Middle Darriwilian conodont zones in the uppermost San Juan limestone and the lower member of the Las Aguaditas formation, central Precordillera of San Juan, Argentina

The geological province of Precordillera is located in western Argentina. It extends 450 km meridionally and 110 km from east to west (Fig. 1) (Furque and Cuerda, 1979). The Lower Paleozoic stratigraphy is characterized by a thick succession of Cambro-Ordovician limestones, which were deposited in platform environments and interdigitate with clastic slope deposits toward the west (Keller et al., 1993; Astini, 1995).Fil: Feltes, Nicolás Alexis. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Museo de Paleontología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Albanesi, Guillermo Luis. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Museo de Paleontología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Bergström, S. M.. Ohio State University; Estados Unido

Macroscopic polarization and band offsets at nitride heterojunctions

Ab initio electronic structure studies of prototypical polar interfaces of wurtzite III-V nitrides show that large uniform electric fields exist in epitaxial nitride overlayers, due to the discontinuity across the interface of the macroscopic polarization of the constituent materials. Polarization fields forbid a standard evaluation of band offsets and formation energies: using new techniques, we find a large forward-backward asymmetry of the offset (0.2 eV for AlN/GaN (0001), 0.85 eV for GaN/AlN (0001)), and tiny interface formation energies.Comment: RevTeX 4 pages, 2 figure

Ectomycorrhizal Fungi as Biofertilizers in Forestry

Ectomycorrhizal (ECM) fungi play a fundamental role in the nutrient cycle in terrestrial ecosystems, especially in forest systems. In this chapter, the value of ECM fungi is reviewed from a global framework, not only to increase the production of edible fruit bodies and biomass of plants but also for the regular practices of reforestation and restoration of ecosystems, with implicit applications in biofertilization, bioremediation, and control of soil pathogens. Ecological functions of the ECM fungi are briefly reviewed. The direct implications of the ECM fungi in forestry are described. To do so, its role as a biotechnological tool in forest nursery production is briefly analyzed, as well as the role of mycorrhizal helper bacteria (MHB). Subsequently, the direct role as biofertilizers of the ECM fungi in forest management is discussed: reforestation, plantation management, and ecosystem restoration. The importance of ECM fungi to increase the tolerance of plants against biotic or abiotic stresses is analyzed

Bioestratigrafía de conodontes y correlación global del Darriwiliano medio-Sandbiano inferior (Ordovícico) Formación Las Aguaditas, precordillera de San Juan, Argentina

En la Formación Las Aguaditas, en su sección tipo en la precordillera Argentina, se registraron conodontes del Darriwiliano medio al Sandbiano bajo. Se recuperaron un total de 9.974 especímenes de 46 muestras carbonáticas; estos representan 68 especies pertenecientes a 38 géneros. Se llevó a cabo un estudio bioestratigráfico para verificar la edad del intervalo que incluye el contacto entra las formaciones San Juan y Las Aguaditas. La presencia de taxones guía indican una edad darriwiliana media para este intervalo. Las siguientes biozonas fueron determinadas en el área de estudio: Zona de Lenodusvariabilis, con las subzonas de Periodongladysae y Paroistodushorridus, correspondientes al esquema establecido para la precordillera; las zonas de L.v ariabilis, Yangtzeplacognathuscrassusy la deE oplacognathuspseudoplanuscon la subzonas de Microzarkodinahagetiana y M.ozarkodella, y la Zona de Pygodusanserinus, según el esquema Báltico; la Zona de Periodonmacrodentatus, con las subzonas de Histiodellasinuosa,H.holodentatayH. cf. holodentata, y la Zona de P.zgierzensis con la subzona de H.kristinae que se correlaciona con el esquema norteamericano. Se reconoció una discontinuidad estratigráfica entre los miembros inferior y medio de la Formación Las Aguaditas. Esta comprende las zonas de Eoplacognathussuecicus y Pygodus serra, y la subzona inferior de la Zona de Pygodusanserinus. La variación en la diversidad de conodontes en la sección de estudio se corresponde con patrones de somerización y profundización, que a su vez son congruentes con los cambios en la litología. Luego de analizar la composición taxonómica de las muestras se reconocieron, de manera cuantitativa, tres asociaciones de conodontes: a) Asociación diversa de conodontes, b) Asociación de baja diversidad de conodontes, y c) Asociación de conodontes en fase de recuperación. Se propone aplicar para la precordillera central el esquema de biozonación de América del Norte debido a la afinidad de los taxones guía documentada, brindando una correlación intercontinental más precisa para el Ordovícico Medio a nivel global.Middle Darriwilian to lower Sandbian conodonts were recorded from the Las Aguaditas Formation at its type section in the Argentine Precordillera. A total of 9,974 conodont specimens were recovered from 46 carbonate samples, which represent 68 species of 38 genera. A biostratigraphic study verified a middle Darriwilian age for the interval spanning the contact between the San Juan and the Las Aguaditas formations. The following zones are determined in the study section: the Lenodusvariabilis Zone, with the Periodongladysae and Paroistodushorridus subzones following the Precordilleran scheme; the L.variabilis, Yangtzeplacognathuscrassus, and the Eoplacognathuspseudoplanuszones with the Microzarkodinahagetiana and M.ozarkodella subzones, and the Pygodusanserinus Zone, according to the Scandinavian scheme; the Periodonmacrodentatus Zone, with the Histiodellasinuosa,H.holodentata and H.cf. holodentatasubzones, and the P.zgierzensis Zone with the H.kristinae Subzone that correlates the North American scheme. A stratigraphic gap was recognized between the lower and middle members of the Las Aguaditas Formation. It comprises the Eoplacognathussuecicus and Pygodus serra zones, and the lower subzone of the PygodusanserinusZone. The variation of conodont diversity through the study section conforms to shallowing and deepening patterns, which accompanies the changes of the provenance lithology. Three conodont assemblages were quantitatively recognized: a) Diverse conodont association, b) Low diversity conodont association and c) Recovery phase association. We propose to use the North American biozonal scheme of conodonts for the Central Precordillera because of the affinity of documented index taxa, which provides a more accurate intercontinental correlation for the global Middle Ordovician Series.Fil: Feltes, Nicolás Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Albanesi, Guillermo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Bergström, S. M.. Ohio State University; Estados Unido

