Temperature dependence of hydrogen evolution reaction on nickel oxide electrode in sealed nickel/cadmium cells

The impedance of sealed nickel/cadmium cells around a cell e.m.f. of 0.0 V was measured at five different temperatures between � 10 and +30 °C. The results show that the behaviour is similar at all temperatures. Based on the experimental results, the relation between charge-transfer resistance (Rct) and temperature (T) has been established for the Volmer reaction. Further, the value of cathodic transfer coefficient (?) has been estimated.

Texture evolution and operative mechanisms during large-strain deformation of nanocrystalline nickel

The large-strain deformation of nanocrystalline nickel was investigated at room temperature and cryogenic (liquid N-2) temperature. Deformation mechanisms ranging from grain boundary sliding to slip, operate due to a wide distribution of grain sizes. These mechanisms leave their finger print in the deformation texture evolution during rolling of nanocrystalline nickel. The occurrence and severance of different mechanisms is understood by a thorough characterization of the deformed samples using X-ray diffraction, X-ray texture measurements, electron back-scattered diffraction and transmission electron microscopy. Crystal plasticity-based viscoplastic self-consistent simulations were used to further substantiate the experimental observations. Thus, a comprehensive understanding of deformation behavior of nanocrystalline nickel, which is characterized by simultaneous operation of dislocation-dominated and grain boundary-mediated mechanisms, has been developed.

The Determination of the Surface Tensions of Liquid-Iron, Nickel and Iron-Nickel Alloys using the electromagnetic Oscillating Droplet Technique

An oscillating droplet method combined with electromagnetic levitation has been applied to determine the surface tensions of liquid pure iron, nickel and iron-nickel alloys as a function of the temperature. The natural frequency of the oscillating droplet is evaluated using a Fourier analyser. The theoretical background of this method and the experimental set-up were described, and the influence of magnetic field strength was also discussed. The experimental results were compared with those of other investigators and interpreted using theoretical models (Butler's equation, subregular and perfect solution model for the surface phase).

The Determination of the Surface Tensions of Nickel Sulfur Alloys using the Electromagnetic Oscillating Droplet Technique

An oscillating droplet method combined with electromagnetic levitation technique has been applied to determine the surface tensions of liquid nickel sulphur alloys as a function of the temperature and composition. The natural frequency of the oscillating droplet is evaluated using a Fourier analyser, and the influence of magnetic field strength on the surface tension was considered. Furthermore, the applicability of Butler's equation and subregular solution model for the surface was shown to predict the surface tension of the systems containing the surface active elements.

On the exothermic peak during annealing of electrodeposited nanocrystalline nickel

Nanocrystalline metals frequently exhibit poor thermal stability, and the exothermic peak in differential scanning calorimetry is usually attributed to grain growth. We show from experiments on electrodeposited nano-Ni with varying levels of S, and tests with microcrystalline Ni and S powders, that the exothermic peak is associated with the formation of a nickel sulfide phase and concurrent grain growth. Analysis suggests that segregation plays a more important role in limiting grain growth than second-phase particles in nano-Ni. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Microstructure evolution and hardness variation during annealing of equal channel angular pressed ultra-fine grained nickel subjected to 12 passes

The microstructure, thermal stability and hardness of ultra-fine grained (UFG) Ni produced by 12 passes of equal channel angular pressing (ECAP) through the route Bc were studied. Comparing the microstructure and hardness of the as-ECAPed samples with the published data on UFG Ni obtained after 8 passes of ECAP through the route Bc reveals a smaller average grain size (230 nm in the present case compared with 270 nm in 8-pass Ni), significantly lower dislocation density (1.08 x 10(14) m(-2) compared with 9 x 10(14) m(-2) in 8-pass Ni) and lower hardness (2 GPa compared with 2.45 GPa for 8-pass Ni). Study of the thermal stability of the 12-pass UFG Ni revealed that recovery is dominant in the temperature range 150-250A degrees C and recrystallisation occurred at temperatures > 250 A degrees C. The UFG microstructure is relatively stable up to about 400 A degrees C. Due to the lower dislocation density and consequently a lower stored energy, the recrystallisation of 12-pass ECAP Ni occurred at a higher temperature (similar to 250 A degrees C) compared with the 8-pass Ni (similar to 200 A degrees C). In the 12-pass Nickel, hardness variation shows that its dependence on grain size is inversely linear rather than the common grain size(-0.5) dependence.

