False-vacuum decay in generalized extended inflation

False-vacuum decay was studied in context of generalized extended inflationary theories, and the bubble nucleation rates was computed for these theories in the limit of G(sub N) yields 0. It was found that the time dependence of the nucleation rate can be exponentially strong through the time dependence of the Jordan-Brans-Dicke field. This can have a pronounced effect on whether extended inflation can be successfully implemented

Extended inflation from higher dimensional theories

The possibility is considered that higher dimensional theories may, upon reduction to four dimensions, allow extended inflation to occur. Two separate models are analayzed. One is a very simple toy model consisting of higher dimensional gravity coupled to a scalar field whose potential allows for a first-order phase transition. The other is a more sophisticated model incorporating the effects of non-trivial field configurations (monopole, Casimir, and fermion bilinear condensate effects) that yield a non-trivial potential for the radius of the internal space. It was found that extended inflation does not occur in these models. It was also found that the bubble nucleation rate in these theories is time dependent unlike the case in the original version of extended inflation

Statistical mechanics of soft-boson phase transitions

The existence of structure on large (100 Mpc) scales, and limits to anisotropies in the cosmic microwave background radiation (CMBR), have imperiled models of structure formation based solely upon the standard cold dark matter scenario. Novel scenarios, which may be compatible with large scale structure and small CMBR anisotropies, invoke nonlinear fluctuations in the density appearing after recombination, accomplished via the use of late time phase transitions involving ultralow mass scalar bosons. Herein, the statistical mechanics are studied of such phase transitions in several models involving naturally ultralow mass pseudo-Nambu-Goldstone bosons (pNGB's). These models can exhibit several interesting effects at high temperature, which is believed to be the most general possibilities for pNGB's

On the Search for the Amino Acids on the Lunar Surface as it Relates to Other Extraterrestrial Bodies

The early search for the amino acids on the lunar surface fines indicated such a low amount of the amino acids that it was deemed insignifi cant. While the later studies seemed to depart in some ways from the earlier results, they were not pursued. In this paper we critically ev aluate the results from the Apollo missions from the new perspective with considerations of the sensitivity of the instrumentation availabl e at the time. We discuss the possible relevance of the lunar results to the findings of the amino acids on the surfaces of other extraterrestrial bodies, such as Mars

False vacuum decay in Jordan-Brans-Dicke cosmologies

The bubble nucleation rate in a first-order phase transition taking place in a background Jordan-Brans-Dicke cosmology is examined. The leading order terms in the nucleation rate when the Jordan-Brans-Dicke field is large (i.e., late times) are computed by means of a Weyl rescaling of the fields in the theory. It is found that despite the fact that the Jordan-Brans-Dicke field (hence the effective gravitational constant) has a time dependence in the false vacuum at late times the nucleation rate is time independent

Is sunlight good for our heart?

Humans evolved being exposed for about half of the day to the light of the sun. Nowadays, exposure to sunlight is actively discouraged for fear of skin cancer, and contemporary lifestyles are associated with long hours spent under artificial light indoors. Besides an increasing appreciation for the adverse effects of these life-style-related behavioural changes on our chronobiology, the balance between the beneficial and harmful effects of sunlight on human health is the subject of considerable debate, in both the scientific and popular press, and the latter is of major public health significance. While there is incontrovertible evidence that ultraviolet radiation (UVR) in the form of sunlight is a significant predisposing factor for non-melanoma and melanoma skin cancers in pale skinned people,1 a growing body of data suggest general health benefits brought about by sunlight.2 These are believed to be mediated either by melatonin or vitamin D. Melatonin is produced from serotonin by the pineal gland located in the centre of the brain during periods of darkness, and its release is suppressed as a function of the visible light intensity sensed through ocular photoreceptors. Vitamin D is formed by ultraviolet B (UVB)-mediated photolysis of 7-dehydrocholesterol in the skin. Both melatonin and vitamin D are pleiotropic hormones that exert a multitude of cellular effects by interacting with membrane and nuclear receptors, and receptor-independent actions. People with more heavily pigmented skin require higher doses of UVB to produce adequate amounts of vitamin D, and this may have been an evolutionary driver to the variation of human skin colour with latitude and intensity of solar irradiation. Our degree of exposure to sunlight is easily modified by behavioural factors such as the use of clothing, sunglasses, and sun-blocking creams, and time spent outdoors. Balancing the carcinogenic risks with the requirement for vitamin D has led to advice on moderating sun exposure, while supplementing food with vitamin D. Guidance on such behaviour is part of the public health campaigns in most countries with Caucasian populations. Following these suggestions, we may, however, be missing out on other health benefits provided by natural sunlight that are less obvious and unrelated to the above classical mediators

