Descripción: Background: A central aspect of development and disease is the control of cell proliferation through regulation of the mitotic cycle. Cell cycle progression and directionality requires an appropriate balance of positive and negative regulators whose expression must fluctuate in a coordinated manner. p19INK4d, a member of the INK4 family of CDK inhibitors, has a unique feature that distinguishes it from the remaining INK4 and makes it a likely candidate for contributing to the directionality of the cell cycle. p19INK4d mRNA and protein levels accumulate periodically during the cell cycle under normal conditions, a feature reminiscent of cyclins. Methodology/Principal Findings: In this paper, we demonstrate that p19INK4d is transcriptionally regulated by E2F1 through two response elements present in the p19INK4d promoter. Ablation of this regulation reduced p19 levels and restricted its expression during the cell cycle, reflecting the contribution of a transcriptional effect of E2F1 on p19 periodicity. The induction of p19INK4d is delayed during the cell cycle compared to that of cyclin E, temporally separating the induction of these proliferative and antiproliferative target genes. Specific inhibition of the E2F1-p19INK4d pathway using triplex-forming oligonucleotides that block E2F1 binding on p19 promoter, stimulated cell proliferation and increased the fraction of cells in S phase. Conclusions/Significance: The results described here support a model of normal cell cycle progression in which, following phosphorylation of pRb, free E2F induces cyclin E, among other target genes. Once cyclinE/CDK2 takes over as the cell cycle driving kinase activity, the induction of p19 mediated by E2F1 leads to inhibition of the CDK4,6-containing complexes, bringing the G1 phase to an end. This regulatory mechanism constitutes a new negative feedback loop that terminates the G1 phase proliferative signal, contributing to the proper coordination of the cell cycle and provides an additional mechanism to limit E2F activity. © 2011 Carcagno et al.

Descripción: Functional interaction between the immune and neuroendocrine systems is mediated by humoral mediators, neurotransmitters, and cytokines, including TRH and PRL. We examined the role of neuroendocrine changes, particularly TRH and PRL, during the T cell-dependent immune response. After immunization of rats with sheep red blood cells (SRBC, a T cell-dependent antigen), an increase of hypothalamic TRH messenger RNA (mRNA) was observed at 4-24 h post immunization, in contrast to the decrease observed after treatment with lipopolysaccharide (LPS). During the above period, with SRBC, there was an increase in pituitary TRH receptor mRNA and plasma PRL levels but no changes in TSH and GH. Also, in contrast to the early corticosterone peak induced by LPS, the activation of the hypothalamic-pituitary-adrenocortical suppressive response appears in a late phase, 5-7 days after SRBC. Intracerebroventricular injection of antisense oligonucleotide complementary to rat TRH mRNA in conscious freely-moving rats immunized with SRBC resulted in a significant inhibition of specific antibody production and a concomitant inability to produce the peak in plasma PRL levels. These studies demonstrate, for the first time, that the T cell-dependent immune response is critically dependent on the early activation of TRH and PRL and that the neuroendocrine changes occurring during it are profoundly different from those occurring during the T cell-independent and inflammatory responses (LPS model).

Descripción: We present here new paleointensity and geochronology results from Early Cretaceous volcanic rocks of Sierra Chica de Cordoba (Argentina). The new K-Ar isotopic ages of 5 samples range from 136 to 122 Ma. Twenty five samples from 7 individual flows yielded acceptable paleointensity estimates. The mean paleointensity values per flow are ranging from 53.0±1.9 to 25.4±2.6 μT and the corresponding Virtual Dipole Moments (VDMs) are ranging from 9.3±1.3 to 4.6±0.5 (1022 Am2). This corresponds to the mean value of 7.3±1.7x1022 Am2, which is compatible to the present geomagnetic axial dipole. Currently available selected paleointensity data from 80 to 130 Ma suggest that geomagnetic field strength frequently fluctuated before and during the Cretaceous Normal Superchron while the magnetic polarity maintained stable. The mean paleointensities derived from Cordoba lavas agree remarkably well with those obtained from the Parana Magmatic Province (133-132 Ma). This reinforces the hypothesis about the unreliability of ‘Mesozoic Dipole Low'. © 2006, The Seismological Society of Japan, Society of Geomagnetism and Earth, Planetary and Space Sciences, The Volcanological Society of Japan, The Geodetic Society of Japan, The Japanese Society for Planetary Sciences. All rights reserved.

Descripción: In this article, the performance of hierarchical architectures for computer vision of biological inspiration is analyzed. In particular, the role of the lateral geniculate nucleus (LGN) for the robustness in the recognition of ring shaped patterns under gradual changes in illumination was analyzed. Changes in illumination are common in everyday environments and thus, it is a crucial factor to be considered for the recognition of objects in everyday environments. © 2012 Springer-Verlag.

Descripción: Some of the Biomphalaria species living in Chaco, such as B. straminea and B. tenagophila, are natural transmitters of schistosomiasis in Brazil, while those of the genus Drepanotrema are not intermediate hosts of the disease. The aim of the present work was to analyze the importance of a selected set of environmental variables in explaining patterns of distributions and relative abundance of planorbid gastropod assemblages. The study sites were located in urban areas of Resistencia City, Chaco Province, and the environmental variables measured were substratum (macrophytes), water quality (pH, O2, nutrients, among others), as well as other gastropods (Ancylidae, Hydrobiidae and Ampullaridae). Seasonal samplings were carried out in four distinct environments. Thirty-one quantitative samples of gastropods and environmental variables were obtained. In canonical correspondence analysis (CCA), seven environmental variables were retained after a stepwise forward selection, from a total of 26, including [N-NH4+], O2%, and the macrophytes Eichhornia crassipes, Pistia stratiotes, Panicum elephantipes, Hydrocotyle ranunculoides and Canna glauca. They explained 62% of the variation in planorbid association. Canna glauca was the most significant variable, being positively correlated with all of the species of Drepanotrema. Axis I separates B. tenagophila from B. straminea, along a gradient related to increasing O 2% and P. elephantipes abundance, as well as decreasing [N-NH 4+] and P. stratiotes. Axis II separates D. lucidum, D. anatinum and D. cimex from the other planorbid species along a gradient associated with decreasing abundances of H. ranunculoides and C. glauca. Some common aquatic macrophytes, and to a lesser extent, dissolved oxygen and ammonium in water, may be useful indicators of favorable environmental conditions for potential intermediate hosts of schistosomiasis in Chaco Region.

Descripción: Fil:Petrovich, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: We perform a generalized Scherk-Schwarz dimensional reduction of Double Field Theory on a twisted double torus. The four dimensional effective action is shown to exactly reproduce the bosonic electric sector of gauged N = 4 supergravity. We present explicit expressions for the gaugings in terms of the twists, and analyze the associated string backgrounds. This framework provides a higher dimensional origin of the gaugings in terms of generalized fluxes.

Descripción: In this paper we obtain an effective algorithm for quantifier elimination over algebraically closed fields: For every effective infinite integral domain k, closed under the extraction of pth roots when the characteristic p of k is positive, and every prenex formula φ with r blocks of quantifiers involving s polynomials F1,...,Fs∈k[X1,...,Xn] encoded in dense form, there exists a well-parallelizable algorithm without divisions whose output is a quantifier-free formula equivalent to φ. The sequential complexity of this algorithm is bounded by O(|φ|) - D(O(n))r, where |φ| is the length of φ and D ≥ n is an upper bound for 1 + ∑si-1 deg Fi, and the polynomials in the output are encoded by means of a straight line program. The complexity bound obtained is better than the bounds of the known elimination algorithms, which are of the type |φ|.Dncr, where c ≥ 2 is a constant. This becomes notorious when r = 1 (i.e., when there is only one block of quantifiers): the complexity bounds known up to now are not less than Dn2, while our bound is DO(n). Moreover, in the particular case that there is only one block of existential quantifiers and the input polynomials are given by a straight line program, we construct an elimination algorithm with even better bounds which depend on the length of this straight line program: Given a formula of the type ∃xn-m + 1, . . . , ∃xn: F1(x1, . . . ,Xn) = 0 ∧ ⋯ ∧ Fs(x1, . . . ,Xn) = 0 ∧ G1(x1, . . . , Xn) ≠ 0 ∧ ⋯ ∧ Gs′ (x1, . . . ,xn) ≠ 0, where F1, . . . ,Fs ∈ k[X1, . . . ,Xn] are polynomials whose degrees in the m variables Xn-m+1,. . . ,Xn are bounded by an integer d ≥ m and G1, . . . ,Gs′ ∈ k[X1, . . . ,Xn] are polynomials whose degrees in the same variables are bounded by an integer δ, this algorithm eliminates quantifiers in time L2.(s.s′.δ)O(1).dO(m), where L is the length of the straight line program that encodes F1, . . . ,Fs, G1, . . . ,Gs′. Finally, we construct a fast algorithm to compute the Chow Form of an irreducible projective variety. The construction of all the algorithms mentioned above relies on a preprocessing whose cost exceedes the complexity classes considered (they are based on the construction of correct test sequences). In this sense, our algorithms are non-uniform but may be considered uniform as randomized algorithms (choosing the correct test sequences randomly). © 1998 Elsevier Science B.V. All rights reserved.

Descripción: Fil:Cafure, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: In this paper we present a probabilistic algorithm which computes, from a finite set of polynomials defining an algebraic variety V, the decomposition of V into equidimensional components. If V is defined by s polynomials in n variables of degrees bounded by an integer d ≥ n and V = ∪l=0 r Vℓ is the equidimensional decomposition of V, the algorithm obtains in sequential time bounded by sO(1)dO(n), for each 0 ≤ ℓ ≤r, a set of n + 1 polynomials of degrees bounded by deg(Vℓ) which define Vℓ. © 2002 Elsevier Science B.V. All rights reserved.

Descripción: The effective spectrum of the hard x-ray output of a Mather-type tabletop plasma focus device was determined from attenuation data on metallic samples using commercial radiographic film coupled to a Gd2 O2 S:Tb phosphor intensifier screen. It was found that the radiation has relevant spectral components in the 40-150 keV range, with a single maximum around 60-80 keV. The radiation output allows for 50 ns resolution, good contrast, and introspective imaging of metallic objects even through metallic walls. A numerical estimation of the induced voltage on the focus during the compressional stage is briefly discussed. © 2007 American Institute of Physics.

Descripción: The aim of this work was to study the short and long term influences of ascorbic acid on Hydrochoerus hydrochaeris, if supplemented in their food. No differences regarding food intake were observed in the absence of vitamin C. On a daily basis, animals accustomed to food containing ascorbic acid prefered to continue eating the same food. Food preference in capybaras did not seem to depend on ascorbic acid availability; however, when accustomed to vitamin C, capybaras might recognize and select ascorbic acid in subsequent food. Mechanisms allowing capybaras to "evaluate" the nutritional quality of their food are discussed, as well as the adaptive value of this behavior in free ranging populations. © 2009 Tecpar.

Descripción: A change in bird density within a captive flock of Sicalis flaveola pelzeni (Sclater, 1872) affected the decision to join a group. Ruling out inter-individual differences and maintaining constant the size of a food patch, birds were found to fly more often to the food source and spend a longer time in its environs when kept in greater groups.

Descripción: Fil:Duhau, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Photoactive materials based on dye molecules incorporated into thin films or bulk solids are useful for applications as photosensitization, photocatalysis, solar cell sensitization and fluorescent labeling, among others. In most cases, high concentrations of dyes are desirable to maximize light absorption. Under these circumstances, the proximity of dye molecules leads to the formation of aggregates and statistical traps, which dissipate the excitation energy and lower the population of excited states. The search for enhancement of light collection, avoiding energy wasting requires accounting the photophysical parameters quantitatively, including the determination of quantum yields, complicated by the presence of light scattering when particulate materials are considered. In this work we summarize recent advances on the photophysics of dyes in light-scattering materials, with particular focus on the effect of dye concentration. We show how experimental reflectance, fluorescence and laser-induced optoacoustic spectroscopy data can be used together with theoretical models for the quantitative evaluation of inner filter effects, fluorescence and triplet formation quantum yields and energy transfer efficiencies. © 2013 The American Society of Photobiology.

Descripción: Since apoptosis appeared to be related to neurodegenerative processes, neuroprotection has been involved in investigation of therapeutic approaches focused upon pharmacological agents to prevent neuronal programmed cell death. In this regard, erythropoietin (Epo) seems to play a critical role. The present work was focused on the study of the Epo protective effect upon human neuroblastoma SH-SY5Y cells subjected to differentiation by staurosporine. Under this condition, profuse neurite outgrowth was accompanied by programmed cell death (35% of apoptotic cells by Hoechst assay, showing characteristic DNA ladder pattern). A previous treatment with recombinant human Epo (rHuEpo) increased the expression of the specific receptor for Epo while prevented apoptosis. Simultaneously, morphological changes in neurite elongation and interconnection induced by staurosporine were blocked by Epo. These Epo effects proved to be associated to the induction of Bcl-xL at the mRNA and protein levels (RT-PCR and Western blot after immunoprecipitation) and were mediated by activation of pathways inhibited by wortmannin. In conclusion, the fact that both events induced by staurosporine, cell apoptosis and differentiation, were prevented in SH-SY5Y cells previously exposed to rHuEpo suggests interrelated signaling pathways triggered by the Epo/EpoR interaction. © 2005 Elsevier B.V. All rights reserved.

