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SLS Processing Studies of Nylon 11 Nanocomposites
Selective Laser Sintering (SLS) is widely used for rapid prototyping/manufacturing of
nylon 11 and nylon 12 parts. This processing technique has not been explored for
nylon nanocomposites. This study investigates the technicalities of processing nylon
11-clay and nylon-carbon nanofiber nanocomposites with SLS. Microstructural
analyses of the SLS powders and parts were conducted under SEM. Results suggest
that SLS processing is possible with the new nylon 11 nanocomposites. Yet the SLS
parts built have inferior properties relative to those of injection molding, suggesting
that more fine tuning for the processing is required.Mechanical Engineerin
Limits on MeV Dark Matter from the Effective Number of Neutrinos
Thermal dark matter that couples more strongly to electrons and photons than
to neutrinos will heat the electron-photon plasma relative to the neutrino
background if it becomes nonrelativistic after the neutrinos decouple from the
thermal background. This results in a reduction in N_eff below the
standard-model value, a result strongly disfavored by current CMB observations.
Taking conservative lower bounds on N_eff and on the decoupling temperature of
the neutrinos, we derive a bound on the dark matter particle mass of m_\chi >
3-9 MeV, depending on the spin and statistics of the particle. For p-wave
annihilation, our limit on the dark matter particle mass is stronger than the
limit derived from distortions to the CMB fluctuation spectrum produced by
annihilations near the epoch of recombination.Comment: 5 pages, 1 figure, discussion added, references added and updated,
labels added to figure, to appear in Phys. Rev.
Quantum transport through a deformable molecular transistor
The linear transport properties of a model molecular transistor with
electron-electron and electron-phonon interactions were investigated
analytically and numerically. The model takes into account phonon modulation of
the electronic energy levels and of the tunnelling barrier between the molecule
and the electrodes. When both effects are present they lead to asymmetries in
the dependence of the conductance on gate voltage. The Kondo effect is observed
in the presence of electron-phonon interactions. There are important
qualitative differences between the cases of weak and strong coupling. In the
first case the standard Kondo effect driven by spin fluctuations occurs. In the
second case, it is driven by charge fluctuations. The Fermi-liquid relation
between the spectral density of the molecule and its charge is altered by
electron-phonon interactions. Remarkably, the relation between the
zero-temperature conductance and the charge remains unchanged. Therefore, there
is perfect transmission in all regimes whenever the average number of electrons
in the molecule is an odd integer.Comment: 9 pages, 6 figure
Branes from a non-Abelian (2,0) tensor multiplet with 3-algebra
In this paper, we study the equations of motion for non-Abelian N=(2,0)
tensor multiplets in six dimensions, which were recently proposed by Lambert
and Papageorgakis. Some equations are regarded as constraint equations. We
employ a loop extension of the Lorentzian three-algebra (3-algebra) and examine
the equations of motion around various solutions of the constraint equations.
The resultant equations take forms that allow Lagrangian descriptions. We find
various (5+d)-dimensional Lagrangians and investigate the relation between them
from the viewpoint of M-theory duality.Comment: 44+1 pages, reference added, typos corrected, and several discussions
added; v3, reference added, many typos corrected, the language improved; v4,
some typos and references corrected, final version to appear in J. Phys.
Observation of Mass Transport through Solid 4He
By use of a novel experimental design, one that provides for superfluid
helium in contact with bulk hcp 4He off the melting curve, we have observed the
DC transport of mass through a cell filled with solid 4He in the hcp region of
the phase diagram. Flow, which shows characteristics of a superflow, is seen to
be independent of the method used to grow the solid, but depends on pressure
and temperature. The temperature dependence suggests the possibility of
hysteresis.Comment: 1 zipped file, produces 16 page paper, with 20 figures; resubmitted
with typos corrected, a figure corrected, some discussion improved, and
additional references - still 16 pages and 20 figure
Parasitic copepods from Egyptian Red Sea fishes: Bomolochidae Claus, 1875
© The Author(s) 2015
Open Access - This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The attached file is the published version of the article
Limits on thermal variations in a dozen quiescent neutron stars over a decade
In quiescent low-mass X-ray binaries (qLMXBs) containing neutron stars, the
origin of the thermal X-ray component may be either release of heat from the
core of the neutron star, or continuing low-level accretion. In general, heat
from the core should be stable on timescales years, while continuing
accretion may produce variations on a range of timescales. While some quiescent
neutron stars (e.g. Cen X-4, Aql X-1) have shown variations in their thermal
components on a range of timescales, several others, particularly those in
globular clusters with no detectable nonthermal hard X-rays (fit with a
powerlaw), have shown no measurable variations. Here, we constrain the spectral
variations of 12 low mass X-ray binaries in 3 globular clusters over
years. We find no evidence of variations in 10 cases, with limits on
temperature variations below 11% for the 7 qLMXBs without powerlaw components,
and limits on variations below 20% for 3 other qLMXBs that do show non-thermal
emission. However, in 2 qLMXBs showing powerlaw components in their spectra
(NGC 6440 CX 1 & Terzan 5 CX 12) we find marginal evidence for a 10% decline in
temperature, suggesting the presence of continuing low-level accretion. This
work adds to the evidence that the thermal X-ray component in quiescent neutron
stars without powerlaw components can be explained by heat deposited in the
core during outbursts. Finally, we also investigate the correlation between
hydrogen column density (N) and optical extinction (A) using our sample
and current models of interstellar X-ray absorption, finding .Comment: 16 pages, 5 figures, MNRAS, in pres
Third-order many-body perturbation theory calculations for the beryllium and magnesium isoelectronic sequences
Relativistic third-order MBPT is applied to obtain energies of ions with two
valence electrons in the no virtual-pair approximation (NVPA). A total of 302
third-order Goldstone diagrams are organized into 12 one-body and 23 two-body
terms. Only third-order two-body terms and diagrams are presented here, owing
to the fact that the one-body terms are identical to the previously studied
third-order terms in monovalent ions. Dominant classes of diagrams are
identified. The model potential is a Dirac-Hartree-Fock potential,
and B-spline basis functions in a cavity of finite radius are employed in the
numerical calculations. The Breit interaction is taken into account through
second order of perturbation theory and the lowest-order Lamb shift is also
evaluated. Sample calculations are performed for berylliumlike ions with Z =
4--7, and for the magnesiumlike ion P IV. The third-order energies are in
excellent agreement with measurement with an accuracy at 0.2% level for the
cases considered. Comparisons are made with previous second-order MBPT results
and with other calculations. The third-order energy correction is shown to be
significant, improving second-order correlation energies by an order of
magnitude
Two--Electron Atoms in Short Intense Laser Pulses
We discuss a method of solving the time dependent Schrodinger equation for
atoms with two active electrons in a strong laser field, which we used in a
previous paper [A. Scrinzi and B. Piraux, Phys. Rev. A 56, R13 (1997)] to
calculate ionization, double excitation and harmonic generation in Helium by
short laser pulses. The method employs complex scaling and an expansion in an
explicitly correlated basis. Convergence of the calculations is documented and
error estimates are provided. The results for Helium at peak intensities up to
10^15 W/cm^2 and wave length 248 nm are accurate to at least 10 %. Similarly
accurate calculations are presented for electron detachment and double
excitation of the negative hydrogen ion.Comment: 14 pages, including figure
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