Neutrinos and Future Concordance Cosmologies

We review the free parameters in the concordance cosmology, and those which might be added to this set as the quality of astrophysical data improves. Most concordance parameters encode information about otherwise unexplored aspects of high energy physics, up to the GUT scale via the "inflationary sector," and possibly even the Planck scale in the case of dark energy. We explain how neutrino properties may be constrained by future astrophysical measurements. Conversely, future neutrino physics experiments which directly measure these parameters will remove uncertainty from fits to astrophysical data, and improve our ability to determine the global properties of our universe.Comment: Proceedings of paper given at Neutrino 2008 meeting (by RE

Nurturing environments and nutrient-rich diets may improve cognitive development: analysis of cognitive trajectories from six to sixty months from the MAL-ED study (OR10-01-19)

Objectives: To identify clusters of cognitive developmental trajectories and associated differentiating factors of children aged 6 to 60 months old in 5 low to middle-income sites.Methods: We followed 835 children and assessed anthropometry at enrolment (≤ 17 d old); bi-weekly illness data (0–24 and 60 mo); non-diarrheal and diarrheal stools (0–24 mo) analyzed for a panel of enteropathogens; quantitative complementary food intakes (9–24 and 60 mo); micronutrient status (Fe, Zn, Vit A; 7, 15, and 24 mo); quality of the child\u27s home environment (6, 24, and 60 mo) and maternal reasoning ability and depressive symptoms via questionnaire. Child cognitive development was assessed by the Bayley Scales of Infant Development III (6, 15 and 24 mo) and Wechsler Preschool and Primary Scale of Intelligence (60 mo). Clusters of trajectories were identified using a latent class mixed model. Differences between clusters were described using discriminant analysis to rank the contribution of each variable using correlation-adjusted t-scores (CAT).Results: Five clusters were identified. From 51 discriminatory factors, 10 had greatest descriptive power: HOME score at 60 mo (mean CAT2 ± SD: 34.6 ± 0.35), proportion of days ill from 0–24 mo (23.9 ± 0.18), years of maternal schooling (13.8 ± 0.23), mean nutrient densities of zinc (12.3 ± 0.07), protein (8.95 ± 0.09), vitamin B6 (8.2 ± 0.10), phytate (7.91 ± 0.05) and mean energy (7.82 ± 0.04) from complementary foods (9–24 mo), % days of exclusive breastfeeding (0–6 mo; 6.42 ± 0.10) and weight-for-age at enrolment (6.14 ± 0.17). The discriminant analysis model fit was statistically significant (Wilk\u27s λ 0.54, P \u3c 0.01).Conclusions: Early life factors associated with higher scoring trajectories included stimulation and support for the child in their home, complementary feeding that typified greater diversity and animal-source foods, and maternal years of schooling. Influences associated with lower scoring trajectories included lower weight at enrolment and higher prevalence of illness. Policies promoting maternal and child nutrition, education and fostering a nurturing environment are likely to have greatest impact on child development

Screening analysis of solar thermochemical hydrogen concepts.

A screening analysis was performed to identify concentrating solar power (CSP) concepts that produce hydrogen with the highest efficiency. Several CSP concepts were identified that have the potential to be much more efficient than today's low-temperature electrolysis technology. They combine a central receiver or dish with either a thermochemical cycle or high-temperature electrolyzer that operate at temperatures >600 C. The solar-to-hydrogen efficiencies of the best central receiver concepts exceed 20%, significantly better than the 14% value predicted for low-temperature electrolysis