890 research outputs found
Backpropagation training in adaptive quantum networks
We introduce a robust, error-tolerant adaptive training algorithm for
generalized learning paradigms in high-dimensional superposed quantum networks,
or \emph{adaptive quantum networks}. The formalized procedure applies standard
backpropagation training across a coherent ensemble of discrete topological
configurations of individual neural networks, each of which is formally merged
into appropriate linear superposition within a predefined, decoherence-free
subspace. Quantum parallelism facilitates simultaneous training and revision of
the system within this coherent state space, resulting in accelerated
convergence to a stable network attractor under consequent iteration of the
implemented backpropagation algorithm. Parallel evolution of linear superposed
networks incorporating backpropagation training provides quantitative,
numerical indications for optimization of both single-neuron activation
functions and optimal reconfiguration of whole-network quantum structure.Comment: Talk presented at "Quantum Structures - 2008", Gdansk, Polan
Effectiveness of surgery for lumbar spinal stenosis
Background: The management of spinal stenosis by surgery has increased rapidly in the past two decades, however, there is still controversy regarding the efficacy of surgery for this condition. Our aim was to investigate the efficacy and comparative effectiveness of surgery in the management of patients with lumbar spinal stenosis. Methods: Electronic searches were performed on MEDLINE, EMBASE, AMED, CINAHL, Web of Science, LILACS and Cochrane Library from inception to November 2014. Hand searches were conducted on included articles and relevant reviews. We included randomised controlled trials evaluating surgery compared to no treatment, placebo/sham, or to another surgical technique in patients with lumbar spinal stenosis. Primary outcome measures were pain, disability, recovery and quality of life. The PEDro scale was used for risk of bias assessment. Data were pooled with a random-effects model, and the GRADE approach was used to summarise conclusions. Results: Nineteen published reports (17 trials) were included. No trials were identified comparing surgery to no treatment or placebo/sham. Pooling revealed that decompression plus fusion is not superior to decompression alone for pain (mean difference -3.7, 95% confidence interval -15.6 to 8.1), disability (mean difference 9.8, 95% confidence interval -9.4 to 28.9), or walking ability (risk ratio 0.9, 95% confidence interval 0.4 to 1.9). Interspinous process spacer devices are slightly more effective than decompression plus fusion for disability (mean difference 5.7, 95% confidence interval 1.3 to 10.0), but they resulted in significantly higher reoperation rates when compared to decompression alone (28% v 7%, P < 0.001). There are no differences in the effectiveness between other surgical techniques for our main outcomes. Conclusions: The relative efficacy of various surgical options for treatment of spinal stenosis remains uncertain. Decompression plus fusion is not more effective than decompression alone. Interspinous process spacer devices result in higher reoperation rates than bony decompression
Gravitational Collapse of Phantom Fluid in (2+1)-Dimensions
This investigation is devoted to the solutions of Einstein's field equations
for a circularly symmetric anisotropic fluid, with kinematic self-similarity of
the first kind, in -dimensional spacetimes. In the case where the radial
pressure vanishes, we show that there exists a solution of the equations that
represents the gravitational collapse of an anisotropic fluid, and this
collapse will eventually form a black hole, even when it is constituted by the
phantom energy.Comment: 10 page
Shell model in the complex energy plane and two-particle resonances
An implementation of the shell-model to the complex energy plane is
presented. The representation used in the method consists of bound
single-particle states, Gamow resonances and scattering waves on the complex
energy plane. Two-particle resonances are evaluated and their structure in
terms of the single-particle degreees of freedom are analysed. It is found that
two-particle resonances are mainly built upon bound states and Gamow
resonances, but the contribution of the scattering states is also important.Comment: 20 pages, 9 figures, submitted to Phys.Rev.
Interatomic potentials for atomistic simulations of the Ti-Al system
Semi-empirical interatomic potentials have been developed for Al, alpha-Ti,
and gamma-TiAl within the embedded atomic method (EAM) by fitting to a large
database of experimental as well as ab-initio data. The ab-initio calculations
were performed by the linear augmented plane wave (LAPW) method within the
density functional theory to obtain the equations of state for a number of
crystal structures of the Ti-Al system. Some of the calculated LAPW energies
were used for fitting the potentials while others for examining their quality.
