g-B3 C2 N3 : A Potential Two Dimensional Metal-free Photocatalyst for Overall Water Splitting.

Based on hybrid density functional theory (DFT) calculations, we propose a new two-dimensional (2D) B-C-N material, graphitic- B 3 C 2 N 3 ${B_3 C_2 N_3 }$ (g- B 3 C 2 N 3 ${B_3 C_2 N_3 }$ ), with the promising prospect of metal-free photocatalysis. We find it to be a near ultraviolet (UV) absorbing direct band gap (3.69 eV) semiconductor with robust dynamical and mechanical stability. Estimating the band positions with respect to water oxidation and hydrogen reduction potential levels along with a detailed analysis of reaction mechanism of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), we observe that g- B 3 C 2 N 3 ${B_3 C_2 N_3 }$ monolayer can be efficiently used for hydrogen fuel generation over entire pH range as well as for spontaneous water splitting at basic pH range. Upon biaxial strain application, band positions get realigned along with the free energy change that is involved in HER and OER. Consequently, operational range of pH for OER gets broadened and the proposed material exhibits the ability to perform spontaneous and simultaneous oxidation and reduction even in neutral pH. The combination of pH variation and applied strain can be used as a key to control the reducing and/or oxidizing abilities precisely for diverse photocatalytic reactions to attain environmental sustainability.

High-Resolution Scanning Electron Microscopy Imaging to Understand the Growth Kinetics of Nickel Nanorods.

In the present work, the growth kinetics of nickel nanorods inside commercially available Whatman nanoporous membrane is explored to achieve uniform deposition over a large area of the membrane. Uniform electrodeposition inside nanopores requires continuous presence of solute ions near the deposition site and reduction of ions. To control ion diffusion and reduction near the deposition site, the effect of DC potential and pulsed potential with various duty cycles and solution temperatures is analyzed. Time-dependent variation in deposition current is recorded for all experiments. For different experimental conditions, high-resolution scanning electron microscopy (SEM) image is acquired. SEM along with the current density profile helped to understand the deposition mechanism for various growth conditions. Experiments confirmed that pulse deposition with a small duty cycle is promising to achieve uniform deposition. Also, by changing the pulse duty cycle, a sectioned nanostructure can be obtained. Based on the electron microscopic observation for various deposition conditions used in this work, it is concluded that initially nickel ions adhere to the pore surfaces due to high surface energy. When a potential is applied, ions reduce and a hollow nanotube structure forms. With time, concentric growth continues by forming a solid nanorod structure.

Light-Induced Hypoxia in Carbon Quantum Dots and Ultrahigh Photocatalytic Efficiency.

Carbon quantum dots (CQDs) represent a class of carbon materials exhibiting photoresponse and many potential applications. Here, we present a unique property that dissolved CQDs capture large amounts of molecular oxygen from the air, the quantity of which can be controlled by light irradiation. The O2 content can be varied between a remarkable 1 wt % of the CQDs in the dark to nearly half of it under illumination, in a reversible manner. Moreover, O2 depletion enhances away from the air-solution interface as the nearby CQDs quickly regain them from the air, creating a pronounced concentration gradient in the solution. We elucidate the role of the CQD functional groups and show that excitons generated under light are responsible for their tunable adsorbed-oxygen content. Because of O2 enrichment, the photocatalytic efficiency of the CQDs toward oxidation of benzylamines in the air is the same as under oxygen flow and far higher than the existing photocatalysts. The findings should encourage the development of a new class of oxygen-enricher materials and air as a sustainable oxidant in chemical transformations.

Scattering Amplitudes: Celestial and Carrollian.

Recent attempts at the construction of holography for asymptotically flat spacetime have taken two different routes. Celestial holography, involving a two dimensional (2D) conformal field theory (CFT) dual to 4D Minkowski spacetime, has generated novel results in asymptotic symmetry and scattering amplitudes. A different formulation, using Carrollian CFTs, has been principally used to provide some evidence for flat holography in lower dimensions. Understanding of flat space scattering has been lacking in the Carroll framework. In this Letter, using ideas from Celestial holography, we show that 3D Carrollian CFTs living on the null boundary of 4D flat space can potentially compute bulk scattering amplitudes. Three-dimensional Carrollian conformal correlators have two different branches, one depending on the null time direction and one independent of it. We propose that it is the time-dependent branch that is related to bulk scattering. We construct an explicit field theoretic example of a free massless Carrollian scalar that realizes some desired properties.

