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Search Results: 1 - 10 of 4033 matches for " Alain Letourneau "
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Delayed neutrons measurement at the MEGAPIE target
Stefano Panebianco,Pavel Bokov,Diane Dore,Xavier Ledoux,Alain Letourneau,Aurelien Prevost,Danas Ridikas
Physics , 2007,
Abstract: In the framework of the Neutronic and Nuclear Assessment Task Group of the MEGAPIE experiment we measured the delayed neutron (DN) flux at the top of the target. The measurement was proposed mainly for radioprotection purposes since the DN flux at the top of the target has been estimated to be of the same order of magnitude as the prompt neutron flux. Given the strong model-dependence of DN predictions, the measurement of DN contribution to the total neutron activity at the top of the target was thus desired. Moreover, this measurement is complementary to the DN experiments performed at PNPI (Gatchina) on solid lead and bismuth targets. The DN measurement at MEGAPIE was performed during the start-up phase of the target. In this paper we present a detailed description of the experimental setup and some preliminary results on decay spectra.
SNIF: A Futuristic Neutrino Probe for Undeclared Nuclear Fission Reactors
Thierry Lasserre,Maximilien Fechner,Guillaume Mention,Romain Reboulleau,Michel Cribier,Alain Letourneau,David Lhuillier
Physics , 2010,
Abstract: Today reactor neutrino experiments are at the cutting edge of fundamental research in particle physics. Understanding the neutrino is far from complete, but thanks to the impressive progress in this field over the last 15 years, a few research groups are seriously considering that neutrinos could be useful for society. The International Atomic Energy Agency (IAEA) works with its Member States to promote safe, secure and peaceful nuclear technologies. In a context of international tension and nuclear renaissance, neutrino detectors could help IAEA to enforce the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). In this article we discuss a futuristic neutrino application to detect and localize an undeclared nuclear reactor from across borders. The SNIF (Secret Neutrino Interactions Finder) concept proposes to use a few hundred thousand tons neutrino detectors to unveil clandestine fission reactors. Beyond previous studies we provide estimates of all known background sources as a function of the detector's longitude, latitude and depth, and we discuss how they impact the detectability.
A proposed search for a fourth neutrino with a PBq antineutrino source
Michel Cribier,Maximilien Fechner,Thierry Lasserre,Alain Letourneau,David Lhuillier,Guillaume Mention,Davide Franco,Vasily Kornoukhov,Stefan Schoenert
Physics , 2011, DOI: 10.1103/PhysRevLett.107.201801
Abstract: Several observed anomalies in neutrino oscillation data can be explained by a hypothetical fourth neutrino separated from the three standard neutrinos by a squared mass difference of a few eV^2. We show that this hypothesis can be tested with a PBq (ten kilocurie scale) 144Ce or 106Ru antineutrino beta-source deployed at the center of a large low background liquid scintillator detector. In particular, the compact size of such a source could yield an energy-dependent oscillating pattern in event spatial distribution that would unabiguously determine neutrino mass differences and mixing angles.
Comment on Phys. Rev. Lett. 108, 191802 (2012): "Observation of Reactor Electron Antineutrino Disappearance in the RENO Experiment"
Thierry Lasserre,Guillaume Mention,Michel Cribier,Antoine Collin,Vincent Durand,Vincent Fischer,Jonathan Gaffiot,David Lhuillier,Alain Letourneau,Matthieu Vivier
Statistics , 2012,
Abstract: The RENO experiment recently reported the disappearance of reactor electron antineutrinos consistent with neutrino oscillations, with a significance of 4.9 standard deviations. The published ratio of observed to expected number of antineutrinos in the far detector is R=0.920 +-0.009(stat.) +-0.014(syst.) and corresponds to sin^2 2theta13 = 0.113 +-0.013(stat.) +-0.019(syst), using a rate-only analysis. In this letter we reanalyze the data and we find a ratio R=0.903 +-0.01(stat.), leading to sin^2 2theta13 = 0.135. Moreover we show that the sin^2 2theta13 measurement still depend of the prompt high energy bound beyond 4 MeV, contrarily to the expectation based on neutrino oscillation.
