Interference and Interaction in Multiwall Carbon Nanotubes

We report equilibrium electric resistance R and tunneling spectroscopy dI/dV measurements obtained on single multiwall nanotubes contacted by four metallic Au fingers from above. At low temperature quantum interference phenomena dominate the magnetoresistance. The phase-coherence and elastic-scattering lengths are deduced. Because the latter is of order of the circumference of the nanotubes, transport is quasi-ballistic. This result is supported by a dI/dV spectrum which is in good agreement with the density-of-states (DOS) due to the one-dimensional subbands expected for a perfect single-wall tube. As a function of temperature T the resistance increases on decreasing T and saturates at approx. 1-10 K for all measured nanotubes. R(T) cannot be related to the energy-dependent DOS of graphene but is mainly caused by interaction and interference effects. On a relatively small voltage scale of order 10 meV, a pseudogap is observed in dI/dV which agrees with Luttinger-Liquid theories for nanotubes. Because we have used quantum diffusion based on Fermi-Liquid as well as Luttinger-Liquid theory in trying to understand our results, a large fraction of this paper is devoted to a careful discussion of all our results.Comment: 14 pages (twocolumn), 8 figure

Newer Intraocular Pressure Measurement Techniques

An elevated intraocular pressure (IOP) has been shown to be one of the major risk factors for glaucoma. It is of utmost importance to obtain accurate and precise IOP when dealing with patients with ocular hypertension and glaucoma, especially patients who have undergone ocular surgery. Goldmann applanation tonometer (GAT) was first introduced in the 1950s and is still currently considered as the gold standard to measure IOP. Although the reproducibility of GAT has shown to be quite good, its accuracy provides several limitations. In particular, IOP measurements taken with GAT have been demonstrated to be influenced by many corneal parameters, including central thickness, curvature, astigmatism and biomechanics. Other disadvantages of GAT include the need for local anesthetic drops, for fluorescein and for a slitlamp. Several different methods have been proposed to overcome the disadvantages found in GAT. The newer devices used as alternative tonometric methods include the iCare rebound tonometer, the BioResonator applanation resonance tonometer, the Pascal dynamic contour tonometer, the ocular response analyzer, the Corvis ST pachy-tonometer and Ocuton S. The precision and accuracy of these alternative tonometric methods in comparison with GAT have been reported and discussed

Qui sont les repreneurs potentiels d’entreprises ? Proposition de typologie en fonction de l’état de santé de la firme