Sulfated Lewis A trisaccharide on oviduct membrane glycoproteins binds bovine sperm and lengthens sperm lifespan.

A fraction of sperm deposited at mating or insemination reaches the oviduct isthmus, where sperm are retained and thereby form a reservoir. This reservoir delays capacitation, prevents polyspermy, selects a fertile population of sperm, and, foremost, increases sperm lifespan. The molecular interactions underlying the formation of a sperm reservoir are becoming clearer in mammals. Sperm lectins bind to oviductal glycans to form the reservoir. Herein, we found that the highest percentage of bovine sperm bound to the 3'-O-sulfated form of Lewis A (suLeA) trisaccharide and sialylated Lewis A and that fluoresceinated versions of each localized to receptors on the anterior head of the sperm. Following capacitation, binding to suLeA decreased significantly, a potential explanation for sperm release from the reservoir. MS and immunohistochemistry analyses indicated that suLeA motifs were present predominantly on O-linked glycans initiated by GalNAc residues, but no sialylated Lewis A was detected. To determine whether sperm binding to isolated suLeAin vitro could mimic in vivo sperm binding to oviduct cells and increase sperm longevity, we immobilized suLeA and incubated it with sperm. Using free-swimming sperm and sperm bound to immobilized laminin as controls, we observed that over 96 h, the viability of free-swimming sperm decreased to 10%, and that of sperm bound to immobilized laminin decreased to about 50%, whereas viability of sperm bound to immobilized suLeA was highest throughout the incubation and 60% at 96 h. These results indicate that bovine sperm binding to oviduct suLeA retains sperm for reservoir formation and extends sperm lifespan.

Molecular analysis of the effects of steroid hormones on mouse meiotic prophase I progression.

BACKGROUND: Infertility is linked to depletion of the primordial follicle pool consisting of individual oocytes arrested at the diplotene stage of meiotic prophase I surrounded by granulosa cells. Primordial germ cells, the oocyte precursors, begin to differentiate during embryonic development. These cells migrate to the genital ridge and begin mitotic divisions, remaining connected, through incomplete cytokinesis, in clusters of synchronously dividing oogonia known as germ cell cysts. Subsequently, they enter meiosis, become oocytes and progress through prophase I to the diplotene stage. The cysts break apart, allowing individual oocytes to be surrounded by a layer of granulosa cells, forming primordial follicles each containing a diplotene arrested oocyte. A large number of oocytes are lost coincident with cyst breakdown, and may be important for quality control of primordial follicle formation. Exposure of developing ovaries to exogenous hormones can disrupt cyst breakdown and follicle formation, but it is unclear if hormones affect progression of oocytes through prophase I of meiosis. METHODS: Fetal ovaries were treated in organ culture with estradiol, progesterone, or both hormones, labeled for MSY2 or Synaptonemal complex protein 3 (SYCP3) using whole mount immunocytochemistry and examined by confocal microscopy. Meiotic prophase I progression was also followed using the meiotic surface spread technique. RESULTS: MSY2 expression in oocytes was reduced by progesterone but not estradiol or the hormone combination. However, while MSY2 expression was upregulated during development it was not a precise marker for the diplotene stage. We also followed meiotic prophase I progression using antibodies against SYCP3 using two different methods, and found that the percent of oocytes at the pachytene stage peaked at postnatal day 1. Finally, estradiol and progesterone treatment together but not either alone in organ culture increased the percent of oocytes at the pachytene stage. CONCLUSIONS: We set out to examine the effects of hormones on prophase I progression and found that while MSY2 expression was reduced by progesterone, MSY2 was not a precise diplotene stage marker. Using antibodies against SYCP3 to identify pachytene stage oocytes we found that progesterone and estradiol together delayed progression of oocytes through prophase I.

