Quantum dynamics of the avian compass

The ability of migratory birds to orient relative to the Earth's magnetic field is believed to involve a coherent superposition of two spin states of a radical electron pair. However, the mechanism by which this coherence can be maintained in the face of strong interactions with the cellular environment has remained unclear. This Letter addresses the problem of decoherence between two electron spins due to hyperfine interaction with a bath of spin 1/2 nuclei. Dynamics of the radical pair density matrix are derived and shown to yield a simple mechanism for sensing magnetic field orientation. Rates of dephasing and decoherence are calculated ab initio and found to yield millisecond coherence times, consistent with behavioral experiments

Neutron spin-echo study of the critical dynamics of spin-5/2 antiferromagnets in two and three dimensions

We report a neutron spin-echo study of the critical dynamics in the $S=5/2$ antiferromagnets MnF$_2$ and Rb$_2$MnF$_4$ with three-dimensional (3D) and two-dimensional (2D) spin systems, respectively, in zero external field. Both compounds are Heisenberg antiferromagnets with a small uniaxial anisotropy resulting from dipolar spin-spin interactions, which leads to a crossover in the critical dynamics close to the N\'eel temperature, $T_N$. By taking advantage of the $\mu\text{eV}$ energy resolution of the spin-echo spectrometer, we have determined the dynamical critical exponents $z$ for both longitudinal and transverse fluctuations. In MnF$_2$, both the characteristic temperature for crossover from 3D Heisenberg to 3D Ising behavior and the exponents $z$ in both regimes are consistent with predictions from the dynamical scaling theory. The amplitude ratio of longitudinal and transverse fluctuations also agrees with predictions. In Rb$_2$MnF$_4$, the critical dynamics crosses over from the expected 2D Heisenberg behavior for $T\gg T_N$ to a scaling regime with exponent $z = 1.387(4)$, which has not been predicted by theory and may indicate the influence of long-range dipolar interactions

How do hospital doctors manage patients with medically unexplained symptoms: a qualitative study of physicians

OBJECTIVE: Medically unexplained symptoms are a common presentation in medical practice and are associated with significant morbidity and high levels of service use. Most research exploring the attitudes and training of doctors in treating patients with unexplained symptoms has been conducted in primary care. This study aims to explore the ways in which doctors working in secondary care approach and manage patients with medically unexplained symptoms. DESIGN: A qualitative study using in-depth interviews and thematic analysis. SETTING: Three hospitals in the North Thames area. PARTICIPANTS: Twenty consultant and training-grade physicians working in cardiology, gastroenterology, rheumatology and neurology. MAIN OUTCOME MEASURE: Physicians' approach to patients with medically unexplained symptoms and their views on managing these patients. RESULTS: There was considerable variation in how the physicians approached patients who presented with medically unexplained symptoms. Investigations were often ordered without a clear rationale and the explanations given to patients when results of investigations were normal were highly variable, both within and across specialties. The doctor's level of experience appeared to be a more important factor in their investigation and management strategies than their medical specialty. Physicians reported little or no formal training in how to manage such presentations, with no apparent consistency in how they had developed their approach. Doctors described learning from their own experience and from senior role models. Organisational barriers were identified to the effective management of these patients, particularly in terms of continuity of care. CONCLUSIONS: Given the importance of this topic, there is a need for serious consideration as to how the management of patients with medically unexplained symptoms is included in medical training and in the planning and delivery of services

Permeability characteristics of the human nail plate

The permeation of chemicals across the nail plate and their consequent effects are discussed in relation to cosmetic toxicity and possible clinical efficacy. The reviewed data are then assessed and placed in context with recent observations on the direct assessment of permeability of the human nail plate. Although marked differences between the diffusional barrier characteristics of nail and stratum corneum are shown, a reasonably unified picture of nail plate permeability is drawn from the collective observations. The cosmetic and clinical implications of chemical penetration of the nail plate are briefly outlined and places where knowledge needs to be strengthened are identified. La permÉabilitÉ de l'ongie humainPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72442/1/j.1467-2494.1983.tb00348.x.pd

