2,096 research outputs found
Freezing of Simple Liquid Metals
Freezing of simple liquid metals and the relative stabilities of competing
crystalline solids are investigated using thermodynamic perturbation theory,
the interactions between ions being modeled by effective pair potentials
derived from pseudopotential theory. The ionic free energy of the solid phase
is calculated, to first order in the perturbation potential, using classical
density-functional theory and an accurate approximation to the hard-sphere
radial distribution function. Free energy calculations for Na, Mg, and Al yield
well-defined freezing transitions and structural free energy differences for
bcc, fcc, and hcp crystals in qualitative agreement with experiment.Comment: 8 pages, 4 figures, LaTeX with elsart.st
Unusual Ground State Properties of the Kondo-Lattice Compound Yb2Ir3Ge5
We report sample preparation, structure, electrical resistivity, magnetic
susceptibility and heat capacity studies of a new compound YbIrGe.
We find that this compound crystallizes in an orthorhombic structure with a
space group PMMN unlike the compound CeIrGe which crystallizes in
the tetragonal IBAM (UCoSi type) structure. Our resistivity
measurements indicate that the compound YbIrGe behaves like a
typical Kondo lattice system with no ordering down to 0.4 K. However, a
Curie-Weiss fit of the inverse magnetic susceptibility above 100 K gives an
effective moment of only 3.66 which is considerably less than the
theoretical value of 4.54 for magnetic Yb ions. The value of
= -15.19 K is also considerably higher indicating the presence of
strong hybridization. An upturn in the low temperature heat capacity gives an
indication that the system may order magnetically just below the lowest
temperature of our heat capacity measurements (0.4 K). The structure contains
two sites for Yb ions and the present investigation suggests that Yb may be
trivalent in one site while it may be significantly lower (close to divalent)
in the other.Comment: 9 pages, 4 figures. submitted to Phys. Rev.
Diversity and regulatory impact of copy number variation in the primate Macaca fascicularis.
Copy number variations (CNVs) are a significant source of genetic diversity and commonly found in mammalian genomes. We have generated a genome-wide CNV map for Cynomolgus monkeys (Macaca fascicularis). This crab-eating macaque is the closest animal model to humans that is used in biomedical research.
We show that Cynomolgus monkey CNVs are in general much smaller in size than gene loci and are specific to the population of origin. Genome-wide expression data from five vitally important organs demonstrates that CNVs in close proximity to transcription start sites associate strongly with expression changes. Among these eQTL genes we find an overrepresentation of genes involved in metabolism, receptor activity, and transcription.
These results provide evidence that CNVs shape tissue transcriptomes in monkey populations, potentially offering an adaptive advantage. We suggest that this genetic diversity should be taken into account when using Cynomolgus macaques as models
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Response of wheat cultivars to foliar potassium fertilization under irrigated saline environment
A field experiment with split-split plot design (SSPD) was conducted to study the response of two winter wheat (Triticumaestivum L.) cultivars (viz. salt tolerant cultivar KRL-1-4 and salt non-tolerant cultivar HD-2894) under saline irrigation regimes with and without foliar potassium fertilization on growth and grain yield of wheat during rabi 2011-12 and 2012-13. Potassium in the ratio of K+: Na+ (1: 10) was applied as foliar application during the heading stage of the crop. Results showed that the grain yield of KRL-1-4 and HD-2894 cultivars with foliar potassium fertilization at the heading stage increased by 6.5 to 22% and 3 to 15% during rabi 2011-2012, respectively under different saline irrigation regimes as compared to the control. Moreover, the results of rabi 2012-13 showed an increase in grain yield ranging from 4.5 to 20% for KRL-1-4 as compared to the control. Statistical analysis of grain yield parameter showed that the foliar potassium application in both varieties resulted in significant yield difference at 0.05 probability level as compared to the non-foliar application. Overall, it was observed that the foliar potassium fertilization increased the grain yield of both wheat cultivars, while the salt tolerant cultivar performed better than the salt non-tolerant cultivar under irrigated saline regimes
Optimization of an isolated photo-voltaic generating unit with battery energy storage system using electric system cascade analysis
This paper presents an improvement to the iterative method of electric system cascade analysis (ESCA) for the optimisation of an isolated PV system with battery energy storage system (BESS) for a residential load. The ESCA algorithm is implemented on MATLAB software environment with Final Excess Energy (FEE), Loss of Power Supply Probability (LPSP) and system cost as optimization constraints. The load, temperature and solar radiation profiles are considered for a year, based on historical data. Practical losses in solar radiation reaching the PV collector surface are considered for analysis. Change in PV efficiency due to variation in temperature and change in charge/discharge efficiency of the battery based on current state of charge (SOC) of BESS are taken into consideration which further bolsters the credibility of the ESCA methodology. The ESCA methodology is used to optimize a PV-BESS system for a residential load with average daily consumption of 26.1 kWh. The optimized result obtained from improved ESCA are compared and verified with benchmark HOMER software.http://www.elsevier.com/locate/epsr2019-11-01hj2018Electrical, Electronic and Computer Engineerin
Synthesis and characterization of Na03RhO206H2O - a semiconductor with a weak ferromagnetic component
We have prepared the oxyhydrate Na03RhO206H2O by extracting Na+ cations from
NaRhO2 and intercalating water molecules using an aqueous solution of Na2S2O8.
