218 research outputs found
Next stage of search for 2K(2)-capture of Kr
A technique to search for 2K-capture of Kr with large low-background
proportional counter filled with an enriched in Kr up to 99.8% sample of
Krypton at a pressure of 4.51 is described in this paper. The results of first
measurements are presented. Analysis of data collected during 159 hours yielded
new limit to the half-life of Kr with regard to 2K-capture
(T yr (90% C.L.)). Sensitivity of the facility to the
process for one year of measurement was evaluated to be
yr (90% C.L.).Comment: 4 pages, 5 figures; talk at the NANP'05 Conference; submitted to
Phys. At. Nuc
Two-body quantum mechanical problem on spheres
The quantum mechanical two-body problem with a central interaction on the
sphere is considered. Using recent results in representation
theory an ordinary differential equation for some energy levels is found. For
several interactive potentials these energy levels are calculated in explicit
form.Comment: 41 pages, no figures, typos corrected; appendix D was adde
On the derivation of the t-J model: electron spectrum and exchange interactions in narrow energy bands
A derivation of the t-J model of a highly-correlated solid is given starting
from the general many-electron Hamiltonian with account of the
non-orthogonality of atomic wave functions. Asymmetry of the Hubbard subbands
(i.e. of ``electron'' and ``hole''cases) for a nearly half-filled bare band is
demonstrated. The non-orthogonality corrections are shown to lead to occurrence
of indirect antiferromagnetic exchange interaction even in the limit of the
infinite on-site Coulomb repulsion. Consequences of this treatment for the
magnetism formation in narrow energy bands are discussed. Peculiarities of the
case of ``frustrated'' lattices, which contain triangles of nearest neighbors,
are considered.Comment: 4 pages, RevTe
Essential spectra and exponential estimates of eigenfunctions of lattice operators of quantum mechanics
This paper is devoted to estimates of the exponential decay of eigenfunctions
of difference operators on the lattice Z^n which are discrete analogs of the
Schr\"{o}dinger, Dirac and square-root Klein-Gordon operators. Our
investigation of the essential spectra and the exponential decay of
eigenfunctions of the discrete spectra is based on the calculus of so-called
pseudodifference operators (i.e., pseudodifferential operators on the group
Z^n) with analytic symbols and on the limit operators method. We obtain a
description of the location of the essential spectra and estimates of the
eigenfunctions of the discrete spectra of the main lattice operators of quantum
mechanics, namely: matrix Schr\"{o}dinger operators on Z^n, Dirac operators on
Z^3, and square root Klein-Gordon operators on Z^n
Two-hole problem in the t-J model: A canonical transformation approach
The t-J model in the spinless-fermion representation is studied. An effective
Hamiltonian for the quasiparticles is derived using canonical transformation
approach. It is shown that the rather simple form of the transformation
generator allows to take into account effect of hole interaction with the
short-range spin waves and to describe the single-hole groundstate. Obtained
results are very close to ones of the self-consistent Born approximation.
Further accounting for the long-range spin-wave interaction is possible on the
perturbative basis. Both spin-wave exchange and an effective interaction due to
minimization of the number of broken antiferromagnetic bonds are included in
the effective quasiparticle interaction. Two-hole bound state problem is solved
using Bethe-Salpeter equation. The only d-wave bound state is found to exist in
the region of 1< (t/J) <5. Combined effect of the pairing interactions of both
types is important to its formation. Discussion of the possible relation of the
obtained results to the problem of superconductivity in real systems is
presented.Comment: 19 pages, RevTeX, 12 postscript figure
Pteridophyte Distribution of the Urals and Adjacent Areas: a Dataset
Background Data on the species diversity and distribution of pteridophytes (lycophytes and ferns) in the Urals and adjacent areas are presented. The dataset includes 13,742 observations of two classes Lycopodiopsida and Polypodiopsida. In total, the dataset contains information on 16 families, 28 generas, 65 species, four subspecies and nine interspecies hybrids. All records are for lycophytes and ferns collected over 170 years between 1853 and 2021. The dataset presented is based on herbarium specimens, published data and field research conducted by the authors. This dataset is the first and important step towards generalising information on the current diversity and geographical distribution of pteridophytes in the Urals and adjacent areas. © Melnikov D et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Funding: This work was supported in part by the Program for Improving the Competitiveness of the Ural Federal University (the decree no. 211 of the Government of the Russian Federation, contract No. 02.A03.21.0006), the state assignments АААА-А19-119031290052-1 (Komarov Botanical Institute RAS), no. 0111-2019-0001 (Tsitsin Main Botanical Garden of the RAS), no. AAAA-A17-117072810011-1 (Institute Botanical Garden UB RAS) and no. АААА-А19-119031890084-6 (Institute of Plant and Animal Ecology UB RAS). This research was carried out within the project No. 121041600045-8 "Western Siberia in the context of Eurasian ties: man, nature, society". We thank the Ministry of Higher Education and Science of Russian Federation for the supportgiven to the Center of Collective Use “Herbarium MBG RAS” (Agreement No. 075-15-2021-678). The work was carried out as part of the Russia 2021 project
