Infrared spectra of crystalline and glassy silicates and application to interstellar dust

The infrared spectra of crystalline minerals predicted in theoretical condensation sequences do not match the astronomical observations. Since the astronomical spectra are a closer match to glassy silicates, the authors undertook a study to measure the infrared spectra of glassy silicates that have compositions similar to silicate minerals predicted in theoretical condensation sequences. The data should support observations aimed at elucidating condensation chemistry in dust forming regions. The authors measured the mass absorption coefficients, from 2.5 to 25 microns, of ground samples of olivine, diopside, and serpentine and also smoke samples that were prepared from these minerals. The smoke samples prepared in this way are predominantly glassy with nearly the same composition as the parent minerals. The crystalline samples consisted of pure olivine ((Fe(0.1)Mg(0.9))(2)SiO(4)), serpentine, diopside. Sample purity was confirmed by x ray diffraction. Each mineral was ground for 10 hours and a measured mass of the powder was mixed with KBr powder for absorption measurements using the method of Borghesi et a. (1985). The smoke samples were prepared from the same samples used for grinding by vaporizing the minerals using pulsed laser radiation in air. The smoke samples formed by condensation of the resulting vapor. The smoke settled onto infrared transparent KRS-5 substrates and onto a quartz crystal microbalance used to obtain mass measurements. A description of the preparation method is given in Stephens (1980). The glassy diopside showed only diffuse electron diffraction peaks and hence was nearly amorphous, while the serpentine smoke showed a weak diffraction pattern corresponding to MgO. The smoke from olivine showed a weak diffraction pattern corresponding to Fe2O3 and/or Fe3O4. The mass absorption coefficients, from 2.5 to 25 microns, of crystalline diopside, olivine, and serpentine and their corresponding smoke samples are shown in figures

The social and economic bases of network multiplexity: Exploring the emergence of multiplex ties

The goal of this article is to shed light on the role of tie content in the evolution of multiplex ties – i.e., ties featuring both an economic and a social component – in interorganizational networks. The authors clarify and extend the theoretical framework on network multiplexity by testing the extent to which two distinct tie content-related logics – social interaction and economic exchange – and their underlying mechanisms lead to the emergence of multiplex ties. Results from a longitudinal network analysis of firms located in an Italian multimedia cluster support the authors’ hypotheses, confirming that both social and economic drivers contribute to the emergence of network multiplexity, and that social ties have a stronger impact than economic ties on this process, thus providing further insight into the microdynamics of network evolution

The vertical transport of methane from different potential emission types on Mars

The contrasting evolutionary behavior of the vertical profile of methane from three potential release scenarios is analysed using a global circulation model with assimilated temperature profiles. Understanding the evolving methane distribution is essential for interpretation of future retrievals of the methane vertical profile taken by instruments on the ExoMars Trace Gas Orbiter spacecraft. We show that at methane release rates constrained by previous observations and modelling studies, discriminating whether the methane source is a sustained or instantaneous surface emission requires at least ten sols of tracking the emission. A methane source must also be observed within five to ten sols of the initial emission to distinguish whether the emission occurs directly at the surface or within the atmosphere via destabilization of metastable clathrates. Assimilation of thermal data is shown to be critical for the most accurate back-tracking of an observed methane plume to its origin

Long-term ecological consequences of forest fires in the continuous permafrost zone of Siberia

