7,287 research outputs found
Maximal Entanglement of Two-qubit States Constructed by Linearly Independent Coherent States
In this paper, we find the necessary and sufficient condition for the maximal
entanglement of the state, constructed by linearly independent
coherent states with \emph{real parameters} when
. This is a further generalization of the
classified nonorthogonal states discussed in Ref. Physics Letters A {\bf{291}},
73-76 (2001).Comment: some examples added; Int J Theor Phys 201
Magnetic Properties and Magnetocaloric Effect in Layered NdMn1.9Ti0.1Si2
The structural and magnetic properties of the NdMn1.9Ti0.1Si2 compund have been studied by high-intensity x-ray and high-resolution neutron powder diffraction, specific heat, dc magnetization, and differential scanning calorimetry measurements over the temperature range of 3-450 K. The Curie temperature and NĂ©el temperature of layered NdMn1.9Ti0.1Si2 are indicated as TC ~ 22 K and TN ~ 374 K respectively. The first order magnetic transition from antiferromagnetic [AFil-type] to ferromagnetic [F(Nd)+Fmc] around TC is found in layered NdMn1.9Ti0.1Si2and is associated with large magnetocaloric effect. This behavior has been confirmed as a contribution of the magnetostructural coupling by using neutron and x-ray powder diffraction. The magnetic entropy change âÎSM ~ 15.3 J kg-1 K-1 and adiabatic temperature change ÎTad ~ 4.7 K have been determined using magnetization and specific heat measurement under 0-5 T applied fields. This compound exhibits almost no thermal and magnetic hysteresis, thus potentially applicable in low temperature region for magnetic refrigerator material.Received: 31 December 2013; Revised:10 February 2014; Accepted: 24 February 201
Connected Green function approach to ground state symmetry breaking in -theory
Using the cluster expansions for n-point Green functions we derive a closed
set of dynamical equations of motion for connected equal-time Green functions
by neglecting all connected functions higher than order for the
-theory in dimensions. We apply the equations to the
investigation of spontaneous ground state symmetry breaking, i.e. to the
evaluation of the effective potential at temperature . Within our momentum
space discretization we obtain a second order phase transition (in agreement
with the Simon-Griffith theorem) and a critical coupling of
as compared to a first order phase transition and
from the Gaussian effective potential approach.Comment: 25 Revtex pages, 5 figures available via fpt from the directory
ugi-94-11 of [email protected] as one postscript file (there
was a bug in our calculations, all numerical results and figures have changed
significantly), ugi-94-1
Analysis of the vector form factors and with light-cone QCD sum rules
In this article, we calculate the vector form factors and
within the framework of the light-cone QCD sum rules
approach. The numerical values of the are compatible with the
existing theoretical calculations, the central value of the ,
, is in excellent agreement with the values from the chiral
perturbation theory and lattice QCD. The values of the are
very large comparing with the theoretical calculations and experimental data,
and can not give any reliable predictions. At large momentum transfers with
, the form factors and can
either take up the asymptotic behavior of or decrease more
quickly than , more experimental data are needed to select the
ideal sum rules.Comment: 22 pages, 16 figures, revised version, to appear in Eur. Phys. J.
A New Cosmological Model of Quintessence and Dark Matter
We propose a new class of quintessence models in which late times
oscillations of a scalar field give rise to an effective equation of state
which can be negative and hence drive the observed acceleration of the
universe. Our ansatz provides a unified picture of quintessence and a new form
of dark matter we call "Frustrated Cold Dark Matter" (FCDM). FCDM inhibits
gravitational clustering on small scales and could provide a natural resolution
to the core density problem for disc galaxy halos. Since the quintessence field
rolls towards a small value, constraints on slow-roll quintessence models are
safely circumvented in our model.Comment: Revised. Important new results added in response to referees comment
Characterization of a wheat HSP70 gene and its expression in response to stripe rust infection and abiotic stresses
Members of the family of 70-kD heat shock proteins (HSP70 s) play various stress-protective roles in plants. In this study, a wheat HSP70 gene was isolated from a suppression subtractive hybridization (SSH) cDNA library of wheat leaves infected by Puccinia striiformis f. sp. tritici. The gene, that was designated as TaHSC70, was predicted to encode a protein of 690 amino acids, with a molecular mass of 73.54 KDa and a pI of 5.01. Further analysis revealed the presence of a conserved signature that is characteristic for HSP70s and phylogenetic analysis demonstrated that TaHSC70 is a homolog of chloroplast HSP70s. TaHSC70 mRNA was present in leaves of both green and etiolated wheat seedlings and in stems and roots. The transcript level in roots was approximately threefold less than in leaves but lightâdark treatment did not charge TaHSC70 expression. Following heat shock of wheat seedlings at 40°C, TaHSC70 expression increased in leaves of etiolated seedlings but remained stable at the same level in green seedlings. In addition, TaHSC70 was differentially expressed during an incompatible and compatible interaction with wheat-stripe rust, and there was a transient increase in expression upon treatment with methyl jasmonate (MeJA) treatment. Salicylic acid (SA), ethylene (ET) and abscisic acid (ABA) treatments had no influence on TaHSC70 expression. These results suggest that TaHSC70 plays a role in stress-related responses, and in defense responses elicited by infection with stripe rust fungus and does so via a JA-dependent signal transduction pathway
Superconductivity at 11.3 K induced by cobalt doping in CeOFeAs
Pure phases of a new oxyarsenide superconductor of the nominal composition
CeOFe0.9Co0.1As was successfully synthesized by solid state reaction in sealed
silica ampoules at 1180 C. It crystallizes in the layered tetragonal ZrCuSiAs
type structure (sp gp P4/nmm) with lattice parameter of a = 3.9918(5) angstrom
and c = 8.603(1) angstrom. A sharp superconducting transition is observed at
11.31 K with an upper critical field of 45.22 T at ambient pressure. The
superconducting transition temperature is drastically lowered (~ 4.5, 4.9 K) on
increasing the concentration (x = 0.15, 0.2) of cobalt
Using enzyme activities as an indicator of soil fertility in grassland - an academic dilemma.
