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Search Results: 1 - 10 of 1051 matches for " Romain Terazzi "
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Sequential resonant tunneling in quantum cascade lasers
Romain Terazzi,Tobias Gresch,Andreas Wittmann,Jér?me Faist
Physics , 2008, DOI: 10.1103/PhysRevB.78.155328
Abstract: A model of sequential resonant tunneling transport between two-dimensional subbands that takes into account explicitly elastic scattering is investigated. It is compared to transport measurements performed on quantum cascade lasers where resonant tunneling processes are known to be dominating. Excellent agreement is found between experiment and theory over a large range of current, temperature and device structures.
Uncontrolled Drilling: Exposing a Global Threat to Groundwater Sustainability  [PDF]
Romain Chesnaux
Journal of Water Resource and Protection (JWARP) , 2012, DOI: 10.4236/jwarp.2012.49084
Abstract: Untold numbers of boreholes are drilled into the earth’s crust every year. Most constitute a potential threat to groundwater quality by creating a preferred pathway for contaminant migration. Some solutions, including “well-pooling”, are proposed to better protect groundwater resources through the efficient management of boreholes.
Cardiomyocytes Derived from Human Induced Pluripotent Stem Cells: An In-Vitro Model to Predict Cardiac Effects of Drugs  [PDF]
Romain Sube, Eric A. Ertel
Journal of Biomedical Science and Engineering (JBiSE) , 2017, DOI: 10.4236/jbise.2017.1011040
Abstract: Introduction: Cardiomyocytes derived from human induced pluripotent stem cells (hiPSC-CM) form spontaneously beating syncytia in-vitro. We evaluated whether hiPSC-CM are a compelling model of human cardiac pharmacology useful for early drug development. Methods: We measured hiPSC-CM beating frequency using Ca-sensitive dyes and a high-throughput screening system. We quantified the effects of 640 drugs with various structures and pharmacologies. Results: When tested at 1 μM, most drugs without direct effects on heart rhythm or with effects at high concentrations do not change frequency, indicating specificity. In contrast, the preparation detects compounds with direct activity on heart rhythm, demonstrating sensitivity. In particular, β-adrenergic agonists increase frequency and the model differentiates β2 from β1 agonists, as well as partial from full agonists. Phosphodiesterase inhibitors have subtype-specific actions and PDE4 is particularly important in controlling frequency. The preparation is sensitive to cardiac ion channel blockers: L-type calcium channel blockers, Class-I and Class-III antiarrhythmics change frequency but drugs acting on KATP channels do not. The assay detects compounds blocking the cardiac rapid delayed-rectifier K channel and is an alternative to the classic “hERG test”. Conclusion: hiPSC-CM are a useful in-vitro cardiac model in drug development since they respond appropriately to drugs that modify heart rate in humans.
Computing with Neural Synchrony
Romain Brette
PLOS Computational Biology , 2012, DOI: 10.1371/journal.pcbi.1002561
Abstract: Neurons communicate primarily with spikes, but most theories of neural computation are based on firing rates. Yet, many experimental observations suggest that the temporal coordination of spikes plays a role in sensory processing. Among potential spike-based codes, synchrony appears as a good candidate because neural firing and plasticity are sensitive to fine input correlations. However, it is unclear what role synchrony may play in neural computation, and what functional advantage it may provide. With a theoretical approach, I show that the computational interest of neural synchrony appears when neurons have heterogeneous properties. In this context, the relationship between stimuli and neural synchrony is captured by the concept of synchrony receptive field, the set of stimuli which induce synchronous responses in a group of neurons. In a heterogeneous neural population, it appears that synchrony patterns represent structure or sensory invariants in stimuli, which can then be detected by postsynaptic neurons. The required neural circuitry can spontaneously emerge with spike-timing-dependent plasticity. Using examples in different sensory modalities, I show that this allows simple neural circuits to extract relevant information from realistic sensory stimuli, for example to identify a fluctuating odor in the presence of distractors. This theory of synchrony-based computation shows that relative spike timing may indeed have computational relevance, and suggests new types of neural network models for sensory processing with appealing computational properties.
