The ring imaging Cherenkov detector for the BRAHMS experiment at RHIC

A ring imaging Cherenkov counter, to be read out by four 100-channel PMTs, is a key element of the BRAHMS experiment. We report here the most recent results obtained tested at the BNL AGS using several radiator gases, including the heavy fluorocarbon C4F10. Ring radii were measured for different particles (pions, muons, and electrons) for momenta ranging from 2 to 12 GeV/c employing pure C4F10 as radiator.Comment: 3 pages 3 figure

Magnetic force microscopy of single crystal magnetite (Fe3O4)(abstract)

The micromagnetic domain structure of a magnetite (Fe3O4) single crystal has been studied using a magnetic force microscope (MFM). The MFM responds to the perpendicular component of the stray field above the magnetite surface. The sample was polished in the (011) plane. In this case, there are two easy magnetic axes parallel to the surface. Surface domains observed near cracks and edges have a complex closure structure (see Fig. 1), while walls seen far from such boundaries have a sinusoidal structure. Of particular interest is the presence of walls with either even or odd symmetry of the perpendicular stray field component across the transition. These can be conventionally modeled as Bloch or Neel walls, respectively. Both types of walls have been modeled and compared with the experimentally observed structures. We find the Bloch domain walls to be about 300 nm wide, nearly twice the value expected from bulk wall calculations. This distinction is consistent with a surface broadening of the domain wall due to magnetostatic effects.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70207/2/JAPIAU-75-10-6892-1.pd

Estimating the Empirical Lorenz Curve and Gini Coefficient in the Presence of Error

The Lorenz curve is a graphical tool that is widely used to characterize the concentration of a measure in a population, such as wealth. It is frequently the case that the measure of interest used to rank experimental units when estimating the empirical Lorenz curve, and the corresponding Gini coefficient, is subject to random error. This error can result in an incorrect ranking of experimental units which inevitably leads to a curve that exaggerates the degree of concentration (variation) in the population. We explore this bias and discuss several widely available statistical methods that have the potential to reduce or remove the bias in the empirical Lorenz curve. The properties of these methods are examined and compared in a simulation study. This work is motivated by a health outcomes application which seeks to assess the concentration of black patient visits among primary care physicians. The methods are illustrated on data from this study

Passive States for Essential Observers

The aim of this note is to present a unified approach to the results given in \cite{bb99} and \cite{bs04} which also covers examples of models not presented in these two papers (e.g. $d$-dimensional Minkowski space-time for $d\geq 3$). Assuming that a state is passive for an observer travelling along certain (essential) worldlines, we show that this state is invariant under the isometry group, is a KMS-state for the observer at a temperature uniquely determined by the structure constants of the Lie algebra involved and fulfills (a variant of) the Reeh-Schlieder property. Also the modular objects associated to such a state and the observable algebra of an observer are computed and a version of weak locality is examined.Comment: 27 page

Documenting Nursing and Medical Students’ Stereotypes about Hispanic and American Indian Patients

Objective: Hispanic Americans and American Indians face significant health disparities compared with White Americans. Research suggests that stereotyping of minority patients by members of the medical community is an important antecedent of race and ethnicity-based health disparities. This work has primarily focused on physicians’ perceptions, however, and little research has examined the stereotypes healthcare personnel associate with Hispanic and American Indian patients. The present study assesses: 1) the health-related stereotypes both nursing and medical students hold about Hispanic and American Indian patients, and 2) nursing and medical students’ motivation to treat Hispanic and American Indian patients in an unbiased manner. Design: Participants completed a questionnaire assessing their awareness of stereotypes that healthcare professionals associate with Hispanic and American Indian patients then completed measures of their motivation to treat Hispanics and American Indians in an unbiased manner. Results: Despite being highly motivated to treat Hispanic and American Indian individuals fairly, the majority of participants reported awareness of stereotypes associating these patient groups with noncompliance, risky health behavior, and difficulty understanding and/or communicating health-related information. Conclusion: This research provides direct evidence for negative health-related stereotypes associated with two understudied minority patient groups—Hispanics and American Indians—among both nursing and medical personnel

