693 research outputs found
Einstein energy associated with the Friedmann -Robertson -Walker metric
Following Einstein's definition of Lagrangian density and gravitational field
energy density (Einstein, A., Ann. Phys. Lpz., 49, 806 (1916); Einstein, A.,
Phys. Z., 19, 115 (1918); Pauli, W., {\it Theory of Relativity}, B.I.
Publications, Mumbai, 1963, Trans. by G. Field), Tolman derived a general
formula for the total matter plus gravitational field energy () of an
arbitrary system (Tolman, R.C., Phys. Rev., 35(8), 875 (1930); Tolman, R.C.,
{\it Relativity, Thermodynamics & Cosmology}, Clarendon Press, Oxford, 1962));
Xulu, S.S., arXiv:hep-th/0308070 (2003)). For a static isolated system, in
quasi-Cartesian coordinates, this formula leads to the well known result , where is the
determinant of the metric tensor and is the energy momentum tensor of
the {\em matter}. Though in the literature, this is known as "Tolman Mass", it
must be realized that this is essentially "Einstein Mass" because the
underlying pseudo-tensor here is due to Einstein. In fact, Landau -Lifshitz
obtained the same expression for the "inertial mass" of a static isolated
system without using any pseudo-tensor at all and which points to physical
significance and correctness of Einstein Mass (Landau, L.D., and Lifshitz,
E.M., {\it The Classical Theory of Fields}, Pergamon Press, Oxford, 2th ed.,
1962)! For the first time we apply this general formula to find an expression
for for the Friedmann- Robertson -Walker (FRW) metric by using the same
quasi-Cartesian basis. As we analyze this new result, physically, a spatially
flat model having no cosmological constant is suggested. Eventually, it is seen
that conservation of is honoured only in the a static limit.Comment: By mistake a marginally different earlier version was loaded, now the
journal version is uploade
Pain outcomes in patients with bone metastases from advanced cancer: assessment and management with bone-targeting agents
Bone metastases in advanced cancer frequently cause painful complications that impair patient physical activity and negatively affect quality of life. Pain is often underreported and poorly managed in these patients. The most commonly used pain assessment instruments are visual analogue scales, a single-item measure, and the Brief Pain Inventory Questionnaire-Short Form. The World Health Organization analgesic ladder and the Analgesic Quantification Algorithm are used to evaluate analgesic use. Bone-targeting agents, such as denosumab or bisphosphonates, prevent skeletal complications (i.e., radiation to bone, pathologic fractures, surgery to bone, and spinal cord compression) and can also improve pain outcomes in patients with metastatic bone disease. We have reviewed pain outcomes and analgesic use and reported pain data from an integrated analysis of randomized controlled studies of denosumab versus the bisphosphonate zoledronic acid (ZA) in patients with bone metastases from advanced solid tumors. Intravenous bisphosphonates improved pain outcomes in patients with bone metastases from solid tumors. Compared with ZA, denosumab further prevented pain worsening and delayed the need for treatment with strong opioids. In patients with no or mild pain at baseline, denosumab reduced the risk of increasing pain severity and delayed pain worsening along with the time to increased pain interference compared with ZA, suggesting that use of denosumab (with appropriate calcium and vitamin D supplementation) before patients develop bone pain may improve outcomes. These data also support the use of validated pain assessments to optimize treatment and reduce the burden of pain associated with metastatic bone disease
Massive gravity from bimetric gravity
We discuss the subtle relationship between massive gravity and bimetric
gravity, focusing particularly on the manner in which massive gravity may be
viewed as a suitable limit of bimetric gravity. The limiting procedure is more
delicate than currently appreciated. Specifically, this limiting procedure
should not unnecessarily constrain the background metric, which must be
externally specified by the theory of massive gravity itself. The fact that in
bimetric theories one always has two sets of metric equations of motion
continues to have an effect even in the massive gravity limit, leading to
additional constraints besides the one set of equations of motion naively
expected. Thus, since solutions of bimetric gravity in the limit of vanishing
kinetic term are also solutions of massive gravity, but the contrary statement
is not necessarily true, there is not complete continuity in the parameter
space of the theory. In particular, we study the massive cosmological solutions
which are continuous in the parameter space, showing that many interesting
cosmologies belong to this class.Comment: v1: 25 pages; v2: 6 references added, discussion streamlined; v3: 24
pages, 20 references added, section 2 summarized, new comments added to
section 3, conclusions improved but unchanged. This version accepted for
publication in Classical and Quantum Gravit
The Impact of Railway Stations on Residential and Commercial Property Value: A Meta-analysis