La question de recherche est la suivante : selon l’état de santé de la firme, quelles sont les caractéristiques des repreneurs potentiels ? Cet article vise à déterminer s’il est possible de caractériser les repreneurs potentiels et à établir qui sont les acteurs capables de reprendre certaines catégories d’entreprises. Les réponses apportées ici peuvent s’avérer particulièrement pertinentes pour les institutionnels en charge du développement économique de leurs territoires (CCI, incubateurs, pôles de compétitivité, etc.). Cette recherche repose sur une enquête menée en 2008 auprès de 44 porteurs de projet de reprise du Languedoc-Roussillon. Les résultats de la recherche, issus d’une analyse typologique, montrent que trois groupes de repreneurs potentiels se profilent : les prudents, les indifférents et les aventuriers. D’un point de vue managérial, cette recherche contribue à une meilleure connaissance des repreneurs potentiels et permet d’améliorer leur accompagnement dans leur démarche de reprise.The research question is the following one : according to the firm’s health, what are the features of management buy-in realized by individuals ? The goal of this article is double : to characterize individuals who want to buy-in companies, and to understand who are the people able to buy-in specific companies. The strength of this study is to propose contributions to help public and private actors who have in charge development of their territory (for example, chamber of commerce). The sample is composed of 44 individuals who have a project of management buy-in in the Languedoc Roussillon area. Thanks to a typological analysis, three types of entrepreneurs are identified : the adventurous, cautious and indifferent managers. On a managerial point of view, this research contributes to a better knowledge of potential manager buy-in in order to help them to develop their projects.La cuestión de investigación es la siguiente : ¿ según el estado de salud de la empresa, cuáles son las características de las personas que se hace cargo de la empresa en crisis potenciales ? Este artículo tiene por objeto determinar si es posible caracterizar las personas que se hace cargo de la empresa en crisis potenciales, y a incluir que son los protagonistas capaces reanudar algunas categorías de empresas. Las respuestas establecidas aquí pueden resultar especialmente pertinentes para institucionales en carga del desarrollo económico de sus territorios (CCI, incubadoras, polos de competitividad, etc.). Esta investigación se basa en una investigación realizada en 2008 ante 44 portadores de proyecto de reanudación del Languedoc-Roussillon. Los resultados de la investigación, resultantes de un análisis tipológico, ponen de manifiesto que tres grupos de personas que se hace cargo de la empresa en crisis potenciales aparecen : los prudentes, los indiferentes y los aventureros. Desde un punto de vista de gestión, esta investigación contribuye a un mejor conocimiento de las personas que se hace cargo de la empresa en crisis potenciales con el fin de mejorar su acompañamiento en su planteamiento de reanudación.Die Forschungsfrage lautet : Kann aufgrund des Zustandes eines Unternehmens auf die Eigenschaften eines potenziellen Übernehmers geschlossen werden ? Ziel des vorliegenden Artikels ist die Diskussion der Frage, für welche Art von Unternehmen welche Nachfolger mit welchen Eigenschaften in Frage kommen. Die vorgeschlagenen Antworten sind besonders interessant für Institutionen, die in diesem Bereich tätig sind. Diese Forschung basiert auf einer Umfrage aus dem Jahre 2008 bei 44 Projektverantwortlichen für geplante Übernahmen im Languedoc-Roussillon. Die Cluster-Analyse ergab drei Gruppen von potenziellen Übernehmern : die Vorsichtigen, die Gleichgültigen und die Abenteurer. Aus betriebswirtschaftlicher Sicht trägt diese Forschung zu einem besseren Verständnis der potenziellen Übernehmer bei, um die Unterstützung im Übernahmeprozess zu verbessern

Force Chains, Microelasticity and Macroelasticity

It has been claimed that quasistatic granular materials, as well as nanoscale materials, exhibit departures from elasticity even at small loadings. It is demonstrated, using 2D and 3D models with interparticle harmonic interactions, that such departures are expected at small scales [below O(100) particle diameters], at which continuum elasticity is invalid, and vanish at large scales. The models exhibit force chains on small scales, and force and stress distributions which agree with experimental findings. Effects of anisotropy, disorder and boundary conditions are discussed as well.Comment: 4 pages, 11 figures, RevTeX 4, revised and resubmitted to Phys. Rev. Let

Qui sont les repreneurs potentiels d’entreprises ? Proposition de typologie en fonction de l’état de santé de la firme

