Quantum phase transitions in the J-J' Heisenberg and XY spin-1/2 antiferromagnets on square lattice: Finite-size scaling analysis

We investigate the critical parameters of an order-disorder quantum phase transitions in the spin-1/2 $J-J'$ Heisenberg and XY antiferromagnets on square lattice. Basing on the excitation gaps calculated by exact diagonalization technique for systems up to 32 spins and finite-size scaling analysis we estimate the critical couplings and exponents of the correlation length for both models. Our analysis confirms the universal critical behavior of these quantum phase transitions: They belong to 3D O(3) and 3D O(2) universality classes, respectively.Comment: 7 pages, 3 figure

Direct-use Values of Non-Timber Forest Products from Two Areas on the Transkei Wild Coast

It is now widely appreciated internationally that rural communities make extensive use of wild resources, and that this use has significant direct use value. The number of case studies in South Africa that have valued the use of such resources are small, albeit growing. Yet none of them have been from coastal sites, which would include use of marine resources, nor have previous studies included the non-biological resources of sand and clay for building purposes. This paper addresses this gap, through examination of the role and value of wild resources in rural livelihoods of households in the Ntubeni and Cwebe areas of the Transkei Wild Coast in the Eastern Cape. Households used a wide range of resources collected from the surrounding communal lands and the Dwesa Cwebe Nature Reserve. Major differences between the sites were the widespread use of bushmeat, shellfish and building sand at Ntubeni compared with relatively small use of these three resources at Cwebe. These differences resulted in a markedly higher, gross, annual, direct-use value at Ntubeni than at Cwebe. The gross, annual, direct-use value averaged across all resources (excluding medicinal plants) and all households (user and non-users) was over R12 000 at Ntubeni, compared to R4 858 at Cwebe. At Ntubeni over half of the total annual direct-use value was contributed by fish and shellfish, indicating the need for more studies in coastal areas. A similar pattern was not evident at Cwebe, because residents did not have access to a rocky shoreline outside of the marine reserve. Local trade was highly variable, both between resources and between households. Averaging the value of trade across all households (i.e. traders and non-traders), gave a total gross, annual value of R1 660 and R600 at Ntubeni and Cwebe, respectively.Resource /Energy Economics and Policy,

Physical activity education in the undergraduate curricula of all UK medical schools: are tomorrow's doctors equipped to follow clinical guidelines?

Physical activity (PA) is a cornerstone of disease prevention and treatment. There is, however, a considerable disparity between public health policy, clinical guidelines and the delivery of physical activity promotion within the National Health Service in the UK. If this is to be addressed in the battle against non-communicable diseases, it is vital that tomorrow's doctors understand the basic science and health benefits of physical activity. The aim of this study was to assess the provision of physical activity teaching content in the curricula of all medical schools in the UK. Our results, with responses from all UK medical schools, uncovered some alarming findings, showing that there is widespread omission of basic teaching elements, such as the Chief Medical Officer recommendations and guidance on physical activity. There is an urgent need for physical activity teaching to have dedicated time at medical schools, to equip tomorrow's doctors with the basic knowledge, confidence and skills to promote physical activity and follow numerous clinical guidelines that support physical activity promotion

Temporal variation in abundance and diversity of butterflies in Bornean rain forests: opposite impacts of logging recorded in different seasons

We used traps baited with fruit to examine how the temporal variation of butterflies within primary forest in Sabah, Borneo differed between species. In addition, we compared patterns of temporal variation in primary and selectively logged forest, and we tested the hypothesis that selective logging has different recorded impacts on species diversity of adults during the wet monsoon period and the drier remaining half of the year. Species of Satyrinae and Morphinae had significantly less-restricted flight periods than did species of Nymphalinae and Charaxinae, which were sampled mainly during the drier season. especially in primary forest. Species diversity of adults was significantly higher during the drier season in primary forest, but did not differ between seasons in logged forest. As a consequence, logging had opposite recorded impacts on diversity during wetter and drier seasons: primary forest had significantly higher diversity than logged forest during the drier season but significantly lower diversity than logged forest during the wetter monsoon season. The results of this study have important implications for the assessment of biodiversity in tropical rain forests, particularly in relation to habitat disturbance: short-term assessments that do not take account of seasonal variation in abundance are likely to produce misleading results, even in regions where the seasonal variation in rainfall is not that great

Long-term adherence to healthy dietary guidelines and chronic inflammation in the prospective Whitehall II study

