Descripción: This work presents results, over the South American region, from the CSIRO Division of Atmospheric Research limited area model (DARLAM) and from the ninelevel general circulation model (GCM) of CSIRO (CSIRO Mk 2), within which it was nested in a one-way mode. Ten separate 30-day DARLAM simulations were performed for both January and July with a resolution of 125 km and were averaged to obtain a climatology for those months. This paper presents for the first time simulations of the January South American climate using a limited area model; previous similar studies simulated only the July climate. The goal of this study was to examine the capability of the CSIRO Mk 2 - DARLAM nested modeling system for simulating the climate in the South American region. Further, it was desired to investigate whether the higher resolution of DARLAM improves the simulated climate over various subregions, compared with the GCM and observations. With this purpose, a representative set of variables was analyzed and statistically compared. Overall, the fields simulated by the nesting system provide a better representation of the South American climate than the GCM. In particular, significant improvements are found in the nested model climatology for near-surface temperature and mean sea level pressure. Comparison of the January and July simulations shows a better wintertime performance. Some significant summertime features, like the Bolivian High, are reasonably well simulated by DARLAM, but not by the GCM. Copyright 2002 by the American Geophysical Union.

Descripción: [i] This work presents results, over the South American region, from the CSIRO Division of Atmospheric Research limited area model (DARLAM) and from the ninelevel general circulation model (GCM) of CSIRO (CSIRO Mk 2), within which it was nested in a one-way mode. Ten separate 30-day DARLAM simulations were performed for both January and July with a resolution of 125 km and were averaged to obtain a climatology for those months. This paper presents for the first time simulations of the January South American climate using a limited area model; previous similar studies simulated only the July climate. The goal of this study was to examine the capability of the CSIRO Mk 2 - DARLAM nested modeling system for simulating the climate in the South American region. Further, it was desired to investigate whether the higher resolution of DARLAM improves the simulated climate over various subregions, compared with the GCM and observations. With this purpose, a representative set of variables was analyzed and statistically compared. Overall, the fields simulated by the nesting system provide a better representation of the South American climate than the GCM. In particular, significant improvements are found in the nested model climatology for near-surface temperature and mean sea level pressure. Comparison of the January and July simulations shows a better wintertime performance. Some significant summertime features, like the Bolivian High, are reasonably well simulated by DARLAM, but not by the GCM. Copyright 2002 by the American Geophysical Union.

Descripción: We present 3D, gasdynamic simulations of jet/cloud collisions, with the purpose of modelling the HH 270/110 system. From the models, we obtain predictions of Hα and H2 1-0 s(1) emission line maps, which qualitatively reproduce some of the main features of the corresponding observations of HH 110. We find that the model that better reproduces the observed structures corresponds to a jet that was deflected at the surface of the cloud ∼ 1000 yr ago, but is now boring a tunnel directly into the cloud. This model removes the apparent contradiction between the jet/cloud collision model and the lack of detection of molecular emission in the crossing region of the HH 270 and HH 110 axes.

Descripción: We obtain in this article theorems on linear fractional transformations of j-expansive matrix-valued functions wich provide a procedure to synthetize linear passive 2n-ports. In particular, these results permit us to solve the problem of Darlington realizations of transfer-scattering matrices of linear passive 2n-ports on the basis of the synthesis of transfer-scattering matrices of linear 4n-ports without losses. It is a pleasure to acknowledge our debt to the remarkable paper [4] by Arov. © 1983.

Descripción: Given X a complex Banach space, L a complex nilpotent finite dimensional Lie algebra, and ρ: L → L(X), a representation of L in X such that ρ(l) ∈ K(X) for all l → L, the Taylor, the Słodkowski, the Fredholm, the split and the Fredholm split joint spectra of the representation ρ are computed.

