Aquifers survey in the context of source rocks exploitation: from baseline acquisition to long term monitoring.

International audienc

Control of friction forces with stationary wave piezoelectric actuator

"In the field of the research on piezoelectric motors, the control of friction forces by ultrasonic waves was studied mainly from an experimental point of view [1]. The principle of friction force reduction by imposed mechanical vibrations in unlubricated contacts was recently studied in order to reduce the friction losses in an internal combustion engine with Langevin type actuators [2]. This article deals with the advantages of flexural stationary wave piezoelectric actuators in the control of the friction forces thanks to their high pressures generated at high frequencies (>10 Khz). The use of specific contact geometry which is defined by the Hertz theory associated with partial slip contact conditions, allows optimizing the lubrication effect. In the case of piezoelectric torque limiter application, the design and the numerical simulation of dedicated piezoelectric actuator are compared. In agreement with the contact modeling, the characterization of the complete actuator on mechanical test bench validates the ""torque limiter"" function and the optimization of lubrication principle with dedicated contact geometry

Incremental Contributions of FbaA and Other Impetigo-Associated Surface Proteins to Fitness and Virulence of a Classical Group A Streptococcal Skin Strain

Group A streptococci (GAS) are highly prevalent human pathogens whose primary ecological niche is the superficial epithelial layers of the throat and/or skin. Many GAS strains having a strong tendency to cause pharyngitis are distinct from strains that tend to cause impetigo; thus, genetic differences between them may confer host tissue-specific virulence. In this study, the FbaA surface protein gene is found to be present in most skin specialist strains, but largely absent from a genetically-related subset of pharyngitis isolates. Using an DeltafbaA mutant constructed in the impetigo strain Alab49, loss of FbaA resulted in a slight but significant decrease in GAS fitness in a humanized mouse model for impetigo; the DeltafbaA mutant also exhibited decreased survival in whole human blood due to phagocytosis. Using assays with highly sensitive outcome measures, Alab49DeltafbaA was compared to other isogenic mutants lacking virulence genes known to be disproportionately associated with classical skin strains. FbaA and PAM (i.e., M53 protein) have additive effects in promoting GAS survival in whole blood. The pilus adhesin tip protein Cpa promotes Alab49 survival in whole blood, and appears to fully account for the antiphagocytic effect attributable to pili. That numerous skin strain-associated virulence factors make slight but significant contributions to virulence underscores the incremental contributions to fitness of individual surface protein genes and the multifactorial nature of GAS-host interactions

Quantum feedback by discrete quantum non-demolition measurements: towards on-demand generation of photon-number states

We propose a quantum feedback scheme for the preparation and protection of photon number states of light trapped in a high-Q microwave cavity. A quantum non-demolition measurement of the cavity field provides information on the photon number distribution. The feedback loop is closed by injecting into the cavity a coherent pulse adjusted to increase the probability of the target photon number. The efficiency and reliability of the closed-loop state stabilization is assessed by quantum Monte-Carlo simulations. We show that, in realistic experimental conditions, Fock states are efficiently produced and protected against decoherence.Comment: 8 pages, 5 figure

Accurate strain measurements in highly strained Ge microbridges

Ge under high strain is predicted to become a direct bandgap semiconductor. Very large deformations can be introduced using microbridge devices. However, at the microscale, strain values are commonly deduced from Raman spectroscopy using empirical linear models only established up to 1.2% for uniaxial stress. In this work, we calibrate the Raman-strain relation at higher strain using synchrotron based microdiffraction. The Ge microbridges show unprecedented high tensile strain up to 4.9 % corresponding to an unexpected 9.9 cm-1 Raman shift. We demonstrate experimentally and theoretically that the Raman strain relation is not linear and we provide a more accurate expression.Comment: 10 pages, 4 figure

Adiabatic passage and ensemble control of quantum systems

This paper considers population transfer between eigenstates of a finite quantum ladder controlled by a classical electric field. Using an appropriate change of variables, we show that this setting can be set in the framework of adiabatic passage, which is known to facilitate ensemble control of quantum systems. Building on this insight, we present a mathematical proof of robustness for a control protocol -- chirped pulse -- practiced by experimentalists to drive an ensemble of quantum systems from the ground state to the most excited state. We then propose new adiabatic control protocols using a single chirped and amplitude shaped pulse, to robustly perform any permutation of eigenstate populations, on an ensemble of systems with badly known coupling strengths. Such adiabatic control protocols are illustrated by simulations achieving all 24 permutations for a 4-level ladder

Operating an atom interferometer beyond its linear range

In this paper, we show that an atom interferometer inertial sensor, when associated to the auxiliary measurement of external vibrations, can be operated beyond its linear range and still keep a high acceleration sensitivity. We propose and compare two measurement procedures (fringe fitting and nonlinear lock) that can be used to extract the mean phase of the interferometer when the interferometer phase fluctuations exceed $2\pi$. Despite operating in the urban environment of inner Paris without any vibration isolation, the use of a low noise seismometer for the measurement of ground vibrations allows our atom gravimeter to reach at night a sensitivity as good as $5.5\times10^{-8}$g at 1 s. Robustness of the measurement to large vibration noise is also demonstrated by the ability of our gravimeter to operate during an earthquake with excellent sensitivity. Our high repetition rate allows for recovering the true low frequency seismic vibrations, ensuring proper averaging. Such techniques open new perspectives for applications in other fields, such as navigation and geophysics.Comment: 20 pages, 8 figure

Control of friction forces with stationary wave piezoelectric actuator

"In the field of the research on piezoelectric motors, the control of friction forces by ultrasonic waves was studied mainly from an experimental point of view [1]. The principle of friction force reduction by imposed mechanical vibrations in unlubricated contacts was recently studied in order to reduce the friction losses in an internal combustion engine with Langevin type actuators [2]. This article deals with the advantages of flexural stationary wave piezoelectric actuators in the control of the friction forces thanks to their high pressures generated at high frequencies (>10 Khz). The use of specific contact geometry which is defined by the Hertz theory associated with partial slip contact conditions, allows optimizing the lubrication effect. In the case of piezoelectric torque limiter application, the design and the numerical simulation of dedicated piezoelectric actuator are compared. In agreement with the contact modeling, the characterization of the complete actuator on mechanical test bench validates the ""torque limiter"" function and the optimization of lubrication principle with dedicated contact geometry

Nonlinear effect on quantum control for two-level systems

The traditional quantum control theory focuses on linear quantum system. Here we show the effect of nonlinearity on quantum control of a two-level system, we find that the nonlinearity can change the controllability of quantum system. Furthermore, we demonstrate that the Lyapunov control can be used to overcome this uncontrollability induced by the nonlinear effect.Comment: 4 pages, 5 figure