Science & Mathematics

Excessive cellular oxidative stress is widely perceived as a key factor in pathophysiological conditions and cancer development. Healthy cells use several mechanisms to maintain intracellular levels of reactive oxygen species (ROS) and overall redox homeostasis to avoid damage to DNA, proteins, and lipids. Cancer cells, in contrast, exhibit elevated ROS levels and upregulated protective antioxidant pathways. Counterintuitively, such elevated oxidative stress and enhanced antioxidant defence mechanisms in cancer cells provide a therapeutic opportunity for the development of drugs with different anticancer mechanisms of action (MoA). In this review, oxidative stress and the role of ROS in cells are described. The tumour-suppressive and tumour-promotive functions of ROS are discussed to compare these two different therapeutic strategies (increasing or decreasing ROS to fight cancer). Clinically approved drugs with demonstrated oxidative stress anticancer MoAs are highlighted before describing examples of metal-based anticancer drug candidates causing oxidative stress in cancer cells via novel MoAs

Like other highly urbanized and industrialized estuaries, the Seine estuary (France) has, for decades, received high inputs of polycyclic aromatic hydrocarbons (PAHs). In order to estimate the bioremediation potentials and to identify the bacterial species involved in hydrocarbon degradation, we used microcosms containing seawater from the Seine estuary supplemented with either naphthalene, phenanthrene, fluorene or pyrene. In the microcosms enriched with naphthalene or phenanthrene, hydrocarbon biodegradation was significant within 9 weeks (43% or 46%, respectively), as shown by analyses in GC-MS. In similar microcosms incubated also with naphthalene or phenanthrene, analysis of the 16S rRNA gene sequences (DNA and cDNA) with denaturing gradient gel electrophoresis and clone libraries indicated that the PAH-degrading communities were dominated by Cycloclasticus spp., confirming their universal key role in degradation of lowmolecular- weight PAHs in marine environments. However, in contrast to previous studies, we found that Pseudomonas spp. also degraded naphthalene and phenanthrene in seawater; this occurred only after 21 days, as was confirmed by real-time PCR. Although this genus has been abundantly described in the literature as a good PAH-degrading bacterial group in soil or in sediment, to our knowledge, this is the first evidence of a significant fitness in PAH degradation in seawater.

The preparation of hydrogenated, r.f. sputtered a-Si films, suitable for large area solar cell arrays is discussed. Optical and electrical measurements on such materials contacted with a variety of metals are detailed. Initial experimental prototype cells, with areas up to 1 cm2 and efficiencies of around 2 %, are described.

Nous étudions le problème de diffusion inverse et un problème inverse de valeurs au bord pour l'équation de Newton-Einstein pluridimensionnelle décrivant le mouvement d'une particule classique relativiste dans un champ externe électromagnétique (ou gravitationnel) statique. Le cas d'une particule classique non relativiste est aussi considéré. Nous supposons que le champ externe est suffisamment régulier et suffisamment décroissant à l'infini. Tout d'abord on rappelle (et on développe) des résultats donnant l'existence et des propriétés de l'opérateur de diffusion. Puis on obtient, en particulier, l'asymptotique aux hautes énergies de l'opérateur de diffusion, et on montre que cette asymptotique détermine de manière unique (par des formules explicites) le champ externe. Enfin on obtient un théorème d'unicité à énergie fixée pour le problème inverse de valeurs au bord, et on en déduit, en particulier, qu'à énergie fixée suffisamment grande l'opérateur de diffusion détermine de manière unique le champ externe lorsque celui-ci est aussi supposé à support compact. Les résultats de cette thèse ont été obtenus en développant, en particulier, des méthodes de [Gerver-Nadirashvili, 1983] et [R. Novikov, 1999].

Here, we propose a novel microfluidic system to investigate the response of the neurons directly stimulated by the potassium ions in vitro. Unlike the conventional way of stimulating neurons by pipetting or sending electrical stimulus, this biomimetic stimulation system enables precise and rapid control of ion concentration by utilizing microfluidic pneumatic valves, which mimics physiological stimulation in a body. By using the system, we demonstrated stimulations of the neuron cells with potassium ions and monitored neural activities with a calcium-specific fluorescence indicator.

