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Search Results: 1 - 10 of 3999 matches for " Alain Chiolero "
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Macroscopic Quantum Coherence in Ferrimagnets
Alain Chiolero,Daniel Loss
Physics , 1997, DOI: 10.1103/PhysRevB.56.738
Abstract: We study macroscopic quantum coherence (MQC) in small ferrimagnets. Through semi-classical calculations we show that even a small uncompensated moment has a drastic effect on MQC. In particular, there is a rapid crossover to a regime where the MQC tunnel splitting is equal to that obtained for a ferromagnet, even though the system is still an antiferromagnet for all other aspects. We calculate this tunnel splitting via instanton methods and compare it with numerical evaluations. As an application we re-examine the experimental evidence for MQC in ferritin and show that even though the uncompensated moment of ferritin is small it greatly modifies the MQC behavior. We also discuss the implications of our results for MQC in molecular magnets.
Macroscopic Quantum Coherence in Molecular Magnets
Alain Chiolero,Daniel Loss
Physics , 1997, DOI: 10.1103/PhysRevLett.80.169
Abstract: We study macroscopic quantum coherence in antiferromagnetic molecular magnets in the presence of magnetic fields. Such fields generate artificial tunnel barriers with externally tunable strength. We give detailed semi-classical predictions for the tunnel splitting in various regimes for low and high magnetic fields. We show that the tunneling dynamics of the Neel vector can be directly measured via the static magnetization and the specific heat. We also report on a new quantum phase arising from fluctuations. The analytic results are complemented by numerical simulations.
Assessing the Relationship between the Baseline Value of a Continuous Variable and Subsequent Change Over Time
Arnaud Chiolero,Benjamin Rich
Frontiers in Public Health , 2013, DOI: 10.3389/fpubh.2013.00029
Abstract: Analyzing the relationship between the baseline value and subsequent change of a continuous variable is a frequent matter of inquiry in cohort studies. These analyses are surprisingly complex, particularly if only two waves of data are available. It is unclear for non-biostatisticians where the complexity of this analysis lies and which statistical method is adequate. With the help of simulated longitudinal data of body mass index in children, we review statistical methods for the analysis of the association between the baseline value and subsequent change, assuming linear growth with time. Key issues in such analyses are mathematical coupling, measurement error, variability of change between individuals, and regression to the mean. Ideally, it is better to rely on multiple repeated measurements at different times and a linear random effects model is a standard approach if more than two waves of data are available. If only two waves of data are available, our simulations show that Blomqvist’s method – which consists in adjusting for measurement error variance the estimated regression coefficient of observed change on baseline value – provides accurate estimates. The adequacy of the methods to assess the relationship between the baseline value and subsequent change depends on the number of data waves, the availability of information on measurement error, and the variability of change between individuals.
Changes of overweight and obesity in the adult Swiss population according to educational level, from 1992 to 2007
Pedro Marques-Vidal, Pascal Bovet, Fred Paccaud, Arnaud Chiolero
BMC Public Health , 2010, DOI: 10.1186/1471-2458-10-87
Abstract: Four cross-sectional National health interview surveys conducted in 1992/93 (n = 14,521), 1997 (n = 12,474), 2002 (n = 18,908) and 2007 (n = 17,879) using representative samples of the Swiss population (age range 18-102 years). BMI was derived from self-reported data. Overweight was defined as BMI ≥ 25 and <30 kg/m2, and obesity as BMI ≥ 30 kg/m2.Mean (± standard deviation) BMI increased from 24.7 ± 3.6 in 1992/3 to 25.4 ± 3.6 kg/m2 in 2007 in men and 22.8 ± 3.8 to 23.7 ± 4.3 kg/m2 in women. Between 1992/3 and 2007, the prevalence of overweight + obesity increased from 40.4% to 49.5% in men and from 22.3% to 31.3% in women, while the prevalence of obesity increased from 6.3% to 9.4% in men and from 4.9% to 8.5% in women. The rate of increase in the prevalence of obesity was greater between 1992/3 and 2002 (men: +0.26%/year; women: +0.31%/year) than between 2002 and 2007 (men: +0.10%/year; women: +0.10%/year). A sizable fraction (~25%) of the increasing mean BMI was due to increasing age of the participants over time. The increase was larger in low than high education strata of the population. BMI was strongly associated with low educational level among women and this gradient remained fairly constant over time. A weaker similar gradient by educational level was apparent in men, but it tended to increase over time.In Switzerland, overweight and obesity increased between 1992 and 2007 and was associated with low education status in both men and women. A trend towards a stabilization of mean BMI levels was noted in most age categories since 2002. The increase in the prevalence of obesity was larger in low education strata of the population. These findings suggest that obesity preventive measures should be targeted according to educational level in Switzerland.The association between educational level and obesity varies between populations [1]. Several studies in the USA [2] and in European countries have shown a widening gap in obesity levels between socio-economic gro
Clustering of smoking, alcohol drinking and cannabis use in adolescents in a rapidly developing country
