Ein Struktursatz für idempotente Halbkörper

Ohne ZusammenfassungVorgelegt vonL. Rédei     

Zur Theorie Levitzkischer Radikale in Halbringen

Ohne Zusammenfassung     

Über Halbringe und Halbkörper. II

Ohne Zusammenfassung Vorgelegt von L. Rédei     

Über Halbringe und Halbkörper. III

Ohne Zusammenfassung Vorgelegt von L. Rédei     

Phytosanitary irradiation of fresh tropical commodities in Hawaii: Generic treatments,commercial adoption,and current issues

Hawaii is a pioneer in the use of phytosanitary irradiation. The commercial X-ray irradiation facility, Hawaii Pride LLC, has been shipping papaya and other tropical fruits and vegetables to the United States mainland using irradiation for 11 years. Irradiation is an approved treatment to control quarantine pests in 17 fruits and 7 vegetables for export from Hawaii to the US mainland. Hawaiian purple sweet potato is the highest volume product with annual exports of more than 12 million lbs (5500 t). The advent of generic radiation treatments for tephritid fruit flies (150 Gy) and other insects (400 Gy) will accelerate commodity export approvals and facilitate worldwide adoption. Lowering doses for specific pests and commodities can lower treatment costs and increase capacity owing to shorter treatment times, and will minimize any quality problems. Current impediments to wider adoption include the 1 kGy limit for fresh horticultural products, the labeling requirement, and non-acceptance of phytosanitary irradiation in Japan, the European Union, and elsewhere. Irradiation has potential as a treatment for unregulated imports to prevent new pest incursions.     

Anatomy of relativistic energy corrections in light molecular systems

Relativistic energy corrections which arise from the use of the Dirac-Coulomb Hamiltonian, and the Gaunt and Breit interaction operators, plus Lamb-shift effects have been determined for the global minima of the ground electronic states of C₂H₆, NH₃, H₂O, [H,C,N], HNCO, HCOOH, SiC₂, SiH^? ₃, and H₂S, and for barrier characteristics for these molecular systems (inversion barrier of NH₃ and SiH^? ₃, barrier to linearity of H₂O, H₂S, and HNCO, rotational barrier of C₂H₆, difference between conformations of HCOOH (Z/E) and SiC₂ (linear/T-shaped), and isomerization barrier of HCN/HNC). The relativistic calculations performed at the Hartree-Fock and the highly correlated CCSD(T) levels employed a wide variety of basis sets. Comparison of the perturbational and the four-component fully variational results indicate that the Coulomb-Pauli Hamiltonian and the lowest order Hamiltonian of direct perturbation theory (DPT(2)) are highly successful for treating the relativistic energy effects in light molecular systems both at a single point on the potential energy hypersurface and along the surface. Electron correlation contributions to the relativistic corrections are relatively small for the systems studied, and are comparable with the 2-electron Darwin correction. Corrections beyond the Dirac-Coulomb treatment are usually rather small, but may become important for high accuracy ab initio calculations.     

Gigahertz modulators using bulk acousto-optic interactions in thin-film waveguides

Abstract

When bulk acoustic waves are applied to an optical waveguide, several modulation effects are observed, depending on the type of wave (longitudinal or shear). Longitudinal sound waves frequency-shift the guided light, thus providing a means of modulating light in a wide variety of waveguide materials. Using thin-film mosaic acoustic transducer technology, we have demonstrated such modulation at frequencies in the gigahertz region. By segmenting the acoustic transducer electrodes, the same arrangement can be used for deflecting the light since, with this arrangement, the acoustic field sets up a time-varying grating whose spatial frequency is set by the segment spacing. Theoretical frequency limitations on these devices do not appear to be important until approximately 30 GHz is reached. Thus, they are potentially useful for extremely wide-band data links. Experiments at 1.5 GHz show 30% bandwidth of acoustic modulation using optical heterodyne detection.     

Calculation of hyperfine interaction parameters in metals-friedel oscillations in dilute Fe and Cu alloys

We review some recent calculations on hyperfine interaction parameters in metals based on density functional theory in the local density approximation. We restrict ourselves to the calculation of Friedel oscillations of the charge and magnetization density in dilute Fe and Cu alloys. In particular, we estimate hyperfine fields, isomer shifts and electric field gradients for a few shells around the impurities. The calculations are performed using the KKR-Green's function method. Especially, we discuss which valence properties determine the hyperfine interaction parameters and what information about the electronic structure can be obtained from their measurement.