Descripción: A recently reported symmetry breaking of density profiles of fluid argon confined by two parallel solid walls of carbon dioxide is studied. The calculations are performed in the framework of a nonlocal density functional theory. It is shown that the existence of such asymmetrical solutions is restricted to a special choice for the adsorption potential, where the attraction of the solid-fluid interaction is reduced by the introduction of a hard-wall repulsion. The behavior as a function of the slit's width is also discussed. All the results are placed in the context of the current knowledge on this matter. © 2008 American Institute of Physics.

Descripción: The role of short-chain fatty acids in the host-seeking behaviour of Triatoma infestans larvae was investigated using a locomotion compensator. Several short-chain fatty acids were tested alone over a wide range of doses, or in combination with L-lactic acid (L-LA; 100 μg). Bugs showed no attractive response to single carboxylic acids, but when L-LA was added to airstreams carrying specific intensities of either propionic (C3; 100 μg), butyric (C4; 1 μg) or valeric acid (C5; 1 μg), these mixtures elicited an attractive response, evincing a synergistic effect. No orientation response was observed when caproic acid (C6) was offered with L-LA at the doses tested. Two blends were created: (1) C3, C4 and C5 combined at the effective doses when added with L-LA [C3C4C5 (1)], and (2) C3, C4 and C5 combined at a third of those intensities [C3C4C5 (2)]. Both blends were tested alone, with L-LA (100 μg), with a sub-threshold concentration of CO2 (300 p.p.m. above the ambient level), and combined with both compounds together. Oriented responses of bugs were only observed with the blend (2) added with L-LA and with the combination of this lure with CO2. This last combination evoked a behavioural response similar in intensity to that induced by a live mouse. © Oxford University Press 2004; all rights reserved.

Descripción: Both the biomass of autotrophic dinoflagellates and its contribution to total chlorophyll were found to increase significantly with seawater temperature and the level of stratification in southern Patagonian waters during spring and winter. The highest peak of biomass corresponded to a single species, Prorocentrum minimum (Pavillard) Schiller, and was detected in middle shelf waters, coinciding with the primary productivity and CO 2 uptake maxima reported for the area under spring conditions. © The Author 2011. Published by Oxford University Press. All rights reserved.

Descripción: Asr (for ABA, stress, ripening) genes are exclusively found in the genomes of higher plants, and the encoded proteins have been found localized both to the nucleus and cytoplasm. However, before the mechanisms underlying the activity of ASR proteins can be determined, the role of these proteins in planta should be deciphered. Results from this study suggest that ASR is positioned within the signaling cascade of interactions among glucose, abscisic acid, and gibberellins. Tobacco (Nicotiana tabacum) transgenic lines with reduced levels of ASR protein showed impaired glucose metabolism and altered abscisic acid and gibberellin levels. These changes were associated with dwarfism, reduced carbon dioxide assimilation, and accelerated leaf senescence as a consequence of a fine regulation exerted by ASR to the glucose metabolism. This regulation resulted in an impact on glucose signaling mediated by Hexokinase1 and Snf1-related kinase, which would subsequently have been responsible for photosynthesis, leaf senescence, and hormone level alterations. It thus can be postulated that ASR is not only involved in the control of hexose uptake in heterotrophic organs, as we have previously reported, but also in the control of carbon fixation by the leaves mediated by a similar mechanism. © 2013 American Society of Plant Biologists. All Rights Reserved.

Descripción: The influence of the plankton community structure on carbon dynamics was studied in the surface waters of the Argentinean continental shelf (SW Atlantic Ocean) in summer and fall 2002, 2003 and 2004, The horizontal changes in plankton community respiration (R), net community production (NCP) and gross primary production (GPP) were (1) compared with the difference in the partial pressure of CO2 (pCO2) between the sea surface and the atmosphere (ΔpCO2), (2) compared with oxygen saturation and (3) related to the microscopic phytoplankton assemblages, This area, which has recently been shown to be a CO2 sink, had an average surface oxygen saturation of 108.1%, indicating that net photosynthesis could have played a dominant role in the CO2 dynamics. At most stations, the production:respiration (GPP:R) ratio was greater than 1, indicating that planktonic communities were autotrophic; the average GPP:R ratio for the whole study was 2.99, Phytoplankton biomass (chlorophyll a) and NCP showed an inverse relationship with ΔpCO2 and a direct relationship with %O 2 saturation when phytoplankton assemblages were dominated by diatoms (30% of the stations), This was not the case when small (≤5 μm) flagellates were the most abundant organisms, Although NCP was mostly positive for both groups of stations (i.e. diatom-dominated or small flagellate- dominated), other physical and biological processes are thought to modify the CO2 dynamics when small flagellates are the prevailing phytoplankton group. © Inter-Research 2007.

Descripción: The thermohaline structure across the tidal fronts of the continental shelf off Patagonia is analyzed using historical and recent summer hydrographic sections. The near-summer tidal front location is determined on the basis of the magnitude of vertical stratification of the water column as measured by the Simpson parameter. Sea surface and air CO2 partial pressures based on data from eleven transects collected in summer and fall from 2000 to 2004 are used to estimate CO2 fluxes over the shelf. The near-shore waters are a source of CO2 to the atmosphere while the midshelf region is a CO2 sink. The transition between source and sink regions closely follows the location of tidal fronts, suggesting a link between vertical stratification of the water column and the regional CO2 balance. The highest surface values of Chl a are associated with the strongest CO2 sinks. The colocation of lowest CO2 partial pressure (pCO2) and highest Chl a suggests that phytoplankton blooms on the stratified side of the fronts draw the ocean's CO2 to very low levels. The mean shelf sea-air difference in pCO2 (ΔpCO2) is -24 μatm and rises to -29 μatm if the shelf break front is included. Peaks in ΔpCO2 of -110 μatm, among the highest observed in the global ocean, are observed. The estimated summer mean CO2 flux over the shelf is -4.4 mmol m-2 d-1 and rises to -5.7 mmol m-2 d-1 when the shelf break area is taken into account. Thus, during the warm season the shelf off Patagonia is a significant atmospheric CO2 sink. Copyright 2005 by the American Geophysical Union.