Casas confortables con mínimo uso de energía: Estudio de casos prácticos para Argentina y Chile
Gonzalez, Alejandro Daniel
Este libro trata sobre el uso de la energía y la eficiencia energética en edificios de dos países del Cono Sur, Argentina y Chile. Se explica cómo, en forma simple y económica, se puede bajar a la mitad el consumo energético de los edificios, aumentando al mismo tiempo el confort interior. El libro está escrito para quienes no tienen formación en física o ingeniería. En diversas ramas de ciencias sociales y política, y en funcionarios ligados a energía y medio ambiente puede ser útil incorporar elementos técnicos básicos para cuantificar el problema energético. Uno de los objetivos de este libro es complementar un vacío educativo en información interdisciplinaria. Los principales problemas energéticos actuales ya no pertenecen a la física, la química o la ingeniería, sino a la administración, a la política y a las ciencias sociales. Pienso que estas profesiones pueden desarrollar mejor su potencial si cuentan con conocimientos técnicos sobre los recursos y cómo cuantificarlos. Por ejemplo, el precio internacional del gas natural se da en dólares por cada millón de BTU; quien quiera conectar esto con aspectos sociales y económicos del uso de energía, ¿sabe que un millón de BTU es igual a 27 m3 de gas natural, o a 21 kg de gas licuado de petróleo, y que esta cantidad provee cerca de 270 kWh de energía neta? En todo caso, ¿qué es BTU? Se explica en el capítulo 3. Pienso que en la enseñanza media y en los primeros años de la universidad los conceptos y casos que aquí se detallan pueden ser un complemento interesante de la bibliografía habitual, aportando diversos elementos de discusión y de ejercitación práctica. El libro enfoca en lo práctico, y esto puede aportar ejemplos y casos a cursos de física en la enseñanza media y primeros años universitarios. Este libro puede ser también útil a los arquitectos para actualizar su formación en física y energía. Por otro lado, provocará también sorpresas en físicos e ingenieros que no habían asociado sus conocimientos básicos a los problemas cotidianos del uso eficiente de recursos energéticos.
Factores de riesgo laboral en bioterios
Turino, Ludmila Noelia; Latorre Rapela, María Gabriela de Los Milagros
En el presente capítulo se hará mención a los factores de riesgo más importantes en los bioterios y los niveles de seguridad requeridos cuando se manipulan microorganismos de diversos niveles de seguridad biológica.
Menopause, Aging, Pelvic Organ Prolapse, and Dysfunction
Pisaneschi, Silvia; Palla, Giulia; Spina, Stefania; Bernacchi, Guja; Cecchi, Elena; Di Bello, Silvia; Montt Guevara, Maria Magdalena; Campelo, Adrián Esteban; Simoncini, Tommaso
The female pelvic floor is a complex functional unit involved in many undertakings. Pelvic floor dysfunction affects micturition, defecation, and sexual activity. Evolutionary adaptation, such as the acquisition of the upright standing position, walking, and delivery of fetuses with larger head diameters, made the fascial and the muscle support of the pelvic floor more vulnerable, predisposing women to pelvic organ prolapse and incontinence. In addition, the female pelvic floor (differently than in males) undergoes a number of adaptive changes related to life and endocrine events. Many of these clinical manifestations become apparent after menopause and aging in women. This chapter summarizes the key aspects of the pathophysiology and the clinics of the changes of the pelvic floor in women, in particular focusing on the association between endocrine changes of aging women and urinary problems and bowel dysfunctions.
