Petawatt laser absorption bounded

The interaction of petawatt ($10^{15}\ \mathrm{W}$) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light $f$, and even the range of $f$ is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that $f$ exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials

Comparison of research framing preferences and information use of state legislators and advocates involved in cancer control, United States, 2012–2013

INTRODUCTION: Evidence-based policy plays an important role in prevention of cancer and other chronic diseases. The needs of actors involved in policy decision-making should inform knowledge translation strategies. This study examines the differences between state legislators and advocates in how they seek and use information and what their preferences are for how research information is framed. METHODS: We conducted a cross-sectional comparison of survey responses by US advocates (n = 77) and state legislators (n = 265) working on issues related to cancer control. RESULTS: Advocates differed significantly from legislators on all demographic characteristics. Advocates reported seeking and using information more frequently than legislators, though legislators used legislative research bureaus more often (0.45 point difference, P = .004). Both legislators and advocates prioritized the presentation and timeliness of research information similarly but reported different preferences for source (information bias, information relevance, delivery of information by trusted person) of research information. Several differences between advocates and legislators were modified by participant age. CONCLUSION: Our study provides insights for development of knowledge translation strategies to enhance evidence-based policy making for cancer control that are tailored to state-level legislators and advocates. Additional research efforts should evaluate the effectiveness of such knowledge translation strategies, particularly among advocates

Opportunities for promoting physical activity in rural communities by understanding the interests and values of community members

Purpose. Physical activity (PA) has well-established health benefits, but most Americans do not meet national guidelines. In southeastern Missouri, trails have been developed to increase rates of PA. Although this has had success, broad-scale interventions will be needed to improve rates further. In this study, we surveyed residents of southeastern Missouri to identify ways to improve rates of PA. Methods. We conducted a telephone survey in 2015 of adults (n=524) from eight rural Missouri towns that had walking trails, regarding their activities and interests. Findings. Forty percent of respondents reported both walking and meeting PA recommendations, 29% reported walking but not meeting PA recommendations, and the remainder did not walk or did not answer. Respondents who used the trails were significantly more likely to meet PA recommendations (odds ratio = 2.7; 95% confidence interval = 1.7, 4.5). Certain values and interests that may encourage PA or draw people to trails were common. Conclusions. The group that walked but did not meet PA recommendations would be the ideal group to target for intervention, which could focus on their reported values and interests (e.g., personal relationships, being outdoors). Use of walking trails was associated with meeting PA recommendations

Improving the performance of independent task assignment heuristics minmin, maxmin and mufferage

Cataloged from PDF version of article.MinMin, MaxMin, and Sufferage are constructive heuristics that are widely and successfully used in assigning independent tasks to processors in heterogeneous computing systems. All three heuristics are known to run in O(KN2) time in assigning N tasks to K processors. In this paper, we propose an algorithmic improvement that asymptotically decreases the running time complexity of MinMin to O(KN log N) without affecting its solution quality. Furthermore, we combine the newly proposed MinMin algorithm with MaxMin as well as Sufferage, obtaining two hybrid algorithms. The motivation behind the former hybrid algorithm is to address the drawback of MaxMin in solving problem instances with highly skewed cost distributions while also improving the running time performance of MaxMin. The latter hybrid algorithm improves the running time performance of Sufferage without degrading its solution quality. The proposed algorithms are easy to implement and we illustrate them through detailed pseudocodes. The experimental results over a large number of real-life data sets show that the proposed fast MinMin algorithm and the proposed hybrid algorithms perform significantly better than their traditional counterparts as well as more recent state-of-the-art assignment heuristics. For the large data sets used in the experiments, MinMin, MaxMin, and Sufferage, as well as recent state-of-the-art heuristics, require days, weeks, or even months to produce a solution, whereas all of the proposed algorithms produce solutions within only two or three minutes

Fast-ignition design transport studies: realistic electron source, integrated PIC-hydrodynamics, imposed magnetic fields

Transport modeling of idealized, cone-guided fast ignition targets indicates the severe challenge posed by fast-electron source divergence. The hybrid particle-in-cell [PIC] code Zuma is run in tandem with the radiation-hydrodynamics code Hydra to model fast-electron propagation, fuel heating, and thermonuclear burn. The fast electron source is based on a 3D explicit-PIC laser-plasma simulation with the PSC code. This shows a quasi two-temperature energy spectrum, and a divergent angle spectrum (average velocity-space polar angle of 52 degrees). Transport simulations with the PIC-based divergence do not ignite for > 1 MJ of fast-electron energy, for a modest 70 micron standoff distance from fast-electron injection to the dense fuel. However, artificially collimating the source gives an ignition energy of 132 kJ. To mitigate the divergence, we consider imposed axial magnetic fields. Uniform fields ~50 MG are sufficient to recover the artificially collimated ignition energy. Experiments at the Omega laser facility have generated fields of this magnitude by imploding a capsule in seed fields of 50-100 kG. Such imploded fields are however more compressed in the transport region than in the laser absorption region. When fast electrons encounter increasing field strength, magnetic mirroring can reflect a substantial fraction of them and reduce coupling to the fuel. A hollow magnetic pipe, which peaks at a finite radius, is presented as one field configuration which circumvents mirroring.Comment: 16 pages, 17 figures, submitted to Phys. Plasma

