Fluctuation-Driven Vortex Fractionalization in Topologically Ordered Superfluids of Cold Atoms

We have studied spin structures of fluctuation-driven fractionalized vortices and topological spin order in 2D nematic superfluids of cold sodium atoms. Our Monte Carlo simulations suggest a softened pi-spin disclination structure in a half-quantum vortex when spin correlations are short ranged; in addition, calculations indicate that a unique non-local topological spin order emerges simultaneously as cold atoms become a superfluid below a critical temperature. We have also estimated fluctuation-dependent critical frequencies for half-quantum vortex nucleation in rotating optical traps and discussed probing these excitations in experiments.Comment: 5 pages, 2 figures; revised version accepted by Europhysics Letter

Photochemistry of CO and H_2O: Analysis of Laboratory Experiments and Applications to the Prebiotic Earth's Atmosphere

The role photochemical reactions in the early Earth's atmosphere played in the prebiotic synthesis of simple organic molecules was examined. We have extended an earlier calculation of formaldehyde production rates to more reduced carbon species, such as methanol, methane, and acetaldehyde. We have simulated the experimental results of Bar-Nun and Chang (1983) as an aid in the construction of our photochemical scheme and as a way of validating our model. Our results indicate that some fraction of CO_2 and H_2 present in the primitive atmosphere could have been converted to simple organic molecules. The exact amount is dependent on the partial pressure of CO_2 and H_2 in the atmosphere and on what assumptions are made concerning the shape of the absorption spectra of CO_2 and H_2O. In particular, the results are most sensitive to the presence or absence of absorption at wavelengths longward of 2000 Å. We also find that small quantities of CH_4 could have been present in the prebiotic Earth's atmosphere as the result of the photoreduction of CO

Manipulation of Host Quality and Defense by a Plant Virus Improves Performance of Whitefly Vectors

Pathogen-mediated interactions between insect vectors and their host plants can affect herbivore fitness and the epidemiology of plant diseases. While the role of plant quality and defense in mediating these tripartite interactions has been recognized, there are many ecologically- and economically-important cases where the nature of the interaction has yet to be characterized. The Bemisia tabaci cryptic species MED is an important vector of tomato yellow leaf curl virus (TYLCV), and performs better on virus-infected tomato than on uninfected controls. We assessed the impact of TYLCV infection on plant quality and defense, and the direct impact of TYLCV infection on MED feeding. We found that although TYLCV infection has a minimal direct impact on MED, the virus alters the nutritional content of leaf tissue and phloem sap in a manner beneficial to MED. TYLCV infection also suppresses herbivore-induced production of plant defensive enzymes and callose deposition. The strongly positive net effect on TYLCV on MED is consistent with previously-reported patterns of whitefly behavior and performance, and provides a foundation for further exploration of the molecular mechanisms responsible for these effects and the evolutionary processes that shape them

Two-dimensional atmospheric transport and chemistry model: Numerical experiments with a new advection algorithm

Extensive testing of the advective scheme, proposed by Prather (1986), has been carried out in support of the California Institute of Technology–Jet Propulsion Laboratory two-dimensional model of the middle atmosphere. We generalize the original scheme to include higher-order moments. In addition, we show how well the scheme works in the presence of chemistry as well as eddy diffusion. Six types of numerical experiments including simple clock motion and pure advection in two dimensions have been investigated in detail. By comparison with analytic solutions it is shown that the new algorithm can faithfully preserve concentration profiles, has essentially no numerical diffusion, and is superior to a typical fourth-order finite difference scheme

Hydrogen and Deuterium Loss from the Terrestrial Atmosphere: A Quantitative Assessment of Nonthermal Escape Fluxes

A comprehensive one-dimensional photochemical model extending from the middle atmosphere (50 km) to the exobase (432 km) has been used to study the escape of hydrogen and deuterium from the Earth's atmosphere. The model incorporates recent advances in chemical kinetics as well as atmospheric observations by satellites, especially the Atmosphere Explorer C satellite. The results suggest: (1) the escape fluxes of both H and D are limited by the upward transport of total hydrogen and total deuterium at the homopause (this result is known as Hunten's limiting flux theorem); (2) about one fourth of total hydrogen escape is thermal, the rest being nonthermal; (3) escape of D is nonthermal; and (4) charge exchange and polar wind are important mechanisms for the nonthermal escape of H and D, but other nonthermal mechanisms may be required. The efficiency to escape from the terrestrial atmosphere for D is 0.74 of the efficiency for H. If the difference between the D/H ratio measured in deep-sea tholeiite glass and that of standard sea water, δD = −77‰, were caused by the escape of H and D, we estimate that as much water as the equivalent of 36% of the present ocean might have been lost in the past

Effects of isospin and momentum dependent interactions on thermal properties of asymmetric nuclear matter