Hongos y bacterias del suelo con capacidades biofertilizantes y biocontroladoras para su aplicación con fines biotecnológicos
Consolo, Verónica Fabiana; Thougnon Islas, Andrea Julieta; Hernández Guijarro, Keren; Covacevich, Fernanda
La provincia de Buenos Aires representa un área agrícola por excelencia en nuestro país debido a sus características edáficas y climáticas, adecuadas para la producción de cultivos. Sin embargo, como consecuencia de la explotación intensiva del suelo en las últimas décadas con permanente extracción de nutrientes, se han evidenciado pérdidas de materia orgánica con los consecuentes desbalances de nutrientes claves para la producción agropecuaria. Por esta razón, la fertilización (destinada a la reposición de nutrientes) y la utilización de la siembra directa (para minimizar las perdidas de materia orgánica) se han implementado de manera generalizada en nuestro país. Sin embargo, la mayor incidencia de enfermedades fúngicas (asociada a la siembra directa) ha generado mayor dependencia en el uso de pesticidas. Tanto la aplicación de fertilizantes como de pesticidas puede afectar negativamente las poblaciones microbianas del suelo que podrían a su vez contribuir a reducir el uso de agroquímicos y fertilizantes sintéticos. Sin embargo, estos aspectos no siempre son considerados al planificar emprendimientos productivos. Nuestro grupo de trabajo tiene como blanco de estudio los hongos formadores de micorrizas arbusculares (HMA; reconocidos por incrementar la nutrición vegetal, la capacidad de recuperación de las plantas frente a estrés y por incrementar la estabilidad de los agregados del suelo), hongos del género Trichoderma (reconocidos como agentes de control biológico contra hongos patógenos, solubilizadores de fósforo (P) y productores de factores de promoción del crecimiento vegetal) y microorganismos solubilizadores de P. Nuestra línea de investigación tiene como objetivos: a) aislar, multiplicar y caracterizar HMA, Trichoderma y solubilizadores de P nativos de la Provincia de Buenos Aires; b) testear la potencialidad de los grupos seleccionados como potenciales promotores de crecimiento (biofertilizantes y biocontroladores) de cultivos de importancia agrícola; y c) formular biofertilizantes compuestos de consorcios microbianos nativos de la Provincia de Buenos Aires. En el presente se están ensayando diferentes combinaciones de consorcios microbianos con el objetivo de ser utilizados como herramientas dentro de programas de manejo integrado de nutrición y control de enfermedades fúngicas en cultivos de importancia agronómica. Además, se está generando una colección de microorganismos nativos de la Provincia de Buenos Aires que han evidenciado, bajo condiciones controladas, capacidades promotoras de crecimiento en plantas de maíz, trigo, cebada y tomate. Dichos microorganismos están siendo caracterizados en su actividad y diversidad genética, con el objetivo de ser utilizados como bioinoculantes.
Tandil (Provincia de Buenos Aires): Segregación espacial a través de los niveles educativos del jefe de hogar
Linares, Santiago; Velázquez, Guillermo Ángel
La segregación socioespacial, también denominada segregación social del espacio urbano, segregación residencial o simplemente segregación urbana, es un concepto que hace referencia a la existencia de diferencias o desigualdades sociales dentro de un colectivo urbano y al agrupamiento de los sujetos según atributos específicos (socioeconómicos, culturales, raciales, etc.) en conglomerados urbanos con tendencia a la homogeneización en su interior y a la reducción de las interacciones con el resto de los grupos…
Tallas medievales en museos argentinos: una imagen de la Virgen y el Niño en el Museo Nacional de Bellas Artes; Medieval wood carvings in Argentine museums: an image of Mary and the Child in the National Museum of Fine Arts
Montemurro, Marialaura
Este artículo se propone avanzar en el estudio de una escultura en madera de la Virgen y el Niño, de principios del siglo XIV, procedente de la provincia española de Álava y que se conserva actualmente en el Museo Nacional de Bellas Artes de Buenos Aires Argentina. Con este objetivo se considerará tanto su historia reciente como su iconografía, estilo y técnica con el propósito final de contribuir al conocimiento y difusión del patrimonio artístico medieval en museos de la Argentina. Para ello se buscará indagar sobre la procedencia de la imagen, dando cuenta de sus antiguos propietarios hasta su ingreso en el ámbito público, en el cual se exhibe actualmente. A continuación se profundizará el estudio, analizando la evolución histórica de ciertos aspectos de su iconografía, y así se podrá situarla dentro del grupo estilístico de esculturas que la especialista Clara Fernandez-Ladreda definió como vasconavarro-riojano; This paper offers an insight into an early 14th. Century wooden sculpture of Virgin Mary and the Child crafted in the Nortwestern Spanish province of Alava and preserved in the Museo Nacional de Bellas Artes, Argentina, by adressing both its recent history as well as its iconography, style and technique, towards a better and wider knowledge of the Medieval artistic patrimony in Argentine public museums. To this end, the author shall first search into the provenance of this work and its transference to the public collection that now houses it, and then look at some peculiar aspects of its iconography to place this sculpture into its precise artistic framework, which has been defined by Clara Fernandez-Ladreda as the "Basque-Navarre-Riojan" Gothic style.
