Explore the vast range of titles available.

\"From his first paintings to the colorful flower images of his later career, Vincent van Gogh (1853-1890) repeatedly painted still lifes. In this genre, he could try out various media and alternatives--from depicting space using light and shadow to experiments with color. The first exhibition on this theme will present 27 paintings and use them to analyze the key stages in van Gogh's life and work. Van Gogh: Still Lifes is the first systematic exploration of this important theme in the artist's work in an exhibition. Of the roughly 800 paintings that Vincent van Gogh (1853-1890) created during his ten-year career as an artist, some 170--about a fifth--are still lifes. It is therefore all the more remarkable that there has never been a monographic exhibition dedicated to the genre of the still life in Van Gogh's work\"--Publisher's description.

Endothelial cells (ECs) contribute to haematopoietic stem cell (HSC) maintenance in bone marrow, but the differential contributions of EC subtypes remain unknown, owing to the lack of methods to separate with high purity arterial endothelial cells (AECs) from sinusoidal endothelial cells (SECs). Here we show that the combination of podoplanin (PDPN) and Sca-1 expression distinguishes AECs (CD45 − Ter119 − Sca-1 bright PDPN − ) from SECs (CD45 − Ter119 − Sca-1 dim PDPN + ). PDPN can be substituted for antibodies against the adhesion molecules ICAM1 or E-selectin. Unexpectedly, prospective isolation reveals that AECs secrete nearly all detectable EC-derived stem cell factors (SCF). Genetic deletion of Scf in AECs, but not SECs, significantly reduced functional HSCs. Lineage-tracing analyses suggest that AECs and SECs self-regenerate independently after severe genotoxic insults, indicating the persistence of, and recovery from, radio-resistant pre-specified EC precursors. AEC-derived SCF also promotes HSC recovery after myeloablation. These results thus uncover heterogeneity in the contribution of ECs in stem cell niches. Endothelial cells (EC) are known to contribute to haematopoietic stem cell (HSC) maintenance in the bone marrow (BM). Here the authors demonstrate that arterial ECs can be distinguished from sinusoidal ECs by podoplanin and Sca-1 expression, and that specifically arterial, but not sinusoidal ECs maintain HSCs by secreting SCF.

Protists are single-celled organisms complete with nuclei, organelles, and symbionts, and possess a multiplicity of physiological talents. They are ubiquitous, abundant, and often neglected by science. Worden et al. review the challenges of understanding the role protists play in geochemical cycling in the oceans. These organisms can photosynthesize like plants, graze on bacteria and archaea, parasitize each other and bigger creatures, have sex, and sometimes do all these things serially as conditions change. Their activities may have a significant influence on carbon cycling, and research efforts need to be amplified to understand their functional importance in marine ecosystems. Science , this issue 10.1126/science.1257594 The profound influence of marine plankton on the global carbon cycle has been recognized for decades, particularly for photosynthetic microbes that form the base of ocean food chains. However, a comprehensive model of the carbon cycle is challenged by unicellular eukaryotes (protists) having evolved complex behavioral strategies and organismal interactions that extend far beyond photosynthetic lifestyles. As is also true for multicellular eukaryotes, these strategies and their associated physiological changes are difficult to deduce from genome sequences or gene repertoires—a problem compounded by numerous unknown function proteins. Here, we explore protistan trophic modes in marine food webs and broader biogeochemical influences. We also evaluate approaches that could resolve their activities, link them to biotic and abiotic factors, and integrate them into an ecosystems biology framework.

We performed triaxial compressive creep experiments on aggregates of San Carlos olivine to develop a flow law and to examine microstructural development in the dislocation‐accommodated grain boundary sliding regime (GBS). Each experiment included load and temperature steps to determine both the stress exponent and the activation energy. Grain boundary maps, created with electron backscatter diffraction data, were used to quantify grain size distributions for each sample. Inversion of the resulting data produced the following flow law for GBS: GBS = 104.8 ± 0.8 (σ2.9 ± 0.3/d0.7 ± 0.1) exp[(−445 ± 20 kJ mol−1)/RT], with σ, d, and GBS in units of MPa, μm, and s−1, respectively. Although relatively weak, crystallographic‐preferred orientations (CPOs) have [010] maxima parallel to the compression direction along with [100] and [001] girdles perpendicular to the compression direction. CPOs and subgrain boundary misorientation axes suggest that the (010)[100] slip system contributes significantly to deformation. We propose that these experimental results are best modeled by a deformation mechanism in which strain is accomplished primarily through grain boundary sliding accommodated by the motion of dislocations. Extrapolation of our flow laws to mantle conditions suggests that GBS is likely to be the dominant deformation mechanism in both lithospheric shear zones and asthenospheric flow, and therefore strong upper mantle seismic anisotropy can not be attributed solely to the dominance of dislocation creep. Key Points We determined a flow law for the grain boundary sliding (GBS) regime Extrapolations of our flow law imply that GBS is dominant in the upper mantle Observed crystallographic fabrics agree with patterns of seismic anisotropy

