Search results for "Formalism"

The kinetics of defect aggregation: A novel lattice formalism

1995

We introduce a stochastic model for the A + B → O reaction on a discrete lattice. The system may include mono- and bimolecular steps (i. e. reaction and diffusion steps). The resulting infinite chain of equations is truncated at a certain level via a modified Kirkwood approximation.

Measurement ofχcjdecaying intopn¯π−andpn¯π−π0

2014

Using (106.41 +/- 0.86) x 10(6) Psi(3686) events collected with the BESIII detector at BEPCII, we study for the first time the decay chi(cJ) -> eta'K+K- (J = 1, 2), where eta' -> gamma rho(0) and eta' -> eta pi(+)pi(-). A partial wave analysis in the covariant tensor amplitude formalism is performed for the decay chi(c1) -> eta'K+K-. Intermediate processes chi(c1) -> eta'f(2)'(1525) chi(c1) -> K-0*(1430)K-+/-(-/+) (K-0*(1430)(+/-) -> eta'K-+/-) are observed with statistical significances larger than 5 sigma, and their branching fractions are measured.

Non-mesonic weak decay of A hypernuclei

1998

Abstract The non-mesonic decay modes of Λ hypernuclei are examined. The one-nucleon induced decay (ΛN → NN) is studied in a shell-model framework using a meson-exchange picture. The total decay rates and parity-violating asymmetries reproduce the available experimental data. However, the model does not yet explain the partial rates and the resulting neutron- to proton-induced ratio Γ n /Γ p . The two-nucleon-induced decay rate (ΛNN -> NNN) is evaluated using the propagator formalism and the local-density approximation and is found to contribute about 15% to the total decay width of medium to heavy hypernuclei. The influence of this channel on the experimental determination of the ratio Γ n …

Nuclear-structure input to r-process calculations

1998

Abstract By comparing results from r-process parameter studies within the classical waiting-point approximation with the observed solar-system r-abundance distribution N r ,⊙ , in-formation on nuclear-structure phenomena on neutron-rich isotopes far off the stability line can be obtained. Such information is — to a large extent — experimentally not accessible. Investigations in the early 1990's, making use of QRPA β-decay properties and nuclear masses from the macroscopic-microscopic FRDM and ETFSI-1 models, showed r-abundance deficiencies around A ⋍115 and 180 , indicating overly strong N=82 and 126 shell strengths far from stability. Recent experiments in the A ⋍110–130 region as well as …

Sideward flow in Au + Au collisions at 400 A.MeV

1995

Abstract We present new experimental data obtained with the FOPI detector at SIS, for the Au + Au heavy-ion collisions at 400 A MeV incident energy. The sideward flow, determined from a method without reaction-plane reconstruction, and the nuclear stopping are studied as a function of the centrality of the collisions. In order to study the nuclear in-medium effects, which act on the NN cross sections and potential and hence on experimental observables like the nuclear-matter flow and stopping, these results are compared with the predictions of two different QMD versions. The first one offers a fully microscopic calculation of the cross sections and potential in the G-matrix formalism and na…

A Generic High-Dose-Rate 192Ir Source Model for Model-Based Dose Calculation Methods in Brachytherapy Beyond the TG-43 Formalism

2013

Statistical analysis when dealing with astigmatism: assessment of different spherocylindrical notations.

2001

Ophthalmic epidemiological studies frequently deal with ocular refractive errors, which are commonly expressed in the form sphere/cylinder x axis. However, this representation has been shown not to be the most suitable one for performing statistical analysis. Although alternative analytical and graphic methods to represent this kind of data have been developed, these formalisms have often gone unnoticed by researchers, despite their usefulness and versatility. Besides, there has been no discussion of how each of them fits in with a particular type of study. In this paper, several mathematical representations of dioptric power are revisited in a comprehensive way. The aim is to encourage res…

Subjective Refraction Techniques in the Frame of the Three-Dimensional Dioptric Space

2001

A novel heuristic approach to the well-known representation of the dioptric power in a three-dimensional space is presented. It is shown how this theoretical framework is ideal for discussing the principles of several subjective refraction methods. In particular, this formalism is used to justify the stenopaic slit refraction, the Barnes subjective refraction technique, and the Jackson cross-cylinder procedure. In view of this analysis, some modifications to the traditional procedures are proposed.

Lateral magnification matrix from the dioptric power matrix formalism in the paraxial case.

2012

Background Previous studies have highlighted that power matrices fully characterize the concept of dioptric power of any astigmatic surface. Thus, the basic equations in physiological optics can be generalized using the matrix formalism of the dioptric power. Among others, lateral magnification has also been interpreted as a matrix but mainly concerning magnification modification induced by spectacle correction of refractive error. Purpose To provide a fresh look into a novel paraxial formulation for the assessment of the lateral magnification using power matrices and in presence of astigmatism for thin and thick imaging systems in general. Methods Linear optics provides the frame to genera…

The bi-Hamiltonian theory of the Harry Dym equation

2002

We describe how the Harry Dym equation fits into the the bi-Hamiltonian formalism for the Korteweg-de Vries equation and other soliton equations. This is achieved using a certain Poisson pencil constructed from two compatible Poisson structures. We obtain an analogue of the Kadomtsev-Petviashivili hierarchy whose reduction leads to the Harry Dym hierarchy. We call such a system the HD-KP hierarchy. We then construct an infinite system of ordinary differential equations (in infinitely many variables) that is equivalent to the HD-KP hierarchy. Its role is analogous to the role of the Central System in the Kadomtsev-Petviashivili hierarchy.