Abstract Wildfires are an important factor in controlling forest ecosystem dynamics across the circumpolar boreal zone. An improved understanding of their direct and indirect, short- to long-term impacts on vegetation cover and permafrost–vegetation coupling is particularly important to predict changes in carbon, nutrient and water cycles under projected climate warming. Here, we apply dendrochronological techniques on a multi-parameter dataset to reconstruct the effect of wildfires on tree growth and seasonal permafrost thaw depth in Central Siberia. Based on annually-resolved and absolutely dated information from 19 Gmelin larch (Larix gmelinii (Rupr.) Rupr.) trees and active soil layer thickness measurements, we find substantial stand-level die-off, as well as the removal of ground vegetation and the organic layer following a major wildfire in 1896. Reduced stem growth coincides with increased δ 13C in the cellulose of the surviving trees during the first decade after the wildfire, when stomatal conductance was reduced. The next six to seven decades are characterized by increased permafrost active soil layer thickness. During this period of post-wildfire ecosystem recovery, enhanced tree growth together with positive δ 13C and negative δ 18O trends are indicative of higher rates of photosynthesis and improved water supply. Afterwards, a thinner active soil layer leads to reduced growth because tree physiological processes become limited by summer temperature and water availability. Revealing long-term effects of forest fires on active soil layer thickness, ground vegetation composition and tree growth, this study demonstrates the importance of complex vegetation–permafrost interactions that modify the trajectory of post-fire forest recovery across much of the circumpolar boreal zone. To further quantify the influence of boreal wildfires on large-scale carbon cycle dynamics, future work should consider a wide range of tree species from different habitats in the high-northern latitudes.</jats:p

Sleep apnea predicts distinct alterations in glucose homeostasis and biomarkers in obese adults with normal and impaired glucose metabolism

<p>Abstract</p> <p>Background</p> <p>Notwithstanding previous studies supporting independent associations between obstructive sleep apnea (OSA) and prevalence of diabetes, the underlying pathogenesis of impaired glucose regulation in OSA remains unclear. We explored mechanisms linking OSA with prediabetes/diabetes and associated biomarker profiles. We hypothesized that OSA is associated with distinct alterations in glucose homeostasis and biomarker profiles in subjects with normal (NGM) and impaired glucose metabolism (IGM).</p> <p>Methods</p> <p>Forty-five severely obese adults (36 women) without certain comorbidities/medications underwent anthropometric measurements, polysomnography, and blood tests. We measured fasting serum glucose, insulin, selected cytokines, and calculated homeostasis model assessment estimates of insulin sensitivity (HOMA-IS) and pancreatic beta-cell function (HOMA-B).</p> <p>Results</p> <p>Both increases in apnea-hypopnea index (AHI) and the presence of prediabetes/diabetes were associated with reductions in HOMA-IS in the entire cohort even after adjustment for sex, race, age, and BMI (<it>P </it>= 0.003). In subjects with NGM (n = 30), OSA severity was associated with significantly increased HOMA-B (a trend towards decreased HOMA-IS) independent of sex and adiposity. OSA-related oxyhemoglobin desaturations correlated with TNF-α (r=-0.76; <it>P </it>= 0.001) in women with NGM and with IL-6 (rho=-0.55; <it>P </it>= 0.035) in women with IGM (n = 15) matched individually for age, adiposity, and AHI.</p> <p>Conclusions</p> <p>OSA is independently associated with altered glucose homeostasis and increased basal beta-cell function in severely obese adults with NGM. The findings suggest that moderate to severe OSA imposes an excessive functional demand on pancreatic beta-cells, which may lead to their exhaustion and impaired secretory capacity over time. The two distinct biomarker profiles linking sleep apnea with NGM and IGM via TNF-α and IL-6 have been discerned in our study to suggest that sleep apnea and particularly nocturnal oxyhemoglobin desaturations are associated with chronic metabolic fluxes and specific cytokine stressors that reflect links between sleep apnea and glucose metabolism. The study may help illuminate potential mechanisms for glucose dysregulation in OSA, and resolve some controversy over the associations of OSA with TNF-α and IL-6 in previous studies.</p

A tree-centered approach to assess impacts of extreme climatic events on forests

Ajut Marie Curie IF fellowship (No 659191); COST Action FP1106 STReES

Sorafenib in advanced iodine-refractory differentiated thyroid cancer: efficacy, safety and exploratory analysis of role of serum thyroglobulin and FDG-PET.

