1,989 research outputs found
Crescimento vegetativo do mamãozinho-de-veado (jacaratia corumbensis O. kuntze - caricaceae) no Sertão de Pernambuco.
Este trabalho teve como objetivo acompanhar o crescimento de 360 plantas de mam?ozinho-de-veado cultivadas em ·rea de caatinga da Embrapa Semi-¡rido, em PetrolinañPE, no perÌodo de 1999 a 2002
Ocorrência e utilização do facheiro (Pilosocereus pachycladus Ritter - Cactaceae) nas Caatingas de Pernambuco, Bahia e Paraíba.
Influência do substrato na germinação e no desenvolvimento do umbuzeiro (Spondias tuberosa Arruda).
Este trabalho teve como objetivo verificar a influÍncia de diferentes substratos na germinaÁ?o e no desenvolvimento de pl?ntulas de umbuzeiro
Myxomycetes, Physarales, Physaraceae, <i>Physarum rigidum</i> (G. Lister) G. Lister: Distribution extension and new records
Brésil
Plus que la "frontière" pionnière de l'intérieur du pays, c'est la région du Centre-Sud, et notamment ses grandes villes, qui attire le plus grand nombre de migrants brésiliens, comme l'atteste l'analyse des recensements de 1985 et 1991. Le Centre-Sud, en effet, est la région la plus urbanisée, la plus industrialisée du pays; elle est en situation dominante dans les secteurs tertiaires, de l'agriculture et de l'élevage, et constitue ainsi le véritable moteur de l'organisation territoriale brésilienne. Ainsi, cette restructuration spatiale, placée sous le signe de l'urbanisation, s'opère aujourd'hui selon deux modèles. D'une part, des zones à la production agropastorale moderne, bien reliées aux circuits économiques et, notamment, au complexe agro-industriel. D'autre part, des régions, dotées d'une population nombreuse, tournées vers l'autoconsommation et, donc, peu intégrées dans les circuits commerciaux. (Résumé d'auteur
Driving-dependent damping of Rabi oscillations in two-level semiconductor systems
We propose a mechanism to explain the nature of the damping of Rabi
oscillations with increasing driving-pulse area in localized semiconductor
systems, and have suggested a general approach which describes a coherently
driven two-level system interacting with a dephasing reservoir. Present
calculations show that the non-Markovian character of the reservoir leads to
the dependence of the dephasing rate on the driving-field intensity, as
observed experimentally. Moreover, we have shown that the damping of Rabi
oscillations might occur as a result of different dephasing mechanisms for both
stationary and non-stationary effects due to coupling to the environment.
Present calculated results are found in quite good agreement with available
experimental measurements
Conformance relations for distributed testing based on CSP
Copyright @ 2011 Springer Berlin HeidelbergCSP is a well established process algebra that provides comprehensive theoretical and practical support for refinement-based design and verification of systems. Recently, a testing theory for CSP has also been presented. In this paper, we explore the problem of testing from a CSP specification when observations are made by a set of distributed testers. We build on previous work on input-output transition systems, but the use of CSP leads to significant differences, since some of its conformance (refinement) relations consider failures as well as traces. In addition, we allow events to be observed by more than one tester. We show how the CSP notions of refinement can be adapted to distributed testing. We consider two contexts: when the testers are entirely independent and when they can cooperate. Finally, we give some preliminary results on test-case generation and the use of coordination messages. © 2011 IFIP International Federation for Information Processing
Geometrically induced singular behavior of entanglement
We show that the geometry of the set of quantum states plays a crucial role
in the behavior of entanglement in different physical systems. More
specifically it is shown that singular points at the border of the set of
unentangled states appear as singularities in the dynamics of entanglement of
smoothly varying quantum states. We illustrate this result by implementing a
photonic parametric down conversion experiment. Moreover, this effect is
connected to recently discovered singularities in condensed matter models.Comment: v2: 4 pags, 4 figs. A discussion before the proof of Proposition 1
and tomographic results were included, Propostion 2 was removed and the
references were fixe
Exact Solutions of the Klein-Gordon Equation in the Presence of a Dyon, Magnetic Flux and Scalar Potential in the Specetime of Gravitational Defects
In this paper we analyse the relativistic quantum motion of a charged spin-0
particle in the presence of a dyon, Aharonov-Bohm magnetic field and scalar
potential, in the spacetimes produced by an idealized cosmic string and global
monopole. In order to develop this analysis, we assume that the dyon and the
Aharonov-Bohm magnetic field are superposed to both gravitational defects. Two
distinct configurations for the scalar potential, , are considered:
the potential proportional to the inverse of the radial distance, i.e.,
, and the potential proportional to this distance, i.e.,
. For both cases the center of the potentials coincide with the
dyon's position. In the case of the cosmic string the Aharonov-Bohm magnetic
field is considered along the defect, and for the global monopole this magnetic
field pierces the defect. The energy spectra are computed for both cases and
explicitly shown their dependence on the electrostatic and scalar coupling
constants. Also we analyse scattering states of the Klein-Gordon equations, and
show how the phase shifts depend on the geometry of the spacetime and on the
coupling constants parameter.Comment: To be published in CQG. Minor comments adde
Causarum Investigatio and the Two Bell's Theorems of John Bell
"Bell's theorem" can refer to two different theorems that John Bell proved,
the first in 1964 and the second in 1976. His 1964 theorem is the
incompatibility of quantum phenomena with the joint assumptions of Locality and
Predetermination. His 1976 theorem is their incompatibility with the single
property of Local Causality. This is contrary to Bell's own later assertions,
that his 1964 theorem began with the assumption of Local Causality, even if not
by that name. Although the two Bell's theorems are logically equivalent, their
assumptions are not. Hence, the earlier and later theorems suggest quite
different conclusions, embraced by operationalists and realists, respectively.
The key issue is whether Locality or Local Causality is the appropriate notion
emanating from Relativistic Causality, and this rests on one's basic notion of
causation. For operationalists the appropriate notion is what is here called
the Principle of Agent-Causation, while for realists it is Reichenbach's
Principle of common cause. By breaking down the latter into even more basic
Postulates, it is possible to obtain a version of Bell's theorem in which each
camp could reject one assumption, happy that the remaining assumptions reflect
its weltanschauung. Formulating Bell's theorem in terms of causation is
fruitful not just for attempting to reconcile the two camps, but also for
better describing the ontology of different quantum interpretations and for
more deeply understanding the implications of Bell's marvellous work.Comment: 24 pages. Prepared for proceedings of the "Quantum [Un]speakables II"
conference (Vienna, 2014), to be published by Springe
- …