Arrest at the diplotene stage of meiotic prophase I is delayed by progesterone but is not required for primordial follicle formation in mice.

BACKGROUND: In mammalian females, reproductive capacity is determined by the size of the primordial follicle pool. During embryogenesis, oogonia divide mitotically but cytokinesis is incomplete so oogonia remain connected in germ cell cysts. Oogonia begin to enter meiosis at 13.5 days postcoitum in the mouse and over several days, oocytes progress through the stages of meiotic prophase I arresting in the diplotene stage. Concurrently, germ cell cysts break apart and individual oocytes become surrounded by granulosa cells forming primordial follicles. In rats, inhibition of a synaptonemal complex protein caused premature arrival at the diplotene stage and premature primordial follicle assembly suggesting diplotene arrest might trigger primordial follicle formation. Cyst breakdown and primordial follicle formation are blocked by exposure to steroid hormones but hormone effects on the timing of diplotene arrest are unclear. Here, we asked: (1) if oocytes were required to arrest in diplotene before follicles formed, (2) if all oocytes within a germ cell cyst arrested at diplotene synchronously, and (3) if steroid hormones affected progression through prophase I. METHODS: Meiotic stage and follicle formation were assessed in histological sections. Statistical differences over time were determined using one-way ANOVA followed by Newman-Keuls multiple comparisons test. To determine if steroid hormones affect the rate of progression to the diplotene stage, 17.5 dpc ovaries were placed in organ culture with media containing estradiol, progesterone or both hormones. In this case, differences were determined using one-way ANOVA followed by Dunnett's multiple comparisons test. RESULTS: We found primordial follicles containing oocytes at the diplotene stage as well as follicles containing oocytes at pre-diplotene stages. We also found individual germ cell cysts containing oocytes at both diplotene and pre-diplotene stages. Progesterone but not estradiol reduced the number of diplotene oocytes in ovary organ culture. CONCLUSIONS: Our results suggest that meiotic progression and primordial follicle formation are independent events. In addition, oocytes in germ cell cysts do not synchronously proceed through meiosis. Finally, only progesterone delayed transit though meiotic prophase I.

Self-limiting layer-by-layer oxidation of atomically thin WSe2.

Growth of a uniform oxide film with a tunable thickness on two-dimensional transition metal dichalcogenides is of great importance for electronic and optoelectronic applications. Here we demonstrate homogeneous surface oxidation of atomically thin WSe2 with a self-limiting thickness from single- to trilayers. Exposure to ozone (O3) below 100 °C leads to the lateral growth of tungsten oxide selectively along selenium zigzag-edge orientations on WSe2. With further O3 exposure, the oxide regions coalesce and oxidation terminates leaving a uniform thickness oxide film on top of unoxidized WSe2. At higher temperatures, oxidation evolves in the layer-by-layer regime up to trilayers. The oxide films formed on WSe2 are nearly atomically flat. Using photoluminescence and Raman spectroscopy, we find that the underlying single-layer WSe2 is decoupled from the top oxide but hole-doped. Our findings offer a new strategy for creating atomically thin heterostructures of semiconductors and insulating oxides with potential for applications in electronic devices.

The steroid hormone environment during primordial follicle formation in perinatal mouse ovaries.

Primordial follicle assembly is essential for reproduction in mammalian females. Oocytes develop in germ cell cysts that in late fetal development begin break down into individual oocytes and become surrounded by pregranulosa cells, forming primordial follicles. As they separate, many oocytes are lost by apoptosis. Exposure to steroid hormones delays cyst breakdown, follicle formation, and associated oocyte loss in some species. One model for regulation of follicle formation is that steroid hormones in the maternal circulation keep cells in cysts and prevent oocyte death during fetal development but that late in pregnancy hormone levels drop, triggering cyst breakdown and associated oocyte loss. However, herein we found that, while maternal circulating levels of progesterone drop during late fetal development, maternal estradiol levels remain high. We hypothesized that fetal ovaries were the source of hormones and that late in fetal development their production stops. To test this, mRNA and protein levels of steroidogenic enzymes required for estradiol and progesterone synthesis were measured. We found that aromatase and 3-beta-hydroxysteroid dehydrogenase mRNA levels drop before cyst breakdown. The 3-beta-hydroxysteroid dehydrogenase protein levels also dropped, but we did not detect a change in aromatase protein levels. The steroid content of perinatal ovaries was assayed, and both estradiol and progesterone were detected in fetal ovaries before cyst breakdown. To determine the role of steroid hormones in oocyte development, we examined the effects of blocking steroid hormone production in organ culture and found that the number of oocytes was reduced, supporting our model that steroid hormones are important for fetal oocyte survival.

