3,249 research outputs found
Non-equilibrium spin dynamics in a trapped Fermi gas with effective spin-orbit interaction
We consider a trapped atomic system in the presence of spatially varying
laser fields. The laser-atom interaction generates a pseudospin degree of
freedom (referred to simply as spin) and leads to an effective spin-orbit
coupling for the fermions in the trap. Reflections of the fermions from the
trap boundaries provide a physical mechanism for effective momentum relaxation
and non-trivial spin dynamics due to the emergent spin-orbit coupling. We
explicitly consider evolution of an initially spin-polarized Fermi gas in a
two-dimensional harmonic trap and derive non-equilibrium behavior of the spin
polarization. It shows periodic echoes with a frequency equal to the harmonic
trapping frequency. Perturbations, such as an asymmetry of the trap, lead to
the suppression of the spin echo amplitudes. We discuss a possible experimental
setup to observe spin dynamics and provide numerical estimates of relevant
parameters.Comment: 5 pages, 4 figures; published versio
Pheochromocytoma – clinical manifestations, diagnosis and current perioperative management
Pheochromocytoma is a neuroendocrine tumor characterized by the excessive production of catecholamines (epinephrine, norepinephrine, and dopamine). The diagnosis is suspected due to hypertensive paroxysms, associated with vegetative phenomena, due to the catecholaminergic hypersecretion. Diagnosis involves biochemical tests that reveal elevated levels of catecholamine metabolites (metanephrine and normetanephrine). Functional imaging, such as 123I-metaiodobenzylguanidine scintigraphy (123I-MIBG), has increased specificity in identifying the catecholamine-producing tumor and its metastases. The gold-standard treatment for patients with pheochromocytoma is represented by the surgical removal of the tumor. Before surgical resection, it is important to optimize blood pressure and intravascular volume in order to avoid negative hemodynamic events
EAST syndrome: Clinical, pathophysiological, and genetic aspects of mutations in KCNJ10
EAST syndrome is a recently described autosomal recessive disorder secondary to mutations in KCNJ10 (Kir4.1), a gene encoding a potassium channel expressed in the brain, eye, ear and kidney. This condition is characterized by 4 cardinal features; Epilepsy, Ataxia, Sensorineural deafness, and (a renal salt-wasting) Tubulopathy, hence the acronym EAST syndrome. Here we review reported clinical manifestations, in particular the neurological signs and symptoms which typically have the most impact on the quality of life of patients. In addition we review the pathophysiology and genetic aspects of the disease. So far 14 different KCNJ10 mutations have been published which either directly affect channel function or may lead to mislocalisation. Investigations of the pathophysiology may provide clues to potential treatments
Surface composition of BaTiO3/SrTiO3(001) films grown by atomic oxygen plasma assisted molecular beam epitaxy
We have investigated the growth of BaTiO3 thin films deposited on pure and 1%
Nb-doped SrTiO3(001) single crystals using atomic oxygen assisted molecular
beam epitaxy (AO-MBE) and dedicated Ba and Ti Knudsen cells. Thicknesses up to
30 nm were investigated for various layer compositions. We demonstrate 2D
growth and epitaxial single crystalline BaTiO3 layers up to 10 nm before
additional 3D features appear; lattice parameter relaxation occurs during the
first few nanometers and is completed at {\guillemotright}10 nm. The presence
of a Ba oxide rich top layer that probably favors 2D growth is evidenced for
well crystallized layers. We show that the Ba oxide rich top layer can be
removed by chemical etching. The present work stresses the importance of
stoichiometry and surface composition of BaTiO3 layers, especially in view of
their integration in devices.Comment: In press in J. Appl. Phy
Electronic and magnetic properties of metallic phases under coexisting short-range interaction and diagonal disorder
We study a three-dimensional Anderson-Hubbard model under the coexistence of
short-range interaction and diagonal disorder within the Hartree-Fock
approximation. We show that the density of states at the Fermi energy is
suppressed in the metallic phases near the metal-insulator transition as a
proximity effect of the soft Hubbard gap in the insulating phases. The
transition to the insulator is characterized by a vanishing DOS in contrast to
formation of a quasiparticle peak at the Fermi energy obtained by the dynamical
mean field theory in pure systems. Furthermore, we show that there exist frozen
spin moments in the paramagnetic metal.Comment: 4 pages, 2 figures, published versio
Founder mutation in KCNJ10 in Pakistani patients with EAST syndrome.
BACKGROUND: EAST syndrome is an autosomal recessive disorder caused by loss-of-function mutations in the gene KCNJ10. Among the 14 pathogenic mutations described so far, the p.R65P mutation stands out as the most frequent one and is particularly associated with patients of Pakistani origin. As a result we aimed to establish the existence of a potential founder effect in the Pakistani population. METHODS: To this end, we genotyped 12 patients from seven families and we compared disease haplotypes with ethnically matched control chromosomes. This haplotype was used together with demographic data for Pakistan to estimate the age of this founder mutation. RESULTS: We identified a small homozygous 0.694Â Mb region around the KCNJ10 p.R65P mutation that had identical haplotypes in all of the patients which were completely absent in the control sample. Based on current demographic data and knowledge about disease frequency, we estimate that this particular p.R65P mutation arose 20 generations (about 500Â years) ago. CONCLUSION: By knowing the prevalent mutation in a given population more efficient diagnostics can be performed and the families can benefit from specific counseling
Finite Temperature Density Instability at High Landau Level Occupancy
We study here the onset of charge density wave instabilities in quantum Hall
systems at finite temperature for Landau level filling . Specific
emphasis is placed on the role of disorder as well as an in-plane magnetic
field. Beyond some critical value, disorder is observed to suppress the charge
density wave melting temperature to zero. In addition, we find that a
transition from perpendicular to parallel stripes (relative to the in-plane
magnetic field) exists when the electron gas thickness exceeds \AA.
The perpendicular alignment of the stripes is in agreement with the
experimental finding that the easy conduction direction is perpendicular to the
in-plane field.Comment: 4 pages, 2 eps figures. We show explicitly that a transition from
perpendicular to parallel stripes (relative to the in-plane magnetic field)
exists when the electron gas thickness exceeds \AA. The
perpendicular alignment of the stripes is in agreement with the experimental
finding that the easy conduction direction is perpendicular to the in-plane
fiel
Role of disorder in half-filled high Landau levels
We study the effects of disorder on the quantum Hall stripe phases in
half-filled high Landau levels using exact numerical diagonalization. We show
that, in the presence of weak disorder, a compressible, striped charge density
wave, becomes the true ground state. The projected electron density profile
resembles that of a smectic liquid. With increasing disorder strength W, we
find that there exists a critical value, W_c \sim 0.12 e^2/\epsilon l, where a
transition/crossover to an isotropic phase with strong local electron density
fluctuations takes place. The many-body density of states are qualitatively
distinguishable in these two phases and help elucidate the nature of the
transition.Comment: 4 pages, 4 figure
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