1,865 research outputs found
The off-Shell Electromagnetic Vertex of the Nucleon in Chiral Perturbation Theory
We study the electromagnetic vertex of a nucleon in next-to-leading order
chiral perturbation theory (CPT). We consider the case where one of the
nucleons at the NN vertex is off its mass shell. We define relevant
measures for the off-shell dependence in the limited kinematical range allowed,
and analyze their expansion in the pion mass. The leading nonanalytic
contributions are calculated to estimate their size.Comment: 12 pages (LaTeX), 1 figure (available upon request), NIKHEF 93-P
Observation of a linear temperature dependence of the critical current density in a Ba_{0.63}K_{0.37}BiO_3 single crystal
For a Ba_{0.63}K_{0.37}BiO_3 single crystal with T_c=31 K, H_{c1}=750 Oe at 5
K, and dimensions 3x3x1 mm^3, the temperature and field dependences of magnetic
hysteresis loops have been measured within 5-25 K in magnetic fields up to 6
Tesla. The critical current density is J_c(0)=1.5 x 10^5 A/cm^2 at zero field
and 1 x 10^5 A/cm^2 at 1 kOe at 5 K. J_c decreases exponentially with
increasing field up to 10 kOe. A linear temperature dependence of J_c is
observed below 25 K, which differs from the exponential and the power-law
temperature dependences in high-Tc superconductors including the BKBO. The
linear temperature dependence can be regarded as an intrinsic effect in
superconductors.Comment: RevTex, Physica C Vol. 341-348, 729 (2000
Stability of 1+1 dimensional causal relativistic viscous hydrodynamics
The stability of the 1+1 dimensional solution of Israel-Stewart theory is
investigated. Firstly, the evolution of the temperature and the ratio of the
bulk pressure over the equilibrium pressure of the background is explored. Then
the stability with linear perturbations is studied by using the Lyapunov direct
method. It shows that the shear viscosity may weaken the instability induced by
the large peak of bulk viscosity around the phase transition temperature .Comment: 18 pages, 4 figures, 1 table; to be published in Nuclear Physics
The Analysis of SKP1 Gene Expression in Physiological Male Sterility Induced by Chemical Hybridizing Agent SQ-1 in Wheat (Triticum aestivum L.)
Physiological male sterility induced by the chemical hybridizing agent (CHA) overcomes problems of maintenance of sterile lines and restorers. However, the mechanism of sterility is unclear. The process of tapetum of CHA-treated ‘Xi’nong 2611’ at uninucleate, binucleate and trinucleate were compared with control to determine if tapetum varying differently during developmental stages. Tapetal degradation in CHA-treated ‘Xi’nong 2611’ began at late uninucleate stage, somewhat earlier than control plants. Cytological observations indicated that the gradual degradation of the tapetum in CHA-treated ‘Xi’nong 2611’ was initiated and terminated earlier than in the control. These findings implied that CHA-induced male sterility was related to abnormally early tapetal degradation. In order to indicate the role of the SKP1 gene in fertility/sterility in wheat, its expression was assessed in anthers at uninucleate, binucleate and trinucleate stages. SKP1 expression was reduced in the later developmental stages, and there was an obvious decrease from the uninucleate to trinucleate stages. Higher expression of the SKP1 gene occurred in ‘Xi’nong 2611’ compared to CHA-treated ‘Xi’nong 2611’. This implied that SKP1 gene expression was inhibited during the fertility transformation process and was related to transformation from fertility to sterility. Moreover, the results from this study suggest that SKP1 plays an essential role of conducting fertility in physiological male sterility
Equation of state and magnetic susceptibility of spin polarized isospin asymmetric nuclear matter
Properties of spin polarized isospin asymmetric nuclear matter are studied
within the framework of the Brueckner--Hartree--Fock formalism. The
single-particle potentials of neutrons and protons with spin up and down are
determined for several values of the neutron and proton spin polarizations and
the asymmetry parameter. It is found an almost linear and symmetric variation
of the single-particle potentials as increasing these parameters. An analytic
