651 research outputs found
High-resolution spatial mapping of a superconducting NbN wire using single-electron detection
Superconducting NbN wires have recently received attention as detectors for
visible and infrared photons. We present experiments in which we use a NbN wire
for high-efficiency (40 %) detection of single electrons with keV energy. We
use the beam of a scanning electron microscope as a focussed, stable, and
calibrated electron source. Scanning the beam over the surface of the wire
provides a map of the detection efficiency. This map shows features as small as
150 nm, revealing wire inhomogeneities. The intrinsic resolution of this
mapping method, superior to optical methods, provides the basis of a
characterization tool relevant for photon detectors.Comment: 2009 IEEE Toronto International Conference, Science and Technology
for Humanity (TIC-STH
Excited exciton and biexciton localised states in a single quantum ring
We observe excited exciton and biexciton states of localised excitons in an
anisotropic quantum ring, where large polarisation asymmetry supports the
presence of a crescent-like localised structure. We also find that saturation
of the localised ground state exciton with increasing excitation can be
attributed to relatively fast dissociation of biexcitons (? 430 ps) compared to
slow relaxation from the excited state to the ground state (? 1000 ps). As no
significant excitonic Aharonov-Bohm oscillations occur up to 14 T, we conclude
that phase coherence around the rim is inhibited as a consequence of height
anisotropy in the quantum ring.Comment: 4 pages, 4 figure
Comparison of Simulator Wear Measured by Gravimetric vs Optical Surface Methods for Two Million Cycles
Understanding wear mechanisms are key for better implants
Critical to the success of the simulation
Small amount of metal wear can have catastrophic effects in the patient such as heavy metal poisoning or deterioration of the bone/implant interface leading to implant failure
Difficult to measure in heavy hard-on-hard implants (metal-on-metal or ceramic-on-ceramic)
May have only fractions of a milligram of wear on a 200 g component
At the limit of detection of even high-end balances when the component is 200 g and the change in weight is on the order of 0.000 1 grams
Here we compare the standard gravimetric wear estimate with
A non-contact 3D optical profiling method at each weighing stop
A coordinate measuring machine (CMM) at the beginning and end of the ru
Trapping of ultra-cold atoms with the magnetic field of vortices in a thin film superconducting micro-structure
We store and control ultra-cold atoms in a new type of trap using magnetic
fields of vortices in a high temperature superconducting micro-structure. This
is the first time ultra-cold atoms have been trapped in the field of magnetic
flux quanta. We generate the attractive trapping potential for the atoms by
combining the magnetic field of a superconductor in the remanent state with
external homogeneous magnetic fields. We show the control of crucial atom trap
characteristics such as an efficient intrinsic loading mechanism, spatial
positioning of the trapped atoms and the vortex density in the superconductor.
The measured trap characteristics are in good agreement with our numerical
simulations.Comment: 4pages, comments are welcom
Trapping of single atoms in cavity QED
By integrating the techniques of laser cooling and trapping with those of
cavity quantum electrodynamics (QED), single Cesium atoms have been trapped
within the mode of a small, high finesse optical cavity in a regime of strong
coupling. The observed lifetime for individual atoms trapped within the cavity
mode is ms, and is limited by fluctuations of light forces
arising from the far-detuned intracavity field. This initial realization of
trapped atoms in cavity QED should enable diverse protocols in quantum
information science.Comment: 4 pages, 4 figure
Single-photon tunneling
Strong evidence of a single-photon tunneling effect, a direct analog of
single-electron tunneling, has been obtained in the measurements of light
tunneling through individual subwavelength pinholes in a thick gold film
covered with a layer of polydiacetylene. The transmission of some pinholes
reached saturation because of the optical nonlinearity of polydiacetylene at a
very low light intensity of a few thousands photons per second. This result is
explained theoretically in terms of "photon blockade", similar to the Coulomb
blockade phenomenon observed in single-electron tunneling experiments. The
single-photon tunneling effect may find many applications in the emerging
fields of quantum communication and information processing.Comment: 4 pages, 4figure
Risk-reducing salpingo-oophorectomy, natural menopause, and breast cancer risk:an international prospective cohort of BRCA1 and BRCA2 mutation carriers
Background The effect of risk-reducing salpingo-oophorectomy (RRSO) on breast cancer risk for BRCA1 and BRCA2 mutation carriers is uncertain. Retrospective analyses have suggested a protective effect but may be substantially biased. Prospective studies have had limited power, particularly for BRCA2 mutation carriers. Further, previous studies have not considered the effect of RRSO in the context of natural menopause. Methods A multi-centre prospective cohort of 2272 BRCA1 and 1605 BRCA2 mutation carriers was followed for a mean of 5.4 and 4.9 years, respectively; 426 women developed incident breast cancer. RRSO was modelled as a time-dependent covariate in Cox regression, and its effect assessed in premenopausal and postmenopausal women. Results There was no association between RRSO and breast cancer for BRCA1 (HR = 1.23; 95% CI 0.94-1.61) or BRCA2 (HR = 0.88; 95% CI 0.62-1.24) mutation carriers. For BRCA2 mutation carriers, HRs were 0.68 (95% CI 0.40-1.15) and 1.07 (95% CI 0.69-1.64) for RRSO carried out before or after age 45 years, respectively. The HR for BRCA2 mutation carriers decreased with increasing time since RRSO (HR = 0.51; 95% CI 0.26-0.99 for 5 years or longer after RRSO). Estimates for premenopausal women were similar. Conclusion We found no evidence that RRSO reduces breast cancer risk for BRCA1 mutation carriers. A potentially beneficial effect for BRCA2 mutation carriers was observed, particularly after 5 years following RRSO. These results may inform counselling and management of carriers with respect to RRSO.</p
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