Oscillatons revisited

In this paper, we study some interesting properties of a spherically symmetric oscillating soliton star made of a real time-dependent scalar field which is called an oscillaton. The known final configuration of an oscillaton consists of a stationary stage in which the scalar field and the metric coefficients oscillate in time if the scalar potential is quadratic. The differential equations that arise in the simplest approximation, that of coherent scalar oscillations, are presented for a quadratic scalar potential. This allows us to take a closer look at the interesting properties of these oscillating objects. The leading terms of the solutions considering a quartic and a cosh scalar potentials are worked in the so called stationary limit procedure. This procedure reveals the form in which oscillatons and boson stars may be related and useful information about oscillatons is obtained from the known results of boson stars. Oscillatons could compete with boson stars as interesting astrophysical objects, since they would be predicted by scalar field dark matter models.Comment: 10 pages REVTeX, 10 eps figures. Updated files to match version published in Classical and Quantum Gravit

Precarious Labour in Portuguese Call Centres: An Anthropological Study

This thesis explores the themes of alienation and exploitation within the Portuguese call centre sector by focusing on the nature of value-creation in the organisation of labour, the effects this regime has on workers’ consciousness and agency, and how these effects are expressed in terms of class, gender and age. These questions are examined within the broader political and economic context. In recent years the ‘call centre domain’ in Portugal has been transformed into the main symbol of precariedade laboral (labour precariousness). The categories of trabalho precário (precarious labour), trabalhador precário (precarious worker) and precariedade laboral (labour precariousness) have recently entered into everyday language in Portugal. They are used by politicians and journalists as well as social movements and citizens as a way of protesting against the growing insecurity, contingency and vulnerability of formal wage employment as is found, for instance, in the increase of ‘atypical forms of employment’ such as temporary agency work. Call centres have been described as ‘electronic sweatshops’ because of such characteristics as repetitive tasks, high turnover, stress and burnout, psychological aggression from ‘angry’ customers, low autonomy in work tasks and automatism (scripting), leading to the stereotype of call centre workers as ‘human answering machines’. My research argues that, in the call centre labour regime workers are subjected to management by tight surveillance which robs humans of their defining characteristics of creative/symbolic thinking and complex communication and language. This management also imposes a gendered division of labour which separates men working in technical support help lines from women working in commercial help lines. The dispossession of call centre operators from what they do comes both from the gap between their expectations of and aspirations to social mobility, which were inculcated through their circles of socialization (family, state, school), and the feeling of ‘falling from grace’ after finishing their college degrees and having to enter into call centre work. This is a form of work which is not only socially perceived as unskilled, inferior and lacking career options, but most importantly as a form of work in which humans are disguised as robots. I conclude by situating my main findings within the anthropological and sociological scholarship related to the nature of value-creation in the capitalist labour process, gender commodification and the subjective experience of dispossession, downward class mobility and stigma

Environmental effects in the quantum-classical transition for the delta-kicked harmonic oscillator

We discuss the roles of the macroscopic limit and of different system-environment interactions in the quantum-classical transition for a chaotic system. We consider the kicked harmonic oscillator subject to reservoirs that correspond in the classical case to purely dissipative or purely diffusive behavior, in a situation that can be implemented in ion trap experiments. In the dissipative case, we derive an expression for the time at which quantum and classical predictions become different (breaking time) and show that a complete quantum-classical correspondence is not possible in the chaotic regime. For the diffusive environment we estimate the minimum value of the diffusion coefficient necessary to retrieve the classical limit and also show numerical evidence that, for diffusion below this threshold, the breaking time behaves, essentially, as in the case of the system without a reservoir.Comment: 16 pages, 13 figures. Accepted for publication in Phys. Rev.

Uso de PCR em tempo real como ferramenta para garantir a autenticidade de alimentos processados à base de mamão (Carica papaya).

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Desenvolvimento de metodologia para detecção simultânea de organismo geneticamente modificado e de patógenos em extrato hidrossolúvel de soja.

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Desenvolvimento de metodologia para detecção simultânea de organismo geneticamente modificado e de patógenos em extrato hidrossolúvel de soja.

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Conical refraction in generalized biaxial media: A geometric algebra approach

It is well-know that conical refraction occurs for electric anisotropic biaxial crystals when the wave vector has the direction of the medium optic axes. In this paper, we show that conical refraction occurs in an analogous away for a more general type of biaxial media that have simultaneously electric and magnetic anisotropies. Furthermore, the new coordinate-free approach based on geometric algebra, developed by the authors in previous papers to address anisotropy, is shown to shed new light on this classic topic of optics that is conical refraction.info:eu-repo/semantics/acceptedVersio

Comparison of biocenoses from sequencing batch and sequencing biofilm batch reactors

Since the extensive research during the 70s, sequencing batch reactors (SBR) have become a quite common modification of activated sludge process. Additionally, the SBR can be combined with biofilm growth on the surface of a support material originating the Sequencing Batch Biofilm Reactors (SBBR). While several comparative studies between the two systems were done in terms of organic carbon and nutrients removal efficiency, a detailed comparison of their biocenoses is not documented in the literature. The present work aims to compare the biocenoses from SBR and SBBR. In order to reach this objective four reactors were operated in parallel. One reactor was operated just with suspended biomass (SBR1) while the others combined suspended biomass with biofilm cultivation. The biofilm was formed on a new type of polyethylene support developed by University of Minho, called DupUM. The bed formed by these supports occupied 5 % (SBBR2), 10 % (SBBR3) and 20 % (SBBR4) of the reactor volume. Microscopic inspection revealed that the quality of biocenoses from reactors started to differ very soon after the inoculation. The biocenose of SBR1 and SBBR2 was dominated by filamentous microorganisms, while in SBBR3 and SBBR4 the communities were clearly more complex. The incorporation of an optimized amount of support for biofilm growth apparently suppressed the overgrowth of filamentous microorganisms. The differences between the biocenoses of the reactors are documented in figure 1

Biofilm reactor technology as an alternative to control fungal filamentous bulking caused by Galactomyces geotrichum

The present work aims to evaluate a strategy for solving fungal filamentous bulking caused by Galactomyces geotrichum. For this study, four sequencing batch reactors (SBR) fed with acetate were operated without (SBR1) and with support for biofilm growth [5 % (SBR2), 10 % (SBR3) and 20 % (SBR4) of the reactor volume]. The results demonstrated an overabundance of G. geotrichum in the SBR operating just with suspended biomass. The incorporation of an optimized amount of support for biofilm growth (10 %) seemed to suppress the overgrowth of the G. geotrichum filaments probably due to the combined effect of a decreased biomass loading and an increased shear force