Juniper from Ethiopia contains a large-scale precipitation signal

Most semiarid regions are facing an increasing scarcity of woody vegetation due mainly to anthropogenic deforestation aggravated by climate changes. However, there is insufficient information to reconstruct past changes in climate and to evaluate the implications of future climate changes on the vegetation. Tree-ring analysis is a powerful tool for studying tree age, population dynamics, growth behavior, and climate-growth relationships among tropical tree species and for gaining information about the environmental forces driving growth change as well as for developing proxies for climate reconstruction. Wood anatomical and dendrochronological methods were used on Juniperus procera trees from two Ethiopian highland forests to check (i) whether tree-ring series of juniper are cross-datable and hence suitable for building tree-ring chronologies, and if so, (ii) which climate factors mainly drive wood formation in juniper from this region. Visible growth layers of the juniper wood were shown to be annual rings. Tree-ring sequences could be cross-dated between trees growing at the same site and between trees growing at sites 350 km apart. Evidence was found that annual growth of junipers is mainly controlled by one climatic factor, precipitation. This strong precipitation influence proves the potential of African juniper chronologies for accurate climate reconstruction and points out the relevance of building a network of juniper chronologies across East Africa

Interplay of Chemical, Electronic, and Structural Effects in the Triple-Conducting BaFeO3-Ba(Zr,Y)O3 Solid Solution

Triple-conducting oxides with mobile protons, oxygen vacancies, and holes are key functional materials for protonic ceramic fuel/electrolysis cells. We comprehensively investigate the Ba(Zr,Y,Fe)O3-delta perovskite solid solution series ranging from electrolyte to electrode-type materials depending on iron content. From thermogravimetry and impedance spectroscopy, the proton and oxygen vacancy concentrations as well as electronic and ionic conductivities are determined. X-ray spectroscopy (Fe K-edge XANES, O K-edge Raman scattering, Fe, Zr, Y K-edge EXAFS) elucidates the finer features of the electronic structure and local distortions. A low Fe content of <= 10% strongly decreases the degree of hydration, while comparably high Fe concentrations of >= 70% are required to obtain an electronic conductivity sufficient for an electrode material. The transport of ionic and electronic carriers is interrelated in a complex way and is closely linked to details of the electronic structure (strength of Fe-O hybridization) and geometrical distortions (Fe-O-Fe and Fe-O-(Zr,Y) buckling). As a result, an optimum combination of proton concentration and electronic conductivity is not obtained in the middle of the solid solution series but rather found for Fe-rich materials with 20-30% doping with oversized, redox-inactive cations. A similar behavior is also expected for related solid solutions between a large-band gap electrolyte and small-band gap redox-active perovskites

Oxygen vacancy clusters in bulk cerium oxide and the impact of gold atoms

Ceria is important for catalysis due to its ability to form and utilize oxygen vacancies during redox reactions. Understanding the dynamic formation of the oxygen vacancies has contributed to the development of efficient catalytic processes. Here, we demonstrate the presence of oxygen vacancy clusters in the bulk of ceria and gold/ceria catalysts upon anaerobic carbon monoxide oxidation and describe their interplay with the orbital hybridization of Ce3+ 4f and 5d states. Observations are made using in situ X-ray Raman scattering spectroscopy at O K-and Ce N4,5-edges and in situ X-ray diffraction. These, combined with multiplet calculations, allow detection of the formation of Ce3+ in gold/ceria upon low temperature carbon monoxide oxidation. The modifications observed at the O K-edge reflect the rearrangement of the bulk oxygen sublattice. Density-functional theory calculations show vacancy ordering in the bulk, and explain modifications at the O K-edge, involving the hybridization of the Ce 4f and 5d and O 2p orbitals

Reduction of Sunburn Damage to Skin by Topical Application of Vitamin E Acetate Following Exposure to Ultraviolet B Radiation: Effect of Delaying Application or of Reducing Concentration of Vitamin E Acetate Applied