La question de recherche est la suivante : selon l’état de santé de la firme, quelles sont les caractéristiques des repreneurs potentiels ? Cet article vise à déterminer s’il est possible de caractériser les repreneurs potentiels et à établir qui sont les acteurs capables de reprendre certaines catégories d’entreprises. Les réponses apportées ici peuvent s’avérer particulièrement pertinentes pour les institutionnels en charge du développement économique de leurs territoires (CCI, incubateurs, pôles de compétitivité, etc.). Cette recherche repose sur une enquête menée en 2008 auprès de 44 porteurs de projet de reprise du Languedoc-Roussillon. Les résultats de la recherche, issus d’une analyse typologique, montrent que trois groupes de repreneurs potentiels se profilent : les prudents, les indifférents et les aventuriers. D’un point de vue managérial, cette recherche contribue à une meilleure connaissance des repreneurs potentiels et permet d’améliorer leur accompagnement dans leur démarche de reprise.The research question is the following one : according to the firm’s health, what are the features of management buy-in realized by individuals ? The goal of this article is double : to characterize individuals who want to buy-in companies, and to understand who are the people able to buy-in specific companies. The strength of this study is to propose contributions to help public and private actors who have in charge development of their territory (for example, chamber of commerce). The sample is composed of 44 individuals who have a project of management buy-in in the Languedoc Roussillon area. Thanks to a typological analysis, three types of entrepreneurs are identified : the adventurous, cautious and indifferent managers. On a managerial point of view, this research contributes to a better knowledge of potential manager buy-in in order to help them to develop their projects.La cuestión de investigación es la siguiente : ¿ según el estado de salud de la empresa, cuáles son las características de las personas que se hace cargo de la empresa en crisis potenciales ? Este artículo tiene por objeto determinar si es posible caracterizar las personas que se hace cargo de la empresa en crisis potenciales, y a incluir que son los protagonistas capaces reanudar algunas categorías de empresas. Las respuestas establecidas aquí pueden resultar especialmente pertinentes para institucionales en carga del desarrollo económico de sus territorios (CCI, incubadoras, polos de competitividad, etc.). Esta investigación se basa en una investigación realizada en 2008 ante 44 portadores de proyecto de reanudación del Languedoc-Roussillon. Los resultados de la investigación, resultantes de un análisis tipológico, ponen de manifiesto que tres grupos de personas que se hace cargo de la empresa en crisis potenciales aparecen : los prudentes, los indiferentes y los aventureros. Desde un punto de vista de gestión, esta investigación contribuye a un mejor conocimiento de las personas que se hace cargo de la empresa en crisis potenciales con el fin de mejorar su acompañamiento en su planteamiento de reanudación.Die Forschungsfrage lautet : Kann aufgrund des Zustandes eines Unternehmens auf die Eigenschaften eines potenziellen Übernehmers geschlossen werden ? Ziel des vorliegenden Artikels ist die Diskussion der Frage, für welche Art von Unternehmen welche Nachfolger mit welchen Eigenschaften in Frage kommen. Die vorgeschlagenen Antworten sind besonders interessant für Institutionen, die in diesem Bereich tätig sind. Diese Forschung basiert auf einer Umfrage aus dem Jahre 2008 bei 44 Projektverantwortlichen für geplante Übernahmen im Languedoc-Roussillon. Die Cluster-Analyse ergab drei Gruppen von potenziellen Übernehmern : die Vorsichtigen, die Gleichgültigen und die Abenteurer. Aus betriebswirtschaftlicher Sicht trägt diese Forschung zu einem besseren Verständnis der potenziellen Übernehmer bei, um die Unterstützung im Übernahmeprozess zu verbessern

Retour sur l’expérimentation de fusion des programmes de SES et de PFEG en seconde : dans quelle mesure la mutualisation des cours a affecté les conditions d’exercice de ma pratique professionnelle ?

Au sein de l’établissement, un seul enseignement d’exploration à dominante économique est proposé aux élèves et se nomme Découverte du Monde Économique et Social (DMES). Il est présenté comme une fusion des programmes de SES et de PFEG tant sur les savoirs, et savoir-faire abordés que sur les pratiques pédagogiques mises en place.Ce projet a été l’occasion de mutualiser la création de cours. L’équipe enseignante de SES s’est réparti la création des chapitres de ce nouvel enseignement d’exploration. Par conséquent, les enseignantes (l’équipe de SES du lycée est uniquement constitué de femmes) et moi-même avons dû nous approprier des supports de cours qui n’étaient pas les nôtres.L’appropriation des cours est une tâche difficile surtout pour un enseignant débutant. En plus d’être une tâche difficile, cette pratique soulève de nombreuses questions de l’ordre de l’appropriation. Peut-on s’approprier (totalement) un cours ? Comment réussir à s’approprier un cours ? Quel impact peuvent avoir des cours clefs en main sur la pratique professionnelle d’un enseignant débutant ? Ce travail sera l’occasion de présenter cette expérimentation. Dans un second temps, un retour critique de la participation à cette expérimentation sera exposé et enfin, dans un troisième temps, l’impact de la mutualisation des cours clefs en main sur la pratique professionnelle et sur l’évolution des croyances en tant qu’enseignant débutant seront étudiés

Non-Arteritic Anterior Ischemic Optic Neuropathy (NA-AION): A Comprehensive Overview

