1,168 research outputs found
Autofluorescence Lifetimes in Patients With Choroideremia Identify Photoreceptors in Areas With Retinal Pigment Epithelium Atrophy.
The purpose of this study was to investigate fundus autofluorescence lifetimes in patients with choroideremia and to identify tissue-specific lifetime characteristics and potential prognostic markers.
Autofluorescence lifetimes of the retina were measured in two spectral channels (498-560 nm and 560-720 nm) in patients with choroideremia and age-matched healthy controls. Furthermore, autofluorescence intensities and spectral-domain optical coherence tomography (OCT) data were acquired and compared to fundus autofluorescence lifetime data.
Sixteen eyes from 8 patients with advanced choroideremia (mean ± SD age, 55 ± 13 years) were included in this study and compared with 10 age-matched healthy participants. Whereas fundus autofluorescence intensity measurement identified areas of remaining retinal pigment epithelium (RPE), autofluorescence lifetime maps identified areas with remaining photoreceptor layers in OCT but RPE atrophy. In these areas, mean (±SEM) lifetimes were 567 ± 59 ps in the short and 603 ± 49 ps in the long spectral channels (+98% and +88% compared to controls). In areas of combined RPE atrophy and loss of photoreceptors, autofluorescence lifetimes were significantly prolonged by 1116 ± 63 ps (+364%) in the short and by 915 ± 52 ps (+270%) in the long spectral channels compared with controls.
Because autofluorescence lifetimes identify areas of remaining photoreceptors in the absence of RPE, this imaging modality may be useful to monitor disease progression in the natural course of disease and in context of potential future therapeutic interventions
Broadening of Spectral Lines due to Dynamic Multiple Scattering and the Tully-Fisher Relation
The frequency shift of spectral lines is most often explained by the Doppler
Effect in terms of relative motion, whereas the Doppler broadening of a
particular line mainly depends on the absolute temperature. The Wolf effect on
the other hand deals with the correlation induced spectral change and explains
both the broadening and shift of the spectral lines. In this framework a
relation between the width of the spectral line is related to the redshift z
for the line and hence with the distance. For smaller values of z a relation
similar to the Tully-Fisher relation can be obtained and for larger values of z
a more general relation can be constructed. The derivation of this kind of
relation based on dynamic multiple scattering theory may play a significant
role in explaining the overall spectra of quasi stellar objects. We emphasize
that this mechanism is not applicable for nearby galaxies, .Comment: 18 pages, 5 figures, revised Version has been submitted to Physical
Review A. (2nd author's affiliation corrected
Kolmogorov-Sinai entropy from recurrence times
Observing how long a dynamical system takes to return to some state is one of
the most simple ways to model and quantify its dynamics from data series. This
work proposes two formulas to estimate the KS entropy and a lower bound of it,
a sort of Shannon's entropy per unit of time, from the recurrence times of
chaotic systems. One formula provides the KS entropy and is more theoretically
oriented since one has to measure also the low probable very long returns. The
other provides a lower bound for the KS entropy and is more experimentally
oriented since one has to measure only the high probable short returns. These
formulas are a consequence of the fact that the series of returns do contain
the same information of the trajectory that generated it. That suggests that
recurrence times might be valuable when making models of complex systems
Entangling power and operator entanglement in qudit systems
We establish the entangling power of a unitary operator on a general
finite-dimensional bipartite quantum system with and without ancillas, and give
relations between the entangling power based on the von Neumann entropy and the
entangling power based on the linear entropy. Significantly, we demonstrate
that the entangling power of a general controlled unitary operator acting on
two equal-dimensional qudits is proportional to the corresponding operator
entanglement if linear entropy is adopted as the quantity representing the
degree of entanglement. We discuss the entangling power and operator
entanglement of three representative quantum gates on qudits: the SUM, double
SUM, and SWAP gates.Comment: 8 pages, 1 figure. Version 3: Figure was improved and the MS was a
bit shortene
Propagation inhibition and wave localization in a 2D random liquid medium
Acoustic propagation and scattering in water containing many parallel
air-filled cylinders is studied. Two situations are considered and compared:
(1) wave propagating through the array of cylinders, imitating a traditional
experimental setup, and (2) wave transmitted from a source located inside the
ensemble. We show that waves can be blocked from propagation by disorders in
the first scenario, but the inhibition does not necessarily imply wave
localization. Furthermore, the results reveal the phenomenon of wave
localization in a range of frequencies.Comment: Typos in Fiures are correcte
Расчет гашения обратного напряжения в импульсной схеме
