Linear stability analysis of magnetohydrodynamic duct flows with perfectly conducting walls

<div><p>The stability of magnetohydrodynamic flow in a duct with perfectly conducting walls is investigated in the presence of a homogeneous and constant static magnetic field. The temporal growth and spatial distribution of perturbations are obtained by solving iteratively the direct and adjoint governing equations with respect of perturbations, based on nonmodal stability theory. The effect of the applied magnetic field, as well as the aspect ratio of the duct on the stability of the magnetohydrodynamic duct flow is taken into account. The computational results show that, weak jets appear near the sidewalls at a moderate magnetic field and the velocity of the jet increases with the increase of the intensity of the magnetic field. The duct flow is stable at either weak or strong magnetic field, but becomes unstable at moderate intensity magnetic field, and the stability is invariance with the aspect ratio of the duct. The instability of magnetohydrodynamic duct flow is related with the exponential growth of perturbations evolving on the fully developed jets. Transient growth of perturbations is also observed in the computation and the optimal perturbation is found to be in the form of streamwise vortices and localized within the sidewall layers. By contrast, the Hartmann layer perpendicular to the magnetic field is irrelevant to the stability issue of the magnetohydrodynamic duct flow.</p></div

Basic velocity profiles in ducts with different aspect ratio <i>r</i> at <i>Ha</i> = 10 (a, b) and <i>Ha</i> = 50 (c, d).

<p>Velocity profiles <i>U</i>(<i>y</i> + <i>r</i>, <i>z</i> = 0) within the sidewall layers (a, c); Velocity profiles <i>U</i>(<i>y</i> = 0, <i>z</i>) in the central cross-section parallel to the sidewall of the duct (b, d).</p

Energy amplification of perturbations <i>G</i> and the corresponding streamwise wavenumber <i>α</i> as a fuction of <i>τ</i> at <i>Re</i> = 7000.

<p>(a, b) <i>Ha</i> = 10; (c, d) <i>Ha</i> = 20; (e, f) <i>Ha</i> = 30; (g, h) <i>Ha</i> = 50.</p

(a) Energy amplification of perturbations <i>G</i> with different modes at <i>Re</i> = 3000 and <i>Ha</i> = 0; (b) Energy amplification of perturbations <i>G</i> in the duct with different aspect ratios <i>r</i> at <i>Re</i> = 3000 and <i>Ha</i> = 0.

<p>(a) Energy amplification of perturbations <i>G</i> with different modes at <i>Re</i> = 3000 and <i>Ha</i> = 0; (b) Energy amplification of perturbations <i>G</i> in the duct with different aspect ratios <i>r</i> at <i>Re</i> = 3000 and <i>Ha</i> = 0.</p

The spatial structures of optimal perturbations at initial with <i>Re</i> = 7000, <i>Ha</i> = 20 and <i>r</i> = 1 (left column) and <i>r</i> = 9 (right column).

<p>(a) <i>τ</i> = 13, <i>α</i> = 1.2; (b) <i>τ</i> = 13, <i>α</i> = 1.2; (c) <i>τ</i> = 50, <i>α</i> = 3.0; (d) <i>τ</i> = 50, <i>α</i> = 0.2.</p

Basic velocity profiles for different Hartmann numbers <i>Ha</i> in the square cross-section duct.

<p>(a) Velocity profiles <i>U</i>(<i>y</i>, <i>z</i> = 0) within the sidewall layers; (b) Velocity profiles <i>U</i>(<i>y</i> = 0, <i>z</i>) in the central cross-section parallel to the sidewall of the duct.</p

The optimal perturbation at different final time <i>τ</i> for <i>Re</i> = 7000 and <i>Ha</i> = 20 in the square cross-section duct.

<p>(a) <i>τ</i> = 13, <i>α</i> = 1.2; (b) <i>τ</i> = 50, <i>α</i> = 3.0. The iso-surfaces correspond to the ±0.45 and ±0.90 of the maximum magnitude of the streamwise velocity component.</p

DataSheet_1_Burden of psoriasis in young adults worldwide from the global burden of disease study 2019.docx

