The oxygen isotopic composition of phytolith assemblages from tropical rainforest soil tops (Queensland, Australia): validation of a new paleoenvironmental tool

Phytoliths are micrometric particles of amorphous silica that form inside or between the cells of higher plant tissues throughout the life of a plant. With plant decay, phytoliths are either incorporated into soils or exported to sediments via regional watersheds. Phytolith morphological assemblages are increasingly used as proxy of grassland diversity and tree cover density in inter-tropical areas. Here, we investigate whether, along altitudinal gradients in northeast Queensland (Australia), changes in the δ<sup>18</sup>O signature of soil top phytolith assemblages reflect changes in mean annual temperature (MAT) and in the oxygen isotopic composition of precipitation (δ<sup>18</sup>O<sub>precipitation</sub>), as predicted by equilibrium temperature coefficients previously published for silica. Oxygen isotopic analyses were performed on 16 phytolith samples, after controlled isotopic exchange (CIE), using the IR Laser-Heating Fluorination Technique. Long-term mean annual precipitation (MAP) and MAT values at the sampled sites were calculated by the ANUCLIM software. δ<sup>18</sup>O<sub>precipitation</sub> estimates were calculated using the Bowen and Wilkinson (2002) model, slightly modified. An empirical temperature-dependant relationship was obtained: δ<sup>18</sup>O<sub>wood phytolith-precipitation</sub> (‰ vs. VSMOW) = −0.4 (±0.2) <i>t</i> (°C) + 46 (±3) (<i>R</i><sup>2</sup> = 0.4, <i>p</i> < 0.05; <i>n</i> = 12). Despite the various unknowns introduced when estimating δ<sup>18</sup>O<sub>precipitation</sub> values and the large uncertainties on δ<sup>18</sup>O<sub>wood phytolith</sub> values, the temperature coefficient (−0.4 ± 0.2‰ °C<sup>−1</sup>) is in the range of values previously obtained for natural quartz, fresh and sedimentary diatoms and harvested grass phytoliths (from −0.2 to −0.5‰ °C<sup>−1</sup>). The consistency supports the reliability of δ<sup>18</sup>O<sub>wood phytolith</sub> signatures for recording relative changes in mean annual δ<sup>18</sup>O<sub>soil water</sub> values (which are assumed to be equivalent to the weighted annual δ<sup>18</sup>O<sub> precipitation</sub> values in rainforests environments) and MAT, provided these changes were several ‰ and/or several °C in magnitude

Cargas en cubiertas curvas con obstrucciones para viento incidiendo oblícuamente

Se simula el viento natural sobre construcciones de cubierta curva sin paredes laterales,incidiendo en forma oblicua a la generatriz, cuando bajo las mismas se ubican obstrucciones debidas aobjetos diversos. Este tipo de situación resulta bastante común en la práctica y no siempre esconsiderada en el proyecto de tales estructuras. A pesar de las diferencias aerodinámicas evidentesentre la situación con y sin obstrucciones no se dispone de especificaciones que permitan evaluar lascargas en estos casos en los códigos de diseño. Los resultados reportados se obtuvieron mediantedinámica de fluidos computacional (CFD, por computational fluid dynamics), tratando la turbulenciaa través de un modelo de simulación de grandes vórtices (LES, por large eddy simulation).Laboratorio de Capa Límite y Fluidodinámica AmbientalGrupo Fluidodinámica Computaciona

Nuclear matrix element for two neutrino double beta decay from 136Xe

The nuclear matrix element for the two neutrino double beta decay (DBD) of 136Xe was evaluated by FSQP (Fermi Surface Quasi Particle model), where experimental GT strengths measured by the charge exchange reaction and those by the beta decay rates were used. The 2 neutrino DBD matrix element is given by the sum of products of the single beta matrix elements via low-lying (Fermi Surface) quasi-particle states in the intermediate nucleus. 136Xe is the semi-magic nucleus with the closed neutron-shell, and the beta + transitions are almost blocked. Thus the 2 neutrino DBD is much suppressed. The evaluated 2 neutrino DBD matrix element is consistent with the observed value.Comment: 7 pages 6 figure

Cargas en cubiertas curvas con obstrucciones para viento incidiendo oblícuamente

Se simula el viento natural sobre construcciones de cubierta curva sin paredes laterales,incidiendo en forma oblicua a la generatriz, cuando bajo las mismas se ubican obstrucciones debidas aobjetos diversos. Este tipo de situación resulta bastante común en la práctica y no siempre esconsiderada en el proyecto de tales estructuras. A pesar de las diferencias aerodinámicas evidentesentre la situación con y sin obstrucciones no se dispone de especificaciones que permitan evaluar lascargas en estos casos en los códigos de diseño. Los resultados reportados se obtuvieron mediantedinámica de fluidos computacional (CFD, por computational fluid dynamics), tratando la turbulenciaa través de un modelo de simulación de grandes vórtices (LES, por large eddy simulation).Laboratorio de Capa Límite y Fluidodinámica AmbientalGrupo Fluidodinámica Computaciona

Cargas en cubiertas curvas con obstrucciones para viento incidiendo oblícuamente

Se simula el viento natural sobre construcciones de cubierta curva sin paredes laterales,incidiendo en forma oblicua a la generatriz, cuando bajo las mismas se ubican obstrucciones debidas aobjetos diversos. Este tipo de situación resulta bastante común en la práctica y no siempre esconsiderada en el proyecto de tales estructuras. A pesar de las diferencias aerodinámicas evidentesentre la situación con y sin obstrucciones no se dispone de especificaciones que permitan evaluar lascargas en estos casos en los códigos de diseño. Los resultados reportados se obtuvieron mediantedinámica de fluidos computacional (CFD, por computational fluid dynamics), tratando la turbulenciaa través de un modelo de simulación de grandes vórtices (LES, por large eddy simulation).Laboratorio de Capa Límite y Fluidodinámica AmbientalGrupo Fluidodinámica Computaciona

What is known about deferasirox chelation therapy in pediatric HSCT recipients: two case reports of metabolic acidosis

To date, in pediatric field, various hematological malignancies are increasingly treated with allogeneic hematopoietic stem cell transplantation (allo-HSCT). Iron overload and systemic siderosis often occur in this particular cohort of patients and are associated with poor prognosis. We describe herein the case of two allo-HSCT patients, on treatment with deferasirox; they showed histopathological elements compatible with venoocclusive disease or vanishing bile duct syndrome in ductopenic evolution before deferasirox started. The first patient developed drug-induced liver damage with metabolic acidosis and the second one a liver impairment with Fanconi syndrome. After withdrawing deferasirox treatment, both patients showed improvement. Measurements of drug plasma concentrations were performed by HPLC assay. The reduction and consequent disappearance of symptoms after the suspension of deferasirox substantiate its role in inducing hepatic damage, probably enabling the diagnosis of drug-induced liver damage. But the difficulties in diagnosing drug-related toxicity must be underlined, especially in compromised subjects. For these reasons, in patients requiring iron-chelating therapy, close and careful drug therapeutic monitoring is strongly recommende