Impedance peaks of sealed nickel/cadmium cells at low states-of-charge

The impedance of sealed nickel/cadmium cells is measured at low states-of-charge that correspond to a cell e.m.f. range of 0.0 to 1.3 V. The results show that the impedance exhibits a pronounced maximum between 0.3 and 0.45 V. It is concluded that the impedance maxima are due to physicochemical processes taking place at the nickel oxide electrode. The impedance of the nickel oxide electrode is dominated by three different phenomena: (i) a Ni(II)/Ni(III) reaction between 1.3 and 0.8 V; (ii) a double-layer impedance between 0.8 and 0.3 V; (iii) a hydrogen evolution reaction between 0.3 and 0.0 V.

Training-Symbol Embedded, High-Rate Complex Orthogonal Designs for Relay Networks

Distributed Space-Time Block Codes (DSTBCs) from Complex Orthogonal Designs (CODs) (both square and non-square CODs other than the Alamouti design) are known to lose their single-symbol ML decodable (SSD) property when used in two-hop wireless relay networks using the amplify and forward protocol. For such a network, a new class of high rate, training-symbol embedded (TSE) SSD DSTBCs are proposed from TSE-CODs. The constructed codes include the training symbols within the structure of the code which is shown to be the key point to obtain high rate along with the SSD property. TSE-CODs are shown to offer full-diversity for arbitrary complex constellations. Non-square TSE-CODs are shown to provide better rates (in symbols per channel use) compared to the known SSD DSTBCs for relay networks when the number of relays is less than 10. Importantly, the proposed DSTBCs do not contain zeros in their codewords and as a result, antennas of the relay nodes do not undergo a sequence of switch on and off transitions within every codeword use. Hence, the proposed DSTBCs eliminate the antenna switching problem.

DNA polymerase alpha-primase complex from the silk glands of the non-mulberry silkworm Philosamia ricini.

The DNA content in the silk glands of the non-mulberry silkworm Philosamia ricini increases continuously during the fourth and fifth instars of larval development indicating high levels of DNA replication in this terminally differentiated tissue. Concomitantly, the DNA polymerase alpha activity also increases in the middle and the posterior silk glands during development, reaching maximal levels in the middle of the fifth larval instar. A comparable level of DNA polymerase delta/epsilon was also observed in this highly replicative tissue. The DNA polymerase alpha-primase complex from the silk glands of P. ricini has been purified to homogeneity by conventional column chromatography as well as by immunoaffinity techniques. The molecular mass of the native enzyme is 560 kDa and the enzyme comprises six non-identical subunits. The identity of the enzyme as DNA polymerase alpha has been established by its sensitivity to inhibitors such as aphidicolin, N-ethylmaleimide, butylphenyl-dGTP, butylanilino-dATP and antibodies to polymerase alpha. The enzyme possesses primase activity capable of initiating DNA synthesis on single-stranded DNA templates. The tight association of polymerase and primase activities at a constant ratio of 6:1 is observed through all the purification steps. The 180 kDa subunit harbours the polymerase activity, while the primase activity is associated with the 45 kDa subunit.

