Dynamic Quantum Logic for Quantum Programs

We present a way to apply quantum logic to the study of quantum programs. This is made possible by using an extension of the usual propositional language in order to make transformations performed on the system appear explicitly. This way, the evolution of the system becomes part of the logical study. We show how both unitary operations and two-valued measurements can be included in this formalism and can thus be handled logically.Comment: Submitted to the International Journal of Quantum Informatio

Elastic properties of cellular dissipative structure

Transition towards spatio-temporal chaos in one-dimensional interfacial patterns often involves two degrees of freedom: drift and out-of-phase oscillations of cells, respectively associated to parity breaking and vacillating-breathing secondary bifurcations. In this paper, the interaction between these two modes is investigated in the case of a single domain propagating along a circular array of liquid jets. As observed by Michalland and Rabaud for the printer's instability \cite{Rabaud92}, the velocity $V_g$ of a constant width domain is linked to the angular frequency $\omega$ of oscillations and to the spacing between columns $\lambda_0$ by the relationship $V_g = \alpha \lambda_0 \omega$. We show by a simple geometrical argument that $\alpha$ should be close to $1/ \pi$ instead of the initial value $\alpha = 1/2$ deduced from their analogy with phonons. This fact is in quantitative agreement with our data, with a slight deviation increasing with flow rate

Dependence of DNA persistence length on ionic strength of solutions with monovalent and divalent salts: a joint theory-experiment study

Using high-throughput Tethered Particle Motion single molecule experiments, the double-stranded DNA persistence length, $L_p$, is measured in solutions with Na$^+$ and Mg$^{2+}$ ions of various ionic strengths, $I$. Several theoretical equations for $L_p(I)$ are fitted to the experimental data, but no decisive theory is found which fits all the $L_p$ values for the two ion valencies. Properly extracted from the particle trajectory using simulations, $L_p$ varies from 30~nm to 55~nm, and is compared to previous experimental results. For the Na$^+$ only case, $L_p$ is an increasing concave function of $I^{-1}$, well fitted by Manning's electrostatic stretching approach, but not by classical Odjik-Skolnick-Fixman theories with or without counter-ion condensation. With added Mg$^{2+}$ ions, $L_p$ shows a marked decrease at low $I$, interpreted as an ion-ion correlation effect, with an almost linear law in $I^{-1}$, fitted by a proposed variational approach

Light-controlled flows in active fluids

International audienceMany photosynthetic microorganisms are able to detect light and move toward optimal intensities. This ability, known as phototaxis, plays a major role in ecology by affecting natural phytoplankton mass transfers and has important applications in bioreactor and artificial microswimmers technologies. Here we show that this property can be exploited to generate macroscopic fluid flows using a localized light source directed toward shallow suspensions of phototactic microorganisms. Within the intensity range of positive phototaxis, algae accumulate beneath the excitation light where collective effects lead to the emergence of radially symmetric convective flows. These flows can thus be used as hydrodynamic tweezers to manipulate small floating objects. At high cell density and layer depth, we uncover a new kind of instability wherein the viscous torque exerted by self-generated fluid flows on the swimmers induces the formation of traveling waves. A model coupling fluid flow, cell concentration and orientation finely reproduces the experimental data

Irreversible Collective Migration of Cyanobacteria in Eutrophic Conditions

In response to natural or anthropocentric pollutions coupled to global climate changes, microorganisms from aquatic environments can suddenly accumulate on water surface. These dense suspensions, known as blooms, are harmful to ecosystems and significantly degrade the quality of water resources. In order to determine the physico-chemical parameters involved in their formation and quantitatively predict their appearance, we successfully reproduced irreversible cyanobacterial blooms in vitro. By combining chemical, biochemical and hydrodynamic evidences, we identify a mechanism, unrelated to the presence of internal gas vesicles, allowing the sudden collective upward migration in test tubes of several cyanobacterial strains (Microcystis aeruginosa PCC 7005, Microcystis aeruginosa PCC 7806 and Synechocystis sp. PCC 6803). The final state consists in a foamy layer of biomass at the air-liquid interface, in which micro-organisms remain alive for weeks, the medium lying below being almost completely depleted of cyanobacteria. These "laboratory blooms" start with the aggregation of cells at high ionic force in cyanobacterial strains that produce anionic extracellular polymeric substances (EPS). Under appropriate conditions of nutrients and light intensity, the high photosynthetic activity within cell clusters leads the dissolved oxygen (DO) to supersaturate and to nucleate into bubbles. Trapped within the EPS, these bubbles grow until their buoyancy pulls the biomass towards the free surface. By investigating a wide range of spatially homogeneous environmental conditions (illumination, salinity, cell and nutrient concentration) we identify species-dependent thresholds and timescales for bloom formation. We conclude on the relevance of such results for cyanobacterial bloom formation in the environment and we propose an efficient method for biomass harvesting in bioreactors.Comment: 16 Pages, 4 figure