Bioelectronic medicine aims at developing devices capable to deliver an electric therapy by stimulating the target organ in a controlled way, possibly with less side effects than standard pharmaceutical therapy. Neural stimulators and implantable systems exploit the bioelectronic technology to reduce neurological impairments. Here we present the prototype of a bi-directional brain prosthesis capable to restore the communication between damaged in vitro neuronal networks.

This paper discusses the concept of public value in relation to government ICT investment from three perspectives - theory foundations, assessment methods, and an application example. The discussion of theory foundations combines attention to the roots of the concept of public value in political philosophy and public administration. The origins of the concept of public value are discussed in terms of foundational ideas in political and moral philosophy about the nature of the good society: utilitarianism and the social contract. The concern with public value, or utility, in early Western moral and political philosophy is central to the two major schools of thought, utilitarian and social contractarian. The social order that produces the greatest good or utility for the greatest number is preferred in the utilitarian perspective. The contractarian view holds that a good society should be based on shared principles and arrangements that avoid the potential evils of unconstrained greed. Though these two views political and moral philosophy differ, they weave similar connections among the basic concept of value, individual interests, societal interests, and institutional forms. These concepts and connections are basic to the public value framework. The framework links value to the workings of government in terms of individual and group interests in relation to government policies and programs. this view is reflected in recent thinking in public administration, particularly in the public value program described by Moore (1995). In Moore's terms, "value is rooted in the desires and perceptions of individuals--not necessarily in physical transformations, and not abstractions called societies." (p. 52) Moore includes both public sector production, i.e., "things of value to particular clients and beneficiaries," and "establishing and operating an institution that meets citizens' (and their representatives') desires for properly ordered and productive public institutions." (Moore, 1995:53) These foundational ideas then form the basis for an assessment method and framework designed to operationalize and provide useful data about the public value outcomes of government investment decisions. The paper presents a description of the assessment framework, followed by an example of how the method applies to a specific ICT investment in a government human service program. A discussion of the implications of the public value framework for investment and performance assessment concludes the paper.

The aim of this paper is to describe the modelling methods of the vertical channel MOS transistor (V. MOS) under DC and small signal HF conditions. By taking into account the scattering velocity saturation mechanisms, it will primarily be shown that (i) the drain current-gate voltage transfer characteristic becomes linear and (ii) the dynamic HF parameters are independent of the gate-source voltage. Moreover it will appear that the maximum working frequencies cannot overcome the UHF range.

absent

The objective of this work is to compare anatomical measurements to wood density variations within annual rings of three major softwood species, Norway spruce, Scots Pine and Silver Fir. The six selected annual rings were sampled within a database of thousand microdensitometric profiles measured on wood samples collected in Finland and France. Each of the six studied annual rings represents one average profile of wood density for a given age class and age ring width. The dimensions of the tracheids are performed in the radial-tangential plane by using two different planimetric methods. The wood density profile within each ring is calculated simply by the mean of the tracheid dimensions and by using a constant value for the cell wall density. We have verified that the knowledge of the (i) tracheid geometry and (ii) the usually admitted value of the cell wall density allows us to calculate intra ring wood density profiles which are similar to the X-rays wood density profiles in terms of variations but very different in average. Thus it appears necessary to calibrate by using an apparent cell wall density varying inside the rings and being far weaker than the effective cell wall density of 1460 kg/m³ as it is usually admitted in the literature.