New age constraints for the Salamanca Formation and lower Río Chico Group in the western San Jorge Basin, Patagonia, Argentina: Implications for cretaceous-paleogene extinction recovery and land mammal age correlations
Clyde, William C.; Wilf, Peter; Iglesias, Ari; Slingerland, Rudy L.; Barnum, Timothy; Bijl, Peter K.; Bralower, Timothy J.; Brinkhuis, Henk; Comer, Emily E.; Huber, Brian T.; Ibañez Mejia, Mauricio; Jicha, Brian R.; Krause, Javier Marcelo; Schuet, Jonathan D.; Singer, Bradley S.; Raigemborn, María Sol; Schmitz, Mark D.; Sluijs, Appy; Zamaloa, María del Carmen
The Salamanca Formation of the San Jorge Basin (Patagonia, Argentina) preserves critical records of Southern Hemisphere Paleocene biotas, but its age remains poorly resolved, with estimates ranging from Late Cretaceous to middle Paleocene. We report a multi-disciplinary geochronologic study of the Salamanca Formation and overlying Río Chico Group in the western part of the basin. New constraints include (1) an 40Ar/39Ar age determination of 67.31 ± 0.55 Ma from a basalt flow underlying the Salamanca Formation, (2) micropaleontological results indicating an early Danian age for the base of the Salamanca Formation, (3) laser ablation HR-MC-ICP-MS (high resolutionmulti collector-inductively coupled plasmamass spectrometry) U-Pb ages and a highresolution TIMS (thermal ionization mass spectrometry) age of 61.984 ± 0.041(0.074) [0.100] Ma for zircons from volcanic ash beds in the Peñas Coloradas Formation (Río Chico Group), and (4) paleomagnetic results indicating that the Salamanca Formation in this area is entirely of normal polarity, with reversals occurring in the Río Chico Group. Placing these new age constraints in the context of a sequence stratigraphic model for the basin, we correlate the Salamanca Formation in the study area to Chrons C29n and C28n, with the Banco Negro Inferior (BNI), a mature widespread fossiliferous paleosol unit at the top of the Salamanca Formation, corresponding to the top of Chron C28n. The diverse paleo botanical assemblages from this area are here assigned to C28n (64.67- 63.49 Ma), ̃2-3 million years older than previously thought, adding to growing evidence for rapid Southern Hemisphere floral recovery after the Cretaceous-Paleogene extinction. Important Peligran and "Carodnia" zone vertebrate fossil assemblages from coastal BNI and Peñas Coloradas exposures are likely older than previously thought and correlate to the early Torrejonian and early Tiffanian North American Land Mammal Ages, respectively.
Paneth cell identification in the small intestine of guinea pig offsprings (Cavia porcellus)
Vásquez Cachay, María Elith; Pebe, Erika; Rodríguez Gutiérrez, José Luis; Mejía, Boris Lira; Falcón Pérez, Néstor; Zanuzzi, Carolina Natalia; Barbeito, Claudio Gustavo
The aim of this study was to determine the presence, number, and morphometrical characteristics of Paneth cells (PC) in the small intestine of guinea pigs during lactation. We used 48 pups from 0 to 15 days old. Samples from small intestine were fixed in 10% buffered formaldehyde (pH 7.4) and processed for histological and morphometrical studies using hematoxylin and eosin (HE), Phloxine tartrazine or Masson's Trichome staining, or immunohistochemistry for lysozyme. PC were morphologically identified at day 2 using Masson's Trichome or Phloxine tartrazine stainings, and at day 4 using HE, whereas using immunohistochemistry they were recognized from birth. Morphometrical differences were found between the intestinal sections at each age studied, and within each section during the first weeks of life. In all developmental stage, the highest number of PC was observed in the duodenum of 13 days old guinea pigs. Our results confirm the presence of PC in the small intestine of guinea pigs from birth.
