8,432 research outputs found

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

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    We investigate the critical parameters of an order-disorder quantum phase transitions in the spin-1/2 JJJ-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

    Cardiovascular medication, physical activity and mortality: cross-sectional population study with ongoing mortality follow up

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    Objective: to establish physical activity levels in relation to cardiovascular medication and to examine if physical activity is associated with benefit independently of medication among individuals with no diagnosis of cardiovascular disease (CVD). Design: Cross-sectional surveys in 1998 and 2003 with ongoing mortality follow up. Setting: Household-based interviews in England and Scotland. Participants: Population samples of adults aged 35 and over living in households, respondents of the Scottish Health Survey and the Health Survey for England. Main outcome measure: Moderate to vigorous physical activity (MVPA) levels and CVD mortality. Results: Fifteen percent (N=3,116) of the 20,177 respondents (8,791 men); were prescribed at least one cardiovascular medication. Medicated respondents were less likely than those unmedicated to meet the physical activity recommendations (OR:0.89, 95%CI: 0.81 to 0.99, p=0.028). The mean follow up (±SD) was 6.6 (2.3) years. There were 1,509 any-cause deaths and 427 CVD deaths. Increased physical activity was associated with all-cause and CVD mortality among both unmedicated (all-cause mortality HR for those with ≥150 min/wk of MVPA compared with those who reported no MVPA): 0.58, 95%CI: 0.48 to 0.69, p<0.001) ; CVD mortality: 0.65, 0.46 to 0.91, p=0.036) and medicated respondents (all-cause death: 0.54, 0.40 to 0.72, p<0.001; CVD death: 0.46 (0.27 to 0.78, p=0.008). Conclusions: Although physical activity protects against premature mortality among both medicated and unmedicated adults, cardiovascular medication is linked with lower uptake of health enhancing physical activity. These results highlight the importance of physical activity in the primary prevention of CVD over and above medication

    Motives for exercise participation as predictors of exercise dependence among endurance athletes

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    Background. To investigate whether motives for exercise participation predicted exercise dependence (ED) among endurance athletes. The rationale for the study centred upon a test of the affect regulation model utilising constructs that form part of the Self-Determination Theory as predictors of ED. It was hypothesised that non self-determined motivation, specifically external regulation, would be predictive of ED.Methods. Design: correlational design, with a time gap between predictor and dependent variables. Settings: competitive sports environment. Participants: 188 competitive endurance athletes were recruited from amateur sports clubs. Interventions: none. Measures: the Behavioural Regulation in Exercise Questionnaire was administered before a training session to measure the predictor variables (motives for exercise participation), and the Running Addiction Scale was administered before a similar training session, one week later, to measure the dependent variable (ED).Results. Multiple regression analysis revealed that the strongest predictor variable of ED was introjected regulation (beta = 0.29, p < 0.001), followed by identified regulation (beta = 0.19, p < 0.05). External regulation and intrinsic motivation were weak and non-significant predictors. The total variance in ED explained by the exercise participation motives was 15% (R-2 = 0.15).Conclusions. ED was predicted by motives that did not support the tenets of the affect regulation model. Results are discussed in light of the potential influence of exercise participation motives on ED and their implications for intervention strategies and diagnosis of the ED syndrome

    Television viewing time and risk of incident obesity and central obesity: the English longitudinal study of ageing

