Reconstruction of the -GaO (1 0 0) cleavage surface to hexagonal GaN after NH nitridation

The potential use of β-Ga₂O₃ wafers as transparent conductive substrates for compounds with hexagonal structure, in particular the GaN-system, is shown. Nitridation of the main cleavage plane under high temperature and NH₃ gas results in the substitution of O by N on the surface, and a simultaneous surface reconstruction. The 2-fold symmetry of the initial (1 0 0) plane changes to a 6-fold symmetry, keeping the [0 1 0] azimuth as a symmetry direction. The RHEED pattern suggests the formation of GaN on the β-Ga₂O₃ surface, with the b-axis of β-Ga₂O₃ parallel to the direction of GaN, so that β-Ga₂O₃ can be used as a substrate with no lattice mismatch to GaN.     

Surface phonons of LaB6(100): deformation of boron octahedra at the surface

The surface phonon dispersion of clean LaB₆(100) surface has been measured by means of high resolution electron energy loss spectroscopy. Eight vibrational modes, of which most are located in the energy gaps between the bulk phonon bands, have been detected. The lattice dynamical calculation of a slab-shaped crystal based on a force constant model has reproduced these experimental dispersion curves, which indicates the large increase in the force constant of interoctahedral boron-boron bond at the surface by 25%, and the large decrease in the force constants of intraoctahedral boron-boron bonds at the surface by 25–50%. These changes together with the analysis of the bulk phonon structure of metal hexaborides strongly suggest that the boron octahedra at the surface are expanded by about 0.004 nm parallel to the surface.     

Characterization of the complex formation of 1,6‐anhydro‐β‐maltotriose with potassium using 1H and 39K NMR spectroscopy

The ¹H and ³⁹K longitudinal relaxation times (T₁) and ¹H diffusion coefficients were measured to investigate the complex formation of 1,6‐anhydro‐β‐maltotriose and potassium ions. Although the ¹H‐T₁ values of H3′, H5′, H1″ and H4″ decreased in the presence of potassium ions, ¹H chemical shifts and ¹H diffusion coefficients did not show significant changes. The long‐range coupling constants of ³J_C?H around the glycosyl bonds did not show significant changes either. In the measurements of ³⁹K spectra, the ³⁹K signal obviously broadened and the ³⁹K‐T₁ values decreased in the presence of 1,6‐anhydro‐β‐maltotriose, indicating the complex formation of 1,6‐anhydro‐β‐maltotriose and potassium ions. These results indicate that the conformation and molecular volume were unaffected in the complex formation. Copyright © 2009 John Wiley & Sons, Ltd.     

Lagrangian formalism for resonant capacitive transducers for gravitational-wave antennas

Summary A general analysis of the characteristics of a resonant transducer for gravitational-wave antennas whose resonator has a general mode of vibration has been made using a Lagrangian formalism. The method has been applied to investigate the characteristics of the resonant capacitive transducer developed at the University of Rome and mounted on the cryogenic gravitational-wave antenna built at CERN, finding results in good agreement with the experimental behaviour.

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Riassunto Si usa il formalismo lagrangiano per svolgere un'analisi delle caratteristiche di un trasduttore risonante per antenne gravitazionali nel caso generale in cui il risuonatore utilizzato abbia un modo di vibrazione di forma qualunque. Il metodo è applicato allo studio delle caratteristiche del trasduttore risonante capacitivo sviluppato alla I Università di Roma e montato sull'antenna gravitazionale criogenica realizzata al CERN, trovando risultati in buon accordo con i valori sperimentali.

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Резюме Используя Лагранжев формализм, проводится обший анализ характеристик резонансного датчика для антенн гравитационных волх. Предложенный метод применяется для исследования характеристик резонансного емкостного датчика, разработанного в Римском Университете и смонтированного на криогенной антенне гравитационных волн в ЦЕРНе. Полученные результаты хорошо согласуются с экспериментальными данными.

     

ESR studies of coenzyme Q1, chromanoxyl and chromenoxyl radicals

ESR measurements were performed for the coenzyme Q₁, chromanoxyl and chromenoxyl radicals obtained by oxidizing the phenol precursors with PbO₂ in toluene, and the proton hyperfine splittings were correctly determined.     

The synthesis of propellance compounds from 2,3-disubsituted indoles and o-benzoquinones

The reaction of 2,3-dihydro-1H-cyclopent[b]indole 3 and 1,2,3,4-tetrahydrocarbazole 4 with substituted o-benzoquinones yielded [4.3.3]- and [4.4.3]propellanes, respectively. The physical and chemical properties of the propellane compounds were investigated and a mechanism for the formation of the propellane compounds was discussed.     

Cationic ring‐opening copolymerization behavior of trioxane and seven‐membered cyclic carbonate

Cationic ring‐opening copolymerization behavior of trioxane (TOX) and a seven‐membered cyclic carbonate, 1,3‐dioxepan‐2‐one (7CC) is described. When TOX and 7CC were cationically copolymerized under various feed ratios using trifluoromethane sulfonic acid (TfOH) as an initiator in nitrobenzene at 30 °C, 7CC was consumed faster than TOX and the decarboxylation was accompanied to afford the corresponding polyacetal–polycarbonate type copolymers containing poly(oxytetramethylene) units. The copolymer composition could be controlled by the feed ratio of 7CC, whose increase resulted in the high copolymer composition of the 7CC unit. The solubility of the copolymers increased as the increase of the 7CC content. Thermogravimetric, size‐exclusion chromatographic, and X‐ray analyses of the copolymers suggest that the sequences of the copolymer chains consist of the segments containing the units originated from 7CC and those with TOX unit‐rich compositions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 733–739, 2008     

Experimental analysis of thermal displacement and strain distributions in a small outline J-leaded electronic package by using wedged-glass phase-shifting moiré interferometry

To evaluate the influence of a printed wiring board (PWB) with a high coefficients of thermal expansion (CTE) on the thermal deformation of a small outline J-leaded electronic package (SOJ), a newly developed phase-shifting method was applied to moiré interferometry. This phase-shifting moiré interferometry method uses a wedged glass plate as a phase shifter to obtain displacement fields with a sensitivity of 100 nm/line. This technique also enabled the quantitative determination of strain distributions in all observation areas. Thermal loading was applied from room temperature (25 °C) to an elevated temperature (100 °C), and then the thermal strains of SOJ with and without the PWB were compared. The results showed that the concentrations of the longitudinal strains ε_xx and ε_yy became increasingly prominent when mounted on the PWB, and the shear strains γ_xy were concentrated at the corners of the silicon chip. The values of these strains increased by about 50% when the SOJ was mounted on the PWB.