Decay of multiply charged vortices at nonzero temperatures

We study the instability of multiply charged vortices in the presence of thermal atoms and find various scenarios of splitting of such vortices. The onset of the decay of a vortex is always preceded by the increase of a number of thermal (uncondensed) atoms in the system and manifests itself by the sudden rise of the amplitude of the oscillations of the quadrupole moment. Our calculations show that the decay time gets shorter when the multiplicity of a vortex becomes higher.Comment: 4 pages, 6 figure

Investigation of fMRI activation in the internal capsule

<p>Abstract</p> <p>Background</p> <p>Functional magnetic resonance imaging (fMRI) in white matter has long been considered controversial. Recently, this viewpoint has been challenged by an emerging body of evidence demonstrating white matter activation in the corpus callosum. The current study aimed to determine whether white matter activation could be detected outside of the corpus callosum, in the internal capsule. Data were acquired from a 4 T MRI using a specialized asymmetric spin echo spiral sequence. A motor task was selected to elicit activation in the posterior limb of the internal capsule.</p> <p>Results</p> <p>White matter fMRI activation was examined at the individual and group levels. Analyses revealed that activation was present in the posterior limb of the internal capsule in 80% of participants. These results provide further support for white matter fMRI activation.</p> <p>Conclusions</p> <p>The ability to visualize functionally active tracts has strong implications for the basic scientific study of connectivity and the clinical assessment of white matter disease.</p

Orbital-selective Mott phase and spin nematicity in Ni-substituted FeTe0.65_{0.65}Se0.35_{0.35} single crystals

The normal state in iron chalcogenides is metallic but highly unusual, with orbital and spin degrees of freedom partially itinerant or localized depending on temperature, leading to many unusual features. In this work, we report on the observations of two of such features, the orbital selective Mott phase (OSMP) and spin nematicity, evidenced in magnetization and magnetotransport [resistivity, Hall effect, angular magnetoresistance (AMR)] of Ni-substituted FeTe$_{0.65}$Se$_{0.35}$ single crystals. Two series of single crystals Fe$_{1+{\delta}-y}$Ni$_y$Te$_{0.65}$Se$_{0.35}$ were prepared, with $0 < y < 0.2$, and $\delta$ either positive (S crystals) or negative (F crystals), depending on the crystallization rate. The S crystals, with single, tetragonal phase exhibit superconducting (SC) properties inferior to F crystals, which contain Fe vacancy-rich monoclinic inclusions. Substitution of Ni dopes both types of crystals with electrons, what eliminates some of the hole pockets from Fermi level, leaving only one, originating from $d_{xy}$ orbital. We show that electron-dominated transport, observed at low $T$ at large $y$, is replaced by hole-dominated transport at $T > 180$ K, suggesting direct link with the appearance of the $d_{z^2}$ hole pockets at X points of the Brillouin zone in the OSMP phase, as recently reported by angular resolved photoemission experiments (Commun. Phys. 5, 29 (2022)). The AMR of S crystals shows the $C_4$ rotational symmetry of in-plane magnetocrystalline anisotropy at small $y$, replaced by $C_2$ symmetry at intermediate $y$, indicating development of Ni doping-induced spin nematicity. The $C_4$ symmetry is preserved in F crystals due to microstructural disorder related to vacancy-rich inclusions. The tendency towards nematicity, induced by Ni doping, appears to be the most important factor producing inferior superconducting properties of S crystals

Caffeine blocks disruption of blood brain barrier in a rabbit model of Alzheimer's disease

High levels of serum cholesterol and disruptions of the blood brain barrier (BBB) have all been implicated as underlying mechanisms in the pathogenesis of Alzheimer's disease. Results from studies conducted in animals and humans suggest that caffeine might be protective against Alzheimer's disease but by poorly understood mechanisms. Using rabbits fed a cholesterol-enriched diet, we tested our hypothesis that chronic ingestion of caffeine protects against high cholesterol diet-induced disruptions of the BBB. New Zealand rabbits were fed a 2% cholesterol-enriched diet, and 3 mg caffeine was administered daily in drinking water for 12 weeks. Total cholesterol and caffeine concentrations from blood were measured. Olfactory bulbs (and for some studies hippocampus and cerebral cortex as well) were evaluated for BBB leakage, BBB tight junction protein expression levels, activation of astrocytes, and microglia density using histological, immunostaining and immunoblotting techniques. We found that caffeine blocked high cholesterol diet-induced increases in extravasation of IgG and fibrinogen, increases in leakage of Evan's blue dye, decreases in levels of the tight junction proteins occludin and ZO-1, increases in astrocytes activation and microglia density where IgG extravasation was present. Chronic ingestion of caffeine protects against high cholesterol diet-induced increases in disruptions of the BBB, and caffeine and drugs similar to caffeine might be useful in the treatment of Alzheimer's disease

Superconductivity and topological aspects of the rock-salt carbides NbC and TaC

Superconducting materials with a nontrivial band structure are potential candidates for topological superconductivity. Here, by combining muon-spin rotation and relaxation ($\mu$SR) methods with theoretical calculations, we investigate the superconducting and topological properties of the rock-salt-type compounds NbC and TaC (with$T_c$ = 11.5 and 10.3 K, respectively). At a macroscopic level, the magnetization and heat-capacity measurements under applied magnetic field provide an upper critical field of 1.93 and 0.65 T for NbC and TaC, respectively. The low-temperature superfluid density, determined by transverse-field $\mu$SR and electronic specific-heat data, suggest a fully-gapped superconducting state in both NbC and TaC, with a zero-temperature gap $\Delta_0 = 1.90$ and 1.45 meV, and a magnetic penetration depth $\lambda_0$ = 141 and 77 nm, respectively. Band-structure calculations suggest that the density of states at the Fermi level is dominated by the Nb $4d$- (or Ta $5d$-) orbitals, which are strongly hybridized with the C $p$-orbitals to produce large cylinder-like Fermi surfaces, similar to those of high-$T_c$ iron-based superconductors. Without considering the spin-orbit coupling (SOC) effect, the first Brillouin zone contains three closed node lines in the bulk band structure, protected by time-reversal and space-inversion symmetry. When considering SOC, its effects in the NbC case appear rather modest. Therefore, the node lines may be preserved in NbC, hence proposing it as a potential topological superconductor.Comment: 10 pages, 12 figures, accepted by Physical Review