Essential epidemiological mechanisms underpinning the transmission dynamics of seasonal influenza

Seasonal influenza has considerable impact around the world, both economically and in mortality among risk groups, but there is considerable uncertainty as to the essential mechanisms and their parametrization. In this paper, we identify a number of characteristic features of influenza incidence time series in temperate regions, including ranges of annual attack rates and outbreak durations. By constraining the output of simple models to match these characteristic features, we investigate the role played by population heterogeneity, multiple strains, cross-immunity and the rate of strain evolution in the generation of incidence time series. Results indicate that an age-structured model with non-random mixing and co-circulating strains are both required to match observed time-series data. Our work gives estimates of the seasonal peak basic reproduction number, R₀, in the range 1.6–3. Estimates of R₀ are strongly correlated with the timescale for waning of immunity to current circulating seasonal influenza strain, which we estimate is between 3 and 8 years. Seasonal variation in transmissibility is largely confined to 15–30% of its mean value. While population heterogeneity and cross-immunity are required mechanisms, the degree of heterogeneity and cross-immunity is not tightly constrained. We discuss our findings in the context of other work fitting to seasonal influenza data.     

Abstractions for DNA circuit design

DNA strand displacement techniques have been used to implement a broad range of information processing devices, from logic gates, to chemical reaction networks, to architectures for universal computation. Strand displacement techniques enable computational devices to be implemented in DNA without the need for additional components, allowing computation to be programmed solely in terms of nucleotide sequences. A major challenge in the design of strand displacement devices has been to enable rapid analysis of high-level designs while also supporting detailed simulations that include known forms of interference. Another challenge has been to design devices capable of sustaining precise reaction kinetics over long periods, without relying on complex experimental equipment to continually replenish depleted species over time. In this paper, we present a programming language for designing DNA strand displacement devices, which supports progressively increasing levels of molecular detail. The language allows device designs to be programmed using a common syntax and then analysed at varying levels of detail, with or without interference, without needing to modify the program. This allows a trade-off to be made between the level of molecular detail and the computational cost of analysis. We use the language to design a buffered architecture for DNA devices, capable of maintaining precise reaction kinetics for a potentially unbounded period. We test the effectiveness of buffered gates to support long-running computation by designing a DNA strand displacement system capable of sustained oscillations.     

Outbreaks of H5N1 in poultry in Thailand: the relative role of poultry production types in sustaining transmission and the impact of active surveillance in control

H5N1, highly pathogenic avian influenza, continues to pose a public health risk in the countries of southeast Asia where it has become endemic. However, in Thailand, which experienced two of the largest recorded epidemics in 2004–2005, the disease has been successfully reduced to very low levels. We fitted a spatio-temporal model of the spread of infection to outbreak data collected during the second wave of outbreaks to assess the extent to which different poultry types were responsible for propagating infection. Our estimates suggest that the wave of outbreaks would not have been possible without the contribution of backyard flocks to the susceptibility of a sub-district. However, we also estimated that outbreaks involving commercial poultry, a much larger sector in Thailand than in neighbouring countries, were disproportionately infectious, a factor which was also crucial in sustaining the wave. As a result, implemented measures that aim to reduce the role of commercial farms in the spread of infection, such as the drive to bring aspects of the supply chain ‘in house’, may help to explain the subsequent success in controlling H5N1 in Thailand. We also found that periods of active surveillance substantially improved the rate of outbreak detection.     

Tomographic imaging with polarized light

We report three-dimensional tomographic reconstruction of optical parameters for the mesoscopic light scattering regime from experimentally obtained datasets by using polarized light. We present a numerically inexpensive approximation to the radiative transfer equation governing the polarized light transport. This approximation is employed in the reconstruction algorithm, which computes two optical parameters by using parallel and perpendicular polarizations of transmitted light. Datasets were obtained by imaging a scattering phantom embedding highly absorbing inclusions. Reconstruction results are presented and discussed.     

释放阳光地带的光伏发电潜力

拥有非常丰富的太阳能辐射资源的阳光地带,人口占全球人口总数的75%,电力需求占全球总需求的40%,该地区经济发展受到能源和环境的制约,充分利用丰富的太阳能辐射资源开发光伏发电产业,是可持续发展的重要手段。预测结果表明,范式转型情景中,这些国家的光伏装机容量甚至可达1 100 GW,也就是该地域发电总量的12%;2020年阳光地带国家光伏系统的发电成本将比建设天然气和燃油电站更具竞争力;至2030年光伏发电可以与所有以煤和天然气为燃料的中负荷电厂竞争。阳光地带国家发展股份发电目前还面临着许多障碍,这些障碍涉及到政府对燃油价格的补贴、服务于市场的能力以及能源公司的知识有限等,这些障碍有待于在发展过程中不断克服。中国和印度是阳光地带中的大国,两国的光伏制造业对阳光地带的影响很大。新能源被锁定为中国十二五规划的七大战略性新兴产业之一,中国的十二.五规划的重心是重新平衡经济增长模式,包括逐步扩大内需;国内光伏市场一旦打开,光伏在中国的发展将会非常迅速。释放阳光地带光伏潜力要求众多利益相关者共同参与协作,包括政府、银行和金融机构以及各行各业的支持,才能充分释放阳光地带的光伏发电潜力,带动光伏发电产业链的发展,成为社会经济...     

