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Search Results: 1 - 10 of 908 matches for " Cyril Lemarchand "
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Existe-t-il une signification sociale stable et univoque de la palatalisation/affrication en fran ais ? étude sur la perception de variantes non standard
Trimaille Cyril,Candea Maria,Lehka-Lemarchand Iryna
SHS Web of Conferences , 2012, DOI: 10.1051/shsconf/20120100122
Abstract: D’après les recherches récentes en sociophonétique, la palatalisation et/ou l’affrication des consonnes dentales /t, d/ devant les voyelles fermées /i, y/, fréquemment considérées par les phonéticiens comme des traits non-standards caractéristiques, en France hexagonale, d’une manière de parler des classes populaires, sont actuellement largement employées en fran ais par les locuteurs appartenant aux classes moyennes, voire supérieures; la diffusion de ce trait pourrait constituer un changement phonétique en cours. L’objectif de notre étude est de vérifier dans quelle mesure la palatalisation et/ou l’affrication influencent, consciemment ou non, l’évaluation et la catégorisation des productions des locuteurs par des auditeurs de deux grandes villes fran aises : Paris et Grenoble. Soucieux de rapprocher notre expérience perceptive de l’écoute en conditions naturelles, nous avons opté pour des stimulus assez longs et pour une consigne permettant de susciter les évaluations des auditeurs sans focaliser leur attention sur le phénomène étudié. Les stimulus consistent en plusieurs lectures par différents locuteurs d’une même dépêche radiophonique, comportant plusieurs contextes possibles de palatalisation/affrication. Les résultats obtenus suggèrent que la palatalisation/affrication ne serait suffisamment saillante ou stéréotypique pour qu'elle puisse, à elle seule, susciter des attributions négatives, conscientes ou non, et entrainer des évaluations négatives, au moins de la part des auditeurs agés de moins de 25 ans. En effet, l’évaluation d’une séquence de parole par les juges dépend fortement du contexte global de celle-ci, et la perception de la palatalisation/affrication semble être le résultat d’une corrélation complexe avec d’autres variables réalisées. La prise en compte de cette corrélation complexe nous amène à défendre une approche permettant de pondérer le poids des différents traits de prononciation dans la catégorisation d'un énoncé comme (in)acceptable dans un contexte donné.
Progress towards an accurate determination of the Boltzmann constant by Doppler spectroscopy
Cyril Lemarchand,Meriam Triki,Beno?t Darquié,Christian J. Bordé,Christian Chardonnet,Christophe Daussy
Physics , 2010, DOI: 10.1088/1367-2630/13/7/073028
Abstract: In this paper, we present significant progress performed on an experiment dedicated to the determination of the Boltzmann constant, k, by accurately measuring the Doppler absorption profile of a line in a gas of ammonia at thermal equilibrium. This optical method based on the first principles of statistical mechanics is an alternative to the acoustical method which has led to the unique determination of k published by the CODATA with a relative accuracy of 1.7 ppm. We report on the first measurement of the Boltzmann constant by laser spectroscopy with a statistical uncertainty below 10 ppm, more specifically 6.4 ppm. This progress results from improvements in the detection method and in the statistical treatment of the data. In addition, we have recorded the hyperfine structure of the probed saQ(6,3) rovibrational line of ammonia by saturation spectroscopy and thus determine very precisely the induced 4.36 (2) ppm broadening of the absorption linewidth. We also show that, in our well chosen experimental conditions, saturation effects have a negligible impact on the linewidth. Finally, we draw the route to future developments for an absolute determination of with an accuracy of a few ppm.
Evidence for speed-dependent effects in NH3 self-broadened spectra: towards a new determination of the Boltzmann constant
Meriam Triki,Cyril Lemarchand,Beno?t Darquié,Papa Lat Tabara Sow,Vincent Roncin,Christian Chardonnet,Christophe Daussy
Physics , 2012, DOI: 10.1103/PhysRevA.85.062510
Abstract: In this paper we present an accurate analysis of the shape of an isolated rovibrational ammonia line from the strong nu2 band around 10 $\mu$m, recorded by laser absorption spectroscopy. Experimental spectra obtained under controlled temperature and pressure, are confronted to various models that take into account Dicke narrowing or speed-dependent effects. Our results show clear evidence for speed-dependent broadening and shifting, which had never been demonstrated so far in NH3. Accurate lineshape parameters of the nu2 saQ(6,3) line are obtained. Our current project aiming at measuring the Boltzmann constant, kB, by laser spectroscopy will straight away benefit from such knowledge. We anticipate that a first optical determination of kB with a competitive uncertainty of a few ppm is now reachable.
