Reliability-Equivalent-Replacement of a Subnetwork

Criteria for two-subnetworks that can replace each other in a network without changing the network reliability are obtained. 2-Node connected subnetworks are replaced by at most three parallel lines and certain 3-node connected subnetworks are replaced by a star composed of three oriented lines.     

Reliability-Equivalent-Separation of a Node

A criterion is obtained for separating a node into two or more nodes without changing the network reliability. If a network with exactly one input node, a network with exactly one output node or a network composed of only nonoriented lines has such a reliability-equivalent-separable node, then the network can be separated into two or more s-independent subnetworks by separating the node into two or more nodes. The network reliability can be obtained as a product of the subnetwork work reliabilities. If a network has such a separable node, then computation of the network reliability can be appreciably reduced by separating the nodes. Examples are provided.     

Partial Liquid-Phase Hydrogenation of Benzene to Cylohexene on SiO2-Immobilized Lanthanide (Eu and Yb) Catalysts

SiO₂-immobilized Eu and Yb catalysts (Si–O–Ln–NH₂) obtained by the reaction of surface hydroxyl groups on SiO₂ with lanthanide metals dissolved in liquid ammonia are active for the partial liquid-phase hydrogenation of benzene to cyclohexene when the reaction was carried out at 423–483 K with hydrogen pressures of 1–5 MPa. Interestingly, only divalent amides are catalytically effective for the partial hydrogenation of benzene.     

Infrared spectra of dinitrogen adsorbed on bimetallic lanthanide (Eu or Yb)–Ni/SiO2 catalysts

Bimetallic lanthanide (Ln: Eu or Yb)–Ni/SiO₂ catalysts prepared by the use of dissolution of lanthanide metals in liquid ammonia have been studied by infrared spectroscopy for dinitrogen adsorption. The infrared spectra were measured at 133–300 K using Ln–Ni/SiO₂ obtained when the Eu or Yb metal dissolved in liquid ammonia reacted with 20 mass% Ni/SiO₂ in different ratios. Infrared spectra for Eu–Ni/SiO₂ showed absorption bands at 2336, 2265, 2254 and 2227 cm⁻¹ at 133 K, which disappeared upon evacuation. The adsorbed state was found to be all molecular from the isotope shift using ²⁸N₂ and z³⁰N₂₈. The bands at 2254 and 2227 cm⁻¹ of them were assigned to new adsorbed dinitrogen species resulting from synergetic interactions between the europium and nickel metal. The concentration of adsorbed dinitrogen on Eu–Ni/² varied markedly with the Eu/Ni ratios, and particularly, it increased in the region of high Eu content. Upon introduction of ytterbium onto nickel, new bands at 2254 and 2226 cm^−- similarly appeared. However, the dependence of dinitrogen adsorption as a function of Yb content in Yb–Ni/SiO²> was somewhat different from that for Eu–Ni/SiO₂. The effects of lanthanide on the surface of Ln–Ni/SiO₂ were discussed in connection with the variation in catalytic properties. This revised version was published online in July 2006 with corrections to the Cover Date.     

The active site of carboxypeptidase Taq possesses the active-site motif His-Glu-X-X-His of zinc-dependent endopeptidases and aminopeptidases

Carboxypeptidase (CPase) Taq possesses the His–Glu–X–X–Hissequence, which is the consensus sequence in the active siteof zinc-dependent endopeptidases and amino-peptidases, at positions276–280. Amino acid replacement of the conserved His andGlu drastically diminished the activity of CPase Taq, and thezinc content of the enzyme was also greatly reduced when eitherof the two His residues was replaced with Arg or Tyr. The resultsindicate that this sequence actually functions as the activesite in CPase Taq, showing that CPase Taq is a novel type ofzinc-dependent CPase that possesses the His–Glu–X–X–Hisactive-site motif.     

Equivalence of a Nonoriented Line and a Pair of Oriented Lines in a Network

Equivalence of a nonoriented line and a pair of oriented lines (in the reliability-sene) is examined for four types of networks. Type I has one input node and one output node; type II has one input node and two or more output nodes; type II' has two or more input nodes and one input node; type III has two or more input nodes and two or more output nodes. For types I, II, II', every non-oriented line is equivalent to a pair of oriented lines with equal line-reliability. The result corresponds to the presumption that almost every one has taken for granted. However equivalence of such a replacement is not true for a type III network.