4,082 research outputs found
CARE1, a TY3-gypsy long terminal repeat retrotransposon in the food legume chickpea (Cicer arietinum L)
We report a novel Ty3-gypsy long terminal repeat retrotransposon CARE1 (_Cicer arietinum_ retro-element 1) in chickpea. This 5920-bp AT-rich (63%) element carries 723-bp 5' and 897-bp 3' LTRs respectively flanking an internal region of 4300-bp. The LTRs of CARE1 show 93.9% nucleotide identity to each other and have 4-bp (ACTA) terminal inverted repeats. A 17-bp potential tRNAmet primer binding site downstream to 5' LTR and a 13-bp polypurine tract upstream to 3' LTR have been identified. The order of domains (Gag-proteinase-reverse transcriptase-RNaseH-integrase) in the deduced amino acid sequence and phylogenetic tree constructed using reverse transcriptase sequences places CARE1 in the gypsy group of retrotransposons. Homologues of a number of _cis_-elements including CCAAT, TATA and GT-1 have been detected in the regulatory region or the 5' LTR of CARE1. Transgenic tobacco plants containing 5' LTR:GUS construct show that its 5'-LTR is inactive in a heterologous system under normal as well as tissue culture conditions. Genomic Southern blot experiments using 5’LTR of the element as a probe show that CARE1 or its related elements are present in the genomes of various chickpea accessions from various geographic regions
Better band gaps for wide-gap semiconductors from a locally corrected exchange-correlation potential that nearly eliminates self-interaction errors
This work constitutes a comprehensive and improved account of
electronic-structure and mechanical properties of silicon-nitride (Si3N4)
polymorphs via van Leeuwen and Baerends (LB) exchange-corrected local density
approximation (LDA) that enforces the exact exchange potential asymptotic
behavior. The calculated lattice constant, bulk modulus, and electronic band
structure of Si3N4 polymorphs are in good agreement with experimental results.
We also show that, for a single electron in a hydrogen atom, spherical well, or
harmonic oscillator, the LB-corrected LDA reduces the (self-interaction) error
to exact total energy to ~10%, a factor of three to four lower than standard
LDA, due to a dramatically improved representation of the exchange-potential.Comment: 6 pages, 3 figure
Counting Black Holes: The Cosmic Stellar Remnant Population and Implications for LIGO
We present an empirical approach for interpreting gravitational wave signals
of binary black hole mergers under the assumption that the underlying black
hole population is sourced by remnants of stellar evolution. Using the observed
relationship between galaxy mass and stellar metallicity, we predict the black
hole count as a function of galaxy stellar mass. We show, for example, that a
galaxy like the Milky Way should host millions of black holes
and dwarf satellite galaxies like Draco should host such remnants,
with weak dependence on the assumed IMF and stellar evolution model. Most
low-mass black holes () typically reside within massive
galaxies () while massive black holes () typically reside within dwarf galaxies () today. If roughly of black holes are involved in a binary black
hole merger, then the reported merger rate densities from Advanced LIGO can be
accommodated for a range of merger timescales, and the detection of mergers
with black holes should be expected within the next decade.
Identifying the host galaxy population of the mergers provides a way to
constrain both the binary neutron star or black hole formation efficiencies and
the merger timescale distributions; these events would be primarily localized
in dwarf galaxies if the merger timescale is short compared to the age of the
universe and in massive galaxies otherwise. As more mergers are detected, the
prospect of identifying the host galaxy population, either directly through the
detection of electromagnetic counterparts of binary neutron star mergers or
indirectly through the anisotropy of the events, will become a realistic
possibility.Comment: 10 pages, 8 figures. Accepted by MNRA
Dynamics of a passive sliding particle on a randomly fluctuating surface
We study the motion of a particle sliding under the action of an external
field on a stochastically fluctuating one-dimensional Edwards-Wilkinson
surface. Numerical simulations using the single-step model shows that the
mean-square displacement of the sliding particle shows distinct dynamic scaling
behavior, depending on whether the surface fluctuates faster or slower than the
motion of the particle. When the surface fluctuations occur on a time scale
much smaller than the particle motion, we find that the characteristic length
scale shows anomalous diffusion with , where from numerical data. On the other hand, when the particle moves faster
than the surface, its dynamics is controlled by the surface fluctuations and
. A self-consistent approximation predicts that the
anomalous diffusion exponent is , in good agreement with simulation
results. We also discuss the possibility of a slow cross-over towards
asymptotic diffusive behavior. The probability distribution of the displacement
has a Gaussian form in both the cases.Comment: 6 pages, 4 figures, error in reference corrected and new reference
added, submitted to Phys. Rev.
