110 research outputs found
Interplay of the electronic and lattice degrees of freedom in A_{1-x}Fe_{2-y}Se_{2} superconductors under pressure
The local structure and electronic properties of RbFeSe
are investigated by means of site selective polarized x-ray absorption
spectroscopy at the iron and selenium K-edges as a function of pressure. A
combination of dispersive geometry and novel nanodiamond anvil pressure-cell
has permitted to reveal a step-like decrease in the Fe-Se bond distance at
GPa. The position of the Fe K-edge pre-peak, which is directly
related to the position of the chemical potential, remains nearly constant
until GPa, followed by an increase until GPa. Here, as in
the local structure, a step-like decrease of the chemical potential is seen.
Thus, the present results provide compelling evidence that the origin of the
reemerging superconductivity in FeSe in vicinity of a
quantum critical transition is caused mainly by the changes in the electronic
structure
Interplay between local structure and electronic properties on CuO under pressure
The electronic and local structural properties of CuO under pressure have
been investigated by means of X-ray absorption spectroscopy (XAS) at Cu K edge
and ab-initio calculations, up to 17 GPa. The crystal structure of CuO consists
of Cu motifs within CuO square planar units and two elongated apical Cu-O
bonds. The CuO square planar units are stable in the studied pressure
range, with Cu-O distances that are approximately constant up to 5 GPa, and
then decrease slightly up to 17 GPa. In contrast, the elongated Cu-O apical
distances decrease continuously with pressure in the studied range. An
anomalous increase of the mean square relative displacement (EXAFS Debye
Waller, \sigma) of the elongated Cu-O path is observed from 5 GPa up to 13
GPa, when a drastic reduction takes place in \sigma. This is interpreted in
terms of local dynamic disorder along the apical Cu-O path. At higher pressures
(P>13 GPa), the local structure of Cu changes from a 4-fold square
planar to a 4+2 Jahn-Teller distorted octahedral ion. We interpret these
results in terms of the tendency of the Cu ion to form favorable
interactions with the apical O atoms. Also, the decrease in Cu-O apical
distance caused by compression softens the normal mode associated with the
out-of-plane Cu movement. CuO is predicted to have an anomalous rise in
permittivity with pressure as well as modest piezoelectricity in the 5-13 GPa
pressure range. In addition, the near edge features in our XAS experiment show
a discontinuity and a change of tendency at 5 GPa. For P < 5 GPa the evolution
of the edge shoulder is ascribed to purely electronic effects which also affect
the charge transfer integral. This is linked to a charge migration from the Cu
to O, but also to an increase of the energy band gap, which show a change of
tendency occurring also at 5 GPa
Novel stable structure of Li3PS4 predicted by evolutionary algorithm under high-pressure
By combining theoretical predictions and in-situ X-ray diffraction under high pressure, we found a novel stable crystal structure of Li3PS4 under high pressures. At ambient pressure, Li3PS4 shows successive structural transitions from γ-type to β-type and from β-type to α type with increasing temperature, as is well established. In this study, an evolutionary algorithm successfully predicted the γ-type crystal structure at ambient pressure and further predicted a possible stable δ-type crystal structures under high pressure. The stability of the obtained structures is examined in terms of both static and dynamic stability by first-principles calculations. In situ X-ray diffraction using a synchrotron radiation revealed that the high-pressure phase is the predicted δ-Li3PS4 phase
Relationships between biomarkers of cartilage, bone, synovial metabolism and knee pain provide insights into the origins of pain in early knee osteoarthritis
Socioeconomic status and self-rated health of Japanese people, based on age, cohort, and period
Visuomotor Cerebellum in Human and Nonhuman Primates
In this paper, we will review the anatomical components of the visuomotor cerebellum in human and, where possible, in non-human primates and discuss their function in relation to those of extracerebellar visuomotor regions with which they are connected. The floccular lobe, the dorsal paraflocculus, the oculomotor vermis, the uvula–nodulus, and the ansiform lobule are more or less independent components of the visuomotor cerebellum that are involved in different corticocerebellar and/or brain stem olivocerebellar loops. The floccular lobe and the oculomotor vermis share different mossy fiber inputs from the brain stem; the dorsal paraflocculus and the ansiform lobule receive corticopontine mossy fibers from postrolandic visual areas and the frontal eye fields, respectively. Of the visuomotor functions of the cerebellum, the vestibulo-ocular reflex is controlled by the floccular lobe; saccadic eye movements are controlled by the oculomotor vermis and ansiform lobule, while control of smooth pursuit involves all these cerebellar visuomotor regions. Functional imaging studies in humans further emphasize cerebellar involvement in visual reflexive eye movements and are discussed
A mindfulness-based stress management program and treatment with omega-3 fatty acids to maintain a healthy mental state in hospital nurses (Happy Nurse Project): study protocol for a randomized controlled trial
Tandem mass spectrometric strategies for determination of sulfation positions and uronic acid epimerization in chondroitin sulfate oligosaccharides
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