Descripción: Fil:Gonzalez, N.S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Notonectids are well-known predators in aquatic habitats, where mosquito larvae, chironomids, and cladocerans constitute their main diet. Our purpose was to assess the effect of structural complexity on the predatory ability of Buenoa fuscipennis, a common predator in aquatic habitats of Buenos Aires city (Argentina). Buenoa fuscipennis showed type 2 functional responses in both the presence and absence of prey refuge and no differences in attack rate or handling time between refuge treatments. Regarding mosquito size classes, B. fuscipennis exhibited a significantly higher preference for 2nd instar larvae and no predation on pupae. In the presence of mosquito larvae and alternative prey, B. fuscipennis preferred mosquitoes over chironomid larvae and adult cladocerans over mosquito larvae. No switching behavior was detected in our experiments. Habitat structure only slightly affected the predatoŕs consumption rates on mosquito larvae. Overall, preference for prey did not vary with the presence of refuge, except for the preference for mosquitoes over chironomid larvae, which was significantly decreased in the presence of refuge as a consequence of reduced predation on mosquito larvae. The results suggest that B. fuscipennis could efficiently control mosquitoes in structurally simple habitats where chironomids are the most abundant alternative prey but not in temporary pools where cladocerans are abundant. © 2013 The Society for Vector Ecology.

Descripción: The effect of O2+, H2+ O 2+, and N2+ O2 + ion-beam irradiation of carbon nanotubes (CNTs) films on the chemical and electronic properties of the material is reported. The CNTs were grown by the chemical vapor deposition technique (CVD) on silicon TiN coated substrates previously decorated with Ni particles. The Ni decoration and TiN coating were successively deposited by ion-beam assisted deposition (IBAD) and afterwards the nanotubes were grown. The whole deposition procedure was performed in situ as well as the study of the effect of ion-beam irradiation on the CNTs by x-ray photoelectron spectroscopy (XPS). Raman scattering, field-effect emission gun scanning electron microscopy (FEG-SEM), and field emission (FE) measurements were performed ex situ. The experimental data show that: (a) the presence of either H2+ or N2 + ions in the irradiation beam determines the oxygen concentration remaining in the samples as well as the studied structural characteristics; (b) due to the experimental conditions used in the study, no morphological changes have been observed after irradiation of the CNTs; (c) the FE experiments indicate that the electron emission from the CNTs follows the Fowler-Nordheim model, and it is dependent on the oxygen concentration remaining in the samples; and (d) in association with FE results, the XPS data suggest that the formation of terminal quinone groups decreases the CNTs work function of the material. © 2011 American Institute of Physics.

Descripción: Previous works in a colonized and an original population of Drosophila buzzatii have shown a consistent relationship between the inversion polymorphism and thorax length, a measure of body size. However, the populations studied in those reports share a close genealogical relationship as suggested by several lines of evidence. In the present paper, we revisit this issue by analysing the correlation between second chromosome arrangements and thorax length in two Argentinian natural populations (Termas de Rio Hondo and Arroyo Escobar) from different biogeographic areas with different host plants. Our findings are: (1) inversion frequencies were significantly different between populations; (2) the mean thorax length of flies collected in both populations was not significantly different; and (3) we obtain confirming evidence that flies carrying 2st, the ancestral gene order, have on average a smaller body size than those carrying the derived arrangements (2j and 2jz3). These results suggest that the biometrical effect of inversions on body size previously described are due to genetic differences between arrangements and not to the close historical relationship between the populations studied in previous reports.

Descripción: In this paper we analyze the effect of introducing a numerical integration in the piecewise linear finite element approximation of the Steklov eigenvalue problem. We obtain optimal order error estimates for the eigenfunctions when this numerical integration is used and we prove that, for singular eigenfunctions. the eigenvalues obtained using this reduced integration are better approximations than those obtained using exact integration when the mesh size is small enough.

Descripción: The preference for relative humidity (RH) and suitability of different levels of this environmental parameter were investigated in the haematophagous bug Triatoma brasiliensis Neiva, 1911 (Hemiptera, Reduviidae). The hygropreference of T. brasiliensis was studied using a RH gradient and the effect of different RHs on the egg hatching, nymph mortality and moulting success was also analysed. The results show that egg hatching in first-instar nymphs of T. brasiliensis was lower at extreme RHs and, particularly, it was lowest at 9.3% RH. The survival of starved nymphs was not affected by RH, but the percentage of engorged nymphs and the ecdysis success of these nymphs once fed was diminished strongly by high humidity. Fourth-instar nymphs preferred to stay at the lowest RH during the first 5 days after feeding and during ecdysis. This preference changed markedly during starvation. Fifteen days after ecdysis, the bugs moved towards intermediate humidities, and 30 days after ecdysis they even preferred the most humid sectors of the gradient. Females preferred to lay eggs in dry environments, suggesting that they may not have a particular hygropreference for oviposition, but that they simply lay their eggs at the RHs where they prefer to stay.

Descripción: 1. 1. The porphyrinogenic ability of several antineoplasics used in the therapy of the different cancers was evaluated. The action of cyclophosphamide, busulfan and 5-fluorouracil on the amount and nature of the accumulated hepatic porphyrins and on the activity of δ-aminolaevulinate synthase(ALA-S). were estimated at different doses and times of drug treatment in 17-day-old chick embryos. 2. 2. It was observed that cyclophosphamide produces a significant increase in the accumulation of hepatic porphyrins at different doses as well as in the activity of the ALA-S, at all the incubation times. Cyclophosphamide alters the pattern of porphyrins accumulated in the liver, where a coproporphyrin: protoporphyrin ratio higher than in the controls can be observed. 3. 3. Busulfan increased the hepatic porphyrins accumulated in the liver but to a lesser degree than cyclophosphamide. 4. 4. 5-Fluorouracil did not modify the hepatic porphyrin content when it was administered at doses up to 40 mg/embryo. 5. 5. When the embryos were injected with busulfan or 5-fluorouracil no significant differences were observed in the activity of ALA-S up to 11 hr of incubation. 6. 6. These results indicate that cyclophosphamide has a remarkable porphyrinogenic capacity in chick embryo while busulfan. notwithstancling the fact that it alters the haem pathway, it does so to a degree that does not impair the regulation of ALA-S activity. Fluorouracil seems to be non porphyrinogenic in this system, up to 40 mg/embryo. © 1988.

Descripción: The subfilter-scale (SFS) physics of regularization models are investigated to understand the regularizations' performance as SFS models. Suppression of spectrally local SFS interactions and conservation of small-scale circulation in the Lagrangian-averaged Navier-Stokes α-model (LANS-α) is found to lead to the formation of rigid bodies. These contaminate the superfilter-scale energy spectrum with a scaling that approaches k +1 as the SFS spectra is resolved. The Clark-α and Leray-α models, truncations of LANS-α, do not conserve small-scale circulation and do not develop rigid bodies. LANS-α, however, is closest to Navier-Stokes in intermittency properties. All three models are found to be stable at high Reynolds number. Differences between L 2 and H 1 norm models are clarified. For magnetohydrodynamics (MHD), the presence of the Lorentz force as a source (or sink) for circulation and as a facilitator of both spectrally nonlocal large to small scale interactions as well as local SFS interactions prevents the formation of rigid bodies in Lagrangian-averaged MHD (LAMHD-α). LAMHD-α performs well as a predictor of superfilter-scale energy spectra and of intermittent current sheets at high Reynolds numbers. It may prove generally applicable as a MHD-LES. © 2010 Springer Science+Business Media, LLC.

Descripción: The combined effect of water activity (a(w)) and pH on growth and toxin production by Clostridium botulinum type G strain 89 was investigated. The minimum a(w) at which growth and toxin formation occurred was 0.965, for media in which the pH was adjusted with either sodium chloride or sucrose. The minimum pH (at the optimum a(w)) for growth and toxin production of C. botulinum type G was found to be 5.6. Optimum conditions for toxin activation were a trypsin concentration of 0.1%, a pH of the medium of 6.5, and an incubation for 45 min at 37° C. These data did not show evidence of heat-labile spores, since a heat shock of 75°C for 10 min did not significantly decrease the spore count of strain 89G in media at pH 7.0 or 5.6. It was frequently observed that cells grown at reduced a(w) or pH experienced severe morphological changes.

Descripción: Bioreactor cultures of Escherichia coli recombinants carrying phaBAC and phaP of Azotobacter sp. FA8 grown on glycerol under low-agitation conditions accumulated more poly(3-hydroxybutyrate) (PHB) and ethanol than at high agitation, while in glucose cultures, low agitation led to a decrease in PHB formation. Cells produced smaller amounts of acids from glycerol than from glucose. Glycerol batch cultures stirred at 125 rpm accumulated, in 24 h, 30.1% (wt/wt) PHB with a relative molecular mass of 1.9 MDa, close to that of PHB obtained using glucose. Copyright © 2010, American Society for Microbiology. All Rights Reserved.

Descripción: The pressure exerted by consumers has generally been considered to be among the main factors affecting the structure and processes in marine communities. Here, we assessed the effects of the predatory starfish Heliaster helianthus on substrate colonization by the dominant mussel Semimytilus algosus in a rocky intertidal area of the central Peruvian coast. We conducted 3 experiments: exclusions of starfish (1) from the edge of mussel beds, (2) from areas on bare substrate and (3) from areas surrounding recruitment mediators (i.e. branched macroalgae). The exclusion of H. helianthus resulted in increased cover of S. algosus in the 3 experiments. However, the colonization of the available space by S. algosus in the absence of starfish was more evident when facilitated by recruitment mediators or by migration from the edge of mussel beds than when colonization occurred during succession starting from bare substrate. By the end of the study period, however, increased S. algosus abundance, which coincided with the end of the cold phase (La Niña) of the El Niño-Southern Oscillation, overwhelmed the effects of starfish. We suggest that periodic oceanographic fluctuations are also important in controlling community dynamics in Peruvian rocky intertidal zones, highlighting the variation in the relative importance of top-down versus bottom-up control when different temporal scales are considered. © Inter-Research 2011.

Descripción: 1. The effects of the voltage-dependent calcium channel (VDCC) blockers ω-agatoxin IVA (ω-AgaIVA), ω-conotoxin GVIA (ω-CgTx), ω-conotoxin MVIIC (ω-MVIIC) and ω-conotoxin MVIID (ω-MVIID) were evaluated on transmitter release in the mouse diaphragm preparation. The effects of ω-AgaIVA and ω-MVIIC were also evaluated on the perineurial calcium and calcium-dependent potassium currents, I(ca), and I(K(Ca)), respectively, in the mouse levator auris preparation. 2. The P- and Q-type VDCC blocker ω-AgaIVA (100 nM) and P- Q- and N-type channel blockers ω-MVIIC (1 μM) and ω-MVIID (3 μM) strongly reduced transmitter release (> 80-90% blockade) whereas the selective N-type channel blocker ω-CgTx (5 μM) was ineffective. 3. The process of release was much more sensitive to ω-MVIIC (IC50 = 39 nM) than to ω-MVIID (IC50 = 1.4 μM). After almost completely blocking transmitter release (quantal content ~0.3% of its control value) with 3 μM ω-MVIIC, elevating the external [Ca2+] from 2 to 10 mM induced an increase of ~20 fold on the quantal content of the endplate potential (e.p.p.) (from 0.2 ± 0.04 to 4.8 ± 1.4). 4. Nerve-evoked transmitter release in a low Ca2+-high Mg2+ medium (low release probability, quantal content = 2 ± 0.1) had the same sensitivity to ω-AgaIVA (IC50 = 16.8 nM) as that in normal saline solutions. In addition, K+-evoked transmitter release was also highly sensitive to the action of this toxin (IC50 = 11.5 nM; 100 nM > 95% blockade). The action of ω-AgaIVA on transmitter release could be reversed by toxin washout if the experiments were carried out at 31-33°C. Conversely, the effect of ω-AgaIVA persisted even after two hours of toxin washout at room temperature. 5. Both the calcium and calcium-dependent potassium presynaptic currents, I(ca), and I(K(Ca)), respectively, were highly sensitive to low concentrations (10-30 nM) of ω-AgaIVA. The I(ca), and the I(K(Ca)) were also strongly reduced by 1 μM ω-MVIIC. The most marked difference between the action of these two toxins was the long incubation times required to achieve maximal effects with ω-MVIIC. 6. In summary these results provide more evidence that synaptic transmission at the mammalian neuromuscular junction is mediated by Ca2+ entry through P- and/or Q-type calcium channels.

Descripción: Dimethyl sulfoxide (DMSO) has been known to enhance cell membrane permeability of drugs or DNA. Molecular dynamics (MD) simulations with single-component lipid bilayers predicted the existence of three regimes of action of DMSO: membrane loosening, pore formation and bilayer collapse. We show here that these modes of action are also reproduced in the presence of cholesterol in the bilayer, and we provide a description at the atomic detail of the DMSO-mediated process of pore formation in cholesterol-containing lipid membranes. We also successfully explore the applicability of DMSO to promote plasma membrane permeability to water, calcium ions (Ca2+) and Yo-Pro-1 iodide (Yo-Pro-1) in living cell membranes. The experimental results on cells in culture can be easily explained according to the three expected regimes: in the presence of low doses of DMSO, the membrane of the cells exhibits undulations but no permeability increase can be detected, while at intermediate DMSO concentrations cells are permeabilized to water and calcium but not to larger molecules as Yo-Pro-1. These two behaviors can be associated to the MD-predicted consequences of the effects of the DMSO at low and intermediate DMSO concentrations. At larger DMSO concentrations, permeabilization is larger, as even Yo-Pro-1 can enter the cells as predicted by the DMSO-induced membrane-destructuring effects described in the MD simulations. © 2012 de Ménorval et al.

