447 research outputs found
Response of Spring Barley (Hordeum vulgare) to Herbicides
‘Karla’, ‘Klages\u27, ‘Morex’, and ‘Steptoe’ cultivars of spring barley (Hordeum vulgare L.) differed in susceptibility to postemergence recommended application rates of diclofop {(±)-2-[4-(2,4-dichlorophenoxy) phenoxy] propanoic acid}, difenzoquat [1,2-dimethyl-3,5-diphenyl-1H-pyrazolium], chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonamide}, and metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] in 1981 and 1982. Metribuzin injured Morex, and difenzoquat injured all cultivars within 2 weeks after herbicide application. Metribuzin reduced height and crop biomass compared to the hand-weeded control. Herbicide treatments did not affect grain yield at Moscow, ID, in either year. However, metribuzin reduced yield of Karla and Morex, and diclofop reduced yield of Karla compared to the hand-weeded control at Pullman, WA, in 1982. Barley injury and grain yield loss depended on herbicide treatment and cultivar. Early season herbicide injury to barley did not indicate grain yield response at harvest
Verbundvorhaben: SIPAS - Methoden zur Ermittlung und Einhaltung eines sicheren Passierabstandes von Schiffen beim Ãœberholen und Begegnen im begrenzten Fahrwasser, Teilvorhaben SIPAS-MAP: Modellierung, Analyse und Parametrisierung hydrodynamischer Wirkungen und Kollisionsursachen beim Passieren von Seeschiffen
Numerical Study of Order in a Gauge Glass Model
The XY model with quenched random phase shifts is studied by a T=0 finite
size defect energy scaling method in 2d and 3d. The defect energy is defined by
a change in the boundary conditions from those compatible with the true ground
state configuration for a given realization of disorder. A numerical technique,
which is exact in principle, is used to evaluate this energy and to estimate
the stiffness exponent . This method gives in
2d and in 3d, which are considerably larger than
previous estimates, strongly suggesting that the lower critical dimension is
less than three. Some arguments in favor of these new estimates are given.Comment: 4 pages, 2 figures, revtex. Submitted to Phys. Rev. Let
Verbundvorhaben SKATE. Schiffs-Konzepte für die Anwendung innovativer Techniken zur Energieeinsparung. Teilvorhaben VALIDATE SKATE : Versuchsdurchführung, Analyse, Extrapolation und Designerrichtlinien ableiten
Quantum Spin Glasses
Ising spin glasses in a transverse field exhibit a zero temperature quantum
phase transition, which is driven by quantum rather than thermal fluctuations.
They constitute a universality class that is significantly different from the
classical, thermal phase transitions. Most interestingly close to the
transition in finite dimensions a quantum Griffiths phase leads to drastic
consequences for various physical quantities: for instance diverging magnetic
susceptibilities are observable over a whole range of transverse field values
in the disordered phase.Comment: 10 pages LaTeX (Springer Lecture Notes style file included), 1
eps-figure; Review article for XIV Sitges Conference: Complex Behavior of
Glassy System
Non-Fermi liquid behavior and Griffiths phase in {\it f}-electron compounds
We study the interplay among disorder, RKKY and Kondo interactions in {\it
f}-electron alloys. We argue that the non-Fermi liquid behavior observed in
these systems is due to the existence of a Griffiths phase close to a quantum
critical point. The existence of this phase provides a unified picture of a
large class of materials. We also propose new experiments that can test these
ideas.Comment: 4 pages, 1 Figure. NEW version of the original manuscript. A single
framework for NFL behavior in different kinds of alloys is presented. Final
version finally allowed to appear on the glorious Physical Review Letter
The metastate approach to thermodynamic chaos
In realistic disordered systems, such as the Edwards-Anderson (EA) spin
glass, no order parameter, such as the Parisi overlap distribution, can be both
translation-invariant and non-self-averaging. The standard mean-field picture
of the EA spin glass phase can therefore not be valid in any dimension and at
any temperature. Further analysis shows that, in general, when systems have
many competing (pure) thermodynamic states, a single state which is a mixture
of many of them (as in the standard mean-field picture) contains insufficient
information to reveal the full thermodynamic structure. We propose a different
approach, in which an appropriate thermodynamic description of such a system is
instead based on a metastate, which is an ensemble of (possibly mixed)
thermodynamic states. This approach, modelled on chaotic dynamical systems, is
needed when chaotic size dependence (of finite volume correlations) is present.
Here replicas arise in a natural way, when a metastate is specified by its
(meta)correlations. The metastate approach explains, connects, and unifies such
concepts as replica symmetry breaking, chaotic size dependence and replica
non-independence. Furthermore, it replaces the older idea of non-self-averaging
as dependence on the bulk couplings with the concept of dependence on the state
within the metastate at fixed coupling realization. We use these ideas to
classify possible metastates for the EA model, and discuss two scenarios
introduced by us earlier --- a nonstandard mean-field picture and a picture
intermediate between that and the usual scaling/droplet picture.Comment: LaTeX file, 49 page
Imogolite nanotubes: a 2D x-ray scattering study of films of oriented samples
International audienceInorganic nanotubes represent an emerging class of nanobuilding blocks. Among them, imogolites are alumino-silicate or alumino-germanate nanotubes with well controlled diameter and helicity. As such, they constitute a model platform for the study of molecular interactions and confinement at the nanoscale, complementing the one constituted by carbon nanotubes. We focus here on double-walled alumino-germanate nanotubes, discovered very recently [1]. They are formed of two concentric tubes (figure inset), with respective internal diameters of 1.6 and 3.1nm and up to 1 micron in length [2]. We report the first experimental study, using wide angle x-ray scattering, performed on films of oriented nanotubes (figure). Structural changes of the nanotubes and behavior of the confined water under heating are investigated in-situ. The study of oriented samples gives new information that is not available with powder diffraction. Above all, the contribution to the scattering signal of internal and external tubes can be separated as well as the translational/rotational correlations. The use of wide image plate detectors allows one to access large area of the reciprocal space in a single image. Simulations of the two-dimensionnal scattering diagrams will be presented. A key question, the correlation between internal and external tube, which is of great interest for understanding friction properties at the nanoscale, will be discussed
Critical Behavior and Griffiths-McCoy Singularities in the Two-Dimensional Random Quantum Ising Ferromagnet
We study the quantum phase transition in the two-dimensional random Ising
model in a transverse field by Monte Carlo simulations. We find results similar
to those known analytically in one-dimension. At the critical point, the
dynamical exponent is infinite and the typical correlation function decays with
a stretched exponential dependence on distance. Away from the critical point
there are Griffiths-McCoy singularities, characterized by a single,
continuously varying exponent, z', which diverges at the critical point, as in
one-dimension. Consequently, the zero temperature susceptibility diverges for a
RANGE of parameters about the transition.Comment: 4 pages RevTeX, 3 eps-figures include
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