1,158 research outputs found
Thermodynamics of the glassy state: effective temperature as an additional system parameter
A system is glassy when the observation time is much smaller than the
equilibration time. A unifying thermodynamic picture of the glassy state is
presented. Slow configurational modes are in quasi-equilibrium at an effective
temperature. It enters thermodynamic relations with the configurational entropy
as conjugate variable. Slow fluctuations contribute to susceptibilities via
quasi-equilibrium relations, while there is also a configurational term.
Fluctuation-dissipation relations also involve the effective temperature.
Fluctuations in the energy are non-universal, however. The picture is supported
by analytically solving the dynamics of a toy model.Comment: 5 pages, REVTEX. Phys. Rev. Lett, to appea
Thermodynamic picture of the glassy state
A picture for thermodynamics of the glassy state is introduced. It assumes
that one extra parameter, the effective temperature, is needed to describe the
glassy state. This explains the classical paradoxes concerning the Ehrenfest
relations and the Prigogine-Defay ratio. As a second part, the approach
connects the response of macroscopic observables to a field change with their
temporal fluctuations, and with the fluctuation-dissipation relation, in a
generalized non-equilibrium way.Comment: Proceedings of the Conference "Unifying Concepts in Glass Physics",
ICTP, Trieste, 15 - 18 September 199
On a Three-Dimensional Gravity Model with Higher Derivatives
The purpose of this work is to present a model for 3D massive gravity with
topological and higher-derivative terms. Causality and unitarity are discussed
at tree-level. Power-counting renormalizability is also contemplated.Comment: 9 pages, Latex, no figures; to be published in Gen. Rel. Gra
Does a preference for fatty foods prior to commencing treatment with the ketogenic diet predict the efficacy of this diet?
AbstractThe ketogenic diet can be effective in children who suffer from drug-resistant epilepsy. However, it is still hard to predict how large an effect this diet will have for an individual child. Previous data suggests a high-fat food preference is more likely in those with epilepsy, as assessed by in-person forced-choice design. The aim of this study is to examine whether a partiality to fatty foods prior to commencing the ketogenic diet can be used as a predictive factor for the efficacy of this diet in children with drug-resistant epilepsy.Data from 43 children aged between 2 and 19 years was used in this retrospective, non-controlled, non-randomised, open study. All children had followed the ketogenic diet for a period of 3 months or more. Before commencing the diet, a food record was collected for each child to determine the percentage of daily energy-intake accounted for by fats. Parents of the participants completed a questionnaire to measure fat-preference in the pre-diet period and received a score to objectify the efficacy of the treatment.The raw scores on the food record and on the questionnaire were divided into subgroups. Subsequently Kendall's tau-b was calculated for the correlation between each combination of variables. A non-significant correlation was found for the relationship between the food record and the questionnaire (p=.939), the relationship between the food record and the efficacy of the treatment (p=.827) and the relationship between the questionnaire and the efficacy of the treatment (p=.539). This means treatment efficacy cannot be predicted by the child's food preference
Assessing the Entrepreneurial Ecosystem of Science Technology Engineering and Mathematics (STEM) Researchers in Nigeria
Abstract: The external context plays a vital role for the promotion of entrepreneurship especially in entrepreneurial universities. The study therefore deploys a mixed methodology (quantitative and qualitative) approach to understand the role that innovation and entrepreneurship infrastructure plays in facilitating the development and commercialization of research outputs from the science, technology, engineering and mathematics (STEM) Faculties in a university in Nigeria. Questionnaire was administered on sixty lecturers/researchers across these six faculties (Science, Engineering, Basic Medical Sciences, Clinical Sciences, Pharmacy and Agriculture) which had 85% response rate. Eleven follow-up interviews were carried out in four Faculties. While field observation was carried out in four research and innovation facilities (the university’s central science laboratory, central technical workshop and the intellectual property & technology transfer office). An Incubation Centre located outside but near the university was also visited. Based on the information collected, the study provided strategic implications for policymaking, practice and theory
Role of Visual Dysfunction in Postural Control in Children With Cerebral Palsy
Introduction: Deficient postural control is one of the key problems in cerebral palsy (CP). Little, however, is known about the specific nature of postural problems of children with CP, nor of the relation between abnormal posture and dysfunction of the visual system. Aim of the study: To provide additional information on the association of abnormalities in postural control and visual dysfunction of the anterior or posterior part of the visual system. Methods: Data resulting from ophthalmologic, orthoptic, neurological, neuro-radiological, and ethological investigations of more than 313 neurologically impaired children were retrospectively analyzed. Results: Abnormal postural control related to ocular and ocular motor disorders consisted of anomalous head control and subsequent abnormal head posture and torticollis. The abnormal postural control related to retrochiasmatical damage of the visual system consisted of a torticollis combined with adjustment of the upper part of the body, as if at the same time adapting to a combination of defects and optimizing residual visual functions. Conclusion: Visual dysfunctions play a distinct role in the postural control of children with CP
Intensity Distribution of Waves Transmitted Through a Multiple Scattering Medium
The distributions of the angular transmission coefficient and of the total
transmission are calculated for multiple scattered waves. The calculation is
based on a mapping to the distribution of eigenvalues of the transmission
matrix. The distributions depend on the profile of the incoming beam. The
distribution function of the angular transmission has a stretched exponential
decay. The total-transmission distribution grows log-normally whereas it decays
exponentially.Comment: 8 pages, revtex3.0, 3 postscript figures, NvR0
On the Dirac Eigenvalues as Observables of the on-shell N=2 D=4 Euclidean Supergravity
We generalize previous works on the Dirac eigenvalues as dynamical variables
of the Euclidean gravity and N=1 D=4 supergravity to on-shell N=2 D=4 Euclidean
supergravity. The covariant phase space of the theory is defined as as the
space of the solutions of the equations of motion modulo the on-shell gauge
transformations. In this space we define the Poisson brackets and compute their
value for the Dirac eigenvalues.Comment: 10 pages, LATeX fil
Bath generated work extraction and inversion-free gain in two-level systems
The spin-boson model, often used in NMR and ESR physics, quantum optics and
spintronics, is considered in a solvable limit to model a spin one-half
particle interacting with a bosonic thermal bath. By applying external pulses
to a non-equilibrium initial state of the spin, work can be extracted from the
thermalized bath. It occurs on the timescale \T_2 inherent to transversal
(`quantum') fluctuations. The work (partly) arises from heat given off by the
surrounding bath, while the spin entropy remains constant during a pulse. This
presents a violation of the Clausius inequality and the Thomson formulation of
the second law (cycles cost work) for the two-level system.
Starting from a fully disordered state, coherence can be induced by employing
the bath. Due to this, a gain from a positive-temperature (inversion-free)
two-level system is shown to be possible.Comment: 4 pages revte
Dimensional regularization of the path integral in curved space on an infinite time interval
We use dimensional regularization to evaluate quantum mechanical path
integrals in arbitrary curved spaces on an infinite time interval. We perform
3-loop calculations in Riemann normal coordinates, and 2-loop calculations in
general coordinates. It is shown that one only needs a covariant two-loop
counterterm (V_{DR} = R/8) to obtain the same results as obtained earlier in
other regularization schemes. It is also shown that the mass term needed in
order to avoid infrared divergences explicitly breaks general covariance in the
final result.Comment: 13 pages, 10 figures, LaTe
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