Early stages of the HFCVD process on multi-vicinal silicon surfaces studied by electron microscopy probes (SEM, TEM)

In this paper, we show that silicon dimples are suitable samples to study diamond nucleation on a controlled distribution of defects by SEM FEG and HRTEM observations. Indeed, multi-vicinal surfaces generated by a UHV thermal treatment have been characterised by STM experiments. On these terraces, we observed a strong increase of the nucleation density higher than two orders of magnitude compared to pristine silicon samples. Moreover, a preferential location of diamond nuclei along the steps is reported. This result is explained by the large surface diffusion length of carbon species compared to the terrace's width. Indeed, during the early stages of growth, oriented silicon carbide nano-crystals are observed with the relationship SiC(220)//Si(220)

Recommandations pour l’utilisation de la toxine botulinique de type A (Botox®) dans l’hyperactivité vésicale réfractaire idiopathique

RésuméObjectifsDéfinir des recommandations pour l’utilisation pratique de la toxine botulinique de type A (BoNTA) dans l’hyperactivité vésicale réfractaire idiopathique (HAVRI).MéthodeÉlaboration de recommandations de bonne pratique par consensus formalisé, validées par un groupe de 13 experts puis par un groupe de lecture indépendant.RésultatsEn cas d’infection urinaire celle-ci doit être traitée et l’injection reportée. Avant l’injection, il est recommandé de s’assurer de la faisabilité et de l’acceptabilité de l’auto-sondage. L’injection peut être réalisée après une anesthésie locale urétro-vésicale (lidocaïne), éventuellement complétée par l’inhalation de protoxyde d’azote et parfois sous anesthésie générale. L’injection sera réalisée au bloc opératoire ou en salle d’endoscopie. La vessie ne doit pas être trop remplie (risque de perforation). Le traitement doit être appliqué en 10 à 20 injections de 0,5 à 1mL réparties de manière homogène dans la vessie en restant à distance des méats urétéraux. Il n’est pas recommandé de laisser en place une sonde vésicale sauf en cas d’hématurie importante. Le patient doit être surveillé jusqu’à la reprise mictionnelle. Une note d’information sur les effets indésirables éventuels doit lui être remise à sa sortie. Une consultation doit être prévue 3 mois après la première injection (calendrier mictionnel, débitmétrie, résidu post-mictionnel et examen cytobactériologique des urines). Un résidu >200mL et/ou symptomatique doit faire discuter des auto-sondages. Une nouvelle injection pourra être envisagée lorsque le bénéfice clinique de la précédente s’estompe (entre 6 et 9 mois).ConclusionsLe respect de ces recommandations devrait permettre une utilisation optimale de la BoNTA.Niveau de preuve3.SummaryObjectivesProvide guidelines for practical usage of botulinum toxin type A (BoNTA) for refractory idiopathic Overactive Bladder management.Patients and methodsGuidelines using formalized consensus guidelines method. These guidelines have been validated by a group of 13 experts quoting proposals, subsequently reviewed by an independent group of experts.ResultsIn the case of patients with urinary tract infection, it must be treated and injection postponed. Before proposing an injection, it is recommended to ensure the feasibility and acceptability of self-catheterisation by patient. The injection can be performed after local anesthesia of the bladder and urethra (lidocaine), supplemented where necessary by nitrous oxide inhalation and sometimes under general anesthesia. Injection is performed in the operating room or endoscopy suite. The bladder should not be too filled (increased risk of perforation). Treatment should be applied in 10 to 20 injections of 0.5 to 1mL homogeneously distributed in the bladder at a distance from the urethral orifices. It is not recommended to leave a urinary catheter in place except in cases of severe hematuria. The patient should be monitored until resumption of micturition. After the first injection, an appointment must be scheduled within 3 months (micturition diary, uroflowmetry, measurement of residual urine and urine culture). Performance of self-catheterisation should be questioned in the case of a symptomatic post-void residual and/or a residue>200mL. A new injection may be considered when the clinical benefit of the previous injection diminishes (between 6 and 9 months). A period of three months must elapse between each injection.ConclusionsImplementation of these guidelines may promote best practice usage of BoNTA with optimal risk/benefit ratio

Weak localization and interaction effects in acceptor graphite intercalation compounds

The presented work is devoted to investigations of manifestation of quantum effects of weak localization and interaction of charge carriers in electrical conductivity of acceptor graphite intercalation compounds (CICs). As shown by studies intercalation leads to a decrease in the resistivity and to change the resistivity temperature coefficient from negative sign in the source graphite on a positive sign in intercalated graphite. At the low temperature for all GICs specimens the minimum in the temperature dependence of resistivity is observed. In terms of the model of charge carrier's weak localization and interaction for two-dimensional systems temperature dependence of phase relaxation time, localization radius and charge carriers screening constant for all GICs are estimated

Variational theory of elastic manifolds with correlated disorder and localization of interacting quantum particles

We apply the gaussian variational method (GVM) to study the equilibrium statistical mechanics of the two related systems: (i) classical elastic manifolds, such as flux lattices, in presence of columnar disorder correlated along the $\tau$ direction (ii) interacting quantum particles in a static random potential. We find localization by disorder, the localized phase being described by a replica symmetry broken solution confined to the mode $\omega=0$. For classical systems we compute the correlation function of relative displacements. In $d=2+1$, in the absence of dislocations, the GVM allows to describes the Bose glass phase. Along the columns the displacements saturate at a length $l_{\perp}$ indicating flux-line localization. Perpendicularly to the columns long range order is destroyed. We find divergent tilt modulus $c_{44}=\infty$ and a $x \sim \tau^{1/2}$ scaling. Quantum systems are studied using the analytic continuation from imaginary to real time $\tau \to i t$. We compute the conductivity and find that it behaves at small frequency as $\sigma(\omega) \approx \omega^2$ in all dimensions ($d < 4$) for which disorder is relevant. We compute the quantum localization length $\xi$. In $d=1$, where the model also describes interacting fermions in a static random potential, we find a delocalization transition and obtain analytically both the low and high frequency behavior of the conductivity for any value of the interaction. We show that the marginality condition appears as the condition to obtain the correct physical behavior. Agreement with renormalization group results is found whenever it can be compared.Comment: 34 pages, REVTeX, no figure

