9,789 research outputs found
Dimerization-Induced Fermi-Surface Reconstruction in IrTe2
We report a de Haas-van Alphen (dHvA) oscillation study on IrTe2 single crystals showing complex dimer formations. By comparing the angle dependence of dHvA oscillations with band structure calculations, we show distinct Fermi surface reconstruction induced by a 1/5-type and a 1/8-type dimerizations. This verifies that an intriguing quasi-two-dimensional conducting plane across the layers is induced by dimerization in both cases. A phase transition to the 1/8 phase with higher dimer density reveals that local instabilities associated with intra-and interdimer couplings are the main driving force for complex dimer formations in IrTe2.X11149sciescopu
Remotely Sensed Northern Vegetation Response to Changing Climate: Growing Season and Productivity Perspective
Vegetation growing season and maximum photosynthetic state determine spatiotemporal variability of seasonal total gross primary productivity of vegetation. Recent warming induced impacts accelerate shifts on growing season and physiological status over Northern vegetated land. Thus, understanding and quantifying these changes are very important. Here, we first investigate how vegetation growing season and maximum photosynthesis state are evolved and how such components contribute on inter-annual variation of seasonal total gross primary productivity. Furthermore, seasonally different response of northern vegetation to changing temperature and water availability is also investigated. We utilized both long-term remotely sensed data to extract larger scale growing season metrics (growing season start, end and duration) and productivity (i.e., growing season summed vegetation index, GSSVI) for answering these questions. We find that regionally diverged growing season shift and maximum photosynthetic state contribute differently characterized productivity inter-annual variability and trend. Also seasonally different response of vegetation gives different view of spatially varying interaction between vegetation and climate. These results highlight spatially and temporally varying vegetation dynamics and are reflective of biome-specific responses of northern vegetation to changing climate
Anomalous He-Gas High-Pressure Studies on Superconducting LaO1-xFxFeAs
AC susceptibility measurements have been carried out on superconducting
LaO1-xFxFeAs for x=0.07 and 0.14 under He-gas pressures to about 0.8 GPa. Not
only do the measured values of dTc/dP differ substantially from those obtained
in previous studies using other pressure media, but the Tc(P) dependences
observed depend on the detailed pressure/temperature history of the sample. A
sizeable sensitivity of Tc(P) to shear stresses provides a possible
explanation
Fast synthesis of platinum nanopetals and nanospheres for highly-sensitive non-enzymatic detection of glucose and selective sensing of ions
Novel methods to obtain Pt nanostructured electrodes have raised particular interest due to their high performance in electrochemistry. Several nanostructuration methods proposed in the literature use costly and bulky equipment or are time-consuming due to the numerous steps they involve. Here, Pt nanostructures were produced for the first time by one-step template-free electrodeposition on Pt bare electrodes. The change in size and shape of the nanostructures is proven to be dependent on the deposition parameters and on the ratio between sulphuric acid and chloride-complexes (i.e., hexachloroplatinate or tetrachloroplatinate). To further improve the electrochemical properties of electrodes, depositions of Pt nanostructures on previously synthesised Pt nanostructures are also performed. The electroactive surface areas exhibit a two order of magnitude improvement when Pt nanostructures with the smallest size are used. All the biosensors based on Pt nanostructures and immobilised glucose oxidase display higher sensitivity as compared to bare Pt electrodes. Pt nanostructures retained an excellent electrocatalytic activity towards the direct oxidation of glucose. Finally, the nanodeposits were proven to be an excellent solid contact for ion measurements, significantly improving the time-stability of the potential. The use of these new nanostructured coatings in electrochemical sensors opens new perspectives for multipanel monitoring of human metabolism
Adsorption-controlled growth of La-doped BaSnO3 by molecular-beam epitaxy
Epitaxial La doped BaSnO3 films were grown in an adsorption controlled regime
by molecular beam epitaxy, where the excess volatile SnOx desorbs from the film
surface. A film grown on a (001) DyScO3 substrate exhibited a mobility of 183
cm^2 V^-1 s^-1 at room temperature and 400 cm^2 V^-1 s^-1 at 10 K, despite the
high concentration (1.2x10^11 cm^-2) of threading dislocations present. In
comparison to other reports, we observe a much lower concentration of (BaO)2
Ruddlesden Popper crystallographic shear faults. This suggests that in addition
to threading dislocations that other defects possibly (BaO)2 crystallographic
shear defects or point defects significantly reduce the electron mobility
"Water-cycle" mechanism for writing and erasing nanostructures at the LaAlO3/SrTiO3 interface
Nanoscale control of the metal-insulator transition in LaAlO3/ SrTiO3
heterostructures can be achieved using local voltages applied by a conductive
atomic-force microscope probe. One proposed mechanism for the writing and
erasing process involves an adsorbed H2O layer at the top LaAlO3 surface. In
this picture, water molecules dissociates into OH- and H+ which are then
selectively removed by a biased AFM probe. To test this mechanism, writing and
erasing experiments are performed in a vacuum AFM using various gas mixtures.