Descripción: In order to increase the understanding of the interactions which define the planar conformation of the methoxy group with respect to the aryl ring in methyl aryl ethers and the effect these interactions have on the methoxy NMR parameters, 17O and 13C spectra were measured and ab initio optimized geometries were calculated for three different conformations of the methoxy group in 2-methoxy-5-X-pyridines (X = H, NO2, and NH2). 17O and 13C chemical shifts were also calculated using the LORG approach. It was found that, contrary to what has been commonly assumed, the oxygen and the carbon of the methoxy group are deshielded when the electronic resonance interaction is increased. Therefore, the large 13C deshielding effect observed for a conformation with an out-of-plane methoxy group in aryl methyl ethers and related compounds has to be attributed to the inhibition of the attractive van der Waals forces between the methyl moiety and the aromatic ortho-cis carbon atom. © 1993 American Chemical Society.

Descripción: The response of altered sex ratio in southern elephant seals due to environmental stress was analysed. Data were collected at King George Island from 1980 to 1994. Significant retreats in the ice cover during El Niño events strongly suggest environmental stress during this period along the Bellingshausen Sea, a zone where female elephant seals from King George Island feed during their pregnancy. Randomly chosen weaning elephant seal pups (n = 1178) were sexed at Stranger Point (King George Island, 62° 14' S, 58° 30' W) over 5 km of beach from 1985 to 1994. Adult sex ratio was also determined annually from 1980 to 1994 as the ratio between maximum number of bulls and females on land. The theoretical pup sex ratio was assumed as 1:1 according to background information. Adult sex ratio was calculated as 1:6. To define the occurrence of El Niño Southern Oscillation (ENSO) during the study period, a sea surface temperature (SST) index called 'Niño 3.4' for the region 5°N to 5° S, 120° E to 170° W was considered. Monthly SST anomalies were obtained from the Climate Prediction Center (CPC, NOAA). To provide an annual index of anomaly strength (IAS), the monthly adjusted oscillation index climatology (AOIC) was averaged. Accumulated values during the whole study period showed that during El Niño years (1987, 1991, 1992) the proportion of pups was significantly biased in favour of females (p < 0.01). During normal years (1986, 1990, 1993, 1994) and La Niña years (1985, 1988, 1989), accumulative values showed a greater proportion of male pups to females (p < 0.05), Using the 1:1 hypothesis, we found during El Niño years a 9% reduction in the male segment, whereas in non-El Niño years a recovery of 7 % was observed (3 % during normal years and 4 % during La Niña years. To see the influence of accumulative values of pup sex ratio in adult sex ratio, a theoretical adult proportion was calculated as 1:6. To test this hypothesis, information on adult sex ratio taken from King George Island between 1980 and 1994 (n = 14 yr) was analysed. The average adult sex ratio for King George Island was 1:7. This value seems to confirm the hypothesis that this population has had a balanced production of male and female pups in the long term. Comparisons with Pacific and Indian declining seal populations were made.

Descripción: Polyhydroxyalkanoates (PHAs) are accumulated as intracellular granules by many bacteria under unfavorable conditions, enhancing their fitness and stress resistance. Poly(3-hydroxybutyrate) (PHB) is the most widespread and best-known PHA. Apart from the genes that catalyze polymer biosynthesis, natural PHA producers have several genes for proteins involved in granule formation and/or with regulatory functions, such as phasins, that have been shown to affect polymer synthesis. This study evaluates the effect of PhaP, a phasin, on bacterial growth and PHB accumulation from glycerol in bioreactor cultures of recombinant Escherichia coli carrying phaBAC from Azotobacter sp. strain FA8. Cells expressing phaP grew more, and accumulated more PHB, both using glucose and using glycerol as carbon sources. When cultures were grown in a bioreactor using glycerol, PhaP-bearing cells produced more polymer (2.6 times) and more biomass (1.9 times) than did those without the phasin. The effect of this protein on growth promotion and polymer accumulation is expected to be even greater in high-density cultures, such as those used in the industrial production of the polymer. The recombinant strain presented in this work has been successfully used for the production of PHB from glycerol in bioreactor studies, allowing the production of 7.9 g/liter of the polymer in a semisynthetic medium in 48-h batch cultures. The development of bacterial strains that can efficiently use this substrate can help to make the industrial production of PHAs economically feasible. Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Descripción: We have measured the specific heat at constant pressure, Cp, of three different samples of multiwall carbon nanotubes (MWNT). For all samples, Cp departs from a graphitic behavior at T < 120 K. Cp measurements show a temperature threshold from a linear regime for intermediate temperature to a higher-order power law for low temperatures. Moreover, it was found that this crossover only depends on the internal structure of the individual MWNT and not on the spatial order of the MWNT within a bundle. © 2009 IOP Publishing Ltd.

Descripción: Background and Aims: Salix nigra seeds are desiccation-tolerant, as are orthodox seeds, although in contrast to other orthodox seeds they lose viability in a few weeks at room temperature. They also differ in that the chloroplasts of the embryo tissues conserve their chlorophyll and endomembranes. The aim of this paper was to investigate the role of chlorophyll in seed deterioration. Methods: Seeds were aged at different light intensities and atmospheric conditions. Mean germination time and normal and total germination were evaluated. The formation of free radicals was assessed using electronic spin resonance spectroscopy, and changes in the fatty acid composition from phospholipids, galactolipids and triglycerides using gas-liquid chromatography. Membrane integrity was studied with electronic spin resonance spin probe techniques, electrolyte leakage and transmission electron microscopy. Key Results: Light and oxygen played an important role in free-radical generation, causing a decrease in normal germination and an increase in mean germination time. Both indices were associated with a decrease in polyunsaturated fatty acids derived from membrane lipids as phospholipids and galactolipids. The detection of damage in thylakoid membranes and an increase in plasmalemma permeability were consistent with the decrease in both types of lipids. Triglycerides remained unchanged. Light-induced damage began in outermost tissues and spread inwards, decreasing normal germination. Conclusions: Salix nigra seeds were very susceptible to photooxidation. The thylakoid membranes appeared to be the first target of the photooxidative process since there were large decreases in galactolipids and both these lipids and the activated chlorophyll are contiguous in the structure of that membrane. Changes in normal germination and mean germination time could be explained by the deteriorative effects of oxidation. © The Author 2010.

Descripción: The effect of chronic exposure to Escherichia coli on morphometrical parameters, different antioxidant defenses, lipid peroxidation and protein oxidation has been studied in digestive gland of the freshwater mussel Diplodon chilensis in the laboratory during 6 weeks. In, a parallel field study, we evaluated morphometrical and oxidative stress parameters in digestive glands of mussels collected from a sewage polluted area (SMA) and from a pristine area (control). Both sites were characterized by analyzing bacteriological and physic-chemical parameters. In the laboratory D. chilensis was able to filter bacteria at high concentrations with a clearing rate of 0.510 ± 0.036. L/h per gram of dry soft tissue mass. The digestive gland mass to shell length ratio (DGM/SL), reduced glutathione (GSH), lipid peroxidation, as concentration of thiobartituric acid reactive substances (TBARS), and glutathione-S-transferase (GST) activity of mussels fed with bacteria were significantly higher than those of control mussels after the fourth week. Fecal bacteria in lake water samples were undetectable in the control, and higher than 24,000. MPN (most probable number)/100. mL in SMA. DGM/SL was higher in SMA. No differences between sites were observed in total lipid and protein content, neither in superoxide dismutase activity. GSH content was higher in SMA, with no difference in the oxidized form. GST activity and MDA were significantly higher in SMA but protein oxidation was not affected. © 2011 Elsevier GmbH.

Descripción: Insects in general, and Drosophila in particular, are much more capable of surviving anoxia than vertebrates, and the mechanisms involved are of considerable biomedical and ecological interest. Temperature is likely to strongly affect both the rates of damage occurring in anoxia and the recovery processes in normoxia, but as yet there is no information on the effect of this crucial variable on recovery rates from anoxia in any animal. We studied the effects of temperature, and thus indirectly of metabolic flux rates, on survival and recovery times of individual male Drosophila melanogaster following anoxia and O2 reperfusion. Individual flies were reared at 25° and exposed to an anoxic period of 7.5, 25, 42.5 or 60?min at 20, 25 or 30°. Before, during and after anoxic exposure the flies' metabolic rates (MRs), rates of water loss and activity indices were recorded. Temperature strongly affected the MR of the flies, with a Q10 of 2.21. Temperature did not affect the slope of the relationship between time to recovery and duration of anoxic exposure, suggesting that thermal effects on damage and repair rates were similar. However, the intercept of that relationship was significantly lower (i.e. recovery was most rapid) at 25°, which was the rearing temperature. When temperatures during exposure to anoxia and during recovery were switched, recovery times matched those predicted from a model in which the accumulation and clearance of metabolic end-products share a similar dependence on temperature. ©2011. Published by The Company of Biologists Ltd.

Descripción: A systematic study is presented of the effects of trehalose on the physical properties of extruded DPPC-cholesterol unilamellar vesicles. Particular emphasis is placed on examining how the interactions present in the hydrated state translate into those in the dehydrated state. Observations from HSDSC and DSC are used to examine the phase behavior of hydrated and dehydrated vesicles, respectively. The concentration of trehalose inside and outside the vesicles is manipulated, and is shown to affect the relative stability of the membranes. Our results show for the first time that a combination of high inner and low outer trehalose concentration is able to decrease the gel-to-liquid crystalline phase temperature (Tm), while any other combination will not. Upon dehydration, the Tm of all lipid mixtures increases. The extent of the increase depends on the trehalose distribution across the bilayer. The Tm changes in the same direction with trehalose concentration for both freeze-dried and fully hydrated samples, suggesting that the trehalose distribution across the vesicle membrane, as well as the trehalose-phospholipid interaction, is maintained upon lyophilization. The results presented in this work may aid in the formulation of systems to be used in the lyophilization of liposomes for drug delivery applications. © 2006 Elsevier B.V. All rights reserved.

Descripción: The egg capsules, eggs and embryos of the muricid gastropod Coronium coronatum are described for the first time. Capsules are sessile, bulliform, semi-circular, with a plug in the dorsal center. Sutures split the capsule into two asymmetrical halves. Recently laid capsules showed the presence of 3639 (n = 2) uncleaved nurse eggs with a diameter of 180-210 μm (mean = 197.4 ± 8.9). The number of early embryos was 9-11. The size of the embryos was 320 × 320 to 820-880 μm. Nine pre-hatching embryos of 3.94 mm (n = 8, SD = 0.32) were found inside the older capsule. SEM illustrations of embryos and radulae are provided. Comparison of shell and radula of embryos with the protoconch and radulae of adults of C. coronatum revealed that the capsule belongs to this species. © The Author 2007. Published by Oxford University Press on behalf of The Malacological Society of London, all rights reserved.

Descripción: We derive oscillation and nonoscillation criteria for the one-dimensional p-Laplacian in terms of an eigenvalue inequality for a mixed problem. We generalize the results obtained in the linear case by Nehari and Willett, and the proof is based on a Picone-type identity.

Descripción: Possible effects of the break-up channel on the elastic scattering threshold anomaly has been investigated. We used the weakly bound 6,7Li nuclei, which is known to undergo break-up, as projectiles in order to study the elastic scattering on a 27Al target. In this contribution we present preliminary results of these experiments, which were analyzed in terms of the Optical Model and compared with other elastic scattering data using weakly bound nuclei as projectile. © 2007 American Institute of Physics.

Descripción: In this work a small plasma jet is generated applying an ac high voltage (kV) of low frequency (50 Hz) between two disk-shaped electrodes with a hole in the center and separated by a centrally perforated dielectric material. A plasma jet emerges from the electrode system to the room air when a large air flow rate is passing through the holes, for inter-electrode voltage drops around 1 ÷ 3 kV. The electrical characteristics of the discharge, voltage and current were studied varying the applied voltage amplitude and the gas flow rate. It was found that the microplasma jet was stable during a long period of time and the gas temperature remained almost at room temperature. These characteristics make this discharge suitable for biological applications.

Descripción: The set of 1:1 and 2:1 complexes of XOOX′ (X, X′ H, CH 3) with lithium cation has been studied to determine if they are suitable candidates for chiral discrimination in an isotropic medium via nuclear magnetic resonance spectroscopy. Conventional nuclear magnetic resonance is unable to distinguish between enantiomers in the absence of a chiral solvent. The criterion for experimental detection is valuated by the isotropic part of nuclear shielding polarisability tensors, related to a pseudoscalar of opposite sign for two enantiomers. The study includes calculations at coupled Hartree-Fock and density functional theory schemes for 17O nucleus in each compound. Additional calculations for 1H are also included for some compounds. A huge static homogeneous electric field, perpendicular to the magnetic field of the spectromer, as big as ≈1.7 108 V m -1 should be applied to observe a shift of ≈1 ppm for 17O magnetic shielding in the proposed set of complexes. © 2011 American Institute of Physics.

