[en] The subject of this thesis is an experimental study of the pseudo-scalar mesons photoproduction on the proton in an energy range from √S=1450 MeV to 2100 MeV. It has been realized with the 4π CLAS detector of Th. Jefferson Laboratory. A software has been developed in order to perform the time calibration of the tagging system, and allowed us to measure a time resolution of 150 ps (FWHM). Gla Data have been analyzed. We determine CLAS energy resolution and show that these values are compatible with those given in the detector conceptual design report. Information from the analysis of the neutral mesons photoproduction channels and from the study of the p(γ, pπ⁺π^-) reaction has been used to develop correction methods, applied to raw data, in order to extract the differential cross-sections for the reactions p(γ, p)π⁰. New data points are shown and compared to the VPI multipole analysis. A preliminary study of the p(γ, p)η is stated in order to establish the method limits. An anomaly has been found in the data at a total center of mass energy of √s = 1790 MeV and is discussed. (author)

[en] Short communication

[en] In the influence of a negative charge deposition on the top oxide, i.e. above the polysilicon gate, of MOS transistor working in the enhancement mode with a P type channel, is examined. The magnitude of the parasitic currents which appear between source and drain is similar to the currents normally available on classical devices. The electrical characteristics of this parasitic devices are discussed, and a model is proposed

[en] Wafer scale integrated-MOS circuits problems related to test and reconfiguration by electron beams are analyzed. First of all the alterations in characteristics of MOS circuits submitted to an electron beam testing are considered. Then the capabilities of reconfiguration by an electron beam bombardment are discussed. The various phenomena involved are reviewed. Experimental data are reported and discussed on the light of data of the literature. (Auth.)

[en] The effects of the Chernobyl nuclear accident on the psychology of the affected population have been much discussed. The psychological dimension has been advanced as a factor explaining the emergence, from 1990 onwards, of a post-accident crisis in the main CIS countries affected. This article presents the conclusions of a series of European studies, which focused on the consequences of the Chernobyl accident. These studies show that the psychological and social effects associated with the post-accident situation arise from the interdependency of a number of complex factors exerting a deleterious effect on the population. We shall first attempt to characterise the stress phenomena observed among the population affected by the accident. Secondly, we will be presenting an anlysis of the various factors that have contributed to the emerging psychological and social features of population reaction to the accident and in post-accident phases, while not neglecting the effects of the pre-accident situation on the target population. Thirdly, we shall devote some initial consideration to the conditions that might be conducive to better management of post-accident stress. In conclusion, we shall emphasise the need to restore confidence among the population generally. (Author)

[en] Living conditions in the contaminated territories of Bielorussia after the Chernobyl accident: evaluation of the situation in the district of Chetchersk in Bielorussia. This article presents an analysis of the social and economic aspects of radiological protection in the territories contaminated by the Chernobyl accident. It is based on the results of two surveys performed in 1994 on the living conditions of the inhabitants of a territorial community located in Bielorussia, 180 km north of Chernobyl. The first part presents the radiological post-accident situation of the district, together with an analysis of this situation's demographic impact since 1986. The second part presents a description of the modes of exposure of the inhabitants of the contaminated territories and an assessment of he various countermeasures programmes initiated by the authorities in the legislative framework of 1991. The last part addresses the economic aspects of the Chetchersk district and an evaluation of the consequences of the radiological situation on the economic, and above all agricultural, activities of the district.The conclusion highlights the difficulties that face the Byelorussian authorities today. The now definitive presence of inhabitants in a durably contaminated environment poses a new category of problems. The objectives of radiological protection have to be reshaped within a set of constraints of different types, notably social and economic. The development of radiological safety cannot be dissociated from a return to quality living in these territories. This necessarily entails re-establishing a climate of social confidence. The initial legislative plan for post-accident management must be adapted to give greater autonomy to local participants in the reconstruction of satisfactory living conditions. (authors)

[en] The electrical properties of B₁₄Si are interpreted by using a model of medium range disorder; the d.c. and a.c. conductivities, the photoconductivity and the thermoelectric power were measured over a wide range of temperatures. The data can be explained well by the existence of a deep dominant level of energy Esub(a) = 0.38 eV and a disorder parameter approximately 0.045 eV. (Auth.)

[en] The elastic modulus and internal friction of silver irradiated by electrons in the temperature range 9-300 K have been studied. The first pinning stage for the dislocations appears between 25-50 K and is attributed to the long range migration of free interstitials. Following irradiations at temperatures greater than or equal to 80 K, the peaking effect has been observed and its characteristics studied as a function of the temperature of irradiation, strain amplitude, instantaneous flux of electrons and the purity of the samples. The results are critically compared with the various theories of the peaking effect

[en] The threshold energy for Frenkel pair creation at low temperature is determined in copper and silver from internal friction and modulus measurements during electron irradiation. The subthreshold phenomena are connected in copper to defects creation in the vicinity of the dislocations and in silver they correspond mainly to impurity effects. The thermal variation of the threshold energy is studied in the two metals and discussed in terms of the annealing models of point defects. (author)

[en] The decrease observed in the pinning rate of dislocations by irradiation induced defects in copper between 80 K and 180 K has been interpreted by different authors as a proof of the validity of the two interstitial model. A critical study of similar experiments to date, shows that there are important differences between them; consequently it is necessary to carry out the measurements of the thermal variation of the pinning rate and isochronal annealing experiments after irradiation on the same specimen and under identical experimental conditions. This study has been carried out for copper and it is shown that when the number of pinning points does not decrease during isochronal annealing, there is no longer a decrease of the pinning rate. A similar type of experiment on silver yields analogous results. It is concluded that the decrease observed under certain conditions in the pinning rate curves is not a proof of the two interstitial model. (author)