Las implicancias arqueológicas del Diario de Pero Lopes de Sousa (1531) durante su viaje al Río de la Plata y al Delta Inferior del río Paraná; The archaeological implications of the Diary of Pero Lopes de Souza (1531) during his trip to the La Plata River
Politis, Gustavo Gabriel
En este trabajo se estudia el diario del explorador portugués Pero Lopes de Souza en 1531 al Río de la Plata y al delta Inferior del río Paraná desde una perspectiva histórica y arqueológica. Este relato es el único documento de la época escrito en tiempo real por un testigo directo de los acontecimientos que describe y por lo tanto es una fuente de calidad superlativa para conocer los primeros momentos de la exploración europea en el Río de la Plata y para abordar el estudio de los indígenas que habitaban el área a principios del siglo XVI. En este artículo se resumirán y discutirán las observaciones de Lopes de Sousa en el contexto de la historia del Río de La Plata en la primera mitad del siglo XVI y de las investigaciones arqueológicas recientes.; In this paper the diary of the Portuguese explorer Pero Lopes de Sousa to the La Plata River and to the Lower Delta of the Paraná River is analyzed from a historical and archaeological perspective. This narrative is the only document written in real time from a direct witness of the accounts he described. Therefore it is a unique high-quality source to know about the early times of the European Conquest to the La Plata River and to approach the study of the indigenous people of the area at the beginning of the XVI Century. In this article, the observations and comments from Lopes de Souza are summarized and analyzed within the context of the history of the first half of the XVI Century and in the light of the recent archaeological investigations.
Tecnología ósea en el oeste de la región pampeana: identificación de las técnicas de manufactura a partir de evidencias arqueológicas y experimentales; Bone technology in the western pampean region: identifying manufacturing techniques from archaeological and experimental evidence
Alvarez, María Clara
En este trabajo se presentan los resultados del estudio de huesos vinculados con la tecnología, provenientes del sitio arqueológico Laguna de los Pampas (LLP), localizado en la subregión Pampa Húmeda de Argentina. Los especímenes fueron estudiados aplicando el enfoque tecnológico al análisis de los instrumentos óseos por secuencias de operaciones, en el sentido de cadenas operativas de la manufactura. El objetivo fue identificar el proceso de manufactura de las formas base en el sitio LLP, a través del estudio de los restos arqueológicos, así como de trabajos experimentales. Se reconstruyó la cadena operativa teórica para la manufactura de las formas base en tibias y metapodios de guanaco. En general, los resultados indican que los instrumentos óseos habrían sido confeccionados en el sitio para el caso de la tibia y que este elemento fue seleccionado como núcleo para la obtención de astillas.; This paper presents the results of a study of bone specimens related to bone technology from the Laguna de los Pampas (LLP) archaeological site, located in the Humid Pampean subregion in Argentina. The bone tools were analyzed using a technological approach examining sequences of operations, that is, chaìnes opératoires of manufacture. The objective was to identify the manufacturing process of bone tools at the LLP site by analyzing the archaeological remains and through experimental studies. The hypothetical sequences for manufacturing bone tools were reconstructed using the tibia and metapodial bones of guanaco, a native camelid. The results indicate that tibia bone tools were crafted at the LLP site, and that this particular bone was favored as a core for the production of shaft splinters.
Two-phase flow instabilities: A review
Ruspini, Leonardo; Marcel, Christian Pablo; Clausse, Alejandro
An updated review of two-phase flow instabilities including experimental and analytical results regarding density-wave and pressure-drop oscillations, as well as Ledinegg excursions, is presented. The latest findings about the main mechanisms involved in the occurrence of these phenomena are introduced. This work complements previous reviews, putting all two-phase flow instabilities in the same context and updating the information including coherently the data accumulated in recent years. The review is concluded with a discussion of the current research state and recommendations for future works.
