Über die Einzigkeit der Ternionenalgebra und linksalternative Algebren kleinen Ranges

Ohne Zusammenfassung     

Atomistic view of the autosurfactant effect during GaN epitaxy

The Ga-N site exchange critical to the autosurfactant effect during GaN epitaxy is studied. On the GaN(0001) pseudo (1x1), the first site exchange results in N incorporation at the subsurface T1 site, forming ghost islands. The second exchange that converts these islands to that of bilayer height can be triggered by continued scanning tunneling microscopy imaging, which involves electrons tunneling to or from localized states associated with the second layer Ga. The resulting electrostatic force sets off a chain reaction which frees these Ga atoms, allowing N to form covalent Ga-N-Ga bonds of a new GaN bilayer.     

Mathematical modelling of the SSD-process

In order to achieve a better agreement between the calculated and experimental results of crystal production by the SSD-process, it was essential to extend the application of the modell presented earlier (Weinert et al.). The thermal and geometrical conditions, which vary strongly during the course of the process and influence the GaP crystallisation, have never been taken into consideration. It has been attempted, in the present work, to consider these changes by dividing the total time of crystallisation into so small durations (Δt), that the evaluation model presented earlier for instant times can be successfully applied. The results of crystallisation for the total period can then be obtained through a mathematical analysis named as sequence correction of process parameters. It has been shown that an exact knowledge of the temperature distribution in the furnace will yield results which are in very good agreement with the experimental values. Moreover, the changes in the process parameters during the whole time of crystallisation have been represented graphically. — Application of this model to other systems, for example to GaAs, is also possible.     

Synthesis of distibiranes and azadistibiranes by cycloaddition reactions of distibenes with diazomethanes and azides

Cycloaddition reactions of distibene [L(Me₂N)GaSb]₂ (L = HC[C(Me)NDipp]₂; Dipp = 2,6-i-Pr₂C₆H₃) with a series of organoazides RN₃ (R = Ph, p-CF₃Ph, 1-adamantyl (ada)) yielded azadistibiranes [L(Me₂N)GaSb]₂NR (R = Ph 1, p-CF₃Ph 2, ada 3), whereas Me₃SiN₃ reacted with insertion into one Ga–Sb bond and formation of L(Me₂N)GaSbSb(NSiMe₃)Ga(NMe₂)L (4). Analogous compounds 5 and 6 formed after heating of 1 and 2 above 60 °C. Prolonged heating of 5 resulted in a [2 + 2] cycloaddition accompanied by elimination of LGa(NMe₂)₂ and formation of tetrastibacyclobutane 7, while the reaction of 5 with a second equivalent of PhN₃ gave heteroleptic azadistibirane 9, which isomerized at elevated temperature to distibene 10. Cycloaddition also occurred in reactions of [L(X)GaSb]₂ (X = NMe₂, OEt, Cl) with Me₃Si(H)CN₂, yielding distibiranes [L(X)GaSb]₂C(H)SiMe₃ (X = NMe₂11, OEt 12, Cl 13). Compounds 1–13 were characterized by IR, UV-Vis and NMR spectroscopy and sc-XRD. The mechanism of the reaction of [L(Me₂N)GaSb]₂ with PhN₃ and Me₃SiN₃ and the electronic nature of the resulting compounds were studied by DFT calculations.

Azadistibiranes and distibiranes formed in cycloaddition reactions of distibene [L(Me₂N)GaSb]₂ with RN₃ and Me₃Si(H)CN₂. The mechanism of the reactions with PhN₃ and Me₃SiN₃ and the electronic nature of the products were studied by DFT calculations.     

Charmonium decay widths in magnetized matter

The European Physical Journal A - In this paper, we investigated the spectroscopy of heavy tetraquarks through a relativistic diquark-antidiquark model. To this aim, the two-bosonic Klein-Gordon...     

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.     

Structural, spectral, and electrochemical investigations of para-tolyl-substituted oligogermanes

The synthesis of four new oligogermanes containing para-tolyl-substituents has been achieved via the hydrogermolysis reaction, including the digermane Tol₃GeGePh₃, the trigermanes Tol₃GeGePh₂GeTol₃ and Tol₃GeGeTol₂GeTol₃, and the tetragermane Tol₃GeGePh₂GePh₂GeTol₃ (Tol = p-CH₃C₆H₄). These four oligogermanes have been structurally characterized and their structures have been compared with those of their per-phenyl-substituted analogs. The digermane Tol₃GeGePh₃ exhibits an unusually short Ge-Ge bond distance of 2.408(1) Å. The four para-tolyl-substituted oligogermanes have also been characterized by UV/visible spectroscopy and cyclic voltammetry. The expected red shift in the absorbance maximum with increasing catenation was observed for this series of compounds. Their cyclic voltammograms each contain n − 1 irreversible oxidation waves (n = the number of Ge atoms), which is atypical since oligogermanes generally exhibit only one irreversible oxidation wave regardless of the degree of catenation.