Descripción: We study the effect of translational-rotational hydrodynamic coupling on the transient electric linear dichroism of DNA fragments in aqueous solution. As opposed to previous theoretical works, where analytic solutions valid in the limit of low electric field were reported, we present here a numerical approach which allows to obtain numerical results valid independently from the applied electric field strength. Numerical procedures here used are an extension to the transient-state of those developed in a previous work for the study of the problem in the steady-state. The molecular orientational processes induced by an electric field is characterized with statistical arguments solving the Fokker-Planck equation by means of the finite difference method to know the orientational distribution function of molecules. © 2013 American Institute of Physics.

Descripción: Computational procedures, based on (i) the Ramsey common origin approach and (ii) the continuous transformation of the origin of the quantum mechanical current density-diamagnetic zero (CTOCD-DZ), were applied at the Hartree-Fock level to determine electric quadrupole polarizabilities of nuclear magnetic shielding for molecules in the presence of a nonuniform electric field with a uniform gradient. The quadrupole polarizabilities depend on the origin of the coordinate system, but values of the magnetic field induced at a reference nucleus, determined via the CTOCD-DZ approach, are origin independent for any calculations relying on the algebraic approximation, irrespective of size and quality of the (gaugeless) basis set employed. On the other hand, theoretical estimates of the induced magnetic field obtained by single-origin methods are translationally invariant only in the limit of complete basis sets. Calculations of electric quadrupole polarizabilities of nuclear magnetic shielding are reported for H2, HF, H2 O, N H3, and C H4 molecules. © 2008 American Institute of Physics.

Descripción: Fil:Gnavi, G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: This work studies the partitioning of the electron density into two contributions which are interpreted as the paired and the effectively unpaired electron densities. The topological features of each density field as well as of the total density are described localizing the corresponding critical points in simple selected molecules (local formalism). The results show that unpaired electron-density concentrations occur out of the topological bonding regions whereas the paired electron densities present accumulations inside those regions. A comparison of these results with those arising from population analysis techniques (nonlocal or integrated formalisms) is reported. © 2005 American Institute of Physics.

Descripción: We study the dependence of the magnetic properties of NiPd and CoPd segregated nanoclusters and slabs as a function of the 3d magnetic component concentration (x), the chemical order, and size. In the case of clusters we consider 3d cores coated by Pd atoms (3d/Pd) and also onion-like (Pd/3d/Pd) configurations. For the slabs we consider different possible segregated structures of the 3d and 4d atoms and study the evolution of the magnetic properties on these different configurations. We show that Pd coating gives rise to an enhancement of the average magnetic moment of the Ni or Co core atoms and of the Pd atoms as well. Larger values of the average magnetic moments are obtained in the onion-like structures (Pd/3d/Pd) than in the core/shell (3d/Pd) configuration. We compare with theoretical and experimental results available in the literature.

Descripción: Fil:Aliaga, J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Fil:Guevara, J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: We perform an analysis of the electroweak precision observables in the Lee-Wick Standard Model. The most stringent restrictions come from the S and T parameters that receive important tree level and one loop contributions. In general the model predicts a large positive S and a negative T. To reproduce the electroweak data, if all the Lee-Wick masses are of the same order, the Lee-Wick scale is of order 5 TeV. We show that it is possible to find some regions in the parameter space with a fermionic state as light as 2.4-3.5 TeV, at the price of rising all the other masses to be larger than 5-8 TeV. To obtain a light Higgs with such heavy resonances a fine-tuning of order a few per cent, at least, is needed. We also propose a simple extension of the model including a fourth generation of Standard Model fermions with their Lee-Wick partners. We show that in this case it is possible to pass the electroweak constraints with Lee-Wick fermionic masses of order 0.4-1.5 TeV and Lee-Wick gauge masses of order 3 TeV.

Descripción: An analysis of the abundances of the helium-weak CP stars HD 19400, HD 34797 and HD 35456, is presented using ATLAS9 model atmospheres and observational material taken with a REOSC echelle spectrograph attached to the Jorge Sahade 2.15 m telescope at CASLEO. The light elements are deficient except silicon which is overabundant in HD 19400 and HD 34797. The iron peak elements are all overabundant by factors between 5 and 60. The heavy elements show an overabundance in the three stars studied.

Descripción: An analysis of the abundances of the Silicon star HD 206653 is presented using an ATLAS9 model atmosphere and observational material taken with a REOSC echelle spectrograph attached to the Jorge Sahade 2.15 m telescope at CASLEO. The light elements are solar or deficient except silicon which is overabundant by a factor of 5. The iron peak elements are all overabundant by factors between 10 and 50. Sr and Y are around 1000 times the solar values. Among the Rare Earths only Ce and Eu are identified; both are overabundant by large factors.

Descripción: In 1853 Sylvester stated and proved an elegant formula that expresses the polynomial subresultants in terms of the roots of the input polynomials. Sylvester's formula was also recently proved by Lascoux and Pragacz using multi-Schur functions and divided differences. In this paper, we provide an elementary proof that uses only basic properties of matrix multiplication and Vandermonde determinants. © 2006 Elsevier Ltd. All rights reserved.

Descripción: The effect of eliminating D-lactate synthesis in poly(3-hydroxybutyrate) (PHB)-accumulating recombinant Escherichia coli (K24K) was analyzed using glycerol as a substrate. K24KL, an ldhA derivative, produced more biomass and had altered carbon partitioning among the metabolic products, probably due to the increased availability of carbon precursors and reducing power. This resulted in a significant increase of PHB and ethanol synthesis and a decrease in acetate production. Cofactor measurements revealed that cultures of K24K and K24KL had a high intracellular NADPH content and that the NADPH/NADP+ ratio was higher than the NADH/NAD+ ratio. The ldhA mutation affected cofactor distribution, resulting in a more reduced intracellular state, mainly due to a further increase in NADPH/NADP+. In 60-h fed-batch cultures, K24KL reached 41.9 g · liter-1 biomass and accumulated PHB up to 63% ± 1% (wt/wt), with a PHB yield on glycerol of 0.41 ± 0.03 g · g-1, the highest reported using this substrate. © 2010, American Society for Microbiology.

Descripción: New formulae are given for Chow forms, discriminants and resultants arising from (not necessarily normal) toric varieties of codimension 2. The Newton polygon of the discriminant is determined exactly. © 2002 Elsevier Science Ltd. All rights reserved.

Descripción: In this paper we consider the elliptic system Δ u = a (x) up vq, Δ v = b (x) ur vs in Ω, a smooth bounded domain, with boundary conditions frac(∂ u, ∂ ν) = λ u, frac(∂ v, ∂ ν) = μ v on ∂Ω. Here λ and μ are regarded as parameters and p, s > 1, q, r > 0 verify (p - 1) (s - 1) > q r. We consider the case where a (x) ≥ 0 in Ω and a (x) is allowed to vanish in an interior subdomain Ω0, while b (x) > 0 in over(Ω, -). Our main results include existence of nonnegative nontrivial solutions in the range 0 < λ < λ1 ≤ ∞, μ > 0, where λ1 is characterized by means of an eigenvalue problem, and the uniqueness of such solutions. We also study their asymptotic behavior in all possible cases: as both λ, μ → 0, as λ → λ1 < ∞ for fixed μ (respectively μ → ∞ for fixed λ) and when both λ, μ → ∞ in case λ1 = ∞. © 2009 Elsevier Inc. All rights reserved.

Descripción: Fil:Carminatti, H. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: In recent analyses of numerical simulation and solar wind dataset, the idea that the magnetic discontinuities may be related to intermittent structures that appear spontaneously in MHD turbulence has been explored in details. These studies are consistent with the hypothesis that discontinuity events founds in the solar wind might be of local origin as well, i.e. a by-product of the turbulent evolution of magnetic fluctuations. Using simulations of 2D MHD turbulence, we are exploring a possible link between tangential discontinuities and magnetic reconnection. The goal is to develop numerical algorithms that may be useful for solar wind applications. © 2011 International Astronomical Union.

Descripción: This paper shows the connection between three previously observed but seemingly unrelated phenomena in hydrodynamic (HD) and magnetohydrodynamic (MHD) turbulent flows, involving the emergence of fluctuations occurring on very long time scales: the low-frequency 1/f noise in the power frequency spectrum, the delayed ergodicity of complex valued amplitude fluctuations in wave number space, and the spontaneous flippings or reversals of large-scale fields. Direct numerical simulations of ideal MHD and HD are employed in three space dimensions, at low resolution, for long periods of time, and with high accuracy to study several cases: different geometries, presence of rotation and/or a uniform magnetic field, and different values of the associated conserved global quantities. It is conjectured that the origin of all these long-time phenomena is rooted in the interaction of the longest wavelength fluctuations available to the system, with fluctuations at much smaller scales. The strength of this nonlocal interaction is controlled either by the existence of conserved global quantities with a back-transfer in Fourier space or by the presence of a slow manifold in the dynamics. © 2011 American Physical Society.

Descripción: The addition of Grignard reagents to aldehydes in the presence of chiral aminoal-cohols shows a moderate enantioselectivity. The study carried out with a series of ligands allows the correlation between the structural characteristics and their reactivity.

Descripción: This work describes simple decompositions of the energy of molecular systems according to schemes that partition the three-dimensional space. The components of those decompositions depend on one and two atomic domains thus providing a meaningful chemical information about the nature of different bondings among the atoms which compose the system. Our algorithms can be applied at any level of theory (correlated or uncorrelated wave functions). The results reported here, obtained at the Hartree-Fock level in selected molecules, show a good agreement with the chemical picture of molecules and require a low computational cost in comparison with other previously reported decompositions.

Descripción: This article is a continuation of our previous paper on schemes of energy decompositions of molecular systems in the real space [D. R. Alcoba, J. Chem. Phys. 122, 074102 (2005)] now using correlated state functions. We study, according to physical arguments, the appropriate management of the density cumulant arising from the second-order reduced density matrix at correlated level, whose contributions can be assigned to one-center or to two-center terms in the energy partitioning. Our treatments are applied within two physical space partitioning schemes: the Bader partitioning into atomic basins and the fuzzy atom procedure. The results obtained in selected molecules are analyzed and discussed in detail. © 2007 American Institute of Physics.

Descripción: Fil:Aliaga, J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: The theory of dynamic frames is a promising approach to handle the so-called framing problem, that is, giving a precise characterizations of the locations in the heap that a procedure may modify. In this paper, we show that the machinery used for dynamic frames may be exploited even further. In particular, we use it to check that implementations of abstract data types maintain certain structural invariants that are very hard to express with usual means, including being acyclic (like non-circular linked lists and trees) and having a unique path between nodes (like in a tree). The idea is that regions in this formalism over-approximate the set of reachable objects. We can then maintain this structural invariants by including special preconditions in assignments, of the kind that can be verified by state-of-the-art SMT-based tools. To test this approach we modified the verifier for the Dafny programming language in a suitable way and were able to enforce these invariants in non-trivial examples. © 2011 Springer-Verlag.

Descripción: Ethylene inhibits the establishment of symbiosis between rhizobia and legumes. Several rhizobia species express the enzyme ACC deaminase, which degrades the ethylene precursor 1-cyclopropane-1-carboxilate (ACC), leading to reductions in the amount of ethylene evolved by the plant. M. loti has a gene encoding ACC deaminase, but this gene is under the activity of the NifA-RpoN- dependent promoter; thus, it is only expressed inside the nodule. The M. loti structural gene ACC deaminase (acdS) was integrated into the M. loti chromosome under a constitutive promoter activity. The resulting strain induced the formation of a higher number of nodules and was more competitive than the wild-type strain on Lotus japonicus and L. tenuis. These results suggest that the introduction of the ACC deaminase activity within M. loti in a constitutive way could be a novel strategy to increase nodulation competitiveness of the bacteria, which could be useful for the forage inoculants industry.

Descripción: To characterize the mechanism of chloroplast fructose‐1,6‐bisphosphatase activation, we have examined kinetic and structural changes elicited by protein perturbants and reductants. At variance with its well‐known capacity for enzyme inactivation, 150 mM sodium trichloroacetate yielded an activatable chloroplast fructose‐1,6‐bisphosphatase in the presence of 1.0 mM fructose 1,6‐bisphosphate and 0.1 mM Ca2+. Other sugar bisphosphates did not replace fructose 1,6‐bisphosphate whereas Mg2+ and Mn2+ were functional in place of Ca2+. Variations of the emission fluorescence of intrinsic fluorophores and a noncovalently bound extrinsic probe [2‐(P‐toluidinyl)naphthalene‐6‐sulfonate] indicated the presence of conformations different from the native form. A similar conclusion was drawn from the analysis of absorption spectra by means of fourth‐derivative spectrophotometry. The effect of these conformational changes on the reductive process was studied by subsequently incubating the enzyme with dithiothreitol. The reaction of chloroplast fructose‐1,6‐bisphosphatase with dithiothreitol was accelerated 13‐fold by the chaotropic anion: second‐order rate constants were 48.1 M−1· min−1 and 3.7 M−1· min−1 in the presence and in the absence of trichloroacetate, respectively. Thus, the enhancement of the reductive activation by compounds devoid of redox activity illustrated that the modification of intramolecular noncovalent interactions of chloroplast fructose‐1,6‐bisphosphatase plays an essential role in the conversion of enzyme disulfide bonds to sulfhydryl groups. In consequence, a conformational change would operate concertedly with the reduction of disulfide bridges in the light‐dependent activation mediated by the ferredoxin–thioredoxin system. Copyright © 1994, Wiley Blackwell. All rights reserved

Descripción: We study the extension of holomorphic functions of bounded type defined on an open subset of a Banach space to larger domains. For this, we first characterize the envelope of holomorphy of a Riemann domain over a Banach space, with respect to the algebra of bounded type holomorphic functions, in terms of the spectrum of the algebra. We then give a simple description of the envelopes of balanced open sets and relate the concepts of domain of holomorphy and polynomial convexity. We show that for bounded balanced sets, extensions to the envelope are always of bounded type, and that this does not necessarily hold for unbounded sets, answering a question posed by Hirschowitz in 1972. We also consider extensions to open subsets of the bidual, present some Banach-Stone type results and show some properties of the spectrum when the domain is the unit ball of ℓ p. © 2011 Elsevier Inc.

