SEASAT: A satellite scatterometer illumination times of selected in situ sites

A list of times that the SEASAT A Satellite Scatterometer (SASS) illuminated from directly above or directly abeam, selected surface sites where in situ winds were measured is provided. The list is ordered by the Greenwich Mean Time (GMT) of the midpoint of the illumination period (hit time) for a given surface site. The site identification, the orbit number and the direction from the subtrack in which the truth lies are provided. The accuracy of these times depends in part upon the ascending node times, which are estimated to be within +.1 sec, and on the illumination time relative to the ascending node, which is estimated to be within +6 seconds. The uncertainties in the times provided were judged to be sufficiently small to allow efficient and accurate extraction of SASS and in situ data at the selected surface sites. The list contains approximately six thousand hit times from 61 geographically dispersed sites

A Time-Orbiting Potential Trap for Bose-Einstein Condensate Interferometry

We describe a novel atom trap for Bose-Einstein condensates of 87Rb to be used in atom interferometry experiments. The trap is based on a time-orbiting potential waveguide. It supports the atoms against gravity while providing weak confinement to minimize interaction effects. We observe harmonic oscillation frequencies omega_x, omega_y, omega_z as low as 2 pi times (6.0,1.2,3.3) Hz. Up to 2 times 10^4 condensate atoms have been loaded into the trap, at estimated temperatures as low as 850 pK. We anticipate that interferometer measurement times of 1 s or more should be achievable in this device.Comment: 9 pages, 3 figure

Observation of a One-Dimensional Spin-Orbit Gap in a Quantum Wire

Understanding the flow of spins in magnetic layered structures has enabled an increase in data storage density in hard drives over the past decade of more than two orders of magnitude1. Following this remarkable success, the field of 'spintronics' or spin-based electronics is moving beyond effects based on local spin polarisation and is turning its attention to spin-orbit interaction (SOI) effects, which hold promise for the production, detection and manipulation of spin currents, allowing coherent transmission of information within a device. While SOI-induced spin transport effects have been observed in two- and three-dimensional samples, these have been subtle and elusive, often detected only indirectly in electrical transport or else with more sophisticated techniques. Here we present the first observation of a predicted 'spin-orbit gap' in a one-dimensional sample, where counter-propagating spins, constituting a spin current, are accompanied by a clear signal in the easily-measured linear conductance of the system.Comment: 10 pages, 5 figures, supplementary informatio

Daylight quantum key distribution over 1.6 km

Quantum key distribution (QKD) has been demonstrated over a point-to-point $\sim1.6$-km atmospheric optical path in full daylight. This record transmission distance brings QKD a step closer to surface-to-satellite and other long-distance applications.Comment: 4 pages, 2 figures, 1 table. Submitted to PRL on 14 January 2000 for publication consideratio

Deep Chandra Observation of the Pulsar Wind Nebula Powered by the Pulsar J1846-0258 in the Supernova Remnant Kes 75

We present the results of detailed spatial and spectral analysis of the pulsar wind nebula (PWN) in supernova remnant Kes 75 (G29.7-0.3) using a deep exposure with Chandra X-ray observatory. The PWN shows a complex morphology with clear axisymmetric structure. We identified a one-sided jet and two bright clumps aligned with the overall nebular elongation, and an arc-like feature perpendicular to the jet direction. Further spatial modeling with a torus and jet model indicates a position angle 207\arcdeg\pm8 \arcdeg for the PWN symmetry axis. We interpret the arc as an equatorial torus or wisp and the clumps could be shock interaction between the jets and the surrounding medium. The lack of any observable counter jet implies a flow velocity larger than 0.4c. Comparing to an archival observation 6 years earlier, some small-scale features in the PWN demonstrate strong variability: the flux of the inner jet doubles and the peak of the northern clump broadens and shifts 2" outward. In addition, the pulsar flux increases by 6 times, showing substantial spectral softening from $\Gamma$=1.1 to 1.9 and an emerging thermal component which was not observed in the first epoch. The changes in the pulsar spectrum are likely related to the magnetar-like bursts of the pulsar that occurred 7 days before the Chandra observation, as recently reported from RXTE observations.Comment: Accepted by ApJ, 8 figures, some of them have been scaled down in resolutio