Railway stations function as nodes in transport networks and places in an urban environment. They have accessibility and environmental impacts, which contribute to property value. The literature on the effects of railway stations on property value is mixed in its finding in respect to the impact magnitude and direction, ranging from a negative to an insignificant or a positive impact. This paper attempts to explain the variation in the findings by meta-analytical procedures. Generally the variations are attributed to the nature of data, particular spatial characteristics, temporal effects and methodology. Railway station proximity is addressed from two spatial considerations: a local station effect measuring the effect for properties with in 1/4 mile range and a global station effect measuring the effect of coming 250 m closer to the station. We find that the effect of railway stations on commercial property value mainly takes place at short distances. Commercial properties within 1/4 mile rang are 12.2% more expensive than residential properties. Where the price gap between the railway station zone and the rest is about 4.2% for the average residence, it is about 16.4% for the average commercial property. At longer distances the effect on residential property values dominate. We find that for every 250 m a residence is located closer to a station its price is 2.3% higher than commercial properties. Commuter railway stations have a consistently higher positive impact on the property value compared to light and heavy railway/Metro stations. The inclusion of other accessibility variables (such as highways) in the models reduces the level of reported railway station impact. © 2007 Springer Science+Business Media, LLC
On Consistent Theories of Massive Spin-2 Fields Coupled to Gravity
We consider the issues that arise out of interpreting the ghost-free bimetric
theory as a theory of a spin-2 field coupled to gravity. This requires
identifying a gravitational metric and parameterizing deviations of the
resulting theory from general relativity. To this end, we first consider the
most general bimetric backgrounds for which a massless and a massive spin-2
fluctuation with Fierz-Pauli mass exist. These backgrounds coincide with
solutions in general relativity. Based on this, we obtain nonlinear extensions
of the massive and massless spin-2 fields. The background value of the
nonlinear massive field parameterizes generic deviations of the bimetric theory
from GR. It is also shown that the nonlinear massless field does not have
standard ghost-free matter couplings, and hence cannot represent the
gravitational metric. However, an appropriate gravitational metric can still be
identified in the weak gravity limit. Hence in the presence of other neutral
spin-2 fields, the weak gravity limit is crucial for compatibility with general
relativity. We also write down the action in terms of the nonlinear massive
spin-2 field and obtain its ghost-free couplings to matter. The discussion is
then generalized to multimetric theories.Comment: Latex, 31 page
Attitudes toward integrative paediatrics: a national survey among youth health are physicians in the Netherlands
<p>Abstract</p> <p>Background</p> <p>Integrative Medicine (IM) is an emerging field in paediatrics, especially in the USA. The purpose of the present study was to assess the attitudes and beliefs of Youth Health Care (YHC) physicians in the Netherlands toward IM in paediatrics.</p> <p>Methods</p> <p>In October 2010, a link to an anonymous, self-reporting, 30-item web-based questionnaire was mailed to all members of the Dutch Organisation of YHC physicians. The questionnaire included questions on familiarity with IM, attitudes towards Integrative Paediatrics (IP), use and knowledge of Complementary and Alternative Medicine (CAM), demographic and practice characteristics.</p> <p>Results</p> <p>A total of 276 YHC physicians (response rate of 27%) responded to the survey. Of the respondents, 52% was familiar with IM and 56% had used some kind of CAM therapy during the past 2 years, of which self-medicated herbal and/or homeopathic remedies (61%) and supplements (50%) were most frequently mentioned. Most of the YHC physicians (62%) seldom asked parents of clients about CAM use. One third of the YHC physicians recommended CAM to their clients. In general, about 50% or more of the respondents had little knowledge of CAM therapies. Predictors for a positive attitude towards IP were familiarity with IM, own CAM use, asking their clients about CAM use and practising one or more forms of CAM therapy. Logistic regression analysis showed that the following factors were associated with a higher recommendation to CAM therapies: own CAM use (odds ratio (OR) = 3.8; 95% confidence interval (CI) = 2.1-6.9, <it>p </it>= 0.001) and practising CAM (OR 4.4; 95% CI = 1.6-11.7, <it>p </it>= 0.003).</p> <p>Conclusions</p> <p>In general Dutch YHC physicians have a relative positive attitude towards IP; more than half of the respondents used one or more forms of CAM and one third recommended CAM therapies. However, the majority of YHC physicians did not ask their clients about CAM use and seemed to have a lack of knowledge regarding CAM.</p
The utilisation of health research in policy-making: Concepts, examples and methods of assessment
The importance of health research utilisation in policy-making, and of understanding the
mechanisms involved, is increasingly recognised. Recent reports calling for more resources to
improve health in developing countries, and global pressures for accountability, draw greater
attention to research-informed policy-making. Key utilisation issues have been described for at
least twenty years, but the growing focus on health research systems creates additional dimensions.
