CCCP: A CCD Controller for Counting Photons

CCCP, a CCD Controller for Counting Photons, is presented. This new controller uses a totally new clocking architecture and allows to drive the CCD in a novel way. Its design is optimized for the driving of EMCCDs at up to 20MHz of pixel rate and fast vertical transfer. Using this controller, the dominant source of noise of EMCCDs at low flux level and high frame rate, the Clock Induced Charges, were reduced to 0.001 - 0.0018 electron/pixel/frame (depending of the electron multiplying gain), making efficient photon counting possible. CCCP will be deployed in 2009 on the ESO NTT through the 3D-NTT1 project and on the SOAR through the BTFI project.Comment: 10 pages, 10 figures, to appear in "Ground-based and Airborne Instrumentation for Astronomy II" SPIE conference, Marseille, 23-28 June 200

La demande d’énergie du secteur commercial québécois

Peu d’études ont comme sujet la demande d’énergie du secteur commercial au Canada. Parmi celles-ci, celles du ministère fédéral de l’Énergie des Mines et des Ressources et de l’Office National de l’Énergie ont utilisé l’approche à deux niveaux. Au premier niveau, la demande d’énergie est modélisée en fonction de son prix relatif, du PIB du secteur commercial et d’autres variables explicatives. Au second niveau, les parts thermiques des formes d’énergie sont reliées à leurs prix relatifs. Ces études se basent sur une mesure de la consommation d’énergie en équivalent thermique, introduisant ainsi un biais systématique au niveau de l’élasticité-prix et de l’élasticité-revenu. De plus, cette structure ignore les relations possibles entre l’énergie et les autres facteurs de production (capital et travail).Dans le cadre de la présente étude, nous empruntons une approche fréquemment employée lors de la modélisation du secteur industriel : le modèle KLEM à deux niveaux. Au premier niveau, la modélisation de la fonction de production du secteur commercial tient compte des relations possibles entre le capital, le travail et l’énergie. Au second niveau, la modélisation porte uniquement sur la demande des différentes formes d’énergie. De plus, nous abandonnons l’usage de la mesure de l’énergie en équivalent thermique à l’avantage de la mesure non biaisée de la dépense en énergie. Le modèle est appliqué au secteur commercial québécois. Les principaux résultats sont : au premier niveau, les élasticités des inputs à leur propre prix sont de signe anticipé, mais très faibles, seule l’énergie semble être influencée par le prix des facteurs de production. Au second niveau, les élasticités des formes d’énergie à leur propre prix sont de signe attendu mais également inférieures à l’unité. La substitution entre les formes d’énergie prédomine.Few studies are concerned with the energy demand of the canadian commercial sector. The modeling works in this area at EMR, Canada and at NEB rely on the two-levels approach. At the first level, the energy demand is expressed as function of energy relative price, commercial sector output, and other variables. At the second level, the market shares of energy forms are related to their relative prices. These studies are based on a thermal measure of energy consumption; such a way of measuring energy consumption introduces systematic bias in energy price and income elasticities. Furthermore, no account is taken of the possible relationships between energy and other inputs (capital and labour).In this paper, we use the approach which has been frequently applied to industrial sector energy demand modeling, i.e., the two-levels KLEM model. The first level deals with the aggregate production function of the commercial sector which emphasizes the relationships among capital, labour and energy. The second level, is concerned with the energy demand by sources only. Thermal measurement of energy consumption is abandoned in favor of real energy expense. The main results are: at the first level, the own price elasticities of inputs shows the signs anticipated on theoretical ground, but are very low, only energy appears to be influenced in some way by prices; at the second level, the signs of own price elasticities of energy forms are in agreement with theoretical expectations. However, they are rather less than unity thus showing limited substitution possibilities

Conception d'un système robotique sécuritaire pour la prise d'images échographiques

