Choice of studies at university, personality and socio-economic status. Comparison between French students in a public social sciences and humanities faculty and Brazilian law students in a private faculty

Several studies have examined the links between personality and choice of studies, particularly from a longitudinal point of view. This original research proposes to study these aspects a posteriori. The Rotter questionnaire (1966) was completed by two groups of students in psychology (N=65) and law (N= 91). The other particularity of the samples concerns the location and the differences in socio-economic backgrounds: privileged for law students in Brazil, modest for students in psychology in France. Most of the hypotheses put forward, particularly those related to the citizenship and political aspects, are verified on the basis of the binomial test

A. C. Power Losses in MOV Surge Arrestors

It was the objective of this study to measure power losses occurring in MOV surge arrestors as they were subjected to various voltage Excitations. In particular, power losses were observed in two MOV devices as sinusoidal voltages of different magnitudes were applied, at various frequencies in the range of typical power frequencies and common harmonics. Power losses were also observed in an MOV device for applied voltages consisting of the sum of 60 Hertz sinusoids and a single harmonic. The measurement procedure consisted of obtaining digital records representing the waveforms of voltage across and current through the MOV device during operation; power was calculated as the mean of the product of these digitally represented waveforms; This report contains a detailed description of the implementation of this procedure, as well as a discussion of some of its limitations when making measurements on highly reactive devices. Experimental results indicate that power losses in the MOV devices studied were primarily dependent upon frequency of operation, and peak amplitude of applied voltage. The results indicate that 60 Hertz specifications given for a particular device do not, in general, apply for other frequencies or non-sinusoidal excitation

Charge and energy dependence of the residence time of cosmic ray nuclei below 15 GeV/nucleon

The relative abundance of nuclear species measured in cosmic rays at Earth has often been interpreted with the simple leaky box model. For this model to be consistent an essential requirement is that the escape length does not depend on the nuclear species. The discrepancy between escape length values derived from iron secondaries and from the B/C ratio was identified by Garcia-Munoz and his co-workers using a large amount of experimental data. Ormes and Protheroe found a similar trend in the HEAO data although they questioned its significance against uncertainties. They also showed that the change in the B/C ratio values implies a decrease of the residence time of cosmic rays at low energies in conflict with the diffusive convective picture. These conclusions crucially depend on the partial cross section values and their uncertainties. Recently new accurate cross sections of key importance for propagation calculations have been measured. Their statistical uncertainties are often better than 4% and their values significantly different from those previously accepted. Here, these new cross sections are used to compare the observed B/C+O and (Sc to Cr)/Fe ratio to those predicted with the simple leaky box model

Source spectral index of heavy cosmic ray nuclei

From the energy spectra of the heavy nuclei observed by the French-Danish experiment on HEAO-3, the source spectra of the mostly primary nuclei (C, O, Ne, Mg, Si, Ca and Fe) in the framework of an energy dependent leaky box model (Engelmann, et al., 1985) were derived. The energy dependence of the escape length was derived from the observed B/C and sub-iron/iron ratios and the presently available cross sections for C and Fe on H nuclei (Koch-Miramond, et al., 1983). A good fit to the source energy spectra of all these nuclei was obtained by a power law in momentum with an exponent gamma = -2.4+0.05 for the energy range 1 to 25GeV/n (Engelmann, et al., 1985). Comparison with data obtained at higher energy suggested a progressive flattening of these spectra. More accurate spectral indices are sought by using better values of the escape length based on the latest cross section measurements (Webber 1984, Soutoul, et al., this conference). The aim is also to extend the analysis to lower energies down to 0.4GeV/n (kinetic energy observed near Earth), using data obtained by other groups. The only nuclei for which a good data base is possessed in a broad range of energies are O and Fe, so the present study is restricted to these two elements

Design, Synthesis and Relaxivity Behaviour of mRNA Targeting Contrast Agents

Introduction: Magnetic Resonance Imaging (MRI) is one of the most important diagnostic tools available in medicine. The specificity and sensitivity of MRI can be further enhanced by the introduction of contrast agents (CAs). As many clinically valuable targets reside inside the cell membrane, the development of efficient intracellular targeted MR contrast agent is required. Potential intracellular targets would be DNA, mRNA or protein/enzymes. The prerequisite for the intracellular targeting is not only the efficient delivery of probes inside the cell but also the colocalization with the target. The objective of the present study is to design and synthesize efficient intracellular MR contrast agents [1] which include three functional domains (i) Gd based MR reporter part (ii) antisense PNA to target mRNA (iii) cell penetrating peptide (CPP) or cholesterol as the delivery agent. The antisense PNA can hybridize uniquely to the complementary mRNA and provides cell specific targeting for cells containing the mRNA. Thus, the expression of the corresponding gene can be visualized non invasively by in vivo MR imaging. Methods: The conjugates were synthesized by continuous solid phase synthesis. Cellular uptake was confirmed by fluorescence microscopy, spectroscopy and MRI of labeled cells. Results: CPP conjugated mRNA targeting CAs were taken up efficiently into cells by an exclusively endosomal mechanism. A subtoxic labeling concentration at low micromolar range was sufficient to enhance significant MR imaging contrast. Cell free binding assays proved a specific interaction with a synthetic target. However, because of the vesicular entrapment, it can be expected that there would be a lack of specific interaction between CA and mRNA located in the cytosol. In order to overcome this problem, cholesterol conjugated CAs are designed and synthesized [2]. The idea behind cholesterol coupling was from the already published report [3] where covalent conjugates of cholesterol and siRNAs were facilitating cellular import and were able to silence protein expression effectively. Initial results have shown that these agents were delivered more efficiently than CPP conjugated CAs. Unfortunately, they were also entrapped in vesicles. Both types of CA were able to enhance contrast in labeled target containing as well as non-targeted parent cells. However, there was not efficient colocalization and specific interaction of CA and target mRNA achievable to be exploited for MR imaging purposes. Conclusion: CPP or lipid coupled CAs are internalized efficiently into cells. However, vesicular entrapment prevented sufficient specific interaction between CA and mRNA. Further modifications are required to achieve the release from endosomes or a direct uptake into the cytosol

Cosmic-ray propagation properties for an origin in SNRs

We have studied the impact of cosmic-ray acceleration in SNR on the spectra of cosmic-ray nuclei in the Galaxy using a series expansion of the propagation equation, which allows us to use analytical solutions for part of the problem and an efficient numerical treatment of the remaining equations and thus accurately describes the cosmic-ray propagation on small scales around their sources in three spatial dimensions and time. We found strong variations of the cosmic-ray nuclei flux by typically 20% with occasional spikes of much higher amplitude, but only minor changes in the spectral distribution. The locally measured spectra of primary cosmic rays fit well into the obtained range of possible spectra. We further showed that the spectra of the secondary element Boron show almost no variations, so that the above findings also imply significant fluctuations of the Boron-to-Carbon ratio. Therefore the commonly used method of determining CR propagation parameters by fitting secondary-to-primary ratios appears flawed on account of the variations that these ratios would show throughout the Galaxy.Comment: Accepted for publication in Ap