Stabilization of the m=1m=1 mode in a long-thin mirror trap with high-beta anisotropic plasmas

Stability of a ``rigid'' ballooning mode $m = 1$ is studied in application to a mirror axisymmetric trap designed to confine anisotropic plasma with a large beta ($\beta$, the ratio of plasma pressure to magnetic field pressure). It was found that for effective stabilization by lateral perfectly conducting wall, the beta parameter must exceed some critical value $\beta_{\text{crit}}$. The dependence of $\beta_{\text{crit}}$ on the plasma anisotropy, mirror ratio and width of vacuum gap between plasma and the wall was studied. Unlike the works of other authors focused on the plasma model with a sharp boundary, we calculated the boundaries of the stability zone for a number of diffuse radial pressure profiles and several axial magnetic field profiles. With a combination of a conducting lateral wall and conducting end plates imitating the attachment of end MHD stabilizers to the central cell of an open trap, there are two critical values of beta and two stability zones, $\beta \beta_{\text{crit}2}$, which can merge, making the entire range of allowable beta values $0<\beta<1$ stable.Comment: 26 pages, 12 figures, 3 tables. arXiv admin note: text overlap with arXiv:2203.0837

Effects of Spatial Dispersion on Reflection from Mushroom-type Artificial Impedance Surfaces

Several recent works have emphasized the role of spatial dispersion in wire media, and demonstrated that arrays of parallel metallic wires may behave very differently from a uniaxial local material with negative permittivity. Here, we investigate using local and non-local homogenization methods the effect of spatial dispersion on reflection from the mushroom structure introduced by Sievenpiper. The objective of the paper is to clarify the role of spatial dispersion in the mushroom structure and demonstrate that under some conditions it is suppressed. The metamaterial substrate, or metasurface, is modeled as a wire medium covered with an impedance surface. Surprisingly, it is found that in such configuration the effects of spatial dispersion may be nearly suppressed when the slab is electrically thin, and that the wire medium can be modeled very accurately using a local model. This result paves the way for the design of artificial surfaces that exploit the plasmonic-type response of the wire medium slab.Comment: submitted for publication, under revie

Validating internal controls for quantitative plant gene expression studies

BACKGROUND: Real-time reverse transcription PCR (RT-PCR) has greatly improved the ease and sensitivity of quantitative gene expression studies. However, accurate measurement of gene expression with this method relies on the choice of a valid reference for data normalization. Studies rarely verify that gene expression levels for reference genes are adequately consistent among the samples used, nor compare alternative genes to assess which are most reliable for the experimental conditions analyzed. RESULTS: Using real-time RT-PCR to study the expression of 10 poplar (genus Populus) housekeeping genes, we demonstrate a simple method for determining the degree of stability of gene expression over a set of experimental conditions. Based on a traditional method for analyzing the stability of varieties in plant breeding, it defines measures of gene expression stability from analysis of variance (ANOVA) and linear regression. We found that the potential internal control genes differed widely in their expression stability over the different tissues, developmental stages and environmental conditions studied. CONCLUSION: Our results support that quantitative comparisons of candidate reference genes are an important part of real-time RT-PCR studies that seek to precisely evaluate variation in gene expression. The method we demonstrated facilitates statistical and graphical evaluation of gene expression stability. Selection of the best reference gene for a given set of experimental conditions should enable detection of biologically significant changes in gene expression that are too small to be revealed by less precise methods, or when highly variable reference genes are unknowingly used in real-time RT-PCR experiments

Spin-orbit coupled particle in a spin bath

We consider a spin-orbit coupled particle confined in a quantum dot in a bath of impurity spins. We investigate the consequences of spin-orbit coupling on the interactions that the particle mediates in the spin bath. We show that in the presence of spin-orbit coupling, the impurity-impurity interactions are no longer spin-conserving. We quantify the degree of this symmetry breaking and show how it relates to the spin-orbit coupling strength. We identify several ways how the impurity ensemble can in this way relax its spin by coupling to phonons. A typical resulting relaxation rate for a self-assembled Mn-doped ZnTe quantum dot populated by a hole is 1 $\mu$s. We also show that decoherence arising from nuclear spins in lateral quantum dots is still removable by a spin echo protocol, even if the confined electron is spin-orbit coupled.Comment: 18 pages, 1 figur

Theory of quantum dot spin-lasers

We formulate a model of a semiconductor Quantum Dot laser with injection of spin-polarized electrons. As compared to higher-dimensionality structures, the Quantum-Dot-based active region is known to improve laser properties, including the spin-related ones. The wetting layer, from which carriers are captured into the active region, acts as an intermediate level that strongly influences the lasing operation. The finite capture rate leads to an increase of lasing thresholds, and to saturation of emitted light at higher injection. In spite of these issues, the advantageous threshold reduction, resulting from spin injection, can be preserved. The "spin-filtering" effect, i.e., circularly polarized emission at even modest spin-polarization of injection, remains present as well. Our rate-equations description allows to obtain analytical results and provides transparent guidance for improvement of spin-lasers.Comment: 7 pages, 3 figure

Substrate-specific transcription of the enigmatic GH61 family of the pathogenic white-rot fungus Heterobasidion irregulare during growth on lignocellulose