Dual inhibition of AKT and ERK1/2 pathways restores the expression of progesterone Receptor-B in endometriotic lesions through epigenetic mechanisms.

Endometriosis is an estrogen-dependent and progesterone-resistant gynecological inflammatory disease of reproductive-age women. Progesterone resistance, loss of progesterone receptor -B (PR-B) in the stromal cells of the endometrium, is one of the hallmarks of endometriosis and a major contributing factor for infertility in endometriosis patients. Loss of PR-B in the stromal cells of the endometriotic lesions poses resistance to the success of progesterone-based therapy. The working hypothesis is that PR-B is hypermethylated and epigenetically silenced, and inhibition of AKT and ERK1/2 pathways will decrease the hypermethylation, reverse the epigenetic silencing, and restore the expression of PR-B via DNA methylation and histone modification mechanisms in the endometriotic lesions. The objectives are to (i) determine the effects of dual inhibition of AKT and ERK1/2 pathways on the expression of PR-B and DNA methylation and histone modification protein machinery in the endometriotic lesions and (ii) identify the underlying epigenetic mechanisms of PR-B restoration in the endometriotic lesions. The results indicate that dual inhibition of AKT and ERK1/2 pathways decreases the hypermethylation, reverses the epigenetic silencing, and restores the expression of PR-B via DNA methylation and H3K9 and H3K27 methylation mechanisms in the endometriotic lesions or endometriotic stromal cells of human origin. These results support the novel concept that restored expression of PR-B in the endometriotic lesions and endometrium may improve the clinical outcome of progesterone therapy in endometriosis patients.

Alteration of epigenetic methyl and acetyl marks by postnatal chromium(VI) exposure causes apoptotic changes in the ovary of the F1 offspring.

Hexavalent chromium, Cr(VI), is a heavy metal endocrine disruptor used widely in various industries worldwide and is considered a reproductive toxicant. Our previous studies demonstrated that lactational exposure to Cr(VI) caused follicular atresia, disrupted steroid hormone biosynthesis and signaling, and delayed puberty. However, the underlying mechanism was unknown. The current study investigated the effects of Cr(VI) exposure (25 ppm) during postnatal days 1-21 via dam's milk on epigenetic alterations in the ovary of F1 offspring. Data indicated that Cr(VI) disrupted follicle development and caused apoptosis by increasing DNMT3a /3b and histone methyl marks (H3K27me3 and H3K9me3) along with decreasing histone acetylation marks (H3K9ac and H3K27ac). Our study demonstrates that exposure to Cr(VI) causes changes in the epigenetic marks, partially contributing to the transcriptional repression of genes regulating ovarian development, cell proliferation (PCNA), cell survival (BCL-XL and BCL-2), and activation of genes regulating apoptosis (AIF and cleaved caspase-3), resulting in follicular atresia. The current study suggests a role for epigenetics in Cr(VI)-induced ovotoxicity and infertility.

Biological control potential of worrisome wheat blast disease by the seed endophytic bacilli.