Background Inflammation plays an important role in the cause of cardiovascular diseases and may contribute to the association linking an unhealthy diet to chronic age-related diseases. However, to date the long-term associations between diet and inflammation have been poorly described. Our aim was to assess the extent to which adherence to a healthy diet and dietary improvements over a 6-year exposure period prevented subsequent chronic inflammation over a 5-year follow-up in a large British population of men and women. Methods Data were drawn from 4600 adults (mean ± standard deviation, age 49.6 ± 6.1 years, 28% were women) from the prospective Whitehall cohort II study. Adherence to a healthy diet was measured using Alternative Healthy Eating Index (AHEI) scores in 1991-1993 (50.7 ± 11.9 points) and 1997-1999 (51.6 ± 12.4 points). Chronic inflammation, defined as average levels of serum interleukin-6 from 2 measures 5 years apart, was assessed in 1997-1999 and 2002-2004. Results After adjustment for sociodemographic factors, health behaviors, and health status, participants who maintained a high AHEI score (ie, a healthy diet, n = 1736, 37.7%) and those who improved this score over time (n = 681, 14.8%) showed significantly lower mean levels of interleukin-6 (1.84 pg/mL, 95% confidence interval [CI], 1.71-1.98 and 1.84 pg/mL, 95% CI, 1.70-1.99, respectively) than those who had a low AHEI score (n = 1594, 34.6%) over the 6-year exposure period (2.01 pg/mL, 95% CI, 1.87-2.17). Conclusions These data suggest that maintaining and improving adherence to healthy dietary recommendations may reduce the risk of long-term inflammation.</p

The Massive Schwinger Model in a Fast Moving Frame

We present a non-perturbative study of the massive Schwinger model. We use a Hamiltonian approach, based on a momentum lattice corresponding to a fast moving reference frame, and equal time quantization.Comment: contribution to Lattice'98 including: 2 style files (espcrc2.sty,psfig.sty) + text file (LaTeX) + 3 figures (ps) + complete paper(ps

Localized energy for wave equations with degenerate trapping

Localized energy estimates have become a fundamental tool when studying wave equations in the presence of asymptotically at background geometry. Trapped rays necessitate a loss when compared to the estimate on Minkowski space. A loss of regularity is a common way to incorporate such. When trapping is sufficiently weak, a logarithmic loss of regularity suffices. Here, by studying a warped product manifold introduced by Christianson and Wunsch, we encounter the first explicit example of a situation where an estimate with an algebraic loss of regularity exists and this loss is sharp. Due to the global-in-time nature of the estimate for the wave equation, the situation is more complicated than for the Schr\"{o}dinger equation. An initial estimate with sub-optimal loss is first obtained, where extra care is required due to the low frequency contributions. An improved estimate is then established using energy functionals that are inspired by WKB analysis. Finally, it is shown that the loss cannot be improved by any power by saturating the estimate with a quasimode.Comment: 18 page

Water service delivery challenges in a small South African municipality: Identifying and exploring key elements and relationships in a complex social-ecological system

South Africa is a developing country undergoing social and ecological transformation. Water service delivery (i) exemplifies the challenge of improvement and transformation towards a more socially and ecologically just situation, and (ii) can usefully be viewed as a complex social-ecological system (C-SES) in the search for ‘just transitions’. Household water security problems associated with water service delivery in South Africa are recognisably intractable, multi-scaled, comprising many actors and elements and having no single solution. There is a global and South African trend towards systemic approaches to addressing such complex water challenges. However, the steps required to take a systemic approach are seldom explicit. This paper presents the analytical process of defining boundaries, identifying elements and exploring relationships between elements as the foundational step in a study of the Makana Local Municipality water service delivery C-SES in the Eastern Cape Province of South Africa. The resulting narrative and heuristics provide a clear systemic basis from which to research the emergence, practice and social learning process of a civil society organisation (Water for Dignity) seeking to confront water service delivery issues in the Makana Local Municipality.Keywords: complex adaptive systems, systems inquiry, household water service delivery, civil society organisatio

Monte Carlo simulation of the transmission of measles: Beyond the mass action principle

We present a Monte Carlo simulation of the transmission of measles within a population sample during its growing and equilibrium states by introducing two different vaccination schedules of one and two doses. We study the effects of the contact rate per unit time $\xi$ as well as the initial conditions on the persistence of the disease. We found a weak effect of the initial conditions while the disease persists when $\xi$ lies in the range 1/L-10/L ($L$ being the latent period). Further comparison with existing data, prediction of future epidemics and other estimations of the vaccination efficiency are provided. Finally, we compare our approach to the models using the mass action principle in the first and another epidemic region and found the incidence independent of the number of susceptibles after the epidemic peak while it strongly fluctuates in its growing region. This method can be easily applied to other human, animals and vegetable diseases and includes more complicated parameters.Comment: 15 pages, 4 figures, 1 table, Submitted to Phys.Rev.