Quantum phase transition in an effective three-mode model of interacting bosons.

In this work we study an effective three-mode model describing interacting bosons. These bosons can be considered as exciton-polaritons in a semiconductor microcavity at the magic angle. This model exhibits quantum phase transition (QPT) when the parameters of the corresponding Hamiltonian are continuously varied. The properties of the Hamiltonian spectrum (e.g., the distance between two adjacent energy levels) and the phase space structure of the thermodynamic limit of the model are used to indicate QPT. The relation between spectral properties of the Hamiltonian and the corresponding classical frame of the thermodynamic limit of the model is established as indicative of QPT. The average number of bosons in a specific mode and the entanglement properties of the ground state as functions of the parameters are used to characterize the order of the transition and also to construct a phase diagram. Finally, we verify our results for experimental data obtained for a setting of exciton-polaritons in a semiconductor microcavity.

Breast reconstruction with autologous tissue--our clinical experience.

INTRODUCTION: Breast reconstruction after mastectomy gained new grounds since the introduction of autologous tissue and oncoplastic surgery techniques. Nowadays large postoperative breast defects can be treated with high quality tissues obtained by autogenous flap surgery, to achieve the best functional and physical results. OBJECTIVES: The purpose of this study is to analyze our results in breast reconstruction using autologous tissue and to emphasize the importance of a multidisciplinary team. MATERIAL AND METHODS: During a five year period (2005-2009) we performed 28 breast reconstructions after cancer surgery, 15 in delayed and 13 in primary reconstruction, using three types of flaps: latissiumus dorsi flap, transverse rectus abdominis myocutaneous flap and deep inferior epigastric artery perforator flap. RESULTS: Functional and cosmetic results were very good, only minor complications such as seroma and hematoma of the donor site and partial/marginal flap necrosis occurred after the surgical procedure. There were no major complications like total flap loss. CONCLUSIONS: Breast reconstruction with autologous tissue is a safe, well proved, although not easy procedure that confers best functional and cosmetic results and is at the same time oncologically safe.

Semiclassical corrections to the large- N limit of Dicke's model.

We use a semiclassical expansion as an alternative derivation of the well-known, rigorous result obtained by Hepp and Lieb for the classical limit of the spin-boson model. We also explicitly derive correction terms to the classical limit previously obtained in the context of Heisenberg equations of motion. We analyze the size and shape of the N (number of atoms) vs t (time) domain whithin which the corrections so obtained are useful.

Entanglement and classical instabilities: fingerprints of electron-hole-to-exciton phase transition in a simple model.

We propose a schematic model to study the formation of excitons in bilayer electron systems. The phase transition is signalized both in the quantum and classical versions of the model. In the present contribution we show that not only the quantum ground state but also higher energy states, up to the energy of the corresponding classical separatrix orbit, "sense" the transition. We also show two types of one-to-one correspondences in this system: On the one hand, between the changes in the degree of entanglement for these low-lying quantum states and the changes in the density of energy levels; on the other hand, between the variation in the expected number of excitons for a given quantum state and the behavior of the corresponding classical orbit.

Quantum-classical transition of the open quartic oscillator: The role of the environment.

We investigate the classical and quantum dynamics of the open quartic oscillator model. Typically quantum behavior such as collapses and revivals (also squeezing) are induced by the nonlinearity of the model. We show that purely diffusive environments, as expected, attenuate such phenomena. We obtain analytical results in both regimes classical and quantum and discuss the effect of a diffusive reservoir in the two cases. We show that "separation times" as usually defined in the literature are strongly observable (and initial condition) dependent, rendering a solid definition of a unique classical limit rather difficult. In particular, the separation time for the variance can be smaller than that for the expectation value of the position of the centroid of the wave packet. We find a hierarchy of time scales which depends on the observable and the reservoir.

Quantum time scales and the classical limit: analytic results for some simple systems.