Descripción: An environmental magnetic study of mainly fluvial "postpampean sediments" assigned to the Lujan Formation (Luján, Buenos Aires Province, Argentina) was carried out. The results obtained suggest a depletion of detrital ferromagnetic minerals during the pedogenetic processes. A characteristic magnetic signal can be distinguished in Holocene paleosols and soils of both eolian and fluvial "post-Pampean sediments" (Fm. Luján and Fm. La Postrera . This signal is analogous to that determined in loessic Pampean sediments assigned to the Buenos Aires Formation. It is inferred that the depletion of detrital ferromagnetic minerals is a general process in the Chacopampean area. This process may be associated with the genesis of a superparamagnetic fraction (SP), which could indicate dry periods during the climatic event. The depletion could also be associated with the genesis of a high coercitivy fraction, analogous with those determined in paleosols in the Pampean loess.

Descripción: 1. 1. A patient with chronic lead intoxication was treated with only one course of highly purified human blood aminolaevulinate dehydratase entrapped in autologous erythrocyte ghosts given intravenously. 2. 2. No untoward effects were observed during or after infusion. 3. 3. An immediate increase in the patient's erythrocyte dehydratase activity was detected 1 hr after enzyme administration, reaching its maximum and nearly normal level 2 days later, values remained unchanged for a week, to slowly diminish after 2 weeks of initiated the treatment, and finally recovered activity was kept practically leveled off for weeks. 4. 4. This novel therapeutic trial produced complete improvement both clinical and biochemical, showing that enzyme infusion has been beneficial and can be safely and successfully used in the treatment of human lead intoxication. © 1983.

Descripción: Epsins are endocytic proteins with a structured epsin N-terminal homology (ENTH) domain that binds phosphoinositides and a poorly structured C-terminal region that interacts with ubiquitin and endocytic machinery, including clathrin and endocytic scaffolding proteins. Yeast has two redundant genes encoding epsins, ENT1 and ENT2; deleting both genes is lethal. We demonstrate that the ENTH domain is both necessary and sufficient for viability of ent1Δent2Δ cells. Mutational analysis of the ENTH domain revealed a surface patch that is essential for viability and that binds guanine nucleotide triphosphatase-activating proteins for Cdc42, a critical regulator of cell polarity in all eukaryotes. Furthermore, the epsins contribute to regulation of specific Cdc42 signaling pathways in yeast cells. These data support a model in which the epsins function as spatial and temporal coordinators of endocytosis and cell polarity. © 2006 by The National Academy of Sciences of the USA.

Descripción: It will be proven that if a gauge-invariant Lagrangian density having the local form L = L(gij;Ai;Aij) is such that its Euler-Lagrange equations Ei(L) = 0 have the same set of solutions as Ei(L0) = 0, where L0 = g1/2F ijFij, then L and cL0 are equivalent for same constant c, i.e., Ei(L) = Ei(cL0). From a previous result it follows that L = cL0 + D + eg1/2, where D is a divergence and e is a constant. © 1991 American Institute of Physics.

Descripción: In affirmative, the equivariant inverse problem for Maxwell-type Euler-Lagrange expressions is solved. This allows the proof of the uniqueness of the Maxwell equations. © 1987 American Institute of Physics.

Descripción: Fil:Bochicchio, R.C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Fil:Clemente, M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Fil:Pagola, G.I. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: In this paper we prove error estimates for a piecewise Q1 average interpolation on anisotropic rectangular elements, i.e., rectangles with sides of different orders, in two and three dimensions. Our error estimates are valid under the condition that neighboring elements have comparable size. This is a very mild assumption that includes more general meshes than those allowed in previous papers. In particular, strong anisotropic meshes arising naturally in the approximation of problems with boundary layers fall under our hypotheses. Moreover, we generalize the error estimates allowing on the right-hand side some weighted Sobolev norms. This extension is of interest in singularly perturbed problems. Finally, we consider the approximation of functions vanishing on the boundary by finite element functions with the same property, a point that was not considered in previous papers on average interpolations for anisotropic elements. As an application we consider the approximation of a singularly perturbed reaction-diffusion equation and show that, as a consequence of our results, almost optimal order error estimates in the energy norm, valid uniformly in the perturbation parameter, can be obtained. © 2005 American Mathematical Society.

Descripción: The Peteroa volcano, located in the SouthernVolcanic Zone of the Andes at 35°15'S latitude, erupted for about 48 days, beginning on September 4th, 2010. After a period of increased fumarole activity, the eruption began with a strong eruption column of ca. 1,800 m in height, to continue later with a weak column of 200 meters. Particulate emitted material contains mainly glass shards and glass fragments with subordinate crystaloclasts. The tephra fallout was mainly accumulated in the vicinity of the volcano, while in more remote areas formed only a thin layer. Due to the low volume of ejected tephra and limited volcanic ash spread, and the fact that the vicinity o the volcano was uninhabited, the eruption of 2010 did not have much effect on people.

Descripción: In this paper we introduce the generalized eigenvalues of a quasilinear elliptic system of resonant type. We prove the existence of infinitely many continuous eigencurves, which are obtained by variational methods. For the one-dimensional problem, we obtain an hyperbolic type function defining a region which contains all the generalized eigenvalues (variational or not), and the proof is based on a suitable generalization of Lyapunov's inequality for systems of ordinary differential equations. We also obtain a family of curves bounding by above the kth variational eigencurve. © 2006 Elsevier Inc. All rights reserved.

Descripción: The inability to monitor wetland drag coefficients at a regional scale is rooted in the difficulty to determine vegetation structure from remote sensing data. Based on the fact that the backscattering coefficient is sensitive to marsh vegetation structure, this paper presents a methodology to estimate the drag coefficient from a combination of SAR images, interaction models and ancillary data. We use as test case a severe fire event occurred in the Paraná River Delta (Argentina) at the beginning of 2008, when 10% of the herbaceous vegetation was burned up. A map of the reduction of the wetland drag coefficient is presented. © 2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.

Descripción: This paper presents new evidence on rupestrian art from a rock shelter in the Puna of Jujuy, attributed to Early/Middle Holocene hunter-gatherers. Figurative rather than abstract-geometric, these paintings differ from those found in the area so far. The physicochemical analysis of the paint on rock walls, pigments from different occupational levels, and red pigments found on a stone pestle, allow us to reconstruct how pigments were made both identifying the raw materials used and the way they were selected. Finally, we discuss the spatial and chronological implications with reference to the distribution of geometric and figurative paintings in the Puna.

Descripción: Aims: Analysis of the physiology and metabolism of Escherichia coli arcA and creC mutants expressing a bifunctional alcohol-acetaldehyde dehydrogenase from Leuconostoc mesenteroides growing on glycerol under oxygen-restricted conditions. The effect of an ldhA mutation and different growth medium modifications was also assessed. Methods and Results: Expression of adhE in E. coli CT1061 [arcA creC(Con)] resulted in a 1·4-fold enhancement in ethanol synthesis. Significant amounts of lactate were produced during micro-oxic cultures and strain CT1061LE, in which fermentative lactate dehydrogenase was deleted, produced up to 6·5 ± 0·3 g l-1 ethanol in 48 h. Escherichia coli CT1061LE derivatives resistant to >25 g l-1 ethanol were obtained by metabolic evolution. Pyruvate and acetaldehyde addition significantly increased both biomass and ethanol concentrations, probably by overcoming acetyl-coenzyme A (CoA) shortage. Yeast extract also promoted growth and ethanol synthesis, and this positive effect was mainly attributable to its vitamin content. Two-stage bioreactor cultures were conducted in a minimal medium containing 100 μg l-1 calcium d-pantothenate to evaluate oxic acetyl-CoA synthesis followed by a switch into fermentative conditions. Ethanol reached 15·4 ± 0·9 g l-1 with a volumetric productivity of 0·34 ± 0·02 g l-1 h-1. Conclusions: Escherichia coli responded to adhE over-expression by funnelling carbon and reducing equivalents into a highly reduced metabolite, ethanol. Acetyl-CoA played a key role in micro-oxic ethanol synthesis and growth. Significance and Impact of the Study: Insight into the micro-oxic metabolism of E. coli growing on glycerol is essential for the development of efficient industrial processes for reduced biochemicals production from this substrate, with special relevance to biofuels synthesis. © 2010 The Society for Applied Microbiology.

Descripción: The effect of Ca2+ (and Mg2+) and the disodium salt of ethylenediaminetetraacetic acid (EDTA), a well known Ca2+ (and Mg2+) chelating agent, on the volatilization/ionization of carbohydrates by using electrospray ionization mass spectrometry has been studied. Model compounds such as maltoses (maltose to maltoheptaose), β-cyclodextrins (β-cyclodextrin, methyl-β-cyclodextrin, heptakis(2,6-di-O-methyl)-β-cyclodextrin, heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin, and 2-hydroxypropyl-β-cyclodextrin) and fructans (sucrose, 1-ketose, nystose, and 1F-fructofuranosylnystose) were used. © 2010.

Descripción: A method is devised for estimating the two-time correlation function and the associated Eulerian decorrelation timescale in turbulence.With the assumptions of a single decorrelation time and a frozen-in flow approximation for the single-point analysis, the method compares two-point correlation measurements with single-point correlation measurements at the corresponding spatial lag. This method is applied to interplanetarymagnetic fieldmeasurements from the Advanced Composition Explorer and Wind spacecraft. An average Eulerian decorrelation time of 2.9 hr is found. This measures the total rate of distortion of turbulent fluid elements-including sweeping, nonlinear distortion, and wave propagation. © 2010. The American Astronomical Society. All rights reserved.

Descripción: The European Starling (Stumus vulgaris) was introduced in Argentina by 1987. Starlings are secondary cavity nesters and may constitute a threat to other cavity nesters. We estimated the density of starlings in Buenos Aires city urban parks and examined the relationships between some habitat characteristics and the presence and abundance of starlings. We also evaluated the interactions between starlings and native species, by observations during foraging and nesting. Because starlings may use Rufous Hornero (Fumarius rufus) dome-shaped nests, we also located and observed them. Starlings were recorded in 293 transects distributed in 20.8 km2 corresponding to 103 Buenos Aires public-access parks, in which 447 individuals were recorded. We found that the relative population density for starlings in parks of Buenos Aires (individuals/ha ± SD) was 2.21 ± 0.09. Starling presence was positively associated with the park area and number of palms and negatively with the number of trees. A positive significant association between starling density and number of tipu trees was also found. Neither the presence nor the abundance of starlings was associated with the park's avian species richness. Although starlings were found to feed in heterospecrfic flocks in 60.3% of the 58 observations (totally 464 min), only five interspecific interactions were recorded (the starling being always the losing species). Twenty-one starling nests were built in natural cavities and nine in cavities made by woodpeckers (Colaptes spp). None of the 26 Rufous Hornero nests found was occupied by starlings. However, the nestling cycle of the Golden-breasted Woodpecker (Colaptes melanolaimus) was recorded to be interrupted in three occasions due either to aggressive interactions or to the presence of starlings near the nests. These findings can be relevant in relation with the need of any action against starlings in Argentina. Accepted 21 September 2010. © The Neotropical Ornithological Society.

Descripción: In contrast to the wide spectrum of cytochrome P450 monooxygenases, there are only 2 heme-based dioxygenases in humans: tryptophan dioxygenase (hTDO) and indoleamine 2,3-dioxygenase (hIDO). hTDO and hIDO catalyze the same oxidative ring cleavage reaction of L-tryptophan to N-formyl kynurenine, the initial and rate-limiting step of the kynurenine pathway. Despite immense interest, the mechanism by which the 2 enzymes execute the dioxygenase reaction remains elusive. Here, we report experimental evidence for a key ferryl intermediate of hIDO that supports a mechanism in which the 2 atoms of dioxygen are inserted into the substrate via a consecutive 2-step reaction. This finding introduces a paradigm shift in our understanding of the heme-based dioxygenase chemistry, which was previously believed to proceed via simultaneous incorporation of both atoms of dioxygen into the substrate. The ferryl intermediate is not observable during the hTDO reaction, highlighting the structural differences between the 2 dioxygenases, as well as the importance of stereoelectronic factors in modulating the reactions.

