A Pan-Spectral Method of Abundance Determination

We propose a new method for determination of element abundances in stellar atmospheres aimed for the automatic processing of high-quality stellar spectra. The pan-spectral method is based on weighted cumulative line-widths Q of studied element. Difference in quantities Q found from synthetic and observed spectra gives a correction to the initial abundance. Final abundances are then found by rapidly converging iterations. Calculations can be made for many elements simultaneously and do not demand supercomputers.Comment: 4 pages, 2 figures, contribution presented at the ESO/Lisbon/Aveiro Workshop on Precision Spectroscopy in Astrophysics held in Aveiro, Portugal, 11-15 September 200

Modelling of mercury isotope separation in CP stellar atmospheres: results and problems

Formation of anomalous isotope abundances in the atmospheres of chemically peculiar (CP) stars can be explained by light-induced drift (LID). This effect is additional to the radiative acceleration and appears due to systematic asymmetry of radiative flux in partly overlapping isotopic spectral line profiles. LID causes levitation of an isotope with a red-shifted spectral line and sinking of an isotope with a blue-shifted line, generating thus diffusive separation of isotopes. We have studied diffusion of mercury as a typical well-studied isotope-rich heavy metal. Our model computations show that in mercury-rich quiescent atmospheres of CP stars LID causes levitation of the heavier mercury isotopes and sinking of the lighter ones. Precise quantitative modelling of the process of isotope separation demands very high-resolution computations and the high-precision input data, including data on hyperfine and isotopic splitting of spectral lines, adequate line profiles and impact cross-sections. Presence of microturbulence and weak stellar winds can essentially reduce the effect of radiative-driven diffusion.Comment: 8 pages, 4 figures. Manuscript accepted for publication in New Astronomy Reviews (proceedings of the 7th Serbian Conference on Spectral Line Shapes in Astrophysics, Zrenjanin, Serbia, June 15-19 2009

β2 Adrenergic Receptor Fluorescent Protein Fusions Traffic to the Plasma Membrane and Retain Functionality

Green fluorescent protein (GFP) has proven useful for the study of protein interactions and dynamics for the last twenty years. A variety of new fluorescent proteins have been developed that expand the use of available excitation spectra. We have undertaken an analysis of seven of the most useful fluorescent proteins (XFPs), Cerulean (and mCerulean3), Teal, GFP, Venus, mCherry and TagRFP657, as fusions to the archetypal G-protein coupled receptor, the β2 adrenergic receptor (β2AR). We have characterized these β2AR::XFP fusions in respect to membrane trafficking and G-protein activation. We noticed that in the mouse neural cell line, OP 6, that membrane bound β2AR::XFP fusions robustly localized in the filopodia identical to gap::XFP fusions. All β2ARR::XFP fusions show responses indistinguishable from each other and the non-fused form after isoprenaline exposure. Our results provide a platform by which G-protein coupled receptors can be dissected for their functionality

Fast Quantitative Real-Time PCR-Based Screening for Common Chromosomal Aneuploidies in Mouse Embryonic Stem Cells

Chromosomal integrity has been known for many years to affect the ability of mouse embryonic stem cells (mESCs) to contribute to the germline of chimeric mice. Abnormal chromosomes are generally detected by standard cytogenetic karyotyping. However, this method is expensive, time consuming, and often omitted prior to blastocyst injection, consequently reducing the frequency of mESC-derived offspring. Here, we show a fast, accurate, and inexpensive screen for identifying the two most common aneuploidies (Trisomy 8 and loss of chromosome Y) in genetically manipulated mESCs using quantitative real-time PCR (qPCR). Screening against these two aneuploidies significantly increases the fraction of normal mESC clones. Our method is extremely sensitive and can detect as low as 10% aneuploidy among a large population of mESCs. It greatly expedites the generation of mutant mice and provides a quick tool for assessing the aneuploidy percentages of any mESC line

Study of the Effect of Y2 O3 Doping on the Resistance to Radiation Damage of CeO2 Microparticles under Irradiation with Heavy Xe22+ Ions

