11,049 research outputs found
Measurements of the effect of horizontal variability of atmospheric backscatter on dial measurements
The horizontal variability of atmospheric backscatter may have a substantial effect on how Differential Absorption Lidar (DIAL) data must be taken and analyzed. To minimize errors, lidar pulse pairs are taken with time separations which are short compared to the time scales associated with variations in atmospheric backscatter. To assess the atmospheric variability for time scales which are long compared to the lidar pulse repetition rate, the variance of the lidar return signal in a given channel can be computed. The variances of the on-line, off-line, and ration of the on-line to off-line signals at given altitudes obtained with the dual solid-state Alexandrite laser system were calculated. These evaluations were made for both down-looking aircraft and up-looking ground-based lidar data. Data were taken with 200 microsecond separation between on-line and off-line laser pulses, 30 m altitude resolution, 5 Hz repetition rate, and the signal were normalized for outgoing laser energy
Concepts, Developments and Advanced Applications of the PAX Toolkit
The Physics Analysis eXpert (PAX) is an open source toolkit for high energy
physics analysis. The C++ class collection provided by PAX is deployed in a
number of analyses with complex event topologies at Tevatron and LHC. In this
article, we summarize basic concepts and class structure of the PAX kernel. We
report about the most recent developments of the kernel and introduce two new
PAX accessories. The PaxFactory, that provides a class collection to facilitate
event hypothesis evolution, and VisualPax, a Graphical User Interface for PAX
objects
Cascaded acceleration of proton beams in ultrashort laser-irradiated microtubes
A cascaded ion acceleration scheme is proposed by use of ultrashort
laser-irradiated microtubes. When the electrons of a microtube are blown away
by intense laser pulses, strong charge-separation electric fields are formed in
the microtube both along the axial and along the radial directions. By
controlling the time delay between the laser pulses and a pre-accelerated
proton beam injected along the microtube axis, we demonstrate that this proton
beam can be further accelerated by the transient axial electric field in the
laser-irradiated microtube. Moreover, the collimation of the injected proton
beam can be enhanced by the inward radial electric field. Numerical simulations
show that this cascaded ion acceleration scheme works efficiently even at
non-relativistic laser intensities, and it can be applied to injected proton
beams in the energy range from 1 to 100 MeV. Therefore, it is particularly
suitable for cascading acceleration of protons to higher energy.Comment: 13 pages, 4 figure
Mean-Field Description of Phase String Effect in the Model
A mean-field treatment of the phase string effect in the model is
presented. Such a theory is able to unite the antiferromagnetic (AF) phase at
half-filling and metallic phase at finite doping within a single theoretical
framework. We find that the low-temperature occurrence of the AF long range
ordering (AFLRO) at half-filling and superconducting condensation in metallic
phase are all due to Bose condensations of spinons and holons, respectively, on
the top of a spin background described by bosonic resonating-valence-bond (RVB)
pairing. The fact that both spinon and holon here are bosonic objects, as the
result of the phase string effect, represents a crucial difference from the
conventional slave-boson and slave-fermion approaches. This theory also allows
an underdoped metallic regime where the Bose condensation of spinons can still
exist. Even though the AFLRO is gone here, such a regime corresponds to a
microscopic charge inhomogeneity with short-ranged spin ordering. We discuss
some characteristic experimental consequences for those different metallic
regimes. A perspective on broader issues based on the phase string theory is
also discussed.Comment: 18 pages, five figure
Un nuevo antioxidante: 6,6'-(butano-1,1-diil)bis(4-metil-benceno-1,2-diol)
A novel compound, 6,6'-(butane-1,1-diyl)bis(4-methylbenzene-1,2-diol) (BMB), was synthesized through an acid-catalyzed condensation reaction between 4-methylcatechol (HPC) and butyraldehyde. When evaluated by the Rancimat and deep frying methods, BMB exhibited a stronger antioxidant activity than TBHQ. Its DPPH radical scavenging activity was also fairly higher than TBHQ, but lower compared to its mother phenol, HPC, due to its relative ease of binding DPPH•. BMB had the strongest scavenging ability of the 4-methylcatechol analogues reported to date. It could be used effectively to retard lipid peroxidation in both moderate and high temperature food preparations.Un nuevo compuesto, 6,6'-(butano-1,1-diil)bis(4-metilbenceno-1,2-diol) (BMB) fue sintetizado mediante una reacción de condensación catalizada por ácido entre el 4-metilcatecol (HPC) y el butiraldehÃdo. Cuando se evaluó mediante los métodos Rancimat y de fritura, el BMB mostró una actividad antioxidante más fuerte que el TBHQ. Su actividad de eliminación de radicales DPPH también fue bastante mayor que la del TBHQ, pero menor en comparación con el fenol de partida, HPC, debido a su relativa facilidad para unirse a DPPH•. BMB tiene una actividad de eliminación más fuerte que los análogos de 4-metilcatecol reportados hasta la fecha. PodrÃa usarse eficazmente para retardar la peroxidación de lÃpidos en la preparación de alimentos a temperatura moderada y alta
Magnetic Incommensurability in Doped Mott Insulator
In this paper we explore the incommensurate spatial modulation of spin-spin
correlations as the intrinsic property of the doped Mott insulator, described
by the model. We show that such an incommensurability is a direct
manifestation of the phase string effect introduced by doped holes in both one-
and two-dimensional cases. The magnetic incommensurate peaks of dynamic spin
susceptibility in momentum space are in agreement with the neutron-scattering
measurement of cuprate superconductors in both position and doping dependence.
In particular, this incommensurate structure can naturally reconcile the
neutron-scattering and NMR experiments of cuprates.Comment: 12 pages (RevTex), five postscript figure
Ginzburg-Landau Expansion in Non-Fermi Liquid Superconductors: Effect of the Mass Renormalization Factor
We reconsider the Ginzburg-Landau expansion for the case of a non-Fermi
liquid superconductor. We obtain analytical results for the Ginzburg-Landau
functional in the critical region around the superconducting phase transition,
T <= T_c, in two special limits of the model, i.e., the spin-charge separation
case and the anomalous Fermi liquid case. For both cases, in the presence of a
mass renormalization factor, we derived the form and the specific dependence of
the coherence length, penetration depth, specific heat jump at the critical
point, and the magnetic upper critical field. For both limits the obtained
results reduce to the usual BCS results for a two dimensional s-wave
superconductor. We compare our results with recent and relevant theoretical
work. The results for a d--wave symmetry order parameter do not change
qualitatively the results presented in this paper. Only numerical factors
appear additionally in our expressions.Comment: accepted for publication in Physical Review
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