281 research outputs found
Cauchy Horizons, Thermodynamics and Closed Time-like Curves in Planar Supersymmetric Space-times
We study geodesically complete, singularity free space-times induced by
supersymmetric planar domain walls interpolating between Minkowski and anti-de
Sitter () vacua. A geodesically complete space-time without closed
time-like curves includes an infinite number of semi-infinite Minkowski
space-times, separated from each other by a region of space-time. These
space-times are closely related to the extreme Reissner Nordstr\" om (RN) black
hole, exhibiting Cauchy horizons with zero Hawking temperature, but in contrast
to the RN black hole there is no entropy. Another geodesically complete
extension with closed time-like curves involves space-times connecting a finite
number of semi-infinite Minkowski space-times.Comment: 11 pages, 1 figure appended, phyzz
Gerontological research in China: The role of anthropological inquiry
One fifth of the world's elderly population lives in China. Until recently political restrictions have hindered the conduct of research particularly ethnography. This piece provides an overview of recent research findings by Western scholars and of ethnographic research in progress in the areas of demography, state policy, age stratification, family planning, residence patterns, inter-generational transfers, patrilineality, health, illness, long term care, social welfare, and mortuary ritual. It analyzes the potential contributions of ethnography in this area.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42988/1/10823_2004_Article_BF00119706.pd
Dark matter and structure formation a review
This paper provides a review of the variants of dark matter which are thought
to be fundamental components of the universe and their role in origin and
evolution of structures and some new original results concerning improvements
to the spherical collapse model. In particular, I show how the spherical
collapse model is modified when we take into account dynamical friction and
tidal torques
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Basic Research Needs for Geosciences: Facilitating 21st Century Energy Systems
To identify research areas in geosciences, such as behavior of multiphase fluid-solid systems on a variety of scales, chemical migration processes in geologic media, characterization of geologic systems, and modeling and simulation of geologic systems, needed for improved energy systems
Symptoms of Anxiety and Cardiac Hospitalizations at 12 Months in Patients with Heart Failure
OBJECTIVE: Heart failure (HF) is a leading cause of hospitalization. Clinical and socio-demographic factors have been associated with cardiac admissions, but little is known about the role of anxiety. We examined whether symptoms of anxiety were associated with cardiac hospitalizations at 12 months in HF patients. METHODS: HF outpatients (N=237) completed the Hospital Anxiety and Depression Scale (HADS) at baseline (i.e., inclusion into the study). A cutoff ≥8 was used to indicate probable clinical levels of anxiety and depression. At 12 months, a medical chart abstraction was performed to obtain information on cardiac hospitalizations. RESULTS: The prevalence of symptoms of anxiety was 24.9 % (59/237), and 27.0 % (64/237) of patients were admitted for cardiac reasons at least once during the 12-month follow-up period. Symptoms of anxiety were neither significantly associated with cardiac hospitalizations in univariable logistic analysis [OR=1.13, 95% CI (0.59–2.17), p=0.72] nor in multivariable analysi
Metabolic Rift or Metabolic Shift? Dialectics, Nature, and the World-Historical Method
Abstract In the flowering of Red-Green Thought over the past two decades, metabolic rift thinking is surely one of its most colorful varieties. The metabolic rift has captured the imagination of critical environmental scholars, becoming a shorthand for capitalism’s troubled relations in the web of life. This article pursues an entwined critique and reconstruction: of metabolic rift thinking and the possibilities for a post-Cartesian perspective on historical change, the world-ecology conversation. Far from dismissing metabolic rift thinking, my intention is to affirm its dialectical core. At stake is not merely the mode of explanation within environmental sociology. The impasse of metabolic rift thinking is suggestive of wider problems across the environmental social sciences, now confronted by a double challenge. One of course is the widespread—and reasonable—sense of urgency to evolve modes of thought appropriate to an era of deepening biospheric instability. The second is the widely recognized—but inadequately internalized—understanding that humans are part of nature
FACTS AND IDEAS IN MODERN COSMOLOGY
A review of the principles of observational testing of cosmological theories
is given with a special emphasis on the distinction between observational facts
and theoretical hypotheses. A classification of modern cosmological theories
and possible observational tests for these theories is presented. The main
rival cosmological models are analyzed from the point of view of observational
testing of their initial hypothesis. A comparison of modern observational data
with theoretical predictions is presented. In particular we discuss in detail
the validity of the two basic assumptions of modern cosmology that are the
Cosmological Principle and the Expanding Space Paradigm. It is found that
classical paradigms need to be reanalyzed and that it is necessary to develop
crucial cosmological tests to discriminate alternative theories.Comment: 84 pages, latex, figures are available to F.S.L
([email protected]). Accepted for publication in Vistas In astronomy,
Vol.38, Part.4, 199
Nanostructural characterization of amorphous diamondlike carbon films
Nanostructural characterization of amorphous diamondlike carbon (a-C) films grown on silicon using pulsed-laser deposition (PLD) is correlated to both growth energetic and film thickness. Raman spectroscopy and x-ray reflectivity probe both the topological nature of 3- and 4-fold coordinated carbon atom bonding and the topographical clustering of their distributions within a given film. In general, increasing the energetic of PLD growth results in films becoming more ``diamondlike'', i.e. increasing mass density and decreasing optical absorbance. However, these same properties decrease appreciably with thickness. The topology of carbon atom bonding is different for material near the substrate interface compared to material within the bulk portion of an a-C film. A simple model balancing the energy of residual stress and the free energies of resulting carbon topologies is proposed to provide an explanation of the evolution of topographical bonding clusters in a growing a-C film
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