BackgroundTo determine the global burden of psoriasis in young adults, i.e., those aged 15–49, from 1990 to 2019 and predict trends in this burden for 2020 to 2030MethodsAge-standardized disease burden indicators and their estimated annual percentage changes were assessed and used to compare the estimated burden between regions. In addition, generalized additive models were used to predict the burden in this population from 2020 to 2030.ResultsFrom 1990 to 2019, the overall burden of psoriasis in young adults worldwide trended downward, as the age-standardized incidence rate and the age-standardized disability-adjusted life year rate decreased. From 1990 to 2019, there were gender differences in the burden of psoriasis between regions with different Socio-demographic index. Specifically, there was a smaller increase in the burden in young men than in young women in middle- and low–middle-Socio-demographic index areas. In 2019, Western Europe, Australasia, and Southern Latin America had the highest age-standardized incidence rate of psoriasis in young adults, whereas age-standardized disability-adjusted life year rates of psoriasis in young adults were highest in high-income North America. In 2019, the psoriasis burden in young adults was the highest in high-Socio-demographic index areas and the lowest in low-Socio-demographic index regions. We predict that from 2020 to 2030, the incidence rate and disability-adjusted life year rate of psoriasis in all age groups of young adults will continue to decline, but the burden in those aged 30–39 will increase.ConclusionFrom 1990 to 2019, the overall burden of psoriasis in each age group trended downward in this period. We predict that from 2020 to 2030, the burden of psoriasis in those aged 30–39 will increase.</p

Ferroelectricity in Covalently functionalized Two-dimensional Materials: Integration of High-mobility Semiconductors and Nonvolatile Memory

Realization of ferroelectric semiconductors by conjoining ferroelectricity with semiconductors remains a challenging task because most present-day ferroelectric materials are unsuitable for such a combination due to their wide bandgaps. Herein, we show first-principles evidence toward the realization of a new class of two-dimensional (2D) ferroelectric semiconductors through covalent functionalization of many prevailing 2D materials. Members in this new class of 2D ferroelectric semiconductors include covalently functionalized germanene, and stanene (<i>Nat. Commun.</i> <b>2014</b>, <i>5</i>, 3389), as well as MoS₂ monolayer (<i>Nat. Chem.</i> <b>2015</b>, <i>7</i>, 45), covalent functionalization of the surface of bulk semiconductors such as silicon (111) (<i>J. Phys. Chem. B</i> <b>2006</b>, <i>110</i> , 23898), and the substrates of oxides such as silica with self-assembly monolayers (<i>Nano Lett.</i> <b>2014</b>, <i>14</i>, 1354). The newly predicted 2D ferroelectric semiconductors possess high mobility, modest bandgaps, and distinct ferroelectricity that can be exploited for developing various heterostructural devices with desired functionalities. For example, we propose applications of the 2D materials as 2D ferroelectric field-effect transistors with ultrahigh on/off ratio, topological transistors with Dirac Fermions switchable between holes and electrons, ferroelectric junctions with ultrahigh electro-resistance, and multiferroic junctions for controlling spin by electric fields. All these heterostructural devices take advantage of the combination of high-mobility semiconductors with fast writing and nondestructive reading capability of nonvolatile memory, thereby holding great potential for the development of future multifunctional devices

Table_1_Systematic analysis of photo/sko-regulated germination and post-germination development of shallow photodormant seeds in Nicotiana tabacum L..docx

IntroductionLight is a major environmental factor in regulating germination and post-germination development of shallow photo-dormant seeds in Nicotiana tabacum L. (tobacco). However, its molecular mechanism remains largely unclear.Methods and resultsIn this study, we compared the phenotypes of the seeds germinated under light and dark, and systematically investigated their regulatory networks by integrating transcriptomic and proteomic data. Under light, the germination increased ~25%, the length of the hypocotyl shortened ~3 cm, and the apical hook disappeared. 9, 161, 342 differentially expressed genes (DEGs) and 128, 185, 81 differentially expressed proteins (DEPs) were regulated by light in the development stage of seed imbibition, radicle protrusion and cotyledon expansion respectively. 0, 19 and 1 co-up-regulated and 1, 30 and 64 co-down-regulated DEGs (DEP) were observed in the three stages, respectively. Of them, 2S albumin large chain, was down-regulated by light in imbibed seed. Oleosin 18.5 kDa (OLEO1) and Glyceraldehyde-3-phosphate dehydrogenase (GAPA1), Oxygen-evolving enhancer protein 1-1 and anchloroplastic (PSBO1), hub genes (proteins) in protein-protein interaction network (PPI), were downregulated and up-regulated in germinated seeds by light, respectively. OLEO1, a hub gene (proteins), was down-regulated by light in post-germination seedling.ConclusionThese results systematically revealed the molecular networks regulated by light during germination and post-germination development of shallow photo-dormant tobacco seeds.</p