Optimized partitioning of a wavelength distributed data interfacering network

A fiber optic ring network, such as fiber distributed data interface (FDDI), can be operated over multiple wavelengths on its existing fiber plant consisting of point-to-point fiber links. Using wavelength division multiplexing (WDM) technology, FDDI nodes can be partitioned to operate over multiple subnetworks, with each subnetwork operating independently on a different wavelength, and inter-subnetwork traffic forwarding performed by a bridge. For this multiwavelength version of FDDI, which we refer to as wavelength distributed data interface (WDDI), we examine the necessary upgrades to the architecture of a FDDI node, including its possibility to serve as a bridge. The main motivation behind this study is that, as network traffic scales beyond (the single-wavelength) FDDI's information-carrying capacity, its multiwavelength version, WDDI, can gracefully accommodate such traffic growth. A number of design choices exist in constructing a good WDDI network. Specifically, we investigate algorithms using which, based on prevailing traffic conditions, partitioning of nodes into subnetworks can be performed in an optimized fashion. Our algorithms partition the nodes into subrings, such that the total traffic flow in the network and/or the network-wide average packet delay is minimized     

Dynamic Waveband Switching in WDM Mesh Networks Based on a Generic Auxiliary Graph Model

Waveband switching (WBS) is a promising technique to reduce the switching and transmission costs in the optical domain of a wavelength-division multiplexing (WDM) network. This paper considers the problem of provisioning dynamic traffic using WBS in a WDM mesh network. The network of interest is a homogeneous WBS network, where each node has the functionality of WBS. The problem is called the dynamic WBS problem, which involves searching waveband-routes or wavelength-routes for the dynamically arriving traffic requests. The objective is to minimize the total switching and transmission costs in the optical domain. To solve the dynamic WBS problem, an auxiliary graph model capturing the network state is proposed. Based on the auxiliary graph, two heuristic on-line WBS algorithms with different waveband grouping policies are proposed, namely the wavelength-first WBS algorithm based on the auxiliary graph (WFAUG) and the waveband-first WBS algorithm based on the auxiliary graph (BFAUG). Simulation results indicate that WBS is an attractive technique which reduces the overall switching and transmission costs by up to 30% in the network. The results also show that the WFAUG algorithm outperforms the BFAUG algorithm in terms of port savings and cost savings.     

secG and temperature modulate expression of azide-resistant and signal sequence suppressor phenotypes of Escherichia coli secA mutants

SecA is a dynamic protein that undergoes ATP-dependent membrane cycling to drive protein translocation across the Escherichia coli inner membrane. To understand more about this process, azide-resistant (azi) and signal sequence suppressor (prlD) alleles of secA were studied. We found that azide resistance is cold sensitive because of a direct effect on protein export, suggesting that SecA-membrane interaction is regulated by an endothermic step that is azide inhibitable. secG function is required for expression of azide-resistant and signal sequence suppressor activities of azi and prlD alleles, and in turn, these alleles suppress cold-sensitive and export-defective phenotypes of a secG null mutant. These remarkable genetic observations support biochemical data indicating that SecG promotes SecA membrane cycling and that this process is dependent on an endothermic change in SecA conformation.     

Selective monitoring of peptidase activities with synthetic polypeptide substrates and polyion-sensitive membrane electrode detection

A novel method to monitor specific peptidase activities in biological samples as complex as undiluted plasma/blood is described. The approach is based on the design of synthetic polypeptide substrates in which di- or triarginine sequences are linked to each other via one or more other amino acids recognized specifically by the peptidase to be determined. Detection of chymotrypsin and renin activities using synthetic substrates P4 (F-R-R-R-F-V-R-R-F-NH2) and P5 (R-R-R-L-L-R-R-L-L-R-R-R), respectively, serves to demonstrate the principles of this new assay system. A polyion-sensitive membrane electrode, prepared by doping polymer films with dinonylnaphthalene-sulfonate (DNNS), is shown to exhibit significant nonequilibrium electromotive force (EMF) responses toward these and other polycationic substrates at microgram/milliliter levels under physiological conditions. The same electrode, however, exhibits much smaller total EMF response toward the shorter fragments of the synthetic peptides generated by peptidase activity; hence, the addition of peptidase to a solution containing the synthetic substrate yields a change in electrode EMF response, the rate of which is proportional to the activity of peptidase present. Other synthetic polycationic peptides as well as natural polycationic peptides (e.g., protamine) that lack specific cleavage sites for chymotrypsin and renin, yet are detected by the DNNS-based membrane electrode, do not elicit any significant change in EMF response in the presence of the peptidases, confirming the feasibility and utility of the proposed bioanalytical method.     

Analysis of linkage between beta-lactoglobulin and J blood group system loci in cattle

Linkage between loci controlling variants of beta-lactoglobulin and blood groups of the J system in cattle was studied by means of stochastic genetic methods reported earlier. The studies were conducted on a herd of Black Pied cattle improved with Holstein sires; population genetic data were analyzed. A plot for lod score was constructed, and point (r - 0.28) and interval estimations of the coefficient of recombination were obtained. The results are in good agreement with earlier reported data on other subjects.     

The orthogenesis of atherosclerosis]

It has been ascertained that myofibroblasts penetrating the aortal intima from the medium layer because of its compensatory rearrangements in sites of wear and pull of the vascular wall when a fibrous plaque becomes a lipid one, get transformed in stages. Ordinarily elongated orderly arranged cells become spider-like ones, polymorphous, disintegrated cells. Lipid drops get accumulated in their cytoplasma. The above myofibroblasts were identified as Langhans' cells. Changes are reported in aortal intima plaques identical to those occurring in cell culture near the Ge?flik's [correction of Geuflick's] line. It means that accumulation of lipids in aortal plaques and atheromatous degeneration of the latter may be related to aging and necrosis of myofibroblasts which reach the Ge?flik's [correction of Geuflick's] line too soon in such sites of their compensatory proliferation as enlargements of fibrous tissue in the intima. Thus, atherosclerosis is to be regarded as quite a natural process, as reaction of re-arrangements of the vascular wall in sites of its premature wear. Prophylaxis of atherosclerosis is a problem of major social concern, which may be solved only through providing adequate conditions of work and life, cultivating a healthy life style.