Application of the generalized 2D correlation analysis to dynamic near-edge X-ray absorption spectroscopy data

Application of the generalized 2D correlation analysis to a series of in situ XANES spectra enabled the determination of additional useful information not readily available from the conventional spectra. In addition to the changes in the intensity of the white line and in the pre-edge feature, readily observable in the regular spectra, the generalized 2D correlation analysis clearly evidenced an otherwise imperceptible shift in the main edge energy caused by the gradual reduction of Co(2+) to metallic cobalt. The 2D correlation spectra also allowed the establishment of a time sequence for the changes occurring in the spectral features during hydrogen reduction, which provides valuable information on the reduction mechanism. While the generalized 2D correlation analysis was found to be very useful in obtaining supplementary information from the series of XANES spectra analyzed, interpretation of the correlation intensities should be checked for consistency with the general trend of each spectral feature, as spectral intensities that do not change monotonically may induce changes in the signs of the correlation intensities leading to inaccurately establishing sequences of changes among the spectral features in the series.     

Large electro-optic activity and low optical loss derived from a highly fluorinated dendritic nonlinear optical chromophore

A 3-D shape nonlinear optical chromophore encapsulated by highly-fluorinated dendrons exhibits significantly improved electro-optic properties and optical attenuation.     

Present and Future Cryogenic Experiments on Double-Beta Decay

Thermal detectors are introduced and their possible impact on neutrinoless double-beta-decay (20) search is discussed. The thermal experiment MIBETA is described, reporting the up-to-date limits on ¹³⁰Te and ¹²⁸Te. A new generation experiment, consisting in a large expansion of MIBETA and known as CUORE, is presented and discussed.     

Si DX centers in GaAs at large hydrostatic pressures

A number of experimental and theoretical studies indicate that DX centers in GaAs, its alloys and other III–V semiconductors have negative U properties. Using far infrared localized vibrational mode (LVM) spectroscopy of Si donors in GaAs under large hydrostatic pressure in a diamond anvil cell we have discovered an LVM of the Si DX center. From the ratio of the LVM absorption lines of Si_Ga and Si_DX and the compensation in our GaAs samples, we show unambiguously that two electrons are trapped when the ionized shallow Si donors transform into negatively charged DX centers, in full agreement with the negative U model.Dedicated to H.-J. Queisser on the occasion of his 60th birthday     

Stereochemie von Metallocenen, 11. Mitt.: Die Temperaturabhängigkeit der optischen Rotationsdispersion von α-disubstituierten Ferrocenderivaten: Ermittlung von Konformationsgleichgewichten

Measurements of the temperature dependence of the molecular amplitudes of the Cottoneffects of optically active, α-substituted methylferrocenes [R=COMe, CH=CH₂, C(Me)=CH₂ and C(Cl)=CH₂] in the region of the ?ferrocene absorption band” (around 440 nm) and comparison with corresponding cyclic derivatives prove the preponderance of energetically preferred conformers; these are present in the equilibrium in amounts of 75–90% (cf. Table 4). Therefore, the optical rotatory power of α-disubstituted ferrocene derivatives seems to be caused primarily by these conformational equilibria: The preferred positions of the groups involved (C=O, C=C) relative to the residue of the molecule perturb the inherently symmetrical ?ferrocene chromophore” (which thereby is placed into a chiral environment) and determine the sign of its Cotton effect.     

A scanning and transmission electron microscopic study of the development of the surface structure of neuroepithelial bodies in the mouse lung

Neuroepithelial bodies (NEBs) are groups of neuroepithelial (NE) cells that are localized on mounds on the bronchiolar epithelium of the lung. The present study examined NEBs in mice ranging in age from 2 days before birth to 80 days after birth. The position and surface architecture of NEBs was examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In foetal mice, 2 days before birth, NEBs were distinguished from the rest of the bronchiolar epithelium by a slight elevation of non-ciliated Clara-like cells arranged in a cobbestone-like pattern. The exposed surface of the NEB was identified by small protrusions with regular microvilli intermittenly located at the base of deep clefts between the Clara-like cells. The surface of the Clara-like cells had fewer and smaller microvilli and could be easily distinguished from the apical surface of the NEB. Before birth, the surface of all of the apical cells was covered by regularly placed microville, however after birth some of the more prominently positional apical cells revealed a bare patch at the centre of the portion of apical cell exposed to the lumen of the lung. As the mice aged there was an increase in the number of apical cell protusions observed with centrally positioned bare patches. These two morphologically distinct surfaces of apical cells may have separate specialized functions. The exposed surfaces of apical cells were often observed in pairs and this feature has been observed in various sensory organs providing support for chemoreceptive function. However small bright spheres resembling vesicles were frequently observed on the lumenal surface of apical cells of the centrally placed bare patch. Transmission electron microscopy confirmed the presence of vesicles on the surface of apical cells and due to their location these vesicles were thought to contain a substance secreted into the lumen of the lung by apical cells. The significance of the bare region on the apical cells is not clear in terms of the proposed chemoreceptive function usually attributed to NEBs. It may be possible that the morphological changes observed in apical cells after birth are more appropriate for secretion of than for chemoreception. This is supported by the observation in the present study of vesicles lying on the lumenal surface of the bare region of the apical cell, however the mechanism for secretion of whoel vesicles is not clear and requires further investigation.     

Solid-phase reactions between (100) GaAs and thin-film refractory metals (Ti,Zr, V,Nb, Cr,Mo, and W)

Recently, there has been an increased interest in the applications of refractory metals as gate materials for the self aligned gate process in the fabrications of GaAs field effect transistors. In this study, we systematically investigated the thermally induced interface interactions between (100) GaAs substrates and thin films of refractory metals (Ti, Zr, V, Nb, Cr, Mo, and W). Depth profilings of the M/GaAs interfaces were obtained using conventional and heavy ion Rutherford backscattering spectrometry. Phase identifications were achieved by x-ray diffraction.Results on the phase formation sequence, reaction kinetics, the distribution, composition and structure of the reacted phases and the interface reactivity of these contacts will be presented. Correlations between metal properties (electronegativity and metal-metal bond strength) and kinetics of the reactions (activation energy and reactivity of the interfaces) will also be discussed.     

Baryon-antibaryon asymmetry in a model with domain structure and soft CP violation

We consider a model with an abelian gauge symmetry, a Higgs potential involving two scalar fields, and two spinor fields coupled to the scalars through Yukawa couplings. The model accomodates soft violation of charge conjugation, and a domain structure of the universe with two different types of domains, which have identical energy but are governed by different effective lagrangians. The effective lagrangian has complex c-number coefficients that become parts of effective coupling constants, and these are different in the two kinds of domains. In spite of that fact the model neither predicts any domain-dependent effects, nor any particle-antiparticle asymmetries within domains.