Architectural issues related to the optical implementation of an EGS network based on embedded control

Free-space optical implementations of switching networks have been proposed to circumvent many of the system-level problems that may be encountered in systems that require many high-density, high-bandwidth connections. The details of a new class of switching network (the EGS network), that is well-suited to free-space implementations, is described. The common control injection problem that plagues most free-space photonic networks, i.e. how can control information from an electronic source be injected into the network for applications that require relatively high network reconfiguration rates, is examined. A new technique for control injection, called embedded control, which permits network operation even with relatively high network reconfiguration rates is also proposed.     

Total Positivity Properties of Generalized Hypergeometric Functions of Matrix Argument

In multivariate statistical analysis, several authors have studied the total positivity properties of the generalized (₀ F ₁) hypergeometric function of two real symmetric matrix arguments. In this paper, we make use of zonal polynomial expansions to obtain a new proof of a result that these ₀ F ₁functions fail to satisfy certain pairwise total positivity properties; this proof extends both to arbitrary generalized ( _r F _s ) functions of two matrix arguments and to the generalized hypergeometric functions of Hermitian matrix arguments. In the case of the generalized hypergeometric functions of two Hermitian matrix arguments, we prove that these functions satisfy certain modified pairwise TP₂properties; the proofs of these results are based on Sylvester's formula for compound determinants and the condensation formula of C. L. Dodgson [Lewis Carroll] (1866).     

Structural and electrical characterization of PZT on gold for micromachined piezoelectric membranes

Piezoelectric membranes have been fabricated that incorporate a gold bottom electrode with an adhesion layer of titanium–tungsten (10:90 wt. %). For solution-deposited acetic acid based lead zirconate titanate (HoAc-PZT) with a Zr:Ti ratio of 40:60, the film’s average piezoelectric coefficient, e₃₁, is -5.31 C/m², with a dielectric constant of 814 at 200 Hz, which is similar to values for platinum bottom electrodes. The PZT structure remains columnar on both types of bottom electrodes. Initial fabrication attempts resulted in cracking that initiated in the PZT layer of the structure. X-ray photoelectron spectroscopy was utilized to establish how processing affects diffusion throughout the composite membrane structure. Crack-free membranes were fabricated and tested. This paper discusses the performance properties and piezoelectric fatigue results for these membranes. PACS 77.84.-s; 77.84.Lf     

Preparation of bisdiazoalkane and related complexes from the reactions of diazo compounds with the dinitrogen complexestrans-[M(N2)2(Ph 2PCH2CH2PPh 2)2] (M=Mo or W)

Summary Reactions oftrans-[M(N₂)₂(dppe)₂] (A;M=Mo, W;dppe=Ph ₂PCH₂CH₂PPh ₂) with ethyldiazoacetate, N₂CHCOOEt, yield the bisdiazoalkane speciestrans-[M(N₂CHCOOEt)₂(dppe)₂], upon simple replacement of the dinitrogen ligand by ethyldiazoacetate. However, diazomethane, N₂CH₂, reacts withA with loss of N₂ to give products which we tentatively formulate as containing methylene ligands,trans-[M(CH₂)₂(dppe)₂].

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Herstellung von Bisdiazoalkan- und ähnlichen Komplexen aus den Reaktionen von Diazoverbindungen mit Distickstoffkomplexen des Typstrans-[M(N₂)₂(Ph ₂PCH₂CH₂PPh ₂)₂] mitM=Mo oder W

Zusammenfassung Die Reaktion vontrans-[M(N₂)₂(dppe)₂] (A:dppe=Ph ₂PCH₂CH₂PPh ₂ undM=Mo oder W) mit Ethyldiazoacetat, N₂CHCOOEt, ergab nach einfachem Austausch des Distickstoffliganden mit Ethyldiazoacetat die Bisdiazoalkanetrans-[M(N₂CHCOOEt)₂(dppe)₂]. Diazomethan (N₂CH₂) hingegen reagierte mitA unter Verlust von N₂ zu Produkten, die tentativ alstrans-[M(CH₂)₂(dppe)₂] mit Methylenliganden formuliert wurden.

     

Pyrolysis-mass spectrometry correlations of crosslink density in natural rubber vulcanizates

A set of twelve natural rubber vulcanizates was analyzed by Curie-point pyrolysis-mass spectrometry (Py-MS). Multivariate analysis successfully correlated the Py-MS data with either total or polysulfidic crosslink density measurements. (Polysulfidic means two or more sulfurs.) The principal correlation observed was an increase in the ratio of monomer to dimer pyrolyzate yield with an increase in crosslink density. The feasibility of using Py-MS for total crosslink density determination has thus been demonstrated. The Py-MS data, however, did not allow us to distinguish different types of crosslinks.     

The electronic properties of isocyanides at rhenium—dinitrogen binding sites. Preparation and redox properties of the isocyanide complexes trans-[ReCl(CNR)(Ph2PCH2CH2PPh2)2]

The isocyanide complexes trans-[ReCl(CNR)(dppe)₂] (R  Me, Bu^t, C₆H₄CH₃-4, C₆H₄CH₃-2, C₆H₄Cl-4, C₆H₄OCH₃-4 and C₆H₃Cl₂-2,6; dppe  Ph₂PCH₂CH₂PPh₂) have been prepared by isocyanide displacement of dinitrogen from the parent complex trans-[ReCl(N₂)(ddpe)₂]. Their redox properties have been studied by cyclic voltammetry and are interpreted on the basis of the electronic properties and the geometry of the ligating isocyanides which are believed to be bent in these complexes, appearing to exhibit ligand parameter (P_L) values ca. +0.3 V higher than those which would be expected for linear geometry. A very high polarisability (B ? 3.4) is observed for the {ReCl(dppe)₂} site.