The GH61 represents the most enigmatic Glycoside Hydrolase family (GH) regarding enzymatic activity and importance in cellulose degradation. Heterobasidion irregulare is a necrotizing pathogen and white-rot fungus that causes enormous damages in conifer forests. The genome of H. irregulare allowed identification of ten HiGH61 genes. qRT-PCR analysis separate the HiGH61 members into two groups; one that show up regulation on lignocellulosic substrates (HiGH61A, HiGH61B, HiGH61D, HiGH61G, HiGH61H, and HiGH61I) and a second showing either down-regulation or constitutive expression (HiGH61C, HiGH61E, HiGH61F, and HiGH61J). HiGH61H showed up to 17,000-fold increase on spruce heartwood suggesting a pivotal role in cellulose decomposition during saprotrophic growth. Sequence analysis of these genes reveals that all GH61s except HiGH61G possess the conserved metal-binding motif essential for activity. The sequences also divide into groups having either an insert near the N terminus or an insert near the second catalytic histidine, which may represent extensions of the substrate-binding surface. Three of the HiGH61s encode cellulose-binding modules (CBM1). Interestingly, HiGH61H and HiGH61I having CBM1s are up-regulated on pure cellulose. There was a common substrate-specific induction patterns of the HiGH61s with several reference cellulolytic and hemicellulolytic GHs, this taken together with their low transcript levels on media lacking lignocellulose, reflect the concerted nature of cell wall polymer degradation. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00253-012-4206-x) contains supplementary material, which is available to authorized users

Secondary polyvinyl butyral modified with potassium polytitanate for coatings with improved mechanical properties

The technology of laminated glass is accompanied with a large amount of polyvinyl butyral wastes, which are used for recycling due to mechanical properties of recycled PVB as these properties are lower than those of the original polymer. The properties of composite coatings based on secondary polyvinyl butyral modified with potassium polytitanate were investigated. The composite coating was obtained by polyvinyl butyral dissolved in ethyl alcohol and then dispersed potassium polytitanate into a solution. The resulting suspension was poured onto the surface of a solid substrate and then dried. The research shows that the surface modification of potassium polytitanate with different coupling agents significantly improves the polymer composite mechanical properties. The investigation of various homogenization techniques established a possibility for a significant improvement in the properties of a polyvinyl butyral composite by treatment in a ball mill. The mechanism interactions among the coupling agents, binders, and surface fillers were determined. The research also highlights the possibility of secondary polyvinyl butyral recycling and the production of films with high mechanical properties

Secondary polyvinyl butyral modified with potassium polytitanate for coatings with improved mechanical properties

The technology of laminated glass is accompanied with a large amount of polyvinyl butyral wastes, which are used for recycling due to mechanical properties of recycled PVB as these properties are lower than those of the original polymer. The properties of composite coatings based on secondary polyvinyl butyral modified with potassium polytitanate were investigated. The composite coating was obtained by polyvinyl butyral dissolved in ethyl alcohol and then dispersed potassium polytitanate into a solution. The resulting suspension was poured onto the surface of a solid substrate and then dried. The research shows that the surface modification of potassium polytitanate with different coupling agents significantly improves the polymer composite mechanical properties. The investigation of various homogenization techniques established a possibility for a significant improvement in the properties of a polyvinyl butyral composite by treatment in a ball mill. The mechanism interactions among the coupling agents, binders, and surface fillers were determined. The research also highlights the possibility of secondary polyvinyl butyral recycling and the production of films with high mechanical properties

Epitype-inducing temperatures drive DNA methylation changes during somatic embryogenesis in the long-lived gymnosperm Norway spruce

An epigenetic memory of the temperature sum experienced during embryogenesis is part of the climatic adaptation strategy of the long-lived gymnosperm Norway spruce. This memory has a lasting effect on the timing of bud phenology and frost tolerance in the resulting epitype trees. The epigenetic memory is well characterized phenotypically and at the transcriptome level, but to what extent DNA methylation changes are involved have not previously been determined. To address this, we analyzed somatic epitype embryos of Norway spruce clones produced at contrasting epitype-inducing conditions (18 and 28°C). We screened for differential DNA methylation in 2744 genes related mainly to the epigenetic machinery, circadian clock, and phenology. Of these genes, 68% displayed differential DNA methylation patterns between contrasting epitype embryos in at least one methylation context (CpG, CHG, CHH). Several genes related to the epigenetic machinery (e.g., DNA methyltransferases, ARGONAUTE) and the control of bud phenology (FTL genes) were differentially methylated. This indicates that the epitype-inducing temperature conditions induce an epigenetic memory involving specific DNA methylation changes in Norway spruce.publishedVersio

Identification and in silico characterization of novel and conservedmicrornas inmethyl jasmonate-stimulated scots pine (Pinus Sylvestris L.) needles

Funding Information: Funding: This project was funded by the Latvian Council of Science grant 284/2012 “Investigation of molecular defense mechanisms in Scots pine (Pinus sylvestris L.). Publisher Copyright: © 2020 by the authors.MicroRNAs (miRNAs) are non-protein coding RNAs of ~20-24 nucleotides in length that play an important role in many biological and metabolic processes, including the regulation of gene expression, plant growth and developmental processes, as well as responses to stress and pathogens. The aim of this study was to identify and characterize novel and conserved microRNAs expressed in methyl jasmonate-treated Scots pine needles. In addition, potential precursor sequences and target genes of the identified miRNAs were determined by alignment to the Pinus unigene set. Potential precursor sequences were identified using the miRAtool, conserved miRNA precursors were also tested for the ability to form the required stem-loop structure, and the minimal folding free energy indexes were calculated. By comparison with miRBase, 4975 annotated sequences were identified and assigned to 173 miRNA groups, belonging to a total of 60 conserved miRNA families. A total of 1029 potential novel miRNAs, grouped into 34 families were found, and 46 predicted precursor sequences were identified. A total of 136 potential target genes targeted by 28 families were identified. The majority of previously reported highly conserved plant miRNAs were identified in this study, as well as some conserved miRNAs previously reported to be monocot specific. No conserved dicot-specific miRNAs were identified. A number of potential gymnosperm or conifer specific miRNAs were found, shared among a range of conifer species.publishersversionPeer reviewe