1,267 research outputs found
Global sea level trends in the presence of variable sea level velocities, and variable accelerations
Author name used in this publication: X. L. Ding2013-2014 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Orientation of the geometrically best fitting triaxial lunar ellipsoid with respect to the mean earth/polar axis reference frame
Author name used in this publication: X. L. Ding2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Local antiferromagnetic exchange and collaborative Fermi surface as key ingredients of high temperature superconductors
Cuprates, ferropnictides and ferrochalcogenides are three classes of
unconventional high-temperature superconductors, who share similar phase
diagrams in which superconductivity develops after a magnetic order is
suppressed, suggesting a strong interplay between superconductivity and
magnetism, although the exact picture of this interplay remains elusive. Here
we show that there is a direct bridge connecting antiferromagnetic exchange
interactions determined in the parent compounds of these materials to the
superconducting gap functions observed in the corresponding superconducting
materials. High superconducting transition temperature is achieved when the
Fermi surface topology matches the form factor of the pairing symmetry favored
by local magnetic exchange interactions. Our result offers a principle guide to
search for new high temperature superconductors.Comment: 12 pages, 5 figures, 1 table, 1 supplementary materia
Large sulfur isotope fractionations in Martian sediments at Gale crater
Variability in the sulfur isotopic composition in sediments can reflect atmospheric, geologic and biological processes. Evidence for ancient fluvio-lacustrine environments at Gale crater on Mars and a lack of efficient crustal recycling mechanisms on the planet suggests a surface environment that was once warm enough to allow the presence of liquid water, at least for discrete periods of time, and implies a greenhouse effect that may have been influenced by sulfur-bearing volcanic gases. Here we report in situ analyses of the sulfur isotopic compositions of SO2 volatilized from ten sediment samples acquired by NASA’s Curiosity rover along a 13 km traverse of Gale crater. We find large variations in sulfur isotopic composition that exceed those measured for Martian meteorites and show both depletion and enrichment in 34S. Measured values of δ34S range from −47 ± 14‰ to 28 ± 7‰, similar to the range typical of terrestrial environments. Although limited geochronological constraints on the stratigraphy traversed by Curiosity are available, we propose that the observed sulfur isotopic signatures at Gale crater can be explained by equilibrium fractionation between sulfate and sulfide in an impact-driven hydrothermal system and atmospheric processing of sulfur-bearing gases during transient warm periods
Electronic Origin of High Temperature Superconductivity in Single-Layer FeSe Superconductor
The latest discovery of high temperature superconductivity signature in
single-layer FeSe is significant because it is possible to break the
superconducting critical temperature ceiling (maximum Tc~55 K) that has been
stagnant since the discovery of Fe-based superconductivity in 2008. It also
blows the superconductivity community by surprise because such a high Tc is
unexpected in FeSe system with the bulk FeSe exhibiting a Tc at only 8 K at
ambient pressure which can be enhanced to 38 K under high pressure. The Tc is
still unusually high even considering the newly-discovered intercalated FeSe
system A_xFe_{2-y}Se_2 (A=K, Cs, Rb and Tl) with a Tc at 32 K at ambient
pressure and possible Tc near 48 K under high pressure. Particularly
interesting is that such a high temperature superconductivity occurs in a
single-layer FeSe system that is considered as a key building block of the
Fe-based superconductors. Understanding the origin of high temperature
superconductivity in such a strictly two-dimensional FeSe system is crucial to
understanding the superconductivity mechanism in Fe-based superconductors in
particular, and providing key insights on how to achieve high temperature
superconductivity in general. Here we report distinct electronic structure
associated with the single-layer FeSe superconductor. Its Fermi surface
topology is different from other Fe-based superconductors; it consists only of
electron pockets near the zone corner without indication of any Fermi surface
around the zone center. Our observation of large and nearly isotropic
superconducting gap in this strictly two-dimensional system rules out existence
of node in the superconducting gap. These results have provided an unambiguous
case that such a unique electronic structure is favorable for realizing high
temperature superconductivity
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The northern hemisphere circumglobal teleconnection in a seasonal forecast model and its relationship to European summer forecast skill