Writing ability is suppressed in those environments where H2O is not present.
The stability of written nanostructures is found to be strongly associated with
the ambient environment. The self-erasure process in air can be strongly
suppressed by creating a modest vacuum or replacing the humid air with dry
inert gas. These experiments provide strong constraints for theories of both
the writing process as well as the origin of interfacial conductance.Comment: 11 pages, 3 figure
Stellar kinematics and populations out to 1.5 effective radius in the elliptical galaxy NGC4636
We present high quality long slit spectra along the major and minor axes out
to 1.5 effective radius () of the massive galaxy NGC4636 taken by
Hobby-Eberly Telescope (HET). Using Fourier Correlation Quotient (FCQ) method,
we measured the stellar line-of-sight velocity distribution along the axes.
Furthermore, six Lick/IDS indices
() are derived from the
clean spectrum. By comparing the measured absorption line strengths with the
predictions of Simple Stellar Populations (SSP) models, we derived ages, total
metallicity and abundance profiles of the galaxy. This galaxy presents
old and over abundant stellar populations. Indeed, using the SSP
model, we obtained the broadband color profiles. The theoretical colors match
well with the measured colors and present red sharp peaks at the galaxy center.
The sharp peaks of the colors are mainly shaped by the high metallicity in the
galaxy center. Interestingly, the galaxy has steep negative metallicity
gradients, but trend flattens outwards. This result likly suggests that the
center and outer regions of the galaxy formed through different formation
process.Comment: 14 pages, 7 figures, accepted by RA
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Myricetin, the main flavonoid in Syzygium cumini leaf, is a novel inhibitor of platelet thiol isomerases PDI and ERp5
Background: Flavonoids have been characterized as a prominent class of compounds to treat thrombotic diseases through the inhibition of thiol isomerases. Syzygium cumini is a flavonoid-rich medicinal plant that contains myricetin and gallic acid. Little is known about the potential anti-platelet properties of S. cumini and its constituent flavonoids.
Objective
To evaluate the anti-platelet effects and mechanism of action of a polyphenol-rich extract (PESc) from S. cumini leaf and its most prevalent polyphenols, myricetin and gallic acid.
Methods
PESc, myricetin and gallic acid were incubated with platelet-rich plasma and washed platelets to assess platelet aggregation and activation. In vitro platelet adhesion and thrombus formation as well as in vivo bleeding time were performed. Finally, myricetin was incubated with recombinant thiol isomerases to assess its potential to bind and inhibit these, whilst molecular docking studies predicted possible binding sites.
Results:
PESc decreased platelet activation and aggregation induced by different agonists. Myricetin exerted potent anti-platelet effects, whereas gallic acid did not. Myricetin reduced the ability of platelets to spread on collagen, form thrombi in vitro without affecting haemostasis in vivo. Fluorescence quenching studies suggested myricetin binds to different thiol isomerases with similar affinity, despite inhibiting only protein disulphide isomerase (PDI) and ERp5 reductase activities (IC50~3.5 μM). Finally, molecular docking studies suggested myricetin formed non-covalent bonds with PDI and ERp5.
Conclusions:
PESc and its most abundant flavonoid myricetin strongly inhibit platelet function. Additionally, myricetin is a novel inhibitor of ERp5 and PDI, unveiling a new therapeutic perspective for the treatment of thrombotic disorders
High mobility, hole transport materials for highly efficient PEDOT:PSS replacement in inverted perovskite solar cells
The authors thank KAUST for financial support and acknowledge EC FP7 Project SC2 (610115) EC H2020 (643791), and EPSRC Projects EP/G037515/1, EP/M024873/1 and EP/M005143/1
Dark Matter: The Leptonic Connection
Recent observatons of high-energy positrons and electrons by the PAMELA and
ATIC experiments may be an indication of the annihilation of dark matter into
leptons and not quarks. This leptonic connection was foreseen already some
years ago in two different models of radiative neutrino mass. We discuss here
the generic interactions (nu eta^0 - l eta^+) chi and l^c zeta^- chi^c which
allow this to happen, where chi and/or chi^c are fermionic dark-matter
candidates. We point out in particular the importance of chi chi to l^+ l^-
gamma to both positron and gamma-ray signals within this framework.Comment: 4 pages, 5 figures. v2: PLB versio
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