540 research outputs found
Model for reflection and transmission matrices of nanowire end facets
Nanowires show a large potential for various electrooptical devices, such as
light emitting diodes, solar cells and nanowire lasers. We present a direct
method developed to calculate the modal reflection and transmission matrix at
the end facets of a waveguide of arbitrary cross section, resulting in a
generalized version of the Fresnel equations. The reflection can be
conveniently computed using Fast Fourier Transforms. We demonstrate that the
reflection is qualitatively described by two main parameters, the modal field
confinement and the average Fresnel reflection of the plane waves constituting
the waveguide mode.Comment: 11 pages,14 figure
Air Permeability, Shrinkage, And Moisture Sorption of Lodgepole Pine Stemwood
The longitudinal air permeabilities, shrinkage (from fully swollen to oven-dry), and moisture sorption characteristics of two varieties (latifotia and murrayana) of lodgepole pine (Pinus contorta) were measured, based on wood samples taken from ten latitudes (37.5° to to 60°N) in western North America, from 279 trees of three diameter classes (76, 152, 228 mm DBH).The mean permeabilities of the sapwood and heartwood were 0.13 and 0.014 darcy, respectively. Geographical latitude and elevation of trees did not affect permeability. The mean calculated radius of pit pores in the sapwood was 1.5 μm, with median values between 12-13 pit pores per mm2. There was a fair correlation between water retention in an empirical water-soaking test and axial gas permeability.The volumetric and radial shrinkages, as well as the ratio of radial to tangential shrinkage, all increased with increasing specific gravity for both varieties. Tree size and latitude also affected shrinkage somewhat, primarily through their effects on specific gravity. The mean ratio of percent volumetric shrinkage to specific gravity was 30.7 2.9% for the two varieties combined.The moisture sorption study gave adsorption and desorption equilibrium moisture content (EMC) values at 30 C at relative humidities of 34.4, 65.0, and 83.2% for both varieties, on each of 62 test samples, representing the three different tree sizes and nine different latitudes. The mean adsorption-desorption (A/D) ratio was 0.79. The EMCs generally decreased with increasing latitude, with no significant difference between varieties at corresponding latitudes
Secure gated detection scheme for quantum cryptography
Several attacks have been proposed on quantum key distribution systems with
gated single-photon detectors. The attacks involve triggering the detectors
outside the center of the detector gate, and/or using bright illumination to
exploit classical photodiode mode of the detectors. Hence a secure detection
scheme requires two features: The detection events must take place in the
middle of the gate, and the detector must be single-photon sensitive. Here we
present a technique called bit-mapped gating, which is an elegant way to force
the detections in the middle of the detector gate by coupling detection time
and quantum bit error rate. We also discuss how to guarantee single-photon
sensitivity by directly measuring detector parameters. Bit-mapped gating also
provides a simple way to measure the detector blinding parameter in security
proofs for quantum key distribution systems with detector efficiency mismatch,
which up until now has remained a theoretical, unmeasurable quantity. Thus if
single-photon sensitivity can be guaranteed within the gates, a detection
scheme with bit-mapped gating satisfies the assumptions of the current security
proofs.Comment: 7 pages, 3 figure
A two week regimen of high dose integrase inhibitors does not cause nephrotoxicity in mice
Background The integrase inhibitors, raltegravir and dolutegravir, are nucleoside reverse transcriptase inhibitor-sparing agents which may be used as part of first-line antiretroviral therapy for HIV. These drugs inhibit creatinine secretion through organic cation transporters, thus elevating serum creatinine without affecting glomerular filtration. We sought to determine whether subtle signs of nephrotoxicity could be observed in mice administered a two-week regimen of high-dose integrase inhibitors.
Methods C57BL/6 mice were fed standard water (CTRL, n = 6), raltegravir-containing water (40 mg/kg/day, n = 6), or dolutegravir-containing water (2.7 mg/kg/day, n = 6) for two weeks and sacrificed. Endpoints were assessed including urine microalbumin, kidney injury molecule-1 renal tissue gene expression, renal histopathology, serum creatinine, and blood urea nitrogen.
Results The results are NOT consistent with a direct nephrotoxic effect of the integrase inhibitors in mice. Serum creatinine was significantly elevated in raltegravir and dolutegravir mice (p < 0.05) compared to control (raltegravir = 0.25 mg/dl, dolutegravir = 0.30 mg/dl versus CTRL = 0.17 mg/dl). Blood urea nitrogen, cystatin C, and urine microalbumin were unchanged. Kidney injury molecule-1 tissue expression in raltegravir and dolutegravir groups was nonsignificantly elevated compared to control (1.2-fold compared to control). Renal histopathology by periodic acid–Schiff staining failed to reveal glomerular or tubular renal injury in any group.
Conclusion These studies are consistent with integrase inhibitors competitively inhibiting creatinine secretion. While no evidence of direct nephrotoxicity was observed after two weeks of high-dose drug administration, additional studies may be performed to understand whether these drugs lead to chronic nephropathy
Experimental demonstration of phase-remapping attack in a practical quantum key distribution system
Unconditional security proofs of various quantum key distribution (QKD)
protocols are built on idealized assumptions. One key assumption is: the sender
(Alice) can prepare the required quantum states without errors. However, such
an assumption may be violated in a practical QKD system. In this paper, we
experimentally demonstrate a technically feasible "intercept-and-resend" attack
that exploits such a security loophole in a commercial "plug & play" QKD
system. The resulting quantum bit error rate is 19.7%, which is below the
proven secure bound of 20.0% for the BB84 protocol. The attack we utilize is
the phase-remapping attack (C.-H. F. Fung, et al., Phys. Rev. A, 75, 32314,
2007) proposed by our group.Comment: 16 pages, 6 figure
Autonomous Robust Skill Generation Using Reinforcement Learning with Plant Variation
This paper discusses an autonomous space robot for a truss structure assembly using some reinforcement learning. It is difficult for a space robot to complete contact tasks within a real environment, for example, a peg-in-hole task, because of error between the real environment and the controller model. In order to solve problems, we propose an autonomous space robot able to obtain proficient and robust skills by overcoming error to complete a task. The proposed approach develops skills by reinforcement learning that considers plant variation, that is, modeling error. Numerical simulations and experiments show the proposed method is useful in real environments
Dispersive properties of quasi-phase-matched optical parametric amplifiers
The dispersive properties of non-degenerate optical parametric amplification
in quasi-phase-matched (QPM) nonlinear quadratic crystals with an arbitrary
grating profile are theoretically investigated in the no-pump-depletion limit.
The spectral group delay curve of the amplifier is shown to be univocally
determined by its spectral power gain curve through a Hilbert transform. Such a
constraint has important implications on the propagation of spectrally-narrow
optical pulses through the amplifier. In particular, it is shown that anomalous
transit times, corresponding to superluminal or even negative group velocities,
are possible near local minima of the spectral gain curve. A possible
experimental observation of such effects using a QPM Lithium-Niobate crystal is
suggested.Comment: submitted for publicatio
CYP genotypes influence the effect of tamoxifen therapy on serum lipids
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110066/1/cptclpt2004270.pd
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