Wavelength-Division Multiplexing Switches Using Free-Space Optics

Optical crossbar switches were fabricated using multiwavelength vertical-cavity surface-emitting lasers and free-space microoptics. Four-channel optical switches with 10-nm wavelength intervals were successfully demonstrated.     

Chiral anomalies, effective lagrangians and differential geometry

Using the differential geometric approach developed by Zumino and others, we study the relation between chiral anomalies and the effective lagrangian. We present a simple formula for the non-abelian (Bardeen) anomaly in any even dimensions. This is used to introduce gauge couplings to the Wess-Zumino effective action, as suggested by Witten.     

Zirconia based oxide ion conductors for solid oxide fuel cells

The electrical conductivity in the ZrO₂-Ln₂O₃ and ZrO₂-MO₂-Ln₂O₃(M = Hf, Ce, Ln = lanthanides) systems has been examined.The highest conductivity of 0.3 S/cm at 1000 °C was found in the ZrO₂-Sc₂O₃ system. The addition of MO₂ into the ZrO₂-Ln₂O₃(Ln = Sc, Y, Yb) systems showed the conductivity decreasing. The conduction mechanism in the zirconia based oxide ion conductors was discussed in view of the dopant ionic radius. The aging effect of the conductivity in the ZrO₂-Ln₂O₃ systems has been measured in a temperature rang 800–1000 °C. ZrO₂ with a high content of Ln₂O₃ showed no significant conductivity degradation. Paper presented at the 97th Xiangshan Science Conference on New Solid State Fuel Cells, Xiangshan, Beijing, China, June 14–17, 1998.     

Surface electronic structure of binary metal oxide catalyst ZrO2/SiO2

The surface electronic structure of the binary metal oxide ZrO₂/SiO₂ was studied by means of XPS and the decrete variational (DV) Xα cluster model calculation. The results show that when ZrO₂, was supported on SiO₂, the SiO bond of SiO₂, neighboring ZrO₄, became stronger and that the Brönsted acid site H which is located on the SiO₄ unit exhibits stronger acidity.     

Isotopically selective CVD of silicon by IRMPD of Si2F6

The IRMPD of Si₂F₆ by a CO₂ TEA laser was applied to isotopically selective CVD of silicon. A white film, probably consisting of polymers of SiF₂, was deposited on a metal foil during the irradiation of natural Si₂F₆ with the laser radiation at 951.19 cm^–1 and about 1.5 J cm^–2. Upon heating, the film became dark brown, evolving SiF₄. The³⁰Si content was found to be as high as about 20%.     

Crystal orientation in a semicrystalline polymer in relation to deformation of polymer spherulites. IV. Crystal orientation mechanism of nylon-6 under uniaxial stretching

A model relating crystal orientation to the deformation of nylon-6 spherulites under uniaxial stretching is discussed in terms of the orientation distribution functions of reciprocal lattice vectors of crystal planes, such as the (002) and (200) planes. The distribution functions calculated from the model are compared with those obtained from x-ray diffraction experiments. It is found that the crystal a axis and, consequently, the direction of hydrogen bonds within the crystal (α modification) orient parallel to the lamellar axis in the undeformed state, and that the crystal orientation behavior of nylon-6 is much different from that of low-density polyethylene, being characterized by much smaller values of the reorientation parameters of crystallites within orienting lamellae. Moreover, small-angle light scattering for H_v and V_v polarization is also calculated on the basis of the spherulite deformation model by taking the nylon-6 crystal as having orthogonal–biaxial symmetry in optical anisotropy. It is concluded that the H_v scattering can be realized in terms of the proposed model for spherulite deformation by taking into account a considerable contribution of hydrogen bonds to the molecular polarizability, so as to make the polarizability along the crystal a axis larger than that along the b axis. In other words, this conclusion suggests positively birefringent spherulites in the nylon-6 samples studied.     