Epidemiological studies on the relation between diet and COPD

Chronic Obstructive Pulmonary Disease (COPD) is an important cause of morbidity and mortality around the world. In the early 1990's several dietary factors were suggested to protect against COPD, based on proposed biological mechanisms and a small number of epidemiological studies. Antioxidants (e.g. vitamin C and E,β-carotene, flavonoids) and foods rich in antioxidants (e.g. fruits, vegetables, whole grains) may protect the airways against oxidant-mediated damage. Alcohol and n-3 fatty acids (mainly present in fish) are thought to have anti-inflammatory effects.To gain more insight into the relation between diet and COPD, we analysed data from two large-scale population-based epidemiological studies. Data from the Seven Countries Study (1960-1990) allowed us to study the relation longitudinally in an international setting. However, less sophisticated methods than available today were used to examine mainly ever-smoking middle-aged and older men. In the cross-sectional MORGEN-study (1993-1997), Dutch men and women (20-59 yr.) with a large variation in smoking habits were examined using modern, high-quality methods. All associations were adjusted for age, height (for pulmonary function only), gender, smoking, body mass index and total energy intake.In the 16 cohorts of the Seven Countries Study, we observed an inverse ecological association of 25-yr COPD mortality with baseline fruit and fish consumption. At the individual level, not energy-adjusted baseline fruit and vitamin E intake were inversely associated with 20-yr COPD mortality in men from three European countries. Alcohol consumption showed a U-shaped curve with 20-yr COPD mortality, with the lowest rate in light drinkers (&gt;1.4,≤30 g/day). This U-shaped curve was supported by cross-sectional data on alcohol and pulmonary function. In all three countries, men with intake of both fruits and vegetables above the median had a higher pulmonary function (FEV 1 or FEV 0.75 ) than those with a low intake of both foods. Finally, bread intake was positively associated with pulmonary function in the three countries.In participants of the MORGEN-study, intake of catechins, flavonols and flavones was positively associated with the FEV 1 and inversely associated with the prevalence of chronic cough and breathlessness. Catechin intake, not derived from tea, was independently associated with both the FEV 1 and all studied COPD symptoms. Flavonol and flavone intake, however, was independently associated with chronic cough only. At the food group level, solid fruit (=apples, pears), but not tea, intake was beneficially associated with COPD. Furthermore, we observed independent beneficial associations of a favourable intake of fruits and whole grains (above the median) and alcohol (1-30 g/day) with COPD. The 2578 subjects with a favourable intake of all three foods had a 139 ml higher FEV 1 and a lower prevalence of COPD symptoms (OR = 0.44) compared to those with unfavourable intakes of the three foods. This was also observed in never smokers.The studies described in this thesis mainly suggest a protective effect of a high intake of fruits and whole grains and of light alcohol consumption (up to 3 drinks/day) against COPD. Causality of the observed relations is supported by an apparently temporal relation and by plausible biological mechanisms. Smoking did not seem to explain our findings. Confounding by other health related lifestyle factors can, however, not be excluded. The observed effect of dietary factors was estimated to reduce COPD with 10 to 30% at the population level and is, if causal, certainly of public health relevance.</p

Work-related correlates of occupational sitting in a diverse sample of employees in Midwest metropolitan cities

The worksite serves as an ideal setting to reduce sedentary time. Yet little research has focused on occupational sitting, and few have considered factors beyond the personal or socio-demographic level. The current study i) examined variation in occupational sitting across different occupations, ii) explored whether worksite level factors (e.g., employer size, worksite supports and policies) may be associated with occupational sitting. Between 2012 and 2013, participants residing in four Missouri metropolitan areas were interviewed via telephone and provided information on socio-demographic characteristics, schedule flexibility, occupation, work related factors, and worksite supports and policies. Occupational sitting was self-reported (daily minutes spent sitting at work), and dichotomized. Occupation-stratified analyses were conducted to identify correlates of occupational sitting using multiple logistic regressions. A total of 1668 participants provided completed data. Those employed in business and office/administrative support spent more daily occupational sitting time (median 330 min) compared to service and blue collar employees (median 30 min). Few worksite supports and policies were sitting specific, yet factors such as having a full-time job, larger employer size, schedule flexibility, and stair prompt signage were associated with occupational sitting. For example, larger employer size was associated with higher occupational sitting in health care, education/professional, and service occupations. Work-related factors, worksite supports and policies are associated with occupational sitting. The pattern of association varies among different occupation groups. This exploratory work adds to the body of research on worksite level correlates of occupational sitting. This may provide information on priority venues for targeting highly sedentary occupation groups