The potentials correctly predict the equilibrium crystal structures of the
phases and accurately reproduce their basic lattice properties. The potentials
are applied to calculate the energies of point defects, surfaces, planar faults
in the equilibrium structures. Unlike earlier EAM potentials for the Ti-Al
system, the proposed potentials provide reasonable description of the lattice
thermal expansion, demonstrating their usefulness in the molecular dynamics or
Monte Carlo studies at high temperatures. The energy along the tetragonal
deformation path (Bain transformation) in gamma-TiAl calculated with the EAM
potential is in a fairly good agreement with LAPW calculations. Equilibrium
point defect concentrations in gamma-TiAl are studied using the EAM potential.
It is found that antisite defects strongly dominate over vacancies at all
compositions around stoichiometry, indicating that gamm-TiAl is an antisite
disorder compound in agreement with experimental data.Comment: 46 pages, 6 figures (Physical Review B, in press
Highlights of the SĂŁo Paulo ISEV workshop on extracellular vesicles in cross-kingdom communication
In the past years, extracellular vesicles (EVs) have become an important field of research since EVs have been found to play a central role in biological processes. In pathogens, EVs are involved in several events during the hostâpathogen interaction, including invasion, immunomodulation, and pathology as well as parasiteâparasite communication. In this report, we summarised the role of EVs in infections caused by viruses, bacteria, fungi, protozoa, and helminths based on the talks and discussions carried out during the International Society for Extracellular Vesicles (ISEV) workshop held in SĂŁo Paulo (November, 2016), Brazil, entitled Cross-organism Communication by Extracellular Vesicles: Hosts, Microbes and Parasites. © 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.11Ysciescopu
Spin dynamics in semiconductors
This article reviews the current status of spin dynamics in semiconductors
which has achieved a lot of progress in the past years due to the fast growing
field of semiconductor spintronics. The primary focus is the theoretical and
experimental developments of spin relaxation and dephasing in both spin
precession in time domain and spin diffusion and transport in spacial domain. A
fully microscopic many-body investigation on spin dynamics based on the kinetic
spin Bloch equation approach is reviewed comprehensively.Comment: a review article with 193 pages and 1103 references. To be published
in Physics Reports
Indicadores de qualidade do solo em sistemas de cultivo orgĂąnico e convencional no semi-ĂĄrido Cearense.
A qualidade do solo pode mudar com o passar do tempo, em decorrĂȘncia de eventos naturais ou açÔes antrĂłpicas. A adoção de prĂĄticas de cultivo orgĂąnico reduz o revolvimento do solo, favorecendo a recuperação de suas propriedades
fĂsicas e quĂmicas. Este trabalho teve como objetivo comparar propriedades fĂsicas,quĂmicas e biolĂłgicas de solos cultivados com algodĂŁo em bases orgĂąnicas e no
sistema convencional, assim como identificar as que possam ser utilizadas como indicadores de qualidade do solo. Selecionaram-se seis ĂĄreas submetidas ao cultivo orgĂąnico e trĂȘs ao cultivo convencional para coleta de amostras de solo deformadas e indeformadas, nas camadas de 0â10, 10â20 e 20â30 cm. TĂ©cnicas de estatĂstica univariada e multivariada foram utilizadas para anĂĄlise dos dados. Os resultados mostraram que os indicadores fĂsicos e quĂmicos testados individualmente nĂŁo foram sensĂveis para diferenciar as ĂĄreas sob sistema de cultivo orgĂąnico daquelas sob cultivo convencional. No entanto, a aplicação de tĂ©cnicas de anĂĄlise multivariada â no caso, componentes principais e a discriminante de Anderson â permitiu a distinção entre algumas ĂĄreas cultivadas sob cultivo orgĂąnico comparativamente Ă s convencionais, atĂ© mesmo as que estavam em transição.Dos indicadores biolĂłgicos, a fauna edĂĄfica mostrou-se mais precisa na avaliação
da qualidade do solo, distinguindo de forma satisfatĂłria as ĂĄreas sob sistema de cultivo orgĂąnico das que estavam sob sistema convencional
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