Understanding the relationship between prokaryotic traits and phylogeny is important for predicting and modeling ecological processes. Microbial extracellular enzymes have a pivotal role in nutrient cycling and the decomposition of organic matter, yet little is known about the phylogenetic distribution of genes encoding these enzymes. In this study, we analyzed 3058 annotated prokaryotic genomes to determine which taxa have the genetic potential to produce alkaline phosphatase, chitinase and β-N-acetyl-glucosaminidase enzymes. We then evaluated the relationship between the genetic potential for enzyme production and 16S rRNA phylogeny using the consenTRAIT algorithm, which calculated the phylogenetic depth and corresponding 16S rRNA sequence identity of clades of potential enzyme producers. Nearly half (49.2%) of the genomes analyzed were found to be capable of extracellular enzyme production, and these were non-randomly distributed across most prokaryotic phyla. On average, clades of potential enzyme-producing organisms had a maximum phylogenetic depth of 0.008004–0.009780, though individual clades varied broadly in both size and depth. These values correspond to a minimum 16S rRNA sequence identity of 98.04–98.40%. The distribution pattern we found is an indication of microdiversity, the occurrence of ecologically or physiologically distinct populations within phylogenetically related groups. Additionally, we found positive correlations among the genes encoding different extracellular enzymes. Our results suggest that the capacity to produce extracellular enzymes varies at relatively fine-scale phylogenetic resolution. This variation is consistent with other traits that require a small number of genes and provides insight into the relationship between taxonomy and traits that may be useful for predicting ecological function.

Introduction There is an urgent need to validate telephone versions of widely used general cognitive measures, such as the Montreal Cognitive Assessment (T‐MoCA), for remote assessments. Methods In the Einstein Aging Study, a diverse community cohort (n = 428; mean age = 78.1; 66% female; 54% non‐White), equivalence testing was used to examine concordance between the T‐MoCA and the corresponding in‐person MoCA assessment. Receiver operating characteristic analyses examined the diagnostic ability to discriminate between mild cognitive impairment and normal cognition. Conversion methods from T‐MoCA to the MoCA are presented. Results Education, race/ethnicity, gender, age, self‐reported cognitive concerns, and telephone administration difficulties were associated with both modes of administration; however, when examining the difference between modalities, these factors were not significant. Sensitivity and specificity for the T‐MoCA (using Youden's index optimal cut) were 72% and 59%, respectively. Discussion The T‐MoCA demonstrated sufficient psychometric properties to be useful for screening of MCI, especially when clinic visits are not feasible.

Although microstructural evolution is critical to strain‐dependent processes in Earth's mantle, flow laws for dunite have only been calibrated with low‐strain experiments. Therefore, we conducted a series of high‐strain torsion experiments on thin‐walled cylinders of iron‐rich olivine aggregates. Experiments were performed in a gas‐medium apparatus at 1200°C and constant strain rate. In our experiments, each at a different strain rate, a peak stress was observed followed by significant strain weakening. We first deformed samples to high enough strain that a steady state microstructure was achieved and then conducted strain rate stepping tests to characterize the creep behavior of each sample with constant microstructure. A global fit to the data yields a stress exponent of 4.1 and a grain‐size exponent of 0.73, values which agree well with those from previous small‐strain experiments conducted on olivine in the dislocation‐accommodated grain‐boundary sliding (GBS) regime. Strong crystallographic preferred orientations provide support for GBS accommodated by movement of (010)[100] dislocations. The observed strain weakening is not entirely explained by grain‐size reduction; thus, we propose that the remaining 30% reduction in stress is related to CPO development. To incorporate microstructural evolution in a constitutive description of GBS in olivine, we (1) derive a flow law for high‐strain deformation with steady state microstructure, which results in an apparent stress exponent of 5.0, and (2) present a system of evolution equations that recreate the observed strain weakening. Our results corroborate flow‐law parameters and microstructural observations from low‐strain experiments and provide a means for incorporating strain weakening into geodynamic simulations. Key Points We explore the high‐strain behavior of olivine with a novel experiment design We quantify the effect of grain size and crystallographic fabric on deformation We develop a model that describes the strain dependence of olivine deformation

