Solution of the quantum harmonic oscillator plus a delta-function potential at the origin: The oddness of its even-parity solutions

We derive the energy levels associated with the even-parity wave functions of the harmonic oscillator with an additional delta-function potential at the origin. Our results bring to the attention of students a non-trivial and analytical example of a modification of the usual harmonic oscillator potential, with emphasis on the modification of the boundary conditions at the origin. This problem calls the attention of the students to an inaccurate statement in quantum mechanics textbooks often found in the context of solution of the harmonic oscillator problem.Comment: 9 pages, 3 figure

Galli-Galli Disease: A Rare Acantholytic Variant of Dowling-Degos Disease

Galli-Galli disease is a rare acantholytic variant of Dowling-Degos disease, with few cases reported in the literature. We describe a case of Galli-Galli disease and review the literature

Influence of the local morphology on the surface tension of injection molded polypropylene

Publicado em “Proceedings of PPS-29 : The 29th International Conference of the Polymer Processing Society - Conference Papers. ISBN 978-0-7354-1227-9”In this work, we investigate the development of the morphology of an injection molding polypropylene under the local thermomechanical environment imposed during processing, and its effect on the contact angle and, hence, on the surface tension of the moldings. Melt and mold temperatures were varied in two levels. The local thermomechanical environment was characterized by mold filling computational simulations that allow the calculation of thermomechanical variables (e.g., local temperatures, shear stresses) and indices (related to the local morphology development). In order to investigate the structural hierarchy variations of the moldings in the thickness direction, samples from skin to core were used. The molecular orientation and degree of crystallinity were determined as function of the thickness, as well as the contact angle. The variations of the degree of crystallinity were assessed by differential scanning calorimetry. The level of molecular orientation was evaluated by birefringence measurements. The contact angles were measured in deionized water by sessile drop (needle in) method at room temperature, to determine the wettability of the samples. The contact angles were found to vary along the molding thickness in the skin, transition and core layers. These variations are related to the local morphologies developed. Results suggest that water contact angle increases with the level of molecular orientation and for finer microstructures

Hanbury Brown Twiss effect for ultracold quantum gases

We have studied 2-body correlations of atoms in an expanding cloud above and below the Bose-Einstein condensation threshold. The observed correlation function for a thermal cloud shows a bunching behavior, while the correlation is flat for a coherent sample. These quantum correlations are the atomic analogue of the Hanbury Brown Twiss effect. We observe the effect in three dimensions and study its dependence on cloud size.Comment: Figure 1 availabl

Ionization rates in a Bose-Einstein condensate of metastable Helium

We have studied ionizing collisions in a BEC of He*. Measurements of the ion production rate combined with measurements of the density and number of atoms for the same sample allow us to estimate both the 2 and 3-body contributions to this rate. A comparison with the decay of the number of condensed atoms in our magnetic trap, in the presence of an rf-shield, indicates that ionizing collisions are largely or wholly responsible for the loss. Quantum depletion makes a substantial correction to the 3-body rate constant.Comment: 4 pages, 3 figure

Structure evolution during deformation of novel polymer systems based on poly(ethylene terephthalate) reinforced with inorganic particles

Inorganic particles have been incorporated into poly(ethylene terephthalate), PET, matrix with the aim of offering some aesthetic effects to the standard transparent beverage packaging. To assess to the effect of different type of inorganic particles (with different interaction with the polymeric matrix) in the deformation behaviour of PET composites, particles such as aluminium, bronze, nanoclay, graphite and mica, were used. Two types of processing methods, ensuring a good mixing, were adopted for the composite preparation: i) melt-blending in an asymmetric batch mini-mixer followed by compression and ii) melt-blending in a twin screw extruder followed by injection moulding. The structural and mechanical behaviours of neat PET and its composites were evaluated during uniaxial stretching at temperatures above the glass transition temperature, Tg, namely at 85, 90, 95, 100 ºC, using a standard tensile stretching machine equipped with an environmental chamber. This study aims at understanding the deformation behaviour of the materials at temperatures found in conventional transformation methods used for packaging. To interpret the structural evolution occurring in the samples, off-line techniques such as DSC, WAXD and SEM were used. A detailed structural evolution was accomplished by applying different stretching ratios to the samples up to a maximum of 5x. Injection moulded samples were also characterized for their mechanical properties at room temperature in order to assess the materials behaviour in service. From all particles studied the PET/Aluminium and PET/Bronze composites are the ones showing the best combination of aesthetic effects, deformation behaviour and final mechanical properties. Comparing to neat PET, their general properties are the same during the deformation process making the new materials suitable for conventional processing techniques. It was found that both particles offer superior molecular mobility to PET at room temperature. In other words, these composites present a higher deformation capacity, however its elastic modulus and tensile strength at yield are slightly reduced

Getting the elastic scattering length by observing inelastic collisions in ultracold metastable helium atoms

We report an experiment measuring simultaneously the temperatureand the flux of ions produced by a cloud of triplet metastablehelium atoms at the Bose-Einstein critical temperature. The onsetof condensation is revealed by a sharp increase of the ion fluxduring evaporative cooling. Combining our measurements withprevious measurements of ionization in a pure BEC,we extract an improved value of the scattering length$a=11.3^{+2}_{-1}$ nm. The analysis includes corrections takinginto accountthe effect of atomic interactions on the criticaltemperature, and thus an independent measurement of the scatteringlength would allow a new test of these calculations

Rare variants of malignant melanoma – a clinical and histopathological challenge

Introduction: Malignant melanoma may present a great variety of histopathological patterns. Besides the classic forms of melanoma, there are a number of variants that have been described, such as polypoid, verrucous, desmoplastic, myxoid, chondroid, balloon-cell, rhabdoid, animal-type, amelanotic, spitzoid, nevoid. The aim of this study was to characterize the rare histopathologic variants of malignant melanoma observed in a Dermatopathology Laboratory in a period of 15 years (1995-2009). Material and Methods: Analized data included: patient age and sex, clinical diagnosis, melanoma location, Breslow and Clark level, presence of ulceration and follow-up. These variants were grouped according to architectural, cytologic and/or stromal changes. Results: Eighty-seven rare histopathologic variants of melanoma were observed, corresponding to 6,5% of all melanomas. We have found predominance of females in spitzoid and of males in animal-type melanoma. There were some preferential locations: face in animal type,trunk in polypoid, limbs in verrucous, and subungual in chondroid melanoma. We identified ulceration in 73% of polypoid, in 60% of verrucous and 50% of amelanotic melanomas. A higher mortality rate was documented in mixed variant (polypoid/animal-type), desmoplastic, polypoid and animal-type. Conclusions: The recognition of these variants is important, not only by the clinical and histopathological challenge in the differential diagnosis with other skin tumors, but also because of the possible implication of some of these variants, with peculiar biological behavior, in the prognosis