1,655 research outputs found
The Amplitude of Non-Equilibrium Quantum Interference in Metallic Mesoscopic Systems
We study the influence of a DC bias voltage V on quantum interference
corrections to the measured differential conductance in metallic mesoscopic
wires and rings. The amplitude of both universal conductance fluctuations (UCF)
and Aharonov-Bohm effect (ABE) is enhanced several times for voltages larger
than the Thouless energy. The enhancement persists even in the presence of
inelastic electron-electron scattering up to V ~ 1 mV. For larger voltages
electron-phonon collisions lead to the amplitude decaying as a power law for
the UCF and exponentially for the ABE. We obtain good agreement of the
experimental data with a model which takes into account the decrease of the
electron phase-coherence length due to electron-electron and electron-phonon
scattering.Comment: New title, refined analysis. 7 pages, 3 figures, to be published in
Europhysics Letter
Detection of very-high-energy gamma-ray emission from the vicinity of PSR B1706-44 with H.E.S.S
The energetic pulsar PSR B1706-44 and the adjacent supernova remnant (SNR)
candidate G 343.1-2.3 were observed by H.E.S.S. during a dedicated
observational campaign in 2007. A new source of very-high-energy (VHE; E > 100
GeV) gamma-ray emission, HESS J1708-443, was discovered with its centroid at
RA(J2000) = 17h08m10s and Dec(J2000) = -44d21', with a statistical error of 3
arcmin on each axis. The VHE gamma-ray source is significantly more extended
than the H.E.S.S. point-spread function, with an intrinsic Gaussian width of
0.29 +/- 0.04 deg. Its energy spectrum can be described by a power law with a
photon index Gamma = 2.0 +/- 0.1 (stat) +/- 0.2 (sys). The integral flux
measured between 1-10 TeV is ~17% of the Crab Nebula flux in the same energy
range. The possible associations with PSR B1706-44 and SNR G343.1-2.3 are
discussed.Comment: 4+ pages, 2 figures; v1 submitted to ICRC Proceedings on 15 May 2009;
v2 has additional references and minor change
Amplitude of Aharonov-Bohm oscillations in mesoscopic metallic rings as a function of the DC bias voltage
We report measurements of the amplitude of the Aharonov-Bohm oscillations in a mesoscopic diffusive gold ring as a function of the DC bias voltage VDC. The amplitude of the h/e oscillations increases with VDC once the Thouless energy Ec and thermal energy are exceeded, and decreases at higher values of VDC. The increase of the amplitude is interpreted in terms of a superposition of the statistically independent contributions of eVDC/Ec energy intervals, whereas its decrease at high VDC could be attributed to enhanced inelastic scattering processes
Amplituda Aharonov-Bohmovih oscilacija u mezoskopskim metalnim prstenovima kao funkcija uzbudnog istosmjernog napona
We report measurements of the amplitude of the Aharonov-Bohm oscillations in a mesoscopic diffusive gold ring as a function of the DC bias voltage VDC. The amplitude of the h/e oscillations increases with VDC once the Thouless energy Ec and thermal energy are exceeded, and decreases at higher values of VDC. The increase of the amplitude is interpreted in terms of a superposition of the statistically independent contributions of eVDC/Ec energy intervals, whereas its decrease at high VDC could be attributed to enhanced inelastic scattering processes.Izvješćujemo o mjerenjima amplitude Aharonov-Bohmovih oscilacija u mezoskopskom zlatnom difuznom prstenu kao funkcije pobudnog istosmjernog napona VDC. Kad se premaše Thoulessova energija Ec i termička energija, amplituda h/e oscilacija raste s VDC, a opada pri većim VDC. Porast amplitude interpretiramo kao zbrajanje doprinosa statistički neovisnih energijskih intervala eVDC/Ec, dok njezin pad pri većim VDC pripisujemo procesima neelastičnih raspršenja
Periodic Modulations in an X-ray Flare from Sagittarius A*
We present the highly significant detection of a quasi-periodic flux
modulation with a period of 22.2 min seen in the X-ray data of the Sgr A* flare
of 2004 August 31. This flaring event, which lasted a total of about three
hours, was detected simultaneously by EPIC on XMM-Newton and the NICMOS
near-infrared camera on the HST. Given the inherent difficulty in, and the lack
of readily available methods for quantifying the probability of a periodic
signal detected over only several cycles in a data set where red noise can be
important, we developed a general method for quantifying the likelihood that
such a modulation is indeed intrinsic to the source and does not arise from
background fluctuations. We here describe this Monte Carlo based method, and
discuss the results obtained by its application to a other XMM-Newton data
sets. Under the simplest hypothesis that we witnessed a transient event that
evolved, peaked and decayed near the marginally stable orbit of the
supermassive black hole, this result implies that for a mass of 3.5 x 10^{6}
Msun, the central object must have an angular momentum corresponding to a spin
parameter of a=0.22.Comment: 4 pages, 6 figures, submitted to ApJ
Current-induced two-level fluctuations in pseudo spin-valves (Co/Cu/Co) nanostructures
Two-level fluctuations of the magnetization state of pseudo spin-valve
pillars Co(10 nm)/Cu(10 nm)/Co(30 nm) embedded in electrodeposited nanowires
(~40 nm in diameter, 6000 nm in length) are triggered by spin-polarized
currents of 10^7 A/cm^2 at room temperature. The statistical properties of the
residence times in the parallel and antiparallel magnetization states reveal
two effects with qualitatively different dependences on current intensity. The
current appears to have the effect of a field determined as the bias field
required to equalize these times. The bias field changes sign when the current
polarity is reversed. At this field, the effect of a current density of 10^7
A/cm^2 is to lower the mean time for switching down to the microsecond range.
This effect is independent of the sign of the current and is interpreted in
terms of an effective temperature for the magnetization.Comment: 4 pages, 5 figures, revised version, to be published in Phys. Rev.
Let
Activity patterns among patients with chronic pain after orthopaedic trauma
ObjectivesActivity patterns influence the development and perpetuation of musculoskeletal pain. To date, three major patterns have been observed in particular on chronic low back pain patients: avoidance, pacing and persistence. Relationships between these behaviours and clinical outcomes remain inconclusive. Moreover, there is only few data on other chronic pain syndromes. Our aim was to identify activity patterns in patients with chronic pain after orthopaedic trauma and to describe relationships with pain, depressive symptomatology and disability.Patients and methodsParticipants were rehab orthopaedic trauma inpatients with chronic pain (mean duration: 9 months). Activity patterns classification was made at entry with the “Patterns of Activity Measure-Pain” (POAM-P) and the Tampa scale for Kinesiophobia (TSK). Outcomes were assessed with the Brief Pain Inventory (BPI), the Hospital Anxiety and Depression scale (HADS), the Spinal Function Sort (SFS: spinal and lower limb trauma) and the Hand Function Sort (HFS: upper limb trauma). Descriptive statistics and ANOVA were used.Results497 inpatients were included (mean age: 43 years; female: 22%). Patterns distribution was: 46% avoidance; 30% pacing and 24% persistence. Kinesiophobia (TSK≥45points) is much more marked in avoidance (71%). Nevertheless, 37% in pacing, 22% in persistence also have kinesiophobia which may suggest the existence of more than three patterns. Outcomes were always poor in avoidance, intermediate in pacing and better in persistence behaviour.DiscussionThe 3 main activity patterns were identified in rehab orthopaedic trauma inpatients. In this cross-sectional study, persistence behaviour was associated with better self-perceptions
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