The final fate of massive stars, and the nature of the compact remnants they leave behind (black holes and neutron stars), are open questions in astrophysics. Many massive stars are stripped of their outer hydrogen envelopes as they evolve. Such Wolf–Rayet stars 1 emit strong and rapidly expanding winds with speeds greater than 1,000 kilometres per second. A fraction of this population is also helium-depleted, with spectra dominated by highly ionized emission lines of carbon and oxygen (types WC/WO). Evidence indicates that the most commonly observed supernova explosions that lack hydrogen and helium (types Ib/Ic) cannot result from massive WC/WO stars 2 , 3 , leading some to suggest that most such stars collapse directly into black holes without a visible supernova explosion 4 . Here we report observations of SN 2019hgp, beginning about a day after the explosion. Its short rise time and rapid decline place it among an emerging population of rapidly evolving transients 5 – 8 . Spectroscopy reveals a rich set of emission lines indicating that the explosion occurred within a nebula composed of carbon, oxygen and neon. Narrow absorption features show that this material is expanding at high velocities (greater than 1,500 kilometres per second), requiring a compact progenitor. Our observations are consistent with an explosion of a massive WC/WO star, and suggest that massive Wolf–Rayet stars may be the progenitors of some rapidly evolving transients. Observations of the supernova SN 2019hgp, identified about a day after its explosion, show that it occurred within a nebula of carbon, oxygen and neon, and was probably the explosion of a massive WC/WO star.

Measurements of the viscous anisotropy of highly deformed polycrystalline olivine find it to be approximately an order of magnitude larger than that predicted by grain-scale simulations; the maximum degree of anisotropy is reached at geologically low shear strain, such that deforming regions of the Earth’s upper mantle should exhibit significant viscous anisotropy. Viscous anisotropy of the mantle The viscous anisotropy of the rocks of the Earth's mantle strongly affects many tectonic-scale processes. Here, Lars Hansen et al . present measurements of the viscous anisotropy of highly deformed polycrystalline olivine, a dominant mineral in the Earth's crust, and find that the anisotropy is approximately an order of magnitude larger than that predicted by grain-scale simulations. The maximum degree of anisotropy is reached at geologically low shear strain, such that deforming regions of the upper mantle should exhibit significant viscous anisotropy. The discrepancy between numerical simulations and laboratory experiments highlights the limitations of current models of anisotropy, and these results provide important constraints for future geodynamic simulations. A marked anisotropy in viscosity develops in Earth’s mantle as deformation strongly aligns the crystallographic axes of the individual grains that comprise the rocks. On the basis of geodynamic simulations, processes significantly affected by viscous anisotropy include post-glacial rebound 1 , 2 , foundering of lithosphere 3 and melt production above subduction zones 4 . However, an estimate of the magnitude of viscous anisotropy based on the results of deformation experiments on single crystals 5 differs by three orders of magnitude from that obtained by grain-scale numerical models of deforming aggregates with strong crystallographic alignment 6 , 7 , 8 . Complicating matters, recent experiments indicate that deformation of the uppermost mantle is dominated by dislocation-accommodated grain-boundary sliding 9 , a mechanism not activated in experiments on single crystals and not included in numerical models. Here, using direct measurements of the viscous anisotropy of highly deformed polycrystalline olivine, we demonstrate a significant directional dependence of viscosity. Specifically, shear viscosities measured in high-strain torsion experiments are 15 times smaller than normal viscosities measured in subsequent tension tests performed parallel to the torsion axis. This anisotropy is approximately an order of magnitude larger than that predicted by grain-scale simulations. These results indicate that dislocation-accommodated grain-boundary sliding produces an appreciable anisotropy in rock viscosity. We propose that crystallographic alignment imparts viscous anisotropy because the rate of deformation is limited by the movement of dislocations through the interiors of the crystallographically aligned grains. The maximum degree of anisotropy is reached at geologically low shear strain (of about ten) such that deforming regions of the upper mantle will exhibit significant viscous anisotropy.

Majority of hearing-loss cases with extremely preterm infants have no known etiology. There is a growing concern that the administration of aminoglycoside treatment in the noisy environment of the Neonatal Intensive Care Unit (NICU) may lead to hair-cell damage and subsequent auditory impairments. In addition, several mitochondrial DNA mutations are known to have been associated with aminoglycoside-induced hearing loss. This review provides a systematic analysis of the research in this area and elucidates the multifactorial mechanisms behind how mitochondrial DNA mutations, aminoglycosides and loud noise can potentiate ototoxicity in extremely preterm neonates. Recommended steps to minimize the risk of ototoxicity and improve clinical care for NICU infants are discussed.