parametrization of the total energy per particle as a function of the asymmetry
and spin polarizations is constructed. This parametrization is employed to
compute the magnetic susceptibility of nuclear matter for several values of the
asymmetry from neutron to symmetric matter. The results show no indication of a
ferromagnetic transition at any density for any asymmetry of nuclear matter.Comment: 23 pages, 8 figures, 2 tables (submitted to Phys. Rev. C
A randomised, double-blind, phase 3 study comparing the efficacy and safety of ceftazidime/avibactam plus metronidazole versus meropenem for complicated intra-abdominal infections in hospitalised adults in Asia
Ceftazidime/avibactam comprises the broad-spectrum cephalosporin ceftazidime and the non-β-lactam β-lactamase inhibitor avibactam. This phase 3, randomised, double-blind study (NCT01726023) assessed the efficacy and safety of ceftazidime/avibactam plus metronidazole compared with meropenem in patients with complicated intra-abdominal infection (cIAI) in Asian countries. Subjects aged 18–90 years and hospitalised with cIAI requiring surgical intervention were randomised 1:1 to receive every 8 h either: ceftazidime/avibactam (2000/500 mg, 2-h infusion) followed by metronidazole (500 mg, 60-min infusion); or meropenem (1000 mg, 30-min infusion). Non-inferiority of ceftazidime/avibactam plus metronidazole to meropenem was concluded if the lower limit of the 95% confidence interval (CI) for the between-group difference in clinical cure rate was greater than −12.5% at the test-of-cure (TOC) visit (28–35 days after randomisation) in the clinically evaluable (CE) population. Safety was also evaluated. Of 441 subjects randomised, 432 received at least one dose of study medication (ceftazidime/avibactam plus metronidazole, n = 215; meropenem, n = 217). In the CE population at the TOC visit, non-inferiority of ceftazidime/avibactam plus metronidazole to meropenem was demonstrated, with clinical cure reported for 93.8% (166/177) and 94.0% (173/184) of subjects, respectively (between-group difference, −0.2, 95% CI −5.53 to 4.97). The clinical cure rate with ceftazidime/avibactam plus metronidazole was comparable in subjects with ceftazidime-non-susceptible and ceftazidime-susceptible isolates (95.7% vs. 92.1%, respectively). Adverse events were similar between the study groups. Ceftazidime/avibactam plus metronidazole was non-inferior to meropenem in the treatment of cIAIs in Asian populations and was effective against ceftazidime-non-susceptible pathogens. No new safety concerns were identified
Chiral restoration effects on the shear viscosity of a pion gas
We investigate the shear viscosity of a pion gas in relativistic kinetic
theory, using the Nambu-Jona-Lasinio model to construct the pion mass and the
pi-pi interaction at finite temperature. Whereas at low temperatures the
scattering properties and, hence, the viscosity are in agreement with
lowest-order chiral perturbation theory, we find strong medium modifications in
the crossover region. Here the system is strongly coupled and the scattering
lengths diverge, similarly as for ultra-cold Fermi gases at a Feshbach
resonance. As a consequence, the ratio eta/s is found to be strongly reduced as
compared to calculations without medium-modified masses and scattering
amplitudes. However, the quantitative results are very sensitive to the details
of the applied approximations.Comment: 15 pages, 12 figures; v2: extended discussions of the dressed sigma
propagator and the low-temperature limit, typos corrected, accepted versio
Reunion of random walkers with a long range interaction: applications to polymers and quantum mechanics
We use renormalization group to calculate the reunion and survival exponents
of a set of random walkers interacting with a long range and a short
range interaction. These exponents are used to study the binding-unbinding
transition of polymers and the behavior of several quantum problems.Comment: Revtex 3.1, 9 pages (two-column format), 3 figures. Published version
(PRE 63, 051103 (2001)). Reference corrections incorporated (PRE 64, 059902
(2001) (E
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