13,092 research outputs found

    Late time cosmological phase transitions 1: Particle physics models and cosmic evolution

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    We described a natural particle physics basis for late-time phase transitions in the universe. Such a transition can seed the formation of large-scale structure while leaving a minimal imprint upon the microwave background anisotropy. The key ingredient is an ultra-light pseudo-Nambu-Goldstone boson with an astronomically large (O(kpc-Mpc)) Compton wavelength. We analyze the cosmological signatures of and constraints upon a wide class of scenarios which do not involve domain walls. In addition to seeding structure, coherent ultra-light bosons may also provide unclustered dark matter in a spatially flat universe, omega sub phi approx. = 1

    Politics of innovation and development: The role of industry associations in integrating political, bureaucratic, industrial and health systems in India and South Africa

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    Integrating political, bureaucratic, industrial and healthcare systems has been a major challenge for politics of innovation and development policy in low- and middle-income countries. This challenge has so far been understood in terms of separate industrial and health-related innovation policies without paying adequate attention to the institutional roles of biopharmaceutical and other umbrella associations. This article seeks to examine such roles in the developmental contexts of South Africa and India. The argument put forward is that, in both countries, biopharmaceutical and umbrella associations have evolved from lobbying organizations to institutional partners who influence the politics of innovation and development—and therefore the degree of integration and fragmentation—of political, bureaucratic, industrial innovation and health systems

    Si3AlP: A new promising material for solar cell absorber

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    First-principles calculations are performed to study the structural and optoelectronic properties of the newly synthesized nonisovalent and lattice-matched (Si2)0.6(AlP)0.4 alloy [T. Watkins et al., J. Am. Chem. Soc. 2011, 133, 16212.] We find that the ordered CC-Si3AlP with a basic unit of one P atom surrounded by three Si atoms and one Al atom is the most stable one within the experimentally observed unit cell.1 Si3AlP has a larger fundamental band gap and a smaller direct band gap than Si, thus it has much higher absorption in the visible light region. The calculated properties of Si3AlP suggest that it is a promising candidate for improving the performance of the existing Si-based solar cells. The understanding on the stability and band structure engineering obtained in this study is general and can be applied for future study of other nonisovalent and lattice-matched semiconductor alloys

    Minor degree of hypohydration adversely influences cognition: a mediator analysis

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    Background: The assumption that small changes in hydration statusare readily compensated by homeostatic mechanisms has been littlestudied. In this study, the influence of hypohydration on cognition wasexamined.Objectives: We assessed whether a loss of ,1% of body mass dueto hypohydration adversely influenced cognition, and examined thepossible underlying mechanisms.Design: A total of 101 individuals were subjected to a temperature of308C for 4 h and randomly either did or did not consume 300 mLH2O during that period. Changes in body mass, urine osmolality,body temperature, and thirst were monitored. Episodic memory, focusedattention, mood, and the perceived difficulty of tasks weremeasured on 3 occasions. The data were analyzed with the use ofa regression-based approach whereby we looked for variables that mediatedthe influence of hypohydration on psychological functioning.Results: Drinking water improved memory and focused attention.In the short-term, thirst was associated with poorer memory. Later,a greater loss of body mass was associated with poorer memory andattention (mean loss: 0.72%). At 90 min, an increase in thirst wasassociated with a decline in subjective energy and increased anxietyand depression, effects that were reduced by drinking water. At180 min, subjects found the tests easier if they had consumed water.Conclusions: Drinking water was shown, for the first time to ourknowledge, to benefit cognitive functioning when there was a lossof ,1% body mass at levels that may occur during everydayliving. Establishing the variables that generate optimal fluid consumptionwill help to tailor individual advice, particularly in clinicalsituations
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