Magnetic force microscope tip-induced remagnetization of CoPt nanodisks with perpendicular anisotropy
We report on the results of a magnetic force microscopy investigation of remagnetization processes in arrays of CoPt nanodisks with diameters of 35 and 200 nm and a thickness of 9.8 nm fabricated by e-beam lithography and ion etching. The controllable magnetization reversal of individual CoPt nanodisks by the magnetic force microscope (MFM) tip-induced magnetic field was demonstrated. We observed experimentally two essentially different processes of tip-induced remagnetization. Magnetization reversal of 200 nm disks was observed when the probe moved across the particle while in case of 35 nm nanodisks one-touch remagnetization was realized. Micromagnetic modeling based on the Landau-Lifshitz-Gilbert (LLG) equation demonstrated that the tip-induced magnetization reversal occurs through the essentially inhomogeneous states. Computer simulations confirmed that in case of 200 nm disks the mechanism of embryo nucleation with reversed magnetization and further dynamic propagation following the probe moving across the particle was realized. On the other hand one-touch remagnetization of 35 nm disks occurs through the inhomogeneous vortexlike state. Micromagnetic LLG simulations showed that magnetization reversal in an inhomogeneous MFM probe field has a lower energy barrier in comparison with the mechanism of coherent rotation, which takes place in a homogeneous external magnetic field
The little skate genome and the evolutionary emergence of wing-like fins
Skates are cartilaginous fish whose body plan features enlarged wing-like pectoral fins, enabling them to thrive in benthic environments1,2. However, the molecular underpinnings of this unique trait remain unclear. Here we investigate the origin of this phenotypic innovation by developing the little skate Leucoraja erinacea as a genomically enabled model. Analysis of a high-quality chromosome-scale genome sequence for the little skate shows that it preserves many ancestral jawed vertebrate features compared with other sequenced genomes, including numerous ancient microchromosomes. Combining genome comparisons with extensive regulatory datasets in developing fins—including gene expression, chromatin occupancy and three-dimensional conformation—we find skate-specific genomic rearrangements that alter the three-dimensional regulatory landscape of genes that are involved in the planar cell polarity pathway. Functional inhibition of planar cell polarity signalling resulted in a reduction in anterior fin size, confirming that this pathway is a major contributor to batoid fin morphology. We also identified a fin-specific enhancer that interacts with several hoxa genes, consistent with the redeployment of hox gene expression in anterior pectoral fins, and confirmed its potential to activate transcription in the anterior fin using zebrafish reporter assays. Our findings underscore the central role of genome reorganization and regulatory variation in the evolution of phenotypes, shedding light on the molecular origin of an enigmatic trait
РОССИЙСКОЕ РЕСПИРАТОРНОЕ ОБЩЕСТВО ФЕДЕРАЛЬНЫЕ КЛИНИЧЕСКИЕ РЕКОМЕНДАЦИИ ПО ДИАГНОСТИКЕ И ЛЕЧЕНИЮ БРОНХИАЛЬНОЙ АСТМЫ
Asthma is a chronic inflammatory airway disease with bronchial hyperresponsivenes causing recurrent episodes of wheezing, dyspnea, chest tightness and cough which typically occur at nighttime or early in the morning. These episodes are due to generalized airway obstruction which is commonly reversible spontaneously or with treatment. Asthma is mainly diagnosed clinically and should be based on the patient's symptoms and signs, lung function testing with investigations of bronchial obstruction reversibility, allergy testing and after exclusion of other diseases. The aim of asthma therapy is achievement and maintenance of asthma control that is maximal resolution of clinical symptoms of the disease.Бронхиальная астма (БА) – хроническое воспалительное заболевание дыхательных путей с развитием бронхиальной гиперреактивности, которая обусловливает повторяющиеся эпизоды свистящих хрипов, одышки, чувства заложенности в груди и кашля, в особенности по ночам или ранним утром. Эти эпизоды связаны с распространенной обструкцией дыхательных путей, которая часто бывает обратимой спонтанно или под влиянием лечения. Диагноз БА является клиническим и устанавливается на основании жалоб и анамнеза пациента, клинико-функционального обследования с оценкой обратимости бронхиальной обструкции, специфического аллергологического обследования и при исключении других заболеваний. Целью лечения стабильной БА является достижение и поддержание контроля над симптомами БА, другими словами, максимальное устранение клинических проявлений заболевания
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