Descripción: Stress granules (SGs) are ephemeral cytoplasmic aggregates containing stalled translation preinitiation complexes involved in mRNA storage and triage during the cellular stress response. SG formation is triggered by the phosphorylation of the alpha subunit of eIF2 (eIF2α), which provokes a dramatic blockage of protein translation. Our results demonstrate that acute infection of Vero cells with the arenavirus Juni{dotless} ́n (JUNV), aetiological agent of Argentine haemorrhagic fever, does not induce the formation of SGs. Moreover, JUNV negatively modulates SG formation in infected cells stressed with arsenite, and this inhibition correlates with low levels of eIF2α phosphorylation. Transient expression of JUNV nucleoprotein (N) or the glycoprotein precursor (GPC), but not of the matrix protein (Z), inhibits SG formation in a similar manner, comparable to infectious virus. Expression of N and GPC also impaired eIF2α phosphorylation triggered by arsenite. A moderate inhibition of SG formation was also observed when DTT and thapsigargin were employed as stress inducers. In contrast, no inhibition was observed when infected cells were treated with hippuristanol, a translational inhibitor and inducer of SGs that bypasses the requirement for eIF2α phosphorylation. Finally, we analysed SG formation in persistently JUNV-infected cells, where N and GPC are virtually absent and truncated N products are expressed abundantly.Wefound that persistently infected cells show a quite normal response to arsenite, with SG formation comparable to that of uninfected cells. This suggests that the presence of GPC and/or N is crucial to control the stress response upon JUNV infection of Vero cells © 2011 SGM.

Descripción: The Jurassic history of southern South America shows a complex geologic evolution which is the result of different processes that began along the western Gondwana margin during the initial stages of Pangea breakup. Andean subduction along the Pacific continental margin began in the Early Jurassic, after a period of continental-scale extension and rifting, which peaked by the end of the Triassic in central and northern Argentina and Chile. Renewal of subduction was the result of an episode of ocean growth along a series of spreading centers between North and South America when the separation of these continents began as a consequence of the activity of the Central Atlantic Magmatic Province hotspot. Motion along these spreading centers produced a component of oblique, SE-directed subduction along the western margin of South America and the reactivation of inherited orthogonal structural features as the N70°E trending Huincul ridge in the Neuquén Basin that was uplifted during Jurassic times. Subduction along the north-south trending Argentine-Chilean continental margin acelerated during the break-up between West and East Gondwana soon after the opening of the Indian Ocean, linked to the Karoo hot-spot. Subduction took place under extensional conditions probably associated with a negative trench roll-back, leading to the formation of a magmatic arc along the Coast Ranges from southern Peru to central Chile and, to the east, the Arequipa, Tarapacá and Neuquén extensional back-arc basins. In northern Patagonia, early Jurassic arc related magmatism occurred to the east of the present day Andean Cordillera along the short-lived (190-170 Ma) Subcordilleran Batholith and the associated Liassic intra arc basin. Arc magmatism ceased in northern Patagonia at ca 170 Ma to be replaced by huge volumes of Early to Middle Jurassic rhyolites and dacites of the Chon-Aike Large Igneous province produced as a result of crustal melting in an overheated crust during the initial stages of Gondwana breakup. Early rifting during Middle-Late Jurassic times took place in the Cañadón Asfalto Basin and the Late Jurassic Río Guenguel, Río Mayo and Río Senguerr basins, orthogonal to the continental margin as a consequence of the Weddell Sea opening. Acid magmatism was associated with widespread extension and culminated in the opening of the ocean-floored Rocas Verdes Basin. The causes of the cessation of magmatism in the Subcordilleran Batholith, the origin of the Chon Aike LIP and the rotation of the magmatic front towards the Patagonian Batholith around 150 Ma are still not well understood. Hypothesis linking this mutating tectonic scenario to the collision of exotic terranes against the Pacific margin of Patagonia during the early to middle Jurassic should be taken into consideration.

