Photoinduced electron-transfer reaction of α-bromomethyl-substituted benzocyclic β-keto esters with amines: selective reaction pathways depending on the nature of the amine radical cations

Photoinduced electron-transfer reaction of α-bromomethyl-substituted benzocyclic β-keto esters with tertiary amines was investigated. Debrominated β-keto esters and ring-expanded γ-keto esters were obtained as major products. On the basis of mechanistic experiments it was concluded that these products are formed via a reaction sequence of selective carbon–bromine bond cleavage and subsequent competitive hydrogen abstraction and Dowd–Beckwith ring-expansion of the resulting primary alkyl radicals. The characteristic product distribution observed for the type of amine used is rationalized on the basis of selective reaction pathways of generated radical intermediates that depend on the nature of the amine radical cations.     

Electro-optic modulation analysis of a Y-cut Z-propagation LiNbO3 light modulator: Comparison with an X-cut Z-propagation LiNbO3 light modulator and a dual LiNbO3 crystal type modulator

We analyzed dependence of modulation characteristics on manufacturing errors for a Y-cut Z-propagation (YZ) and an X-cut Z-propagation (XZ) LiNbO₃ (LN) crystal light modulators. We investigated that the modulation of the YZ modulator is hardly affected by small rotation error of Z-axis, while the XZ modulator suffers significant influence. We also analyzed temperature characteristics of modulation of conventional temperature-compensation LN light modulator. These numerical results show that the modulated signal change of the YZ modulator due to temperature variance is not more than 2.5% of that of the temperature-compensation modulator, in the presence of applied electric field of integral times of the half-wave voltage, modulated signal of the YZ modulator is almost independent on the temperature.     

Highly dispersed anodes for solid oxide fuel cells using NiO/YSZ/BZY triple-phase composite powders prepared by spray pyrolysis

NiO/Y₂O₃-stabilized ZrO₂ (YSZ)/Y-doped BaZrO₃ (BZY) triple-phase composite powders were prepared by spray pyrolysis and evaluated for Ni/YSZ/BZY cermet anodes, which are considered effective for dry CH₄ operation in solid oxide fuel cells. The structure of the particles in these powders was fine crystal fragments, and the individual material phases were clearly separated and highly dispersed within the particles. The Ni/YSZ/BZY cermet anodes fabricated with these composite powders maintained a fine electrode microstructure equivalent to that in a simple Ni/YSZ cermet anode manufactured using a composite powder prepared by spray pyrolysis. Furthermore, the addition of BZY improved the anode performance in humidified H₂ and dry CH₄ operation.     

Increased phosphatidylcholine (16:0/16:0) in the folliculus lymphaticus of Warthin tumor

Warthin tumor (War-T), the second most common benign salivary gland tumor, consists mainly of neoplastic epithelium and lymphoid stroma. Some proteins and genes thought to be involved in War-T were evaluated by molecular biology and immunology. However, lipids as an important component of many tumor cells have not been well studied in War-T. To elucidate the molecular biology and pathogenesis of War-T, we investigated the visualized distribution of phosphatidylcholines (PCs) by imaging mass spectrometry (IMS). In our IMS analysis of a typical case, 10 signals were significantly different in intensity (p?+ (m/z 772.5), [PC (16:0/20:4)?+?K]⁺ (m/z 820.5), [PC (16:0/20:3)?+?K]⁺ (m/z 822.5), [PC (18:2/20:4)?+?K]⁺ (m/z 844.5), and [PC (18:0/20:5)?+?K]⁺ (m/z 846.5). PC (16:0/16:0) was increased specifically in the folliculus lymphaticus of War-T lymphoid stroma, suggesting a different metabolism. Localization of PC (16:0/16:0) might reflect inflammation activity participating in the pathogenesis of War-T. Thus, our IMS analysis revealed the profile of PCs specific to the War-T region. The molecules identified in our study provide important information for further studies of War-T pathogenesis.     

Electronic states of lanthanide in the ternary thiogallate CaGa2S4

The electronic states of lanthanide (Ln) doped CaGa₂S₄ are investigated by the molecular orbital calculations for a spherical cluster of LnCa₈Ga₁₂S₂₄ using the FORTRAN program DVSCAT on the basis of the Discrete Variational method with Xα potentials (DV-Xα). In view of the SCF convergence, the Ln-doped lattice should contract to 85-90% of the mother crystal around the Ln atom for the lightweight lanthanides from Ce to Sm. On the other hand, the lattice contraction is very small for the heavyweight lanthanides, especially for Er, Tm and Yb in contrast to the generally known lanthanide contraction for Ln³⁺ ions. This is probably attributed to the effective charges of Ln atoms calculated here to be less than +1 for all lanthanides contrary to the chemically accepted value of +3. The energy level scheme of 4f and 5d related molecular orbitals is proposed for each Ln substituting Ca in CaGa₂S₄, showing that the optical processes relating to the 5d→4f transition must be complicated especially for the lightweight Ln-doped CaGa₂S₄.     

Non-nucleonic degrees of freedom in weak nuclear currents

Some of the key issues in the study of exchange currents in nuclei are surveyed. Particular emphasis is placed on the important connection between exchange-current effects and the effects of chiral symmetry in nuclei, a topic which is investigated with great intensity in the current literature.Supported in part by the National Science Foundation (USA), Grant No. PHYS-9006844.     

Design Considerations of a Television Camera Detecting Oil Slicks on the Sea

This paper describes a television camera system that automatically captures exclusive images of an oil slick on the sea. The system includes two optical wavelength filters (WFs), two charge coupled devices (CCDs), and a differential image circuit that produces an absolute value of a difference signal between two output images from CCDs. The operating principle is based on the fact that, due to the multiple-beam interference in the oil slick, there is a marked difference of intensity between light reflected from the surface of the sea and that from the slick. The probabilities to sense slicks under various conditions were calculated using two types of WF, i.e., a space-invariant WF and a space-variant WF, and it was found that the latter was far superior to the former.     

Photodissociation and geminate dynamics in solution phase: Picosecond transient absorption studies of tetraphenylhydrazines and diphenyl disulfides

Photodissociation of aromatic molecules and the following geminate dynamics of the photochemically produced fragment radical pair in liquid phase are discussed in relation to the results of ultrafast transient absorption measurements. Photodissociation of tetraphenylhydrazine occurs from the unequilibrated excited singlet state competing with the relaxation to the fluorescence state. In addition to the rapid fragmentation, the N?N bond rupture is clearly demonstrated to take place in the fluorescence state of tetraphenyl-and tetratolyl-hydrazine in tens of picoseconds time scale. In the case of di-p-aminophenyl disulfide in nonpolar solvents, geminate recombination of the p-aminophenylthiyl radical and the formation of the radical dimer were observed in tens of picoseconds. The observed slow geminate recombination can be explained by the repulsion between the large dipole of the fragment radical preventing the reformation of the S?S bond and by the restricted conformation required for the dimer formation at the encounter of radicals.