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    Background Research suggests television viewing time may be associated with incident obesity and central obesity in young adults. No study has investigated these associations in older English adults. The aim of this study was to investigate longitudinal associations between television viewing time and incident obesity and central obesity in a sample of older English adults. Analyses of data from the English Longitudinal Study of Ageing. At baseline (2008), participants reported their television viewing time. Research nurses recorded obesity and central obesity by body mass index and waist circumference, respectively, at four year follow-up. Associations between television viewing time and incident obesity (BMI > 30 kg/m2) and central obesity (waist >102 cm men; > 88 cm women) at four year follow-up were examined using adjusted logistic regression. Participants gave full written informed consent to participate in the study and ethical approval was obtained from the London Multicentre Research Ethics Committee. Results A total of 3777 initially non-obese participants (aged 64.8 ± 8.6 yrs, 46.4% male) were included in the analyses using BMI as an outcome and 2947 for the analyses using waist circumference. No significant associations were found between television viewing time and incident obesity. A significant association was found between watching ≥6 hrs/d of television (compared to <2 hrs/d) and central obesity (Odds Ratio 1.48; 95% confidence interval 1.07 to 2.03) after adjustment for covariables including physical activity. Conclusions In this sample of older community dwelling English adults greater television viewing time was associated with incident central obesity, but not total obesity when measured by BMI. Interventions to reduce the incidence of central obesity in this age group that focus on reducing TV time, as well as targeting other health behaviours (eg, increasing physical activity levels, improving dietary intake) might prove useful

    Optimization of thrust algorithm calibration for Computing System (TCS) for Thrust the NASA Highly Maneuverable Aircraft Technology (HiMAT) vehicle's propulsion system

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    A simplified gross thrust computing technique for the HiMAT J85-GE-21 engine using altitude facility data was evaluated. The results over the full engine envelope for both the standard engine mode and the open nozzle engine mode are presented. Results using afterburner casing static pressure taps are compared to those using liner static pressure taps. It is found that the technique is very accurate for both the standard and open nozzle engine modes. The difference in the algorithm accuracy for a calibration based on data from one test condition was small compared to a calibration based on data from all of the test conditions

    Prospective study of coffee and tea consumption in relation to risk of type 2 diabetes mellitus among men and women: The Whitehall II study

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    At least fourteen cohort studies have documented all inverse association between coffee consumption and risk of type 2 diabetes. We examined the prospective association between coffee and tea consumption and the risk of type 2 diabetes mellitus among British men (n 4055) and women (n 1768) from the Whitehall II cohort. During 11.7 years follow-up there were a total of 387 incident cases of diabetes confirmed by Self-report of doctor's diagnosis or glucose tolerance tests. Despite an inverse association between coffee intake and 2 h post-load glucose concentration at the baseline assessment, combined caffeinated and decaffeinated coffee (hazard ratio (HR) 0-80 95% CI 0.54, 1.18) or only decaffeinated coffee intake (HR 0.65: 95% CI 0.36, 1.16) was not significantly associated with diabetes risk at follow-up after adjustment for possible confounders. There was all association between tea intake and diabetes (HR 0.66: 95% CI 0.61, 1.22: P<0.05) after adjustment for age. gender. ethnicity and social status, which was not robust to further adjustments. There was. however, an association between combined intake of tea and coffee (two or more cups per clay of both beverage) and diabetes (HR 0.68: 95% CI 0.46, 0.99: P<0.05) after full adjustment. In conclusion, relatively moderate intake (more than three CLIPS per (lay) of coffee and tea were not prospectively associated with incidence of type 2 diabetes although there was evidence of a combined effect. The limited range of exposure and beverage consumption according to socio-economic class may explain these conflicting findings

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

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    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

    Path Integral Monte Carlo Approach to the U(1) Lattice Gauge Theory in (2+1) Dimensions

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    Path Integral Monte Carlo simulations have been performed for U(1) lattice gauge theory in (2+1) dimensions on anisotropic lattices. We extractthe static quark potential, the string tension and the low-lying "glueball" spectrum.The Euclidean string tension and mass gap decrease exponentially at weakcoupling in excellent agreement with the predictions of Polyakov and G{\" o}pfert and Mack, but their magnitudes are five times bigger than predicted. Extrapolations are made to the extreme anisotropic or Hamiltonian limit, and comparisons are made with previous estimates obtained in the Hamiltonian formulation.Comment: 12 pages, 16 figure