1,298 research outputs found
Mixed Symmetry Solutions of Generalized Three-Particle Bargmann-Wigner Equations in the Strong-Coupling Limit
Starting from a nonlinear isospinor-spinor field equation, generalized
three-particle Bargmann-Wigner equations are derived. In the strong-coupling
limit, a special class of spin 1/2 bound-states are calculated. These solutions
which are antisymmetric with respect to all indices, have mixed symmetries in
isospin-superspin space and in spin orbit space. As a consequence of this mixed
symmetry, we get three solution manifolds. In appendix \ref{b}, table 2, these
solution manifolds are interpreted as the three generations of leptons and
quarks. This interpretation will be justified in a forthcoming paper.Comment: 17 page
Resposta do milheto comum a doses de nitrogênio em planossolo típico no litoral sul do Rio Grande do Sul.
bitstream/item/31615/1/comunicado86.pd
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Integrating rich user feedback into intelligent user interfaces
The potential for machine learning systems to improve via a mutually beneficial exchange of information with users has yet to be explored in much detail. Previously, we found that users were willing to provide a generous amount of rich feedback to machine learning systems, and that the types of some of this rich feedback seem promising for assimilation by machine learning algorithms. Following up on those findings, we ran an experiment to assess the viability of incorporating real-time keyword-based feedback in initial training phases when data is limited. We found that rich feedback improved accuracy but an initial unstable period often caused large fluctuations in classifier behavior. Participants were able to give feedback by relying heavily on system communication in order to respond to changes. The results show that in order to benefit from the user’s knowledge, machine learning systems must be able to absorb keyword-based rich feedback in a graceful manner and provide clear explanations of their predictions
Método de determinação de cálcio iônico no leite bovino.
bitstream/item/44002/1/documento-321.pd
Atomistic modelling of large-scale metal film growth fronts
We present simulations of metallization morphologies under ionized sputter
deposition conditions, obtained by a new theoretical approach. By means of
molecular dynamics simulations using a carefully designed interaction
potential, we analyze the surface adsorption, reflection, and etching reactions
taking place during Al physical vapor deposition, and calculate their relative
probability. These probabilities are then employed in a feature-scale
cellular-automaton simulator, which produces calculated film morphologies in
excellent agreement with scanning-electron-microscopy data on ionized sputter
deposition.Comment: RevTeX 4 pages, 2 figure
Adição de gordura à dieta de bovinos de leite submetidos à transferência de embriões.
bitstream/item/43881/1/boletim-17.pd
Thermodynamics of a mixed quantum-classical Heisenberg model in two dimensions
We study the planar antiferromagnetic Heisenberg model on a decorated
hexagonal lattice, involving both classical spins (occupying the vertices) and
quantum spins (occupying the middle of the links). This study is motivated by
the description of a recently synthesized molecular magnetic compound. First,
we trace out the spin 1/2 degrees of freedom to obtain a fully classical model
with an effective ferromagnetic interaction. Then, using high temperature
expansions and Monte Carlo simulations, we analyse its thermal and magnetic
properties. We show that it provides a good quantitative description of the
magnetic susceptibility of the molecular magnet in its paramagnetic phase.Comment: Revtex, 6 pages, 4 included postscript figures, fig.1 upon request to
[email protected] . To appear in J. of Physic C (condensed matter
Multivariate moment closure techniques for stochastic kinetic models.
Stochastic effects dominate many chemical and biochemical processes. Their analysis, however, can be computationally prohibitively expensive and a range of approximation schemes have been proposed to lighten the computational burden. These, notably the increasingly popular linear noise approximation and the more general moment expansion methods, perform well for many dynamical regimes, especially linear systems. At higher levels of nonlinearity, it comes to an interplay between the nonlinearities and the stochastic dynamics, which is much harder to capture correctly by such approximations to the true stochastic processes. Moment-closure approaches promise to address this problem by capturing higher-order terms of the temporally evolving probability distribution. Here, we develop a set of multivariate moment-closures that allows us to describe the stochastic dynamics of nonlinear systems. Multivariate closure captures the way that correlations between different molecular species, induced by the reaction dynamics, interact with stochastic effects. We use multivariate Gaussian, gamma, and lognormal closure and illustrate their use in the context of two models that have proved challenging to the previous attempts at approximating stochastic dynamics: oscillations in p53 and Hes1. In addition, we consider a larger system, Erk-mediated mitogen-activated protein kinases signalling, where conventional stochastic simulation approaches incur unacceptably high computational costs
(Meta-)stable reconstructions of the diamond(111) surface: interplay between diamond- and graphite-like bonding
Off-lattice Grand Canonical Monte Carlo simulations of the clean diamond
(111) surface, based on the effective many-body Brenner potential, yield the
Pandey reconstruction in agreement with \emph{ab-initio}
calculations and predict the existence of new meta-stable states, very near in
energy, with all surface atoms in three-fold graphite-like bonding. We believe
that the long-standing debate on the structural and electronic properties of
this surface could be solved by considering this type of carbon-specific
configurations.Comment: 4 pages + 4 figures, Phys. Rev. B Rapid Comm., in press (15Apr00).
For many additional details (animations, xyz files) see electronic supplement
to this paper at http://www.sci.kun.nl/tvs/carbon/meta.htm
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