Shades of Grey: Ethical Dilemmas

No abstract available

Black Hole Entropy, Topological Entropy and the Baum-Connes Conjecture in K-Theory

We shall try to exhibit a relation between black hole entropy and topological entropy using the famous Baum-Connes conjecture for foliated manifolds which are particular examples of noncommutative spaces. Our argument is qualitative and it is based on the microscopic origin of the Beckenstein-Hawking area-entropy formula for black holes, provided by superstring theory, in the more general noncommutative geometric context of M-Theory following the Connes- Douglas-Schwarz article.Comment: 17 pages, Latex, contains an important paragraph in section 2 which gives a better understandin

EFFECTS OF RISK ON OPTIMAL NITROGEN FERTILIZATION DATES IN WINTER WHEAT PRODUCTION AS AFFECTED BY DISEASE AND NITROGEN SOURCE

Optimal fertilization dates were found for two nitrogen sources in the presence of two diseases for wheat farmers with different risk preferences. Risk was independent of fertilization date. Ammonium Nitrate and Urea-Ammonium Nitrate did not affect risk differently. Ammonium Nitrate applied on March 9 was optimal regardless of risk preferences.Crop Production/Industries,

Is there an association between perceived social support and cardiovascular health behaviours in people with severe mental illnesses?

PURPOSE: People with severe mental illnesses (SMI) have an increased risk of cardiovascular disease (CVD). Research in the general population suggests that social support may protect against increased CVD morbidity and mortality; however, this may not apply to those with SMI. We aimed to explore the association between perceived social support and attendance at primary care nurse CVD risk reduction clinic appointments and CVD risk-reducing behaviours in an SMI population with elevated CVD risk factors. METHODS: We used longitudinal and cross-sectional data from a randomised controlled trial on 326 adults with SMI recruited via 76 general practices in England. Multilevel regression analysis estimated the effect of perceived social support on attendance at CVD risk reduction clinic appointments over 6 months, and adherence to CVD medication, physical activity, diet, smoking and alcohol use at baseline, adjusted by age, sex, ethnicity, deprivation, psychiatric diagnosis and employment. RESULTS: Perceived social support predicted greater appointment attendance in unadjusted (IRR = 1.005; 1.000-1.010; p = 0.05) but not adjusted analysis (IRR = 1.003; 0.998-1.009; p = 0.25). Perceived social support was associated with greater adherence to medication; for each 1% increase in social support, there was a 4.2% increase in medication adherence (OR = 1.042; 1.015-1.070; p = 0.002). No association was found between greater perceived social support and greater physical activity, lower sedentary behaviour, healthier diet, lower alcohol use or being a non-smoker. CONCLUSIONS: Social support may be an important facilitator for CVD medication adherence and is potentially important for primary care appointment attendance; however, alternative strategies might be needed to help people with SMI engage in physical activity, healthier diets and to reduce their smoking and alcohol use

EFFECTS OF RISK, DISEASE, AND NITROGEN SOURCE ON OPTIMAL NITROGEN FERTILIZATION RATES IN WINTER WHEAT PRODUCTION

Interactions among nitrogen (N) fertilization rate, N source, and disease severity can affect mean yield and yield variance in conservation tillage wheat production. A Just-Pope model was used to evaluate the effects of N rate, N source, and disease on the spring N-fertilization decision. Ammonium nitrate (AN) was the utility-maximizing N source regardless of risk preferences. The net-return-maximizing AN rate was 92 lb N/acre, providing $0.52/acre higher net returns than the best alternative N source (urea). If a farmer could anticipate a higher than average Take-All infection, the difference in optimal net-returns between AN and urea would increase to$35.11/acre.Crop Production/Industries,