Diatom based transfer function for estimating the chemical composition of fossil water. Calibration based on salt lakes of the Lipez area in the southwestern Bolivian Altiplano

Diatom assemblages and water chemistry were studied in 13 shallow salt lakes in the southern part of the Bolivian Altiplano. At each locality bottom sediment and water samples were collected simultaneously. Relationships between the composition of the diatom assemblages and variations in water chemistry were collated in order to permit the estimation of ancient water chemistries based on changes in the make up of fossil diatom associations in older sediments. Weighted Averages treated by Partial Least Squares regression (WA and WA-PLS methods) allowed an estimation of optima and the relative tolerances of 61 species to variations in salinity and to the relative quantities of the 15 chemical elements studied, among them boron and lithium.L'étude des assemblages de diatomées et de la composition chimique des eaux a été effectuée dans 13 lacs salés peu profonds localisés dans le Sud de l'Altiplano Bolivien. Les points et les dates de prélèvement sont les mêmes pour les deux types d'étude. Les relations entre les assemblages de diatomées et les variables chimiques mesurées sont effectuées dans le but d'estimer ces variables dans le passé à partir des diatomées fossiles conservées dans les sédiments. La méthode des moyennes pondérées (WA et WA-PLS régression) a permis d'estimer les optima et les tolérances de 61 espèces à la salinité et aux différents éléments chimiques dont le bore et le lithium

High-J CO emission in the Cepheus E protostellar outflow observed with SOFIA/GREAT

We present and analyze two spectrally resolved high-J CO lines towards the molecular outflow Cep E, driven by an intermediate-mass class 0 protostar. Using the GREAT receiver on board SOFIA, we observed the CO (12--11) and (13--12) transitions (E_u ~ 430 and 500 K, respectively) towards one position in the blue lobe of this outflow, that had been known to display high-velocity molecular emission. We detect the outflow emission in both transitions, up to extremely high velocities (~ 100 km/s with respect to the systemic velocity). We divide the line profiles into three velocity ranges that each have interesting spectral features: standard, intermediate, and extremely high-velocity. One distinct bullet is detected in each of the last two. A large velocity gradient analysis for these three velocity ranges provides constraints on the kinetic temperature and volume density of the emitting gas, >~ 100 K and > ~ 10^4 cm^-3, respectively. These results are in agreement with previous ISO observations and are comparable with results obtained by Herschel for similar objects. We conclude that high-J CO lines are a good tracer of molecular bullets in protostellar outflows. Our analysis suggests that different physical conditions are at work in the intermediate velocity range compared with the standard and extremely high-velocity gas at the observed position.Comment: Accepted for publication in A&A (SOFIA/GREAT special issue

Identifying disease sensitive and quantitative trait-relevant biomarkers from multidimensional heterogeneous imaging genetics data via sparse multimodal multitask learning

Motivation: Recent advances in brain imaging and high-throughput genotyping techniques enable new approaches to study the influence of genetic and anatomical variations on brain functions and disorders. Traditional association studies typically perform independent and pairwise analysis among neuroimaging measures, cognitive scores and disease status, and ignore the important underlying interacting relationships between these units

Кераміка для техніки

The benthic invertebrates fauna of most of the saline lakes of the Sud Lipez region (Bolivia, Altiplano) has been until now quite unstudied. Samples collected during an extensive survey of 12 lakes and two small inflow rivers allow a first list of the main macroinvertebrates living in the biotopes. The heterogeneous nature of these saline lakes with their freshwater springs and phreatic inflows offers a variety of habitats to macroinvertebrates. The benthic fauna in lakes with salinity > 10 g l-1 is not so low in density but includes few species and is dominated by Orthocladinae and Podonominae larvae. In contrast, the freshwater springs and inflows are colonized by a diverse fauna with a mixture of both freshwater and saline taxa, but dominated by Elmidae and Amphipoda. The lakes are quite isolated and, apart from some cosmopolitan organisms, their fauna can be quite distinctive. (Résumé d'auteur

Excitation of the molecular gas in the nuclear region of M82

We present high resolution HIFI spectroscopy of the nucleus of the archetypical starburst galaxy M82. Six 12CO lines, 2 13CO lines and 4 fine-structure lines are detected. Besides showing the effects of the overall velocity structure of the nuclear region, the line profiles also indicate the presence of multiple components with different optical depths, temperatures and densities in the observing beam. The data have been interpreted using a grid of PDR models. It is found that the majority of the molecular gas is in low density (n=10^3.5 cm^-3) clouds, with column densities of N_H=10^21.5 cm^-2 and a relatively low UV radiation field (GO = 10^2). The remaining gas is predominantly found in clouds with higher densities (n=10^5 cm^-3) and radiation fields (GO = 10^2.75), but somewhat lower column densities (N_H=10^21.2 cm^-2). The highest J CO lines are dominated by a small (1% relative surface filling) component, with an even higher density (n=10^6 cm^-3) and UV field (GO = 10^3.25). These results show the strength of multi-component modeling for the interpretation of the integrated properties of galaxies.Comment: Accepted for publication in A&A Letter