Low Temperature Magnetic Properties of Siderite and Magnetite in Marine Sediments

Low temperature magnetic techniques provide useful tools to detect the presence of magnetite and pyrrhotite in sediments through identification of their low temperature transitions, to determine the amount of ultrafine-grained (superparamagnetic) material in sediments, and can potentially detect the presence of certain types of magnetotactic bacteria. Application of these types of experiments to nannofossil chalks from beneath the Barbados accretionary prism led to some unusual results, which are attributed to the presence of siderite. Thermal demagnetization of low-temperature remanence after cooling in zero field and in a 2.5 T field both displayed large remanence losses from 20 K to 40 K. Below 40 K, the magnetization of the chalks was much higher in the field-cooled experiments than in the zero-field-cooled experiments. Low temperature hysteresis experiments, made after cooling in a 2.5 T field, displayed offsets in magnetization parallel to the direction of the initial applied field, when measured below 40 K. The offset loops can be due to either an exchange anisotropy between siderite and magnetite phases in the sediments, a defect moment in the siderites, or a canted moment in the siderites. Apparent similarity between the low-temperature thermal demagnetization results from these siderite-bearing sediments, pure siderite, and pure rhodochrosite samples and the well-known 34 K transition in pyrrhotite should lead to caution in identification of pyrrhotite in marine sediments based on low-temperature remanence studies alone

Biomedical research leaders: report on needs, opportunities, difficulties, education and training, and evaluation.

The National Association of Physicians for the Environment (NAPE) has assumed a leadership role in protecting environmental health in recent years. The Committee of Biomedical Research Leaders was convened at the recent NAPE Leadership Conference: Biomedical Research and the Environment held on 1--2 November 1999, at the National Institutes of Health, Bethesda, Maryland. This report summarizes the discussion of the committee and its recommendations. The charge to the committee was to raise and address issues that will promote and sustain environmental health, safety, and energy efficiency within the biomedical community. Leaders from every important research sector (industry laboratories, academic health centers and institutes, hospitals and care facilities, Federal laboratories, and community-based research facilities) were gathered in this committee to discuss issues relevant to promoting environmental health. The conference and this report focus on the themes of environmental stewardship, sustainable development and "best greening practices." Environmental stewardship, an emerging theme within and outside the biomedical community, symbolizes the effort to provide an integrated, synthesized, and concerted effort to protect the health of the environment in both the present and the future. The primary goal established by the committee is to promote environmentally responsible leadership in the biomedical research community. Key outcomes of the committee's discussion and deliberation were a) the need for a central organization to evaluate, promote, and oversee efforts in environmental stewardship; and b) immediate need to facilitate efficient information transfer relevant to protecting the global environment through a database/clearinghouse. Means to fulfill these needs are discussed in this report

A Constrained Path Monte Carlo Method for Fermion Ground States

We describe and discuss a recently proposed quantum Monte Carlo algorithm to compute the ground-state properties of various systems of interacting fermions. In this method, the ground state is projected from an initial wave function by a branching random walk in an over-complete basis of Slater determinants. By constraining the determinants according to a trial wave function $|\psi_T\rangle$, we remove the exponential decay of signal-to-noise ratio characteristic of the sign problem. The method is variational and is exact if $|\psi_T\rangle$ is exact. We illustrate the method by describing in detail its implementation for the two-dimensional one-band Hubbard model. We show results for lattice sizes up to $16\times 16$ and for various electron fillings and interaction strengths. Besides highly accurate estimates of the ground-state energy, we find that the method also yields reliable estimates of other ground-state observables, such as superconducting pairing correlation functions. We conclude by discussing possible extensions of the algorithm.Comment: 29 pages, RevTex, 3 figures included; submitted to Phys. Rev.