Electrode/Electrolyte Interphase Studies of Ceria Based Electrolytes for IT-SOFCs
Baque, Laura Cecilia; Padmasree, Karinjilottu; Fuentes, Antonio F.; Serquis, Adriana Cristina; Soldati, Analía Leticia
Solid oxide fuel cells (SOFCs) require high operation temperatures (up to 800°C) in order to allow oxygen ion conduction through the ceramic electrolyte. Lowering SOFC operation temperature implies enhancing the transport and electrochemical properties of both electrolyte and cathode. In this work, the electrochemical performance of nanostructured La0.4Sr0.6Co0.8Fe0.2O3-d (LSCFO)/Ce0.8Gd0.2O2-d(CGO)/LSCFO and LSCFO/Ce0.8Nd0.2O2-d (CNO)/LSCFO symmetrical cells was investigated. The bulk conductivity is similar for both electrolytes, while the grain boundary and total conductivities is higher for the CGO electrolyte. Nevertheless, CGO electrolyte exhibits large pores that compromise its mechanical properties. In addition, cathode performance degrades in LSCFO/CGO/LSCFO cells.
Direct recoil spectroscopy of adsorbed atoms and self-assembled monolayers on Cu(001)
Salazar Alarcón, Leonardo; Jia, J.; Carrera, Alvaro Daniel; Esaulov, V. A.; Ascolani, Hugo del Lujan; Gayone, Julio Esteban; Sánchez, Esteban Alejandro; Grizzi, Oscar
We present results of adsorption experiments of Sn and 1,4-benzenedimethanethiol (BDMT) on Cu(001), which illustrate the capabilities of a new setup specifically designed to perform surface studies by Direct Recoil Spectroscopy (DRS). The system consists of three UHV chambers connected in series with a 1–100 keV ion accelerator. In the main UHV chamber the DRS technique is combined with other more standard techniques such as Auger and Energy Loss Electron Spectroscopy, and Low Energy Electron Diffraction. The capabilities of the instrument are exemplified by two adsorption studies on the (001) face of Cu. First we describe measurements for 0.5 monolayer of Sn adsorbed on Cu that are in agreement with the crystallographic symmetry (3√2x√2) R45° seen by LEED and the appearance of Cu vacancies along the [100] direction. Then we present a study of self-assembling of 1,4-benzenedimethanethiol (BDMT) on Cu(001) from the vapour phase. For this system we show that it is possible to form a standing-up phase at large exposures, of the order of 106 L, and discuss its stability with temperature. We also discuss a S enrichment effect induced during the first adsorption stages of BDMT.
On the relation between Seyfert 2 accretion rate and environment at z < 0.1
Coldwell Lloveras, Georgina Vanesa; Gurovich, Sebastian; Diaz Tello, Jorge Andres; Söchting, Ilona K.; Garcia Lambas, Diego Rodolfo
We analyse different properties of the small-scale environment of Seyfert 2 for two samples selected according to the accretion rate parameter, R, from the Sloan Digital Sky Survey, Data Release 7 survey. We compare the results with two control samples of non-active galaxies that cover the same redshift range, luminosity, colours, morphology, age and stellar mass content. Our study shows that both high and low accretion rate subsamples reside in bluer and lower density environments than the control samples. However, we find that this difference is at least two times stronger for the low accretion rate Seyferts. In the vicinity of Seyfert 2, red galaxies have systematically lower values of stellar mass as compared with corresponding control samples. The lower values of stellar mass for red neighbours is more significant at higher density environments and it is more evident for low accretion rate Seyfert. We also find that this effect is independent of the host's stellar mass. Our results are consistent with a scenario where active galactic nucleus occurrence is higher in lower/medium density environments with a higher merger rate and a lack of a dense intergalactic medium (that can strip gas from these systems) that provide suitable conditions for the central black hole feeding. We find this particularly evident for the low accretion rate Seyferts that could compensate through the intergalactic medium the lack of gas of their hosts.
