3,482 research outputs found
Effects of cobalt in nickel-base superalloys
The role of cobalt in a representative wrought nickel-base superalloy was determined. The results show cobalt affecting the solubility of elements in the gamma matrix, resulting in enhanced gamma' volume fraction, in the stabilization of MC-type carbides, and in the stabilization of sigma phase. In the particular alloy studied, these microstructural and microchemistry changes are insufficient in extent to impact on tensile strength, yield strength, and in the ductilities. Depending on the heat treatment, creep and stress rupture resistance can be cobalt sensitive. In the coarse grain, fully solutioned and aged condition, all of the alloy's 17% cobalt can be replaced by nickel without deleteriously affecting this resistance. In the fine grain, partially solutioned and aged condition, this resistance is deleteriously affected only when one-half or more of the initial cobalt content is removed. The structure and property results are discussed with respect to existing theories and with respect to other recent and earlier findings on the impact of cobalt, if any, on the performance of nickel-base superalloys
Small coherence peak near in unconventional superconductors
It is usually believed that a coherence peak just below T in the
nuclear spin lattice relaxation rate T in superconducting materials
is a signature of conventional s-wave pairing. In this paper we demonstrate
that any unconventional superconductor obeying BCS pure-case weak-coupling
theory should show a small T coherence peak near T, generally
with a height between 3 and 15 percent greater than the normal state
T at T. It is largely due to impurity effects that this peak
has not commonly been observed.Comment: 4 pages, 5 figure
Integrated Optics: a Report on the 2nd OSA Topical Meeting
This report surveys the papers presented at the 2nd OSA Topical Meeting on Integrated Optics, which was held 21–24 January 1974 in New Orleans, La
The Impact of Physical Activity on Non-Motor Symptoms in Parkinson’s Disease: A Systematic Review
Dielectric multilayer waveguides for TE and TM mode matching
We analyse theoretically for the first time to our knowledge the perfect
phase matching of guided TE and TM modes with a multilayer waveguide composed
of linear isotropic dielectric materials. Alongside strict investigation into
dispersion relations for multilayer systems, we give an explicit qualitative
explanation for the phenomenon of mode matching on the basis of the standard
one-dimensional homogenization technique, and discuss the minimum number of
layers and the refractive index profile for the proposed device scheme. Direct
applications of the scheme include polarization-insensitive, intermodal
dispersion-free planar propagation, efficient fibre-to-planar waveguide
coupling and, potentially, mode filtering. As a self-sufficient result, we
present compact analytical expressions for the mode dispersion in a finite,
N-period, three-layer dielectric superlattice.Comment: 13 pages with figure
Summary of combustion instability research at Princeton University, 1969
Control and causes of combustion instability in rocket engine
Exploring Millions of 6-State FSSP Solutions: the Formal Notion of Local CA Simulation
In this paper, we come back on the notion of local simulation allowing to
transform a cellular automaton into a closely related one with different local
encoding of information. This notion is used to explore solutions of the Firing
Squad Synchronization Problem that are minimal both in time (2n -- 2 for n
cells) and, up to current knowledge, also in states (6 states). While only one
such solution was proposed by Mazoyer since 1987, 718 new solutions have been
generated by Clergue, Verel and Formenti in 2018 with a cluster of machines. We
show here that, starting from existing solutions, it is possible to generate
millions of such solutions using local simulations using a single common
personal computer
Inferring periodic orbits from spectra of simple shaped micro-lasers
Dielectric micro-cavities are widely used as laser resonators and
characterizations of their spectra are of interest for various applications. We
experimentally investigate micro-lasers of simple shapes (Fabry-Perot, square,
pentagon, and disk). Their lasing spectra consist mainly of almost equidistant
peaks and the distance between peaks reveals the length of a quantized periodic
orbit. To measure this length with a good precision, it is necessary to take
into account different sources of refractive index dispersion. Our experimental
and numerical results agree with the superscar model describing the formation
of long-lived states in polygonal cavities. The limitations of the
two-dimensional approximation are briefly discussed in connection with
micro-disks.Comment: 13 pages, 19 figures, accepted for publication in Physical Review
Acute infection of chinese macaques by a CCR5-tropic SHIV carrying a primary HIV-1 subtype B' envelope
The increasing prevalence of HIV-1 subtype B' in China and Southeast Asia calls for efforts to develop a relevant animal model to study viral transmission and pathogenesis. Because there are significant differences between subtype B' HIV-1 and other chimeric simian/human immunodeficiency viru (SHIVs) in the env gene, a novel SHIV, designated SHIV B'WHU, was generated by replacing counterparts of SHIVSF33 with tat/rev/vpu/env genes derived from a primary, CCR5-tropic, subtype B' HIV-1 strain of a Chinese patient. SHIV B'WHU was able to replicate in rhesus peripheral blood mononuclear cells and used CCR5 as its major coreceptor. Moreover, after serial passages in Chinese macaques, the in vivo infectivity of SHIV B' WHU was enhanced, yet no significant sequence changes were found in viral envelopes, and the virus did not change its CCR5-tropism. CD4 T-cell loss, however, was found in the intraepithelial lymphocytes of small intestines of infected macaques. Our findings have implications in understanding the early pathogenesis of SHIV B' WHU in Chinese macaques. Copyright © 2010 by Lippincott Williams & Wilkins.postprin
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