Dinuclear Cobalt Complexes with a Decadentate Ligand Scaffold: Hydrogen Evolution and Oxygen Reduction Catalysis

A new decadentate dinucleating ligand containing a pyridazine bridging group and pyridylic arms has been synthesized and characterized by analytical and spectroscopic techniques. Four new dinuclear cobalt complexes featuring this ligand have been prepared and thoroughly characterized both in the solid state (X‐ray diffraction) and in solution (1D and 2D NMR spectroscopy, ESI‐MS, and electrochemical techniques). The flexible but stable coordination environment provided by the ligand scaffold when coordinating Co in different oxidation states is shown to play a crucial role in the performance of the set of complexes when tested as catalysts for the photochemical hydrogen evolution reaction (HER) and chemical oxygen reduction reaction (ORR).     

Synthesis and Structure Elucidation of 8-Methyl- and 9-Methyl-exo-2-carbomethoxy-endo-tricyclo[5.2.1.02,6]deca-3,8-dien-5-ones

A mixture of 1-methyl- and 2-methyl-1,4,4a,8a,-tetrahydro-endo-1,4-methano-naphthalene-5,8-diones ( 2 & 3 ) was chemically transformed into separable methyl substituted tricyclo[5.2.1.0^2,6]decadienones 7 , 8 & 9 . The structure of 8 & 9 were elucidated via Cope rearrangement of their corresponding allylic alcohols ( 10 & 11 ) to furnish 12 & 13 respectively.     

Soil response to track and wheel tractor traffic

Experiments were conducted on a Eudora silt loam to determine the effect of tracked and wheeled tractor traffic on cone penetration resistance and soil bulk density at three different soil-water content levels. Treatment plots were ripped to a depth of 0.45 m and irrigated 5 days prior to the experiment. Significant differences in penetration resistance and bulk density were observed between the treatments within the plowing depth (0.30 m). After the tractor passes, the average penetration resistance recorded was about 7.5% higher and the soil bulk density was about 3% higher in the wheel treatment plots. However, at the soil-water content level close to Proctor optimum (15% w/w), no significant difference was observed in the average penetration resistance of the two treatments.     

Electrochemical Assay to Detect Influenza Viruses and Measure Drug Susceptibility

An electrochemical assay has been designed to rapidly diagnose influenza viruses. Exposure of a glucose‐bearing substrate to influenza viruses or its enzyme, neuraminidase (NA), releases glucose, which was detected amperometrically. Two methods were used to detect released glucose. First, we used a standard glucose blood meter to detect two viral NAs and three influenza strains. We also demonstrated drug susceptibility of two antivirals, Zanamivir and Oseltamivir, using the assay. Finally, we used disposable test strips to detect nineteen H1N1 and H3N2 influenza strains using this assay in one hour. The limit and range of detection of this first generation assay is 10² and 10²–10⁸ plaque forming units (pfu), respectively. Current user‐friendly glucose meters can be repurposed to detect influenza viruses.     

Ionization of an atom by photoabsorption at high photon energies: unified view in terms of singularities of the Coulombic potentials

We discuss a unified nonrelativistic approach to single and multiple ionization of atoms by absorption of a photon of high incident energy ω (but still ωm). The approach is based on asymptotic Fourier transform theory (AFT), modified by Coulombic interactions. The AFT theory connects the high energy behavior of photoabsorption matrix elements with the singularity structures of the inter-particle Coulomb interactions and takes into account initial and final state correlation. The modification of this AFT result by Coulombic interactions leads to a rapid convergence of cross sections with photon energy. We illustrate these ideas for the simple example of photoionization in a potential and then discuss its generalizations.     

On the p version of the finite element method in the presence of numerical integration

We analyze the error in the p version of the finite element method when the effect of the quadrature error is taken into account. We extend some results by Banerjee and Suri [Math. Comput. 59 , 1–20 (1992)] on the H¹-norm error to the case of the error in the L₂ norm. We investigate three sources of quadrature error that can occur: the error due to the numerical integration of the right-hand side, that due to nonconstant coefficients, and that due to the presence of mapped elements. Presented are various theoretical and computational examples regarding the sharpness of our results. In addition, we make a note on the use of numerical quadrature in conjunction with p-adaptive procedures and on the necessity of overintegration in the h version with linear elements, when the L₂ norm is of interest. © 1993 John Wiley & Sons, Inc.     

On the addition of silver to highT c (Y1Ba2Cu3O7−x ) superconductor

The superconducting transition temperature of the highT _c compound Y₁Ba₂Cu₃O_7−x does not show degradation consequent upon the addition of metallic silver up to a concentration of 60 wt per cent. The X-ray diffraction data confirm that the oxygen deficient distorted orthorhombic perovskite structure of the pure compound stays intact as if silver does not enter the crystal lattice. SEM studies do show the presence of silver at the grain boundaries only. Silver is found to restrict the grain growth.     

Existence of optimal Lagrange multipliers for certain nonconvex allocation problems

The use of Lagrange multipliers for decentralization of large resource allocation problems is well known. However, these dual techniques may suffer from the drawback ofduality gaps, to guarantee the absence of which various functions are required to be convex. This limits greatly the applicability of the decentralized approach. We show that less restrictive conditions can be formulated for a certain class of allocation problems, which we call resource management problems, which typically occur in large operational systems. We present a theorem for the existence of optimal multipliers, while placing almost no restrictions on the forms of the resource usage functions or the domains of the decision variables. Efficient solution algorithms, with provable convergence properties, have been given in a companion paper. Our results justify the application of dual methods to this class ofreal-world problems.The author is indebted to Mr. G. Karady and Professor Y. C. Ho of Harvard University for their valuable comments, and also to the referees for their helpful suggestions. This research was partially supported by the Office of Naval Research, under the Joint Services Electronic Program, Contract No. N0001475-C-0648, and by the National Science Foundation, Grant No. ENG-78-15231.     

Designing Least-Cost Nonblocking Broadband Networks

Integrated network technologies, such as ATM, support multimedia applications with vastly different bandwidth needs, connection request rates, and holding patterns. Due to their high level of flexibility and communication rates approaching several gigabits per second, the classical network planning techniques, which rely heavily on statistical analysis, are less relevant to this new generation of networks. In this paper, we propose a new model for broadband networks and investigate the question of their optimal topology from a worst-case performance point of view. Our model is more flexible and realistic than others in the literature, and our worst-case bounds are among the first in this area. Our results include a proof of intractability for some simple versions of the network design problem and efficient approximation algorithms for designing nonblocking networks of provably small cost. More specifically, assuming some mild global traffic constraints, we show that a minimum-cost nonblockingstarnetwork achieves near-optimal cost; the cost ratio is at most 2 if switch source and sink capacities are symmetric and at most 3 when the total source and sink capacities are balanced. In the special case of unit link costs, we can show that a star network is indeed the cheapest nonblocking network.