Fiscal redistribution around elections when democracy is not "the only game in town"

This paper seeks to examine the implications of policy intervention around elections on income inequality and fiscal redistribution. We first develop a simplified theoretical framework that allows us to examine election-cycle fiscal redistribution programs in the presence of a revolutionary threat from some groups of agents, i.e., when democracy is not “the only game in town”. According to our theoretical analysis, when democracy is not “the only game in town”, incumbents implement redistributive policies not only as a means of improving their reelection prospects, but also in order to signal that “democracy works”, thereby preventing a reversion to an autocratic status quo ante at a time of the current regime’s extreme vulnerability. Subsequently, focusing on 65 developed and developing countries over the 1975–2010 period, we report robust empirical evidence of pre-electoral budgetary manipulation in new democracies. Consistent with our theory, this finding is driven by political instability that induces incumbents to redistribute income—through tax and spending policies—in a relatively broader coalition of voters with the aim of consolidating the vulnerable newly established democratic regime

Activating Fc γ receptors contribute to the antitumor activities of immunoregulatory receptor-targeting antibodies

Fc γ receptor (FcγR) coengagement can facilitate antibody-mediated receptor activation in target cells. In particular, agonistic antibodies that target tumor necrosis factor receptor (TNFR) family members have shown dependence on expression of the inhibitory FcγR, FcγRIIB. It remains unclear if engagement of FcγRIIB also extends to the activities of antibodies targeting immunoregulatory TNFRs expressed by T cells. We have explored the requirement for activating and inhibitory FcγRs for the antitumor effects of antibodies targeting the TNFR glucocorticoid-induced TNFR-related protein (GITR; TNFRSF18; CD357) expressed on activated and regulatory T cells (T reg cells). We found that although FcγRIIB was dispensable for the in vivo efficacy of anti-GITR antibodies, in contrast, activating FcγRs were essential. Surprisingly, the dependence on activating FcγRs extended to an antibody targeting the non-TNFR receptor CTLA-4 (CD152) that acts as a negative regulator of T cell immunity. We define a common mechanism that correlated with tumor efficacy, whereby antibodies that coengaged activating FcγRs expressed by tumor-associated leukocytes facilitated the selective elimination of intratumoral T cell populations, particularly T reg cells. These findings may have broad implications for antibody engineering efforts aimed at enhancing the therapeutic activity of immunomodulatory antibodies

Adipose-derived stem/stromal cells in kidney transplantation: Status quo and future perspectives

Kidney transplantation (KT) is the gold standard treatment of end-stage renal disease. Despite progressive advances in organ preservation, surgical technique, intensive care, and immunosuppression, long-term allograft survival has not significantly improved. Among the many peri-operative complications that can jeopardize transplant outcomes, ischemia-reperfusion injury (IRI) deserves special consideration as it is associated with delayed graft function, acute rejection, and premature transplant loss. Over the years, several strategies have been proposed to mitigate the impact of IRI and favor tolerance, with rather disappointing results. There is mounting evidence that adipose stem/stromal cells (ASCs) possess specific characteristics that could help prevent, reduce, or reverse IRI. Immunomodulating and tolerogenic properties have also been suggested, thus leading to the development of ASC-based prophylactic and therapeutic strategies in pre-clinical and clinical models of renal IRI and allograft rejection. ASCs are copious, easy to harvest, and readily expandable in culture. Furthermore, ASCs can secrete extracellular vesicles (EV) which may act as powerful mediators of tissue repair and tolerance. In the present review, we discuss the current knowledge on the mechanisms of action and therapeutic opportunities offered by ASCs and ASC-derived EVs in the KT setting. Most relevant pre-clinical and clinical studies as well as actual limitations and future perspective are highlighted

Methane production by mechanochemical processing of MgH2-Li2CO3as sources of H2and CO2at room temperature

The reutilization of CO2 to produce valuable chemical fuels is an attractive approach to reduce the greenhouse effect and global warming. In this work, the room temperature production of CH4/H2 fuel mixtures via mechanochemical activation of Li2CO3-MgH2 system was explored. The CH4/H2 fuel mixtures were obtained by a free-catalyst reaction, with high selectivity and using Li2CO3 and MgH2 as solid portable sources of CO2 and H2, respectively. The effect of processing parameters on both the evolution of the solid phases and the production of CH4/H2 fuel mixtures was studied using X-ray diffraction, spectroscopic techniques, electron scanning microscopy and gas chromatography. Thermodynamic calculations predict the complete CO2 reduction to CH4, with simultaneous formation of MgO and Li2O. Experimental evidence supports the progressive formation of MgO and the appearance of Li2O. The presence of H2 simultaneously with CH4 in the gas phase was due to kinetic restrictions. Based on experimental results and equilibrium composition calculations, the reaction mechanism was proposed. The kinetic analysis reveals that the rate limiting CH4 production is the nucleation of MgO/Li2O in the surroundings of Li2CO3, while the H2 release is controlled by the reaction interface between MgH2/Mg or MgH2/MgO