Dans ce rapport, nous présentons l’architecture de MadKit (pour “Multi-Agent Development Kit”), une plate-forme générique de conception et d’exécution de systèmes multi-agents. Cette plate-forme a l’originalité d’être basé sur un modèle organisationnel plutôt qu’une architecture d’agent ou un modèle d’interaction spécifique. L’utilisation de groupes et de roles associés à des agents est mis en oeuvre tant en tant qu’outil de modèlisation et de conception pour les développeurs de systèmes multi-agents, que de principe d’architecture de la plate-forme elle-même. Cette architecture est basée sur un noyau agent minimal découplé de tout modèle individuel d’agent. Dans cette plate-forme, les services classiques de passage de message distribués, de migration ou de surveillance sont fournis au meta-niveau par des agents spécialisés afin d’obtenir un maximum de flexibilité. Une interface graphique componentielle et découplée du noyau et des agents permets de supporter différentes modes d’utilisation et d’exploitation de la plate-forme. Nous illustrons notre propos en présentant certaines conséquences et déclinaisons de cette plateforme, ainsi que quelques applications construites avec MadKit.

Il s'agit du travail d'une illustratrice représentant une recherche en menée par le CREAD (Centre de recherche sur l'éducation, les apprentissages et la didactique). L'objectif est de présenter les différentes étapes de la recherche à travers des illustrations.

La première partie de la thèse consiste en un article publié (IEEE Trans. Aut. Control Vol. AC 28, n° 9, 1983), avec J.C. Fort et G. Malgouyres, qui propose deux méthodes d'évaluation du temps de sortie d'un bassin d'attraction pour une chaîne de Markov : ce temps étant extrêmement grand, on utilise pour cela un changement de probabilité exponentiel tant pour une méthode de simulation rapide que pour une approximation diffusion non standard. La deuxième partie comprend deux articles publiés avec J.C. Fort (Annales de l'IHP Probabilités et Statistiques vol. 23, n° 1, 1987) et Biological Cybernetics (N° 53, 1986). Le premier donne une démonstration de la convergence de l'algorithme d'auto-organisation de Kohonen en dimension 1. Dans le second, nous définissons un algorithme d'auto-organisation qui est une version simplifiée de celui de Kohonen, et nous démontrons sa convergence en dimensions 1 et 2. Dans la troisième partie, publiée dans Biological Cybernetics (n° 58, 1988) nous résolvons le problème du calcul de la matrice de connexions pour un réseau de neurones de type Mac Culloch et Pitts ou Hopfield, qui permette d'obtenir la plus grande attractivité possible, dans le cas de l'algorithme déterministe et de patrons non nécessairement orthogonaux. De plus nous calculons pour une matrice de connexion donnée l'attractivité de chaque patron mémorisé. La dernière partie est consacrée à l'étude du rôle de l'inhibition dans un réseau de neurones connectés aux plus proches voisins. Le modèle choisi est proche de la réalité biologique du cortex cérébelleux chez le jeune animal. On montre que tant que l'inhibition est plus faible qu'un certain seuil, le réseau est ergodique et que s'installe rapidement un régime stationnaire. Au contraire, lorsque l'inhibition s'accroît, on provoque des réponses en bandes ou moirures, dont la forme et la largeur dépendent du type de voisinage considéré.

Introduction and statement of the research questions: Gap dynamics have been widely studied in forests of Abies spp. from temperate and boreal regions. The local microclimate and competition for light have been identified as the main factors controlling changes in species composition and canopy structure, however little is known on dynamics of such forests in Mediterranean.* Experimental design and aims: We studied forest structure and dynamics of Abies pinsapo stands in southern Spain, in contrasting habitats and successional status. In addition past regeneration patterns and their relationship to canopy structure, disturbances and forest-use history were investigated.* Results: Stands structure attributes were within the range described for temperate conifer biomes. The age structure revealed two main cohorts comprised of a few > 100 year-old trees and abundant younger trees established in a single recruitment event after the stands were protected in the 1950s. Initial growth-rate analyses indicated that A. pinsapo regenerated mainly in small canopy gaps, while only 15% recruited from the forest understorey. For the last ten years, basal area increment was lower than 10 cm2y−1 in 91% of studied trees and growth rate differences between trees narrowed.* Conclusion: Stand dynamics in A. pinsapo forests maintain general features of temperate fir forests. Tree establishment over time and current stand structure fit to known changes in forest use. Widespread growth decline trends might be linked to stand stagnation and global warming.