Orbitally relieved magnetic frustration in NaVO2

The magnetic properties of NaVO2 are investigated using full-potential linearized augmented plane wave method. We perform calculations for three structures. For the rhombohedral structure at 100 K, the t2g orbitals of V ions are split into upper a1g and lower e'g orbitals by a trigonal distortion of compression. For the monoclinic structure at 91.5 K, the system behaves like a frustrated spin lattice with spatially anisotropic exchange interactions. For another monoclinic structure at 20 K, the magnetic frustration is relieved by a lattice distortion which is driven by a certain orbital ordering, and the long-range magnetic ordering is thus formed. Moreover, the small magnetic moment originates from the compensation oforbital moment for the spin moment.Comment: Accepted by PR

Variations of Particle Size Distribution, Black Carbon, and Brown Carbon during a Severe Winter Pollution Event over Xi'an, China

Real-time particulate matter (PM) size distributions, 4-hour time resolution, PM2.5, carbonaceous materials, and their optical properties were measured during a severe pollution event in Xi'an, China High PM2.5 /PM10 ratios were observed on both pollution (0.83) and non-pollution (0.73) days, emphasizing the abundance of fine particles during sampling days. The particle number (PN) first peaked with a wide size range (30-100 nm) before morning rush hours (approximately 01:00-05:00) on pollution and non-pollution days, demonstrating that PN was governed by the accumulation of freshly emitted diesel particles and characterized by distinct aerosol condensation growth. By contrast, the second peak time and size range differed between pollution and non-pollution days because of different formation mechanisms The light-absorbing coefficients of both black carbon (BC, b(abs-880nm,BC)) and brown carbon (BrC, b(abs-370nm, BrC)) were high on pollution days and decreased to approximately half of those values on non-pollution days, indicating that the degree of light absorption is reduced by rain. The diurnal variation in b(abs-880nm, BC) pollution peaked with traffic on January 1 and 2. By contrast, it remained in relatively stable and high ranges (120-160 Mm(-1)) in the second period (January 3-5) without traffic peaks, illustrating that the dominant sources changed even during the same pollution period. High values of both b(abs-370nm, BrC) and b(abs-880nm,) (BC )coincided in the afternoon and evening due to emissions from primary sources, and abundant aqueous secondary organic carbon, respectively. A highly variable mass absorption coefficient of BrC also indicated the variety of fuel combustion sources of primary BrC in Xi'an

Balancing selection on an MYB transcription factor maintains the twig trichome color variation in Melastoma normale

Background The factors that maintain phenotypic and genetic variation within a population have received long-term attention in evolutionary biology. Here the genetic basis and evolution of the geographically widespread variation in twig trichome color (from red to white) in a shrub Melastoma normale was investigated using Pool-seq and evolutionary analyses. Results The results show that the twig trichome coloration is under selection in different light environments and that a 6-kb region containing an R2R3 MYB transcription factor gene is the major region of divergence between the extreme red and white morphs. This gene has two highly divergent groups of alleles, one of which likely originated from introgression from another species in this genus and has risen to high frequency (> 0.6) within each of the three populations under investigation. In contrast, polymorphisms in other regions of the genome show no sign of differentiation between the two morphs, suggesting that genomic patterns of diversity have been shaped by homogenizing gene flow. Population genetics analysis reveals signals of balancing selection acting on this gene, and it is suggested that spatially varying selection is the most likely mechanism of balancing selection in this case. Conclusions This study demonstrate that polymorphisms on a single transcription factor gene largely confer the twig trichome color variation in M. normale, while also explaining how adaptive divergence can occur and be maintained in the face of gene flow

General anesthetic action profile on the human prefrontal cortex cells through comprehensive single-cell RNA-seq analysis

The cellular and molecular actions of general anesthetics to induce anesthesia state and also cellular signaling changes for subsequent potential "long term" effects remain largely elusive. General anesthetics were reported to act on voltage-gated ion channels and ligand-gated ion channels. Here we used single-cell RNA-sequencing complemented with whole-cell patch clamp and calcium transient techniques to examine the gene transcriptome and ion channels profiling of sevoflurane and propofol, both commonly used clinically, on the human fetal prefrontal cortex (PFC) mixed cell cultures. Both propofol and sevoflurane at clinically relevant dose/concentration promoted "microgliosis" but only sevoflurane decreased microglia transcriptional similarity. Propofol and sevoflurane each extensively but transiently (<2 h) altered transcriptome profiling across microglia, excitatory neurons, interneurons, astrocytes and oligodendrocyte progenitor cells. Utilizing scRNA-seq as a robust and high-through put tool, our work may provide a comprehensive blueprint for future mechanistic studies of general anesthetics in clinically relevant settings

Search for the decay J/ψ→γ+invisibleJ/\psi\to\gamma + \rm {invisible}

We search for $J/\psi$ radiative decays into a weakly interacting neutral particle, namely an invisible particle, using the $J/\psi$ produced through the process $\psi(3686)\to\pi^+\pi^-J/\psi$ in a data sample of $(448.1\pm2.9)\times 10^6$ $\psi(3686)$ decays collected by the BESIII detector at BEPCII. No significant signal is observed. Using a modified frequentist method, upper limits on the branching fractions are set under different assumptions of invisible particle masses up to 1.2 $\mathrm{\ Ge\kern -0.1em V}/c^2$. The upper limit corresponding to an invisible particle with zero mass is 7.0$\times 10^{-7}$ at the 90\% confidence level

Graphite and Hexagonal Boron-Nitride Possess the Same Interlayer Distance. Why?

Graphite and hexagonal boron nitride (h-BN) are two prominent members of the family of layered materials possessing a hexagonal lattice. While graphite has non-polar homo-nuclear C-C intra-layer bonds, h-BN presents highly polar B-N bonds resulting in different optimal stacking modes of the two materials in bulk form. Furthermore, the static polarizabilities of the constituent atoms considerably differ from each other suggesting large differences in the dispersive component of the interlayer bonding. Despite these major differences both materials present practically identical interlayer distances. To understand this finding, a comparative study of the nature of the interlayer bonding in both materials is presented. A full lattice sum of the interactions between the partially charged atomic centers in h-BN results in vanishingly small monopolar electrostatic contributions to the interlayer binding energy. Higher order electrostatic multipoles, exchange, and short-range correlation contributions are found to be very similar in both materials and to almost completely cancel out by the Pauli repulsions at physically relevant interlayer distances resulting in a marginal effective contribution to the interlayer binding. Further analysis of the dispersive energy term reveals that despite the large differences in the individual atomic polarizabilities the hetero-atomic B-N C6 coefficient is very similar to the homo-atomic C-C coefficient in the hexagonal bulk form resulting in very similar dispersive contribution to the interlayer binding. The overall binding energy curves of both materials are thus very similar predicting practically the same interlayer distance and very similar binding energies.Comment: 18 pages, 5 figures, 2 table