2,808 research outputs found
Systematic description and key to isolants from Atacama Desert, Chile
Isolation and identification of desert soil microorganism from Chil
Development of boron calibration via hybrid comparator method in prompt gamma activation analysis
The prompt gamma activation analysis (PGAA) facility at the Nuclear Engineering Teaching Laboratory at The University of Texas at Austin was utilized to quantify boron concentrations in boron carbide semiconductor films deposited on silicon substrates. Calibration was complicated by the unique and varying sample geometries analyzed. In addition, there was a dearth of solid materials available with quantified boron concentrations having comparable or readily modifiable dimensions to exploit for calibration purposes. Therefore, a novel hybrid comparator method was developed for the quantification of boron utilizing aluminum as an inexpensive and easily machinable reference material. Aluminum samples were manufactured with high tolerances to match the geometry of each sample of interest. Each boron carbide film sample and its congruent aluminum sample were measured in the PGAA system. The measured aluminum responses and relevant nuclear parameters were used to standardize the measurements. A boron standard was created using a procedure derived from a similar approach used by the National Institute of Standards and Technology. Quality control measurements using this standard show that the method provided accuracy to within 5% for boron quantification
Corn Silage Diets for Finishing Cattle When Supplemented With Soybean Meal or Urea and DES Fed at 10 mg., 20 mg. Daily or Implanted
Corn silage properly supplemented with protein, minerals and vitamin A forms a simple and efficient diet for growing and finishing cattle. Rate of gain will be less than for high-concentrate diets, especially during late stages of finishing. However, gain per acre of corn will be greater when fed as silage than as grain
Systematic description and key to isolants from Little Lake volcanic area, California Progress report
Descriptive charts on bacteria isolated from soils of Little Lake volcanic area in Californi
Evidence for a superfluid density in t--J ladders
Applying three independent techniques, we give numerical evidence for a
finite superfluid density in isotropic hole-doped t--J ladders: We show the
existence of anomalous flux quantization, emphasising the contrasting behaviour
to that found in the `Luttinger liquid' regime stabilised at low electron
densities; We consider the nature of the low-lying excitation modes, finding
the 1-D analog of the superconducting state; And using a density matrix
renormalization group approach, we find long range pairing correlations and
exponentially decaying spin-spin correlations.Comment: 4 pages, revtex, postscript figs included, submitted to PR
Quantum Transition between an Antiferromagnetic Mott Insulator and Superconductor in Two Dimensions
We consider a Hubbard model on a square lattice with an additional
interaction, , which depends upon the square of a near-neighbor hopping. At
half-filling and a constant value of the Hubbard repulsion, increasing the
strength of the interaction drives the system from an antiferromagnetic
Mott insulator to a superconductor. This conclusion is reached
on the basis of zero temperature quantum Monte Carlo simulations on lattice
sizes up to .Comment: 4 pages (latex) and 4 postscript figure
Local Electronic Structure of a Single Magnetic Impurity in a Superconductor
The electronic structure near a single classical magnetic impurity in a
superconductor is determined using a fully self-consistent Koster-Slater
algorithm. Localized excited states are found within the energy gap which are
half electron and half hole. Within a jellium model we find the new result that
the spatial structure of the positive-frequency (electron-like) spectral weight
(or local density of states), can differ strongly from that of the negative
frequency (hole-like) spectral weight. The effect of the impurity on the
continuum states above the energy gap is calculated with good spectral
resolution for the first time. This is also the first three-dimensional
self-consistent calculation for a strong magnetic impurity potential.Comment: 13 pages, RevTex, change in heuristic picture, no change in numerical
result
The interplay between electron-electron interactions and impurities in one-dimensional rings
The persistent current and charge stiffness of a one-dimensional Luttinger
liquid on a ring threaded by a magnetic flux are calculated by Monte Carlo
simulation. By changing the random impurity potential strength and the
electron-electron interaction, we see a crossover behavior between weak and
strong impurity limits. For weak impurity potentials, interactions enhance
impurity effects, that is, interactions decrease the current and the stiffness.
On the other hand, interactions tend to screen impurities when the impurity
potential is strong. Temperature dependence of the persistent current and the
charge stiffness shows a peak at a characteristic temperature, consistent with
a recent single impurity study.Comment: 4 pages (ReVTeX3.0) + 3 figures (in uuencoded postscript format)
appended in the end of the fil
Re-parameterization Invariance in Fractional Flux Periodicity
We analyze a common feature of a nontrivial fractional flux periodicity in
two-dimensional systems. We demonstrate that an addition of fractional flux can
be absorbed into re-parameterization of quantum numbers. For an exact
fractional periodicity, all the electronic states undergo the
re-parameterization, whereas for an approximate periodicity valid in a large
system, only the states near the Fermi level are involved in the
re-parameterization.Comment: 4 pages, 1 figure, minor changes, final version to appear in J. Phys.
Soc. Jp
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