Descripción: The G protein-coupled receptor oncogene (vGPCR) of the Kaposi's sarcoma (KS) associated herpesvirus (KSHV), an oncovirus implicated in angioproliferative neoplasms, induces angiogenesis by VEGF secretion. Accordingly, we found that expression of vGPCR in human umbilical vein endothelial cells (HUVEC) leads to immortalization with constitutive VEGF receptor-2/ KDR expression and activation. vGPCR immortalization was associated with anti-senescence mediated by alternative lengthening of telomeres and an anti-apoptotic response mediated by vGPCR constitutive signaling and KDR autocrine signaling leading to activation of the PI3K/AKT pathway. In the presence of the KS growth factor VEGF, this mechanism can sustain suppression of signaling by the immortalizing gene. We conclude that vGPCR can cause an oncogenic immortalizing event and recapitulate aspects of the KS angiogenic phenotype in human endothelial cells, pointing to this gene as a pathogenic determinant of KSHV.

Descripción: Meiotic and/or mitotic chromosome numbers were determined and observations on meiotic behavior were made in 14 accessions belonging to 14 especies concerning 8 genera distributed in 4 tribes of the Asteraceae. Five species are investigated chromosomally for the first time. These are as follows, tribe Mutisieae: Brachyclados cespitosus(Phil.) Speg. (n = 23), Nassauvia pygmaea (Cass.) Hooker (n = 22); tribe Cichorieae: Hypochoeris acaulis (Remy) Britton (n = 4, 2n = 8), Hieracium glaucifolium Poepp. ex Froelich in DC. (2n = 18) and Hieracium aff. palezieuxii Zahn (2n = 18). Different chromosome number to those previously reported in the literature were found for Hypochoeris chondrilloides (A. Gray) Cabrera (n = 8), Baccharis ulicina Hook. Arn. (2n = 18+3B), Conyza aff. bonariensis (L.) Cronquist (2n = 18). The karyotypes of Brachyclados lycioides Don, Hypochoeris acaulis (Remy) Britton, Hieracium aff. palezieuxii Zahn and Senecio chilensis Less. are described for the first time. Meanwhile, the karyotypes of Hypochoeris microcephala (Sch. Bip.) Cabrera var. albiflora (Kuntze) Cabrera, H. chillensis (Kunth) Hieron. and H. megapotamica Cabrera showed to be slightly different with those described in previous publications. The significance of some of the results in relation to taxonomical and evolutionary problems is discussed.

Descripción: This paper presents the karyotype, DNA content and meiotic behaviour of five species of Vicia from Argentina (V. macrograminea Burk., V. graminea SM., V. epetiolaris Burk., V. pampicola Burk. and V. nana Vog.). All the species have the same chromosome number and karyotype formula (2n = 14; 6 m + 4 st + 4 t). Each species, however, displays a characteristic number and position of the nucleolar organizer region (NOR) and different sizes of the respective satellites, confirmed by Ag-NOR banding. Moreover, significant differences were found in the total chromosome volume (TCV) and DNA content of the species. Positive correlations between DNA content and TCV, and between DNA content and type of life cycle were also found. TCV and DNA content are lower in V. nana (annual) and higher in V. macrograminea (biennial-perennial). The material displayed marked karyotypic orthoselection, with similar karyotypes in all studied species, even when the overall chromosome size varied. Evolutionary changes in DNA amount are proportional to the relative length of each chromosome arm, maintaining karyotypic uniformity. Significant differences were found between the meiotic behaviour of V. graminea and that of the other species. V. graminea has a lower frequency of ring bivalents and chiasmata per cell, and also has a lower interstitial chiasma frequency. In general, the results are congruent with the morphological data reported for these species.