Descripción: This study was aimed at testing the hypothesis that different forms of fibronectin (FN), produced as a consequence of the alternative splicing of the precursor messenger RNA, play specific roles during development of the ovarian follicle. In particular, we were interested in determining the effect of the ED-I (also termed ED-A) type III repeat, which is absent in the plasma form. Analysis of FN levels in follicular fluids corresponding to different stages of development of bovine follicles revealed marked changes in the concentrations of ED-I + FN, whereas total FN levels remained relatively constant. ED-I + FN levels were higher in small follicles, corresponding to the phase of granulosa cell proliferation. The hypothesis of a physiological role for ED-I + FN was further supported by the finding of a regulation of the alternative splicing of FN in primary cultures of bovine granulosa cells by factors known to control ovarian follicular development. cAMP produced a 10-fold decrease in the relative proportion of the ED-I region. In contrast, transforming growth factor-β elicited a 2-fold stimulation of overall FN synthesis and a 4-fold increase in the synthesis of ED-I containing FN. This effect was evident at the protein (Western blots) and messenger RNA (Northern blots) levels. Although a negative correlation (P < 0.001) was detected between ED-I + FN and estradiol levels in follicular fluid, this steroid was unable to modulate in vitro the alternative splicing of FN. A possible mitogenic effect of ED-I + FN was suggested by the observation that a recombinant peptide corresponding to the ED-I domain stimulated DNA synthesis in a bovine granulosa cell line (BGC-1), whereas a peptide corresponding to the flanking type III sequences had no effect. The hypothesis of ED-I + FN as a growth regulatory factor was further strengthened by the fact that depletion of FN from BGC-1-conditioned medium, which contained ED-I + FN, abrogated its mitogenic activity, whereas plasma FN was without effect. We propose that changes in the primary structure of FN may mediate some of the effects of gonadotropin and intraovarian factors during follicular development.

Descripción: Rapid, ligand-dependent movement of glucocorticoid receptors (GR) from cytoplasm to the nucleus is hsp90-dependent, and much of the movement system has been defined. GR-hsp90 heterocomplexes isolated from cells contain one of several hsp90-binding immunophilins that link the complex to cytoplasmic dynein, a molecular motor that processes along microtubular tracks to the nucleus. The immunophilins link to dynein indirectly via the dynamitin component of the dynein-associated dynactin complex (Galigniana, M. D., Harrell, J. M., O'Hagen, H. M., Ljungman, M., and Pratt, W. B. (2004) J. Biol. Chem. 279, 22483-22489). Although it is known that rapid, hsp90-dependent GR movement requires intact microtubules, it has not been shown that the movement is dynein-dependent. Here, we show that overexpression of dynamitin, which blocks movement by dissociating the dynein motor from its cargo, inhibits ligand-dependent movement of the GR to the nucleus. We show that native GR·hsp90·immnunophilin complexes contain dynamitin as well as dynein and that GR heterocomplexes isolated from cytosol containing paclitaxel and GTP to stabilize microtubules also contain tubulin. The complete movement system, including the dynein motor complex and tubulin, can be assembled under cell-free conditions by incubating GR immune pellets with paclitaxel/GTP-stabilized cytosol prepared from GR - L cells. This is the first evidence that the movement of a steroid receptor is dynein-dependent, and it is the first isolation of a steroid receptor bound to the entire system that determines its retrograde movement.

Descripción: The formation of coherent structures in turbulence is a signature of a developing cascade and therefore might be observable by analyzing inner heliospheric solar wind turbulence. To test this idea, data from the Helios 2 mission, for six streams of solar wind at different heliocentric distances and of different velocities, were subjected to statistical analysis using the partial variance of increments (PVI) approach. We see a clear increase of the PVI distribution function versus solar wind age for higher PVI cutoff, indicating development of non-Gaussian coherent structures. The plausibility of this interpretation is confirmed by a similar behavior observed in two-dimensional magnetohydrodynamics simulation data at corresponding dimensionless nonlinear times. © 2012. The American Astronomical Society. All rights reserved.

Descripción: Geochemical features and neomorphism of Chachao Formation calcareous rocks (Valanginian)-Malargüe Anticline, Mendoza. The Lower Cretaceous Chachao Formation in the Malargüe anticline area consists of wackestone, packstone, grainstone and minor mudstone rich in benthic fauna (mainly bivalves) which were deposited in a shallow carbonate ramp as previous sedimentological studies have proposed. Standard petrographic, XRD, SEM, cathodoluminiscense and trace element determinations composition of micrite and microsparite mosaic crystals were undetaken in order to characterize their original mineralogy. The SEM shows that the mud fraction is composed of a mosaic texture of subhedral to anhedral micrite and microsparite crystals, both showing similar features such as smooth (unpitted) surfaces and lack of aragonite relicts. Crystal morphology also rules out the possible presence of aragonite. These features together with the microfabric, low Sr content (average: 592 ppm) of both micrite and microsparite point to an original high-magnesium calcite composition of the muds. Geochemical data from the micrite and microsparite of the mud-supported rocks of the Chachao Formation show two contrasting trends : decreasing-upward Sr and Na concentrations and increasing-upward Mg and Mn concentrations. The loss of Sr and Na are related to mineralogical stabilization of metastable carbonate particles involving the inversion of high-magnesium calcite to low-magnesium calcite, whereas local dolomitization in the upper part of the studied sequence has formed dolomite crystals showing different stages of dissolution due to meteoric and marine water influences. © 1999 Asociación Geológica Argentina.

Descripción: We present new cytogenetic, morphometric, and sperm morphology data of eight populations belonging to the C. pundti complex from Southern Córdoba and Eastern La Pampa Provinces in Argentina. The diploid numbers ranged from 2n = 44 to 2n = 50, and C- bands revealed a pattern of centromeric and pericentromeric heterochromatin. Comparisons of G-banded karyotypes revealed that the 2n = 44 (Holmberg, Santa Catalina, Sampacho), 2n = 46 (Realicó), 2n = 48 (El Guanaco, Guatraché), 2n = 46-48 (Vicuña Mackenna), and 2n = 50 (Puente Olmos) karyotypes, are closely related. In addition, these karyotypes show a high degree of homology (95%) with C. talarum talarum, despite the fact that five chromosomal rearrangements differentiate both taxa. Discriminant Function Analysis of morphometric data allows to distinguish three clusters: i) the C. mendocinus species group, ii) C. t. talarum, and iii) populations of the C. pundti complex proposed herein. The close phylogenetic relationship between C. talarum and the C. pundti complex, which undoubtedly belong to the same evolutionary lineage, is well supported by two different kinds of evidence: the extensive chromosomal homology and the same symmetric type of sperm. The morphological and chromosomal differences show that these two forms have diverged recently. © Publications Scientifiques du Muséum national d'Histoire naturelle.

Descripción: Abstract: Previous comparative genomic studies of genes involved in olfactory behavior in Drosophila focused only on particular gene families such as odorant receptor and/or odorant binding proteins. However, olfactory behavior has a complex genetic architecture that is orchestrated by many interacting genes. In this paper, we present a comparative genomic study of olfactory behavior in Drosophila including an extended set of genes known to affect olfactory behavior. We took advantage of the recent burst of whole genome sequences and the development of powerful statistical tools to analyze genomic data and test evolutionary and functional hypotheses of olfactory genes in the six species of the Drosophila melanogaster species group for which whole genome sequences are available. Our study reveals widespread purifying selection and limited incidence of positive selection on olfactory genes. We show that the pace of evolution of olfactory genes is mostly independent of the life cycle stage, and of the number of life cycle stages, in which they participate in olfaction. However, we detected a relationship between evolutionary rates and the position that the gene products occupy in the olfactory system, genes occupying central positions tend to be more constrained than peripheral genes. Finally, we demonstrate that specialization to one host does not seem to be associated with bursts of adaptive evolution in olfactory genes in D. sechellia and D. erecta, the two specialists species analyzed, but rather different lineages have idiosyncratic evolutionary histories in which both historical and ecological factors have been involved. © the author(s), publisher and licensee Libertas Academica Ltd.

Descripción: We study the emergence and evolution of AR NOAA 10314, observed on the solar disk during March 13-19, 2003. This extremely complex AR is of particular interest due to its unusual magnetic flux distribution and the clear rotation of the polarities of a d-spot within the AR. Using SOHO/MDI magnetograms we follow the evolution of the photospheric magnetic flux to infer the morphology of the structure that originates the AR. We determine the tilt angle variation for the d-spot and find a counter-clockwise rotation corresponding to a positive writhed flux tube. We compute the magnetic helicity injection and the total accumulated helicity in the AR and find a correlation with the observed rotation. © 2012 International Astronomical Union.

Descripción: Magnetic clouds (MCs) are objects in expansion during their travel through the heliosphere. In situ observations indicate that their front travel faster than their back, showing a clear empirical signature of expansion. With the aim of quantifying the expansion rate of MCs in the inner heliosphere (0.3 to 1 AU), we present here a statistical study of events observed by the spacecraft Helios 1 and 2, during their complete period of operations. From the analysis of the profile of the MC magnetic field components in its local frame, which is obtained from a rotation of the observed magnetic field vectors to a system of reference oriented as the main axis of the flux rope, we revise a list of events identified in previous works and redefine improved MC boundaries/orientation for each event. We then split the sample into two subsets according to the characteristics of their velocity profiles, (a) those MCs with a significantly perturbed velocity profile due to the interaction with their surrounding solar wind (i.e. overtaken by streams) and (b) those that are not perturbed. We compute the dimensionless local expansion rate (ζ) for MCs defined by several works [e.g. Démoulin et al., Solar Phys, 250, 347-374 (2008)]. We find significantly different distribution of values for ζ when perturbed and non perturbed events are considered. Non perturbed MCs expand at rates ζ consistent with the expected value from the global pressure decay in the surrounding solar wind for increasing helio-distances, while perturbed ones may present strong departures from that global rule. We interpret these departures of ζ for perturbed MCs as a consequence of interaction with streams on their expansion. © 2010 American Institute of Physics.

Descripción: Background. The rapid evolution of genital morphology is a fascinating feature that accompanies many speciation events. However, the underlying patterns and explanatory processes remain to be settled. In this work we investigate the patterns of intraspecific variation and interspecific divergence in male genitalic morphology (size and shape) in the cactophilic sibling species Drosophila buzzatii and D. koepferae. Genital morphology in interspecific hybrids was examined and compared to the corresponding parental lines. Results. Despite of being siblings, D. buzzatii and D. koepferae showed contrasting patterns of genital morphological variation. Though genitalic size and shape variation have a significant genetic component in both species, shape varied across host cacti only in D. buzzatii. Such plastic expression of genital shape is the first evidence of the effect of rearing substrate on genitalic morphology in Drosophila. Hybrid genital morphology was not intermediate between parental species and the morphological resemblance to parental strains was cross-dependent. Conclusion. Our results suggest the evolution of different developmental networks after interspecific divergence and the existence of a complex genetic architecture, involving genetic factors with major effects affecting genital morphology. © 2007 Soto et al; licensee BioMed Central Ltd.

Descripción: • Premise of the study: A new infrafamilial circumscription of the Verbenaceae with eight tribes: Casselieae, Citharexyleae, Duranteae, Lantaneae, Neospartoneae, Petreeae, Priveae, and Verbeneae, has been recently proposed, on the basis of molecular phylogenetic studies. Two genera, Dipyrena and Rhaphithamnus, remain unplaced. The aim of this work is to reconstruct the evolutionary history of morphological characters traditionally employed in the classification of the Verbenaceae, with special attention to tribes Verbeneae and Lantaneae. • Methods: Twenty-one characters, related to habit and vegetative morphology, inflorescence and floral morphology, ovary and fruit morphology, as well as chromosome number, were optimized over a molecular phylogeny of Verbenaceae. • Key Results: All tribes are supported by at least one morphological trait except tribes Duranteae and Citharexyleae. Suffrutescent habit, sessile flowers, and four cluses are synapomorphies for tribe Verbeneae. Gynoecium with short style and entire stigma are synapomorphic traits for tribe Lantaneae. Sessile flowers and unicarpellate ovaries are morphological synapomorphies for the new tribe Neospartoneae. Suffrutescent habit is a synapomorphic trait for tribe Priveae. Homothetic pleiobotrya and absence of the adaxial staminode are synapomorphic traits for tribe Casselieae. Undivided fleshy fruits are probably a synapomorphic trait for tribe Petreeae. Putative plesiomorphies for the ancestor of the Verbenaceae are discussed as well as synapomorphic traits within other Verbenaceae clades. • Conclusions: Many of the characters traditionally employed in classification have proven to be very homoplastic, or have been shown not to support relationships within the family. Moreover, traditional assumptions concerning character polarity have in some cases been shown to be incorrect. © 2012 Botanical Society of America.