Determination of the Boltzmann constant by laser spectroscopy as a basis for future measurements of the thermodynamic temperature
Cyril Lemarchand,Khelifa Djerroud,Beno?t Darquié,Olivier Lopez,Anne Amy-Klein,Christian Chardonnet,Christian J. Bordé,Stephan Briaudeau,Christophe Daussy
Physics , 2009, DOI: 10.1007/s10765-010-0755-3
Abstract: In this paper, we present the latest results on the measurement of the Boltzmann constant kB, by laser spectroscopy of ammonia at 10 ?m. The Doppler absorption profile of a ro-vibrational line of an NH3 gas sample at thermal and pressure equilibrium is measured as accurately as possible. The absorption cell is placed inside a large 1m3 thermostat filled with an ice-water mixture, which sets the temperature very close to 273.15 K. Analysing this profile, which is related to the Maxwell-Boltzmann molecular speed distribution, leads to a determination of the Boltzmann constant via a measurement of the Doppler width (proportional tosqrt(kBT)). A spectroscopic determination of the Boltzmann constant with an uncertainty as low as 37 ppm is obtained. Recent improvements with a new passive thermostat lead to a temperature accuracy, stability and homogeneity of the absorption cell better than 1 ppm over a day.
Measurement of the Boltzmann constant by the Doppler broadening technique at a 3,8x10-5 accuracy level
Khelifa Djerroud,Cyril Lemarchand,Alexandre Gauguet,Christophe Daussy,Stephan Briaudeau,Beno?t Darquié,Olivier Lopez,Anne Amy-Klein,Christian Chardonnet,Christian J. Bordé
Physics , 2009, DOI: 10.1016/j.crhy.2009.10.020
Abstract: In this paper, we describe an experiment performed at the Laboratoire de Physique des Lasers and dedicated to an optical measurement of the Boltzmann constant. With the proposed innovative technique, determining comes down to an ordinary frequency measurement. The method consists in measuring as accurately as possible the Doppler absorption profile of a rovibrational line of ammonia in thermal equilibrium. This profile is related to the Maxwell-Boltzmann molecular velocity distribution along the laser beam. A fit of the absorption line shape leads to a determination of the Doppler width proportional to sqrt(kT) and thus to a determination of the Boltzmann constant. The laser source is an ultra-stable CO2 laser with a wavelength . The absorption cell is placed in a thermostat keeping the temperature at 273.15 K within 1.4 mK. We were able to measure with a relative uncertainty as small as 3.8x10-5, which represents an improvement of an order of magnitude for an integration time comparable to our previous measurement published in 2007 [1]
A revised uncertainty budget for measuring the Boltzmann constant using the Doppler Broadening Technique on ammonia
Cyril Lemarchand,Sinda Mejri,Papa Lat Tabara Sow,Meriam Triki,Sean K. Tokunaga,Stephan Briaudeau,Christian Chardonnet,Beno?t Darquié,Christophe Daussy
Physics , 2013, DOI: 10.1088/0026-1394/50/6/623
Abstract: We report on our on-going effort to measure the Boltzmann constant, kB, using the Doppler Broadening Technique. The main systematic effects affecting the measurement are discussed. A revised error budget is presented in which the global uncertainty on systematic effects is reduced to 2.3 ppm. This corresponds to a reduction of more than one order of magnitude compared to our previous Boltzmann constant measurement. Means to reach a determination of kB at the part per million accuracy level are outlined.