Descripción: The haploid DNA content of Aeshna confusa (2n = 27, n = 13 + XO, male). A. bonariensis (2n = 26, n = 12 + neo-XY, male) and A. cornigera planaltica (2n = 16, n = 7 + neo-XY, male) has been determined (2.16 ± 0.16 pg, 1.81 ± 0.17 pg, and 2.08 ± 0.08 pg, respectively). Despite the differences in chromosome size and number, differences in DNA content between species are not significant. The karyotypic analysis of Aeshna species leads to the conclusion that fusions between autosomes or autosome and the sex chromosome, are the only chromosome rearrangement that occurred during evolution. In the species here studied, fusions have taken place with a minimal loss of DNA; however, other species of the genus show important differences in genome size, which cannot only be justified by fusion events.

Descripción: In this work we show that when an inviscid axisymmetric Rankine flow experiences a soft expansion, rotating Kelvin waves can be excited. Downstream of the region where the expansion occurs (the transition region) the resulting flow can be expressed as the addition of a Rankine and a Beltrami flow. The Beltrami constant is determined from the Rankine upstream flow, and the helix pitch of the n=1 mode results from the boundary conditions downstream. Finally, a discussion of the process leading to oscillatory flow and a conjecture about the topological background that sustains the Beltrami flow structure are offered. © 2008 American Institute of Physics.

Descripción: We study a k-essence field evolving linearly with the cosmic time and the atypical k-essence model on a homogeneous and isotropic flat 3-brane. We show that the k-field is driven by an inverse quadratic polynomial potential. The solutions represent expanding, contracting or bouncing universes with a finite time span and some of them end in a big crunch or a big rip. Besides, by selecting the extended tachyonic kinetic functions we analyze the high and low energy limits of our model, obtaining the nearly power law solution. We introduce a tachyon field with negative energy density and show that the universe evolves between two singularities. © 2010 IOP Publishing Ltd.

Descripción: Bracketed between 188-152 Ma, the Chon Aike Silicic Province developed in Patagonia covering an area of about 1,7 x 10 6 km 2 with volcanic products. An extensional tectonic regime that was active since at least the Jurassic-Cretaceous boundary accompanied this volcanic megaevent. Kinematic analyses focused in four selected localities (El Dorado - Monserrat, Norte de Cerro Vanguardia and El Fénix, in the Deseado region; and Lago Ghío, in the southern Patagonian Cordillera) allowed to define the main kinematic axes and to recognize two different kinematic events (a main and a secondary ones). Additionally these data certified the transtensional character of the Jurassic deformational event. When comparing directions of kinematic axes of all the selected localities, two kinematic domains: west and east could be discriminated. Whereas the eastern domain (El Dorado - Monserrat, Cerro Vanguardia north) shows ENE and NNW directions of extension for the main and the secondary kinematic events respectively, the western domain (El Fénix and Lago Ghío) indicate NE and NW directions of extension for the two events. The two kinematic events could be related or correspond to different volcanic facies. Considering the diachronism of the Chon Aike province (younger volcanic rocks westwards), the different kinematic fields could be linked to a large scale, non-coaxial deformation regime that controlled the emplacement of the Chon Aike volcanic province.

Descripción: A general kinematic wave model for flood propagation is presented in the form of a scalar conservation law. The corresponding flux function is convex or nearly convex for regular cross-sections of the river. In the presence of pronounced irregularities, however, convexity may fail. Qualitative consequences of the shape of the flux function for typical irregularities are discussed, particularly for rivers with flood plains and rivers trapped in canyons.

Descripción: We introduce and study so-called self-indexed graphs. These are (oriented) finite graphs endowed with a map from the set of edges to the set of vertices. Such graphs naturally arise from classical knot and link diagrams. In fact, the graphs resulting from link diagrams have an additional structure, an integral flow. We call a self-indexed graph with integral flow a comte. The analogy with links allows us to define transformations of comtes generalizing the Reidemeister moves on link diagrams. We show that many invariants of links can be generalized to comtes, most notably the linking number, the Alexander polynomials, the link group, etc. We also discuss finite type invariants and quandle cocycle invariants of comtes.

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