The utilisation of health research in policy-making should contribute to policies that may eventually
lead to desired outcomes, including health gains. In this article, exploration of these issues is
combined with a review of various forms of policy-making. When this is linked to analysis of
different types of health research, it assists in building a comprehensive account of the diverse
meanings of research utilisation.
Previous studies report methods and conceptual frameworks that have been applied, if with varying
degrees of success, to record utilisation in policy-making. These studies reveal various examples of
research impact within a general picture of underutilisation.
Factors potentially enhancing utilisation can be identified by exploration of: priority setting;
activities of the health research system at the interface between research and policy-making; and
the role of the recipients, or 'receptors', of health research. An interfaces and receptors model
provides a framework for analysis.
Recommendations about possible methods for assessing health research utilisation follow
identification of the purposes of such assessments. Our conclusion is that research utilisation can
be better understood, and enhanced, by developing assessment methods informed by conceptual
analysis and review of previous studies
Control of star formation by supersonic turbulence
Understanding the formation of stars in galaxies is central to much of modern
astrophysics. For several decades it has been thought that stellar birth is
primarily controlled by the interplay between gravity and magnetostatic
support, modulated by ambipolar diffusion. Recently, however, both
observational and numerical work has begun to suggest that support by
supersonic turbulence rather than magnetic fields controls star formation. In
this review we outline a new theory of star formation relying on the control by
turbulence. We demonstrate that although supersonic turbulence can provide
global support, it nevertheless produces density enhancements that allow local
collapse. Inefficient, isolated star formation is a hallmark of turbulent
support, while efficient, clustered star formation occurs in its absence. The
consequences of this theory are then explored for both local star formation and
galactic scale star formation. (ABSTRACT ABBREVIATED)Comment: Invited review for "Reviews of Modern Physics", 87 pages including 28
figures, in pres
Affine Gravity, Palatini Formalism and Charges
Affine gravity and the Palatini formalism contribute both to produce a simple
and unique formula for calculating charges at spatial and null infinity for
Lovelock type Lagrangians whose variational derivatives do not depend on
second-order derivatives of the field components. The method is based on the
covariant generalization due to Julia and Silva of the Regge-Teitelboim
procedure that was used to define properly the mass in the classical
formulation of Einstein's theory of gravity. Numerous applications reproduce
standard results obtained by other secure but mostly specialized methods. As a
novel application we calculate the Bondi energy loss in five dimensional
gravity, based on the asymptotic solution given by Tanabe, Tanahashi and
Shiromizu, and obtain, as expected, the same result. We also give the
superpotential for Einstein-Gauss-Bonnet gravity and find the superpotential
for Lovelock theories of gravity when the number of dimensions tends to
infinity with maximally symmetrical boundaries. The paper is written in
standard component formalism.Comment: The work is dedicated to Joshua Goldberg from whom I learned and got
interested in conservation laws in General Relativity (J.K
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