38,957 research outputs found
Classification of -Wave and Systems
An exotic meson, the with , has been seen to
decay into a p-wave system. If this decay conserves flavor SU(3),
then it can be shown that this exotic meson must be a four-quark state () belonging to a flavor representation
of SU(3). In contrast, the with a substantial decay mode into
is likely to be a member of a flavor octet.Comment: 8 page
Phase equilibrium modeling for high temperature metallization on GaAs solar cells
Recent trends in performance specifications and functional requirements have brought about the need for high temperature metallization technology to be developed for survivable DOD space systems and to enhance solar cell reliability. The temperature constitution phase diagrams of selected binary and ternary systems were reviewed to determine the temperature and type of phase transformation present in the alloy systems. Of paramount interest are the liquid-solid and solid-solid transformations. Data are being utilized to aid in the selection of electrical contact materials to gallium arsenide solar cells. Published data on the phase diagrams for binary systems is readily available. However, information for ternary systems is limited. A computer model is being developed which will enable the phase equilibrium predictions for ternary systems where experimental data is lacking
Covariant Helicity-Coupling Amplitudes: A New Formulation
We have worked out covariant amplitudes for any two-body decay of a resonance
with an arbitrary non-zero mass, which involves arbitrary integer spins in the
initial and the final states. One key new ingredient for this work is the
application of the total intrinsic spin operator which is given
directly in terms of the generators of the Poincar\'e group.
Using the results of this study, we show how to explore the Lorentz factors
which appear naturally, if the momentum-space wave functions are used to form
the covariant decay amplitudes. We have devised a method of constructing our
covariant decay amplitudes, such that they lead to the Zemach amplitudes when
the Lorentz factors are set one
Treehoppers (Hemiptera: Aetalionidae and Membracidae) from Madre de Dios region, Peru
A list of treehoppers (Aetalionidae and Membracidae) is presented from Madre de Dios region at the southeastern Amazon basin in Peru. The treehopper specimens were collected as by-catch in a survey of the beetles in the Villa Carmen Biological Station and Los Amigos Biological Station. The list comprises 44 species, 31 genera, 16 tribes and 9 subfamilies. Ten genera are new records to Peru. The images of representative specimens of each identified species and genera are provided to facilitate the identification of the local treehopper fauna.
Resumen: Se presenta una lista de los membrácidos (Aetalionidae y Membracidae) de la región Madre de Dios, en el sureste de la cuenca Amazónica, en Perú. La lista está basada en especÃmenes recolectados como captura fortuita en un inventario de escarabajos en las estaciones biológicas Villa Carmen y Los Amigos. La lista incluye 44 especies, 31 géneros, 16 tribus y 9 subfamilias. Diez géneros son nuevos registros para Perú. Se presentan las imágenes de especÃmenes representativos de cada especie y género para facilitar la identifición de la fauna local de los membrácidos
Non-monotonic temperature dependent transport in graphene grown by Chemical Vapor Deposition
Temperature-dependent resistivity of graphene grown by chemical vapor
deposition (CVD) is investigated. We observe in low mobility CVD graphene
device a strong insulating behavior at low temperatures and a metallic behavior
at high temperatures manifesting a non-monotonic in the temperature dependent
resistivity.This feature is strongly affected by carrier density modulation. To
understand this anomalous temperature dependence, we introduce thermal
activation of charge carriers in electron-hole puddles induced by randomly
distributed charged impurities. Observed temperature evolution of resistivity
is then understood from the competition among thermal activation of charge
carriers, temperature-dependent screening and phonon scattering effects. Our
results imply that the transport property of transferred CVD-grown graphene is
strongly influenced by the details of the environmentComment: 7 pages, 3 figure
Strong Collapse Turbulence in Quintic Nonlinear Schr\"odinger Equation
We consider the quintic one dimensional nonlinear Schr\"odinger equation with
forcing and both linear and nonlinear dissipation. Quintic nonlinearity results
in multiple collapse events randomly distributed in space and time forming
forced turbulence. Without dissipation each of these collapses produces finite
time singularity but dissipative terms prevents actual formation of
singularity. In statistical steady state of the developed turbulence the
spatial correlation function has a universal form with the correlation length
determined by the modulational instability scale. The amplitude fluctuations at
that scale are nearly-Gaussian while the large amplitude tail of probability
density function (PDF) is strongly non-Gaussian with power-like behavior. The
small amplitude nearly-Gaussian fluctuations seed formation of large collapse
events. The universal spatio-temporal form of these events together with the
PDF for their maximum amplitudes define the power-like tail of PDF for large
amplitude fluctuations, i.e., the intermittency of strong turbulence.Comment: 14 pages, 17 figure
Tau Polarizations in the Three-body Slepton Decays with Stau as the NLSP
In the gauge-mediated supersymmetry breaking models with scalar tau as the
next-to-lightest supersymmetric particle, a scalar lepton may decay dominantly
into its superpartner, tau lepton, and the lightest scalar tau particle. We
give detailed formulas for the three-body decay amplitudes and the polarization
asymmetry of the outgoing tau lepton . We find that the tau polarizations are
sensitive to the model parameters such as the stau mixing angle, the neutralino
to slepton mass ratio and the neutralino mixing effect.Comment: 13 pages, 5 figures, RevTe
Virgo Galaxies with Long One-Sided HI Tails
In a new HI imaging survey of Virgo galaxies (VIVA: VLA Imaging of Virgo
galaxies in Atomic gas), we find 7 spiral galaxies with long HI tails. The
morphology varies but all the tails are extended well beyond the optical radii
on one side. These galaxies are found in intermediate-low density regions
(0.6-1 Mpc in projection from M87). The tails are all pointing roughly away
from M87, suggesting that these tails may have been created by a global cluster
mechanism. While the tidal effects of the cluster potential are too small, a
rough estimate suggests that simple ram-pressure stripping indeed could have
formed the tails in all but two cases. At least three systems show HI
truncation to within the stellar disk, providing evidence for a gas-gas
interaction. Although most of these galaxies do not appear disturbed optically,
some have close neighbors, suggesting that tidal interactions may have moved
gas outwards making it more susceptible to the ICM ram-pressure or viscosity.
Indeed, a simulation study of one of the tail galaxies, NGC 4654, suggests that
the galaxy is most likely affected by the combined effect of a gravitational
interaction and ram-pressure stripping. We conclude that these one-sided HI
tail galaxies have recently arrived in the cluster, falling in on highly radial
orbits. It appears that galaxies begin to lose their gas already at
intermediate distances from the cluster center through ram-pressure or
turbulent viscous stripping and tidal interactions with neighbours, or a
combination of both.Comment: 4 pages, 3 figures (including 1 plate), accepted for accepted for
publication in ApJ Letter (vol. 659, L115), a version with full resolution
Plate 1 is available from
http://www.astro.umass.edu/~achung/astro-ph/viva_tail.pd
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