277 research outputs found
Metallic phase in stoichiometric CeOBiS 2 revealed by space-resolved ARPES
Recently CeOBiS2 system without any fluorine doping is found to show superconductivity posing question on its origin. Using space resolved ARPES we have found a metallic phase embedded in the morphological defects and at the sample edges of stoichiometric CeOBiS2. While bulk of the sample is semiconducting, the embedded metallic phase is characterized by the usual electron pocket at X point, similar to the Fermi surface of doped BiS2-based superconductors. Typical size of the observed metallic domain is larger than the superconducting correlation length of the system suggesting that the observed superconductivity in undoped CeOBiS2 might be due to this embedded metallic phase at the defects. The results also suggest a possible way to develop new systems by manipulation of the defects in these chalcogenides with structural instability
Indium selenide: An insight into electronic band structure and surface excitations
We have investigated the electronic response of single crystals of indium selenide by means of angle-resolved photoemission spectroscopy, electron energy loss spectroscopy and density functional theory. The loss spectrum of indium selenide shows the direct free exciton at similar to 1.3 eV and several other peaks, which do not exhibit dispersion with the momentum. The joint analysis of the experimental band structure and the density of states indicates that spectral features in the loss function are strictly related to single-particle transitions. These excitations cannot be considered as fully coherent plasmons and they are damped even in the optical limit, i.e. for small momenta. The comparison of the calculated symmetry-projected density of states with electron energy loss spectra enables the assignment of the spectral features to transitions between specific electronic states. Furthermore, the effects of ambient gases on the band structure and on the loss function have been probed
Protein Dynamics Control of Electron Transfer in Photosynthetic Reaction Centers from Rps. Sulfoviridis
In the cycle of photosynthetic reaction centers, the initially oxidized special pair of bacteriochlorophyll molecules is subsequently reduced by an electron transferred over a chain of four hemes of the complex. Here, we examine the kinetics of electron transfer between the proximal heme c-559 of the chain and the oxidized special pair in the reaction center from Rps. sulfoviridis in the range of temperatures from 294 to 40 K. The experimental data were obtained for three redox states of the reaction center, in which one, two, or three nearest hemes of the chain are reduced prior to special pair oxidation. The experimental kinetic data are analyzed in terms of a Sumi–Marcus-type model developed in our previous paper,1 in which similar measurements were reported on the reaction centers from Rps. viridis. The model allows us to establish a connection between the observed nonexponential electron-transfer kinetics and the local structural relaxation dynamics of the reaction center protein on the microsecond time scale. The activation energy for relaxation dynamics of the protein medium has been found to be around 0.1 eV for all three redox states, which is in contrast to a value around 0.4–0.6 eV in Rps. viridis.1 The possible nature of the difference between the reaction centers from Rps. viridis and Rps. sulfoviridis, which are believed to be very similar, is discussed. The role of the protein glass transition at low temperatures and that of internal water molecules in the process are analyzed.España, Ministerio de Educación y Ciencia BFU2004-04914-C02-01/BMCJunta de Andalucía PAI CVI-26
Buy-out of pets because of their unproper treatment under civil legislation of Russia and post-soviet countries
The article deals with one of the compulsory methods of ownership right termination - the buy-out of pets if they are treated improperly. The authors draw attention to the specifics of this reason, which is associated with the buy-out subject, i.e. with an animal. They performed the comparative analysis of "pet improper treatment" and "cruel animal treatment" concepts, the problem of their differentiation is studie
Spectromicroscopy of electronic phase separation in KFeSe superconductor
Structural phase separation in AFeSe system has been studied
by different experimental techniques, however, it should be important to know
how the electronic uniformity is influenced, on which length scale the
electronic phases coexist, and what is their spatial distribution. Here, we
have used novel scanning photoelectron microscopy (SPEM) to study the
electronic phase separation in KFeSe, providing a direct
measurement of the topological spatial distribution of the different electronic
