4,524 research outputs found
Ideal Gas in a strong Gravitational field: Area dependence of Entropy
We study the thermodynamic parameters like entropy, energy etc. of a box of
gas made up of indistinguishable particles when the box is kept in various
static background spacetimes having a horizon. We compute the thermodynamic
variables using both statistical mechanics as well as by solving the
hydrodynamical equations for the system. When the box is far away from the
horizon, the entropy of the gas depends on the volume of the box except for
small corrections due to background geometry. As the box is moved closer to the
horizon with one (leading) edge of the box at about Planck length (L_p) away
from the horizon, the entropy shows an area dependence rather than a volume
dependence. More precisely, it depends on a small volume A*L_p/2 of the box,
upto an order O(L_p/K)^2 where A is the transverse area of the box and K is the
(proper) longitudinal size of the box related to the distance between leading
and trailing edge in the vertical direction (i.e in the direction of the
gravitational field). Thus the contribution to the entropy comes from only a
fraction O(L_p/K) of the matter degrees of freedom and the rest are suppressed
when the box approaches the horizon. Near the horizon all the thermodynamical
quantities behave as though the box of gas has a volume A*L_p/2 and is kept in
a Minkowski spacetime. These effects are: (i) purely kinematic in their origin
and are independent of the spacetime curvature (in the sense that Rindler
approximation of the metric near the horizon can reproduce the results) and
(ii) observer dependent. When the equilibrium temperature of the gas is taken
to be equal to the the horizon temperature, we get the familiar A/L_p^2
dependence in the expression for entropy. All these results hold in a D+1
dimensional spherically symmetric spacetime.Comment: 19 pages, added some discussion, matches published versio
Frequency and Circadian Timing of Eating May Influence Biomarkers of Inflammation and Insulin Resistance Associated with Breast Cancer Risk.
Emerging evidence suggests that there is interplay between the frequency and circadian timing of eating and metabolic health. We examined the associations of eating frequency and timing with metabolic and inflammatory biomarkers putatively associated with breast cancer risk in women participating in the National Health and Nutrition Examination 2009-2010 Survey. Eating frequency and timing variables were calculated from 24-hour food records and included (1) proportion of calories consumed in the evening (5 pm-midnight), (2) number of eating episodes per day, and (3) nighttime fasting duration. Linear regression models examined each eating frequency and timing exposure variable with C-reactive protein (CRP) concentrations and the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR). Each 10 percent increase in the proportion of calories consumed in the evening was associated with a 3 percent increase in CRP. Conversely, eating one additional meal or snack per day was associated with an 8 percent reduction in CRP. There was a significant interaction between proportion of calories consumed in the evening and fasting duration with CRP (p = 0.02). A longer nighttime fasting duration was associated with an 8 percent lower CRP only among women who ate less than 30% of their total daily calories in the evening (p = 0.01). None of the eating frequency and timing variables were significantly associated with HOMA-IR. These findings suggest that eating more frequently, reducing evening energy intake, and fasting for longer nightly intervals may lower systemic inflammation and subsequently reduce breast cancer risk. Randomized trials are needed to validate these associations
The masked cognate translation priming effect for different-script bilinguals is modulated by the phonological similarity of cognate words: Further support for the phonological account
The effect of phonological similarity on L1-L2 cognate translation priming was examined with Japanese-English bilinguals. According to the phonological account, the cognate priming effect for different-script bilinguals consists of additive effects of phonological and conceptual facilitation. If true, then the size of the cognate priming effect would be directly influenced by the phonological similarity of cognate translation equivalents. The present experiment tested and confirmed this prediction: the cognate priming effect was significantly larger for cognate prime-target pairs with high-phonological similarity than pairs with low-phonological similarity. Implications for the nature of lexical processing in same-versus different-script bilinguals are discussed
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Effects of Process Variables and Size Scale on Solidification Microstructure in Laser-Based Solid Freeform Fabrication of Ti-6Al-4V
Mechanical Engineerin
Formalism for obtaining nuclear momentum distributions by the Deep Inelastic Neutron Scattering technique
We present a new formalism to obtain momentum distributions in condensed
matter from Neutron Compton Profiles measured by the Deep Inelastic Neutron
Scattering technique. The formalism describes exactly the Neutron Compton
Profiles as an integral in the momentum variable . As a result we obtain a
Volterra equation of the first kind that relates the experimentally measured
magnitude with the momentum distributions of the nuclei in the sample. The
integration kernel is related with the incident neutron spectrum, the total
cross section of the filter analyzer and the detectors efficiency function. A
comparison of the present formalism with the customarily employed approximation
based on a convolution of the momentum distribution with a resolution function
is presented. We describe the inaccuracies that the use of this approximation
produces, and propose a new data treatment procedure based on the present
formalism.Comment: 11 pages, 8 figure
Loss of redundant gene expression after polyploidization in plants
Based on chromosomal location data of genes encoding 28 biochemical systems in allohexaploid wheat,Triticum aestivum L. (genomes AABBDD), it is concluded that the proportions of systems controlled by triplicate, duplicate, and single loci are 57%, 25%, and 18% respectively
Using state space differential geometry for nonlinear blind source separation
Given a time series of multicomponent measurements of an evolving stimulus,
nonlinear blind source separation (BSS) seeks to find a "source" time series,
comprised of statistically independent combinations of the measured components.
In this paper, we seek a source time series with local velocity cross
correlations that vanish everywhere in stimulus state space. However, in an
earlier paper the local velocity correlation matrix was shown to constitute a
metric on state space. Therefore, nonlinear BSS maps onto a problem of
differential geometry: given the metric observed in the measurement coordinate
system, find another coordinate system in which the metric is diagonal
everywhere. We show how to determine if the observed data are separable in this
way, and, if they are, we show how to construct the required transformation to
the source coordinate system, which is essentially unique except for an unknown
rotation that can be found by applying the methods of linear BSS. Thus, the
proposed technique solves nonlinear BSS in many situations or, at least,
reduces it to linear BSS, without the use of probabilistic, parametric, or
iterative procedures. This paper also describes a generalization of this
methodology that performs nonlinear independent subspace separation. In every
case, the resulting decomposition of the observed data is an intrinsic property
of the stimulus' evolution in the sense that it does not depend on the way the
observer chooses to view it (e.g., the choice of the observing machine's
sensors). In other words, the decomposition is a property of the evolution of
the "real" stimulus that is "out there" broadcasting energy to the observer.
The technique is illustrated with analytic and numerical examples.Comment: Contains 14 pages and 3 figures. For related papers, see
http://www.geocities.com/dlevin2001/ . New version is identical to original
version except for URL in the bylin
The Minkowski metric in non-inertial observer radar coordinates
We give a closed expression for the Minkowski (1+1)-dimensional metric in the
radar coordinates of an arbitrary non-inertial observer O in terms of O's
proper acceleration. Knowledge of the metric allows the non-inertial observer
to perform experiments in spacetime without making reference to inertial
frames. To clarify the relation between inertial and non-inertial observers the
coordinate transformation between radar and inertial coordinates, also is
given. We show that every conformally flat coordinate system can be regarded as
the radar coordinate system of a suitable observer for a suitable
parametrization of the observer worldline. Therefore, the coordinate
transformation between arbitrarily moving observers is a conformal
transformation and conformally invariant (1+1)-dimensional theories lead to the
same physics for all observers, independently of their relative motion.Comment: Revtex4, 6 pages, 1 figur
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