Search results for "Exam"
showing 10 items of 1241 documents
COMPUTER SIMULATION OF PROFILES OF INTERFACES BETWEEN COEXISTING PHASES: DO WE UNDERSTAND THEIR FINITE SIZE EFFECTS?
2000
Interfaces between coexisting phases are very common in condensed matter physics, and thus many simulations attempt to characterize their properties, in particular, the interfacial tension and the interfacial profile. However, while theory usually deals with the "intrinsic profile", the latter is not a straightforward output of a simulation: The actual profile (observed in simulations and/or experiments!) is broadened by lateral fluctuations. Therefore, in the usual simulation geometry of L × L × L (in three dimensions), where one chooses suitable boundary conditions to stabilize one or two interfaces of (minimal) area L × L, the profile (and in particular the interfacial width) depends on…
Spin-coupling topology in the copper hexamer compounds A2Cu3O(SO4)3 (A=Na, K)
2020
The compounds ${A}_{2}\mathrm{C}{\mathrm{u}}_{3}\mathrm{O}{(\mathrm{S}{\mathrm{O}}_{4})}_{3}$ $(A=\mathrm{Na},\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ are characterized by copper hexamers that are weakly coupled to realize antiferromagnetic order below ${T}_{N}\ensuremath{\approx}3\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. They constitute quantum spin systems with $S=1$ triplet ground states. We investigated the energy-level splittings of the copper hexamers by inelastic neutron scattering experiments covering the entire range of the magnetic excitation spectra. The observed transitions are governed by very unusual selection rules that we ascribe to the underlying spin-coupling topology. This…
A holographic approach to low-energy weak interactions of hadrons
2011
We apply the double-trace formalism to incorporate nonleptonic weak interactions of hadrons into holographic models of the strong interactions. We focus our attention upon $\Delta S=1$ nonleptonic kaon decays. By working with a Yang-Mills--Chern-Simons 5-dimensional action, we explicitly show how, at low energies, one recovers the $\Delta S=1$ weak chiral Lagrangian for both the anomalous and nonanomalous sectors. We provide definite predictions for the low energy coefficients in terms of the AdS metric and argue that the double-trace formalism is a 5-dimensional avatar of the Weak Deformation Model introduced long ago by Ecker et al. As a significant phenomenological application, we reasse…
β− Strength function phenomena of exotic nuclei: A critical examination of the significance of nuclear model predictions
1984
Abstract Reliable predictions of β-decay properties of nuclei far from stability require knowledge of the β-strength distribution, S β ( E ). By comparison of experimental strength functions of neutron-rich Rb isotopes in the transitional region around A = 100 with S β ( E ) from different nuclear models, the sensitivity and physical significance of S β ( E ) on various integral and spectral β-decay properties are examined. The reliability of extrapolations and the applicability to different fields in nuclear physics, astrophysics and reactor technology are discussed. It is shown that, although there has been considerable progress in the physical understanding of the decay properties of nuc…
Supersymmetry does not imply mass degeneracy
2004
Abstract It is commonly believed that unbroken supersymmetry (SUSY) implies that all members of a supermultiplet have the same mass. We demonstrate that this is not true, by exhibiting a simple counterexample. We employ the formalism of homeotic fermions, in a simple model where CPT conjugate fermions have different masses. This model can be supersymmetrized to a hypermultiplet of fields which form a representation of the conventional N=2 SUSY algebra. Nevertheless, CPT conjugate states in this hypermultiplet have different masses. These surprising results do not violate either the CPT theorem or the Haag–Lopuszanski–Sohnius theorem.
Solution of the Lindblad equation in Kraus representation
2006
The so-called Lindblad equation, a typical master equation describing the dissipative quantum dynamics, is shown to be solvable for finite-level systems in a compact form without resort to writing it down as a set of equations among matrix elements. The solution is then naturally given in an operator form, known as the Kraus representation. Following a few simple examples, the general applicability of the method is clarified.
Description and evolution of anisotropy in superfluid vortex tangles with counterflow and rotation
2006
We examine several vectorial and tensorial descriptions of the geometry of turbulent vortex tangles. We study the anisotropy in rotating counterflow experiments, in which the geometry of the tangle is especially interesting because of the opposite effects of rotation, which orients the vortices, and counterflow, which randomizes them. We propose to describe the anisotropy and the polarization of the vortex tangle through a tensor, which contains the first and second moments of the distribution of the unit vector ${\mathbf{s}}^{\ensuremath{'}}$ locally tangent to the vortex lines. We use an analogy with paramagnetism to estimate the anisotropy, the average polarization, the polarization fluc…
Evidence for extrinsic control of oesophageal primary peristalsis.
1985
AbstractThe role of both peripheral and central mechanism in the control of primary peristalsis was studied in pigeon cervical oesophagus.The results from the transection of oesophageal muscular wall and of extrinsic nerves suggest that :i) primary peristalsis is programmed centrally.ii) extrinsic motor input is carried in glossopharyngeal nerves and distributed separately at each oesophageal level through intramural neurons.iii) intramural neurons do not seem capable of propagating the peristaltic sequence irrespective of the central control.
Carga y factores de riesgo para la neumonía adquirida en la comunidad de Pseudomonas aeruginosa : un estudio multinacional de prevalencia puntual de …
2018
Pseudomonas aeruginosa is a challenging bacterium to treat due to its intrinsic resistance to the antibiotics used most frequently in patients with community-acquired pneumonia (CAP). Data about the global burden and risk factors associated with P. aeruginosa-CAP are limited. We assessed the multinational burden and specific risk factors associated with P. aeruginosa-CAP. We enrolled 3193 patients in 54 countries with confirmed diagnosis of CAP who underwent microbiological testing at admission. Prevalence was calculated according to the identification of P. aeruginosa. Logistic regression analysis was used to identify risk factors for antibiotic-susceptible and antibiotic-resistant P. aeru…
Polygraph examination in anaysis of evidence
2014
"I assume that a polygraph examination may be part of mass of evidence in a specific case, and I also assume that the result of a polygraph examination belongs to forensic evidence, and within it has its place in expert evidence. Therefore, as item of evidence, it can be subjected to an analysis covering the assessment of its credibility, reliability, weigh, probative force, etc., and can also be analysed as evidential argument. Such an argument may be evaluated from two points of view: “internal” developed by its creator (in this case: by the expert), and “external” whose author is the analyst, or, more generally speaking, the addressee of the argument. Th e “internal” analysis is presente…