Comment on the Adiabatic Condition

The experimental observation of effects due to Berry's phase in quantum systems is certainly one of the most impressive demonstrations of the correctness of the superposition principle in quantum mechanics. Since Berry's original paper in 1984, the spin 1/2 coupled with rotating external magnetic field has been one of the most studied models where those phases appear. We also consider a special case of this soluble model. A detailed analysis of the coupled differential equations and comparison with exact results teach us why the usual procedure (of neglecting nondiagonal terms) is mathematically sound.Comment: 9 page

Phototherapy of Renal Pruritus and of Pruritus Associated with HIV Infection

Introdução e Objectivos: A fototerapia (UVB isolados ou em combinação aos UVA) tem-se revelado eficaz no tratamento do prurido grave que complica, frequentemente, a doença renal crónica (DRC) ou a infecção pelo vírus da imunodeficiência humana (VIH). Pretendemos neste estudo avaliar a eficácia e segurança das radiações UVA e UVB de banda-larga, combinadas, no tratamento do prurido refractário associado à DRC e à infecção pelo VIH. Material e métodos: Para tal foi efectuado um estudo retrospectivo e descritivo de 83 doentes (55 com prurido renal e 28 com infecção pelo VIH), que efectuaram 3 sessões/semana de UVAB. Os UVB foram administrados na dose inicial de 20 a 30mJ/cm2 (70% da DEM), aumentados em 30mJ/cm2 por sessão, na ausência de eritema, até à regressão do prurido. As doses iniciais e subsequentes de UVA foram calculadas de acordo com o fototipo, não se ultrapassando a dose máxima de 6J/cm2. Resultados: Os doentes com prurido renal (33 homens e 22 mulheres) tinham em média 57,7 anos de idade, duração da DRC de 8,7 anos e do prurido de 27,8 meses; realizaram, em média 11,1 sessões de fototerapia com doses cumulativas de UVA de 22,9J/cm2 e de UVB de 1900mJ/cm2; verificou-se melhoria do prurido após 5 sessões e alivio completo no final do ciclo; todos os doentes continuavam assintomáticos após período médio de 11,2 meses. Os doentes com infecção VIH (18 homens e 10 mulheres) apresentavam, em média, idade de 40,8 anos, seropositividade conhecida há 2,5 anos, prurido generalizado com duração de 13,4 meses e contagem de CD4 de 177 células/μL; efectuaram, em média, 12,1 sessões de fototerapia, 24,3J/cm2 de UVA e 2000mJ/cm2 de UVB; em 21 doentes constatou-se diminuição do prurido após 5 sessões de UVAB e regressão completa no final do ciclo, permanecendo assintomáticos após período médio de 13,4 meses. Não ocorreram efeitos secundários, excepto pigmentação moderada e eritema ligeiro e transitório. Nos doentes com infecção pelo VIH não se detectou agravamento da imunossupressão. Conclusão: Estes resultados apoiam a eficácia e segurança da fototerapia combinada no controlo do prurido associado à DRC e à infecção pelo VIH, podendo o tratamento de um maior número de doentes confirmar as suas potenciais vantagens em relação aos UVA ou UVB utilizados isoladamente

Schwinger's Method for the Massive Casimir Effect

We apply to the massive scalar field a method recently proposed by Schwinger to calculate the Casimir effect. The method is applied with two different regularization schemes: the Schwinger original one by means of Poisson formula and another one by means of analytical continuation.Comment: plain TeX, 6 pages, DFTUZ-93-2

The distance to the LMC cluster NGC 1866 and the surrounding field

We use the Main Sequence stars in the LMC cluster NGC 1866 and of Red Clump stars in the local field to obtain two independent estimates of the LMC distance. We apply an empirical Main Sequence-fitting technique based on a large sample of subdwarfs with accurate {\sl Hipparcos} parallaxes in order to estimate the cluster distance modulus, and the multicolor Red Clump method to derive distance and reddening of the LMC field. We find that the Main Sequence-fitting and the Red Clump distance moduli are in significant disagreement; NGC 1866 distance is equal to $\rm (m-M)_{0,NGC 1866}=18.33\pm$0.08 (consistent with a previous estimate using the same data and theoretical Main Sequence isochrones), while the field stars provide $\rm (m-M)_{0,field}=18.53\pm$0.07. This difference reflects the more general dichotomy in the LMC distance estimates found in the literature. Various possible causes for this disagreement are explored, with particular attention paid to the still uncertain metallicity of the cluster and the star formation history of the field stars.Comment: 5 pages, incl. 1 figure, uses emulateapj.sty, ApJ accepte

Behavioural compensation by drivers of a simulator when using a vision enhancement system

