Two-component mixture of charged particles confined in a channel: melting

The melting of a binary system of charged particles confined in a {\it quasi}-one-dimensional parabolic channel is studied through Monte Carlo simulations. At zero temperature the particles are ordered in parallel chains. The melting is anisotropic and different melting temperatures are obtained according to the spatial direction, and the different types of particles present in the system. Melting is very different for the single-, two- and four-chain configurations. A temperature induced structural phase transition is found between two different four chain ordered states which is absent in the mono-disperse system. In the mixed regime, where the two types of particles are only slightly different, melting is almost isotropic and a thermally induced homogeneous distribution of the distinct types of charges is observed.Comment: To appear in Journal of Physics: condensed matter ; (13 pages, 12 figures

Development of liquid xenon detectors for medical imaging

In the present paper, we report on our developments of liquid xenon detectors for medical imaging, positron emission tomography and single photon imaging, in particular. The results of the studies of several photon detectors (photomultiplier tubes and large area avalanche photodiode) suitable for detection of xenon scintillation are also briefly described.Comment: 13 pages, 5 figures, presented on the International Workshop on Techniques and Applications of Xenon Detectors (Xenon01), ICRR, Univ. of Tokyo, Kashiwa, Japan, December 3-4, 2001 (submitted to proceedings

Insufficient heat treatment of eggs due to following cooking instructions in the labels

Purpose: The demand for ready-to-eat, prepared meals has risen over the years. Following a recipe is a reason pointed by some consumers for not monitoring doneness during cooking. Our aim was to investigate the inactivation of Salmonella in products with eggs during cooking according to instructions in labels/recipes. Methods & Materials: We have chosen a very popular and traditional Portuguese dish made with salted codfish, fried potatoes and eggs – “Bacalhau À Brás”. We bought in a supermarket three packages of a frozen, precooked dish of “Bacalhau à Brás”, all belonging to the same production lot. The package contained a 300 g meal, with the codfish and fried potatoes already precooked, being the consumer responsible to add one raw egg in the end of the recipe. In the package, the cooking instructions are provided: “Conditions of use/preparation: Without defrosting, place the stew in a non-stick frying pan, then place the potatoes over the top and let them cook on a low heat so that it defrosts completely. Add a beaten egg, slowly wrapped for about 2 minutes so that the egg is sufficiently cooked. Garnish with whole olives or slices and chopped fresh parsley.” These instructions were followed in the laboratory where a domestic food preparation was mimicked. Eggs contaminated with different levels of Salmonella were used. Results: The 2 min at low temperature after the addition of the raw egg, as indicated in the package of the pre-cooked dish tested, was not enough to complete inactivate Salmonella. The risk for Salmonella survival and recovery of injured cells increases with the initial level of contamination. Conclusion: Recipes where raw eggs are added by the consumers at home might constitute a safety issue due to failure in proper inactivation of Salmonella as the manufacturer's instructions might not be specific enough to guarantee sufficient time and temperature, which may lead to the survival of Salmonella. This study highlights the need to provide scientifically-based information on food labels to increase food safety.info:eu-repo/semantics/publishedVersio

Effects of a CPT-even and Lorentz-violating nonminimal coupling on the electron-positron scattering

We propose a new \emph{CPT}-even and Lorentz-violating nonminimal coupling between fermions and Abelian gauge fields involving the CPT-even tensor $(K_{F})_{\mu\nu\alpha\beta}$ of the standard model extension. We thus investigate its effects on the cross section of the electron-positron scattering by analyzing the process $e^{+}+e^{-}\rightarrow\mu^{+}+\mu^{-}$. Such a study was performed for the parity-odd and parity-even nonbirefringent components of the Lorentz-violating $(K_{F})_{\mu\nu\alpha\beta}$ tensor. Finally, by using experimental data available in the literature, we have imposed upper bounds as tight as $10^{-12}(eV)^{-1}$ on the magnitude of the CPT-even and Lorentz-violating parameters while nonminimally coupled.Comment: LaTeX2e, 06 pages, 01 figure