Tuning the effective coupling of an AFM lever to a thermal bath

Fabrication of Nano-Electro-Mechanical-Systems (NEMS) of high quality is nowadays extremely efficient. These NEMS will be used as sensors and actuators in integrated systems. Their use however raises questions about their interface (actuation, detection, read out) with external detection and control systems. Their operation implies many fundamental questions related to single particle effects such as Coulomb blockade, light matter interactions such as radiation pressure, thermal effects, Casimir forces and the coupling of nanosystems to external world (thermal fluctuations, back action effect). Here we specifically present how the damping of an oscillating cantilever can be tuned in two radically different ways: i) through an electro-mechanical coupling in the presence of a strong Johnson noise, ii) through an external feedback control of thermal fluctuations which is the cold damping closely related to Maxwell's demon. This shows how the interplay between MEMS or NEMS external control and their coupling to a thermal bath can lead to a wealth of effects that are nowadays extensively studied in different areas

Overcoming limitations of nanomechanical resonators with simultaneous resonances

Dynamic stabilization by simultaneous primary and superharmonic resonances for high order nonlinearity cancellation is demonstrated with an electrostatically-actuated, piezoresistively-transduced nanomechanical resonator. We prove experimentally how the combination of both the third-order nonlinearity cancellation and simultaneous resonances can be used to linearly drive a nanocantilever up to very large amplitudes compared to fundamental limits like pull-in occurrence, opening the way towards resonators with high frequency stability for high-performance sensing or time reference

How to square floats accurately and efficiently on the ST231 integer processor

We consider the problem of computing IEEE floating-point squares by means of integer arithmetic. We show how the specific properties of squaring can be exploited in order to design and implement algorithms that have much lower latency than those for general multiplication, while still guaranteeing correct rounding. Our algorithm descriptions are parameterized by the floating-point format, aim at high instruction-level parallelism (ILP) exposure, and cover all rounding modes. We show further that their C implementation for the binary32 format yields efficient codes for targets like the ST231 VLIW integer processor from STMicroelectronics, with a latency at least 1.75x smaller than that of general multiplication in the same context

Investigating the vertical extent and short-wave radiative effects of the ice phase in Arctic summertime low-level clouds

Low-level (cloud tops below 2 km) mixed-phase clouds are important in amplifying warming in the Arctic region through positive feedback in cloud fraction, water content and phase. In order to understand the cloud feedbacks in the Arctic region, good knowledge of the vertical distribution of the cloud water content, particle size and phase is required. Here we investigate the vertical extent of the cloud-phase and ice-phase optical properties in six case studies measured in the European Arctic during the ACLOUD campaign. Late spring- and summertime stratiform clouds were sampled in situ over pack ice, marginal sea ice zone and open-ocean surface, with cloud top temperatures varying between −15 and −1.5 ∘C. The results show that, although the liquid phase dominates the upper parts of the clouds, the ice phase was frequently observed in the lower parts down to cloud top temperatures as warm as −3.8 ∘C. In the studied vertical cloud profiles, the maximum of average liquid phase microphysical properties, droplet number concentration, effective radius and liquid water content, varied between 23 and 152 cm−3, 19 and 26 µm, 0.09 and 0.63 g m−3, respectively. The maximum of average ice-phase microphysical properties varied between 0.1 and 57 L−1 for the ice number concentration, 40 and 70 µm for the effective radius, and 0.005 and 0.08 g m−3 for the ice water content. The elevated ice crystal number concentrations and ice water paths observed for clouds, with cloud top temperatures between −3.8 and −8.7 ∘C can be likely attributed to secondary ice production through rime splintering. Low asymmetry parameters between 0.69 and 0.76 were measured for the mixed-phase ice crystals with a mean value of 0.72. The effect of the ice-phase optical properties on the radiative transfer calculations was investigated for the four cloud cases potentially affected by secondary ice production. Generally the choice of ice-phase optical properties only has a minor effect on the cloud transmissivity and albedo, except in a case where the ice phase dominated the upper cloud layer extinction. In this case, cloud albedo at solar wavelengths was increased by 10 % when the ice phase was given its measured optical properties instead of treating it as liquid phase. The presented results highlight the importance of accurate vertical information on cloud phase for radiative transfer and provide a suitable data set for testing microphysical parameterizations in models

Le jeu des solidarités rurales et urbaines : influences, interférences, contradictions. (Appel à contribution)

Dans le cadre de la collaboration entre la Maison des sciences de l'homme d'Aquitaine (Contrat quadriennal "Les solidarités" sous la responsabilité de Pierre Guillaume ) et l'Équipe "Sociétés rurales européennes contemporaines" (axe de l'UMR 5599 CNRS-Université Lyon 2, responsable Jean-Luc Mayaud), un colloque sera organisé à Lyon les 17 et 18 janvier 2002 sur le thème du "Jeu des solidarités rurales et urbaines : influences, interférences, contradictions". L'objectif est de repérer en quoi ..

Le jeu des solidarités rurales et urbaines : influences, interférences, contradictions. (Appel à contribution)

Dans le cadre de la collaboration entre la Maison des sciences de l'homme d'Aquitaine (Contrat quadriennal "Les solidarités" sous la responsabilité de Pierre Guillaume ) et l'Équipe "Sociétés rurales européennes contemporaines" (axe de l'UMR 5599 CNRS-Université Lyon 2, responsable Jean-Luc Mayaud), un colloque sera organisé à Lyon les 17 et 18 janvier 2002 sur le thème du "Jeu des solidarités rurales et urbaines : influences, interférences, contradictions". L'objectif est de repérer en quoi ..

Le jeu des solidarités rurales et urbaines : influences, interférences, contradictions

Dans le cadre de la collaboration entre la Maison des sciences de l'homme d'Aquitaine (Contrat quadriennal « Les solidarités » sous la responsabilité de Pierre Guillaume ) et l'Équipe « Sociétés rurales européennes contemporaines » (axe de l'UMR 5599 CNRS-Université Lyon 2, responsable Jean-Luc Mayaud), un colloque sera organisé à Lyon les 17 et 18 janvier 2002 sur le thème du « Jeu des solidarités rurales et urbaines : influences, interférences, contradictions ». L'objectif est de re..