David Faeh, Bharathi Viswanathan, Arnaud Chiolero, Wick Warren, Pascal Bovet
BMC Public Health , 2006, DOI: 10.1186/1471-2458-6-169
Abstract: Cross-sectional survey in a representative sample of secondary school students using an anonymous self-administered questionnaire (Global Youth Tobacco Survey). The questionnaire was completed by 1,321 (92%) of 1,442 eligible students aged 11 to 17 years. Main variables of interest included smoking cigarettes on ≥1 day in the past 30 days; drinking any alcohol beverage on ≥1 day in the past 30 days and using cannabis at least once in the past 12 months.In boys and girls, respectively, prevalence (95% CI) was 30% (26–34)/21% (18–25) for smoking, 49% (45–54)/48% (43–52) for drinking, and 17% (15–20)/8% (6–10) for cannabis use. The prevalence of all these behaviors increased with age. Smokers were two times more likely than non-smokers to drink and nine times more likely to use cannabis. Drinkers were three times more likely than non-drinkers to smoke or to use cannabis. Comparison of observed versus expected frequencies of combination categories demonstrated clustering of these risk behaviors in students (P < 0.001).Smoking, drinking and cannabis use were common and clustered among adolescents of a rapidly developing country. These findings stress the need for early and integrated prevention programs.In addition to the increased risk of chronic diseases at an older age, smoking, drinking and use of illegal substances in adolescents are associated with more immediate health hazards such as depression, interpersonal violence, motor vehicle crashes and drowning, risky sexual behaviors, and suicidal behavior [1-3]. Furthermore, behaviors initiated during adolescence tend to track into adulthood [4]. Early experience with smoking and drinking increases the risk of subsequent tobacco [5] and alcohol [6] dependences. In addition, cross-sectional [7-9] and longitudinal [10-12] studies in western countries have shown that these behaviors tended to cluster in adolescence and perhaps even at an earlier age [13]. Also of importance, these behaviors increase the likelihood to adop
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.
Design of a Performance Measurement Framework for Cloud Computing  [PDF]
Luis Bautista, Alain Abran, Alain April
Journal of Software Engineering and Applications (JSEA) , 2012, DOI: 10.4236/jsea.2012.52011
Abstract: Cloud Computing is an emerging technology for processing and storing very large amounts of data. Sometimes anomalies and defects affect part of the cloud infrastructure, resulting in a performance degradation of the cloud. This paper proposes a performance measurement framework for Cloud Computing systems, which integrates software quality concepts from ISO 25010.
Prevalence of thinness in children and adolescents in the Seychelles: comparison of two international growth references
Pascal Bovet, Nathalie Kizirian, George Madeleine, Monika Bl?ssner, Arnaud Chiolero
Nutrition Journal , 2011, DOI: 10.1186/1475-2891-10-65
Abstract: Weight and height were measured every year in all children of 4 grades (age range: 5 to 16 years) of all schools in the Seychelles as part of a routine school-based surveillance program. In this study we used data collected in 16,672 boys and 16,668 girls examined from 1998 to 2004. Thinness was estimated according to two growth references: i) an international survey (IS), defining three grades of thinness corresponding to a BMI of 18.5, 17.0 and 16.0 kg/m2 at age 18 and ii) the WHO reference, defined here as three categories of thinness (-1, -2 and -3 SD of BMI for age) with the second and third named "thinness" and "severe thinness", respectively.The prevalence of thinness was 21.4%, 6.4% and 2.0% based on the three IS cut-offs and 27.7%, 6.7% and 1.2% based on the WHO cut-offs. The prevalence of thinness categories tended to decrease according to age for both sexes for the IS reference and among girls for the WHO reference.The prevalence of the first category of thinness was larger with the WHO cut-offs than with the IS cut-offs while the prevalence of thinness of "grade 2" and thinness of "grade 3" (IS cut-offs) was similar to the prevalence of "thinness" and "severe thinness" (WHO cut-offs), respectively.Although the prevalence of overweight is increasing worldwide, underweight remains a major public health problem and is a leading cause of the burden of disease in low income countries [1]. Underweight is linked to growth faltering and is associated with increased morbidity and mortality [2-6]. Monitoring growth and nutritional status during infancy and childhood is therefore of primary importance. Thinness can be a marker of malnutrition although thin children are not necessarily undernourished. Thinness in school children and adolescents is largely under studied, contrasting with the vast amount of literature on infant malnutrition and a current focus on overweight in children and adolescents.Recently, two growth references have been developed for the classif
Excess Spin and the Dynamics of Antiferromagnetic Ferritin
J. G. E. Harris,J. E. Grimaldi,D. D. Awschalom,A. Chiolero,D. Loss
Physics , 1999, DOI: 10.1103/PhysRevB.60.3453
Abstract: Temperature-dependent magnetization measurements on a series of synthetic ferritin proteins containing from 100 to 3000 Fe(III) ions are used to determine the uncompensated moment of these antiferromagnetic particles. The results are compared with recent theories of macroscopic quantum coherence which explicitly include the effect of this excess moment. The scaling of the excess moment with protein size is consistent with a simple model of finite size effects and sublattice noncompensation.
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