Functional Electrical Stimulation mediated by Iterative Learning Control and 3D robotics reduces motor impairment in chronic stroke

Background: Novel stroke rehabilitation techniques that employ electrical stimulation (ES) and robotic technologies are effective in reducing upper limb impairments. ES is most effective when it is applied to support the patients’ voluntary effort; however, current systems fail to fully exploit this connection. This study builds on previous work using advanced ES controllers, and aims to investigate the feasibility of Stimulation Assistance through Iterative Learning (SAIL), a novel upper limb stroke rehabilitation system which utilises robotic support, ES, and voluntary effort. Methods: Five hemiparetic, chronic stroke participants with impaired upper limb function attended 18, 1 hour intervention sessions. Participants completed virtual reality tracking tasks whereby they moved their impaired arm to follow a slowly moving sphere along a specified trajectory. To do this, the participants’ arm was supported by a robot. ES, mediated by advanced iterative learning control (ILC) algorithms, was applied to the triceps and anterior deltoid muscles. Each movement was repeated 6 times and ILC adjusted the amount of stimulation applied on each trial to improve accuracy and maximise voluntary effort. Participants completed clinical assessments (Fugl-Meyer, Action Research Arm Test) at baseline and post-intervention, as well as unassisted tracking tasks at the beginning and end of each intervention session. Data were analysed using t-tests and linear regression. Results: From baseline to post-intervention, Fugl-Meyer scores improved, assisted and unassisted tracking performance improved, and the amount of ES required to assist tracking reduced. Conclusions: The concept of minimising support from ES using ILC algorithms was demonstrated. The positive results are promising with respect to reducing upper limb impairments following stroke, however, a larger study is required to confirm this

Observation of Parity Nonconservation in Møller Scattering

We report a measurement of the parity-violating asymmetry in fixed target electron-electron (Møller) scattering: A_(PV) = [-175 ± 30(stat)± 20(syst)] X 10^(-9). This first direct observation of parity nonconservation in Møller scattering leads to a measurement of the electron’s weak charge at low energy Q^e_W = -0:053 ± 0:011. This is consistent with the standard model expectation at the current level of precision: sin^2θ_W = (M_Z)_(MS) = 0:2293 ± 0:0024(stat) ± 0:0016(syst) ± 0:0006(theory)

Binary black hole merger gravitational waves and recoil in the large mass ratio limit

Spectacular breakthroughs in numerical relativity now make it possible to compute spacetime dynamics in almost complete generality, allowing us to model the coalescence and merger of binary black holes with essentially no approximations. The primary limitation of these calculations is now computational. In particular, it is difficult to model systems with large mass ratio and large spins, since one must accurately resolve the multiple lengthscales which play a role in such systems. Perturbation theory can play an important role in extending the reach of computational modeling for binary systems. In this paper, we present first results of a code which allows us to model the gravitational waves generated by the inspiral, merger, and ringdown of a binary system in which one member of the binary is much more massive than the other. This allows us to accurately calibrate binary dynamics in the large mass ratio regime. We focus in this analysis on the recoil imparted to the merged remnant by these waves. We closely examine the "antikick", an anti-phase cancellation of the recoil arising from the plunge and ringdown waves, described in detail by Schnittman et al. We find that, for orbits aligned with the black hole spin, the antikick grows as a function of spin. The total recoil is smallest for prograde coalescence into a rapidly rotating black hole, and largest for retrograde coalescence. Amusingly, this completely reverses the predicted trend for kick versus spin from analyses that only include inspiral information.Comment: 15 pages, 5 figures. Submitted to Phys. Rev.