1,128 research outputs found
USE OF NEUTRON IRRADIATIONS IN THE BROOKHAVEN MUTATIONS PROGRAM
Many plant species were irradiated with x rays, thermal and fast neutrons, andd gamma radiation during the past 10 yr of the cooperative mutations program and adjunct mutation breeding program. Four major concepts and/ or approaches related to the use of mutagenic agents in plant breeding that have evolved are discussed. It was concluded that outcrossing between treated and nontreated populations must be reckoned with, and consequently the two populations should be separated before a true measure of mutation induction can be ascertained; chromosome rearrangement studies are useful, with particular emphasis on inducing disease resistance; work concerned with tissue reorgandization and rearrangement as related to chimera production and basic understanding of tissue ontogeny, particularly with fruit crops andd horticultural crops is promising; and the effectiveness of responses of plant tissues to neutrons and other mutagenic agents is extremely variable and more basic work is needed before the full potentialities of mutation breeding as a tool in crop improvement can be appreciated. (auth
Low autocorrelated multi-phase sequences
The interplay between the ground state energy of the generalized Bernasconi
model to multi-phase, and the minimal value of the maximal autocorrelation
function, , , is examined analytically and
the main results are: (a) The minimal value of is
significantly smaller than the typical value for random
sequences . (b) over all sequences
of length N is obtained in an energy which is about 30% above the ground-state
energy of the generalized Bernasconi model, independent of the number of phases
m. (c) The maximal merit factor grows linearly with m. (d) For a
given N, indicating that for m=N,
, i.e. a Barker code exits. The analytical results are
confirmed by simulations.Comment: 4 pages, 4 figure
The Future Evolution of White Dwarf Stars Through Baryon Decay and Time Varying Gravitational Constant
Motivated by the possibility that the fundamental ``constants'' of nature
could vary with time, this paper considers the long term evolution of white
dwarf stars under the combined action of proton decay and variations in the
gravitational constant. White dwarfs are thus used as a theoretical laboratory
to study the effects of possible time variations, especially their implications
for the future history of the universe. More specifically, we consider the
gravitational constant to vary according to the parametric relation , where the time scale is the same order as
the proton lifetime. We then study the long term fate and evolution of white
dwarf stars. This treatment begins when proton decay dominates the stellar
luminosity, and ends when the star becomes optically thin to its internal
radiation.Comment: 12 pages, 10 figures, accepted to Astrophysics and Space Scienc
Kohn Anomalies in Superconductors
I present the detailed behavior of phonon dispersion curves near momenta
which span the electronic Fermi sea in a superconductor. I demonstrate that an
anomaly, similar to the metallic Kohn anomaly, exists in a superconductor's
dispersion curves when the frequency of the phonon spanning the Fermi sea
exceeds twice the superconducting energy gap. This anomaly occurs at
approximately the same momentum but is {\it stronger} than the normal-state
Kohn anomaly. It also survives at finite temperature, unlike the metallic
anomaly. Determination of Fermi surface diameters from the location of these
anomalies, therefore, may be more successful in the superconducting phase than
in the normal state. However, the superconductor's anomaly fades rapidly with
increased phonon frequency and becomes unobservable when the phonon frequency
greatly exceeds the gap. This constraint makes these anomalies useful only in
high-temperature superconductors such as .Comment: 18 pages (revtex) + 11 figures (upon request), NSF-ITP-93-7
Interaction-Induced Magnetization of the Two-Dimensional Electron Gas
We consider the contribution of electron-electron interactions to the orbital
magnetization of a two-dimensional electron gas, focusing on the ballistic
limit in the regime of negligible Landau-level spacing. This regime can be
described by combining diagrammatic perturbation theory with semiclassical
techniques. At sufficiently low temperatures, the interaction-induced
magnetization overwhelms the Landau and Pauli contributions. Curiously, the
interaction-induced magnetization is third-order in the (renormalized) Coulomb
interaction. We give a simple interpretation of this effect in terms of
classical paths using a renormalization argument: a polygon must have at least
three sides in order to enclose area. To leading order in the renormalized
interaction, the renormalization argument gives exactly the same result as the
full treatment.Comment: 11 pages including 4 ps figures; uses revtex and epsf.st
Activation of the heat shock transcription factor Hsf1 is essential for the full virulence of the fungal pathogen Candida albicans
Peer reviewedPublisher PD
Entanglement between Demand and Supply in Markets with Bandwagon Goods
Whenever customers' choices (e.g. to buy or not a given good) depend on
others choices (cases coined 'positive externalities' or 'bandwagon effect' in
the economic literature), the demand may be multiply valued: for a same posted
price, there is either a small number of buyers, or a large one -- in which
case one says that the customers coordinate. This leads to a dilemma for the
seller: should he sell at a high price, targeting a small number of buyers, or
at low price targeting a large number of buyers? In this paper we show that the
interaction between demand and supply is even more complex than expected,
leading to what we call the curse of coordination: the pricing strategy for the
seller which aimed at maximizing his profit corresponds to posting a price
which, not only assumes that the customers will coordinate, but also lies very
near the critical price value at which such high demand no more exists. This is
obtained by the detailed mathematical analysis of a particular model formally
related to the Random Field Ising Model and to a model introduced in social
sciences by T C Schelling in the 70's.Comment: Updated version, accepted for publication, Journal of Statistical
Physics, online Dec 201
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