Gallium chalcogenides are promising building blocks for novel van der Waals heterostructures. We report on the low-temperature micro-photoluminescence (PL) of GaTe and GaSe films with thicknesses ...ranging from 200 nm to a single unit cell. In both materials, PL shows a dramatic decrease by 104-105 when film thickness is reduced from 200 to 10 nm. Based on evidence from continuous-wave (cw) and time-resolved PL, we propose a model explaining the PL decrease as a result of non-radiative carrier escape via surface states. Our results emphasize the need for special passivation of two-dimensional films for optoelectronic applications.
The porous titania growth during electrochemical anodization of titanium films and foils in the 0.1M ammonium fluoride (FNH4) solution in ethyleneglycol has been studied in the temperature range from ...−5°C to +20°C. Titania films with a smooth tubular morphology was found to be formed at the electrolyte temperatures below 0°C. The growth rate was as high as 1.5μm/min provided that the tube diameters were up to 300nm and the film porosity was less than 1%. Porous titanium anodization at the electrolyte temperature of 0°C and below induces formation of porous titania with a structure close to ideal packed hexagonal prisms with a smooth tubular surface. The mechanism of the appearance of such structure is discussed.
► Porous titania with an ordered hexagonal structure ► The approach to form the porous titania doped with carbon up to 18at.% ► The record values of titanium anodization process have been reached. ► The record values of titania parameters have been obtained.
The natural frequencies and modes of cantilever isotropic thin closed corrugated circular cylindrical shells with arbitrary number of corrugations are determined using the finite-element method. Two ...test problems for longitudinally corrugated open circular cylindrical shells are solved. The frequencies determined with our method and with the spline-collocation method in combination with the method of discrete orthogonalization are in good agreement (the difference is no greater than 5.5%). The natural frequencies of corrugated shells with different number of corrugations are compared. The dependence of the natural frequency of corrugated shells on the number of corrugations and vibration modes is established. The symmetric and antisymmetric modes of vibrations including those of tensile, shear, flexural, and torsional vibrations for all the corrugated shells considered are found.
The frequency and mode of free vibrations of thin isotropic triangular plates with a central hole for different boundary conditions are determined using the finite-element method. The topology of ...vibration modes for some plates is presented compared with square plates with hinged and clamped edges. To validate the numerical values of the natural frequencies and modes of triangular plates, an experimental method is proposed. It demonstrates a good agreement of the results with an error less than 6%.
Blood bacterial DNA is one of the pathogen-associated molecular patterns whose signaling pathways can alter the expression of neurotrophins, such as brain-derived neurotrophic factor (BDNF) and nerve ...growth factor (NGF). The study of neurotrophins is interesting in the context of obesity, which is associated with the risk of neuropathy. At the same time, the risk of complications depends on the metabolic type of obesity: in the metabolically unhealthy type (MUHO), this risk is significantly higher than in the metabolically healthy (MHO). The aim was to study the relationship between blood microbiome taxa and serum BDNF and NGF levels in different metabolic types of obesity. Healthy non-obese donors (
n
= 114) and obese patients (
n
= 98) were examined. Obese patients were divided into subgroups depending on the obesity metabolic type: patients with MHO (
n
= 36) and patients with MUHO (
n
= 53). Serum concentrations of neurotrophins were measured, and qualitative assessment of the blood microbiome was carried out by sequencing the variable region of the 16S rRNA gene. In healthy donors, taxa translocated from the skin and respiratory tract were negatively associated with BDNF, but in obesity, especially MUHO, this relationship was positive. Taxa translocated from the stomach (
Helicobacter pylori
) and intestine (
Sutterella
spp.) were negatively associated with BDNF in obese patients. NGF in healthy donors was positively associated with
Akkermansia muciniphila
, the taxon supporting intestinal integrity and reducing intestinal permeability. Patients with MUHO had a positive relationship between NGF and
Ruminococcus bromii
. Numerous negative relationships between the taxa of the intestinal flora and NGF were found in healthy donors and patients with MUHO, but not with MHO. In general, the effect of blood bacterial DNA on the serum concentration of neurotrophins depends on the translocation sources, permeability of the outer barriers, characteristics of microbiomes (gut, skin, etc.), as well as the presence or absence of metabolic disorders in patients with different body weight.
The frequencies and modes of free vibrations of a thin closed corrugated circular cylindrical shell with different clamped and free-ends boundary conditions and different physical and mechanical ...parameters are determined using the finite-element method. The test problem for an open corrugated elliptical cylindrical shell is solved. The solution demonstrates good agreement (less than 2.5%) between the calculated natural frequencies and the frequencies determined by other authors using the spline-collocation method in combination with the discrete-orthogonalization method. The frequencies of the corrugated shell are compared with those for a circular shell of equivalent mass. The dependence of the natural frequencies of a corrugated shell on the boundary conditions and the physical and mechanical characteristics of its material is established. Symmetric and antisymmetric vibration modes are determined for all the corrugated shells considered.
The formation of supramolecular complexes of glycyrrhetic acid (GLA) and levomycetin was detected and studied for the first time using electrospray-ionization mass spectrometry (ESI-MS). It was shown ...that the intermolecular complexes detected in the mass spectra were formed most effectively for a 1:1 host–guest ratio and less effectively for a 1:2 ratio. GLA aggregates (dimers and trimers) bound one or two levomycetin molecules and formed several singly and doubly charged cationic complexes. A comparison of the mass spectra of supramolecular complexes of glycyrrhizic acid (GA) and its aglycon (GLA) indicated that GLA self-aggregates and complexes with levomycetin formed more effectively than those of GA.
We study three-dimensional pseudo-spherical submanifolds in
R
5
, whose Bianchi transformations are degenerate of rank 2. A complete description of such submanifolds is obtained in the case where the ...Bianchi transformations are holonomically degenerate.
The formation of self-associates of glycyrrhetinic acid (GLA), an aglycone of glycyrrhizic acid (GA), has been studied by electrospray ionization mass spectrometry. It has been shown for the first ...time that, analogously to triterpene saponins having free carboxyl groups, GLA stereoisomers can form self-associates. The capacity of GLA to form self-associates has been confirmed by the mass spectrometry data. It has been found that the ionization of GLA self-associates with the formation of an anion proceeds rather weakly. The ionization of GLA in the positive ion mode goes on effectively and makes it possible to record multidimensional structures of one to eight 18α-GLA molecules and from one to nine 18β-GLA molecules. The structure of GLA associates and their stability are demonstrated most comprehensively in positive ion mass spectra. As a whole, the sets and intensity of peaks for 18α- and 18β-GLA correlate well. The results of the mass spectrometry study show the capacity of 18α- and 18β-GLA stereoisomers to form self-associates, which indicates a high potentiality of GLA in providing noncovalent interactions during the formation of supramolecular complexes. Similarly to the saponins of licorice and ivy, GLA stereoisomers may form a potential basis for the synthesis of a new generation of noncovalent molecular complexes and novel highly effective medicinal substances owing to a possible improvement in bioaccessibility and possible synergistic effects.
We present the results of metallographic investigations of the structure and microhardness and the results of the bench tests of the threads of tubings made of steels of the strength class D after ...finishing electromechanical surface quenching in pairs with commercial couplings.
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