Understanding the Evolution of Mammalian Brain Structures; the Need for a (New) Cerebrotype Approach
Romain Willemet
Brain Sciences , 2012, DOI: 10.3390/brainsci2020203
Abstract: The mammalian brain varies in size by a factor of 100,000 and is composed of anatomically and functionally distinct structures. Theoretically, the manner in which brain composition can evolve is limited, ranging from highly modular (“mosaic evolution”) to coordinated changes in brain structure size (“concerted evolution”) or anything between these two extremes. There is a debate about the relative importance of these distinct evolutionary trends. It is shown here that the presence of taxa-specific allometric relationships between brain structures makes a taxa-specific approach obligatory. In some taxa, the evolution of the size of brain structures follows a unique, coordinated pattern, which, in addition to other characteristics at different anatomical levels, defines what has been called here a “taxon cerebrotype”. In other taxa, no clear pattern is found, reflecting heterogeneity of the species’ lifestyles. These results suggest that the evolution of brain size and composition depends on the complex interplay between selection pressures and constraints that have changed constantly during mammalian evolution. Therefore the variability in brain composition between species should not be considered as deviations from the normal, concerted mammalian trend, but in taxa and species-specific versions of the mammalian brain. Because it forms homogenous groups of species within this complex “space” of constraints and selection pressures, the cerebrotype approach developed here could constitute an adequate level of analysis for evo-devo studies, and by extension, for a wide range of disciplines related to brain evolution.
Date de semis du mil et variabilité intra-saisonnière des précipitations au Niger
Romain Marteau
M@ppemonde , 2012,
Abstract: Les sociétés d’Afrique sahélienne sont connues pour la forte vulnérabilité de leur agriculture à la variabilité climatique (Mishra et al., 2008). Leur économie et leur sécurité alimentaire reposent principalement sur l’agriculture pluviale, mode de production le plus largement répandu. Les rendements agricoles sont extrêmement sensibles aux fluctuations inter-annuelles et intra-saisonnières des précipitations liées à la mousson d’été boréale. Cette région a enregistré au cours du XXe siècle la plus forte transition climatique, marquée par une péjoration pluviométrique exceptionnelle (Janicot, Fontaine, 1993; Lebel et al., 1997), avec de très fortes répercussions économiques et humaines, notamment sur les productions agricoles et les migrations.
Tivoli, une garnison assiégée à Kingston (Jama que, mai 2010)
Romain Cruse
M@ppemonde , 2010,
Le local sous l’ il des sciences sociales
Romain Huret
Transatlantica : Revue d'études Américaines , 2006,
Abstract: Here speaks a characteristic mood of these midland folk, living close to the earth, taking good times and bad, like the weather, as natural events to be endured as cheerfully as possible, with a strong conviction that nothing permanently bad can happen to America and that Providence teaches lessons through temporary adversity.Robert et Helen LyndMais oublier que l’enquête même est un rapport social qui tend inévitablement à structurer toutes les interactions, c’est se condamner à traiter comm...
Jennifer KLEIN. For All These Rights. Business, Labor, and the Shaping of America’s Public-Private Welfare State.
Romain Huret
Transatlantica : Revue d'études Américaines , 2006,
Abstract: At the 1939 World Fair in New York, Thomas Parkinson, the president of Equitable Life Assurance Society, proclaimed: “Security! The modern world is in constant search of security.” During the fair, Equitable policyholders could relax and find security in a garden and reflecting pool, which stood at the foot of the Equitable statue, aptly named Protection. Such a symbolic exhibit embodied the will of employers and insurers to adopt the language of security, which came to dominate political dis...
Does The Working Poor Exist ?
Romain Huret
Transatlantica : Revue d'études Américaines , 2006,
Abstract: Nelson Lichtenstein’s State of the Union is a major accomplishment: a piece of work that moves us closer to the understanding of the historical role of unions. This rich synthesis is both a story of American workers and an attempt to reinvigorate Labor History. The chapters dealing with the post war decades provide a fresh and stimulating analysis. Above all, Lichtenstein parts ways with the theory of the “labor management accord” after World War Two, and he reconsiders the efforts of liberal...
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