phases. The SPEM results reveal a peculiar interconnected conducting
filamentary phase that is embedded in the insulating texture. The filamentary
structure with a particular topological geometry could be important for the
high T superconductivity in the presence of a phase with a large magnetic
moment in AFeSe materials.Comment: 14 pages,3 figure
Strongly localized polaritons in an array of trapped two-level atoms interacting with a light field
We propose a new type of spatially periodic structure, i.e. polaritonic
crystal (PolC), to observe a "slow"/"stopped" light phenomenon due to coupled
atom-field states (polaritons) in a lattice. Under the tightbinding
approximation, such a system realizes an array of weakly coupled trapped
two-component atomic ensembles interacting with optical field in a
tunnel-coupled one dimensional cavity array. We have shown that the phase
transition to the superfluid Bardeen-Cooper-Schrieffer state, a so-called
(BCS)-type state of low branch polaritons, occurs under the strong coupling
condition. Such a transition results in the appearance of a macroscopic
polarization of the atomic medium at non-zero frequency. The principal result
is that the group velocity of polaritons depends essentially on the order
parameter of the system, i.e. on the average photon number in the cavity array.Comment: 16 pages, 6 figure
NOVEL APPROACHES TO TREATING NONSPECIFIC LOW BACK PAIN
Objective: to evaluate the impact of therapy with chondroitin sulfate (CS) and glucosamine (GA) on the clinical manifestations of low back pain (LBP).Subjects and methods. A multicenter open-label observational prospective study was conducted in 22 cities of Russia (46 centers) to investigate the efficacy of a combination of CS and GA in the outpatient treatment of nonspecific LBP. A total of 9761 patients were enrolled in the study that was completed by 8546 patients. Therapeutic efficiency was evaluated from changes in pain intensity during movement and at rest, by using the visual analogue scale. The Oswestry disability index, an global physician and patient assessment of therapeutic efficiency, and a daily need for nonsteroidal anti-inflammatory drugs (NSAIDs) were taken into account as additional criteria for efficiency evaluation.Results and discussion. The multicenter open-label observational study established the efficacy of a combination of CS and GA in treating nonspecific LBP: relief in pain during movement and at rest, functional improvement, and a reduction in the daily need for NSAIDs. The patients and physicians highly assessed therapeutic efficiency. The combination of CS and GA was also noted to be well tolerated. The findings may suggest that this combination may be a promising tool to treat LBP and gives proof to the expediency of its use in randomized placebo-controlled studies
Determination of interatomic coupling between two-dimensional crystals using angle-resolved photoemission spectroscopy
Lack of directional bonding between two-dimensional crystals like graphene or
monolayer transition metal dichalcogenides provides unusual freedom in
selection of components for vertical van der Waals heterostructures. However,
even for identical layers, their stacking, in particular the relative angle
between their crystallographic directions, modifies properties of the
structure. We demonstrate that the interatomic coupling between two
two-dimensional crystals can be determined from angle-resolved photoemission
spectra of a trilayer structure with one aligned and one twisted interface.
Each of the interfaces provides complementary information and together they
enable self-consistent determination of the coupling. We parametrize
interatomic coupling for carbon atoms by studying twisted trilayer graphene and
show that the result can be applied to structures with different twists and
number of layers. Our approach demonstrates how to extract fundamental
information about interlayer coupling in a stack of two-dimensional crystals
and can be applied to many other van der Waals interfaces.Comment: This is a post-peer-review, pre-copyedit version of an article
published in Nature Communications. The final authenticated version is
available online at: http://dx.doi.org/10.1038/s41467-020-17412-
Anomalous exponents in the rapid-change model of the passive scalar advection in the order
Field theoretic renormalization group is applied to the Kraichnan model of a
passive scalar advected by the Gaussian velocity field with the covariance
. Inertial-range
anomalous exponents, related to the scaling dimensions of tensor composite
operators built of the scalar gradients, are calculated to the order
of the expansion. The nature and the convergence of
the expansion in the models of turbulence is are briefly discussed.Comment: 4 pages; REVTeX source with 3 postscript figure
- …