19,037 research outputs found
An intrinsic state for an extended version of the interacting boson model
An intrinsic-state formalism for IBM-4 is presented. A basis of deformed
bosons is introduced which allows the construction of a general trial wave
function which has Wigner's spin-isospin SU(4) symmetry as a particular limit.
Intrinsic-state calculations are compared with exact ones showing good
agreement.Comment: 12 pages, TeX (ReVTeX). Content changed. Accepted in Phys. Rev.
Glassy phases and driven response of the phase-field-crystal model with random pinning
We study the structural correlations and the nonlinear response to a driving
force of a two-dimensional phase-field-crystal model with random pinning. The
model provides an effective continuous description of lattice systems in the
presence of disordered external pinning centers, allowing for both elastic and
plastic deformations. We find that the phase-field crystal with disorder
assumes an amorphous glassy ground state, with only short-ranged positional and
orientational correlations even in the limit of weak disorder. Under increasing
driving force, the pinned amorphous-glass phase evolves into a moving
plastic-flow phase and then finally a moving smectic phase. The transverse
response of the moving smectic phase shows a vanishing transverse critical
force for increasing system sizes
Gas gun shock experiments with single-pulse x-ray phase contrast imaging and diffraction at the Advanced Photon Source
The highly transient nature of shock loading and pronounced microstructure
effects on dynamic materials response call for {\it in situ}, temporally and
spatially resolved, x-ray-based diagnostics. Third-generation synchrotron x-ray
sources are advantageous for x-ray phase contrast imaging (PCI) and diffraction
under dynamic loading, due to their high photon energy, high photon fluxes,
high coherency, and high pulse repetition rates. The feasibility of bulk-scale
gas gun shock experiments with dynamic x-ray PCI and diffraction measurements
was investigated at the beamline 32ID-B of the Advanced Photon Source. The
x-ray beam characteristics, experimental setup, x-ray diagnostics, and static
and dynamic test results are described. We demonstrate ultrafast, multiframe,
single-pulse PCI measurements with unprecedented temporal (100 ps) and
spatial (2 m) resolutions for bulk-scale shock experiments, as well
as single-pulse dynamic Laue diffraction. The results not only substantiate the
potential of synchrotron-based experiments for addressing a variety of shock
physics problems, but also allow us to identify the technical challenges
related to image detection, x-ray source, and dynamic loading
Short-range charge-order in NiO perovskites (=Pr,Nd,Eu) probed by X-ray absorption spectroscopy
The short-range organization around Ni atoms in orthorhombic NiO
(=Pr,Nd,Eu) perovskites has been studied over a wide temperature range by Ni
K-edge x-ray absorption spectroscopy. Our results demonstrate that two
different Ni sites, with different average Ni-O bond lengths, coexist in those
orthorhombic compounds and that important modifications in the Ni nearest
neighbors environment take place across the metal-insulator transition. We
report evidences for the existence of short-range charge-order in the
insulating state, as found in the monoclinic compounds. Moreover, our results
suggest that the two different Ni sites coexists even in the metallic state.
The coexistence of two different Ni sites, independently on the ion,
provides a common ground to describe these compounds and shed new light in the
understanding of the phonon-assisted conduction mechanism and unusual
antiferromagnetism present in all NiO compounds.Comment: 4 pages, 3 figures, accepted PRB - Brief Report Dec.200
Água necessária no período seco para irrigação do coqueiro anão no Distrito Federal.
bitstream/CPAC-2010/30266/1/bolpd-222.pd
First Results of the Phase II SIMPLE Dark Matter Search
We report results of a 14.1 kgd measurement with 15 superheated droplet
detectors of total active mass 0.208 kg, comprising the first stage of a 30 kgd
Phase II experiment. In combination with the results of the neutron-spin
sensitive XENON10 experiment, these results yield a limit of |a_p| < 0.32 for
M_W = 50 GeV/c2 on the spin-dependent sector of weakly interacting massive
particle-nucleus interactions with a 50% reduction in the previously allowed
region of the phase space formerly defined by XENON, KIMS and PICASSO. In the
spin-independent sector, a limit of 2.3x10-5 pb at M_W = 45 GeV/c2 is obtained.Comment: 4 pages, 4 figures; PRL-accepted version with corrected SI contour
(Fig. 4
Fast high fidelity quantum non-demolition qubit readout via a non-perturbative cross-Kerr coupling
Qubit readout is an indispensable element of any quantum information
processor. In this work, we experimentally demonstrate a non-perturbative
cross-Kerr coupling between a transmon and a polariton mode which enables an
improved quantum non-demolition (QND) readout for superconducting qubits. The
new mechanism uses the same experimental techniques as the standard QND qubit
readout in the dispersive approximation, but due to its non-perturbative
nature, it maximizes the speed, the single-shot fidelity and the QND properties
of the readout. In addition, it minimizes the effect of unwanted decay channels
such as the Purcell effect. We observed a single-shot readout fidelity of 97.4%
for short 50 ns pulses, and we quantified a QND-ness of 99% for long
measurement pulses with repeated single-shot readouts
Towards a FPGA-controlled deep phase modulation interferometer
Deep phase modulation interferometry was proposed as a method to enhance
homodyne interferometers to work over many fringes. In this scheme, a
sinusoidal phase modulation is applied in one arm while the demodulation takes
place as a post-processing step. In this contribution we report on the
development to implement this scheme in a fiber coupled interferometer
controlled by means of a FPGA, which includes a LEON3 soft-core processor. The
latter acts as a CPU and executes a custom made application to communicate with
a host PC. In contrast to usual FPGA-based designs, this implementation allows
a real-time fine tuning of the parameters involved in the setup, from the
control to the post-processing parameters.Comment: Proceedings of the X LISA Symposium, Gainesville, May 18-23, 201
Conteúdo de Ca, Cu, Fe, K, Mg, Mn, Na e Zn em chás de Cecropia palmata Willd.
A espécie Cecropia palmata é tradicionalmente conhecida na Região Norte como embaúba vermelha. O objetivo deste trabalho foi avaliar a composição mineral de chás de folhas Cecropia palmata (embaúba vermelha) em diferentes sazonalidades e certificar suas propriedades nutricionais. A composição mineral foi determinada através de espectrometria. Os resultados mostraram que o período mais chuvoso contribuiu para o aumento da concentração de Cu e o período menos chuvoso o de Na. Os teores dos minerais obtidos em uma xícara de chá padrão não ultrapassam os valores do limite máximo tolerável (UL)
Analyzing the House Fly's Exploratory Behavior with Autoregression Methods
This paper presents a detailed characterization of the trajectory of a single
housefly with free range of a square cage. The trajectory of the fly was
recorded and transformed into a time series, which was fully analyzed using an
autoregressive model, which describes a stationary time series by a linear
regression of prior state values with the white noise. The main discovery was
that the fly switched styles of motion from a low dimensional regular pattern
to a higher dimensional disordered pattern. This discovered exploratory
behavior is, irrespective of the presence of food, characterized by anomalous
diffusion.Comment: 20 pages, 9 figures, 1 table, full pape
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