The skin of the skh-1 mouse after ultraviolet B (280-320 nm, UVB) irradiation shows the pathological changes typical of sunburn damage: spongiosis (edematous spaces) around some cells, necrosis of keratinocytes, giving rise to sunburn cells, inflammatory infiltration ofpolymorphonuclear leucocytes, etc. In our previous study, these were accompanied by erythema, increased skin sensitivity, and edematous swelling. The topical application of tocopherol acetate (TA) immediately after the UVB exposure decreased these changes. In this paper, multiple measurements of the skin thickness were made at different locations along the magnetic resonance imaging (MRI) cross-sectional image of the skin. This permits effects to be quantified with (if desired) the contralateral half of the back serving as an internal control, either exposed (positive control) or unexposed (negative control). Topical application of TA resulted in an increase in the concentration of free tocopherol in the skin. No qualitative differences in ultrastructural appearance of the DVB-irradiated, TA-treated skin could be discerned by careful examination. In vivo high resolution video microscopy of blood flow in venules of the irradiated mouse ear revealed a large (tenfold) but not statistically significant decrease in stationary lymphocytes adhering to the venule walls. The delaying of the application of TA up to 8 hours after the termination of UVB irradiation still offered statistically significant protection as did immediate application of 5% TA in diluent Myritol 318 (Delios S, Henkel)

Hydration in aqueous osmolyte solutions: the case of TMAO and urea

The hydration and hydrogen-bond topology of small water solvated molecules such as the naturally occurring organic osmolytes trimethylamine N-oxide (TMAO) and urea are under intense investigation. We aim at furthering the understanding of this complex hydration by combining experimental oxygen K-edge excitation spectra with results from spectra calculated via the Bethe-Salpeter equation based on structures obtained from ab initio molecular dynamics simulations. Comparison of experimental and calculated spectra allows us to extract detailed information about the immediate surrounding of the solute molecules in the solvated state. We quantify and localize the influence of the solute on the hydrogen bond network of the water solvent and find spectroscopic fingerprints of a clear directional asymmetry around TMAO with strong and local kosmotropic influence around TMAO's NO head group and slight chaotropic influence around the hydrophobic methyl groups. The influence of urea on the local water network is qualitatively similar to that of TMAO but weaker in magnitude. The strongest influence of both molecules on the shape of the oxygen K-edge spectra is found in the first hydration shells

A large-solid-angle X-ray Raman scattering spectrometer at ID20 of the European Synchrotron Radiation Facility

An end-station for X-ray Raman scattering spectroscopy at beamline ID20 of the European Synchrotron Radiation Facility is described. This end-station is dedicated to the study of shallow core electronic excitations using non-resonant inelastic X-ray scattering. The spectrometer has 72 spherically bent analyzer crystals arranged in six modular groups of 12 analyzer crystals each for a combined maximum flexibility and large solid angle of detection. Each of the six analyzer modules houses one pixelated area detector allowing for X-ray Raman scattering based imaging and efficient separation of the desired signal from the sample and spurious scattering from the often used complicated sample environments. This new end-station provides an unprecedented instrument for X-ray Raman scattering, which is a spectroscopic tool of great interest for the study of low-energy X-ray absorption spectra in materials under insitu conditions, such as inoperando batteries and fuel cells, insitu catalytic reactions, and extreme pressure and temperature conditions.Peer reviewe

LDL aggregation susceptibility is higher in healthy South Asian compared with white Caucasian men