Upscaling of the investment casting of the intermetallic alloy IC75

This research work is based on a specially developed SiO₂-free shell mold system for the investment casting of NiAl alloys. Hitherto, this shell system has only been used for scientific work on small, laboratory scale samples made of IC75 alloy. The main focus of the research is to examine the feasibility of upscaling of the shell mold system for production scale samples. For this reason, 200 mm long dummy turbine blades were cast. Nondestructive analysis of the castings by visual examination of the blades’ surface quality, computed tomography scans of their internal structures and three-dimensional measurements showed very good results for the shell mold system. In particular, the good dimensional stability of the shell mold with average deviations of +0.3 mm and a local maximum deviation of −0.73 mm are excellent for a water-soluble shell mold system. The results of this work demonstrate that the investigated mold system is suitable for large samples and melt weights of up to 5 kg and is thus adaptable for the production process of NiAl components.     

Numerical investigation of supercritical water-cooled nuclear reactor in horizontal rod bundles

The commercial CFD code STAR-CD v4.02 is used as a numerical simulation tool for flows in the supercritical water-cooled nuclear reactor (SCWR). The basic heat transfer element in the reactor core can be considered as round rods and rod bundles. Reactors with vertical or horizontal flow in the core can be found. In vertically oriented core, symmetric characters of flow and heat transfer can be found and two-dimensional analyses are often performed. However, in horizontally oriented core the flow and heat transfer are fully three-dimensional due to the buoyancy effect. In this paper, horizontal rods and rod bundles at SCWR conditions are studied. Special STAR-CD subroutines were developed by the authors to correctly represent the dramatic change in physical properties of the supercritical water with temperature. In the rod bundle simulations, it is found that the geometry and orientation of the rod bundle have strong effects on the wall temperature distributions and heat transfers. In one orientation the square bundle has a higher wall temperature difference than other bundles. However, when the bundles are rotated by 90° the highest wall temperature difference is found in the hexagon bundle. Similar analysis could be useful in design and safety studies to obtain optimum fuel rod arrangement in a SCWR.     

Psychological contract breaches, organizational commitment, and innovation-related behaviors: A latent growth modeling approach.

This study examined the relationships among psychological contract breaches, organizational commitment, and innovation-related behaviors (generating, spreading, implementing innovative ideas at work) over a 6-month period. Results indicate that the effects of psychological contract breaches on employees are not static. Specifically, perceptions of psychological contract breaches strengthened over time and were associated with decreased levels of affective commitment over time. Further, increased perceptions of psychological contract breaches were associated with decreases in innovation-related behaviors. We also found evidence that organizational commitment mediates the relationship between psychological contract breaches and innovation-related behaviors. These results highlight the importance of examining the nomological network of psychological contract breaches from a change perspective. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Peak of the Oil Age – Analyzing the world oil production Reference Scenario in World Energy Outlook 2008

The assessment of future global oil production presented in the IEA’s World Energy Outlook 2008 (WEO 2008) is divided into 6 fractions; four relate to crude oil, one to non-conventional oil, and the final fraction is natural-gas-liquids (NGL). Using the production parameter, depletion-rate-of-recoverable-resources, we have analyzed the four crude oil fractions and found that the 75 Mb/d of crude oil production forecast for year 2030 appears significantly overstated, and is more likely to be in the region of 55 Mb/d. Moreover, analysis of the other fractions strongly suggests lower than expected production levels. In total, our analysis points to a world oil supply in 2030 of 75 Mb/d, some 26 Mb/d lower than the IEA predicts.     

Adults' physical activity patterns across life domains: Cluster analysis with replication.

Objective: Identifying adults' physical activity patterns across multiple life domains could inform the design of interventions and policies. Design: Cluster analysis was conducted with adults in two U.S. regions (Baltimore/Washington, DC, n = 702; Seattle, WA [King County], n = 987) to identify different physical activity patterns based on adults' reported physical activity across four life domains: leisure, occupation, transport, and home. Objectively measured physical activity, and psychosocial and built (physical) environment characteristics of activity patterns were examined. Main Outcome Measures: Accelerometer-measured activity, reported domain-specific activity, psychosocial characteristics, built environment, body mass index. Results: Three clusters replicated (κ = .90–.93) across both regions: Low Activity, Active Leisure, and Active Job. The Low Activity and Active Leisure adults were demographically similar, but Active Leisure adults had the highest psychosocial and built environment support for activity, highest accelerometer-measured activity, and lowest body mass index. Compared to the other clusters, the Active Job cluster had lower socioeconomic status and intermediate accelerometer-measured activity. Conclusion: Adults can be clustered into groups based on their patterns of accumulating physical activity across life domains. Differences in psychosocial and built environment support between the identified clusters suggest that tailored interventions for different subgroups may be beneficial. (PsycINFO Database Record (c) 2010 APA, all rights reserved)