Spectromètres Ge(Li) 0 absorption totale

On a réalisé divers spectromètres Ge(Li) à absorption totale constitués par deux diodes fonctionnant en coïncidence-somme, ainsi qu'un détecteur puits de 52 cm3

Evidence for the coexistence of Dirac and massive carriers in a-(BEDT-TTF)2I3 under hydrostatic pressure

Transport measurements were performed on the organic layered compound \aI3 under hydrostatic pressure. The carrier types, densities and mobilities are determined from the magneto-conductance of \aI3 . While evidence of high-mobility massless Dirac carriers has already been given, we report here, their coexistence with low-mobility massive holes. This coexistence seems robust as it has been found up to the highest studied pressure. Our results are in agreement with recent DFT calculations of the band structure of this system under hydrostatic pressure. A comparison with graphene Dirac carriers has also been done.Comment: 5 pages 5 figure

DNA transport by a micromachined Brownian ratchet device

We have micromachined a silicon-chip device that transports DNA with a Brownian ratchet that rectifies the Brownian motion of microscopic particles. Transport properties for a DNA 50mer agree with theoretical predictions, and the DNA diffusion constant agrees with previous experiments. This type of micromachine could provide a generic pump or separation component for DNA or other charged species as part of a microscale lab-on-a-chip. A device with reduced feature size could produce a size-based separation of DNA molecules, with applications including the detection of single nucleotide polymorphisms.Comment: Latex: 8 pages, 4 figure

Social-ecological Resilience of a Nuosu Community-linked Watershed, Southwest Sichuan, China

Farmers of the Nuosu Yi ethnic group in the Upper Baiwu watershed report reductions in the availability of local forest resources. A team of interdisciplinary scientists worked in partnership with this community to assess the type and extent of social-ecological change in the watershed and to identify key drivers of those changes. Here, we combine a framework for institutional analysis with resilience concepts to assess system dynamics and interactions among resource users, resources, and institutions over the past century. The current state of this system reflects a legacy of past responses to institutional disturbances initiated at the larger, national system scale. Beginning with the Communist Revolution in 1957 and continuing through the next two decades, centralized forest regulations imposed a mismatch between the scale of management and the scale of the ecological processes being managed. A newly implemented forest property rights policy is shifting greater control over the management of forest resources to individuals in rural communities. Collective forest users will be allowed to manage commodity forests for profit through the transfer of long-term leases to private contractors. Villagers are seeking guidance on how to develop sustainable and resilient forest management practices under the new policy, a responsibility returned to them after half a century and with less abundant and fewer natural resources, a larger and aggregated population, and greater influence from external forces. We assess the watershed’s current state in light of the past and identify future opportunities to strengthen local institutions for governance of forest resources

Maintaining Disorder: Some Technical and Aesthetic Issues Involved in the Performance of Ligeti’s E´ tudes for Piano

This article examines some of the particular questions and associated strategies concerning matters of rhythm, perceived metre, notation, accentuation, line, physical approach to the keyboard, pedalling, and more in the performance of Ligeti’s Études for piano. I relate these issues to those encountered in earlier repertoire, including works of Schumann, Liszt, Stravinsky, Prokofiev, Bartók and Blacher, and argue that particular approaches and attitudes to both technical and musical matters in the context of these Études can fundamentally affect the concept of the music. A particular focus is upon issues of continuity and discontinuity, and the ‘situation’ of these works within particular pianistic and other traditions by virtue of the approach taken to performance

Single-cell, whole-embryo phenotyping of mammalian developmental disorders

Mouse models are a critical tool for studying human diseases, particularly developmental disorders. However, conventional approaches for phenotyping may fail to detect subtle defects throughout the developing mouse. Here we set out to establish single-cell RNA sequencing of the whole embryo as a scalable platform for the systematic phenotyping of mouse genetic models. We applied combinatorial indexing-based single-cell RNA sequencing to profile 101 embryos of 22 mutant and 4 wild-type genotypes at embryonic day 13.5, altogether profiling more than 1.6 million nuclei. The 22 mutants represent a range of anticipated phenotypic severities, from established multisystem disorders to deletions of individual regulatory regions. We developed and applied several analytical frameworks for detecting differences in composition and/or gene expression across 52 cell types or trajectories. Some mutants exhibit changes in dozens of trajectories whereas others exhibit changes in only a few cell types. We also identify differences between widely used wild-type strains, compare phenotyping of gain- versus loss-of-function mutants and characterize deletions of topological associating domain boundaries. Notably, some changes are shared among mutants, suggesting that developmental pleiotropy might be 'decomposable' through further scaling of this approach. Overall, our findings show how single-cell profiling of whole embryos can enable the systematic molecular and cellular phenotypic characterization of mouse mutants with unprecedented breadth and resolution

Effets des champs electriques alternatifs et continus sur la luminescence de certains sulfures de zinc excités par un rayonnement α.

Pas de Résumé disponibl

Étude théorique et expérimentale de la luminescence de l'argon induite par des particules α

An analysis of the nature and of the evolution of the atomic states excited in argon by fast ionizing particles, leads to the conclusion that the radioluminescence of the gas at pressures of the order of one atmosphere, is due to a radiative emission from excited dimers A**2. These dimers are formed in three-body collisions involving an atom A** excited in a state belonging to the configuration (3p)5 5s or (3 p)5 3d. This is in agreement with the experimental results on the fluorescence spectra and decay times, obtained by methods which are briefly described. It is found that the mean lifetimes of the excited atom A** and dimer A**2 are respectively equal to 10-7 s and to 6 x 10-9 s. The rate constant of the ternary collision producing the excited dimers is found to be 22 × 10-32 cm 6 s-1. The numerical values thus obtained are discussed.L'analyse de la nature et de l'évolution des états atomiques excités dans l'argon par des particules α, nous a conduits à attribuer la radioluminescence de ce gaz, pour des pressions voisines d'une atmosphère, à la désactivation radiative de molécules diatomiques A**2 formées lors de chocs à trois corps à partir d'atomes A ** se trouvant dans des états de configurations électroniques (3 p)5 5s et (3p)5 3d. Les résultats expérimentaux obtenus lors de la détermination des spectres d'émission et des courbes de décroissance de l'intensité lumineuse en fonction du temps ont confirmé cette interprétation et nous ont permis d'évaluer la durée de vie moyenne des atomes A** (∼ 10-7 s) et des molécules A**2 (6 × 10-9 s), ainsi que la constante de vitesse des processus à trois corps conduisant à la formation des dimères A**2 (k2 = 22 × 10-32 cm6 s -1). La signification des valeurs numériques ainsi obtenues est discutée