A Synchrotron Mössbauer Spectroscopy Study of a Hydrated Iron-Sulfate at High Pressures

Szomolnokite is a monohydrated ferrous iron sulfate mineral, FeSO₄·H₂O, where the ferrous iron atoms are in octahedral coordination with four corners shared with SO4 and two with H₂O groups. While somewhat rare on Earth, szomolnokite has been detected on the surface of Mars along with several other hydrated sulfates and is suggested to occur near the surface of Venus. Previous measurements have characterized the local environment of the iron atoms in szomolnokite using Mössbauer spectroscopy at a range of temperatures and 1 bar. Our study represents a step towards understanding the electronic environment of iron in szomolnokite under compression at 300 K. Using a hydrostatic helium pressure-transmitting medium, we explored the pressure dependence of iron’s site-specific behavior in a synthetic szomolnokite powdered sample up to 95 GPa with time-domain synchrotron Mössbauer spectroscopy. At 1 bar, the Mössbauer spectrum is well described by two Fe²⁺-like sites and no ferric iron, consistent with select conventional Mössbauer spectra evaluations. At pressures below 19 GPa, steep gradients in the hyperfine parameters are most likely due to a structural phase transition. At 19 GPa, a fourth site is required to explain the time spectrum with increasing fractions of a low quadrupole splitting site, which could indicate the onset of another transition. Above 19 GPa we present three different models, including those with a high- to low-spin transition, that provide reasonable scenarios of electronic environment changes of the iron in szomolnokite with pressure. We summarize the complex range of Fe²⁺ spin transition characteristics at high-pressures by comparing szomolnokite with previous studies on ferrous-iron bearing phases

Granzyme A Required for Regulatory T-Cell Mediated Prevention of Gastrointestinal Graft-versus-Host Disease

In our previous work we could identify defects in human regulatory T cells (Tregs) likely favoring the development of graft-versus-host disease (GvHD) following allogeneic stem cell transplantation (SCT). Treg transcriptome analyses comparing GvHD and immune tolerant patients uncovered regulated gene transcripts highly relevant for Treg cell function. Moreover, granzyme A (GZMA) also showed a significant lower expression at the protein level in Tregs of GvHD patients. GZMA induces cytolysis in a perforin-dependent, FAS- FASL independent manner and represents a cell-contact dependent mechanism for Tregs to control immune responses. We therefore analyzed the functional role of GZMA in a murine standard model for GvHD. For this purpose, adoptively transferred CD4+CD25+ Tregs from gzmA-/- mice were analyzed in comparison to their wild type counterparts for their capability to prevent murine GvHD. GzmA-/- Tregs home efficiently to secondary lymphoid organs and do not show phenotypic alterations with respect to activation and migration properties to inflammatory sites. Whereas gzmA-/- Tregs are highly suppressive in vitro, Tregs require GZMA to rescue hosts from murine GvHD, especially regarding gastrointestinal target organ damage. We herewith identify GZMA as critical effector molecule of human Treg function for gastrointestinal immune response in an experimental GvHD model

A new mass stranding of false killer whale, Pseudorca crassidens, in the Strait of Magellan, Chile

We report the mass stranding of 46 false killer whales in the Strait of Magellan in February 2013. We present observation-based information about body size, sex, dental formula and necropsies. Sexual dimorphism in body length was clear, with males being significantly larger than females. Dental formula coincided with previous reports for the species, with asymmetry present in females. Individuals showed normal body conditions without any signs of apparent disease. The cause of the stranding remains unknown, however the coastal morphology hypothesis is a possible explanation.Fil: Haro, Daniela. Universidad de Chile; ChileFil: Aguayo Lobo, Anelio. Instituto Antártico Chileno; ChileFil: Blank, Olivia. Clínica Veterinaria Timaukel; ChileFil: Cifuentes, Constanza. Universidad Mayor; ChileFil: Dougnac, Catherine. Universidad de Chile; ChileFil: Arredondo, Cristóbal. Universidad de Chile; ChileFil: Pardo, Catalina. Universidad de Chile; ChileFil: Cáceres Saez, Iris. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin

Equity in evidence synthesis : you can’t play on broken strings

Peer reviewe

Using global remote camera data of a solitary species complex to evaluate the drivers of group formation

We would like to thank Megan Whatton, Belden Giman, Hongliang Bu, Dajun Wang, Fang Wang, Roland Kays, Jillian Kilborn, and New Hampshire Fish and Game for their roles in contributing data that was used in this analysis. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the US Government.Peer reviewe

Post-Franco Theatre

In the multiple realms and layers that comprise the contemporary Spanish theatrical landscape, “crisis” would seem to be the word that most often lingers in the air, as though it were a common mantra, ready to roll off the tongue of so many theatre professionals with such enormous ease, and even enthusiasm, that one is prompted to wonder whether it might indeed be a miracle that the contemporary technological revolution – coupled with perpetual quandaries concerning public and private funding for the arts – had not by now brought an end to the evolution of the oldest of live arts, or, at the very least, an end to drama as we know it

The PREDICTS database: a global database of how local terrestrial biodiversity responds to human impacts

Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species’ threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project – and avert – future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups – including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems – www.predicts.org.uk). We make site-level summary data available alongside this article. The full database will be publicly available in 2015

The Elastic, Electronic, and Structural Properties of Hydrous, Sulfur-Bearing Minerals in Planetary Environments: from the Surface to Deep Interiors

In this thesis, a comprehensive investigation of the hydrous iron endmember sulfate szomolnokite (FeSO₄·H₂O) has been conducted using a suite of complementary techniques to measure its structural, elastic, electronic, and vibrational properties under extreme conditions. Through X-ray diffraction (XRD), nuclear resonant inelastic X-ray scattering (NRIXS), synchrotron Mössbauer spectroscopy (SMS), and synchrotron Fourier transform infrared spectroscopy (FTIR) in the diamond anvil cell, the material properties of szomolnokite have been characterized under high pressures and low temperatures relevant to hydrous, sulfur-rich planetary environments. XRD measurements presented in this work have revealed two structural phase transitions occurring at pressures between 5.0 and 6.6 GPa and between 12.7 and 16.8 GPa, with the latter phase stable up to 80 GPa. The elastic parameters of each phase have been determined by fitting third-order Birch-Murnaghan equations of state. I compare our results with elastic parameters of other relevant sulfate phases, highlighting the importance of reporting and comparing these parameters at the pressures where the phases are stable. Using NRIXS and SMS, the lattice vibrational response and the effects on the iron electronic environments during the structural transitions are examined. The NRIXS and SMS data reveal distinct features and pressure-dependent behaviors that characterize alterations in both iron-site specific and bulk lattice properties associated with the phase transitions, including lattice softening and decreased iron-coordination environment symmetry. Utilizing both the NRIXS and XRD results, I discuss how the presence of sulfates in the ice-rich crusts of planetary bodies could affect tidal loading observations. Synchrotron FTIR measurements demonstrate that structurally bound H₂O is retained within the unit cell during the structural transitions and upon subsequent decompression, confirming the retention of water up to 23 GPa and temperatures as low as 20 K and indicating the reversibility of both structural transitions. Supported by our quantum mechanics molecular dynamics simulations, the existence of two vibrationally unique water sites in szomolnokite’s crystal structure is proposed to explain the experimentally observed H2O-related features. I develop a spectral diagnostic for observing the high pressure structural transformations at ambient and low temperatures. The measured partial phonon density of states, predicted vibrational density of states, and measured FTIR spectrum are compared. Drawing from the insights gained, we emphasize the advantages of employing complementary experimental and computational techniques and discuss future research directions that can further enhance our knowledge of hydrous, sulfur-rich planetary environments