Chartres – Terrain Doré

Date de l'opération : 1984 (SU) Inventeur(s) : Joly Dominique ; Brunet Philippe Cette intervention a permis d'observer, au sud de la ville [ (Fig. n°1 : Chartres : plan général. Localisation des principales fouilles et observations depuis 1979), site E] un tronçon fossé qui a ceinturé l'oppidum de Chartres à la fin de l'Âge du fer ou à l'Époque augustéenne, en protégeant un espace de près de 200 ha (Brunet, 1985 : 64-69) (Fig. n°2 : Localisation du site et de la circonvallation par rapport à..

Maximum size of drops levitated by an air cushion

Liquid drops can be kept from touching a plane solid surface by a gas stream entering from underneath, as it is observed for water drops on a heated plate, kept aloft by a stream of water vapor. We investigate the limit of small flow rates, for which the size of the gap between the drop and the substrate becomes very small. Above a critical drop radius no stationary drops can exist, below the critical radius two solutions coexist. However, only the solution with the smaller gap width is stable, the other is unstable. We compare to experimental data and use boundary integral simulations to show that unstable drops develop a gas "chimney" which breaks the drop in its middle.Comment: 13 pages, 11 figure

Les restes de l’industrie de l’uranium

L’industrie minière de l’uranium s’est déployée sur le territoire métropolitain entre 1948 et 2001, soit sur un demi-siècle. La région du Limousin a été la zone de production la plus importante, de l’extraction du minerai à sa concentration sur place en yellow cake. Il a résulté de cette industrie trois types de restes : les stériles, les résidus et les eaux d’exhaure. La masse très importante de ces restes, stériles et résidus, est liée à la richesse du minerai extrait et traité. Ils sont radioactifs avec une très faible activité. Mais, compte tenu de la décroissance de leur radioactivité, leur impact sur l’environnement peut être considéré comme infini à l’échelle du temps humain.À partir d’une enquête réalisée intensivement entre 1996 et 2002, puis de manière plus ponctuelle jusqu’à aujourd’hui, l’article examine l’évolution de la gestion de ces restes. Il prend appui sur la notion de capacité de prise en charge et sur une méthode sociohistorique adaptée. Cette articulation permet à l’analyse sociologique de montrer la plasticité de la capacité de prise en charge de ces restes à travers le temps long et non discontinu de l’exploitation à la post-exploitation. L’analyse se déploie sur trois périodes, qui sont autant de configurations sociales distinctes depuis 1948 jusqu’à aujourd’hui : le temps béni de l’uranium, le temps disputé du nucléaire et le temps incertain de la radioactivité. Elle montre que la capacité de prise en charge de ces restes se transforme lentement, passant de la modalité attribution à la nature, à la modalité disposition à, affaire pleinement humaine. Cette transformation est l’expression de l’évolution des rapports sociaux qui agitent chacune des configurations sociales. Ces rapports se nouent en particulier autour de l’identification et de la gestion de ces restes comme déchets radioactifs, l’une et l’autre tendues entre les réglementations minière et nucléaire. Dans une certaine mesure, le maintien de cette conflictualité qui traverse ces rapports sociaux est garant d’un pouvoir mémoriel relatif à l’incertitude de la situation.The mining industry of the uranium expanded on the metropolitan terrirory between 1948 and 2001, is over half a century. The region of Limousin was the zone of the most important production, the extraction of the ore in its on-the-spot concentration yellow cake. It resulted from this industry three types of remnants : the sterile, the residues and mine water. The very important mass of these remnants, sterile and residues, is bound to the wealth of extracted and handled ore. They are radioactive with one very low activity. But, considering the diminution of their radioactivity, their impact on the environment can be considered as infinity on the scale of human time.From a survey realized between 1996 and 2002, then in a more punctual way until today, the article examines the evolution of management of these remnants. It takes one’s stand the notion of carrying capacity and on a sociohistoric method adapted. This articulation allows the sociological analysis to show the plasticity of the carrying capacity of these remnants through the long and not discontinuous time since the exploitation until the post-exploitation. The analysis expand over three periods, which are so many different social configurations since 1948 until today : the blessed time of uranium, the nuclear discord time and the nuclear uncertainty of radioactivity time. It shows that the carrying capacity of these remnants is slowly transformed, crossing as the modality of attribution to the nature in the modality of arrangement to, completely human matter. This processing is the expression of the evolution of the social relationships which shake each of the social configurations. These relationships are formed in particular around the identification and the management of this remnants as radioactive waste, tightened between the regulations quarry and nuclear powers. To a certain extent, the preservation of this confliction which crosses these social relationships is a guarantor for a memory power concerning the uncertaintly of the situation