2,879 research outputs found
Quantum erasure in the presence of a thermal bath: the effects of system-environment microscopic correlations
We investigate the role of the environment in a quantum erasure setup in the
cavity quantum electrodynamics domain. Two slightly different schemes are
analyzed. We show that the effects of the environment vary when a scheme is
exchanged for another. This can be used to estimate the macroscopic parameters
related to the system-environment microscopic correlations.Comment: 10 pages, 2 figure
Analysis of the velocity field of granular hopper flow
We report the analysis of radial characteristics of the flow of granular
material through a conical hopper. The discharge is simulated for various
orifice sizes and hopper opening angles. Velocity profiles are measured along
two radial lines from the hopper cone vertex: along the main axis of the cone
and along its wall. An approximate power law dependence on the distance from
the orifice is observed for both profiles, although differences between them
can be noted. In order to quantify these differences, we propose a Local Mass
Flow index that is a promising tool in the direction of a more reliable
classification of the flow regimes in hoppers
Quantum critical point in the spin glass-antiferromagnetism competition in Kondo-lattice systems
A theory is proposed to describe the competition among antiferromagnetism
(AF), spin glass (SG) and Kondo effect. The model describes two Kondo
sublattices with an intrasite Kondo interaction strength and an
interlattice quantum Ising interaction in the presence of a transverse field
. The interlattice coupling is a random Gaussian distributed variable
(with average and variance ) while the field is
introduced as a quantum mechanism to produce spin flipping. The path integral
formalism is used to study this fermionic problem where the spin operators are
represented by bilinear combinations of Grassmann fields. The disorder is
treated within the framework of the replica trick. The free energy and the
order parameters of the problem are obtained by using the static ansatz and by
choosing both and to allow, as previously,
a better comparison with the experimental findings.
The results indicate the presence of a SG solution at low and for
temperature ( is the freezing temperature). When is
increased, a mixed phase AF+SG appears, then an AF solution and finally a Kondo
state is obtained for high values of . Moreover, the behaviors of the
freezing and Neel temperatures are also affected by the relationship between
and the transverse field . The first one presents a slight
decrease while the second one decreases towards a Quantum Critical Point (QCP).
The obtained phase diagram has the same sequence as the experimental one for
, if is assumed to increase with , and
in addition, it also shows a qualitative agreement concerning the behavior of
the freezing and the Neel temperatures.Comment: 11 pages, 3 figures, accepted for publication in J. Phys.
Control of state and state entanglement with a single auxiliary subsystem
We present a strategy to control the evolution of a quantum system. The novel
aspect of this protocol is the use of a \emph{single auxiliary subsystem}. Two
applications are given, one which allows for state preservation and another
which controls the degree of entanglement of a given initial state
New spectral data of some flavonoids from Deguelia hatschbachii A.M.G. Azevedo
From the roots of Deguelia hatschbachii, the known flavonoids scandenin (1), methyl robustate (2) and 4',5- dihydroxy-6-(3,3-dimethylalyll)-7-methoxy flavanone (3) were isolated and characterized by comparison of their spectroscopic data with those found in the literature. Now the inclusion of 1D- and 2D-NMR and MS/MS data has allowed the complete assignment of all hydrogen and carbon chemical shifts in their NMR spectra, as well as the elucidation of the fragmentation pathways of 1-3 in the mass spectrometer.Entre os flavonóides isolados de Deguelia hatschbachii¹ encontram-se escandenina (1), robustato de metila (2) e 4',5-diidroxi-6-(3,3-dimetilalila)-7-metoxiflavanona (3) que foram identificados pela comparação dos dados espectroscópicos previamente publicados. A obtenção de novos dados espectroscópicos (RMN, RMN-2D e EM/EM) permitiu a atribuição dos deslocamentos quÃmicos de todos os hidrogênios e carbonos nos espectros de RMN ¹H e 13C destas substâncias, assim como a elucidação dos caminhos de fragmentação de 1-3 no espectrômetro de massas.133137Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de NÃvel Superior (CAPES
Multiple mating rescues offspring sex ratio but not productivity in a haplodiploid exposed to developmental heat stress
Reproduction is generally more sensitive to high temperatures than survival and arguably a better predictor of the response of populations to climate change than survival estimates. Still, how temperature simultaneously impacts male and female reproductive success, the mating system and the operational sex ratio remains an open question.
Here, we addressed how a sublethal high temperature affects the reproductive system of the haplodiploid spider mite Tetranychus urticae. Males and females maintained at 25 or 36°C during development were paired and the fertility of both sexes, their mating and remating eagerness, and the paternity of the offspring of females with different mating histories were measured.
Female and male fertility decreased at 36°C compared to 25°C, resulting in lower offspring production and a more male-biased sex ratio, respectively, because of haplodiploidy. However, when either heat-stressed females or females that mated with heat-stressed males remated, there was a shift in paternity share, with more than one male contributing to the offspring. This was accompanied by reduced mating eagerness in pairs with partially sterile males and increased remating eagerness in pairs in which at least one sex was partially sterile in the first mating.
The observed temperature-induced changes in female remating eagerness and sperm use allowed restoring the offspring sex ratio, by increasing the proportion of fertilized offspring, but did not lead to the recovery of offspring number.
The temperature-induced changes in the mating behaviour and mating system should alter the interactions within and between the sexes, and with it the strength of sexual selection and sexual conflict in this species. Whether such changes are sufficient to prevent population extinction, despite the inability to recover offspring number, remains an open question.info:eu-repo/semantics/publishedVersio
Quantum Critical Point in the Spin Glass-Kondo Transition in Heavy Fermion Systems
The Kondo-Spin Glass competition is studied in a theoretical model of a Kondo
lattice with an intra-site Kondo type exchange interaction treated within the
mean field approximation, an inter-site quantum Ising exchange interaction with
random couplings among localized spins and an additional transverse field in
the x direction, which represents a simple quantum mechanism of spin flipping.
We obtain two second order transition lines from the spin-glass state to the
paramagnetic one and then to the Kondo state. For a reasonable set of the
different parameters, the two second order transition lines do not intersect
and end in two distinct QCP.Comment: 20 pages; 1 figure; to appear in Physical Review
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