1,061 research outputs found
Curvature Correction in the Strutinsky's Method
Mass calculations carried out by Strutinsky's shell correction method are
based on the notion of smooth single particle level density. The smoothing
procedure is always performed using curvature correction. In the presence of
curvature correction a smooth function remains unchanged if smoothing is
applied. Two new curvature correction methods are introduced. The performance
of the standard and new methods are investigated using harmonic oscillator and
realistic potentials.Comment: 4 figures, submitted to Journal of Physics G: Nuclear and Particle
Physic
Postan - A Package for Postoptimal Analysis (An Extension of Minos)
This paper presents a new software package which has been developed in collaboration with IIASA The new package, POSTAN, is designed for postoptimal analysis of linear programming problems, and is embedded in the well-known linear and nonlinear programming code MINOS. POSTAN is composed of a number of FORTRAN subroutines which may be called by adding some new keywords to the original list of MINOS specifications. The main function of POSTAN is to determine the ranges in which certain parameters may be changed without affecting the optimal solution and/or the optimal basis.
In this paper the authors outline the general form of the linear programming problems studied, describe the six new subroutines in some detail, and illustrate this description with a printout obtained in the solution of a sample problem. The mathematical theory behind the software package is given in an Appendix
Postan 3 - Extended Postoptimal Analysis Package for Minos
This paper is one of the series of 11 Working Papers presenting the software for interactive decision support and software tools for developing decision support systems. These products constitute the outcome of the contracted study agreement between the System and Decision Sciences Program at IIASA and several Polish scientific institutions. The theoretical part of these results is presented in the IIASA Working Paper WP-88-071 entitled "Theory, Software and Testing Examples in Decision Support Systems" which contains the theoretical and methodological backgrounds of the software systems developed within the project.
This paper presents the POSTAN 3 package. This package constitutes the tool for postoptimal analysis for linear and linear-fractional programming problems. POSTAN consists of a number of FORTRAN routines which are incorporated into MINOS, the well known linear and nonlinear programming code developed at the Stanford University. The postoptimal analysis is performed after MINOS has found an optimal solution and is initiated by extending the original MINOS specification file. The main function of POSTAN is ranging with respect to parameters specified by the user and computing the sensitivity coefficients
Fission barriers in actinides in covariant density functional theory: the role of triaxiality
Relativistic mean field theory allowing for triaxial deformations is applied
for a systematic study of fission barriers in the actinide region. Different
pairing schemes are studied in details and it is shown that covariant density
functional theory is able to describe fission barriers on a level of accuracy
comparable with non-relativistic calculations, even with the best
phenomenological macroscopic+microscopic approaches. Triaxiality in the region
of the first saddle plays a crucial role in achieving that.Comment: 11 pages, 13 figure
Quantum graphs with singular two-particle interactions
We construct quantum models of two particles on a compact metric graph with
singular two-particle interactions. The Hamiltonians are self-adjoint
realisations of Laplacians acting on functions defined on pairs of edges in
such a way that the interaction is provided by boundary conditions. In order to
find such Hamiltonians closed and semi-bounded quadratic forms are constructed,
from which the associated self-adjoint operators are extracted. We provide a
general characterisation of such operators and, furthermore, produce certain
classes of examples. We then consider identical particles and project to the
bosonic and fermionic subspaces. Finally, we show that the operators possess
purely discrete spectra and that the eigenvalues are distributed following an
appropriate Weyl asymptotic law
The magnetic interactions in spin-glasslike Ge/1-x-y/Sn/x/Mn/y/Te diluted magnetic semiconductor
We investigated the nature of the magnetic phase transition in the
Ge/1-x-y/Sn/x/Mn/y/Te mixed crystals with chemical composition changing in the
range of 0.083 < x < 0.142 and 0.012 < y < 0.119. The DC magnetization
measurements performed in the magnetic field up to 90 kOe and temperature range
2-200 K showed that the magnetic ordering at temperatures below T = 50 K
exhibits features characteristic for both spin-glass and ferromagnetic phases.
The modified Sherrington - Southern model was applied to explain the observed
transition temperatures. The calculations showed that the spin-glass state is
preferred in the range of the experimental carrier concentrations and Mn
content. The value of the Mn hole exchange integral was estimated to be J/pd/ =
0.45+/-0.05 eV. The experimental magnetization vs temperature curves were
reproduced satisfactory using the non-interacting spin-wave theory with the
exchange constant J/pd/ values consistent with those calculated using modified
Sherrington - Southern model. The magnetization vs magnetic field curves showed
nonsaturating behavior at magnetic fields B < 90 kOe indicating the presence of
strong magnetic frustration in the system. The experimental results were
reproduced theoretically with good accuracy using the molecular field
approximation-based model of a disordered ferromagnet with long-range RKKY
interaction.Comment: 9 pages, 6 figure
Renal Heme Oxygenase-1 Induction with Hemin Augments Renal Hemodynamics, Renal Autoregulation, and Excretory Function
Heme oxygenases (HO-1; HO-2) catalyze conversion of heme to free iron, carbon monoxide, and biliverdin/bilirubin. To determine the effects of renal HO-1 induction on blood pressure and renal function, normal control rats (n=7) and hemin-treated rats (n=6) were studied. Renal clearance studies were performed on anesthetized rats to assess renal function; renal blood flow (RBF) was measured using a transonic flow probe placed around the left renal artery. Hemin treatment significantly induced renal HO-1. Mean arterial pressure and heart rate were not different (115±5 mmHg versus 112±4 mmHg and 331±16 versus 346±10 bpm). However, RBF was significantly higher (9.1±0.8 versus 7.0±0.5 mL/min/g, P<0.05), and renal vascular resistance was significantly lower (13.0±0.9 versus 16.6±1.4 [mmHg/(mL/min/g)], P<0.05). Likewise, glomerular filtration rate was significantly elevated (1.4±0.2 versus 1.0±0.1 mL/min/g, P<0.05), and urine flow and sodium excretion were also higher (18.9±3.9 versus 8.2±1.0 μL/min/g, P<0.05 and 1.9±0.6 versus 0.2±0.1 μmol/min/g, P<0.05, resp.). The plateau of the autoregulation relationship was elevated, and renal vascular responses to acute angiotensin II infusion were attenuated in hemin-treated rats reflecting the vasodilatory effect of HO-1 induction. We conclude that renal HO-1 induction augments renal function which may contribute to the antihypertensive effects of HO-1 induction observed in hypertension models
RESONANT TUNNELLING IN DOUBLE-BARRIER HETEROSTRUCTURES WITH AN ACCUMULATION LAYER
Two modes of electron gas injection in resonant tunnelling through GaAs/AlGaAs double-barrier heterostructures were revealed while studying their current-voltage characteristics. Examining peculiarities of the characteristics within the temperature range 4-350 K and under a high magnetic field, we were able to distinguish the contribution to resonant tunnelling of ballistic electrons mjected from a three-dimensional electron gas in the emitter contact and that of electrons injected from a two-dimensional electron gas in the accumulation layer formed near the emitter barrier.
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