The kink-type instability of toroidal stellar magnetic fields with thermal diffusion

The stability of toroidal magnetic fields in rotating radiative stellar zones is studied for realistic values of both the Prandtl numbers. The two considered models for the magnetic geometry represent fields with odd and even symmetry with respect to the equator. In the linear theory in Boussinesq approximation the resulting complex eigenfrequency (including growth rate and drift rate) are calculated for a given radial wavenumber of a nonaxisymmetric perturbation with m=1. The ratio of the Alfven frequency, \Omega_A, to the rate of the basic rotation, \Omega, controls the eigenfrequency of the solution. For strong fields with \Omega_A > \Omega the solutions do not feel the thermal diffusion. The growth rate runs with \Omega_A and the drift rate is close to -\Omega so that the magnetic pattern will rest in the laboratory system. For weaker fields with \Omega_A < \Omega the growth rate strongly depends on the thermal conductivity. For fields with dipolar parity and for typical values of the heat conductivity the resulting very small growth rates are almost identical with those for vanishing gravity. For fields with dipolar symmetry the differential rotation of any stellar radiative zone (like the solar tachocline) is shown as basically stabilizing the instability independent of the sign of the shear. Finally, the current-driven kink-type instability of a toroidal background field is proposed as a model for the magnetism of Ap stars. The recent observation of a lower magnetic field treshold of about 300 Gauss for Ap stars is understood as corresponding to the minimum magnetic field producing the instability.Comment: 11 pages, 7 figures, acc. for publicatio

Campus Cultural Climate: A Minority Perspective

A survey was administered to sixty-five students at The University of Akron, to assess their sentiments toward the cultural climate on their campus. It was hypothesized that minority students, specifically African-Americans, would report lower scores than White students, as previous research has shown that students of color do not perceive their campus cultural climate in as positive of a light as their Caucasian peers. Despite previous notions, students of color at The University of Akron reported a more positive view of campus cultural climate than did White students. A correlational analysis was then done, to see what factors could potentially contribute to one’s perception of overall climate. Interestingly, one’s experiences were significantly correlated to one’s perception of climate, although White students seemed to have a more positive view of their college experiences than did African American students. Given these contradictory findings, it is evident that further research should be done, in order to compare other factors such as living on or off campus

Measuring antibiotic availability and use in 20 low- and middle-income countries

Objective To assess antibiotic availability and use in health facilities in low- and middle-income countries, using the service provision assessment and service availability and readiness assessment surveys. Methods We obtained data on antibiotic availability at 13 561 health facilities in 13 service provision assessment and 8 service availability and readiness assessment surveys. In 10 service provision assessment surveys, child consultations with health-care providers were observed, giving data on antibiotic use in 22 699 children. Antibiotics were classified as access, watch or reserve, according to the World Health Organization’s AWaRe categories. The percentage of health-care facilities across countries with specific antibiotics available and the proportion of children receiving antibiotics for key clinical syndromes were estimated. Findings The surveys assessed the availability of 27 antibiotics (19 access, 7 watch, 1 unclassified). Co-trimoxazole and metronidazole were most widely available, being in stock at 89.5% (interquartile range, IQR: 11.6%) and 87.1% (IQR: 15.9%) of health facilities, respectively. In contrast, 17 other access and watch antibiotics were stocked, by fewer than a median of 50% of facilities. Of the 22 699 children observed, 60.1% (13 638) were prescribed antibiotics (mostly co-trimoxazole or amoxicillin). Children with respiratory conditions were most often prescribed antibiotics (76.1%; 8972/11 796) followed by undifferentiated fever (50.1%; 760/1518), diarrhoea (45.7%; 1293/2832) and malaria (30.3%; 352/1160). Conclusion Routine health facility surveys provided a valuable data source on the availability and use of antibiotics in low- and middle-income countries. Many access antibiotics were unavailable in a majority of most health-care facilities

Assessing national sanitation policy for effectiveness: lessons from Nepal and Ghana

Providing improved sanitation services can contribute directly to a number of the Millennium Development Goals and the alleviation of global poverty. This contribution can be maximized through the development of appropriate national sanitation policies to enable the implementation of national strategies and programmes. Only then can the scale of the sanitation need be effectively addressed. This paper presents the process and findings of research carried out in Nepal and Ghana to test guidelines for assessing national sanitation policies. It explains how the guidelines were applied and where they were modified to suit the context of the case study countries. Findings from the research look to both inform the future application of the guidelines and ongoing development of national sanitation policies. The paper is one of a series of outputs developed on the basis of the research project