Mercado de trabajo y trayectorias laborales en contextos de pobreza. Desafíos para pensar la política social; Labour Market and Career Paths in Contexts of Poverty. Challenges for Social Policy
Freyre, Maria Laura
El presente artículo analiza las principales características del mercado de trabajo en Argentina desde las recientes transformaciones neoliberales y específicamente tras la caída del régimen de Convertibilidad con el objetivo de considerar sus efectos diferenciales sobre los hogares de menores recursos. A partir de este diagnóstico se propone reflexionar sobre los desafíos que suponen las características de la fuerza de trabajo presente en las familias pobres, para el diseño e implementación de la política social de empleo y sostenimiento de ingresos.; Recent research on the labor market in Argentina highlights the positive effects of the recovery phase and initiated economic growth from 2003 to 2009. The specific literature on the subject point emphasizes the context of overall economic recovery after the crisis and devaluation of 2001-2002, both in terms of growth in economic activity, measured from GDP growth, as the conditions in the labor market due to the sustained recovery in employment levels and progressive restructuring of labor income. In this phase of economic expansion, there was a reduction in labor costs. This paper analyzes the main features of the labor market in Argentina since the recent neoliberal transformations and specifically after the collapse of the Convertibility regime in order to consider their differential effects on low-income households. From this analysis it intends to reflect on the challenges of the features of the present workforce in poor families, for the design and implementation of social policy and employment income support.
Assessing the reliability of friends-of-friends groups on the future Javalambre Physics of the Accelerating Universe Astrophysical Survey
Zandivarez, Arnaldo Ariel; Diaz, Maria Eugenia; Oliveira, Claudia Mendes de; Ascaso, B.; Benítez, N.; Dupke, R.; Sodré, L.; Irwin, J.
Aims: We have performed a detailed analysis of the ability of the friends-of-friends algorithm to identify real galaxy systems in deep surveys such as the future Javalambre Physics of the Accelerating Universe Astrophysical Survey. Our approach was twofold: assessing the reliability of the algorithm in real and in redshift space. In the latter, our intention was also to determine the degree of accuracy that could be achieved when using spectroscopic or photometric-redshift determinations as a distance indicator. Methods: We built a light-cone mock catalogue using synthetic galaxies constructed from the Millennium Run Simulation I plus a semi-analytical model of galaxy formation. We explored different ways to define the proper linking length parameters of the algorithm to identify the best-suited galaxy groups in each case. Results: We found that when one identifies systems in redshift space using spectroscopic information, the linking lengths should take into account the variation of the luminosity function with redshift as well as the linear redshift dependence of the radial fiducial velocity in the line-of-sight direction. When we tested the purity and completeness of the group samples, we found that the best resulting group sample reaches values of ~40% and ~70% of systems with high levels of purity and completeness, when spectroscopic information was used. To identify systems using photometric redshifts, we adopted a probabilistic approach to link galaxies in the line-of-sight direction. Our result suggests that it is possible to identify a sample of groups with fewer than ~40% false identifications at the same time as we recover around 60% of the true groups. Conclusions: This modified version of the algorithm can be applied to deep surveys provided that the linking lengths are selected appropriately for the science to be made with the data.
Central α- and β-thujone: Similar anxiogenic-like effects and differential modulation on GABAA receptors in neonatal chicks
Rivera, E. M.; Cid, Mariana Paula; Zunino, María Paula; Baiardi, Gustavo Carlos; Salvatierra, Nancy Alicia
The convulsant effects of α-thujone are attributed to inhibitory actions on the GABAA receptor. We investigated, for the first time, the effects of α-thujone or β-thujone administrated centrally on the fear/anxiety behaviour of 3-day-old chicks in an Open Field and their modulation on the GABAA receptor. Higher doses were convulsant by eliciting a toxic and excitatory action, with the results showing that a dose of 78 nmol of either of the two diastereoisomers had an anxiogenic-like effect observed as an increased latency to ambulate and a reduced locomotor activity in an Open Field. Nevertheless, only the central administration of α-thujone reversed the increase induced by acute stress in the flunitrazepam-sensitive GABAA receptor recruitment. These findings demonstrated that α-thujone, when intracerebroventricularly administered, suppressed the GABAA receptor recruitment induced by acute stress, maybe due to α-thujone blocking the benzodiazepine binding site or another site of the GABAA complex. However, it should not be discarded that acute stress associated with novelty may have induced the recruitment of a subpopulation of GABAA receptors more sensitive to α-thujone than to the constitutive receptors, or that this monoterpene could have inhibited any protein or enzyme trafficking that modulated the phosphorylation of the receptor involved in the turnover of GABAA receptor. β-Thujone showed behavioural effects similar to its diastereoisomer α-thujone. However, its action mechanism may have been mediated by other neurotransmitter systems, such as the serotonergic one or by a different biological effectiveness due to a distinct stereochemistry at the specific site of the GABAA receptor.