Neutronic Characterization of the Megapie Target
Stefano Panebianco,Olivier Bringer,Pavel Bokov,Sebastien Chabod,Frederic Chartier,Emmeric Dupont,Diane Dore,Xavier Ledoux,Alain Letourneau,Ludovic Oriol,Aurelien Prevost,Danas Ridikas,Jean-Christian Toussaint
Physics , 2007,
Abstract: The MEGAPIE project is one of the key experiments towards the feasibility of Accelerator Driven Systems. On-line operation and post-irradiation analysis will provide the scientific community with unique data on the behavior of a liquid spallation target under realistic irradiation conditions. A good neutronics performance of such a target is of primary importance towards an intense neutron source, where an extended liquid metal loop requires some dedicated verifications related to the delayed neutron activity of the irradiated PbBi. In this paper we report on the experimental characterization of the MEGAPIE neutronics in terms of the prompt neutron (PN) flux inside the target and the delayed neutron (DN) flux on the top of it. For the PN measurements, a complex detector, made of 8 microscopic fission chambers, has been built and installed in the central part of the target to measure the absolute neutron flux and its spatial distribution. Moreover, integral information on the neutron energy distribution as a function of the position along the beam axis could be extracted, providing integral constraints on the neutron production models implemented in transport codes such as MCNPX. For the DN measurement, we used a standard 3He counter and we acquired data during the start-up phase of the target irradiation in order to take sufficient statistics at variable beam power. Experimental results obtained on the PN flux characteristics and their comparison with MCNPX simulations are presented, together with a preliminary analysis of the DN decay time spectrum.
Coping and Suicidal Ideations in Women with Symptoms of Postpartum Depression
S. Doucet and N. Letourneau
Clinical Medicine Insights: Reproductive Health , 2012,
Abstract: Objective: To explore the relationship between coping mechanisms and suicidal ideations among women who experience symptoms of postpartum depression. Design: This exploratory descriptive study used secondary data from a study of women who experienced symptoms of postpartum depression. Participants: Convenience and purposive sampling were used to obtain the community sample of 40 women who experienced symptoms of postpartum depression. Methods: Binary logistic regression was employed to explore emotion-focused coping, avoidance-focused coping, problem-focused coping, and religious coping as predictors of suicidal ideations. Results: Approximately 27% of the sample reported suicidal ideations within the past seven days. The results showed that lower levels of emotion-focused coping and higher levels of avoidance-focused and religious coping predicted suicidal ideations in participants. Problem-focused coping did not predict suicidal ideations. Conclusion: Overall, our findings provide support for the importance of coping mechanisms as predictors of suicidal ideations among women who experience symptoms of postpartum depression. The results illustrate the need for health professionals to conduct routine assessments on coping strategies and thoughts of suicide when caring for postpartum women, as well as the need to integrate coping approaches in the prevention and treatment of suicidal ideations.
Carnot Factor of a Vapour Power Cycle with Regenerative Extraction  [PDF]
Duparquet Alain
Journal of Modern Physics (JMP) , 2017, DOI: 10.4236/jmp.2017.811107
Abstract: The present paper describes the energy analysis of a regenerative vapour power system. The regenerative steam turbines based on the Rankine cycle and comprised of vapour extractions have been used industrially since the beginning of the 20th century, particularly regarding the processes of electrical production. After having performed worked in the first stages of the turbine, part of the vapour is directed toward a regenerative exchanger and heats feedwater coming from the condenser. This process is known as regeneration, and the heat exchanger where the heat is transferred from steam is called a regenerator (or a feedwater heater). The profit in the output brought by regenerative rakings is primarily enabled by the lack of exchange of the tapped vapour reheating water with the low-temperature reservoir. The economic optimum is often fixed at seven extractions. One knows the Carnot relation, which is the best possible theoretical yield of a dual-temperature cycle; in a Carnot cycle, one makes the assumption that both compressions and expansions are isentropic. This article studies an ideal theoretical machine comprised of vapour extractions in which each cycle partial of tapped vapour obeys these same compressions and isentropic expansions.
