Geometry of color perception. Part 2: perceived colors from real quantum states and Hering's rebit

Inspired by the work of Resnikoff, which is described if full details in the first part of this two-part paper, we give a quantum description of the space P of perceived colors. We show that P is the effect space of a rebit, a real quantum qubit, whose state space S is isometric to the hyperbolic Klein disk K. This chromatic state space of perceived colors can be represented as a Bloch disk of real dimension 2 that coincides with the Hering disk given by the color opponency mechanism. Attributes of perceived colors, hue and saturation, are defined in terms of Von Neumann entropy

Spinor Fourier Transform for Image Processing

We propose in this paper to introduce a new spinor Fourier transform for both grey-level and color image processing. Our approach relies on the three following considerations: mathematically speaking, defining a Fourier transform requires to deal with group actions; vectors of the acquisition space can be considered as generalized numbers when embedded in a Clifford algebra; the tangent space of the image surface appears to be a natural parameter of the transform we define by means of so-called spin characters. The resulting spinor Fourier transform may be used to perform frequency filtering that takes into account the Riemannian geometry of the image. We give examples of low-pass filtering interpreted as diffusion process. When applied to color images, the entire color information is involved in a really non marginal process

Arcueil – 10 rue Paul-Vaillant-Couturier

Un diagnostic archéologique a eu lieu à l’emplacement des laboratoires de la société lnnothera du 18 mai au 7 juin 1998. Implanté à une soixantaine de mètres de la rive droite de la Bièvre canalisée, le site a été sondé en trois tranchées dont la localisation fut imposée par l’existence d’un bâtiment encore en élévation. Les trois tranchées ont révélé un mobilier céramique Bas-Empire et haut Moyen Âge, au sein de niveaux qui ne semblent pas perturbés. Parmi les structures découvertes, signalo..

Self-lubricating polymer composites : using numerical trbology to hightlight their design criterion

International audienceAfter the cessation of RT/Duroid 5813, manufacturing tests were performed by CNES and ESA/ESTL in order to find an alternative material. Although PGM-HT was selected as the best candidate, limitations about its tribological capabilities to replace RT/Duroid 5813 were later pointed out. Today, the predictability of the tribological behaviour of those materials is not fully overcome. The motivation to this work is to complement studies of self-lubricating materials by coupling experimental analyses with numerical modelling, in order to predict their tribological behaviour. A Discrete Element Method is chosen to construct the numerical material, because it allows to represent wear and the third body generation at the scale of the ball/retainer contact. An underlying role of the adhesion between components in controlling the tribological properties of the transfer film has been observed

Self-lubricating composite bearings: Effect of fibre length on its tribological properties by DEM modelling

International audienceSelf-lubricating polymer-based composites are used in space and in aircraft mechanisms as materials for solid lubricated systems. Such composites mostly consist of a polymeric matrix and fillers of two kinds: hard fillers (fibres made of glass, or of minerals) and solid lubricating particles (made of MoS 2). Their advantages are that they provide their own lubrication, and they can be used in both very high and very low temperatures (from −40 up to ~200 F). Precision ball bearings with these composites are manufactured since the 60's in these bearings the retainer material itself provides the lubrication. From the experimental analyses implemented (X-ray tomography, SEM observations, and experiences in a tribometer); it is possible to observe that the geometry of the fillers has a strong influence on the third body rheology. Nevertheless, the confined nature of the contact does not allow in-situ observation. To overcome this difficulty a combined numerical/experimental approach is carried out. To be able to reproduce the evolution of third-body particles within the contact, Discrete Element Methods (DEM) is used. Such an approach allows to represent wear: by the construction of an equivalent continuous medium resulting from the incorporation of interaction laws between the discrete particles. The motivation to this work is the understanding of the impact of filler geometry o tribological behaviour of these materials. More specifically, the goal is to study the influence of the fibre length in the tribological behaviour of self-lubricating composites by Discrete Element Methods (DEM)

Selection assisted by a BoLA-DR/DQ haplotype against susceptibility to bovine dermatophilosis

Bovine dermatophilosis is a severe skin infection of tropical ruminants inducing a severe loss in productivity and a 15% mortality rate. This disease is caused by the actinomycete bacterium Dermatophilus congolensis associated with the tick Amblyomma variegatum. Currently there are no prospects for a vaccine, and acaricide or antibiotic control is hampered by the development of chemoresistance. Animal breeders have observed that dermatophilosis susceptibility seems to be determined genetically, and we previously identified a BoLA-DRB3-DQB class II haplotype marker for high (R2 = 0.96) susceptibility to the disease. With this marker, we developed a successful eugenic selection procedure for zebu Brahman cattle in Martinique (FWI). Over a period of five years, a marked reduction in disease prevalence, from 0.76 to 0.02 was achieved, and this low level has been maintained over the last two years. The selection procedure, based on a genetic marker system targeting the highly polymorphic BoLA locus, eliminates only those individuals which are at the highest risk of contracting the disease. In the present work, we discuss the properties of this system, including the "heterozygote advantage" and the "frequency dependence" theories, and examine their involvement in the biological mechanisms at the host/pathogen interface. We speculate on the exact role of the MHC molecules in the control of the disease, how the natural selection pressure imposed by the pathogens selectively maintains MHC diversity, and how our results can be practically applied for integrated control of dermatophilosis in developing countries

Human pregnancy complicated by Chlamydia psittaci acquired from goat, a new zaonotic infection ?

Nous rapportons le cas d’une femme dont la grossesse s’est spontané ment interrompue à 32 semaines d’aménorrhée en raison d’une infection très sévère par Chlamydia psittaci. Cette infection est secondaire à un contact avec un troupeau de chèvres. Neuf cas d’infection materno-fœtale par Chlamydia psittaci d’origine animale sont décrits dans la littérature, il s’agit toujours d’une contamination par les brebis atteintes de chlamydiose abortive. La chèvre peut également être infectée par ce germe, mais la trans mission à la femme enceinte de la chlamydiose abortive caprine n’a pas été décrit jusqu’à présent.A case of chlamydial infection in pregnant woman is described. This infection was contracted from goat. The woman, who had contact with caprine abortion, spontaneously delivered a stillborn infant in the 32nd week of pregnancy. She developed dessiminated intravascular coagulation post partum with acute renal failure and pulmonary oedema. Nine cases of chlamydial infections in pregnant women have been reported in literature, in all cases, the infection was contracted from ewes suffering from enzootic abortion. Such an infection acquired from goat have not been previously described