Low level accelerometer test methods are investigated

Problems associated with testing accelerometers to an accuracy where the standard error is less than .0000001 g are centered around the elimination of uncertainties in the acceleration input to the accelerometer. By placing a test rig in free fall, the uncertainty in the earths gravity field can be eliminated

Vortex dynamics in superconducting channels with periodic constrictions

Vortices confined to superconducting easy flow channels with periodic constrictions exhibit reversible oscillations in the critical current at which vortices begin moving as the external magnetic field is varied. This commensurability scales with the channel shape and arrangement, although screening effects play an important role. For large magnetic fields, some of the vortices become pinned outside of the channels, leading to magnetic hysteresis in the critical current. Some channel configurations also exhibit a dynamical hysteresis in the flux-flow regime near the matching fields

Picovoltmeter for probing vortex dynamics in a single weak-pinning Corbino channel

We have developed a picovoltmeter using a Nb dc Superconducting QUantum Interference Device (SQUID) for measuring the flux-flow voltage from a small number of vortices moving through a submicron weak-pinning superconducting channel. We have applied this picovoltmeter to measure the vortex response in a single channel arranged in a circle on a Corbino disk geometry. The circular channel allows the vortices to follow closed orbits without encountering any sample edges, thus eliminating the influence of entry barriers.Comment: 4 pages, 3 figures, submitted to Review of Scientific Instrument

Flux Qubits and Readout Device with Two Independent Flux Lines

We report measurements on two superconducting flux qubits coupled to a readout Superconducting QUantum Interference Device (SQUID). Two on-chip flux bias lines allow independent flux control of any two of the three elements, as illustrated by a two-dimensional qubit flux map. The application of microwaves yields a frequency-flux dispersion curve for 1- and 2-photon driving of the single-qubit excited state, and coherent manipulation of the single-qubit state results in Rabi oscillations and Ramsey fringes. This architecture should be scalable to many qubits and SQUIDs on a single chip.Comment: 5 pages, 4 figures, higher quality figures available upon request. Submitted to PR

Spatio-temporal patterns in fin whale <i>Balaenoptera physalus</i> habitat use in the northern Gulf of St. Lawrence

Significant ecosystem changes in the Gulf of St. Lawrence (GSL), Canada, have had far-reaching effects at all trophic levels. The abundance of fin whales Balaenoptera physalus has declined significantly in the northern GSL over the past decade. This study aimed to test the hypothesis that the observed decline was correlated to changing environmental conditions. Cetacean sightings data from 292 surveys, resulting in 2986 fin whale encounters from 2007 to 2013, were used to fit 2 separate generalised additive models in terms of (1) bathymetric and oceanographic variables (the proxy model) and (2) modelled krill biomass (the prey model). The concept of ‘handling time’ was introduced to correct for time off search effort, applicable to other studies relying on opportunistically sampled data. While a positive correlation between krill biomass and fin whale numbers was found, the performance of the proxy model (24.2% deviance explained) was overall better than the prey model (11.8%). Annual predictive maps derived from the final proxy model highlighted 2 key areas with recurrently high relative fin whale abundance and a significant overlap with shipping lanes. While both models provided evidence for an annual decline in relative fin whale abundance, static bathymetric features were the most important predictors of habitat use, and no correlation between dynamic variables and the decline was found. High resolution prey data and a better understanding of the feeding ecology of fin whales are proposed to further investigate the predator-prey relationship and decline of fin whales in the GSL

STM Imaging of Flux Line Arrangements in the Peak Effect Regime

We present the results of a study of vortex arrangements in the peak-effect regime of 2H-NbSe_2 by scanning tunneling microscopy. By slowly increasing the temperature in a constant magnetic field, we observed a sharp transition from collective vortex motion to positional fluctuations of individual vortices at the temperature which coincides with the onset of the peak effect in ac-susceptibility. We conclude that the peak effect is a disorder driven transition, with the pinning energy winning from the elastic energy.Comment: 4 pages, 4 figures included Manuscript has been submitte

BMC Neuroscience

Résumé non disponible

Rain: Relaxations in the sky

We demonstrate how, from the point of view of energy flow through an open system, rain is analogous to many other relaxational processes in Nature such as earthquakes. By identifying rain events as the basic entities of the phenomenon, we show that the number density of rain events per year is inversely proportional to the released water column raised to the power 1.4. This is the rain-equivalent of the Gutenberg-Richter law for earthquakes. The event durations and the waiting times between events are also characterised by scaling regions, where no typical time scale exists. The Hurst exponent of the rain intensity signal $H = 0.76 > 0.5$. It is valid in the temporal range from minutes up to the full duration of the signal of half a year. All of our findings are consistent with the concept of self-organised criticality, which refers to the tendency of slowly driven non-equilibrium systems towards a state of scale free behaviour.Comment: 9 pages, 8 figures, submitted to PR

Entangling flux qubits with a bipolar dynamic inductance

We propose a scheme to implement variable coupling between two flux qubits using the screening current response of a dc Superconducting QUantum Interference Device (SQUID). The coupling strength is adjusted by the current bias applied to the SQUID and can be varied continuously from positive to negative values, allowing cancellation of the direct mutual inductance between the qubits. We show that this variable coupling scheme permits efficient realization of universal quantum logic. The same SQUID can be used to determine the flux states of the qubits.Comment: 4 pages, 4 figure

Physical activity during a treatment for substance use disorder: A qualitative study

Abstract Background Individuals with substance use disorder face a higher mortality rate, attributed in part to the presence of chronic physical conditions. Physical activity emerges as a promising solution, as it could impact on physical conditions as well as on the symptoms of substance use disorder itself. Although there is promising evidence, studies are still needed to fully understand the mechanisms, as well as their acceptability in real life. In order to address these issues, we need to include the perceptions of people who participate in these programs to determine the clinical importance and feasibility of physical activity. Objective To understand the physical activity perception of people undergoing treatment for substance use disorder. Methods Thirteen people (69% men; 33.4 ± 8.3 years old) were interviewed after experiencing a physical activity intervention during their treatment. Results Following the content analysis, three predominant themes emerged: physical activity was (1) a way to take care of themselves, through the perceived improvement of health; (2) used as a protective mechanism against relapse, through the occupation time, behavior replacement and the creation of a healthy network; (3) served as a facilitator of treatment retention because participant developed social support. Conclusion Physical activity during treatment could improve the therapeutic process for people with substance use disorders, as well as helping to develop healthy lifestyle habits and reinforce confidence in coping with future relapses