411 research outputs found
Concircular tensors in Spaces of Constant Curvature: With Applications to Orthogonal Separation of The Hamilton-Jacobi Equation
We study concircular tensors in spaces of constant curvature and then apply
the results obtained to the problem of the orthogonal separation of the
Hamilton-Jacobi equation on these spaces. Any coordinates which separate the
geodesic Hamilton-Jacobi equation are called separable. Specifically for spaces
of constant curvature, we obtain canonical forms of concircular tensors modulo
the action of the isometry group, we obtain the separable coordinates induced
by irreducible concircular tensors, and we obtain warped products adapted to
reducible concircular tensors. Using these results, we show how to enumerate
the isometrically inequivalent orthogonal separable coordinates, construct the
transformation from separable to Cartesian coordinates, and execute the
Benenti-Eisenhart-Kalnins-Miller (BEKM) separation algorithm for separating
natural Hamilton-Jacobi equations.Comment: Removed preamble and references to unpublished articles. Also made
some minor changes in the bod
Orthogonal Separation of the Hamilton-Jacobi Equation on Spaces of Constant Curvature
We review the theory of orthogonal separation of variables of the
Hamilton-Jacobi equation on spaces of constant curvature, highlighting key
contributions to the theory by Benenti. This theory revolves around a special
type of conformal Killing tensor, hereafter called a concircular tensor. First,
we show how to extend original results given by Benenti to intrinsically
characterize all (orthogonal) separable coordinates in spaces of constant
curvature using concircular tensors. This results in the construction of a
special class of separable coordinates known as Kalnins-Eisenhart-Miller
coordinates. Then we present the Benenti-Eisenhart-Kalnins-Miller separation
algorithm, which uses concircular tensors to intrinsically search for
Kalnins-Eisenhart-Miller coordinates which separate a given natural
Hamilton-Jacobi equation. As a new application of the theory, we show how to
obtain the separable coordinate systems in the two dimensional spaces of
constant curvature, Minkowski and (Anti-)de Sitter space. We also apply the
Benenti-Eisenhart-Kalnins-Miller separation algorithm to study the separability
of the three dimensional Calogero-Moser and Morosi-Tondo systems
Continuous synthesis of pyridocarbazoles and initial photophysical and bioprobe characterization
Pyridocarbazoles when ligated to transition metals yield high affinity kinase
inhibitors. While batch photocyclizations enable the synthesis of these
heterocycles, the non-oxidative Mallory reaction only provides modest yields
and difficult to purify mixtures. We demonstrate here that a flow-based
Mallory cyclization provides superior results and enables observation of a
clear isobestic point. The flow method allowed us to rapidly synthesize ten
pyridocarbazoles and for the first time to document their interesting
photophysical attributes. Preliminary characterization reveals that these
molecules might be a new class of fluorescent bioprobe
Jet-induced cratering of a granular surface with application to lunar spaceports
The erosion of lunar soil by rocket exhaust plumes is investigated
experimentally. This has identified the diffusion-driven flow in the bulk of
the sand as an important but previously unrecognized mechanism for erosion
dynamics. It has also shown that slow regime cratering is governed by the
recirculation of sand in the widening geometry of the crater. Scaling
relationships and erosion mechanisms have been characterized in detail for the
slow regime. The diffusion-driven flow occurs in both slow and fast regime
cratering. Because diffusion-driven flow had been omitted from the lunar
erosion theory and from the pressure cratering theory of the Apollo and Viking
era, those theories cannot be entirely correct.Comment: 13 pages, link to published version:
http://cedb.asce.org/cgi/WWWdisplay.cgi?090000
National and subnational mortality effects of metabolic risk factors and smoking in Iran: a comparative risk assessment
<p>Abstract</p> <p>Background</p> <p>Mortality from cardiovascular and other chronic diseases has increased in Iran. Our aim was to estimate the effects of smoking and high systolic blood pressure (SBP), fasting plasma glucose (FPG), total cholesterol (TC), and high body mass index (BMI) on mortality and life expectancy, nationally and subnationally, using representative data and comparable methods.</p> <p>Methods</p> <p>We used data from the Non-Communicable Disease Surveillance Survey to estimate means and standard deviations for the metabolic risk factors, nationally and by region. Lung cancer mortality was used to measure cumulative exposure to smoking. We used data from the death registration system to estimate age-, sex-, and disease-specific numbers of deaths in 2005, adjusted for incompleteness using demographic methods. We used systematic reviews and meta-analyses of epidemiologic studies to obtain the effect of risk factors on disease-specific mortality. We estimated deaths and life expectancy loss attributable to risk factors using the comparative risk assessment framework.</p> <p>Results</p> <p>In 2005, high SBP was responsible for 41,000 (95% uncertainty interval: 38,000, 44,000) deaths in men and 39,000 (36,000, 42,000) deaths in women in Iran. High FPG, BMI, and TC were responsible for about one-third to one-half of deaths attributable to SBP in men and/or women. Smoking was responsible for 9,000 deaths among men and 2,000 among women. If SBP were reduced to optimal levels, life expectancy at birth would increase by 3.2 years (2.6, 3.9) and 4.1 years (3.2, 4.9) in men and women, respectively; the life expectancy gains ranged from 1.1 to 1.8 years for TC, BMI, and FPG. SBP was also responsible for the largest number of deaths in every region, with age-standardized attributable mortality ranging from 257 to 333 deaths per 100,000 adults in different regions.</p> <p>Discussion</p> <p>Management of blood pressure through diet, lifestyle, and pharmacological interventions should be a priority in Iran. Interventions for other metabolic risk factors and smoking can also improve population health.</p
Chronotype and environmental light exposure in a student population
In humans and most other species, changes in the intensity and duration of light provide a critical set of signals for the synchronisation of the circadian system to the astronomical day. The timing of activity within the 24 h day defines an individual’s chronotype, i.e. morning, intermediate or evening type. The aim of this study was to investigate the associations between environmental light exposure, due to geographical location, on the chronotype of university students. Over 6 000 university students from cities in the Northern Hemisphere (Oxford, Munich and Groningen) and Southern Hemisphere (Perth, Melbourne and Auckland) completed the Munich ChronoType Questionnaire. In parallel, light measures (daily irradiance, timing of sunrise and sunset) were compiled from satellite or ground stations at each of these locations. Our data shows that later mid-sleep point on free days (corrected for oversleep on weekends MFSsc) is associated with (i) residing further from the equator, (ii) a later sunset, (iii) spending more time outside and (iv) waking from sleep significantly after sunrise. However, surprisingly, MSFscdid not correlate with daily light intensity at the different geographical locations. Although these findings appear to contradict earlier studies suggesting that in the wider population increased light exposure is associated with an earlier chronotype, our findings are derived exclusively from a student population aged between 17 and 26 years. We therefore suggest that the age and occupation of our population increase the likelihood that these individuals will experience relatively little light exposure in the morning whilst encountering more light exposure later in the day, when light has a delaying effect upon the circadian system
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