Method of fabricating an object with a thin wall having a precisely shaped slit

A method is described for making a structure with a cavity and a thin wall with a precisely shaped slit. An object with a cavity having two openings, one of which is to be closed by a thin wall with a slit, is placed on the surface of a fixture. The fixture surface has a slot conforming to the size and shape of the slit to be formed in the thin wall

Spin of ground state baryons

We calculate the quark spin contribution to the total angular momentum of flavor octet and flavor decuplet ground state baryons using a spin-flavor symmetry based parametrization method of quantum chromodynamics. We find that third order SU(6) symmetry breaking three-quark operators are necessary to explain the experimental result Sigma_1=0.32(10). For spin 3/2 decuplet baryons we predict that the quark spin contribution is Sigma_3=3.93(22), i.e. considerably larger than their total angular momentum.Comment: 8 page

Charge-Symmetry-Breaking Three-Nucleon Forces

Leading-order three-nucleon forces that violate isospin symmetry are calculated in Chiral Perturbation Theory. The effect of the charge-symmetry-breaking three-nucleon force is investigated in the trinucleon systems using Faddeev calculations. We find that the contribution of this force to the 3He - 3H binding-energy difference is approximately 5 keV.Comment: 14 pages, 3 figure

Isospin symmetry breaking in an algebraic pairing Sp(4) model

An exactly solvable sp(4) algebraic approach extends beyond the traditional isospin conserving nuclear interaction to bring forward effects of isospin symmetry breaking and isospin mixing resulting from a two-body nuclear interaction that includes proton-neutron (pn) and like-particle isovector pairing correlations plus significant isoscalar pn interactions. The model yields an estimate for the extent to which isobaric analog 0+ states in light and medium mass nuclei may mix with one another and reveals possible, but still extremely weak, non-analog beta-decay transitions.Comment: 8 pages, 2 figure

Sound velocity and absorption measurements under high pressure using picosecond ultrasonics in diamond anvil cell. Application to the stability study of AlPdMn

We report an innovative high pressure method combining the diamond anvil cell device with the technique of picosecond ultrasonics. Such an approach allows to accurately measure sound velocity and attenuation of solids and liquids under pressure of tens of GPa, overcoming all the drawbacks of traditional techniques. The power of this new experimental technique is demonstrated in studies of lattice dynamics, stability domain and relaxation process in a metallic sample, a perfect single-grain AlPdMn quasicrystal, and rare gas, neon and argon. Application to the study of defect-induced lattice stability in AlPdMn up to 30 GPa is proposed. The present work has potential for application in areas ranging from fundamental problems in physics of solid and liquid state, which in turn could be beneficial for various other scientific fields as Earth and planetary science or material research

Vector, Axial, Tensor and Pseudoscalar Vacuum Susceptibilities

Using a recently developed three-point formalism within the method of QCD Sum Rules we determine the vacuum susceptibilities needed in the two-point formalism for the coupling of axial, vector, tensor and pseudoscalar currents to hadrons. All susceptibilities are determined by the space-time scale of condensates, which is estimated from data for deep inelastic scattering on nucleons

Informed consent - a survey of doctors' practices in South Africa

Objective. To examine doctors' practices with regard to informed consent.Design. Cross-sectional, descriptive survey.Participants 'and setting. All full-time consultants and registrars in the Departments of Medicine, Obstetrics and Gynaecology, Paediatrics and Child Health, Paediatric Surgery and Surgery at the University of Cape Town were included. The overall response rate was 63% (160/254).Measurement. Data were collected by means of selfadministered, semi-structured questionnaires.Results. Most doctors (79%) felt it was their responsibility to ensure that patients and parents were fully informed about diagnostic and therapeutic interventions. Many (62%) supported a patient-centred standard for determining the type and amount of information to disclose. Doctors disclose most of the legally required information except for information about alternative forms of treatment and remote serious risks. They almost never provide information on medical costs. The most common reasons for not obtaining informed consent were the doctors' tendency to 'tell' patients! parents what they intend doing and their belief that patients/parents expect doctors to know what is medicallybest for them. Language, inadequate communication skills and lack of time were, surprisingly, seldom viewed as obstacles to the obtaining of informed consent. Findings were independent of discipline (medical or surgical) and doctors' status (consultant or registrar). Doctors who treat children were significantly less likely to obtain consent forcertain interventions.Conclusion. Doctors meet many, but not all, of the legal requirements for informed consent. The findings question whether informed consent as envisioned by the law existsin reality. Cross-cultural research is needed to clarify patients' and parents' expectations of informed consent

Correlation density matrices for 1- dimensional quantum chains based on the density matrix renormalization group

A useful concept for finding numerically the dominant correlations of a given ground state in an interacting quantum lattice system in an unbiased way is the correlation density matrix. For two disjoint, separated clusters, it is defined to be the density matrix of their union minus the direct product of their individual density matrices and contains all correlations between the two clusters. We show how to extract from the correlation density matrix a general overview of the correlations as well as detailed information on the operators carrying long-range correlations and the spatial dependence of their correlation functions. To determine the correlation density matrix, we calculate the ground state for a class of spinless extended Hubbard models using the density matrix renormalization group. This numerical method is based on matrix product states for which the correlation density matrix can be obtained straightforwardly. In an appendix, we give a detailed tutorial introduction to our variational matrix product state approach for ground state calculations for 1- dimensional quantum chain models. We show in detail how matrix product states overcome the problem of large Hilbert space dimensions in these models and describe all techniques which are needed for handling them in practice.Comment: 50 pages, 34 figures, to be published in New Journal of Physic

Isospin Breaking in the Pion-Nucleon Coupling from QCD Sum Rules

We use QCD sum rules for the three point function of a pseudoscalar and two nucleonic currents in order to estimate the charge dependence of the pion nucleon coupling constant $g_{NN\pi}$ coming from isospin violation in the strong interaction. The effect can be attributed primarily to the difference of the quark condensates $$and$$. For the splitting $(g_{pp\pi_0} - g_{nn\pi_0}) / g_{NN\pi}$ we obtain an interval of $1.2 * 10^{-2}$ to $3.7 * 10^{-2}$, the uncertainties coming mainly from the input parameters. The charged pion nucleon coupling is found to be the average of $g_{pp\pi_0}$ and $g_{nn\pi_0}$. Electromagnetic effects are not included.Comment: 18 pages (REVTeX) + 2 figures (as PostScript), to be published in PRC, replaced with final version: inclusion of pi-eta mixing and N -> N* transition

Energy level statistics of electrons in a 2D quasicrystal

A numerical study is made of the spectra of a tight-binding hamiltonian on square approximants of the quasiperiodic octagonal tiling. Tilings may be pure or random, with different degrees of phason disorder considered. The level statistics for the randomized tilings follow the predictions of random matrix theory, while for the perfect tilings a new type of level statistics is found. In this case, the first-, second- level spacing distributions are well described by lognormal laws with power law tails for large spacing. In addition, level spacing properties being related to properties of the density of states, the latter quantity is studied and the multifractal character of the spectral measure is exhibited.Comment: 9 pages including references and figure captions, 6 figures available upon request, LATEX, report-number els