Non-arteritic anterior ischemic optic neuropathy (NA-AION) represents one of the most important causes of blindness or severely impaired vision in middle-aged and elderly people. Unilateral optic disc edema and abrupt, painless vision loss are its defining features. It is commonly assumed that NA-AION is caused by an ischemic infarction of the optic nerve head, and, although the exact pathogenesis is still unknown, several risk factors and comorbidities associated with its development have been found. NA-AION occurs generally in patients older than 50 years who have small optic discs and vasculopathy risk factors. Even though numerous treatment options have been proposed, no available effective medical or surgical therapy or prophylactic measure for NA-AION currently exists. The purpose of present-day therapeutic strategies is therefore to identify and possibly control any underlying modifiable risk factors, aiming to prevent the development of new NA-AION episodes in the affected and fellow eye. A thorough assessment of NAION, including its history, epidemiology, etiology, pathophysiology, risk factors, associated comorbidities, clinical findings, diagnostic tests, treatment choices, prognosis, and future research, is the goal of this work

Pharmaceutical approaches to normal tension glaucoma

Normal tension glaucoma (NTG) is defined as a subtype of primary open-angle glaucoma (POAG) in which the intraocular pressure (IOP) values are constantly within the statistically normal range without treatment and represents approximately the 30-40% of all glaucomatous cases. The pathophysiology of this condition is multifactorial and is still not completely well known. Several theories have been proposed to explain the onset and progression of this disease, which can be divided into IOP-dependent and IOP-independent factors, suggesting different therapeutic strategies. The current literature strongly supports the fundamental role of IOP in NTG. The gold standard treatment for NTG tends to be based on the lowering IOP even if "statistically normal". Numerous studies have shown, however, that the IOP reduction alone is not enough to slow down or stop the disease progression in all cases, suggesting that other IOP-independent risk factors may contribute to the NTG pathogenesis. In addition to IOP-lowering strategies, several different therapeutic approaches for NTG have been proposed, based on vaso-active, antioxidant, anti-inflammatory and/or neuroprotective substances. To date, unfortunately, there are no standardized or proven treatment alternatives for NTG when compared to traditional IOP reduction treatment regimes. The efficacy of the IOP-independent strategies in decreasing the risk or treating NTG still remains inconclusive. The aim of this review is to highlight strategies reported in the current literature to treat NTG. The paper also describes the challenges in finding appropriate and pertinent treatments for this potentially vision-threatening disease. Further comprehension of NTG pathophysiology can help clinicians determine when to use IOP-lowering treatments alone and when to consider additional or alternatively individualized therapies focused on particular risk factors, on a case-by-case basis

Nanoengineering Carbon Allotropes from Graphene

Monolithic structures can be built into graphene by the addition and subsequent re-arrangement of carbon atoms. To this end, ad-dimers of carbon are a particularly attractive building block because a number of emerging technologies offer the promise of precisely placing them on carbon surfaces. In concert with the more common Stone-Wales defect, repeating patterns can be introduced to create as yet unrealized materials. The idea of building such allotropes out of defects is new, and we demonstrate the technique by constructing two-dimensional carbon allotropes known as haeckelite. We then extend the idea to create a new class of membranic carbon allotropes that we call \emph{dimerite}, composed exclusively of ad-dimer defects.Comment: 5 pages, 5 figure

Comparative study of the catalytic growth of patterned carbon nanotube films

Three different catalysts (Fe, Ni, Co nitrates dissolved in ethanol) were patterned on a SiO2/Si substrate and multi-wall carbon nanotubes were grown by catalytic decomposition of acetylene. We compare the growth of the carbon nanostructures in the temperature range between 580C and 1000C. With our experimental set-up the catalyst solutions of cobalt and nickel were found to be less efficient than the one of iron. An optimal production of multi-wall nanotubes was observed at temperatures between 650C and 720C with the iron solution as catalyst. We found a tendency towards thicker structures with higher temperatures. Finally, we suggest a mechanism for the growth of these carbon structures.Comment: 5 pages, 5 figure