La sténose consiste en un blocage des vaisseaux sanguins qui peut survenir n'importe où dans le corps humain. Lorsqu'un vaisseau alimentant les membres inférieurs est partiellement bloqué, la pression sanguine diminue, causant des douleurs chroniques. Les systèmes modernes d'imagerie médicale en trois dimensions peuvent aider le diagnostic ou la planification d'une intervention chirurgicale de la sténose. Ces appareils coûteux soumettent souvent le patient à de fortes doses de radiations tout en lui injectant un agent contraste pour rehausser la visibilité du système vasculaire. L'échographie fait l'objet de plus en plus de recherches en imagerie 3D comme alternative potentielle permettant de poser un diagnostic de sténose. De plus, les ultrasons ne présentent aucune radiation ionisante et l'appareil est plus abordable. Afin d'effectuer la prise d'images échographiques par le déplacement d'une sonde en contact avec le patient, des robots sont développés. Un robot donne en tout temps la position de la sonde, en plus d'alléger la tâche du radiologue et de rendre possible l'automatisation de l'examen. Cette thèse propose le concept d'un nouveau robot effectuant l'examen échographique 3D des artères des membres inférieurs. Le design mécanique original de ce robot a été élaboré avec pour objectif un fonctionnement hautement sécuritaire pour le personnel de la santé et le patient. Puisqu'aucune norme de sécurité en robotique médicale n"a pu être recensée, une recherche approfondie de la littérature a permis l'élaboration d'une stratégie adaptée au défi posé par l'objectif de départ. Le robot à structure parallèle proposé permet de partager les efforts aux différents moteurs. Ses dimensions ont été mathématiquement déterminées afin qu'il soit en mesure d'effectuer l'examen échographique vasculaire demandant le plus grand déplacement : le balayage des vaisseaux sanguins des membres inférieurs. Conséquemment, tout autre examen demandant un déplacement plus petit pourra être réalisé. Des dispositifs mécaniques d'équilibrage statique ont par ailleurs permis de prédire le comportement du robot lorsqu'il est mis hors tension, en plus de minimiser les effets de la gravité. Enfin, les équations mécaniques détaillées rendront possible la fabrication d'un prototype du système robotique proposé

Extreme faint flux imaging with an EMCCD

An EMCCD camera, designed from the ground up for extreme faint flux imaging, is presented. CCCP, the CCD Controller for Counting Photons, has been integrated with a CCD97 EMCCD from e2v technologies into a scientific camera at the Laboratoire d'Astrophysique Experimentale (LAE), Universite de Montreal. This new camera achieves sub-electron read-out noise and very low Clock Induced Charge (CIC) levels, which are mandatory for extreme faint flux imaging. It has been characterized in laboratory and used on the Observatoire du Mont Megantic 1.6-m telescope. The performance of the camera is discussed and experimental data with the first scientific data are presented.Comment: 33 pages, 17 figures, accepted for publication in PAS

Optimum Static Balancing of a Parallel Robot for Medical 3D-Ultrasound Imaging

International audienceStatic balancing of mechanical systems is useful and required in many situations. The objective of such balancing is the compensation of gravitational forces in order to achieve a static equilibrium. A balanced system becomes safer and actuators are reduced in size. However, balancing a system requires numerous complex mechanical add-ons or unavoidable addition of mass. This is the reason why methods of partial static balancing have been developed and applied in practice. In this paper, a newly designed parallel robot for medical 3D-ultrasound imaging is required to be statically balanced without complicated design modifications. Simple mechanical add-on that is optimally designed can reduce substantially the effect of gravity. The efficiency of these suggested solutions is illustrated by numerical simulation of the robot

Characterization of dedifferentiating human mature adipocytes from the 6 visceral and subcutaneous fat compartments : fibroblast-activation protein 7 alpha and Dipeptidyl peptidase 4 as major components of matrix remodeling