Grain boundary relaxation phenomena in block and graft copolymers

Summary The grain boundary relaxation phenomena, which have been found in the mechanical relaxation of the cast films of a series ofgraft copolymers ofpoly(methyl acrylate) with styrene, are examined again, in order to understand its relaxation mechanism, by using some particular series of heterogeneous systems of two components having different interaction between the two phases and, subsequently, different grain boundary structure; i. e., two series of poly(vinyl acetate) filled with two types of carbon blacks having relatively high and low surface activities, respectively, a series ofmechanical mixtures ofpoly(vinyl acetate) with polystyrene, and a series of styrene-isoprene-styrene tri-block copolymers.The grain boundary relaxation phenomena are again detected for the series of the tri-block copolymers but definitely not for the series of the mechanical mixtures, suggesting that the grain boundary relaxation phenomena must arise not from the heterogeneous structures themselves but from characteristic arrangements of molecular chains at the boundary of the two phases. That is, there must be a considerably strong interaction between the two phases, and there exists an intermediate phase in which the polymer segments of soft component are rigidified while the other polymer segments of hard component are softened. In other words, there must be a cooperative motions of chain segments of the two components to produce a mechanical relaxation under a certain environmental condition, such as temperature and time scale of observation.

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Zusammenfassung Die Korngrenzenrelaxationsphänomene, die in der mechanischen Relaxation einer Serie von aus Graft-Copolymeren von Polymethylacrylat mit Styrol gefunden wurden, wurden erneut geprüft, um den Relaxations-mechanismus zu verstehen, unter Verwendung einer besonderen Serie von heterogenen Systemen zweier Komponenten, die verschiedene Wechselwirkungen zwischen den zwie Phasen besitzen und deshalb verschiedene Korgrenzenstrukturen. Das heißt, wir verwendeten zwei Serien von Polyvinylacetaten, gefüllt mit zwei Rußtypen von vergleichsweise hoher und niedriger Oberflächenaktivität, eine Serie von mechanischen Mischungen aus Polyvinylacetat mit Polystyrol und eine Serie von Styrol-Isopren-Dreiblockcopolymeren. Die Korngrenzenrelaxationsphänomene, wurden für die Serie der Dreiblockcopolymeren wiederum festgestellt, aber definitiv nicht für die Serie der mechanischen Mischungen. Das läßt vermuten, daß Korngrenzenrelaxation nicht von heterogenen Strukturen selbst, sondern von charakteristischen Anordnungen der molekularen Kette an der Grenze von zwei Phasen herrührt. Das heißt, es muß eine beträchtlich strenge Wechselwirkung zwischen den zwei Phasen bestehen, und es muß eine Zwischenphase existieren, in welcher die Polymersegmente der weichen Komponente versteift werden, während die anderen Polymersegmente der harten Komponente erweicht werden. Mit anderen Worten, es müssen cooperative Bewegungen von Kettensegmenten der zwei Komponenten vorhanden sein, um eine mechannische Relaxation unter gewissen Umgebungsbedingungenzuerzeugen, Umgebungsbedingungen wie Temperatur und Zeitskala der Beobachtungen.

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With 6 figures and 13 tables

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Presented at the 20th Annual Symposium on Rheology, Japan, Fukui, Oct. 18, 1972.     

Weak coupling perturbative calculations of the Wilson loop in lattice gauge theory

Weak coupling perturbative calculations of the Wilson loop in lattice gauge theory are carried out numerically up to order g⁴. Comparison of the results with those of the Monte Carlo calculations shows that there exists a non-perturbative contribution of an essential singularity type which may be identified as the string tension.     

A new synthesis of olefins. Conversion of nitroolefins into olefins by reductive elimination

A nitro group in nitroolefins is displaced by hydrogen giving the corresponding olefins in good yields by the reaction of nitroolefins with sodium sulfide in the presence of benzenethiol. It proceeds rapidly at room temperature.