39,941 research outputs found
Results from the arable crop rotation study at Oak Park 2000 - 2007
An organic rotation trial was established at Oak Park in 2000. The crop sequence in the seven year rotation was: two years grass-clover, winter wheat, potatoes, winter oats, lupins and spring barley. The grass-clover, which supplies nitrogen to the system, also provides vegetation which of late is cut and mixed with cereal straw to produce compost. The compost replaced sheep manure which was available up to 2007. Manure was applied to potato plots prior to cultivation for the period 2002 to 2007 and to barley plots from 2005 to 2007. The average yield of crops over the period of the rotation was: winter wheat 5.9 t/ha, potatoes 32.7 t/ha, winter oats 5.8 t/ha, lupins 2.4 t/ha and spring barley 4.5 t/ha. Triticale, which was grown in one of the plots designated for winter wheat, had an average yield of 7.5 t/ha. Lupins have been unsatisfactory due to uncompetitiveness with weeds and lateness of maturity
Oscillations of atomic fermions in a one dimensional optical lattice
A semiclassical model is used to investigate oscillations of atomic fermions
in a combined magnetic trap and one dimensional optical lattice potential
following axial displacement of the trap. The oscillations are shown to have a
characteristic small amplitude, damped behavior in the collisionless regime.
The presence of a separatrix in the semiclassical Brillouin zone phase space is
predicted and shown to produce a strongly asymmetric phase space distribution
function.Comment: 6 pages, 6 figure
The Length of an SLE - Monte Carlo Studies
The scaling limits of a variety of critical two-dimensional lattice models
are equal to the Schramm-Loewner evolution (SLE) for a suitable value of the
parameter kappa. These lattice models have a natural parametrization of their
random curves given by the length of the curve. This parametrization (with
suitable scaling) should provide a natural parametrization for the curves in
the scaling limit. We conjecture that this parametrization is also given by a
type of fractal variation along the curve, and present Monte Carlo simulations
to support this conjecture. Then we show by simulations that if this fractal
variation is used to parametrize the SLE, then the parametrized curves have the
same distribution as the curves in the scaling limit of the lattice models with
their natural parametrization.Comment: 18 pages, 10 figures. Version 2 replaced the use of "nu" for the
"growth exponent" by 1/d_H, where d_H is the Hausdorff dimension. Various
minor errors were also correcte
New continua for absorption spectroscopy from 40 to 2000 Å
The spectra of plasmas produced by focusing the output of a Q-switched ruby laser (output 1 J) on the rare-earth metals have been studied. From samarium (Z = 70), strong quasi-uniform continua are emitted in the wavelength range 40–2000 Å. Line emission from the target elements is absent over most of this wavelength region, particularly below about 600 Å. The use of these continua as simple, reliable background sources for absorption spectroscopy in the vacuum-ultraviolet and soft x-ray region down to 40 Å is demonstrated
Effect of a Spin-1/2 Impurity on the Spin-1 Antiferromagnetic Heisenberg Chain
Low-lying excited states as well as the ground state of the spin-1 antiferro-
magnetic Heisenberg chain with a spin-1/2 impurity are investigated by means of
a variational method and a method of numerical diagonalization. It is shown
that 1) the impurity spin brings about massive modes in the Haldane gap, 2)
when the the impurity-host coupling is sufficiently weak, the phenomenological
Hamiltonian used by Hagiwara {\it et al.} in the analysis of ESR experimental
results for NENP containing a small amount of spin-1/2 Cu impurities is
equivalent to a more realistic Hamiltonian, as far as the energies of the
low-lying states are concerned, 3) the results obtained by the variational
method are in semi-quantitatively good agreement with those obtained by the
numerical diagonalization.Comment: 11 pages, plain TeX (Postscript figures are included), KU-CCS-93-00
Transforming fixed-length self-avoiding walks into radial SLE_8/3
We conjecture a relationship between the scaling limit of the fixed-length
ensemble of self-avoiding walks in the upper half plane and radial SLE with
kappa=8/3 in this half plane from 0 to i. The relationship is that if we take a
curve from the fixed-length scaling limit of the SAW, weight it by a suitable
power of the distance to the endpoint of the curve and then apply the conformal
map of the half plane that takes the endpoint to i, then we get the same
probability measure on curves as radial SLE. In addition to a non-rigorous
derivation of this conjecture, we support it with Monte Carlo simulations of
the SAW. Using the conjectured relationship between the SAW and radial SLE, our
simulations give estimates for both the interior and boundary scaling
exponents. The values we obtain are within a few hundredths of a percent of the
conjectured values
Report on the development of the Manned Orbital Research Laboratory /MORL/ system utilization potential. Task area IV - MORL SYSTEM improvement study, book 2
Environmental control and life support systems analyses for improved Manned Orbital Research Laborator
Analytic Relations between Localizable Entanglement and String Correlations in Spin Systems
We study the relation between the recently defined localizable entanglement
and generalized correlations in quantum spin systems. Differently from the
current belief, the localizable entanglement is always given by the average of
a generalized string. Using symmetry arguments we show that in most spin 1/2
and spin 1 systems the localizable entanglement reduces to the spin-spin or
string correlations, respectively. We prove that a general class of spin 1
systems, which includes the Heisenberg model, can be used as perfect quantum
channel. These conclusions are obtained in analytic form and confirm some
results found previously on numerical grounds.Comment: 5 pages, RevTeX
Energy Versus Magnetic-Field Diagram of the Spin-1 Haldane System with an Impurity
Energy versus magnetic-field diagram of the spin- Haldane system with an
impurity bond is studied in terms of spin-1/2 degree of freedom at the sites
neighboring the impurity bond by means of analytical method. We examine the
equivalence between the realistic Hamiltonian and the phenomenological
Hamiltonian which is composed two spin-1/2 spins representing the spin-1/2
degree of freedom. It is proved that when the strength of the impurity bond is
sufficiently weak, the two Hamiltonians are equivalent to each other, as far as
the energies of the low-lying states are concerned. We determine the
correspondence between the interaction constants in the phenomenological
Hamiltonian and those in the realistic Hamiltonian.Comment: 10 pages, plain TeX (Postscript figures are included), KU-CCS-93-00
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