Context Radioactive iodine is a crucial tool for treatment of differentiated thyroid cancer (DTC). In 5% of cases, DTCs lose I-131 avidity and assume an aggressive behaviour. Treatment options for iodine-refractory DTC are limited. We report the experience of off-label use of the tyrosine kinase inhibitor sorafenib for treatment of advanced iodine-refractory DTC. Design Patients with progressive DTC refractory to radioactive iodine were treated with sorafenib used off-label independently from their performance status. Primary study end-points were radiological response, progression-free survival (PFS) and safety. Secondary end-points were site-specific radiological response and overall survival (OS). An exploratory analysis of the role of serum thyroglobulin (Tg) and fluorodeoxyglucose (FDG) positron emission tomography (PET) was performed. Results A total of 17 patients were included in the study. Median follow-up was 15·5 months. Clinical benefit was obtained in 71% of subjects (30% partial response and 41% stable disease). Sorafenib was mostly well tolerated, but a high incidence of fatal events was reported (three patients died from severe bleeding events and two from cardiac arrest). Median PFS was 9 months. Median OS was 10 months. The best responses were observed in lymph nodes and lung. Baseline Tg levels and the Tg response to treatment were correlated to both radiological response and PFS. Baseline FDG-PET assessment and early FDG-PET response were correlated to radiological response. Conclusions Sorafenib allows morphological disease control in the majority of patients with iodine-refractory DTC. Progression-free survival and overall survival were lower than in previous studies as a consequence of the worse clinical condition of our patients. Sorafenib is mostly well tolerated but could have been responsible for the reported fatal events. Baseline Tg and the Tg response to treatment could be useful for predicting morphological response and clinical outcome. Early FDG-PET response could be helpful for the timely identification of nonresponding patients

Validation of statistical clustering on TES dataset using synthetic Martian spectra

In this work we present some results concerning the analysis of Thermal Emission Spectrometer (TES) data, looking at the methane Q-branch spectral signature at 1304 cm-1. Such analysis has been enabled by producing some synthetic spectral datasets, simulating the atmospheric and surface variability observed on Mars, excluding the high latitude regions. The use of synthetic spectra is aimed to provide a better comprehension of the influence that the atmospheric state vector and its composition have on the spectral behavior. This effort is important, because the TES data are characterized by a low resolution (10 cm-1) and a significant random and systematic noise which could, in principle, give results whose quality needs to be improved. We apply statistical clustering of the synthetic spectra to evaluate the effectiveness of detecting methane, and estimating its abundance

Defining an Adequate Sample of Earlywood Vessels for Retrospective Injury Detection in Diffuse-Porous Species

Vessels of broad-leaved trees have been analyzed to study how trees deal with various environmental factors. Cambial injury, in particular, has been reported to induce the formation of narrower conduits. Yet, little or no effort has been devoted to the elaboration of vessel sampling strategies for retrospective injury detection based on vessel lumen size reduction. To fill this methodological gap, four wounded individuals each of grey alder (Alnus incana (L.) Moench) and downy birch (Betula pubescens Ehrh.) were harvested in an avalanche path. Earlywood vessel lumina were measured and compared for each tree between the injury ring built during the growing season following wounding and the control ring laid down the previous year. Measurements were performed along a 10 mm wide radial strip, located directly next to the injury. Specifically, this study aimed at (i) investigating the intra-annual duration and local extension of vessel narrowing close to the wound margin and (ii) identifying an adequate sample of earlywood vessels (number and intra-ring location of cells) attesting to cambial injury. Based on the results of this study, we recommend analyzing at least 30 vessels in each ring. Within the 10 mm wide segment of the injury ring, wound-induced reduction in vessel lumen size did not fade with increasing radial and tangential distances, but we nevertheless advise favoring early earlywood vessels located closest to the injury. These findings, derived from two species widespread across subarctic, mountainous, and temperate regions, will assist retrospective injury detection in Alnus, Betula, and other diffuse-porous species as well as future related research on hydraulic implications after wounding