Crop production often faces challenges from plant diseases, and biological control emerges as an effective, environmentally friendly, cost-effective, and sustainable alternative to chemical control. Wheat blast disease caused by fungal pathogen Magnaporthe oryzae Triticum (MoT), is a potential catastrophic threat to global food security. This study aimed to identify potential bacterial isolates from rice and wheat seeds with inhibitory effects against MoT. In dual culture and seedling assays, three bacterial isolates (BTS-3, BTS-4, and BTLK6A) demonstrated effective suppression of MoT growth and reduced wheat blast severity when artificially inoculated at the seedling stage. Genome phylogeny identified these isolates as Bacillus subtilis (BTS-3) and B. velezensis (BTS-4 and BTLK6A). Whole-genome analysis revealed the presence of genes responsible for controlling MoT through antimicrobial defense, antioxidant defense, cell wall degradation, and induced systemic resistance (ISR). Taken together, our results suggest that the suppression of wheat blast disease by seed endophytic B. subtilis (BTS-3) and B. velezensis (BTS-4 and BTLK6A) is liked with antibiosis and induced systemic resistance to wheat plants. A further field validation is needed before recommending these endophytic bacteria for biological control of wheat blast.

Studies on macrobenthic organisms in relation to water parameters at East Calcutta Wetlands.

East Calcutta Wetlands is an internationally important site for natural remediation of domestic sewage and organic waste and their successful recycling into habitat for pisciculture. Macrobenthic fauna is responsible for efficient utilization of sediments and their diversity indicates health of a wetland in accordance to its sediment quality. In the present study, several physico-chemical parameters such as DO (3.03-11.06 ppm), CO2 (4.02-20.0 ppm), alkalinity (36.83-164.0 ppm), total hardness (100.0-270.00 ppm), TDS (450.0-620 ppm), chloride(142.0-364.2 ppm), pH (7.3-8.5), water transparency (8.0-54.2 cm), organic contents like organic carbon (1.03-10.9 mg g(-1)) were studied. Variation in macrobenthic fauna from the selected fields were also examined by calculating Simpson's dominance index, evenness index (Pielou index), Shannon's diversity index. 12 taxa of mollusk and 1 taxa of annelid were found in the study and Bellamyo and Thiara were the most dominant species which indicated clean water of the pond. The correlation between macrobenthic diversity and physico-chemical parameters were also studied in selected ponds from East Calcutta Wetlands.

Circular dichroism in two-dimensional BC6N and B3C2N3in absence of intervalley excitonic coupling.

Two-dimensional (2D) noncentrosymmetric systems offer potential opportunities for exploiting the valley degrees of freedom for advanced information processing, owing to non-zero Berry curvature. However, such valley polarization in 2D materials is crucially governed by the intervalley excitonic scattering in momentum space due to reduced electronic degrees of freedom and consequent enhanced electronic correlation. Here, we study the valley excitonic properties of two 2D noncentrosymmetric complementary structures, namely, BC6N and B3C2N3using first principles-based GW calculations combined with the Bethe-Salpeter equation, that brings the many-body interactions among the quasiparticles. Thek-resolved oscillator strength of their first bright exciton indicates their ability to exhibit valley polarization under the irradiation of circularly polarized light of different chiralities. Both the systems show significant singlet excitonic binding energies of 0.74 eV and 1.31 eV, respectively. Higher stability of dark triplet excitons as compared to the singlet one can lead to higher quantum efficiency in both the systems. The combination of large excitonic binding energies and the valley polarization ability with minimal intervalley scattering make them promising candidates for applications in advanced optical devices and information storage technologies.

Endocrine disruptors and endometriosis.

Endometriosis is a hormone-dependent inflammatory gynecological disease of reproductive-age women. It is clinically and pathologically characterized by the presence of functional endometrium as heterogeneous lesions outside the uterine cavity. The two major symptoms are chronic pelvic pain and infertility, which profoundly affect women's reproductive health and quality of life. This significant individual and public health concerns underscore the importance of understanding the pathogenesis of endometriosis. The environmental endocrine-disrupting chemicals (EDCs) are exogenous agents that interfere with the synthesis, secretion, transport, signaling, or metabolism of hormones responsible for homeostasis, reproduction, and developmental processes. Endometriosis has been potentially linked to exposure to EDCs. In this review, based on the robust literature search, we have selected four endocrine disruptors (i) polychlorinated biphenyls (PCB)s (ii) dioxins (TCDD) (iii) bisphenol A (BPA) and its analogs and (iv) phthalates to elucidate their critical role in the etiopathogenesis of endometriosis. The epidemiological and experimental data discussed in this review indicate that these four EDCs activate multiple intracellular signaling pathways associated with proinflammation, estrogen, progesterone, prostaglandins, cell survival, apoptosis, migration, invasion, and growth of endometriosis. The available information strongly indicates that environmental exposure to EDCs such as PCBs, dioxins, BPA, and phthalates individually or collectively contribute to the pathophysiology of endometriosis. Further understanding of the molecular mechanisms of how these EDCs establish endometriosis and therapeutic strategies to mitigate the effects of these EDCs in the pathogenesis of endometriosis are timely needed. Moreover, understanding the interactive roles of these EDCs in the pathogenesis of endometriosis will help regulate the exposure to these EDCs in reproductive age women.