Evidence for Spinodal Decomposition in Nuclear Multifragmentation

Multifragmentation of a ``fused system'' was observed for central collisions between 32 MeV/nucleon 129Xe and natSn. Most of the resulting charged products were well identified thanks to the high performances of the INDRA 4pi array. Experimental higher-order charge correlations for fragments show a weak but non ambiguous enhancement of events with nearly equal-sized fragments. Supported by dynamical calculations in which spinodal decomposition is simulated, this observed enhancement is interpreted as a ``fossil'' signal of spinodal instabilities in finite nuclear systems.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Letter

Quantum and thermal ionic motion, oxygen isotope effect, and superexchange distribution in La₂CuO₄

We study the zero-point and thermal ionic motion in La$_2$CuO$_4$ by means of high-resolution neutron diffraction experiments. Our results demonstrate anisotropic motion of O and to a lesser extent of Cu ions, both consistent with the structure of coupled CuO$_6$ octahedra, and quantify the relative effects of zero-point and thermal contributions to ionic motion. By substitution of $^{18}$O, we find that the oxygen isotope effect on the lattice dimensions is small and negative ($-0.01\%$), while the isotope effect on the ionic displacement parameters is significant ($-6$ to $50\%$). We use our results as input for theoretical estimates of the distribution of magnetic interaction parameters, $J$, in an effective one-band model for the cuprate plane. We find that ionic motion causes only small ($1\%$) effects on the average value $\langle J\rangle$, which vary with temperature and O isotope, but results in dramatic ($10$-$20\%$) fluctuations in $J$ values that are subject to significant ($8$-$12\%$) isotope effects. We demonstrate that this motional broadening of $J$ can have substantial effects on certain electronic and magnetic properties in cuprates.Comment: 13 pages, 9 figure

Dynamical effects in multifragmentation at intermediate energies

The fragmentation of the quasi-projectile is studied with the INDRA multidetector for different colliding systems and incident energies in the Fermi energy range. Different experimental observations show that a large part of the fragmentation is not compatible with the statistical fragmentation of a fully equilibrated nucleus. The study of internal correlations is a powerful tool, especially to evidence entrance channel effects. These effects have to be included in the theoretical descriptions of nuclear multifragmentation.Comment: 13 pages, 26 figures, submitted to Physical Review

Response of CsI(Tl) scintillators over a large range in energy and atomic number of ions (Part I): recombination and delta -- electrons

A simple formalism describing the light response of CsI(Tl) to heavy ions, which quantifies the luminescence and the quenching in terms of the competition between radiative transitions following the carrier trapping at the Tl activator sites and the electron-hole recombination, is proposed. The effect of the delta rays on the scintillation efficiency is for the first time quantitatively included in a fully consistent way. The light output expression depends on four parameters determined by a procedure of global fit to experimental data.Comment: 28 pages, 6 figures, submitted to Nucl. Inst. Meth.

Elastic theory of flux lattices in presence of weak disorder

The effect of disorder on flux lattices at equilibrium is studied quantitatively in the absence of free dislocations using both the Gaussian variational method and the renormalization group. Our results for the mean square relative displacements clarify the nature of the crossovers with distance. We find three regimes: (i) a short distance regime (``Larkin regime'') where elasticity holds (ii) an intermediate regime (``Random Manifold'') where vortices are pinned independently (iii) a large distance, quasi-ordered regime where the periodicity of the lattice becomes important and there is universal logarithmic growth of displacements for $2<d<4$ and persistence of algebraic quasi-long range translational order. The functional renormalization group to $O(\epsilon=4-d)$ and the variational method, agree within $10\%$ on the value of the exponent. In $d=3$ we compute the crossover function between the three regimes. We discuss the observable signature of this crossover in decoration experiments and in neutron diffraction experiments on flux lattices. Qualitative arguments are given suggesting the existence for weak disorder in $d=3$ of a `` Bragg glass '' phase without free dislocations and with algebraically divergent Bragg peaks. In $d=1+1$ both the variational method and the Cardy-Ostlund renormalization group predict a glassy state below the same transition temperature $T=T_c$, but with different behaviors. Applications to $d=2+0$ systems and experiments on magnetic bubbles are discussed.Comment: 59 pages; RevTeX 3.0; 5 postscript figures uuencode

Multifragmentation process for different mass asymmetry in the entrance channel around the Fermi energy

The influence of the entrance channel asymmetry upon the fragmentation process is addressed by studying heavy-ion induced reactions around the Fermi energy. The data have been recorded with the INDRA 4pi array. An event selection method called the Principal Component Analysis is presented and discussed. It is applied for the selection of central events and furthermore to multifragmentation of single source events. The selected subsets of data are compared to the Statistical Multifragmentation Model (SMM) to check the equilibrium hypothesis and get the source characteristics. Experimental comparisons show the evidence of a decoupling between thermal and compresional (radial flow) degrees of freedom in such nuclear systems.Comment: 28 pages, 15 figures, article sumitted to Nuclear Physics