BACKGROUND: South Asians are more prone to develop atherosclerotic cardiovascular disease (ASCVD) compared with white Caucasians, which is not fully explained by classical risk factors. We recently reported that the presence of aggregation-prone low-density lipoprotein (LDL) in the circulation is associated with increased ASCVD mortality. OBJECTIVE: We hypothesized that LDL of South Asians is more prone to aggregate, which may be explained by differences in their LDL lipid composition. METHODS: In this cross-sectional hypothesis-generating study, LDL was isolated from plasma of healthy South Asians (n = 12) and age- and BMI-matched white Caucasians (n = 12), and its aggregation susceptibility and lipid composition were analyzed. RESULTS: LDL from South Asians was markedly more prone to aggregate compared with white Caucasians. Among all measured lipids, sphingomyelin 24:0 and triacylglycerol 56:8 showed the highest positive correlation with LDL aggregation. In addition, LDL from South Asians was enriched in arachidonic acid containing phosphatidylcholine 38:4 and had less phosphatidylcholines and cholesteryl esters containing monounsaturated fatty acids. Interestingly, body fat percentage, which was higher in South Asians (+26%), positively correlated with LDL aggregation and highly positively correlated with triacylglycerol 56:8, sphingomyelin 24:0, and total sphingomyelin. CONCLUSIONS: LDL aggregation susceptibility is higher in healthy young South Asians compared with white Caucasians. This may be partly explained by the higher body fat percentage of South Asians, leading to sphingomyelin enrichment of LDL. We anticipate that the presence of sphingomyelin-rich, aggregation -prone LDL particles in young South Asians may increase LDL accumulation in the arterial wall and thereby contribute to their increased risk of developing ASCVD later in life. (C) 2019 National Lipid Association. Published by Elsevier Inc.Peer reviewe

X-ray Raman scattering : An exciting tool for the study of matter at conditions of the Earth's interior

Volume: 425The study of minerals and melts at in situ conditions is highly relevant to understand the physical and chemical properties of the Earth's crust and mantle. Here, x-ray Raman scattering provides a valuable tool to investigate the local atomic and electronic structure of Earth materials consisting predominantly of low Z elements at high pressures and temperatures. The capabilities of x-ray Raman scattering to investigate silicate minerals, glasses, and melts are discussed and the application of the method to in situ studies of silicate melts using a hydrothermal diamond anvil cell is demonstrated.Non peer reviewe

Earliest stone-tipped projectiles from the Ethiopian Rift date to> 279,000 years ago

Projectile weapons (i.e. those delivered from a distance) enhanced prehistoric hunting efficiency by enabling higher impact delivery and hunting of a broader range of animals while reducing confrontations with dangerous prey species. Projectiles therefore provided a significant advantage over thrusting spears. Composite projectile technologies are considered indicative of complex behavior and pivotal to the successful spread of Homo sapiens . Direct evidence for such projectiles is thus far unknown from >80,000 years ago. Data from velocity-dependent microfracture features, diagnostic damage patterns, and artifact shape reported here indicate that pointed stone artifacts from Ethiopia were used as projectile weapons (in the form of hafted javelin tips) as early as >279,000 years ago. In combination with the existing archaeological, fossil and genetic evidence, these data isolate eastern Africa as a source of modern cultures and biology

RIXS observation of bond-directional nearest-neighbor excitations in the Kitaev material Na2_2IrO3_3

Spin-orbit coupling locks spin direction and spatial orientation and generates, in semi-classical magnets, a local spin easy-axis and associated ordering. Quantum spin-1/2's defy this fate: rather than spins becoming locally anisotropic, the spin-spin interactions do. Consequently interactions become dependent on the spatial orientation of bonds between spins, prime theoretical examples of which are Kitaev magnets. Bond-directional interactions imply the existence of bond-directional magnetic modes, predicted spin excitations that render crystallographically equivalent bonds magnetically inequivalent, which yet have remained elusive experimentally. Here we show that resonant inelastic x-ray scattering allows us to explicitly probe the bond-directional character of magnetic excitations. To do so, we use a scattering plane spanned by one bond and the corresponding spin component and scan a range of momentum transfer that encompasses multiple Brillouin zones. Applying this approach to Na$_2$IrO$_3$ we establish the different bond-directional characters of magnetic excitations at 10 meV and 45 meV. Combined with the observation of spin-spin correlations that are confined to a single bond, this experimentally validates the Kitaev character of exchange interactions long proposed for this material.Comment: 6 pages, 5 figures, plus 4 pages Supplementary Information (incl. 5 figures