Grasslands play an important role in conserving natural biodiversity and providing ecosystem functions and services for societies. Soil fertility is an important property in grassland, and the monitoring of soil fertility can provide crucial information to optimize ecosystem productivity and sustainability. Testing various soil physiochemical properties related to fertility usually relies on traditional measures, such as destructive sampling, pre-test treatments, labor-intensive procedures, and costly laboratory measurements, which are often difficult to perform. However, soil enzyme activity reflecting the intensity of soil biochemical reactions is a reliable indicator of soil properties and thus enzyme assays could be an efficient alternative to evaluate soil fertility. Here, we review the latest research on the features and functions of enzymes catalyzing the biochemical processes that convert organic materials to available plant nutrients, increase soil carbon and nutrient cycling, and enhance microbial activities to improve soil fertility. We focus on the complex relationships among soil enzyme activities and functions, microbial biomass, physiochemical properties, and soil/crop management practices. We highlight the biochemistry of enzymes and the rationale for using enzyme activities to indicate soil fertility. Finally, we discuss the limits and disadvantages of the potential new molecular tool and provide suggestions to improve the reliability and feasibility of the proposed alternative
Superplastic behaviour of AZ91 magnesium alloy processed by highâ pressure torsion
An investigation has been conducted on the tensile properties of a fineâgrained AZ91 magnesium alloy processed at room temperature by high pressure torsion (HPT). Tensile testing was carried out at 423 K, 473 K and 573 K using strain rates from 1Ă10â1 sâ1 to 1Ă10â4 sâ1 for samples processed in HPT for N = 1, 3, 5 and 10 turns. After testing was completed, the microstructures were investigated by scanning electron microscopy and energy dispersive spectroscopy. The alloy processed at room temperature in HPT exhibited excellent superplastic behaviour with elongations higher than elongations reported previously for fineâgrained AZ91 alloy produced by other severe plastic deformation processes, e.g. HPT, ECAP and EXâECAP. A maximum elongation of 1308 % was achieved at a testing temperature of 573 K using a strain rate of 1Ă10â4 sâ1, which is the highest value of elongation reported to date in this alloy. Excellent highâstrain rate superplasticity (HSRSP) was achieved with maximum elongations of 590 % and 860 % at temperatures of 473 K and 573 K, respectively, using a strain rate of 1Ă10â2 sâ1. The alloy exhibited lowâtemperature superplasticity (LTSP) with maximum elongations of 660 % and 760 % at a temperature of 423 K and using strain rates of 1Ă10â3 sâ1 and 1Ă10â4 sâ1, respectively. Grainâboundary sliding (GBS) was identified as the deformation mechanism during HSRSP, and the glideâdislocation creep accommodated by GBS dominated during LTSP. Grainâboundary sliding accommodated with diffusion creep was the deformation mechanism at high test temperature and slow strain rates. An enhanced thermal stability of the microstructure consisting of fine equiaxed grains during deformation at elevated temperature was attributed to the extremely fine grains produced in HPT at room temperature, a high volume fraction of nano ?âparticles, and the formation of ?âphase filaments
Scaling Behavior of Anomalous Hall Effect and Longitudinal Nonlinear Response in High-Tc Superconductors
Based on existing theoretical model and by considering our longitudinal
nonlinear response function, we derive a nonliear equation in which the mixed
state Hall resistivity can be expressed as an analytical function of magnetic
field, temperature and applied current. This equation enables one to compare
quantitatively the experimental data with theoretical model. We also find some
new scaling relations of the temperature and field dependency of Hall
resistivity. The comparison between our theoretical curves and experimental
data shows a fair agreement.Comment: 4 pages, 3 figure
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