The generalized dual-kinetic-balance approach for axially symmetric systems is employed to solve the two-center Dirac problem. The spectra of one-electron homonuclear quasimolecules are calculated ...and compared with the previous calculations. The analysis of the monopole approximation with two different choices of the origin is performed. Special attention is paid to the lead and xenon dimers, Pb82+–Pb82+–e− and Xe54+–Xe54+–e−, where the energies of the ground and several excited σ-states are presented in the wide range of internuclear distances. The developed method provides the quasicomplete finite basis set and allows for the construction of perturbation theory, including within the bound-state QED.
The current status of the theoretical investigation of the bound-electron g factor in lithium-like and boron-like highly charged ions is reported. Some tension between the several theoretical values ...and measurements is discussed. Then, prospects for future investigations are briefly reviewed.
Characteristics of a photoacoustic signal depending on mechanical stresses in the vicinity of a hole in a D16 aluminum-alloy plate have been analyzed. A new nonlinear photoacoustic effect was found ...that consists in the occurrence of a nonlinear component in the photoacoustic signal depending on mechanical stresses in the vicinity of a hole. This dependence is detected in the signal on the main modulation frequency of laser radiation. We have proposed a theoretical description of the detected effect of thermoelastic generation of ultrasound in stressed metals based on taking into account the thermal impact of laser radiation on their electron subsystem.
This paper is an experimental and theoretical study of changes in a laser-induced photoacoustic signal near a hole in metal plates of D16 aluminum alloy. The process of photoacoustic signal ...generation from metals is analyzed within the classical thermoelasticity framework, with account for only the thermal effect of laser irradiation on metal lattice deformation. A comparison is made of photoacoustic experimental and theoretical results obtained for a mechanically stressed aluminum alloy plate with a hole. The effect of external mechanical stresses on the behavior of laser photoacoustic signals near the hole is studied experimentally and theoretically. It is found that the classical theory of thermoelasticity is not enough to correctly describe the stress dependence of the photoacoustic signal near a hole in aluminum alloy plates. In order for the obtained experimental and theoretical results to agree, along with the thermal effect of laser irradiation on the lattice, it is necessary to account for the additional effect of the electron gas. A calibration procedure of the laser photoacoustic signal with respect to stress is described. It is shown that internal stresses in metals can be estimated by the photoacoustic method in combination with the hole drilling method.
The effect of mechanical stress influence on the thermoelastic photoacoustic signals inside Vickers indents in steel and nanonickel has been experimentally demonstrated. It has been shown that ...photoacoustic signal changes due to external stresses can be reversible or irreversible, depending on the indent orientation and the stress applied to the sample. Reversible changes in the photoacoustic signal can reach significant values at the level of tens percent of the average signal amplitude from the sample. Relative changes in the photoacoustic signal amplitudes have been theoretically evaluated for Vickers-indented and non-indented areas, taking into account the dependence of the elastic modulus of metals on temperature. It has been shown that this theoretical consideration provides qualitative explanation of differences in the behavior of photoacoustic signals under stress in indented and non-indented areas in metals.
•Thermal wave propagation via non-ideal joints of semiconductor devices is studied.•Non-ideal thermal joints were simulated using complex thermal conductance.•Complex thermal conductance is needful ...for joints with high volumetric heat capacity.•Thermal properties of electronic devices were studied by a photodeflection method.•Photodeflection signals were calculated for objects with many vertical layers.
Thermal wave propagation through solid-solid non-ideal interfaces in multilayer semiconductor devices is considered. A theoretical model is developed for thermal wave propagation, and the laser photothermal probe beam deflection method is used for experimental study of heat transport through multilayered samples with vertical joint interfaces. Experimental and theoretical results are presented for bonded and soldered joints. It is shown that, in general case, both the thermal resistance and the heat capacity of the joint should be considered to describe adequately experimental data and to determine thermophysical properties of a separate layer. It is shown that the real thermal resistance of a soldered joint may be much higher than the predicted one basing on tabulated characteristics. The paper demonstrates that the laser photothermal beam-deflection methods can be applied for testing the thermal contact quality between elements of multilayered semiconductor structures, for example, a multijunction solar cell, assembling by various technologies. These methods make possible to evaluate quantitatively the thermal resistance and heat capacity of thermal contacts at the micrometer scale.
Reprogramming of a limited number of human cell types has been achieved through ectopic expression of four transcription factors to yield induced pluripotent stem (iPS) cells that closely resemble ...human embryonic stem cells (ESCs). Here, we determined functional and epigenetic properties of iPS cells generated from human umbilical vein endothelial cells (HUVEC) by conventional method of direct reprogramming. Retroviral overexpression of four transcription factors resets HUVEC to the pluripotency. Human endothelial cell-derived iPS (endo-iPS) cells were similar to human ESCs in morphology, gene expression, in vitro and in vivo differentiation capacity. Endo-iPS cells were efficiently differentiated in vitro into endothelial cells. Using genome-wide methylation profiling we show that promoter elements of endothelial specific genes were methylated following reprogramming whereas pluripotency-related gene promoters were hypomethylated similar to levels observed in ESCs. Genome-wide methylation analysis of CpG sites located in the functional regions of over than 14,000 genes indicated that human endo-iPS cells were highly similar to human ES cells, although differences in methylation levels of 46 genes were found. Overall CpG methylation of promoter regions in the pluripotent cells was higher than in somatic. We also show that during reprogramming female human endo-iPS cells exhibited reactivation of the somatically silenced X chromosome. Our findings demonstrate that iPS cells can be generated from human endothelial cells and reprogramming resets epigenetic status of endothelial cells to pluripotency.
Recently, we identified a large number of ultraconserved (uc) sequences in noncoding regions of human, mouse, and rat genomes that appear to be essential for vertebrate and amniote ontogeny. Here, we ...used similar methods to identify ultraconserved genomic regions between the insect species Drosophila melanogaster and Drosophila pseudoobscura, as well as the more distantly related Anopheles gambiae. As with vertebrates, ultraconserved sequences in insects appear to occur primarily in intergenic and intronic sequences, and at intron-exon junctions. The sequences are significantly associated with genes encoding developmental regulators and transcription factors, but are less frequent and are smaller in size than in vertebrates. The longest identical, nongapped orthologous match between the three genomes was found within the homothorax (hth) gene. This sequence spans an internal exon-intron junction, with the majority located within the intron, and is predicted to form a highly stable stem-loop RNA structure. Real-time quantitative PCR analysis of different hth splice isoforms and Northern blotting showed that the conserved element is associated with a high incidence of intron retention in hth pre-mRNA, suggesting that the conserved intronic element is critically important in the post-transcriptional regulation of hth expression in Diptera.
The effect of external mechanical stresses on the parameters of photoacoustic signals within Vickers indents in steel and nanocopper has been experimentally revealed. It has been shown that changes ...in photoacoustic signals can be reversible and irreversible, depending on the indent orientation and the stress applied to the sample. In this case, reversible changes can reach significant values at the level of tens of percent of the average signal from the sample. The relative changes in the photoacoustic signal amplitudes have been theoretically evaluated for indented and unindented areas, taking into account the temperature dependence of the elastic modulus of metals. It has been shown that its consideration allows qualitative explanation of the differences in the behavior of photoacoustic signals under stresses in indented and unindented areas.
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