28,770 research outputs found
Economic method for measuring ultra-low flow rates of fluids
Capillary tube flowmeter measures ultra-low flows of very corrosive fluids /such as chlorine trifluoride and liquid fluorine/ and other liquids with reasonable accuracy. Flowmeter utilizes differential pressure transducer and operates on the principle that for laminar flow in the tube, pressure drop is proportional to flow rate
Scalable photonic quantum computation through cavity-assisted interaction
We propose a scheme for scalable photonic quantum computation based on cavity
assisted interaction between single-photon pulses. The prototypical quantum
controlled phase-flip gate between the single-photon pulses is achieved by
successively reflecting them from an optical cavity with a single-trapped atom.
Our proposed protocol is shown to be robust to practical nose and experimental
imperfections in current cavity-QED setups.Comment: 5 pages, 2 figure
Momentum-resolved electron-phonon interaction in lead determined by neutron resonance spin-echo spectroscopy
Neutron resonance spin-echo spectroscopy was used to monitor the temperature
evolution of the linewidths of transverse acoustic phonons in lead across the
superconducting transition temperature, , over an extended range of the
Brillouin zone. For phonons with energies below the superconducting energy gap,
a linewidth reduction of maximum amplitude eV was observed below
. The electron-phonon contribution to the phonon lifetime extracted from
these data is in satisfactory overall agreement with {\it ab-initio}
lattice-dynamical calculations, but significant deviations are found
Neutron spin-echo study of the critical dynamics of spin-5/2 antiferromagnets in two and three dimensions
We report a neutron spin-echo study of the critical dynamics in the
antiferromagnets MnF and RbMnF with three-dimensional (3D) and
two-dimensional (2D) spin systems, respectively, in zero external field. Both
compounds are Heisenberg antiferromagnets with a small uniaxial anisotropy
resulting from dipolar spin-spin interactions, which leads to a crossover in
the critical dynamics close to the N\'eel temperature, . By taking
advantage of the energy resolution of the spin-echo
spectrometer, we have determined the dynamical critical exponents for both
longitudinal and transverse fluctuations. In MnF, both the characteristic
temperature for crossover from 3D Heisenberg to 3D Ising behavior and the
exponents in both regimes are consistent with predictions from the
dynamical scaling theory. The amplitude ratio of longitudinal and transverse
fluctuations also agrees with predictions. In RbMnF, the critical
dynamics crosses over from the expected 2D Heisenberg behavior for
to a scaling regime with exponent , which has not been predicted
by theory and may indicate the influence of long-range dipolar interactions
The physical determinants of the thickness of lamellar polymer crystals
Based upon kinetic Monte Carlo simulations of crystallization in a simple
polymer model we present a new picture of the mechanism by which the thickness
of lamellar polymer crystals is constrained to a value close to the minimum
thermodynamically stable thickness. This description contrasts with those given
by the two dominant theoretical approaches.Comment: 4 pages, 4 figures, revte
An absorption spectrum amplifier for determining gas composition
Compositions of gas samples are frequently studied by laser absorption spectroscopy. Sensitivity is improved by two orders of magnitude when absorption cell is placed inside an organic-dye laser cavity
Evidence for complex order parameter in La_{1.83}Sr_{0.17}CuO_4
The in-plane magnetic field penetration depth (\lambda_{ab}) in
single-crystal La_{1.83}Sr_{0.17}CuO_4 was investigated by means of the
muon-spin rotation (\muSR) technique. The temperature dependence of
\lambda^{-2}_{ab} has an inflection point around 10-15K, suggesting the
presence of two superconducting gaps: a large gap (\Delta_1^d) with d-wave and
a small gap (\Delta_2^s) with s-wave symmetry. The zero-temperature values of
the gaps at \mu_0H=0.02T were found to be \Delta_1^d(0)=8.2(2)meV and
\Delta_2^s(0)=1.57(8)meV.Comment: 5 pages, 3 figure
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