Grid and e-science infrastructure interoperability is an increasing demand for Grid applications but interoperability based on common open standards adopted by Grid middle-wares are only starting to emerge on Grid infrastructures and are not broadly provided today. In earlier work we have shown how open standards can be improved by lessons learned from cross-Grid applications that require access to both, High Throughput Computing (HTC) resources as well as High Performance Computing (HPC) resources. This paper provides more insights in several concepts with a particular focus on effectively describing Grid job descriptions in order to satisfy the demands of e-scientists and their cross-Grid applications. Based on lessons learned over years gained with interoperability setups between production Grids such as EGEE, DEISA, and NorduGrid, we illustrate how common open Grid standards (i.e. JSDL and GLUE2) can take cross-Grid application experience into account
Cracking Of Petroleum Residues By Reactive Molecular Distillation
It is known that the Brazilian oils are more heavy - super heavy - viscous, its operation is difficult, especially its production, including all stages - elevation, runoff and primary processing - in addition to their transfer, and refining itself. Studies indicate the existence of oil fields as heavy lifting and that the simple flow of the base of the pit to the surface seems impossible at first sight, especially in off-shore fields, compromising both technically and economically a project to produce a new field. Therefore, efforts are needed to develop alternatives aimed at reducing the API gravity, viscosity and sulfur content of extra-heavy oil, adding a higher commercial value for these oils. This work aims to study, propose and develop enhanced hybrid process that transforms the extra-heavy oil, or part thereof, in lighter crude oil to generate a mixture: lower sulfur content, lower density, lower viscosity, lower content of volatile (aromatics and asphaltenes), greater resistance to the processes of purification. The process studied is the Reactive molecular distillation with the addition of tetralin that suffer from high temperature cracking of molecules, providing protons that help the breakdown of asphaltenes and residues will suffer as a consequence physicochemical changes, such as those mentioned above. This way you can improve the problems associated with the deposition of asphaltenes at high temperatures. The conversion of light with immediate reduction of API gravity and sulfur content promoted a better use of extra-heavy oil and the DMR is a product of high-value oil and very interesting for the oil industry and the environment. The experimental work proposed in this study was conducted to cracking and separation of fractions and petroleum. The evaluation and characterization of the cracking results were obtained after analysis of properties such as density, viscosity, sulfur content, molar mass and mass balance of the currents. © 2012 Published by Elsevier Ltd.42329334Erciyes, A.T., Ishikawa, H., Inuzuka, M., Hiraoka, S., Mori, H.E., Yamada, I., Vaporization of binary liquid mixtures from surface at reduced pressure (1987) Chem Eng Symp Series, 1, pp. A359-A371Moraes, E.B., Batistella, C.B., Torres Alvarez, M.E., Maciel Filho, R., Wolf Maciel, M.R., Evaluation of tocopherol recovery through simulation of molecular distillation process (2004) Appl Biochem Biotech, 114, pp. 689-711Noeres, C., Kenig, E.Y., Górak, A., Modelling of reactive separation processes (2003) Reactive Absorption and Reactive Distillation. Chem Eng Process, 42, pp. 157-178Duarte, F.A., Mello, P.A., Bizzi, C.A., Nunes, M.A.G., Moreira, E.M., Alencar, M.S., Motta, H.N., Flores, E.M.M., Sulfur removal from hydrotreated petroleum fractions using ultrasound-assisted oxidative desulfurization process (2001) Fuel, 90, pp. 2158-216
Second harmonics and compensation effect in ceramic superconductors
A three-dimensional lattice of the Josephson junctions with a finite
self-conductance is employed to model the ceramic superconductors. The
nonlinear ac susceptibility and the compensation effect are studied by Monte
Carlo simulations in this model. The compensation effect is shown to be due to
the existence of the chiral glass phase. We demonstrate, in agreement with
experiments, that this effect may be present in the ceramic superconductors
which show the paramagnetic Meissner effect.Comment: 6 pages, latex, 4 figures, Phys. Rev. B (accepted
Entanglement capability of self-inverse Hamiltonian evolution
We determine the entanglement capability of self-inverse Hamiltonian
evolution, which reduces to the known result for Ising Hamiltonian, and
identify optimal input states for yielding the maximal entanglement rate. We
introduce the concept of the operator entanglement rate, and find that the
maximal operator entanglement rate gives a lower bound on the entanglement
capability of a general Hamiltonian.Comment: 4 pages, no figures. Version 3: small change
Electronic Structure of Calcium Hexaboride within the Weighted Density Approximation
We report calculations of the electronic structure of CaB using the
weighted density approximation (WDA) to density functional theory. We find a
semiconducting band structure with a sizable gap, in contrast to local density
approximation (LDA) results, but in accord with recent experimental data. In
particular, we find an -point band gap of 0.8 eV. The WDA correction of the
LDA error in describing the electronic structure of CaB is discussed in
terms of the orbital character of the bands and the better cancelation of
self-interactions within the WDA.Comment: 1 figur
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