We set up a semiclassical approximation which helps us clarify by means of several simple examples the rich variety of time scale in the quantum domain. The underlying structure of quantum and classical mechanics is so completly different that it is naive to expect to reach a classical regime by counting powers of the quantum scale variant Planck's over 2pi. We show although it is possible to define a time scale for nonclassical phenomena, but it is impossible to characterize quantum dynamics through a unique time scale, such as Ehrenfest's time. We use simple systems to critically discuss and illustrate these features of the quantum-classical limit.

[Training of local health managers: process of identification of strategic actions]. / Formação de gestores locais de saúde: processos para identificar estratégias de atuação.

In Brazil, in recent years, as a result of the increasing participation of county authorities in health care, a need for tools which would contribute to the better preparation of local administrators, complementary to the activities of a more academic nature, has been recognized. One of the possible alternatives is the exploitation of experiences, regarded as successful, in local health care planning and administration, by using them as material for "case studies" in activities with selected groups of health care administrators thus, stimulating the identification of those elements which contributed to the favorable results attained, and their interactions, in the quest for analogies which would facilitate the identification of new perspectives for their own situations. In this article an experience of a "case studies" development, in response to a demand from UNICEF, based on 8 counties in from the North and Northeast, which were successful in using a "focus approach" in their organization of data and their utilisation in a seminar with 21 local managers from both regions, is presented. During the seminar the local health managers attained greater knowledge of the strategies implemented and identified feasible intervention alternatives. The methodological proposition of teaching on the basis of case studies, using a conceptual strategy of grouping experiences according to specific dimensions enabled local health managers to learn from their practical experiences.

Rapid decoherence in integrable systems: a border effect.

We show that rapid decoherence, usually associated with chaotic dynamics, is not necessarily a hallmark of nonintegrability: border effects in integrable systems may produce similarly drastic decoherence rates. These can be found when the subsystem under observation possesses an energy limitation as, e.g., in the N-atom Jaynes-Cummings model. We show for this model that special initial coherent wave packets exhibit entropy production rates strikingly similar to the chaotic case. Also, a (de)localization phenomenon is found to be a function of the proximity to the phase-space border.

[Methodology for the assessment of activities in primary health care]. / Metodologia de avaliação do trabalho na atenção primaria à saúde.

A case study assessed health care activities in a primary health care facility to help develop methodologies of care work assessment and of the proposal of leading categories for the said processes, based on the work process. This study was developed at the Centro de Saúde Escola of the Faculdade de Medicina of the Universidade de São Paulo, using as empirical material the assessment of the care activities aimed at the emergency care and programmed care of 'chronic' patients (patients suffering from hypertension and diabetes). The analysis of these assessments which considered different moments of the work process (working objects, activity of agents, analysis of the working means and result of the work) suggest the need of creating analytical categories that will make workable the understanding of this process, inserting each moment to the work as a whole. The analytical categories proposed are: 1) workability as a means of making effective the proposed actions; 2) strategic effectiveness as a measure of the scope of the results that have been observed among patients and/or the population and that can be the result of the actions performed.

On the interplay between symmetry breaking, integrability, and chaos in the semiclassical limit of the Heisenberg system.

In this work we present a detailed numerical analysis of the interplay between symmetry breaking, integrability, and chaos in the two- and three-spin Heisenberg models. The results suggest that a very simple and powerful tool to convey such information are the plots of the energy level spacings Delta(n) versus the energy level index n, together with the correlation plots Delta(n+1)xDelta(n). When integrability is broken, these plots are shown to identify very sharply an energy below which one has chaotic behavior. The particularly strong point in favor of such analysis is that it can be useful in partially chaotic regimes. (c) 1995 American Institute of Physics.

Double-stranded polynucleotides as interferon inducers.

A discussion of factors considered influential in making a polynucleotide an efficient inducer of interferon was presented. These factors were double-strandedness of the polynucleotides, the sugar moiety of the polynucleotides, thermal stability, resistance to enzymatic degradation, and molecular size of the polynucloetides. Recent developments concerning interferon induction during virus infection were also discussed.