A noncompetitive peptide inhibitor of the nicotinic acetylcholine receptor from Conus purpurascens venom

A paralytic peptide, psi-conotoxin Piiie has been purified and characterized from Conus purpurascens venom. Electrophysiological studies indicate that the peptide inhibits the nicotinic acetylcholine receptor (nAChR). However, the peptide does not block the binding of alpha-bungarotoxin, a competitive nAChR antagonist. Thus, psi-conotoxin Piiie appears to inhibit the receptor at a site other than the acetylcholine-binding site. As ascertained by sequence analysis, mass spectrometry, and chemical synthesis, the peptide has the following covalent structure: HOOCCLYGKCRRYOGCSSASCCQR* (O = 4-trans hydroxyproline; * indicates an amidated C-terminus). The disulfide connectivity of the toxin is unrelated to the alpha- or the alphaA-conotoxins, the Conus peptide families that are competitive inhibitors of the nAChR, but shows homology to the mu-conotoxins (which are Na+ channel blockers).     

Design and performance evaluation of a banyan network basedinterconnection structure for ATM switches

This paper presents a new self-routing packet network called the plane interconnected parallel network (PIPN). In the proposed design, the traffic arriving at the network is shaped and routed through two banyan network based interconnected planes. The interconnections between the planes distribute the incoming load more homogeneously over the network. The throughput of the network under uniform and heterogeneous traffic requirements is studied analytically and by simulation. The results are compared with the results of the baseline network and another banyan network based parallel interconnection network. It is shown that, for the proposed design, a higher degree of heterogeneity results in better performance     

Optimal deterministic timeouts for reliable scalable multicast

Reliable multicast protocols suffer from the problem of feedback implosion. To avoid this problem, the number of receivers sending feedback in case of loss must be small. However, losses experienced by different receivers are strongly correlated, since receivers share common resources in the multicast tree. One approach to feedback implosion avoidance relies on delaying feedback at the receivers. We present deterministic timeouts for reliable multicast (DTRM), a distributed algorithm to compute optimal deterministic timeouts for each receiver in a multicast tree as a function of the tree topology and the sender-to-receiver round-trip delays. DTRM has several desirable properties. First, feedback implosion is provably avoided for a single loss anywhere in the tree, provided delay jitter is bounded. Second, the computation of the timeouts can be entirely distributed; receivers and intermediate nodes only rely on local topology information. Third, the timeouts computed by DTRM are optimal with respect to the maximum response time     

Finite element beam propagation method for three-dimensionaloptical waveguide structures

A beam propagation method (BPM) based on the finite element method (FEM) is described for longitudinally varying three-dimensional (3-D) optical waveguides. In order to avoid nonphysical reflections from the computational window edges, the transparent boundary condition is introduced. The present algorithm using the Pade approximation is, to our knowledge, the first wide-angle finite element beam propagation method for 3-D waveguide structures. To show the validity and usefulness of this approach, numerical results are shown for Gaussian-beam excitation of a straight rib waveguide and guided-mode propagation in a Y-branching rib waveguide     

Positive temperature dependence of the electron impact ionizationcoefficient in In0.53Ga0.47As/InP HBTs

Impact ionization is a major limiting factor to the maximum operating voltage of InGaAs-based, high-speed transistors. In this work, data on the positive temperature dependence of the electron impact ionization coefficient α_n in In_0.53Ga_0.47As at medium-low electric fields are reported for the first time. The increase of α_n with temperature is opposite to the behavior normally observed in most semiconductors. This anomalous behavior implies the onset of a positive feedback between power dissipation and avalanche generation which may adversely affect the power handling capability of In_0.53Ga _0.47As-based devices, and which should be taken into account in device thermal modeling. In the experimental procedure, based on the measurement of the multiplication factor M-1 in npn In_0.53Ga _0.47As/InP Heterojunction Bipolar Transistors (HBT), particular care has been taken in order to rule out possible spurious, temperature-dependent contributions to the measured multiplication current     

The strategy of edge wear prediction in CIM concept

A monitoring of tool wear in different cutting operations has been studied for many years. Special techniques have been used to detect a wear status basing upon cutting forces, acoustic emission, temperature, torque and power, vibration, noise and acceleration sensors. The adapting of a proper prediction method allows to solve problems of an automatic supervision in Computer Integrated Manufacturing systems. A task of the abrasive edge wear index prediction can be formulated as follows: disposing by the data collection of the edge wear status in a time period preceding the concerning the wear status in the successive time period embraced by the prediction method.     

Van vleck paramagnetism of the diluted intermetallic compounds Pr1−x Y x Ni5 at fields up to 15 T

We have measured the 16 Hz susceptibility of the diluted Van Vleck paramagnets Pr_1−x Y _x Ni₅ withx=0.00, 0.05, 0.10. 0.20 at temperatures 1.5 K≤T≤50 K and magnetic fields up to 15T. Their Van Vleck type magnetic susceptibility χ(T, B, x) strongly depends on the field atB≥6 T. The temperatureT _max(B, x) of the maximum of χ(T, B, x) decreases at increasing the field from zero to 15 T by approximately one order of magnitude for all Pr_1−x Y _x Ni₅ compounds. Changing the dilutionx from zero to 0.20, the field whereT _max(B, x) strongly drops is increased from 9 T to 11 T. Our data agree qualitatively with the predictions of a point charge model which considers the Zeeman term in addition to the electronic exchange and the dominating crystal field contributions.     

Evaluation of the tensile and fatigue behaviourof a powder metallurgy beryllium/aluminium alloy

The tensile and fatigue behaviour of a powder metallurgy beryllium/aluminium alloy produced by Brush Wellman (Albemet 562) is determined as a function of temperature. The material is shown to have very high stiffness/density compared with common structural materials and moderate strength up to 232°C. The mechanical properties of the material do not vary significantly as a function of orientation for the extruded plate evaluated in this study. The stiffness of the material can be readily explained using standard composite theory, where the material is treated as a beryllium particle-reinforced aluminium matrix composite. To explain the observed strength levels, a combination of microstructural-based dislocation strengthening mechanisms is proposed to act in combination with continuum mechanics strengthening based on load transfer. Failure analysis reveals that the aluminium regions of the material fail in a ductile dimple fashion, while the beryllium regions exhibit a more brittle cleavage type failure. Fatigue failure was found to initiate at inclusions present in the material, but is still very high relative to conventional aluminium alloys. This revised version was published online in November 2006 with corrections to the Cover Date.     

Densification involved in the UV-based photosensitivity of silicaglasses and optical fibers

A comprehensive survey of photosensitivity in silica glasses and optical fiber is reviewed. Recent work on understanding the mechanisms contributing to germanium or aluminum doped fiber photosensitivity is discussed within the framework of photoelastic densification models     

Characterization of localized states in thin PrBa2Cu3O7−x tunnel barriers

Characteristic power-law dependence of junction conductance on temperature was confirmed at low temperatures fora,b-axis oriented Au/PrBa₂Cu₃O_7−x /YBa₂Cu₃O_7−y junctions with a PrBa₂Cu₃O_7−x layer thinner than 30 nm, indicating that current transport via a small number of localized states was predominant. The radius and the density of the localized states were estimated to be 1.1 nm and 5.0x10¹⁹ eV⁻¹ cm⁻³, respectively. Transport measurement at 1.7 K in a magnetic field of up to 6 T revealed no indication of on-site Coulomb repulsion of electrons in the localized states. These results support the possibility of resonant tunneling of Cooper pairs in superconductor-insulator-superconductor junctions with a thin PrBa₂Cu₃O_7−x tunnel barrier.