979 resultados para Ion lourd et rapide
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We investigate a planar ion chip design with a two-dimensional array of linear ion traps for the scalable quantum information processor. The segmented electrodes reside in a single plane on a substrate and a grounded metal plate, a combination of appropriate rf and DC potentials are applied to them for stable ion confinement, and the trap axes are located above the surface at a distance controlled by the electrodes' lateral extent and the substrate's height as discussed. The potential distributions are calculated using static electric field qualitatively. This architecture is conceptually simple and many current microfabrication techniques are feasible for the basic structure. It may provide a promising route for scalable quantum computers.
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A description of the cyanobacteriae Anabaena circinalis Rabenhorst and Anabaena flos aquae Brebisson, ex Bornet et Flanault is given. Illustrations are included.
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The disolvated proton, H(OH2)2+ is employed as a chemical reagent in low pressure (˂ 10-5 torr) investigations by ion cyclotron resonance spectroscopy. Since termolecular reactions are absent at low pressure, disolvated protons are not generally observed. However H(OH2)2+ is produced in a sequence of bimolecular reactions in mixtures containing H2O and one of a small number of organohalide precursors. Then a series of hydrated Lewis bases is produced by H3O+ transfer from H(OH2)2+. In Chapter II, the relative stability of hydrated bases containing heteroatoms of both first and second row elements is determined from the preferred direction of H3O+ transfer between BH(OH2)+ complexes. S and P containing bases are shown to bind H3O+ more weakly than O and N bases with comparable proton affinities. A simple model of hydrogen bonding is proposed to account for these observations.
H+ transfer from H(OH2)2+ to several Lewis bases also occurs at low pressure. In Chapter III the relative importance of H3O+ transfer and H+ transfer from H(OH2)2+ to a series of bases is observed to be a function of base strength. Beginning with CH3COOH, the weakest base for which H+ transfer is observed, the importance of H+ transfer increases with increasing proton affinity of the acceptor base. The nature of neutral products formed from H(OH2)2+ by loss of H+ is also considered.
Chapters IV and V deal with thermochemistry of small fluorocarbons determined by photoionization mass spectrometry. The enthalpy of formation of CF2 is considered in Chapter IV. Photoionization of perfluoropropylene, perfluorocyclopropane, and trifluoromethyl benzene yield onsets for ions formed by loss of a CF2 neutral fragment. Earlier determinations of ΔH°f298 (CF2) are reinterpreted using updated thermochemical values and compared with results of this study. The heat of formation of neutral perfluorocyclopropane is also derived. Finally, the energetics of interconversion of perfluoropropylene and perfluorocyclopropane are considered for both the neutrals and their molecular ions.
In Chapter V the heats of formation of CF3+ and CF3I+are derived from photoionization of CF3I. These are considered with respect to ion-molecule reactions observed in CF3I monitored by the techniques of ion cyclotron resonance spectroscopy. Results obtained in previous experiments are also compared.
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Species of Pithophora occasionally appear in Europe and are associated mostly with the tropical, higher water plants, cultivated in numerous botanical gardens. In June 1973 pale green, branched threads were discovered in the pond of the Wroclaw Botanical Garden, amongst filaments of Spirogyra crassa (Kutz.) Czurda emend. and Cladophora glomerata (L.) Kutz. floating on the water surface. They were maintained for several weeks in crude cultures and produced numerous, dark akinetes tightly packed with reserve material. This collected material was found to be a member of the family Pithophora, Wittr. Further examinations identified the material as Pithophora oedogonia. The findings point out that it is probable, that species of Pithophora Wittr. can become acclimatized in Europe, primarily in ponds of botanical gardens, where consequently they are able to tangle easily with higher tropical plants.
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Analyse about all the economical connexions between the European Union and Algeria since 1962 until 2014.
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Utilization of the heavy isotope of nitrogen as a tracer has found numerous applications in soil biology. It allows better definition of different stages of the nitrogen cycle, in particular the immobilization-mineralization cycle. In this work, the authors report the results of calculations of natural isotope ratios of nitrogen in samples of water, soil and vegetation prevailing in Dombes and discuss the possibilities of errors and coefficients of fractionation.
