29,240 research outputs found
Pressure-control purge panel for automatic butt welding
Modification of a purge panel for use in an automatic butt weld reduces the drop in pressure between the regulators and the weld head and tube purge fitting. The invention affects air regulators for plants, regulating circuits for pneumatic valves, and automatic welding machines
Wage and salary inequality in U.S. manufacturing, 1973-1981: The effects of economic restructuring
Circular 109
Introduction -- Explanation of Plant Evaluation Tables -- Table 1. Weather records for the test years -- Table 2. All plant materials evaluated in 1996 -- Table 3. All plants that have been evaluated but did not survive the minimum number of test years -- Table 4. Plantings from 1996 that have not yet been evaluated for winter survival -- Table 5. Annual flowers evaluated in 1996 -- Appendix 1. Commercial Sources and Organizations -- Map of GB
ELECTRON-DEFICIENT PENTAMETHYLCYCLOPENTADIENYL-1,3-BUTADIENE COMPLEXES OF TITANIUM, ZIRCONIUM, AND HAFNIUM
The Effect of Recombination on the Neutral Evolution of Genetic Robustness
Conventional population genetics considers the evolution of a limited number
of genotypes corresponding to phenotypes with different fitness. As model
phenotypes, in particular RNA secondary structure, have become computationally
tractable, however, it has become apparent that the context dependent effect of
mutations and the many-to-one nature inherent in these genotype-phenotype maps
can have fundamental evolutionary consequences. It has previously been
demonstrated that populations of genotypes evolving on the neutral networks
corresponding to all genotypes with the same secondary structure only through
neutral mutations can evolve mutational robustness [Nimwegen {\it et al.}
Neutral evolution of mutational robustness, 1999 PNAS], by concentrating the
population on regions of high neutrality. Introducing recombination we
demonstrate, through numerically calculating the stationary distribution of an
infinite population on ensembles of random neutral networks that mutational
robustness is significantly enhanced and further that the magnitude of this
enhancement is sensitive to details of the neutral network topology. Through
the simulation of finite populations of genotypes evolving on random neutral
networks and a scaled down microRNA neutral network, we show that even in
finite populations recombination will still act to focus the population on
regions of locally high neutrality.Comment: Accepted for publication in Math. Biosci. as part of the proceedings
of BIOCOMP 200
A Mean-Field Theory for Coarsening Faceted Surfaces
A mean-field theory is developed for the scale-invariant length distributions
observed during the coarsening of one-dimensional faceted surfaces. This theory
closely follows the Lifshitz-Slyozov-Wagner theory of Ostwald ripening in
two-phase systems [1-3], but the mechanism of coarsening in faceted surfaces
requires the addition of convolution terms recalling the work of Smoluchowski
[4] and Schumann [5] on coalescence. The model is solved by the exponential
distribution, but agreement with experiment is limited by the assumption that
neighboring facet lengths are uncorrelated. However, the method concisely
describes the essential processes operating in the scaling state, illuminates a
clear path for future refinement, and offers a framework for the investigation
of faceted surfaces evolving under arbitrary dynamics.
[1] I. Lifshitz, V. Slezov, Soviet Physics JETP 38 (1959) 331-339.
[2] I. Lifshitz, V. Slyozov, J. Phys. Chem. Solids 19 (1961) 35-50.
[3] C. Wagner, Elektrochemie 65 (1961) 581-591.
[4] M. von Smoluchowski, Physikalische Zeitschrift 17 (1916) 557-571.
[5] T. Schumann, J. Roy. Met. Soc. 66 (1940) 195-207
Tuning the Charge Density Wave and Superconductivity in CuxTaS2
We report the characterization of layered, 2H-type CuxTaS2, for x between 0
and 0.12. The charge density wave (CDW), at 70 K for TaS2, is destabilized with
Cu doping. The sub-1K superconducting transition in undoped 2H-TaS2 jumps
quickly to 2.5 K at low x, increases to 4.5 K at the optimal composition
Cu0.04TaS2, and then decreases at higher x. The electronic contribution to the
specific heat, first increasing and then decreasing as a function of Cu
content, is 12 mJ mol-1 K-2 at Cu0.04TaS2. Electron diffraction studies show
that the CDW remains present at the optimal superconducting composition, but
with both a changed q vector and decreased coherence length. We present an
electronic phase diagram for the system.Comment: 7 pages, 9 figures. To be published in Physical Review
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