Technological progress is suggesting dramatic changes to the tasks of the driver, with the general aim of making driving environment safer. Before any of these technologies are implemented, empirical research is required to establish if these devices do, in fact, bring about the anticipated improvements. Initially, at least, simulated driving environments offer a means of conducting this research. The study reported here concentrates on the application of a vision enhancement (VE) system within the risk homeostasis paradigm. It was anticipated, in line with risk homeostasis theory, that drivers would compensate for the reduction in risk by increasing speed. The results support the hypothesis although, after a simulated failure of the VE system, drivers did reduce their speed due to reduced confidence in the reliability of the system

Shear strength of adhesively bonded polyolefins with minimal surface preparation

Interest in polyethylene and polypropylene bonding has increased in the last years. However, adhesive joints with adherends which are of low surface energy and which are chemically inert present several difficulties. Generally, their high degree of chemical resistance to solvents and dissimilar solubility parameters limit the usefulness of solvent bonding as a viable assembly technique. One successful approach to adhesive bonding of these materials involves proper selection of surface pre-treatment prior to bonding. With the correct pre-treatment it is possible to glue these materials with one or more of several adhesives required by the applications involved. A second approach is the use of adhesives without surface pre-treatment, such as hot melts, high tack pressure-sensitive adhesives, solvent-based specialty adhesives and, more recently, structural acrylic adhesives as such 3M DP-8005® and Loctite 3030®. In this paper, the shear strengths of two acrylic adhesives were evaluated using the lap shear test method ASTM D3163 and the block shear test method ASTM D4501. Two different industrial polyolefins (polyethylene and polypropylene) were used for adherends. However, the focus of this study was to measure the shear strength of polyethylene joints with acrylic adhesives. The effect of abrasion was also studied. Some test specimens were manually abraded using 180 and 320 grade abrasive paper. An additional goal of this work was to examine the effect of temperature and moisture on mechanical strength of adhesive joints

Concept for a Time-of-Flight Small Angle Neutron Scattering Instrument at the European Spallation Source

A new Small Angle Neutron Scattering instrument is proposed for the European Spallation Source. The pulsed source requires a time-of-flight analysis of the gathered neutrons at the detector. The optimal instrument length is found to be rather large, which allows for a polarizer and a versatile collimation. The polarizer allows for studying magnetic samples and incoherent background subtraction. The wide collimation will host VSANS and SESANS options that increase the resolution of the instrument towards um and tens of um, respectively. Two 1m2 area detectors will cover a large solid angle simultaneously. The expected gains for this new instrument will lie in the range between 20 and 36, depending on the assessment criteria, when compared to up-to-date reactor based instruments. This will open new perspectives for fast kinetics, weakly scattering samples, and multi-dimensional contrast variation studies.Comment: 18 pages, 10 figure

Troubles with quantum anistropic cosmological models: Loss of unitarity

The anisotropic Bianchi I cosmological model coupled with perfect fluid is quantized in the minisuperspace. The perfect fluid is described by using the Schutz formalism which allows to attribute dynamical degrees of freedom to matter. A Schr\"odinger-type equation is obtained where the matter variables play the role of time. However, the signature of the kinetic term is hyperbolic. This Schr\"odinger-like equation is solved and a wave packet is constructed. The norm of the resulting wave function comes out to be time dependent, indicating the loss of unitarity in this model. The loss of unitarity is due to the fact that the effective Hamiltonian is hermitian but not self-adjoint. The expectation value and the bohmian trajectories are evaluated leading to different cosmological scenarios, what is a consequence of the absence of a unitary quantum structure. The consistency of this quantum model is discussed as well as the generality of the absence of unitarity in anisotropic quantum models.Comment: Latex file, 18 pages. To appear in General Relativity and Gravitatio

A non inflationary model with scale invariant cosmological perturbations

We show that a contracting universe which bounces due to quantum cosmological effects and connects to the hot big-bang expansion phase, can produce an almost scale invariant spectrum of perturbations provided the perturbations are produced during an almost matter dominated era in the contraction phase. This is achieved using Bohmian solutions of the canonical Wheeler-de Witt equation, thus treating both the background and the perturbations in a fully quantum manner. We find a very slightly blue spectrum ($n_{_\mathrm{S}}-1>0$). Taking into account the spectral index constraint as well as the CMB normalization measure yields an equation of state that should be less than $\omega\lesssim 8\times 10^{-4}$, implying $n_{_\mathrm{S}}-1 \sim \mathcal{O}(10^{-4})$, and that the characteristic size of the Universe at the bounce is $L_0 \sim 10^3 \ell_\mathrm{Planck}$, a region where one expects that the Wheeler-DeWitt equation should be valid without being spoiled by string or loop quantum gravity effects.Comment: 9 pages, 4 figure