Detection of 6.7 GHz methanol absorption towards hot corinos

Methanol masers at 6.7 GHz have been found exclusively towards high-mass star forming regions. Recently, some Class 0 protostars have been found to display conditions similar to what are found in hot cores that are associated with massive star formation. These hot corino sources have densities, gas temperatures, and methanol abundances that are adequate for exciting strong 6.7 GHz maser emission. This raises the question of whether 6.7 GHz methanol masers can be found in both hot corinos and massive star forming regions, and if not, whether thermal methanol emission can be detected. We searched for the 6.7 GHz methanol line towards five hot corino sources in the Perseus region using the Arecibo radio telescope. To constrain the excitation conditions of methanol, we observed thermal submillimeter lines of methanol in the NGC1333-IRAS 4 region with the APEX telescope. We did not detect 6.7 GHz emission in any of the sources, but found absorption against the cosmic microwave background in NGC1333-IRAS 4A and NGC1333-IRAS 4B. Using a large velocity gradient analysis, we modeled the excitation of methanol over a wide range of physical parameters, and verify that the 6.7 GHz line is indeed strongly anti-inverted for densities lower than 10^6 cm^-3. We used the submillimeter observations of methanol to verify the predictions of our model for IRAS 4A by comparison with other CH3OH transitions. Our results indicate that the methanol observations from the APEX and Arecibo telescopes are consistent with dense (n ~ 10^6 cm^-3), cold (T ~ 15-30 K) gas. The lack of maser emission in hot corinos and low-mass protostellar objects in general may be due to densities that are much higher than the quenching density in the region where the radiation field is conducive to maser pumping.Comment: Accepted by A&

Differential trajectories of hypometabolism across cognitively-defined Alzheimer’s disease subgroups

Disentangling biologically distinct subgroups of Alzheimer’s disease (AD) may facilitate a deeper understanding of the neurobiology underlying clinical heterogeneity. We employed longitudinal [18F]FDG-PET standardized uptake value ratios (SUVRs) to map hypometabolism across cognitively-defined AD subgroups. Participants were 384 amyloid-positive individuals with an AD dementia diagnosis from ADNI who had a total of 1028 FDG-scans (mean time between first and last scan: 1.6 ± 1.8 years). These participants were categorized into subgroups on the basis of substantial impairment at time of dementia diagnosis in a specific cognitive domain relative to the average across domains. This approach resulted in groups of AD-Memory (n = 135), AD-Executive (n = 8), AD-Language (n = 22), AD-Visuospatial (n = 44), AD-Multiple Domains (n = 15) and AD-No Domains (for whom no domain showed substantial relative impairment; n = 160). Voxelwise contrasts against controls revealed that all AD-subgroups showed progressive hypometabolism compared to controls across temporoparietal regions at time of AD diagnosis. Voxelwise and regions-of-interest (ROI)-based linear mixed model analyses revealed there were also subgroup-specific hypometabolism patterns and trajectories. The AD-Memory group had more pronounced hypometabolism compared to all other groups in the medial temporal lobe and posterior cingulate, and faster decline in metabolism in the medial temporal lobe compared to AD-Visuospatial. The AD-Language group had pronounced lateral temporal hypometabolism compared to all other groups, and the pattern of metabolism was also more asymmetrical (left < right) than all other groups. The AD-Visuospatial group had faster decline in metabolism in parietal regions compared to all other groups, as well as faster decline in the precuneus compared to AD-Memory and AD-No Domains. Taken together, in addition to a common pattern, cognitively-defined subgroups of people with AD dementia show subgroup-specific hypometabolism patterns, as well as differences in trajectories of metabolism over time. These findings provide support to the notion that cognitively-defined subgroups are biologically distinct

Sensitive limits on the abundance of cold water vapor in the DM Tau protoplanetary disk

We performed a sensitive search for the ground-state emission lines of ortho- and para-water vapor in the DM Tau protoplanetary disk using the Herschel/HIFI instrument. No strong lines are detected down to 3sigma levels in 0.5 km/s channels of 4.2 mK for the 1_{10}--1_{01} line and 12.6 mK for the 1_{11}--0_{00} line. We report a very tentative detection, however, of the 1_{10}--1_{01} line in the Wide Band Spectrometer, with a strength of T_{mb}=2.7 mK, a width of 5.6 km/s and an integrated intensity of 16.0 mK km/s. The latter constitutes a 6sigma detection. Regardless of the reality of this tentative detection, model calculations indicate that our sensitive limits on the line strengths preclude efficient desorption of water in the UV illuminated regions of the disk. We hypothesize that more than 95-99% of the water ice is locked up in coagulated grains that have settled to the midplane.Comment: 5 pages, 3 figures. Accepted for publication in the Herschel HIFI special issue of A&

Hydrides in Young Stellar Objects: Radiation tracers in a protostar-disk-outflow system

Context: Hydrides of the most abundant heavier elements are fundamental molecules in cosmic chemistry. Some of them trace gas irradiated by UV or X-rays. Aims: We explore the abundances of major hydrides in W3 IRS5, a prototypical region of high-mass star formation. Methods: W3 IRS5 was observed by HIFI on the Herschel Space Observatory with deep integration (about 2500 s) in 8 spectral regions. Results: The target lines including CH, NH, H3O+, and the new molecules SH+, H2O+, and OH+ are detected. The H2O+ and OH+ J=1-0 lines are found mostly in absorption, but also appear to exhibit weak emission (P-Cyg-like). Emission requires high density, thus originates most likely near the protostar. This is corroborated by the absence of line shifts relative to the young stellar object (YSO). In addition, H2O+ and OH+ also contain strong absorption components at a velocity shifted relative to W3 IRS5, which are attributed to foreground clouds. Conclusions: The molecular column densities derived from observations correlate well with the predictions of a model that assumes the main emission region is in outflow walls, heated and irradiated by protostellar UV radiation.Comment: Astronomy and Astrophysics Letters, in pres