14,003 research outputs found
Method and apparatus for attaching physiological monitoring electrodes Patent
Adhesive spray process for attaching biomedical skin electrode
Calculation of model Hamiltonian parameters for LaMnO_3 using maximally localized Wannier functions
Maximally localized Wannier functions (MLWFs) based on Kohn-Sham
band-structures provide a systematic way to construct realistic, materials
specific tight-binding models for further theoretical analysis. Here, we
construct MLWFs for the Mn e_g bands in LaMnO_3, and we monitor changes in the
MLWF matrix elements induced by different magnetic configurations and
structural distortions. From this we obtain values for the local Jahn-Teller
and Hund's rule coupling strength, the hopping amplitudes between all nearest
and further neighbors, and the corresponding reduction due to the GdFeO_3-type
distortion. By comparing our results with commonly used model Hamiltonians for
manganites, where electrons can hop between two "e_g-like" orbitals located on
each Mn site, we find that the most crucial limitation of such models stems
from neglecting changes in the underlying Mn(d)-O(p) hybridization.Comment: 15 pages, 11 figures, 3 table
Low level of virological failure and drug resistance among patients receiving antiretroviral treatment under programme conditions in Maputo, Mozambique
Mexico AIDS Conference 200
Complementary optical-potential analysis of alpha-particle elastic scattering and induced reactions at low energies
A previously derived semi-microscopic analysis based on the Double Folding
Model, for alpha-particle elastic scattering on A~100 nuclei at energies below
32 MeV, is extended to medium mass A ~ 50-120 nuclei and energies from ~13 to
50 MeV. The energy-dependent phenomenological imaginary part for this
semi-microscopic optical model potential was obtained including the dispersive
correction to the microscopic real potential, and used within a concurrent
phenomenological analysis of the same data basis. A regional parameter set for
low-energy alpha-particles entirely based on elastic-scattering data analysis
was also obtained for nuclei within the above-mentioned mass and energy ranges.
Then, an ultimate assessment of (alpha,gamma), (alpha,n) and (alpha,p) reaction
cross sections concerned target nuclei from 45Sc to 118Sn and incident energies
below ~12 MeV. The former diffuseness of the real part of optical potential as
well as the surface imaginary-potential depth have been found responsible for
the actual difficulties in the description of these data, and modified in order
to obtain an optical potential which describe equally well both the low energy
elastic-scattering and induced-reaction data of alpha-particles.Comment: 46 pages, 16 figures. n_TOF Collaboration Annual Meeting, Bari,
Italy, 28-30 November 2007
(http://www.cern.ch/ntof/Documents/bari_nov07/bari_slides.php); revised
version accepted for publication in ADND
A study of energy concentration and drain in incompressible fluids
In this paper we examine two opposite scenarios of energy behavior for
solutions of the Euler equation. We show that if is a regular solution on a
time interval and if for some , where is the dimension of the fluid, then the energy at the
time cannot concentrate on a set of Hausdorff dimension samller than . The same holds for solutions of the three-dimensional
Navier-Stokes equation in the range . Oppositely, if the energy
vanishes on a subregion of a fluid domain, it must vanish faster than
(T-t)^{1-\d}, for any \d>0. The results are applied to find new exclusions
of locally self-similar blow-up in cases not covered previously in the
literature.Comment: an update of the previous versio
Factor ordering in standard quantum cosmology
The Wheeler-DeWitt equation of Friedmann models with a massless quantum field
is formulated with arbitrary factor ordering of the Hamiltonian constraint
operator. A scalar product of wave functions is constructed, giving rise to a
probability interpretation and making comparison with the classical solution
possible. In general the bahaviour of the wave function of the model depends on
a critical energy of the matter field, which, in turn, depends on the chosen
factor ordering. By certain choices of the ordering the critical energy can be
pushed down to zero.Comment: 15 pages, 3 figure
Phonon lasing from optical frequency comb illumination of a trapped ion
An atomic transition can be addressed by a single tooth of an optical
frequency comb if the excited state lifetime () is significantly longer
than the pulse repetition period (). In the crossover regime
between fully-resolved and unresolved comb teeth (), we observe Doppler cooling of a pre-cooled trapped atomic ion
by a single tooth of a frequency-doubled optical frequency comb. We find that
for initially hot ions, a multi-tooth effect gives rise to lasing of the ion's
harmonic motion in the trap, verified by acoustic injection locking. The gain
saturation of this phonon laser action leads to a comb of steady-state
oscillation amplitudes, allowing hot ions to be loaded directly into the trap
and laser cooled to crystallization despite the presence of hundreds of
blue-detuned teeth.Comment: 5 pages, 4 figure
Improving light harvesting in polymer photodetector devices through nanoindented metal mask films
To enhance light harvesting in organic photovoltaic devices, we propose the incorporation of a metal (aluminum) mask film in the system’s usual layout. We fabricate devices in a sandwich geometry, where the mask (nanoindented with a periodic array of holes of sizes d and spacing s) is added between the transparent electrode and the active layer formed by a blend of the semiconducting polymer P3HT and substituted fullerene. Its function is to promote trapping of the incident light into the device’s cavity (the region corresponding to the active layer). For d, we set a value that allows light diffraction through the holes in the relevant absorption range of the polymer. To optimize the mask structure, we consider a very simple model to determine the s leading to trapped fields that are relatively intense and homogeneous within the device. From measurements of the action spectra, we show that, indeed, such architecture can considerably improve the resulting photocurrent efficiencies—one order of magnitude in the best situation studied.
Tomographic readout of an opto-mechanical interferometer
The quantum state of light changes its nature when being reflected off a
mechanical oscillator due to the latter's susceptibility to radiation pressure.
As a result, a coherent state can transform into a squeezed state and can get
entangled with the motion of the oscillator. The complete tomographic
reconstruction of the state of light requires the ability to readout arbitrary
quadratures. Here we demonstrate such a readout by applying a balanced homodyne
detector to an interferometric position measurement of a thermally excited
high-Q silicon nitride membrane in a Michelson-Sagnac interferometer. A readout
noise of \unit{1.9 \cdot 10^{-16}}{\metre/\sqrt{\hertz}} around the
membrane's fundamental oscillation mode at \unit{133}{\kilo\hertz} has been
achieved, going below the peak value of the standard quantum limit by a factor
of 8.2 (9 dB). The readout noise was entirely dominated by shot noise in a
rather broad frequency range around the mechanical resonance.Comment: 7 pages, 5 figure
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