Mature adipocytes can reverse their phenotype to become fibroblast-like cells. This is achieved by ceiling culture and the resulting cells, called dedifferentiated fat (DFAT) cells, are multipotent. Beyond the potential value of these cells for regenerative medicine, the dedifferentiation process itself raises many questions about cellular plasticity and the pathways implicated in cell behavior. This work has been performed with the objective of obtaining new information on adipocyte dedifferentiation, especially pertaining to new targets that may be involved in cellular fate changes. To do so, omental and subcutaneous mature adipocytes sampled from severely obese subjects have been dedifferentiated by ceiling culture. An experimental design with various time points along the dedifferentiation process has been utilized to better understand this process. Cell size, gene and protein expression as well as cytokine secretion were investigated. Il-6, IL-8, SerpinE1 and VEGF secretion were increased during dedifferentiation, whereas MIF-1 secretion was transiently increased. A marked decrease in expression of mature adipocyte transcripts (PPARγ2, C/EBPα, LPL and Adiponectin) was detected early in the process. In addition, some matrix remodeling transcripts (FAP, DPP4, MMP1 and TGFβ1) were rapidly and strongly up-regulated. FAP and DPP4 proteins were simultaneously induced in dedifferentiating mature adipocytes supporting a potential role for these enzymes in adipose tissue remodeling and cell plasticity

Role of the TGF-β pathway in dedifferentiation of human mature adipocytes

Dedifferentiation of adipocytes contributes to the generation of a proliferative cell population that could be useful in cellular therapy or tissue engineering. Adipocytes can dedifferentiate into precursor cells to acquire a fibroblast-like phenotype using ceiling culture, in which the buoyancy of fat cells is exploited to allow them to adhere to the inner surface of a container. Ceiling culture is usually performed in flasks, which limits the ability to test various culture conditions. Using a new 6-well plate ceiling culture approach, we examined the relevance of TGF-β signaling during dedifferentiation. Adipose tissue samples from patients undergoing bariatric surgery were digested with collagenase and cell suspensions were used for ceiling cultures. Using the 6-well plate approach, cells were treated with SB431542 (an inhibitor of TGF-β receptor ALK5) or human TGF-β1 during dedifferentiation. Gene expression was measured in these cultures and in whole adipose tissue, the stromal-vascular fraction (SVF), mature adipocytes and dedifferentiated fat (DFAT) cells. TGF-β1 and collagen type I alpha 1 (COL1A1) gene expression was significantly higher in DFAT cells compared to whole adipose tissue samples and SVF cells. TGF-β1, COL1A1 and COL6A3 gene expression was significantly higher at day 12 of dedifferentiation compared to day 0. In the 6-well plate model, treatment with recombinant TGFβ1 or SB431542 respectively stimulated and inhibited the TGF-β pathway as shown by increased TGF-β1, TGF-β2, COL1A1 and COL6A3 gene expression and decreased expression of TGF-β1, COL1A1, COL1A2 and COL6A3, respectively. Treatment of DFAT cells with recombinant TGF-β1 increased the phosphorylation level of SMAD 2 and SMAD 3. Thus, a new 6-well plate model for ceiling culture allowed us to demonstrate a role for TGF-β in modulating collagen gene expression during dedifferentiation of mature adipocytes

Temporal changes in gene expression profile during mature adipocyte dedifferentiation

Objective. To characterize changes in gene expression profile during human mature adipocyte dedifferentiation in ceiling culture. Methods. Subcutaneous (SC) and omental (OM) adipose tissue samples were obtained from 4 participants paired for age and BMI. Isolated adipocytes were dedifferentiated in ceiling culture. Gene expression analysis at days 0, 4, 7, and 12 of the cultures was performed using Affymetrix Human Gene 2.0 STvi arrays. Hierarchical clustering according to similarity of expression changes was used to identify overrepresented functions. Results. Four clusters gathered genes with similar expression between day 4 to day 7 but decreasing expression from day 7 to day 12. Most of these genes coded for proteins involved in adipocyte functions (LIPE, PLIN1, DGAT2, PNPLA2, ADIPOQ, CEBPA, LPL, FABP4, SCD, INSR, and LEP). Expression of several genes coding for proteins implicated in cellular proliferation and growth or cell cycle increased significantly from day 7 to day 12 (WNT5A, KITLG, and FGF5). Genes coding for extracellular matrix proteins were differentially expressed between days 0, 4, 7, and 12 (COL1A1, COL1A2, and COL6A3, MMP1, and TGFB1). Conclusion. Dedifferentiation is associated with downregulation of transcripts encoding proteins involved in mature adipocyte functions and upregulation of genes involved in matrix remodeling, cellular development, and cell cycle