Biological Aging Acceleration Due to Environmental Exposures: An Exciting New Direction in Toxicogenomics Research.

Biological clock technologies are designed to assess the acceleration of biological age (B-age) in diverse cell types, offering a distinctive opportunity in toxicogenomic research to explore the impact of environmental stressors, social challenges, and unhealthy lifestyles on health impairment. These clocks also play a role in identifying factors that can hinder aging and promote a healthy lifestyle. Over the past decade, researchers in epigenetics have developed testing methods that predict the chronological and biological age of organisms. These methods rely on assessing DNA methylation (DNAm) levels at specific CpG sites, RNA levels, and various biomolecules across multiple cell types, tissues, and entire organisms. Commonly known as 'biological clocks' (B-clocks), these estimators hold promise for gaining deeper insights into the pathways contributing to the development of age-related disorders. They also provide a foundation for devising biomedical or social interventions to prevent, reverse, or mitigate these disorders. This review article provides a concise overview of various epigenetic clocks and explores their susceptibility to environmental stressors.

Strong Dopant-Dopant Electronic Coupling in Emissive Codoped Two Dimensional Metal Halide Hybrid.

Multimetallic halide hybrids are attractive for the fundamental understanding of interacting excitons. However, realizing halide hybrids that incorporate multiple heterometal centers has been synthetically challenging. This further limits access to gaining physical insight into the electronic coupling mechanism between the constituent metal halide units. Reported herein is an emissive heterometallic halide hybrid, synthesized by codoping (with Mn2+, Sb3+) a 2D host (C6H22N4CdCl6) hybrid, that shows strong dopant-dopant interaction. Here, C6H22N4Sb0.003Mn0.128Cd0.868Cl6 codoped hybrid shows weak green emission (Sb3+ dopant based) and strong orange emission (Mn2+ dopant based). The observed dominance of the Mn2+ dopant emission, arising due to efficient energy transfer between the distant dopants (Sb3+ → Mn2+), highlights strong dopant-dopant electronic coupling. DFT calculations, supporting the observed dopant-dopant interaction, suggest that the electronic coupling between the dopant units (Mn-Cl; Sb-Cl) is mediated by the 2D networked host structure. This work reports physical insight into the coupling mechanism of interacting excitons in multimetallic halide hybrids synthesized through a codoping strategy.

Inhibition of Sirtuin-1 hyperacetylates p53 and abrogates Sirtuin-1-p53 interaction in Cr(VI)-induced apoptosis in the ovary.

Environmental contamination with hexavalent chromium, Cr(VI), has been increasing in the United States as well as in developing countries. Exposure to Cr(VI) predisposes the human population to various diseases, including cancer, infertility, and developmental problems in children. Previous findings from our laboratory reported that prenatal exposure to Cr(VI) caused premature ovarian failure through p53-mediated mechanisms. Sirtuin 1 (SIRT1) is an NAD+ -dependent histone deacetylase class III. SIRT1 deacetylates several histones and non-histone proteins such as p53 and NFkB. The current study determines a role for the SIRT1-p53 network in apoptosis induced by Cr(VI) in the ovary and establishes physical interaction between SIRT1 and p53. Adult pregnant dams were given regular drinking water or Cr(VI) (10 ppm potassium dichromate in drinking water, ad libitum), and treated with SIRT1 inhibitor, EX-527 (50 mg/kg body weight, i.p.,), during 9.5 - 14.5 days post-coitum. On postnatal day-1, ovaries from F1 offspring were collected for various analyses. Results indicated that Cr(VI) increased germ cell and somatic cell apoptosis, upregulated acetyl-p53, activated the apoptotic pathway, and inhibited cell survival pathways. Cr(VI) decreased acetyl-p53-SIRT1 co-localization in the ovary. In an immortalized rat granulosa cell line SIGC, Cr(VI) inhibited the physical interaction between SIRT1 and acetyl-p53 by altering the p53:SIRT1 ratio. EX-527 exacerbated Cr(VI)-induced mechanisms. The current study shows a novel mechanism for Cr(VI)-induced apoptosis in the ovary, mediated through the p53-SIRT1 network, suggesting that targeting the p53 pathway may be an ideal approach to rescue ovaries from Cr(VI)-induced apoptosis.