Better Band Gaps with Asymptotically Corrected Local Exchange Potentials
We formulate a spin-polarized van Leeuwen and Baerends (vLB) correction to
the local density approximation (LDA) exchange potential [Phys. Rev. A 49, 2421
(1994)] that enforces the ionization potential (IP) theorem following Stein et
al. [Phys. Rev. Lett. 105, 266802 (2010)]. For electronic-structure problems,
the vLB-correction replicates the behavior of exact-exchange potentials, with
improved scaling and well-behaved asymptotics, but with the computational cost
of semi-local functionals. The vLB+IP corrections produces large improvement in
the eigenvalues over that from LDA due to correct asympotic behavior and atomic
shell structures, as shown on rare-gas, alkaline-earth, zinc-based oxides,
alkali-halides, sulphides, and nitrides. In half-Heusler alloys, this
asymptotically-corrected LDA reproduces the spin-polarized properties
correctly, including magnetism and half-metallicity. We also considered
finite-sized systems [e.g., ringed boron-nitirde (BN) and
graphene (C)] to emphasize the wide applicability of the method.Comment: 9 pages, 3 figure
Dark Matter from Early Decays
Two leading dark matter candidates from supersymmetry and other theories of
physics beyond the standard model are WIMPs and weak scale gravitinos. If the
lightest stable particle is a gravitino, then a WIMP will decay into it with a
natural lifetime of order a month ~ M_{pl}^2/M_{weak}^3. We show that if the
bulk of dark matter today came from decays of neutral particles with lifetimes
of order a year or smaller, then it could lead to a reduction in the amount of
small scale substructure, less concentrated halos and constant density cores in
the smallest mass halos. Such beneficial effects may therefore be realized
naturally, as discussed by Cembranos, Feng, Rajaraman, and Takayama, in the
case of supersymmetry.Comment: Matches version accepted for publication in PRD. Added a paragraph to
Sec V. 9 pages, 3 figure
In Vitro screening of tomato genotypes for drought resistance using polyethylene glycol
Drought is a major abiotic factor that limits plant growth and productivity. Tomato is an important vegetable crop and area under production is limited by irrigation water scarcity. Effort was made toscreen tomato germplasm under in vitro condition using polyethylene glycol (PEG) at four concentrations (0, 20, 40 and 60 g/l) with two replications in factorial CRD. Important seedling characters like root length and weight; shoot length and weight were recorded. Drought resistant mutant derivatives and hybrid produced using mutant derivative as female parent performed significantly superior for root characters. Decrease in seedling growth was worth notice with increasing concentration of PEG indicating precise nature of the in vitro screening. Mutant hybrid and its derivatives were observed with outstanding ability to continue root growth under in vitro stressconditions indicating there ability to fight with sever water stress situation. These results were further confirmed for early indication traits in raised bed seedlings and fully-grown mature plants under fieldconditions. At all three experimental conditions, mutant derivatives and hybrids performed better than cultivated genotypes under all levels of water stress. Based on results, Hy-3 and MTG 1-4 were foundto be drought resistant due to there remarkable performance at all levels of water stress. This in vitro screening method is potential and cost effective method to screen large set of germplasm within veryless time period and accurately
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