Dissipative Taylor-Couette flows under the influence of helical magnetic fields

The linear stability of MHD Taylor-Couette flows in axially unbounded cylinders is considered, for magnetic Prandtl number unity. Magnetic fields varying from purely axial to purely azimuthal are imposed, with a general helical field parameterized by \beta=B_\phi/B_z. We map out the transition from the standard MRI for \beta=0 to the nonaxisymmetric Azimuthal MagnetoRotational Instability (AMRI) for \beta\to \infty. For finite \beta, positive and negative wave numbers m, corresponding to right and left spirals, are no longer identical. The transition from \beta=0 to \beta\to\infty includes all the possible forms of MRI with axisymmetric and nonaxisymmetric modes. For the nonaxisymmetric modes, the most unstable mode spirals in the opposite direction to the background field. The standard (\beta=0) MRI is axisymmetric for weak fields (including the instability with the lowest Reynolds number) but is nonaxisymmetric for stronger fields. If the azimuthal field is due in part to an axial current flowing through the fluid itself (and not just along the central axis), then it is also unstable to the nonaxisymmetric Tayler instability, which is most effective without rotation. For large \beta this instability has wavenumber m=1, whereas for \beta\simeq 1 m=2 is most unstable. The most unstable mode spirals in the same direction as the background field.Comment: 9 pages, 11 figure

The Origin of Solar Activity in the Tachocline

Solar active regions, produced by the emergence of tubes of strong magnetic field in the photosphere, are restricted to within 35 degrees of the solar equator. The nature of the dynamo processes that create and renew these fields, and are therefore responsible for solar magnetic phenomena, are not well understood. We analyze the magneto-rotational stability of the solar tachocline for general field geometry. This thin region of strong radial and latitudinal differential rotation, between the radiative and convective zones, is unstable at latitudes above 37 degrees, yet is stable closer to the equator. We propose that small-scale magneto-rotational turbulence prevents coherent magnetic dynamo action in the tachocline except in the vicinity of the equator, thus explaining the latitudinal restriction of active regions. Tying the magnetic dynamo to the tachocline elucidates the physical conditions and processes relevant to solar magnetism.Comment: 10 pages, 1 figure, accepted for publication in ApJ

The Effects of Alcohol Consumption and Perception of Normative Behaviors on Risky Sexual Behavior Among College Students

Recent research suggests that a majority of college students report having sex with multiple partners while practicing inconsistent condom use. These reports can be attributed to heavy drinking habits and perceived approval of behavior based on social interactions. The purpose of this study was to examine the effects that alcohol consumption and perceptions of peer behavior have on risky sexual behavior among college students. The present study recruited 50 students from the University of Arkansas to participate in an anonymous survey on their drinking habits, risky sexual behavior, and their perception of normative risky sexual behavior. Correlational analyses revealed a positive relationship between risky sexual behavior and alcohol consumption. Regression analysis suggests that drinking behavior and perception of peer risky sexual behavior influence actual risky sexual behavior. Implications for future research and educational programming are presented

Assessing Nepal's national sanitation policy

Many researchers and commentators on sanitation have recognised that relevant and effective policies play an important role in ensuring sanitation is addressed at sufficient scale that progress is made towards national sanitation targets in support of the Millennium Development Goals (MDGs). With this in mind, the Environmental Health Programme (EHP) of USAID developed a written ‘Guidelines for the Assessment of National Sanitation Policies’ in 2002, to help countries assess the effectiveness of policy in enabling an environment that encourages effective programmes and strategies. Nepal was selected as one of two countries for field-testing the EHP Guidelines as part of DFID-funded research carried out by WEDC in collaboration with Development Network, a national consulting research firm in Nepal. This paper highlights key findings based on the research process, with implications for challenges facing Nepal in effectively implementing sanitation policy

Nonaxisymmetric Magnetorotational Instability in Proto-Neutron Stars

We investigate the stability of differentially rotating proto-neutron stars (PNSs) with a toroidal magnetic field. Stability criteria for nonaxisymmetric MHD instabilities are derived using a local linear analysis. PNSs are expected to have much stronger radial shear in the rotation velocity compared to normal stars. We find that nonaxisymmetric magnetorotational instability (NMRI) with a large azimuthal wavenumber $m$ is dominant over the kink mode ($m=1$) in differentially rotating PNSs. The growth rate of the NMRI is of the order of the angular velocity $\Omega$ which is faster than that of the kink-type instability by several orders of magnitude. The stability criteria are analogous to those of the axisymmetric magnetorotational instability with a poloidal field, although the effects of leptonic gradients are considered in our analysis. The NMRI can grow even in convectively stable layers if the wavevectors of unstable modes are parallel to the restoring force by the Brunt-V\"ais\"al\"a oscillation. The nonlinear evolution of NMRI could amplify the magnetic fields and drive MHD turbulence in PNSs, which may lead to enhancement of the neutrino luminosity.Comment: 24pages, 7figures, Accepted for publication in the Astrophysical Journal (December 12, 2005

Sexual violence in post-conflict Liberia: survivors and their care.

Using routine data from three clinics offering care to survivors of sexual violence (SV) in Monrovia, Liberia, we describe the characteristics of SV survivors and the pattern of SV and discuss how the current approach could be better adapted to meet survivors' needs. There were 1500 survivors seeking SV care between January 2008 and December 2009. Most survivors were women (98%) and median age was 13 years (Interquartile range: 9-17 years). Sexual aggression occurred during day-to-day activities in 822 (55%) cases and in the survivor's home in 552 (37%) cases. The perpetrator was a known civilian in 1037 (69%) SV events. Only 619 (41%) survivors sought care within 72 h. The current approach could be improved by: effectively addressing the psychosocial needs of child survivors, reaching male survivors, targeting the perpetrators in awareness and advocacy campaigns and reducing delays in seeking care