Thermal properties of asymmetric nuclear matter are studied within a self-consistent thermal model using an isospin and momentum dependent interaction (MDI) constrained by the isospin diffusion data in heavy-ion collisions, a momentum-independent interaction (MID), and an isoscalar momentum-dependent interaction (eMDYI). In particular, we study the temperature dependence of the isospin-dependent bulk and single-particle properties, the mechanical and chemical instabilities, and liquid-gas phase transition in hot asymmetric nuclear matter. Our results indicate that the temperature dependence of the equation of state and the symmetry energy are not so sensitive to the momentum dependence of the interaction. The symmetry energy at fixed density is found to generally decrease with temperature and for the MDI interaction the decrement is essentially due to the potential part. It is further shown that only the low momentum part of the single-particle potential and the nucleon effective mass increases significantly with temperature for the momentum-dependent interactions. For the MDI interaction, the low momentum part of the symmetry potential is significantly reduced with increasing temperature. For the mechanical and chemical instabilities as well as the liquid-gas phase transition in hot asymmetric nuclear matter, our results indicate that the boundary of these instabilities and the phase-coexistence region generally shrink with increasing temperature and is sensitive to the density dependence of the symmetry energy and the isospin and momentum dependence of the nuclear interaction, especially at higher temperatures.Comment: 21 pages, 29 figure

Effects of environmental parameters to total, quantum and classical correlations

We quantify the total, quantum, and classical correlations with entropic measures, and quantitatively compare these correlations in a quantum system, as exemplified by a Heisenberg dimer which is subjected to the change of environmental parameters: temperature and nonuniform external field. Our results show that the quantum correlation may exceed the classical correlation at some nonzero temperatures, though the former is rather fragile than the later under thermal fluctuation. The effect of the external field to the classical correlation is quite different from the quantum correlation.Comment: 6 pages, 4 figure

Cloning and molecular characterization of TaAGO1, a member of argonaute gene family in wheat (Triticum aestivum L.)

Argonaute (AGO) proteins play important roles in RNA silencing processes through formation of complexes with the mature microRNAs. In this study, a wheat AGO gene referred to TaAGO1, which shares high similarities to AtAGO1 in Arabidopsis and OsAGO1 in rice, was characterized. As a cDNA full length of 3747 bp, TaAGO1 encodes a 1099-aa polypeptide with a molecular weight of 122 kD and an isoelectric point (pI) of 9.52. Subcellular prediction analysis suggests that TaAGO1 is to target onto the cytoplasm after endoplasmic reticulum (ER) sorted. Similar to AtAGO1 and OsAGO1, TaAGO1 contains PIWI and DDH, two conserved domains in AGOs. Phylogenetic analysis indicated that TaAGO1 was possibly derived from different progenitors with its homologous across diverse plant species. The transcripts of TaAGO1 were significantly regulated by the stresses of phosphorus deprivation and dehydration, and exogenous treatment of abscisic acid (ABA), suggesting that this wheat AGO member also exerts roles on mediating above signaling transductions. Southern blotting analysis revealed that genome AA, SS, and DD, three diploids composing of the hexaploid wheat, all harbored two copies of TaAGO1. Down-regulation of TaAGO1 in wheat led to conspicuously phenotypic alterations of the young plantlets, with a variety of abnormal growth features. Taking the results in this study together, it was implicated that TaAGO1 exists as a subset of copies in wheat and plays critical roles on silencing of appropriate target genes via regulation of TaAGO1-MiRNAs complex formation.Key words: Wheat (Triticum aestivum L.), argonaute (AGO) gene 1, cloning, molecular characterization, antisense expression

Phosphoregulation of the cytokinetic protein Fic1 contributes to fission yeast growth polarity establishment

© 2020. Published by The Company of Biologists Ltd. Cellular polarization underlies many facets of cell behavior, including cell growth. The rod-shaped fission yeast Schizosaccharomyces pombe is a well-established, genetically tractable system for studying growth polarity regulation. S. pombe cells elongate at their two cell tips in a cell cycle-controlled manner, transitioning from monopolar to bipolar growth in interphase when new ends established by the most recent cell division begin to extend. We previously identified cytokinesis as a critical regulator of new end growth and demonstrated that Fic1, a cytokinetic factor, is required for normal polarized growth at new ends. Here, we report that Fic1 is phosphorylated on two C-terminal residues, which are each targeted by multiple protein kinases. Endogenously expressed Fic1 phosphomutants cannot support proper bipolar growth, and the resultant defects facilitate the switch into an invasive pseudohyphal state. Thus, phosphoregulation of Fic1 links the completion of cytokinesis to the re-establishment of polarized growth in the next cell cycle. These findings broaden the scope of signaling events that contribute to regulating S. pombe growth polarity, underscoring that cytokinetic factors constitute relevant targets of kinases affecting new end growth.This article has an associated First Person interview with Anthony M. Rossi, joint first author of the paper