Measurement of complex optical flow with use of an augmented generalized gradient scheme

We present a method for measuring the local velocities and first-order variations in velocities in a timevarying image. The scheme is an extension of the generalized gradient model that encompasses the local variation of velocity within a local patch of the image. Motion within a patch is analyzed in parallel by 42 different spatiotemporal filters derived from 6 linearly independent spatiotemporal kernels. No constraints are imposed on the image structure, and there is no need for smoothness constraints on the velocity field. The aperture problem does not arise so long as there is some two-dimensional structure in the patch being analyzed. Among the advantages of the scheme is that there is no requirement to calculate second or higher derivatives of the image function. This makes the scheme robust in the presence of noise. The spatiotemporal kernels are of simple form, involving Gaussian functions, and are biologically plausible receptive fields. The validity of the scheme is demonstrated by application to both synthetic and real video images sequences and by direct comparison with another recently published scheme Biol. Cybern. 63, 185 (1990)] for the measurement of complex optical flow.

Iron, cobalt and nickel nanoparticles encapsulated in carbon obtained by the arc evaporation of graphite with the metals

Are evaporation of graphite with Fe, Co and Ni yields two distinct types of metal nanoparticles, wrapped in graphitic layers and highly resistant to oxidation. Electron microscopy shows that the metal particles (10-40 nm) in the stub region are encapsulated in carbon onions, the particles in the soot being considerably smaller (2-15 nm). The metal particles in the soot are either ferromagnetic with lowered Curie temperatures or superparamagnetic.

Measurement of complex optical flow with use of an augmented generalized gradient scheme

We present a method for measuring the local velocities and first-order variations in velocities in a time-varying image. The scheme is an extension of the generalized gradient model that encompasses the local variation of velocity within a local patch of the image. Motion within a patch is analyzed in parallel by 42 different spatiotemporal filters derived from 6 linearly independent spatiotemporal kernels. No constraints are imposed on the image structure, and there is no need for smoothness constraints on the velocity field. The aperture problem does not arise so long as there is some two-dimensional structure in the patch being analyzed. Among the advantages of the scheme is that there is no requirement to calculate second or higher derivatives of the image function. This makes the scheme robust in the presence of noise. The spatiotemporal kernels are of simple form, involving Gaussian functions, and are biologically plausible receptive fields. The validity of the scheme is demonstrated by application to both synthetic and real video images sequences and by direct comparison with another recently published scheme [Biol. Cybern. 63, 185 (1990)] for the measurement of complex optical flow.

On kuhnels 9-vertex complex projective plane

We present an elementary combinatorial proof of the existence and uniqueness of the 9-vertex triangulation of C P2. The original proof of existence, due to Kuhnel, as well as the original proof of uniqueness, due to Kuhnel and Lassmann, were based on extensive computer search. Recently Arnoux and Marin have used cohomology theory to present a computer-free proof. Our proof has the advantage of displaying a canonical copy of the affine plane over the three-element field inside this complex in terms of which the entire complex has a very neat and short description. This explicates the full automorphism group of the Kuhnel complex as a subgroup of the automorphism group of this affine plane. Our method also brings out the rich combinatorial structure inside this complex.

Physicochemical studies of (o-vanillin thiosemicarbazonato)-nickel(Ii) chelate

Five- and six-membered rings result from the chelation of nickel(II) by the dibasic tridentate Schiff base ligand, o-vanillin thiosemicarbazone(o-VTSC), a new chelate prepared and characterized. The structural results are discussed in the light of spectroscopic and other data.

Synthesis and x-ray crystal structure of a CuII-theophylline complex: [Cu(theo)2 (H2O)3]·2H2O

The complex [Cu-II (theo)(2)(H2O)(3)].2H(2)O (theo = theophylline) was obtained from aqueous solution. The crystals belong to the monoclinic system, space group P2(1)/n, and are reflection twins about the (001) face. The structure was solved using data from a twinned crystal and refined to final R and R(W) values of 0.069 and 0.064, respectively. Copper has a square-pyramidal coordination with two thee molecules coordinating through N(7) at equatorial positions. The remaining sites are occupied by water molecules. O(6) of one of the thee molecules is at the other axial site at a longer distance of 3.18 Angstrom. This could lead to an alternate (4+1+1) octahedral coordination geometry for Cu-II. The packing is stabilized by stacking interactions between the theophylline moieties at an average separation of 3.46 Angstrom.