Synchrotron X-ray powder diffraction, thermogravimetric analysis (TGA), and
energy-dispersive x-ray analysis (EDX) reveal that a non-stoichiometric
Na03(H2O)06 network separates layers of edge-sharing RhO6 octahedra containing
Rh3+(4d6, S=0) and Rh4+ (4d5, S=1/2). The resistivities of NaRhO2 and
Na03RhO206H2O (T < 300) reveal insulating and semi-conducting behavior with
activation gaps of 134 meV and 7.8 meV, respectively. Both Na03RhO206H2O and
NaRhO2 show paramagnetism at room temperature, however, the sodium-deficient
sample exhibits simultaneously a weak but experimentally reproducible
ferromagnetic component. Both samples exhibit a temperature-independent Pauli
paramagnetism, for NaRhO2 at T > 50 K and for Na03RhO206H2O at T > 25 K. The
relative magnitudes of the temperature-independent magnetic susceptibilities,
that of the oxide sample being half that of the oxyhydrate, is consistent with
a higher density of thermally accessible electron states at the Fermi level in
the hydrated sample. At low temperatures the magnetic moments rise sharply,
providing evidence of localized and weakl -ordered electronic spins.Comment: 15 fages 5 figures Solid State Communications in prin
Magnetic Ordering and Superconductivity in the REIrGe (RE = Y, La-Tm, Lu) System
We find that the compounds for RE = Y, La-Dy, crystallize in the tetragonal
Ibam (UCoSi type) structure whereas the compounds for RE = Er-Lu,
crystallize in a new orthorhombic structure with a space group Pmmn. Samples of
HoIrGe were always found to be multiphase. The compounds for RE = Y
to Dy which adopt the Ibam type structure show a metallic resistivity whereas
the compounds with RE = Er, Tm and Lu show an anomalous behavior in the
resistivity with a semiconducting increase in as we go down in
temperature from 300K. Interestingly we had earlier found a positive
temperature coefficient of resistivity for the Yb sample in the same
temperature range. We will compare this behavior with similar observations in
the compounds RERuGe and REBiPt. LaIrGe and
YIrGe show bulk superconductivity below 1.8K and 2.5K respectively.
Our results confirm that CeIrGe shows a Kondo lattice behavior and
undergoes antiferromagnetic ordering below 8.5K. Most of the other compounds
containing magnetic rare-earth elements undergo a single antiferromagnetic
transition at low temperatures (T12K) while GdIrGe,
DyIrGe and NdIrGe show multiple transitions. The
T's for most of the compounds roughly scale with the de Gennes factor.
which suggests that the chief mechanism of interaction leading to the magnetic
ordering of the magnetic moments may be the RKKY interaction.Comment: 25 pages, 16 figure
Antiferromagnetic ordering in the Kondo lattice system YbFeSi
Compounds belonging to the RFeSi series exhibit unusual
superconducting and magnetic properties. Although a number of studies have been
made on the first reentrant antiferromagnet superconductor TmFeSi,
the physical properties of YbFeSi are largely unexplored. In this
work, we attempt to provide a comprehensive study of bulk properties such as,
resistivity, susceptibility and heat-capacity of a well characterized
polycrystalline YbFeSi. Our measurements indicate that Yb
moments order antiferromagnetically below 1.7 K. Moreover, the system behaves
as a Kondo lattice with large Sommerfeld coefficient () of 0.5~J/Yb mol
K at 0.3 K, which is well below T. The absence of superconductivity
in YbFeSi down to 0.3 K at ambient pressure is attributed to the
presence of the Kondo effect.Comment: 10 pages, 3 figures, tex document. A fuller version has appeared in
PRB. Here we have omitted the figures showing the crystal structure and the
fitting of the X-ray pattern. Also the table with the lattice parameters
obtained from fitting has been remove
Structural phase control of (LaNdSr)CuO thin films by epitaxial growth technique
Epitaxial growth of (LaNdSr)CuO thin films was
studied by pulsed-laser deposition technique on three different substrates,
SrTiO (100), LaSrAlO (001), and YAlO (001). The
(Nd,Sr,Ce)CuO-type structure appears at the initial growth stage on
SrTiO (100) when the film is deposited under the growth conditions
optimized for (La,Sr)CuO. This (Nd,Sr,Ce)CuO-type structure can
be eliminated by increasing the substrate temperature and the laser repetition
frequency. Films on LaSrAlO (001) maintain a LaCuO-type structure
as bulk samples, but those on YAlO (001) show phase separation into
LaCuO- and NdCuO-type structures. Such complicated results are
explained in terms of the competition between lattice misfit and thermodynamic
conditions. Interestingly the films with LaCuO-type structure prepared
on SrTiO and LaSrAlO show different surface structures and transport
properties. The results indicate the possibility of controlling charge stripes
of (LaNdSr)CuO as was demonstrated in
(La,Ba)CuO thin films by Sato et al. (Phys. Rev. B {\bf 62}, R799
(2000)).Comment: 5 pages, 6 EPS figure, accepted for publication in Phys. Rev.
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