Antiferromagnetic spin ordering in two-dimensional honeycomb lattice of SiP3.

Magnetism in low-dimensional materials has been of sustained interest due to its intriguing quantum mechanical origin and promising device applications. Here, we propose a buckled honeycomb lattice of stoichiometry SiP3, a two-dimensional binary group-IV and V material that exhibits an antiferromagnetic ground state with itinerant electrons. Here we perform elemental Si substitution in pristine blue phosphorene to downshift the Fermi energy and induce the Fermi instability that results in a spin polarized ground state. Within first-principles calculations, we observe antiferromagnetic spin alignment between adjacent ferromagnetic triangular domains where each Si atom is coupled with three neighboring P atoms with a ferromagnetic interaction. Such unique spin structure and resulting magnetic ground state are unprecedented in defect-free two-dimensional materials made of only p-block elements. This metal-free magnetism can be exploited for advanced spintronic and memory storage applications.

Stress Decreases Host Viral Resistance and Increases Covid Susceptibility in Embryonic Stem Cells.

Stress-induced changes in viral receptor and susceptibility gene expression were measured in embryonic stem cells (ESC) and differentiated progeny. Rex1 promoter-Red Fluorescence Protein reporter ESC were tested by RNAseq after 72hr exposures to control stress hyperosmotic sorbitol under stemness culture (NS) to quantify stress-forced differentiation (SFD) transcriptomic programs. Control ESC cultured with stemness factor removal produced normal differentiation (ND). Bulk RNAseq transcriptomic analysis showed significant upregulation of two genes involved in Covid-19 cell uptake, Vimentin (VIM) and Transmembrane Serine Protease 2 (TMPRSS2). SFD increased the hepatitis A virus receptor (Havcr1) and the transplacental Herpes simplex 1 (HSV1) virus receptor (Pvrl1) compared with ESC undergoing ND. Several other coronavirus receptors, Glutamyl Aminopeptidase (ENPEP) and Dipeptidyl Peptidase 4 (DPP4) were upregulated significantly in SFD>ND. Although stressed ESC are more susceptible to infection due to increased expression of viral receptors and decreased resistance, the necessary Covid-19 receptor, angiotensin converting enzyme (ACE)2, was not expressed in our experiments. TMPRSS2, ENPEP, and DPP4 mediate Coronavirus uptake, but are also markers of extra-embryonic endoderm (XEN), which arise from ESC undergoing ND or SFD. Mouse and human ESCs differentiated to XEN increase TMPRSS2 and other Covid-19 uptake-mediating gene expression, but only some lines express ACE2. Covid-19 susceptibility appears to be genotype-specific and not ubiquitous. Of the 30 gene ontology (GO) groups for viral susceptibility, 15 underwent significant stress-forced changes. Of these, 4 GO groups mediated negative viral regulation and most genes in these increase in ND and decrease with SFD, thus suggesting that stress increases ESC viral susceptibility. Taken together, the data suggest that a control hyperosmotic stress can increase Covid-19 susceptibility and decrease viral host resistance in mouse ESC. However, this limited pilot study should be followed with studies in human ESC, tests of environmental, hormonal, and pharmaceutical stressors and direct tests for infection of stressed, cultured ESC and embryos by Covid-19.