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During hydrographic and plankton studies carried out since 1960 in the coastal zone between the Ebro and Castellon (western Mediterranean), data has been collected which confirms the importance of ciliates in the composition and activity of the plankton. The ciliates in 413 samples of 100 ml of water were counted, having been examined with the Utermohl microscope after sedimentation. The samples studied were distributed according to the density of their population. subject for study. The author concludes that recognition of the role of ciliates as an important link in the food chain of the sea would simplify the interpretation of certain problems posed by the nutrition of certain groups of planktonic animals.
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Ce rapport présente les activités et les résultats de l’atelier Vision 2050: Changement climatique, pêche et aquaculture en Afrique de l’Ouest. Les objectifs de l’atelier étaient de discuter les questions critiques et les incertitudes auxquelles est confronté le secteur de la pêche et de l’aquaculture au Ghana, au Sénégal et en Mauritanie, d’élaborer des scénarios sectoriels pour 2050 et de discuter de l’implication de ces scénarios dans le contexte du changement climatique pour ces pays et la région ouest africaine.
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Presented in the first part of this thesis is work performed on the ionizing energy beam induced adhesion enhancement of thin (~ 500 Angstrom) Au films on GaAs substrates. The ionizing beam, employed in the present thesis, is the MeV ions (i.e., 16O, 19F, and 35Cl), with energies between 1 and 20 MeV. Using the "Scratch" test for adhesion measurement, and ESCA for chemical analysis of the film-substrate interface, the native oxide layer at the interface is shown to play an important role in the adhesion enhancement by the ionizing radiation. A model is discussed which explains the experimental data on the the dependence of adhesion enhancement on the energy which was deposited into electronic processes at the interface. The ESCA data indicate that the chemical bonds (or compounds), which are responsible for the increase in the thin film adherence, are hydroxides rather than oxides.
In the second part of the thesis we present a research performed on the radiation damage in GaAs crystals produced by MeV ions. Lattice parameter dilatation in the surface layers of the GaAs crystals becomes saturated after a high dose bombardment at room temperature. The strain produced by nuclear collisions is shown to relax partially due to electronic excitation (with a functional dependence on the nuclear and electronic stopping power of bombarding ions). Data on the GaAs and GaP crystals suggest that low temperature recovery stage defects produce major crystal distortion. The x-ray rocking curve technique with a dynamical diffraction theory analysis provides the depth distribution of the strain and damage in the MeV ion bombarded crystals.
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The work described in this thesis represents an attempt to summarize to date the information collected on the process of high energy heavy ion induced enhanced adhesion. Briefly, the process involves the irradiation of materials covered by thin (≾3μm) films with high energy (E > 200 keV I nucleon) heavy ion beams (such as Fluorine or Chlorine). Enhanced adhesion has been observed on all material combinations tested, including metal on metal, metal on semiconductor, metal on dielectric and dielectric on dielectric systems. In some cases, the enhancement can be quite large, so that a film that could be wiped off a substrate quite easily before irradiation can withstand determined scrubbing afterwards.
Very little is understood yet about this adhesion mechanism, so what is presented are primarily observations about systems studied, and descriptions of the actual preparation and irradiation of samples used. Some discussion is presented about mechanisms that have been considered but rejected.
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I. Nuclear magnetic resonance spectra of appropriately substituted ferrocenylcarbonium ions reveal the α-protons of the substituted ring to be more shielded than β-protons. The observation is discussed in terms of various models proposed for the ferrocenylcarbonium ion and is found to support a model in which the iron is bonded to all six carbona of the substituted ring.
II. Ferrocene catalyzes the photoisomerization of the piperylenes and the photodimerization of isoprene. Our results suggest a mechanism in which a complex of ferrocene and diene is excited to its second singlet state which dissociates to a triplet-state ferrocene molecule and a triplet-state diene molecule. The triplet-state diene, then, proceeds to isomerize or attack ground-state diene to form dimers.