Linearized model Fokker-Planck collision operators for gyrokinetic simulations. II. Numerical implementation and tests

A set of key properties for an ideal dissipation scheme in gyrokinetic simulations is proposed, and implementation of a model collision operator satisfying these properties is described. This operator is based on the exact linearized test-particle collision operator, with approximations to the field-particle terms that preserve conservation laws and an H-Theorem. It includes energy diffusion, pitch-angle scattering, and finite Larmor radius effects corresponding to classical (real-space) diffusion. The numerical implementation in the continuum gyrokinetic code GS2 is fully implicit and guarantees exact satisfaction of conservation properties. Numerical results are presented showing that the correct physics is captured over the entire range of collisionalities, from the collisionless to the strongly collisional regimes, without recourse to artificial dissipation.Comment: 13 pages, 8 figures, submitted to Physics of Plasmas; typos fixe

Is Incarceration a Contributor to Health Disparities? Access to Care of Formerly Incarcerated Adults

Despite the disproportionate prevalence of incarceration in communities of color, few studies have examined its contribution to health disparities. We examined whether a lifetime history of incarceration is associated with recent access to medical and dental care. We performed a secondary data analysis of the 2007 Los Angeles County Health Survey, a population-based random-digit-dialing telephone survey of county households. Any history of incarceration in a prison/jail/detention center as an adult was assessed for a random subsample. Bivariate and multivariate logistic regression analyses examined whether incarceration history was associated with access to care, controlling for other characteristics. Ten percent of our study population reported a history of incarceration. While persons with an incarceration history were similar to their peers with regard to health and insurance status, their access to medical and dental care was worse. Incarceration history was independently associated with disparities in access to care. Interventions to improve the health of communities affected by high rates of incarceration could include efforts that enable access to care for formerly incarcerated adults

Saturated State of the Nonlinear Small-Scale Dynamo

We consider the problem of incompressible, forced, nonhelical, homogeneous and isotropic MHD turbulence with no mean magnetic field and large magnetic Prandtl number. This type of MHD turbulence is the end state of the turbulent dynamo, which generates folded fields with small-scale direction reversals. We propose a model in which saturation is achieved as a result of the velocity statistics becoming anisotropic with respect to the local direction of the magnetic folds. The model combines the effects of weakened stretching and quasi-two-dimensional mixing and produces magnetic-energy spectra in remarkable agreement with numerical results at least in the case of a one-scale flow. We conjecture that the statistics seen in numerical simulations could be explained as a superposition of these folded fields and Alfv\'en-like waves that propagate along the folds.Comment: revtex, 4 pages, 2 figures; minor changes to match published versio

On the Origin of Cosmic Magnetic Fields

We review the literature concerning how the cosmic magnetic fields pervading nearly all galaxies actually got started. some observational evidence involves the chemical abundance of the light elements Be and B, while another one is based on strong magnetic fields seen in high red shift galaxies. Seed fields, whose strength is of order 10^{-20} gauss, easily sprung up in the era preceding galaxy formation. Several mechanisms are proposed to amplify these seed fields to microgauss strengths. The standard mechanism is the Alpha-Omega dynamo theory. It has a major difficulty that makes unlikely to provide the sole origin. The difficulty is rooted in the fact that the total flux is constant. This implies that flux must be removed from the galactic discs. This requires that the field and flux be separated, for otherwise interstellar mass must be removed from the deep galactic gravitational and then their strength increased by the alpha omega theory.Comment: 90 pages and 6 figures; accepted for publication in Reports of Progress in Physics as an invited revie

Hard-boiled Ecologies: Ross Macdonald’s Environmental Crime Fiction

Although Ross Macdonald’s position in the annals of great American hardboiled crime writers is unquestioned, what often been overlooked in the study of his works are the underlying environmental preoccupations that frequently serve as the background to, or context for, crime. This context of ecological violence is forcefully manifested in two of Macdonald’s later Archer novels The Underground Man (1971) and Sleeping Beauty (1973). This essay scrutinizes the environmental imperatives of Macdonald’s work, arguing that the damage and destruction inflicted upon the environment in these two texts becomes symbiotically connected to the broader, morally fraught social milieu of the city

