Anisotropic Corbino magnetothermopower in a quantum Hall system

A Corbino-geometry contact configuration combined with a scanning laserspot as a heating source, is used for a thermovoltage mapping in a GaAs-AlGaAs quantum Hall device. For an isotropic system, the Corbino thermopower yields the diagonal component epsilon /sub xx/ of the thermoelectric tensor, which should be zero under the prevailing condition of phonon drag. The experiments reveal that epsilon /sub xx/ is large and anisotropic with respect to the crystallographic directions. The observations yield conclusive evidence that inhomogeneities are the origin for the existence of epsilon /sub xx

Efficiency of the flagellar propulsion of Escherichia coli in confined microfluidic geometries

Bacterial movement in confined spaces is routinely encountered either in a natural environment or in artificial structures. Consequently, the ability to understand and predict the behavior of motile bacterial cells in confined geometries is essential to many applications, spanning from the more classical, such as the management complex microbial networks involved in diseases, biomanufacturing, mining, and environment, to the more recent, such as single cell DNA sequencing and computation with biological agents. Fortunately, the development of this understanding can be helped by the decades-long advances in semiconductor microfabrication, which allow the design and the construction of complex confining structures used as test beds for the study of bacterial motility. To this end, here we use microfabricated channels with varying sizes to study the interaction of Escherichia coli with solid confining spaces. It is shown that an optimal channel size exists for which the hydrostatic potential allows the most efficient movement of the cells. The improved understanding of how bacteria move will result in the ability to design better microfluidic structures based on their interaction with bacterial movement

Psychological Factors Change during the Rehabilitation of an Achilles Tendon Rupture:A Multicenter Prospective Cohort Study

OBJECTIVE: The authors sought to gain insight into the changes in psychological factors during rehabilitation after Achilles tendon rupture (ATR) and to explore the association between psychological factors during rehabilitation and functional outcome 12 months after ATR. METHODS: Fifty patients clinically diagnosed with ATR were invited to visit the hospital 3, 6, and 12 months after injury for data collection. They completed questionnaires assessing psychological factors: psychological readiness to return to sport (Injury Psychological Readiness to Return to Sport Questionnaire); kinesiophobia (Tampa Scale for Kinesiophobia); expectations, motivation, and outcome measures related to symptoms and physical activity (Achilles Tendon Total Rupture Score); and sports participation and performance (Oslo Sports Trauma Research Centre Overuse Injury Questionnaire). To determine whether psychological factors changed over time, generalized estimating equation analyses were performed. Multivariate regression analyses were used to study the association between psychological factors at 3, 6, and 12 months and outcome measures at 12 months after ATR. RESULTS: Psychological readiness to return to sport improved, and kinesiophobia decreased significantly during rehabilitation. Psychological readiness at 6 and 12 months showed significant associations with sports participation and performance. Kinesiophobia at 6 months was significantly associated with symptoms and physical activity. Motivation remained high during rehabilitation and was highly associated with symptoms and physical activity, sports participation, and performance. CONCLUSION: Psychological factors change during rehabilitation after ATR. Patients with lower motivation levels during rehabilitation, low psychological readiness to return to sports, and/or high levels of kinesiophobia at 6 months after ATR need to be identified. IMPACT: According to these results, psychological factors can affect the rehabilitation of patients with ATR. Physical therapists can play an important role in recognizing patients with low motivation levels and low psychological readiness for return to sport and patients with high levels of kinesiophobia at 6 months post-ATR. Physical therapist interventions to enhance motivation and psychological readiness to return to sport and to reduce kinesiophobia need to be developed and studied in the post-ATR population. LAY SUMMARY: With Achilles tendon rupture, level of motivation, psychological readiness for return to sport, and fear of movement can affect rehabilitation outcome. A physical therapist can help recognize these factors

Enhanced low voltage nonlinearity in resonant tunneling metal–insulator–insulator–metal nanostructures

The electrical properties of bi-layer Ta2O5/Al2O3 and Nb2O5/Al2O3 metal–insulator–insulator–metal nanostructures as rectifiers have been investigated. The ultra-thin (1–6 nm) insulator layers were deposited by atomic-layer deposition or rf magnetron sputtering with Al as metal contacts. Variable angle spectroscopic ellipsometry was performed to extract the optical properties and band gap of narrow band gap insulator layers while the surface roughness of the metal contacts was measured by atomic force microscopy. Superior low voltage large signal and small signal nonlinearities such as asymmetry of 18 at 0.35 V, rate of change of non-linearity of 7.5 V�1, and responsivity of 9 A/W at 0.2 V were observed from the current–voltage characteristics. A sharp increase in current at �2 V on Ta2O5/Al2O3 device can be ascribed to resonant tunneling

Observation of the screening signature in the lateral photovoltage of electrons in the Quantum Hall regime

The lateral photovoltage generated in the plane of a two-dimensional electron system (2DES) by a focused light spot, exhibits a fine-structure in the quantum oscillations in a magnetic field near the Quantum Hall conductivity minima. A double peak structure occurs near the minima of the longitudinal conductivity oscillations. This is the characteristic signature of the interplay between screening and Landau quantization.Comment: 4 pages, 4 figures, to be published in Phys. Rev.

GAMBE: Thermal neutron detection system based on a sandwich configuration of silicon semiconductor detector coupled with neutron reactive material

© 2019 Elsevier Ltd Silicon semiconductor detectors are used efficiently for neutron detection when coated with a suitable material. They detect secondary reaction products resulting from the interaction of thermal neutrons with a neutron sensitive material such as 6 LiF. In the present work, the efficiency of the thermal neutron detector system, GAMBE, is discussed. This detector system based on two silicon sensors of 1 cm 2 active area and a layer of 6 LiF (1.5±0.6) mg/cm 2 thick in a sandwich configuration. This arrangement achieves total and coincidence detection efficiency of (4.1±0.5)% and (0.9±0.3)% respectively. The coincidence method defines a true neutron hit by the simultaneous signal recorded by the two sensors facing the conversion film. This coincidence methodology is applied to enhance the rejection factor of fake hits due to high gamma background conditions up to 10 8 as discussed in previous work. Geant simulation indicates that total and coincidence detection efficiency up to 55% and 18% are possible using an advanced design of stacked detectors