Descripción: The line-of-sight magnetograms from Solar Optical Telescope Narrowband Filter Imager observations of NOAA Active Region 10930 have been used to study the evolution of spinning and braiding helicities over a period of five days starting from 2006 December 9. The north (N) polarity sunspot was the follower and the south (S) polarity sunspot was the leader. The N-polarity sunspot in the active region was rotating in the counterclockwise direction. The rate of rotation was small during the first two days of observations and it increased up to 8°hr-1 on the third day of the observations. On the fourth and fifth days it remained at 4°hr-1 with small undulations in its magnitude. The sunspot rotated about 260° in the last three days. The S-polarity sunspot did not complete more than 20° in five days. However, it changed its direction of rotation five times over a period of five days and injected both the positive and negative type of spin helicity fluxes into the corona. Through the five days, both the positive and negative sunspot regions injected equal amounts of spin helicity. The total injected helicity is predominantly negative in sign. However, the sign of the spin and braiding helicity fluxes computed over all the regions were reversed from negative to positive five times during the five-day period of observations. The reversal in spinning helicity flux was found before the onset of the X3.4-class flare, too. Though, the rotating sunspot has been observed in this active region, the braiding helicity has contributed more to the total accumulated helicity than the spinning helicity. The accumulated helicity is in excess of -7 × 1043Mx2 over a period of five days. Before the X3.4-class flare that occurred on 2006 December 13, the rotation speed and spin helicity flux increased in the S-polarity sunspot. Before the flare, the total injected helicity was larger than -6 × 1043Mx2. The observed reversal in the sign of spinning and braiding helicity fluxes could be the signature of the emergence of a twisted flux tube, which acquires the writhe of an opposite sign. The magnetic cloud associated with the ejected mass has carried about -7 × 1041Mx2 of helicity. A time integration of helicity flux of about 1.2hr integrated backward in time of the observation of the coronal mass ejection is sufficient for this event. © 2011. The American Astronomical Society. All rights reserved.

Descripción: The combination of differential emission measure tomography with extrapolation of the photospheric magnetic field allows determination of the electron density and electron temperature along individual magnetic field lines. This is especially useful in quiet-Sun (QS) plasmas where individual loops cannot otherwise be identified. In Paper I, this approach was applied to study QS plasmas during Carrington rotation (CR) 2077 at the minimum between solar cycles (SCs) 23 and 24. In that work, two types of QS coronal loops were identified: "up" loops in which the temperature increases with height, and "down" loops in which the temperature decreases with height. While the first ones were expected, the latter ones were a surprise and, furthermore, were found to be ubiquitous in the low-latitude corona. In the present work, we extend the analysis to 11 CRs around the last solar minimum. We found that the "down" population, always located at low latitudes, was maximum at the time when the sunspot number was minimum, and the number of down loops systematically increased during the declining phase of SC-23 and diminished during the rising phase of SC-24. "Down" loops are found to have systematically larger values of β than do "up" loops. These discoveries are interpreted in terms of excitation of Alfvén waves in the photosphere, and mode conversion and damping in the low corona. © 2013. The American Astronomical Society. All rights reserved..

Descripción: We introduce an effective one-uid description of the interacting dark sector in a spatially at Friedmann-Robertson-Walker space-time and investigate the stability of the power-law solutions. We find the "source equation" for the total energy density and determine the energy density of each dark component. We study linear and nonlinear interactions which depend on the dark matter and dark energy densities, their first derivatives, the total energy density with its derivatives up to second order and the scale factor. We solve the evolution equations of the dark components for both interactions, examine exhaustively several examples and show cases where the problem of the coincidence is alleviated. We show that a generic nonlinear interaction gives rise to the "relaxed Chaplygin gas model" whose effective equation of state includes the variable modified Chaplygin gas model while some others nonlinear interactions yield de Sitter and power-law scenarios. © 2012 American Institute of Physics.

Descripción: In this Letter an intrinsically non-Abelian black hole solution for the SU(2) Einstein-Yang-Mills theory in four dimensions is constructed. The gauge field of this solution has the form of a meron whereas the metric is the one of a Reissner-Nordström black hole in which, however, the coefficient of the 1/r2 term is not an integration constant. Even if the stress-energy tensor of the Yang-Mills field is spherically symmetric, the field strength of the Yang-Mills field itself is not. A remarkable consequence of this fact, which allows to distinguish the present solution from essentially Abelian configurations, is the Jackiw-Rebbi-Hasenfratz-'t Hooft mechanism according to which excitations of Bosonic fields moving in the background of a gauge field with this characteristic behave as Fermionic degrees of freedom. © 2013 Elsevier B.V.

Descripción: In this paper we consider a class of symmetric Cantor sets in R. Under certain separation condition we determine the exact packing measure of such a Cantor set through the computation of the lower density of the uniform probability measure supported on the set. With an additional restriction on the dimension we give also the exact centered Hausdorff measure by computing the upper density. © 2011 Elsevier Inc.

Descripción: We calculate the exact Casimir interaction energy between two perfectly conducting, very long, eccentric cylindrical shells using a mode summation technique. Several limiting cases of the exact formula for the Casimir energy corresponding to this configuration are studied both analytically and numerically. These include concentric cylinders, cylinder-plane and eccentric cylinders, for small and large separations between the surfaces. For small separations we recover the proximity approximation, while for large separations we find a weak logarithmic decay of the Casimir interaction energy, typical of cylindrical geometries. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Descripción: A recursive reformulation of Sierpinski's construction of an absolutely normal number was provided. The reformulation produced a computable absolute normal number in base 2, which was normal in any scale considered. The construction was adapted to define numbers in any other bases and distinct numbers were obtained for different bases.

Descripción: We carried out molecular dynamics simulation experiments to examine equilibrium and dynamical characteristics of the solvation of excess protons in mesoscopic, [m:n] binary polar clusters comprising m 50 water molecules and n 6, 25, and 100 acetone molecules. Contrasting from what is found in conventional macroscopic phases, the characteristics of the proton solvation are dictated, to a large extent, by the nature of the concentration fluctuations prevailing within the clusters. At low acetone contents, the overall cluster morphology corresponds to a segregated aqueous nucleus coated by an external aprotic phase. Under these circumstances, the proton remains localized at the surface of the water core, in a region locally deprived from acetone molecules. At higher acetone concentrations, we found clear evidence of the onset of the mixing process. The cluster structures present aqueous domains with irregular shape, fully embedded within the acetone phase. Still, the proton remains coordinated to the aqueous phase, with its closest solvation shell composed exclusively by three water molecules. As the relative concentration of acetone increases, the time scales characterizing proton transfer events between neighboring water molecules show considerable retardations, stretching into the nanosecond time domain already for n ∼ 25. In water-rich aggregates, and similarly to what is found in the bulk, proton transfers are controlled by acetone/water exchange processes taking place at the second solvation shell of the proton. As a distinctive feature of the transfer mechanism, translocation pathways also include diffusive motions of the proton from the surface down into inner regions of the underlying water domain. © 2012 American Institute of Physics.

Descripción: Using molecular dynamics experiments, we analyze equilibrium and dynamical characteristics related to the solvation of excess protons in water-acetone mixtures. Our approach is based on the implementation of an extended valence-bond Hamiltonian, which incorporates translocation of the excess charge between neighboring water molecules. Different mixtures have been analyzed, starting from the pure water case down to solutions with a water molar fraction x w 0.25. In all cases, we have verified that the structure of the first solvation shell of the H 3 O moiety remains practically unchanged, compared to the one observed in pure water. This shell is composed by three water molecules acting as hydrogen bond acceptors, with no evidence of hydrogen bond donor-like connectivity. Moreover, the increment in the acetone concentration leads to a gradual stabilization of Eigen-like [H 3O·(H 2O) 3] configurations, in detriment of Zundel-like [H·(H 2O) 2] ones. Rates of proton transfer and proton diffusion coefficients have been recorded at various water-acetone relative concentrations. In both cases, we have found a transition region, in the vicinity of x w ∼ 0.8, where the concentration dependences of the two magnitudes change at a quantitative level. A crude estimate shows that, at this tagged concentration, the volumes occupied by the two solvents become comparable. The origins of this transition separating water-rich from acetone-rich realms is rationalized in terms of modifications operated in the nearby, second solvation shell, which in the latter solutions, normally includes at least, one acetone molecule. Our results would suggest that one possible mechanism controlling the proton transfer in acetone-rich solutions is the exchange of one of these tagged acetone molecules, by nearby water ones. This exchange would give rise to Zundel-like structures, exhibiting a symmetric, first solvation shell composed exclusively by water molecules, and would facilitate the transfer between neighboring water molecules along the resonant complex. © 2012 American Institute of Physics.

Descripción: Perturbing the Navier-Stokes equation in the ionospheric F-region, the dispersion relation and the unstable regions in wavenumber space are derived as a function of two control parameters, the colatitude θ and the slow time evolution for tidal modes τ. Our results satisfy the internal gravity wave (IGW) dispersion relation and are in good agreement with observational data. Also, we obtained a nice prediction for the excitation regions of these modes in the parameter space (θ, τ). The distribution of IGW excitations, in this parameter space is in very good agreement with observational data distributed along the day. An alternative explanation to the disappearence of IGW near the equator is given. Our model predicts an interesting latitude dependence, which needs to be tested by new observational data.

Descripción: The Navier-Stokes, continuity and energy balance equations including magnetic effects for an inviscid compressible fluid in the ionospheric F-region were perturbed around the tidal phenomenological solution. We imposed adiabaticity and incompressibility to the perturbation. Our results satisfy the internal gravity wave (IGW) dispersion relation. The stable and unstable regions of these modes were derived as a function of two control parameters, the colatitude θ and the slow time evolution for tidal modes τ. These regions were obtained for different values of the magnetic field intensity, showing good agreement with observational data for the South Atlantic anomaly. Our model predictions for other magnetic field intensities corresponding to other latitude dependences need to be contrasted with new observational data. In addition we show for some hours and latitudes that, resonant interaction occurs between low frequency tidal waves and two high frequency gravity waves. In these regions, where tidal modes are linearly unstable, the gravity group velocity is modulated by a function of the tidal phase velocity.

Descripción: Some strains of Bacillus sphaericus are entomopathogenic to mosquito larvae, which transmit diseases, such as filariasis and malaria, affecting millions of people worldwide. This species is unable to use hexoses and pentoses as unique carbon sources, which was proposed to be due to the lack of glycolytic enzymes, such as 6-phosphofructokinase (PFK). In this study, PFK activity was detected and the pfk gene was cloned and sequenced. Furthermore, this gene was shown to be present in strains belonging to all the homology groups of this heterogeneous species, in which PFK activity was also detected. A careful sequence analysis revealed the conservation of different catalytic and regulatory residues, as well as the enzyme's phylogenetic affiliation with the family of allosteric ATP-PFK enzymes.

Descripción: Relativistic Schrödinger equation with a nonlinear potential interaction describes the dynamics of a particle, with rest mass m, travelling to a significant fraction |v| < 1 of the light speed c = 1. At first, we deal with the local and global existence of solutions of the flux, and in the second term, and according to the relativistic nature of the problem, we look for boosted solitons as ψ(x, t) = eiμtφv(x - vt), where the profile φ v ∈ H 1/2 (R{double-struck}) is a minimizer of a suitable variational problem. Our proof uses a concentration-compactness-type argument. Stability results for the boosted solitons are established. © 2012 American Institute of Physics.

Descripción: We prove the existence of nontrivial solutions to the system Δpu = |u|p-2u, Δqv = |v| q-2v, on a bounded set of ℝN, with nonlinear coupling at the boundary given by |∇u|p-2∂u/∂ν = F u(x, u, v), |∇u|q-2∂v/∂ν = F v(x, u, v). The proofs are done under suitable assumptions on the potential F, and based on variational arguments. Our results include subcritical, resonant and critical growth on F. © 2007 Birkhäuser Verlag.

Descripción: In this paper we study the existence of nontrivial solutions for the problem Δpu = up-2u in a bounded smooth domain Ω ⊂ ℝN, with a nonlinear boundary condition given by |∇u|p-2∂u/∂v = f(u) on the boundary of the domain. The proofs are based on variational and topological arguments. © 2001 Academic Press.

Descripción: Context. A large amount of magnetized plasma is frequently ejected from the Sun as coronal mass ejections (CMEs). Some of these ejections are detected in the solar wind as magnetic clouds (MCs) that have flux rope signatures. Aims. Magnetic clouds are structures that typically expand in the inner heliosphere. We derive the expansion properties of MCs in the outer heliosphere from one to five astronomical units to compare them with those in the inner heliosphere. Methods. We analyze MCs observed by the Ulysses spacecraft using in situ magnetic field and plasma measurements. The MC boundaries are defined in the MC frame after defining the MC axis with a minimum variance method applied only to the flux rope structure. As in the inner heliosphere, a large fraction of the velocity profile within MCs is close to a linear function of time. This is indicative of a self-similar expansion and a MC size that locally follows a power-law of the solar distance with an exponent called ζ. We derive the value of ζ from the in situ velocity data. Results. We analyze separately the non-perturbed MCs (cases showing a linear velocity profile almost for the full event), and perturbed MCs (cases showing a strongly distorted velocity profile). We find that non-perturbed MCs expand with a similar non-dimensional expansion rate (ζ = 1.05 ± 0.34), i.e. slightly faster than at the solar distance and in the inner heliosphere (ζ = 0.91 ± 0.23). The subset of perturbed MCs expands, as in the inner heliosphere, at a significantly lower rate and with a larger dispersion (ζ = 0.28 ± 0.52) as expected from the temporal evolution found in numerical simulations. This local measure of the expansion also agrees with the distribution with distance of MC size, mean magnetic field, and plasma parameters. The MCs interacting with a strong field region, e.g. another MC, have the most variable expansion rate (ranging from compression to over-expansion). © 2012 ESO.