This paper presents the results of a study on the influence of Y2 O3 doping on the resistance to radiation damage and an assessment of structural changes associated with the accumulation of radiation defects in CeO2 microparticles under irradiation with heavy Xe22+ ions. The relevance of this study consists of the prospects for the use of CeO2 microparticles as materials and candidates of inert matrices of nuclear fuel. A method of solid-phase synthesis was applied to obtain microparticles with different concentrations of dopant. It included grinding of CeO2 and Y2 O3 microparticles followed by thermal sintering at 1100◦ C in an oxygen-containing medium to produce highly ordered microparticles. During the study of the structural characteristics of the synthesized microparticles, it was found that increasing the dopant concentration from 0.05 mol.% to 0.15 mol.% leads to an increase in the crystallinity degree as well as a decrease in dislocation density. According to the results of the assessment of the resistance of microparticles to radiation damage, it was found that an increase in the dopant concentration leads to a decrease in swelling and structural distortion by more than 2.5–3 times, which indicates an increase in the radiation resistance. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (No. AP09058081)

Effect of Irradiation with Heavy Xe22+ Ions with Energies of 165–230 MeV on Change in Optical Characteristics of ZrO2 Ceramic

The aim of this work is to study the effect of irradiation with heavy Xe22+ ions with energies of 165 MeV, 200 MeV, and 230 MeV on the change in the optical properties of ZrO2 ceramic. The choice of ion energies, as well as irradiation fluences of 1013-1014 ion/cm2, is primarily due to the possibility of simulating radiation damage in ceramics that occurs when overlapping damaged areas in the material, comparable to damage from fission fragments of uranium nuclei in an atomic reactor. Using UV–Vis spectroscopy methods, changes in the throughput of ceramics were evaluated depending on the irradiation fluence and the energy of incident ions. It was found that a change in the irradiation conditions leads to the formation of irradiation-induced defects with an energy of 2.4–2.45 eV in the structure, the concentration of which increases with the irradiation dose. Changes in the band gap and refractive index depending on irradiation fluence and incident ions energy indicate a change in the electronic and optical density of ceramics, as well as the formation of additional absorbing centers in the structure. © 2021 Elsevier B.V.This work was supported by the Grant No. BR09158499 ( Development of complex scientific research in the field of nuclear and radiation physics on the basis of Kazakhstan accelerator complexes) of the Ministry of Energy of the Republic of Kazakhstan

New Methods in Modeling of Hot Stellar Atmospheres

In the present study we had three main aims. First to study the possibility of reducing the initial model atmosphere data to short analytical polynomials. The second was to use as the depth variable the logarithm of the local gas pressure instead the Rosseland mean. The third aim was to check the applicability of the derived formulae and proposed computation methods to obtain high precision self-consistent results in modeling hot plane-parallel stellar atmospheres. Introducing the dimensionless (reduced) local quantities θ = T/Teff and β = P/P(Teff) it has been shown that for hot convection-free stellar atmospheres the curves log θ versus log β reduce an initial grid of models to simple polynomials and bring forth some general features of the model stellar atmospheres. Even for stellar atmospheres having the convective zones in the deeper atmospheric layers, the outer part of the atmosphere (up to T = Teff and for Teff > 5000 K) can be described in the same manner by curves log θ versus log β as for the hotter stars. Iterative modeling of any hot stellar atmosphere can be started from these formulae (obtained for solar abundances), using rational polynomial ratios for P(Teff), obtaining from these data the needed T versus P dependence. To check suitability of the formulae, the iterative correction of the model stellar atmospheres has been carried out by the traditional Unsöld-Lucy method and by the novel least squares optimization based on Levenberg-Marquardt method, followed by Broyden correction loop. It has been shown that the flux constancy obtained by it is almost 2 dex higher than obtained by the Unsöld-Lucy method. The precision estimators as criteria of the modeling algorithms self-consistency and of the computational precision level have been proposed and used