664 research outputs found
Analytic approximation to 5 dimensional Black Holes with one compact dimension
We study black hole solutions in space, using an expansion to
fourth order in the ratio of the radius of the horizon, , and the
circumference of the compact dimension, . A study of geometric and
thermodynamic properties indicates that the black hole fills the space in the
compact dimension at . At the same value of
the entropies of the uniform black string and of the black hole are
approximately equal.Comment: 21 pages, 4 figures. Replaces previous version, with added references
and slightly altered discussio
The low-frequency response in the surface superconducting state of ZrB single crystal}
The large nonlinear response of a single crystal ZrB to an ac field
(frequency 40 - 2500 Hz) for has been observed. Direct
measurements of the ac wave form and the exact numerical solution of the
Ginzburg-Landau equations, as well as phenomenological relaxation equation,
permit the study of the surface superconducting states dynamics. It is shown,
that the low frequency response is defined by transitions between the
metastable superconducting states under the action of an ac field. The
relaxation rate which determines such transitions dynamics, is found.Comment: 7 pages, 11 figure
Energy resolution of terahertz single-photon-sensitive bolometric detectors
We report measurements of the energy resolution of ultra-sensitive
superconducting bolometric detectors. The device is a superconducting titanium
nanobridge with niobium contacts. A fast microwave pulse is used to simulate a
single higher-frequency photon, where the absorbed energy of the pulse is equal
to the photon energy. This technique allows precise calibration of the input
coupling and avoids problems with unwanted background photons. Present devices
have an intrinsic full-width at half-maximum energy resolution of approximately
23 terahertz, near the predicted value due to intrinsic thermal fluctuation
noise.Comment: 11 pages (double-spaced), 5 figures; minor revision
Electronic information and educational environment of RSVPU
The article describes the electronic information and educational environment, that is built on the basis of integration of different tools and services used for the implementation of the educational process envisaged types of academic work. Describes the concept, structure and interface of this information systemВ статье рассмотрена электронная информационно-образовательная среда, построенная на основе интеграции различных инструментов и сервисов, используемых для реализации предусмотренных учебным процессом видов учебной работы. Описана концепция, структура и интерфейс информационной систем
Wave Function of a Brane-like Universe
Within the mini-superspace model, brane-like cosmology means performing the
variation with respect to the embedding (Minkowski) time before fixing
the cosmic (Einstein) time . The departure from Einstein limit is
parameterized by the 'energy' conjugate to , and characterized by a
classically disconnected Embryonic epoch. In contrast with canonical quantum
gravity, the wave-function of the brane-like Universe is (i) -dependent,
and (ii) vanishes at the Big Bang. Hartle-Hawking and Linde proposals dictate
discrete 'energy' levels, whereas Vilenkin proposal resembles -particle
disintegration.Comment: Revtex, 4 twocolumn pages, 3 eps figures (accepted for publication in
Class. Quan. Grav.
Small Black Holes on Branes: Is the horizon regular or singular ?
We investigate the following question: Consider a small mass, with
(the ratio of the Schwarzschild radius and the bulk curvature length) much
smaller than 1, that is confined to the TeV brane in the Randall-Sundrum I
scenario. Does it form a black hole with a regular horizon, or a naked
singularity? The metric is expanded in and the asymptotic form of
the metric is given by the weak field approximation (linear in the mass). In
first order of we show that the iteration of the weak field
solution, which includes only integer powers of the mass, leads to a solution
that has a singular horizon. We find a solution with a regular horizon but its
asymptotic expansion in the mass also contains half integer powers.Comment: Accepted for publication in PR
Age-related hearing loss: biological aspects
Presbycusis is one of the more prevalent neurodegenerative disease of aging. There are many studies about the influence of environmental and genetic factors. Age-related hearing loss is caused by changes in peripheral (cell loss in organ of Corti, spiral ganglion and stria vascularis) and central auditory systems (consequent to peripheral modifications or for changes in the neurobiologic activity underlying central processing of auditory informations) [1]. Consequences are reduced sensitivity, tuning sharpness, compression, and reduced signal-to-noise ratios, deficits in auditory discrimination, temporal processing, processing of degraded auditory signals or when embedded in competing acoustic signals. Approaching biology of age-related hearing loss is complex: it needs to clarify some peripheral aspects with different cochlear structure and cellular type affected, and some others central auditory processing aspects. There are some peripherally induced central effects and others direct neurodegenerative changes in the brain. Moreover biochemical and mechanical injury in life course can represent a risk factor for auditory function particularly for organ of Corti. This complicates the attempt of separate pure presbycusis from socioacusis. Research indicated some "longevity genes" and longevity-promoting life-styles (obesity and correlated conditions like hyperlipidemia, hypercholesterolemia, hypertension, hyperhomocysteinemia and cardiovascular disease, smoking, diet and diabetes [2,3]. Age-related hearing loss seems to occur more frequently in industrial population than in non-industrial [4]. The relation between alleles pro or against-aging and environment maybe play a determinant role in the evolution of hearing with aging. Until such genes are identified, the best strategy is to reduce environmental risk factors (noise exposure, ototoxic drugs, industrial solvents or combinations of these)
Project-Based Learning with the Eyes of a University Student
В статье описано, как осуществляется проектное обучение в университете, разобран реальный пример выполнения проекта студентом по теме, связанной с нейронными сетями, а также описаны достоинства и недостатки данного метода обучения и способы его улучшения.The article describes how project-based learning is carried out in the university; it also analyses the way how project about neural network is performed by a student and it describes advantages and disadvantages of a given learning method and ways of its improving
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