Accurate determination of the Boltzmann constant by Doppler spectroscopy: Towards a new definition of the kelvin
Beno?t Darquié,Sinda Mejri,Papa Lat Tabara Sow,Cyril Lemarchand,Meriam Triki,Sean Tokunaga,Christian J. Bordé,Christian Chardonnet,Christophe Daussy
Physics , 2015, DOI: 10.1051/epjconf/20135702005
Abstract: Accurate molecular spectroscopy in the mid-infrared region allows precision measurements of fundamental constants. For instance, measuring the linewidth of an isolated Doppler-broadened absorption line of ammonia around 10 $\mu$m enables a determination of the Boltzmann constant k B. We report on our latest measurements. By fitting this lineshape to several models which include Dicke narrowing or speed-dependent collisional effects, we find that a determination of k B with an uncertainty of a few ppm is reachable. This is comparable to the best current uncertainty obtained using acoustic methods and would make a significant contribution to any new value of k B determined by the CODATA. Furthermore, having multiple independent measurements at these accuracies opens the possibility of defining the kelvin by fixing k B, an exciting prospect considering the upcoming redefinition of the International System of Units.
Counting on Beauty: The role of aesthetic, ethical, and physical universal principles for interstellar communication
Guillermo A. Lemarchand
Physics , 2008,
Abstract: SETI researchers believe that the basic principles of our science and the science of extraterrestrial beings should be fundamentally the same, and we should be able to communicate with them by referring to those things we share, such as the principles of mathematics, physics, and chemistry (a similar cognitive map of nature). This view assumes that there is only one way to conceptualize the laws of nature. Consequently, mathematics and the language of nature should be universal. In this essay, we discuss the epistemological bases of the last assumptions. We describe all the hypotheses behind the universality of the laws of nature and the restrictions that any technology should have to establish contact with other galactic technological civilization. We introduce some discussions about the limitations of homocentric views. We discuss about the possible use of aesthetic cognitive universals as well as ethical ones in the design of interstellar messages. We discuss the role of symmetry as a universal cognitive map. We give a specific example on how to use the Golden Section principles to design a hypothetical interstellar message based in physical and aesthetical cognitive universals. We build a space of configuration matrix, representing all the variables to be taken into account for designing an electromagnetic interstellar message (e.g. frequency, polarization, bandwidth, transmitting power, modulation, rate of information, galactic coordinates, etc.) against the limitations imposed by physical, technological, aesthetical and ethical constraints. We show how to use it, in order to make hypotheses about the characteristics and properties of hypothetical extraterrestrial artificial signals and their detection by existing SETI projects.
Science for Peace in the Benefit of Humankind. The Hippocratic Oath for Scientists concept
Guillermo A. Lemarchand
Physics , 2010,
Abstract: This article shows the importance that has had the scientific research, the technological development and the innovation processes in increasing the lethality of the available weapons during the last century. A set of initiatives promoted by the scientific community to stop the nuclear arms race that threatened the continuation of life on the planet is described. At this point, a thorough survey of the texts and proposals of Hippocratic Oaths for Scientists presented at different epochs is made. It is observed that the interest in linking ethical aspects with science and technology issues shows an exponential growth behavior since the Second World War. It is shown how the several proposals of oaths and ethical commitments for scientists, engineers and technologists are disseminated following a logistic growth behavior, in the same manner as a disembodied technology in a particular niche. The data analysis shows that there is a coincidence between the maximum rate of proposals and the historical moment at which the world had deployed the largest number of nuclear warheads (70,586) as well as the largest world military expenditures in history (USD 1,485,000,000,000). Subsequently, the origin of the Hippocratic Oath for Scientists used for more than two decades in graduation ceremonies at the Faculty of Exact and Natural Sciences of the University of Buenos Aires is analyzed and linked with the historical circumstances of its birth.
A brief social history of astrobiology in Ibero-america
Guillermo A. Lemarchand
Physics , 2010,
Abstract: The work is divided into three sections: the first one describes the historical evolution of the main arguments presented about the plurality of inhabited worlds, from the presocratics to the birth of modern science. The second section analyzes the race to define the search for life beyond Earth as a scientific activity under a specific name. Finally, the third part presents a brief description of the social history of science that allowed the early development of astrobiology in Iberoamerica.
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