A blind detection of a large, complex, Sunyaev--Zel'dovich structure

We present an interesting Sunyaev-Zel'dovich (SZ) detection in the first of the Arcminute Microkelvin Imager (AMI) 'blind', degree-square fields to have been observed down to our target sensitivity of 100{\mu}Jy/beam. In follow-up deep pointed observations the SZ effect is detected with a maximum peak decrement greater than 8 \times the thermal noise. No corresponding emission is visible in the ROSAT all-sky X-ray survey and no cluster is evident in the Palomar all-sky optical survey. Compared with existing SZ images of distant clusters, the extent is large (\approx 10') and complex; our analysis favours a model containing two clusters rather than a single cluster. Our Bayesian analysis is currently limited to modelling each cluster with an ellipsoidal or spherical beta-model, which do not do justice to this decrement. Fitting an ellipsoid to the deeper candidate we find the following. (a) Assuming that the Evrard et al. (2002) approximation to Press & Schechter (1974) correctly gives the number density of clusters as a function of mass and redshift, then, in the search area, the formal Bayesian probability ratio of the AMI detection of this cluster is 7.9 \times 10^4:1; alternatively assuming Jenkins et al. (2001) as the true prior, the formal Bayesian probability ratio of detection is 2.1 \times 10^5:1. (b) The cluster mass is MT,200 = 5.5+1.2\times 10^14h-1M\odot. (c) Abandoning a physical model with num- -1.3 70 ber density prior and instead simply modelling the SZ decrement using a phenomenological {\beta}-model of temperature decrement as a function of angular distance, we find a central SZ temperature decrement of -295+36 {\mu}K - this allows for CMB primary anisotropies, receiver -15 noise and radio sources. We are unsure if the cluster system we observe is a merging system or two separate clusters.Comment: accepted MNRAS. 12 pages, 9 figure

Simulation of the Magnetothermal Instability

In many magnetized, dilute astrophysical plasmas, thermal conduction occurs almost exclusively parallel to magnetic field lines. In this case, the usual stability criterion for convective stability, the Schwarzschild criterion, which depends on entropy gradients, is modified. In the magnetized long mean free path regime, instability occurs for small wavenumbers when (dP/dz)(dln T/dz) > 0, which we refer to as the Balbus criterion. We refer to the convective-type instability that results as the magnetothermal instability (MTI). We use the equations of MHD with anisotropic electron heat conduction to numerically simulate the linear growth and nonlinear saturation of the MTI in plane-parallel atmospheres that are unstable according to the Balbus criterion. The linear growth rates measured from the simulations are in excellent agreement with the weak field dispersion relation. The addition of isotropic conduction, e.g. radiation, or strong magnetic fields can damp the growth of the MTI and affect the nonlinear regime. The instability saturates when the atmosphere becomes isothermal as the source of free energy is exhausted. By maintaining a fixed temperature difference between the top and bottom boundaries of the simulation domain, sustained convective turbulence can be driven. MTI-stable layers introduced by isotropic conduction are used to prevent the formation of unresolved, thermal boundary layers. We find that the largest component of the time-averaged heat flux is due to advective motions as opposed to the actual thermal conduction itself. Finally, we explore the implications of this instability for a variety of astrophysical systems, such as neutron stars, the hot intracluster medium of galaxy clusters, and the structure of radiatively inefficient accretion flows.Comment: Accepted for publication in Astrophysics and Space Science as proceedings of the 6th High Energy Density Laboratory Astrophysics (HEDLA) Conferenc

Routine Opt-Out HIV Testing Strategies in a Female Jail Setting: A Prospective Controlled Trial

Background: Ten million Americans enter jails annually. The objective was to evaluate new CDC guidelines for routine optout HIV testing and examine the optimal time to implement routine opt-out HIV testing among newly incarcerated jail detainees. Methods: This prospective, controlled trial of routine opt-out HIV testing was conducted among 323 newly incarcerated female inmates in Connecticut’s only women’s jail. 323 sequential entrants to the women’s jail over a five week period in August and September 2007 were assigned to be offered routine opt-out HIV testing at one of three points after incarceration: immediate (same day, n = 108), early (next day, n = 108), or delayed (7 days, n = 107). The primary outcome was the proportion of women in each group consenting to testing. Results: Routine opt-out HIV testing was significantly highest (73%) among the early testing group compared to 55 % for immediate and 50 % for 7 days post-entry groups. Other factors significantly (p = 0.01) associated with being HIV tested were younger age and low likelihood of early release from jail based on bond value or type of charge for which women were arrested. Conclusions: In this correctional facility, routine opt-out HIV testing in a jail setting was feasible, with highest rates of testing if performed the day after incarceration. Lower testing rates were seen with immediate testing, where there is a high prevalence of inability or unwillingness to test, and with delayed testing, where attrition from jail increases with each passing day