Essay on Playfulness and Play in Children’s Art Class: A Reflection Based on Winnicott  [PDF]
Alain Savoie
Creative Education (CE) , 2019, DOI: 10.4236/ce.2019.102024
Abstract: From a survey of literature, this article presents some reflections about the value of play and playfulness as, respectively, an activity and a creative attitude of mind to be fostered in art education in children. Indeed, at the heart of any artistic creative impulse sits a playful attitude of the artist towards realitya feature that has been highlighted by the psychoanalyst Winnicott. Following his line of thought, we propose that the art teacher must place the learner in a position of being able to play with her/him, in order to overlap their two areas of playing and establish a learning space. Playfulness and play tend to be confused with impulsive and disruptive behaviours and generally more tolerated at home then school. We claim that artistic activities in school should always be play-based and take place in a playful environment because art and creation emerge from and grow in and as play.
Plant Fitness Assessment for Wild Relatives of Insect Resistant Bt-Crops
D. K. Letourneau,J. A. Hagen
Journal of Botany , 2012, DOI: 10.1155/2012/389247
Abstract: When field tests of transgenic plants are precluded by practical containment concerns, manipulative experiments can detect potential consequences of crop-wild gene flow. Using topical sprays of bacterial Bacillus thuringiensislarvicide (Bt) and larval additions, we measured fitness effects of reduced herbivory on Brassica rapa (wild mustard) and Raphanus sativus (wild radish). These species represent different life histories among the potential recipients of Bt transgenes from Bt cole crops in the US and Asia, for which rare spontaneous crosses are expected under high exposure. Protected wild radish and wild mustard seedlings had approximately half the herbivore damage of exposed plants and 55% lower seedling mortality, resulting in 27% greater reproductive success, 14-day longer life-spans, and 118% more seeds, on average. Seed addition experiments in microcosms and in situ indicated that wild radish was more likely to spread than wild mustard in coastal grasslands. 1. Introduction Commercialized transgenic, insect resistant (IR) crops currently grown in the United States have virtually no wild relatives near production sites, thus ensuring that novel crop traits are unlikely to move into local wild gene pools. However, an assessment of the consequences of gene flow will be necessary in future deregulation decisions because most of the major and minor crops in the world either exist in the wild themselves or hybridize with wild relatives somewhere in their range [1–5]. Wild relatives of transformed plants that obtain IR traits through gene flow and introgression may be released from the pressure exerted by susceptible herbivores [6–14]. However, scant knowledge about the ecological factors that regulate the abundance, competitive ability, or geographic range of weeds limits our ability to predict whether novel plant defenses are likely to increase the weediness of wild crop relatives [14] or even whether herbivory has a negative or positive effect on plant growth and fitness [15–20]. Surprisingly, few tests have been conducted on the effects of herbivory on the spread of invasive plants [21, 22] or to quantify the effects of herbivory on plant vital rates [23]. Identifying and quantifying environmental risks associated with gene flow from transgenic crops is subject to methodological tradeoffs because of containment restrictions, especially for plant fitness effects, which require pollen production. Field tests with pollen-producing transgenic plants must be contained physically in cages or greenhouses or established at sites where wild relatives do
What Risk Assessments of Genetically Modified Organisms Can Learn from Institutional Analyses of Public Health Risks
S. Ravi Rajan,Deborah K. Letourneau
Journal of Biomedicine and Biotechnology , 2012, DOI: 10.1155/2012/203093
Abstract: The risks of genetically modified organisms (GMOs) are evaluated traditionally by combining hazard identification and exposure estimates to provide decision support for regulatory agencies. We question the utility of the classical risk paradigm and discuss its evolution in GMO risk assessment. First, we consider the problem of uncertainty, by comparing risk assessment for environmental toxins in the public health domain with genetically modified organisms in the environment; we use the specific comparison of an insecticide to a transgenic, insecticidal food crop. Next, we examine normal accident theory (NAT) as a heuristic to consider runaway effects of GMOs, such as negative community level consequences of gene flow from transgenic, insecticidal crops. These examples illustrate how risk assessments are made more complex and contentious by both their inherent uncertainty and the inevitability of failure beyond expectation in complex systems. We emphasize the value of conducting decision-support research, embracing uncertainty, increasing transparency, and building interdisciplinary institutions that can address the complex interactions between ecosystems and society. In particular, we argue against black boxing risk analysis, and for a program to educate policy makers about uncertainty and complexity, so that eventually, decision making is not the burden that falls upon scientists but is assumed by the public at large.
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