β3-Chimaerin, a novel member of the chimaerin Rac-GAP family
Zubeldia Brenner, Lautaro; Gutierrez Uzquiza, Alvaro; Barrio Real, Laura; Wang, Hongbin; Kazanietz, Marcelo Gabriel; Coluccio Leskow, Federico
Chimaerins are a family of diacylglycerol- and phorbol ester-regulated GTPase activating proteins (GAPs) for the small G-protein Rac. Extensive evidence indicates that these proteins play important roles in development, axon guidance, metabolism, cell motility, and T cell activation. Four isoforms have been reported to-date, which are products of CHN1 (α1- and α2-chimaerins) and CHN2 (β1- and β2-chimaerins) genes. Although these gene products are assumed to be generated by alternative splicing, bioinformatics analysis of the CHN2 gene revealed that β1- and β2-chimaerins are the products of alternative transcription start sites (TSSs) in different promoter regions. Furthermore, we found an additional TSS in CHN2 gene that leads to a novel product, which we named β3-chimaerin. Expression profile analysis revealed predominantly low levels for the β3-chimaerin transcript, with higher expression levels in epididymis, plasma blood leucocytes, spleen, thymus, as well as various areas of the brain. In addition to the prototypical SH2, C1, and Rac-GAP domains, β3-chimaerin has a unique N-terminal domain. Studies in cells established that β3-chimaerin has Rac-GAP activity and is responsive to phorbol esters. The enhanced responsiveness of β3-chimaerin for phorbol ester-induced translocation relative to β2-chimaerin suggests differential ligand accessibility to the C1 domain.
Simulations of cold nuclear matter at sub-saturation densities
Giménez Molinelli, Pedro Agustín; Nichols, Juan Ignacio; Lopez, J. A.; Dorso, Claudio Oscar
Ideal nuclear matter is expected to undergo a first order phase transition at the thermodynamic limit. At such phase transitions the size of density fluctuations (bubbles or droplets) scale with the size of the system. This means that simulations of nuclear matter at sub-saturation densities will inexorably suffer from what is vaguely referred to as “finite size effects”. It is usually thought that these finite size effects can be diminished by imposing periodic boundary conditions and making the system large enough, but as we show in this work, that is actually not the case at sub-saturation densities. In this paper we analyze the equilibrium configurations of molecular dynamics simulations of a classical model for symmetric ideal (uncharged) nuclear matter at sub-saturation densities and low temperatures, where phase coexistence is expected at the thermodynamic limit. We show that the most stable configurations in this density range are almost completely determined by artificial aspects of the simulations (i.e. boundary conditions) and can be predicted analytically by surface minimization. This result is very general and is shown to hold true for several well known semi-classical models of nuclear interaction and even for a simple Lennard-Jones potential. Also, in the limit of very large systems, when “small size” effects can be neglected, those equilibrium configurations seem to be restricted to a few structures reminiscent to the “Pasta Phases” expected in Neutron Star matter, but arising from a completely different origin: In Neutron Star matter, the non-homogeneous structures arise from a competition between nuclear and Coulomb interactions while for ideal nuclear matter they emerge from finite (yet not “small”) size effects. The role of periodic boundary conditions and finite size effects in Neutron Star matter simulations are reexamined.
