1,380 research outputs found
Needs assessment traceability for aquaculture shrimp and workshop in Java Timur, Indonesia, 14-18 June, 2010 Java Timnur Indonesia
The procurement and evaluation of a prototype laser satellite-tracking system Final report, 1 Jan. 1967 - 30 Sep. 1968
Pulsed ruby laser satellite tracking syste
Photographic measurements of the energy distribution in the beam of a ruby laser
Photographic measurement of energy distribution in beam of Q-switched ruby lase
Measurements of satellite range with a ruby laser
Range measurements of GEOS-I and BE-C satellites with ruby lase
The Chromium Impurity in ZnTe: Changes of the Charge State Detected by Optical and EPR Spectroscopy
In gasphase-grown p-type ZnTe crystals, the substitutional Cr impurity is detected in the neutral (Cr2+) and both ionized states Cr3+ and Cr+. While these three oxidation states are now identified by EPR, two of them emerge in the optical spectra as well. Optical irradiation of the samples at low temperatures influences the relative concentrations of these species. By monitoring the respective EPR or optical signals, thresholds for photoionization and photo-neutralization processes are derived. In addition to the strong 5E(D)â5T2(D) optical absorption of Cr2+(d4), the samples display a luminescence band near 4500 cm-1, structured by JahnâTeller interaction. For the first time, a no-phonon line at 4989 cm-1 is resolved, accompanied by a TA(L) satellite and some local-mode structure. In EPR, the angular dependence of the âM = ±2 transition characteristic for Cr2+(d4) ions on lattice sites indicates the 5E(D) ground state subject to a static Jahn-Teller effect in the three (100) directions. Whereas an internal optical transition of Cr3+(d3) could not be identified, in EPR, an isotropie signal at g=3.3 discloses a strongly JahnâTeller-disturbed 4T1(F) ground state. On irradiation with band-tail photons, the ionized acceptor state Cr+(d5) becomes detectable by EPR. Furthermore, an emission with an onset near 10,300 cm-1 is recorded for the first time. Its excitation and optical stimulation spectra are studied in wide spectral ranges; the exponential decay with ζâ
1 ms supports an assignment to a spin-forbidden transition. The acceptor ionization energy is determined as 10,500 cm-1 (1.3 eV)
Delocalizing effect of the Hubbard repulsion for electrons on a two-dimensional disordered lattice
We study numerically the ground-state properties of the repulsive Hubbard
model for spin-1/2 electrons on two-dimensional lattices with disordered
on-site energies. The projector quantum Monte Carlo method is used to obtain
very accurate values of the ground-state charge density distributions with
and particles. The difference in these charge densities allows us
to study the localization properties of an added particle. The results obtained
at quarter-filling on finite clusters show that the Hubbard repulsion has a
strong delocalizing effect on the electrons in disordered 2D lattices. However,
numerical restrictions do not allow us to reach a definite conclusion about the
existence of a metal-insulator transition in the thermodynamic limit in
two-dimensions.Comment: revtex, 7 pages, 7 figure
National Geodetic Satellite Program, Part II: Smithsonian Astrophysical Observatory
A sequence of advances in the determination of geodetic parameters presented by the Smithsonian Astrophysical Observatory are described. A Baker-Nunn photographic system was used in addition to a ruby-laser ranging system to obtain data for refinement of geodetic parameters. A summary of the data employed to: (1) derive coordinates for the locations of various tracking stations; and (2) determine the gravitational potential of the earth, is presented
Long-term outcome prediction by clinicopathological risk classification algorithms in node-negative breast cancerâcomparison between Adjuvant!, St Gallen, and a novel risk algorithm used in the prospective randomized Node-Negative-Breast Cancer-3 (NNBC-3) trial
Background: Defining risk categories in breast cancer is of considerable clinical significance. We have developed a novel risk classification algorithm and compared its prognostic utility to the Web-based tool Adjuvant! and to the St Gallen risk classification. Patients and methods: After a median follow-up of 10 years, we retrospectively analyzed 410 consecutive node-negative breast cancer patients who had not received adjuvant systemic therapy. High risk was defined by any of the following criteria: (i) age 2 cm. All patients were also characterized using Adjuvant! and the St Gallen 2007 risk categories. We analyzed disease-free survival (DFS) and overall survival (OS). Results: The Node-Negative-Breast Cancer-3 (NNBC-3) algorithm enlarged the low-risk group to 37% as compared with Adjuvant! (17%) and St Gallen (18%), respectively. In multivariate analysis, both Adjuvant! [Pâ=â0.027, hazard ratio (HR) 3.81, 96% confidence interval (CI) 1.16-12.47] and the NNBC-3 risk classification (Pâ=â0.049, HR 1.95, 95% CI 1.00-3.81) significantly predicted OS, but only the NNBC-3 algorithm retained its prognostic significance in multivariate analysis for DFS (P < 0.0005). Conclusion: The novel NNBC-3 risk algorithm is the only clinicopathological risk classification algorithm significantly predicting DFS as well as O
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