A primary care, multi-disciplinary disease management program for opioid-treated patients with chronic non-cancer pain and a high burden of psychiatric comorbidity

BACKGROUND: Chronic non-cancer pain is a common problem that is often accompanied by psychiatric comorbidity and disability. The effectiveness of a multi-disciplinary pain management program was tested in a 3 month before and after trial. METHODS: Providers in an academic general medicine clinic referred patients with chronic non-cancer pain for participation in a program that combined the skills of internists, clinical pharmacists, and a psychiatrist. Patients were either receiving opioids or being considered for opioid therapy. The intervention consisted of structured clinical assessments, monthly follow-up, pain contracts, medication titration, and psychiatric consultation. Pain, mood, and function were assessed at baseline and 3 months using the Brief Pain Inventory (BPI), the Center for Epidemiological Studies-Depression Scale scale (CESD) and the Pain Disability Index (PDI). Patients were monitored for substance misuse. RESULTS: Eighty-five patients were enrolled. Mean age was 51 years, 60% were male, 78% were Caucasian, and 93% were receiving opioids. Baseline average pain was 6.5 on an 11 point scale. The average CESD score was 24.0, and the mean PDI score was 47.0. Sixty-three patients (73%) completed 3 month follow-up. Fifteen withdrew from the program after identification of substance misuse. Among those completing 3 month follow-up, the average pain score improved to 5.5 (p = 0.003). The mean PDI score improved to 39.3 (p < 0.001). Mean CESD score was reduced to 18.0 (p < 0.001), and the proportion of depressed patients fell from 79% to 54% (p = 0.003). Substance misuse was identified in 27 patients (32%). CONCLUSIONS: A primary care disease management program improved pain, depression, and disability scores over three months in a cohort of opioid-treated patients with chronic non-cancer pain. Substance misuse and depression were common, and many patients who had substance misuse identified left the program when they were no longer prescribed opioids. Effective care of patients with chronic pain should include rigorous assessment and treatment of these comorbid disorders and intensive efforts to insure follow up

General practice vs surgical-based follow-up for patients with colon cancer: randomised controlled trial

This trial examined the optimal setting for follow-up of patients after treatment for colon cancer by either general practitioners or surgeons. In all, 203 consenting patients who had undergone potentially curative treatment for colon cancer were randomised to follow-up by general practitioners or surgeons. Follow-up guidance recommended three monthly clinical review and annual faecal occult blood tests (FOBT) and were identical in both study arms. Primary outcome measures (measured at baseline, 12 and 24 months were (1) quality of life, SF-12; physical and mental component scores, (2) anxiety and depression: Hospital Anxiety and Depression Scale and (3) patient satisfaction: Patient Visit-Specific Questionnaire. Secondary outcomes (at 24 months) were: investigations, number and timing of recurrences and deaths. In all, 170 patients were available for follow-up at 12 months and 157 at 24 months. At 12 and 24 months there were no differences in scores for quality of life (physical component score, P=0.88 at 12 months; P=0.28 at 24 months: mental component score, P=0.51, P=0.47; adjusted), anxiety (P=0.72; P=0.11) depression (P=0.28; P=0.80) or patient satisfaction (P=0.06, 24 months). General practitioners ordered more FOBTs than surgeons (rate ratio 2.4, 95% CI 1.4–4.4), whereas more colonoscopies (rate ratio 0.7, 95% CI 0.5–1.0), and ultrasounds (rate ratio 0.5, 95% CI 0.3–1.0) were undertaken in the surgeon-led group. Results suggest similar recurrence, time to detection and death rates in each group. Colon cancer patients with follow-up led by surgeons or general practitioners experience similar outcomes, although patterns of investigation vary