1,905 research outputs found
TRABALHO PRECĂRIO E REPRODUĂĂO SOCIAL: A REALIDADE DOS CATADORES DO LIXĂO DA CODIN EM CAMPOS DOS GOYTACAZES/RJ.
Resumo O presente trabalho propĂ”e uma reflexĂŁo sobre as condiçÔes de vida e de trabalho dos catadores de Campos dos Goytacazes/RJ, em especial, daquelas que se dedicaram ao trabalho no lixĂŁo da cidade. A anĂĄlise tem como referĂȘncia as transformaçÔes econĂŽmicas que ocorreram no Brasil a partir da dĂ©cada de 1990 e os seus rebatimentos no interior da classe trabalhadora, especialmente no que se refere ao aumento dos trabalhadores informais e precarizados. TambĂ©m percebendo o catador dentro de uma cadeia produtiva riquĂssima, onde este trabalhador Ă© o principal e mais fragilizado ator do processo
Approach to ergodicity in quantum wave functions
According to theorems of Shnirelman and followers, in the semiclassical limit
the quantum wavefunctions of classically ergodic systems tend to the
microcanonical density on the energy shell. We here develop a semiclassical
theory that relates the rate of approach to the decay of certain classical
fluctuations. For uniformly hyperbolic systems we find that the variance of the
quantum matrix elements is proportional to the variance of the integral of the
associated classical operator over trajectory segments of length , and
inversely proportional to , where is the Heisenberg
time, being the mean density of states. Since for these systems the
classical variance increases linearly with , the variance of the matrix
elements decays like . For non-hyperbolic systems, like Hamiltonians
with a mixed phase space and the stadium billiard, our results predict a slower
decay due to sticking in marginally unstable regions. Numerical computations
supporting these conclusions are presented for the bakers map and the hydrogen
atom in a magnetic field.Comment: 11 pages postscript and 4 figures in two files, tar-compressed and
uuencoded using uufiles, to appear in Phys Rev E. For related papers, see
http://www.icbm.uni-oldenburg.de/icbm/kosy/ag.htm
Design diversity: an update from research on reliability modelling
Diversity between redundant subsystems is, in various forms, a common design approach for improving system dependability. Its value in the case of software-based systems is still controversial. This paper gives an overview of reliability modelling work we carried out in recent projects on design diversity, presented in the context of previous knowledge and practice. These results provide additional insight for decisions in applying diversity and in assessing diverseredundant systems. A general observation is that, just as diversity is a very general design approach, the models of diversity can help conceptual understanding of a range of different situations. We summarise results in the general modelling of common-mode failure, in inference from observed failure data, and in decision-making for diversity in development.
Role of the JP45-Calsequestrin Complex on Calcium Entry in Slow Twitch Skeletal Muscles
We exploited a variety of mouse models to assess the roles of JP45-CASQ1 (CASQ, calsequestrin) and JP45-CASQ2 on calcium entry in slow twitch muscles. In flexor digitorum brevis (FDB) fibers isolated from JP45-CASQ1-CASQ2 triple KO mice, calcium transients induced by tetanic stimulation rely on calcium entry via La3+- and nifedipine-sensitive calcium channels. The comparison of excitation-coupled calcium entry (ECCE) between FDB fibers from WT, JP45KO, CASQ1KO, CASQ2KO, JP45-CASQ1 double KO, JP45-CASQ2 double KO, and JP45-CASQ1-CASQ2 triple KO shows that ECCE enhancement requires ablation of both CASQs and JP45. Calcium entry activated by ablation of both JP45-CASQ1 and JP45-CASQ2 complexes supports tetanic force development in slow twitch soleus muscles. In addition, we show that CASQs interact with JP45 at Ca2+ concentrations similar to those present in the lumen of the sarcoplasmic reticulum at rest, whereas Ca2+ concentrations similar to those present in the SR lumen after depolarization-induced calcium release cause the dissociation of JP45 from CASQs. Our results show that the complex JP45-CASQs is a negative regulator of ECCE and that tetanic force development in slow twitch muscles is supported by the dynamic interaction between JP45 and CASQs
Semiquantum Chaos and the Large N Expansion
We consider the dynamical system consisting of a quantum degree of freedom
interacting with quantum oscillators described by the Lagrangian \bq L
= {1\over 2}\dot{A}^2 + \sum_{i=1}^{N} \left\{{1\over 2}\dot{x}_i^2 - {1\over
2}( m^2 + e^2 A^2)x_i^2 \right\}. \eq In the limit , with
fixed, the quantum fluctuations in are of order . In this
limit, the oscillators behave as harmonic oscillators with a time dependent
mass determined by the solution of a semiclassical equation for the expectation
value \VEV{A(t)}. This system can be described, when \VEV{x(t)}= 0, by a
classical Hamiltonian for the variables G(t) = \VEV{x^2(t)}, ,
A_c(t) = \VEV{A(t)}, and . The dynamics of this latter system
turns out to be chaotic. We propose to study the nature of this large- limit
by considering both the exact quantum system as well as by studying an
expansion in powers of for the equations of motion using the closed time
path formalism of quantum dynamics.Comment: 30 pages, uuencoded LaTeX file (figures included
Periodic orbit quantization of chaotic maps by harmonic inversion
A method for the semiclassical quantization of chaotic maps is proposed,
which is based on harmonic inversion. The power of the technique is
demonstrated for the baker's map as a prototype example of a chaotic map.Comment: 7 pages, 1 figure, accepted for publication in Phys. Lett.
On the isospectral problem of the dispersionless Camassa-Holm equation
We discuss direct and inverse spectral theory for the isospectral problem of
the dispersionless Camassa--Holm equation, where the weight is allowed to be a
finite signed measure. In particular, we prove that this weight is uniquely
determined by the spectral data and solve the inverse spectral problem for the
class of measures which are sign definite. The results are applied to deduce
several facts for the dispersionless Camassa--Holm equation. In particular, we
show that initial conditions with integrable momentum asymptotically split into
a sum of peakons as conjectured by McKean.Comment: 26 page
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