Forecasting seasonal variations in European summer weather represents a considerable challenge. Here, we assess the performance of a seasonal forecasting model at representing a major mode of northern hemisphere summer climate variability, the circumglobal teleconnection (CGT), and the implications of errors in its representation on seasonal forecasts for the European summer (June, July, August). Using seasonal hindcasts initialised at the start of May, we find that the model skill for forecasting the interannual variability of 500 hPa geopotential height is poor, particularly over Europe and several other “centres of action” of the CGT. The model also has a weaker CGT pattern than is observed, particularly in August, when the observed CGT wavetrain is strongest. We investigate several potential causes of this poor skill. First, model variance in geopotential height in west-central Asia (an important region for the maintenance of the CGT) is lower than observed in July and August, associated with a poor representation of the link between this region and Indian monsoon precipitation. Second, analysis of the Rossby wave source shows that the source associated with monsoon heating is both too strong and displaced to the northeast in the model. This is related to errors in monsoon precipitation over the Bay of Bengal and Arabian Sea, where the model has more precipitation than is observed. Third, the model jet is systematically shifted northwards by several degrees latitude over large parts of the northern hemisphere, which may affect the propagation characteristics of Rossby waves in the model
Selective masking and demasking for the stepwise complexometric determination of aluminium, lead and zinc from the same solution
Background: A complexometric method based on selective masking and de-masking has been developed for the rapid determination of aluminium, lead and zinc from the same solution in glass and glass frit samples. The determination is carried out using potassium cyanide to mask zinc, and excess disodium salt of EDTA to mask lead and aluminium. The excess EDTA was titrated with standard Mn(II)SO(4) solution using Erichrome Black-T as the indicator. Subsequently selective de-masking agents - triethanolamine, 2,3-dimercaptopropanol and a formaldehyde/acetone mixture - were used to determine quantities of aluminium, lead and zinc in a stepwise and selective manner. Results: The accuracy of the method was established by analysing glass certified reference material NBS 1412. The standard deviation of the measurements, calculated by analysing five replicates of each sample, was found to be less than 1.5% for the method proposed. Conclusion: The novelty of the method lies in its simplicity and accuracy afforded by there not being a need for a prior separation or instrumentation. The proposed method was found to be highly selective for the precise determination of aluminum, zinc and lead in the routine analysis of glass batch and allied materials
Quantum corrections and black hole spectroscopy
In the work \cite{BRM,RBE}, black hole spectroscopy has been successfully
reproduced in the tunneling picture. As a result, the derived entropy spectrum
of black hole in different gravity (including Einstein's gravity,
Einstein-Gauss-Bonnet gravity and Ho\v{r}ava-Lifshitz gravity) are all evenly
spaced, sharing the same forms as , where physical process is only
confined in the semiclassical framework. However, the real physical picture
should go beyond the semiclassical approximation. In this case, the physical
quantities would undergo higher-order quantum corrections, whose effect on
different gravity shares in different forms. Motivated by these facts, in this
paper we aim to observe how quantum corrections affect black hole spectroscopy
in different gravity. The result shows that, in the presence of higher-order
quantum corrections, black hole spectroscopy in different gravity still shares
the same form as , further confirming the entropy quantum is universal
in the sense that it is not only independent of black hole parameters, but also
independent of higher-order quantum corrections. This is a desiring result for
the forthcoming quantum gravity theory.Comment: 14 pages, no figure, use JHEP3.cls. to be published in JHE
HLA-matched sibling transplantation with G-CSF mobilized PBSCs and BM decreases GVHD in adult patients with severe aplastic anemia
<p>Abstract</p> <p>Background</p> <p>Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective treatment for severe aplastic anemia (SAA). However, graft failure and graft-versus-host disease (GVHD) are major causes of the early morbidity in Allo-HSCT.</p> <p>Methods</p> <p>To reduce graft failure and GVHD, we treated fifteen patients with SAA using high- dose of HSCT with both G-CSF mobilized PB and BMSCs from HLA-identical siblings to treat patients with SAA.</p> <p>Results</p> <p>All patients had successful bone marrow engraftment. Only one patient had late rejection. Median time to ANC greater than 0.5 × 10<sup>9</sup>/L and platelet counts greater than 20 × 10<sup>9</sup>/L was 12 and 16.5 days, respectively. No acute GVHD was observed. The incidence of chronic GVHD was 6.67%. The total three-year probability of disease-free survival was 79.8%.</p> <p>Conclusion</p> <p>HSCT with both G-CSF mobilized PB and BMSCs is a promising approach for heavily transfused and/or allo-immunized patients with SAA.</p
A Conserved Mechanism for Control of Human and Mouse Embryonic Stem Cell Pluripotency and Differentiation by Shp2 Tyrosine Phosphatase
Recent studies have suggested distinctive biological properties and signaling mechanisms between human and mouse embryonic stem cells (hESCs and mESCs). Herein we report that Shp2, a protein tyrosine phosphatase with two SH2 domains, has a conserved role in orchestration of intracellular signaling cascades resulting in initiation of differentiation in both hESCs and mESCs. Homozygous deletion of Shp2 in mESCs inhibited differentiation into all three germ layers, and siRNA-mediated knockdown of Shp2 expression in hESCs led to a similar phenotype of impaired differentiation. A small molecule inhibitor of Shp2 enzyme suppressed both hESC and mESC differentiation capacity. Shp2 modulates Erk, Stat3 and Smad pathways in ES cells and, in particular, Shp2 regulates BMP4-Smad pathway bi-directionally in mESCs and hESCs. These results reveal a common signaling mechanism shared by human and mouse ESCs via Shp2 modulation of overlapping and divergent pathways
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