GRACE gravity solutions validated by in-situ ocean bottom pressure in different regions of the global ocean

The GRACE satellite mission provides gravity field estimates of the Earth with unprecedented accuracy. Nevertheless,the realistic detection of oceanic mass redistribution remains challenging due to comparatively small signalamplitude, aliasing by tides and other short-term variability, and smoothing of small spatial scales. To verify thecapability of GRACE to measure oceanic mass variability, a validation with in-situ timeseries of Ocean BottomPressure (OBP) timeseries is essential.Here, different GRACE gravity fields provided by the GRACE Science Data System (CSR, GFZ, JPL), GRGS,ITG and others are compared with more than 140 timeseries of OBP sensors deployed throughout all oceans.The performance of the different GRACE products to capture oceanic mass variability is assessed by a weighedcorrelation analysis, taking into account the length and data quality of the in-situ time series. Both Gaussianfiltering and an ocean-model derived spatial pattern filtering method are used for the GRACE data, whereas forthe in-situ timeseries, different de-tiding and de-trending methods are applied to reduce aliasing and sensor drift.The analysis aims (a) to quantify the skill of different GRACE products and to quantify the advances made byrecent GRACE gravity field releases with improved data processing, and (b) to identify regions where GRACEperforms exceptionally well (e.g. high latitudes), and in which parts of the oceans GRACE fails to detect real OBPvariability. Spatial patterns related to the performance of GRACE may help to predict the quality of spacebornegravity measurements also for those oceanic regions where no in-situ data are available. This is critical for thefuture use of GRACE to remotely determine water mass redistribution in all oceans

A global Ocean Bottom Pressure data base as ground-truth reference for GRACE gravity field products

The GRACE satellite mission provides monthly estimates of the gravity field of the Earth. Differences between the monthly solutions are induced by mass redistribution on the Earth. Over the continents, the hydrological cycle represents the largest signals, which are readily observed by GRACE. Over the oceans, however, gravity field changes are about an order of magnitude smaller, close to the accuracy limits of the present GRACE solutions. Nevertheless, GRACE measurements may prove as an important tool to obtain integral estimates of water mass redistribution, sea level changes and geostrophic current variability. In order to validate and improve the gravity field products, GRACE is to be compared against ocean models and in-situ observations of Ocean Bottom Pressure (OBP). Time series of OBP sensors deployed by Alfred-Wegener-Institut in the Antarctic Circumpolar Current, as well as measurements from other locations of the global ocean are included in a OBP database that is currently under development at AWI, in close cooperation with Proudman Oceanographic Laboratory (POL, Liverpool). The mutual comparison of in-situ and ocean model data with different GRACE products provided by CSR, GFZ, GRGS, ITG and JPL will help to optimize data processing methods and corrections applied to GRACE, and to identify the performance of GRACE to detect oceanic mass flux variability in different regions of the global ocean

Periodic Variation of Stress in Sputter Deposited Si/WSi2 Multilayers

A tension increment after sputter deposition of 1 nm of WSi2 onto sputtered Si was observed at low Ar gas pressures. Wafer curvature data on multilayers were found to have a periodic variation corresponding to the multilayer period, and this permitted statistical analyses to improve the sensitivity to small stresses. The observation of tension instead of compression in the initial stage of growth is new and a model invoking surface rearrangement is invoked. The data also bear on an unusual surface smoothing phenomena for sputtered Si surfaces caused by the sputter deposition of WSi2 . We furthermore report that for low Ar pressures the Si layers are the predominant source of built-up stress

Pressure-dependent transition from atoms to nanoparticles in magnetron sputtering: Effect on WSi2 film roughness and stress

We report on the transition between two regimes from several-atom clusters to much larger nanoparticles in Ar magnetron sputter deposition of WSi2, and the effect of nanoparticles on the properties of amorphous thin films and multilayers. Sputter deposition of thin films is monitored by in situ x-ray scattering, including x-ray reflectivity and grazing incidence small angle x-ray scattering. The results show an abrupt transition at an Ar background pressure Pc; the transition is associated with the threshold for energetic particle thermalization, which is known to scale as the product of the Ar pressure and the working distance between the magnetron source and the substrate surface. Below Pc smooth films are produced, while above Pc roughness increases abruptly, consistent with a model in which particles aggregate in the deposition flux before reaching the growth surface. The results from WSi2 films are correlated with in situ measurement of stress in WSi2/Si multilayers, which exhibits a corresponding transition from compressive to tensile stress at Pc. The tensile stress is attributed to coalescence of nanoparticles and the elimination of nano-voids.Comment: 16 pages, 10 figures; v3: published versio

Conservation of DNA and ligand binding properties of retinoid X receptor from the placozoan Trichoplax adhaerens to human

Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Journal of Steroid Biochemistry and Molecular Biology 184 (2018): 3-10, doi:10.1016/j.jsbmb.2018.02.010.Nuclear receptors are a superfamily of transcription factors restricted to animals. These transcription factors regulate a wide variety of genes with diverse roles in cellular homeostasis, development, and physiology. The origin and specificity of ligand binding within lineages of nuclear receptors (e.g., subfamilies) continues to be a focus of investigation geared toward understanding how the functions of these proteins were shaped over evolutionary history. Among early-diverging animal lineages, the retinoid X receptor (RXR) is first detected in the placozoan, Trichoplax adhaerens. To gain insight into RXR evolution, we characterized ligand- and DNA-binding activity of the RXR from T. adhaerens (TaRXR). Like bilaterian RXRs, TaRXR specifically bound 9-cis-retinoic acid, which is consistent with a recently published result and supports a conclusion that the ancestral RXR bound ligand. DNA binding site specificity of TaRXR was determined through protein binding microarrays (PBMs) and compared with human RXR. The binding sites for these two RXR proteins were broadly conserved (~85% shared high-affinity sequences within a targeted array), suggesting evolutionary constraint for the regulation of downstream genes. We searched for predicted binding motifs of the T. adhaerens genome within 1000 bases of annotated genes to identify potential regulatory targets. We identified 648 unique protein coding regions with predicted TaRXR binding sites that had diverse predicted functions, with enriched processes related to intracellular signal transduction and protein transport. Together, our data support hypotheses that the original RXR protein in animals bound a ligand with structural similarity to 9-cis-retinoic acid; the DNA motif recognized by RXR has changed little in more than 1 billion years of evolution; and the suite of processes regulated by this transcription factor diversified early in animal evolution.Support for AMT was provided by the Tropical Research Initiative and an Internal Research and Development Award from the Woods Hole Oceanographic Institution. AMR was supported by NIH award R15GM114740. JM was supported by NSF award 1536530 to AMR. DM-P, BF and FMS were supported by NIH award R01DK094707 to FMS

Exciton spectroscopy of hexagonal boron nitride using non-resonant x-ray Raman scattering

We report non-resonant x-ray Raman scattering (XRS) measurements from hexagonal boron nitride for transferred momentum from 2 to 9 $\mathrm{\AA}^{-1}$ along directions both in and out of the basal plane. A symmetry-based argument, together with real-space full multiple scattering calculations of the projected density of states in the spherical harmonics basis, reveals that a strong pre-edge feature is a dominantly $Y_{10}$-type Frenkel exciton with no other \textit{s}-, \textit{p}-, or \textit{d}- components. This conclusion is supported by a second, independent calculation of the \textbf{q}-dependent XRS cross-section based on the Bethe-Salpeter equation

Hard x ray spectroscopy and imaging by a reflection zone plate in the presence of astigmatism

The feasibility of an off axis x ray reflection zone plate to perform wavelength dispersive spectroscopy, on axis point focusing, and two dimensional imaging is demonstrated by means of one and the same diffractive optical element DOE at a synchrotron radiation facility. The resolving power varies between 30 and 400 in the range of 7.6 keV to 9.0 keV, with its maximum at the design energy of 8.3 keV. This result is verified using an adjustable entrance slit, by which horizontal H and vertical V focusing to 0.85 amp; 956;m H and 1.29 amp; 956;m V is obtained near the sagittal focal plane of the astigmatic configuration. An angular and axial scan proves an accessible field of view of at least 0.6 arcmin 0.8 arcmin and a focal depth of plus minus 0.86 mm. Supported by the grating efficiency of around 17.5 and a very short pulse elongation, future precision x ray fluorescence and absorption studies of transition metals at their K edge on an ultrashort timescale could benefit from our finding

Potential predictability of rapid changes in the Atlantic meridional overturning circulation

We explore the potential predictability of rapid changes in the Atlantic meridional overturning circulation (MOC) using a coupled global climate model (HadCM3). Rapid changes in the temperature and salinity of surface water in the Nordic Seas, and the flow of dense water through Denmark Strait, are found to be precursors to rapid changes in the model's MOC, with a lead time of around 10 years. The mechanism proposed to explain this potential predictability relies on the development of density anomalies in the Nordic Seas which propagate through Denmark Strait and along the deep western boundary current, affecting the overturning. These rapid changes in the MOC have significant, and widespread, climate impacts which are potentially predictable a few years ahead. Whilst the flow through Denmark Strait is too strong in HadCM3, the presence of such potential predictability motivates the monitoring of water properties in the Nordic Seas and Denmark Strait

Hydroxyurea lowers the frequency of sickle cell vaso-occlusive crises

A critical appraisal and clinical application of Charache S, Terrin ML, Moore RD, et al. Effect of hydroxyurea on the frequency of painful crises in sickle cell anemia. N Engl J Med 1995;(332):1317-1322 doi: 10.1056/nejm19950518332200