Descripción: We experimentally assessed the effect of controlling vegetation height along farm perimeters on the abundance of rodents in 2 broiler poultry farms in central Argentina. We carried out an experimental design based on the before-after-control-impact method. After vegetation treatments, there was a significant decrease in rodent abundance at the perimeter of the farm with control of vegetation height because of the reduction of the Pampean grassland mouse Akodon azarae. In poultry houses, there was a significant decrease in rodent abundance on nonaffected farms because of the reduction of the commensal house mouse Mus musculus domesticus, possibly because of a major collocation of rodenticide. Our results indicate that both the control of vegetation growth at the perimeters and the appropriate timing of rodenticide applications are effective measures for rodent control on broiler poultry farms when both control measures are applied simultaneously. We achieved effective rodent control through an understanding of the habitat use and population dynamics of the species involved and the characteristics of the area where the control program would be applied. © 2009 Poultry Science Association, Inc.

Descripción: An experimental study using mesocosms was conducted in the main shallow lake of a temperate wetland (Otamendi Natural Reserve, Argentina) to analyse the impact of zooplankton on phytoplankton and the microbial assemblages. The lake is characterised by the presence of a fluctuating cover of floating macrophytes, whose shading effects shape the phytoplakton community and the ecosystem functioning, which was absent during the study period. The experiment was run in situ using polyethylene bags, comparing treatments with and without zooplankton. The cascade effect of zooplankton on phytoplankton and the lower levels of the microbial food web (ciliates, heterotrophic nanoflagellates (HNF) and picoplankton) were analysed. A significant zooplankton grazing on the nano-phytoplankton fraction (3-30 μm) was observed. Conversely, large algae (filamentous cyanobacteria, colonial chlorophytes and large diatoms) increased in all mesocosms until day 10, suggesting that they were not actively grazed by zooplankton during this period. However, from day 10 until day 17 this fraction decreased in the enclosures with mesozooplankton, probably due to an increase in the abundance of large herbivores. The results of the experiment would also indicate a trophic cascade effect on the lower levels of the microbial community. In the treatment where zooplankton was removed, the abundance of ciliates followed the same increasing pattern as the abundance of HNF, but with a time lag in its response. In the enclosures without zooplankton, HNF remained relatively constant throughout the experiment, whereas ciliates strongly decrease during the last week. Total picoplankton abundance increased in the enclosures with mesozooplankton, thus supporting the existence of a four-link trophic cascade (copepods-microzooplankton-HNF-picoplankton). Zooplankton composition changed significantly from the beginning until the end of the experiment; cyclopoid nauplii and rotifers were notoriously dominant at t0, whereas 10 days later the community showed a more equitable proportion of cyclopoids, calanoids, nauplii, cladocerans and rotifers. © 2006 Elsevier GmbH. All rights reserved.

Descripción: An experimental study using microcosms was conducted in a South American wetland, Lower Paraná River Basin (Argentina), to analyse the structure of the components of the microbial plankton community and the influence of the light deficiency due to floating macrophytes on this community. Two experiments were run under different light conditions; the decrease of the light penetration due to floating macrophytes was simulated using different nylon mesh covers that resembled natural conditions in the lake. These studies revealed that the light deficiency favoured the replacement of obligate autotrophs by mixotrophic and heterotrophic organisms. Abundances of strictly autotrophic algae along the experiments responded to the light gradient, being maximum in the flasks without cover. Heterotrophic nanoflagellates (HNF) and ciliates increased in the microcosms, probably favoured by the high food availability (picoplankton) and the lack of their predators (zooplankton). The increase of ciliates was higher in the microcosms with more light. In the first experiment, the picoplankton fraction strongly decreased after 24 h in the flasks that included all their potential predators, thus suggesting a grazing pressure on this fraction. Grazing experiments performed with fluorescent-labelled bacteria (FLB) revealed that two Cryptomonas species, which are frequent in the lake (Cryptomonas erosa and Cryptomonas marssonii), can ingest bacteria. © The Author 2006. Published by Oxford University Press. All rights reserved.

Descripción: An experimental validation of an model for the production of birdsongs was discussed. The derivation of the model with functions whose time dependence came from recordings of muscle activities and air sac pressure was studied. It was found that birds' songs were recorded and compared with the synthetic songs. Some predictions of the model concerning the relative levels of activity in the gating muscles at the beginning and end of a syllable were also tested.

Descripción: The role of GAs in promoting seed germination is well known and experiments with seeds from different species have suggested the requirement of de novo synthesis of GAs upon imbibition for germination. There are also strong indications that the enhancement of GA synthesis is part of the mechanism through which environmental signals (i.e. light) induce germination. Since along the GA biosynthetic pathway, oxidation at C-20 carried out by GA 20-oxidases is thought to be a site of regulation, a cDNA clone encoding a GA 20-oxidase was isolated from embryos of sorghum (SbGA 20ox). Expression analysis of this gene in embryos within imbibed caryopses with low dormancy showed detectable amounts of the specific mRNA early upon incubation, increasing thereafter. In contrast, it remained barely detectable in embryos from dormant caryopses. Changes in endogenous GA4 levels were in agreement with those of SbGA 20ox mRNA, suggesting that GA production might be regulated differentially at the level of transcription of this gene. The expression of SbGA 20ox was enhanced in incubated embryos isolated from either type of caryopses, illustrating a physiological control exerted by the surrounding seed tissues on gene expression. The results also show that ABA leads to a suppression of transcription of this gene.

Descripción: Background and AimsPre-harvest sprouting susceptibility in grain sorghum (Sorghum bicolor) is related to low seed dormancy and reduced embryo sensitivity to inhibition of germination by abscisic acid (ABA). Intra-specific variability for pre-harvest sprouting might involve differential regulation of ABA signalling genes.MethodsSorghum genes encoding homologues for ABA signalling components from other species (ABI5, ABI4, VP1, ABI1 and PKABA1) were studied at the transcriptional and protein level (ABI5) during grain imbibition for two sorghum lines with contrasting sprouting phenotypes and in response to hormones.Key ResultsTranscript levels of these genes and protein levels of ABI5 were higher in imbibed immature caryopses of the more dormant line. Dormancy loss was related to lower transcript levels of these genes and lower ABI5 protein levels in both genotypes. Exogenous ABA inhibited germination of isolated embryos but failed to prevent ABI5 rapid decrease supporting a role for the seed coat in regulating ABI5 levels.ConclusionsSeveral genes involved in ABA signalling are regulated differently in imbibed caryopses from two sorghum lines with contrasting pre-harvest sprouting response before - but not after - physiological maturity. A role for ABI5 in the expression of dormancy during grain development is discussed.

Descripción: VjbR is a LuxR homolog that regulates transcription of many genes including important virulence determinants of the facultative intracellular pathogen Brucella abortus. This transcription factor belongs to a family of regulators that participate in a cell-cell communication process called quorum sensing, which enables bacteria to respond to changes in cell population density by monitoring concentration of self produced autoinducer molecules. Unlike almost all other LuxR-type proteins, VjbR binds to DNA and activates transcription in the absence of any autoinducer signal. To investigate the mechanisms by which Brucella induces VjbR-mediated transcriptional activation, and to determine how inappropriate spatio-temporal expression of the VjbR target genes is prevented, we focused on the study of expression of vjbR itself. By assaying different parameters related to the intracellular lifestyle of Brucella, we identified a restricted set of conditions that triggers VjbR protein expression. Such conditions required the convergence of two signals of different nature: a specific pH value of 5.5 and the presence of urocanic acid, a metabolite involved in the connection between virulence and metabolism of Brucella. In addition, we also observed an urocanic acid, pH-dependent expression of RibH2 and VirB7, two additional intracellular survival-related proteins of Brucella. Analysis of promoter activities and determination of mRNA levels demonstrated that the urocanic acid-dependent mechanisms that induced expression of VjbR, RibH2, and VirB7 act at the post-transcriptional level. Taken together, our findings support a model whereby Brucella induces VjbR-mediated transcription by modulating expression of VjbR in response to specific signals related to the changing environment encountered within the host. © 2012 Arocena et al.

Descripción: Fil:Catren, G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Temporal pattern of hatching was studied in the subantarctic lithodid crabs Lithodes santolla (Molina) and Paralomis granulosa (Jaquinot) from the Argentine Beagle Channel. In both species, larval hatching occurred in low daily numbers over an extended period of up to several weeks, depending on hatch size. Low daily hatching activity and low oxygen-consumption rates in freshly hatched P. granulosa larvae are discussed as life history adaptations to, and/or physiological constraints by, the environmental conditions of high latitudes.

Descripción: Given a homogeneous polynomial on a Banach space E belonging to some maximal or minimal polynomial ideal, we consider its iterated extension to an ultrapower of E and prove that this extension remains in the ideal and has the same ideal norm. As a consequence, we show that the Aron-Berner extension is a well defined isometry for any maximal or minimal ideal of homogeneous polynomials. This allows us to obtain symmetric versions of some basic results of the metric theory of tensor products. © 2010 Research Institute for Mathematical Sciences, Kyoto University. All rights reserved.

Descripción: We introduce the notion of Timed I/O Components as Timed Automata "á la" Alur & Dill where an "admissible" I/O interface is declared. That notion has, what we consider, a key modeling property: non-zeno preservation under syntactically-checkable "I/O compatibility" among interacting components. Also a reduced parallel composition is posssible based on the ability of statically detect influence of behavior between components [8,10,11]. On the other hand, with some simple extra conditions, modular assume-guarantee style of reasoning like [15,19] is valid in our model. © 2002 Published by Elsevier Science B. V.

Descripción: This contribution presents the results of a first stage of a study of the Tordillo Formation in southwestern Mendoza province. This unit, assigned to the Kimmeridgian, represents a continentalization of the Neuquén Basin. It consists mainly of fluvial deposits associated with eolian and playa lake deposits. The reconstruction of the thickness variations of this unit, the presence of synsedimentary normal faults and a provenance study in sandstones from two localities, which shows that sediment supply came from both margins of the basin, suggest that the Tordillo Formation was deposited during an extensional period, in a similar way to what is observed in the Cerro Aconcagua area and in the Sexta Region in Chile.

Descripción: We study the extendibility of integral vector-valued polynomials on Banach spaces. We prove that an X-valued Pietsch-integral polynomial on E extends to an X-valued Pietsch-integral polynomial on any space F containing E, with the same integral norm. This is not the case for Grothendieck-integral polynomials: they do not always extend to X-valued Grothendieck-integral polynomials. However, they are extendible to X-valued polynomials. The Aron-Berner extension of an integral polynomial is also studied. A canonical integral representation is given for domains not containing ℓ1. © 2004 Elsevier Inc. All rights reserved.

Descripción: We previously demonstrated that extracellular bacterial DNA activates neutrophils through a CpG- and TLR9-independent mechanism. Biofilms are microbial communities enclosed in a polymeric matrix that play a critical role in the pathogenesis of many infectious diseases. Because extracellular DNA is a key component of biofilms of different bacterial species, the aim of this study was to determine whether it plays a role in the ability of biofilms to induce human neutrophil activation. We found that degradation of matrix extracellular DNA with DNase I markedly reduced the capacity of Pseudomonas aeruginosa biofilms to induce the release of the neutrophil proinflammatory cytokines IL-8 and IL-1β (>75%); reduced the upregulation of neutrophil activation markers CD18, CD11b, and CD66b (p < 0.001); reduced the number of bacteria phagocytosed per neutrophil contacting the biofilm; and reduced the production of neutrophil extracellular traps. Consistent with these findings, we found that biofilms formed by the lasI rhlI P. aeruginosa mutant strain, exhibiting a very low content of matrix extracellular DNA, displayed a lower capacity to stimulate the release of proinflammatory cytokines by neutrophils, which was not decreased further by DNase I treatment. Together, our findings support that matrix extracellular DNA is a major proinflammatory component of P. aeruginosa biofilms. Copyright © 2010 by The American Association of Immunologists, Inc.

Descripción: We present results on the quark and gluon polarization in the nucleon obtained in a combined next to leading order analysis to the available inclusive and semi-inclusive polarized deep inelastic scattering data. © 2005 American Institute of Physics.

Descripción: This article generalizes recent results in the extra invariance for shift-invariant spaces to the context of LCA groups. Let G be a locally compact abelian (LCA) group and K a closed subgroup of G. A closed subspace of L2(G) is called K-invariant if it is invariant under translations by elements of K. Assume now that H is a countable uniform lattice in G and M is any closed subgroup of G containing H. In this article we study necessary and sufficient conditions for an H-invariant space to be M-invariant. As a consequence of our results we prove that for each closed subgroup M of G containing the lattice H, there exists an H-invariant space S that is exactly M-invariant. That is, S is not invariant under any other subgroup M' containing H. We also obtain estimates on the support of the Fourier transform of the generators of the H-invariant space, related to its M-invariance. © 2010 Elsevier Inc.

Descripción: The lucinid bivalve Lucina pensylvanica possesses an unusual flexible commarginal shell sculpture formed from calcified periostracal lamellae. The lamellae comprise thick, recurved, periostracal extensions with distal calcified scales. The periostracum is also densely embedded with calcareous granules around 2.0-2.5 μm in diameter and a thin (10 μm) layer of prismatic aragonite covers the ventral face of each lamella. Other species of Lucina in the western Atlantic possess calcified scales but with different morphologies and the continuous commarginal ridges of the eastern Atlantic Lucina adansoni and other African species are similarly constructed and homologous. The periostracal lamellae are a probable apomorphy of the genus Lucina and morphology of the calcified structures provides a set of systematic characters of importance in the discrimination of species.