Li(+) ion conductivity in rock salt-structured nickel-doped Li(3)NbO(4)

Two mechanisms of doping Li(3)NbO(4), which has an ordered, rock salt superstructure, have been established. In the "stoichiometric mechanism", the overall cation-to-anion ratio is maintained at 1:1 by means of the substitution 3Li(+) + Nb(5+) --> 4Ni(2+). In the "vacancy mechanism", Li(+) ion vacancies are created by means of the substitution 2Li(+) --> Ni(2+). Solid solution ranges have been determined for both mechanisms and a partial phase diagram constructed for the stoichiometric join. On the vacancy join, the substitution mechanism has been confirmed by powder neutron diffraction; associated with lithium vacancy creation, a dramatic increase in Li(+) ion conductivity occurs with increasing Ni content, reaching a value of 5 x 10(-4) Omega(-1) cm(-1) at 300 degrees C for composition x= 0.1 in the formula Li(3-2x)Ni(x)NbO(4). This is the first example of high Li(+) ion conductivity in complex oxides with rock salt-related structures.     

Photobiology of RNA bacteriophages. II. U.V.-irradiation of f2: effects on extracellular stages of infection and on early replication

Abstract— The effect of u.v. irradiation (2537 Å) on the RNA bacteriophage f2 has been studied with respect to the adsorption of f2 to E. coli K12 (male strain), the penetration of f2-RN A into the host cell and the conversion of the phage nucleic acid to the double-stranded replicative intermediate. The biological parameter most sensitive to u.v. was the plaque-forming ability of the phage. Its loss could be attributed to several factors. (1). A binding of capsid protein to phage nucleic acid interfering with host penetration by the f2-RNA. (2). Desorption of some irradiated phage at 37° from their attachment sites on the host. (3). Molecular alterations in the RNA preventing formation of the replicative intermediate within the host. The relationship of these factors to the lack of photoreactivability of irradiated f2 is discussed.     

Univalent salts as modifiers in micellar capillary electrophoresis

The influence of three univalent salts (LiCl, NaCl and RbCl) on the separation of amino acids labelled with 3-(4-carboxybenzoyl)-quinoline-2-carboxaldehyde (CBQCA) in micellar capillary electrophoresis has been studied. Capacity factors for a series of eight CBQCA-labelled amino acids in a sodium dodecyl sulfate (SDS) micellar system containing different concentrations of salt were measured and were found to be related to both the hydrodynamic radius of the salt counter-ion (Li(+), Na(+), Rb(+)) and the relative hydrophobicity of the amino acid. Affinities of the analytes for the micelles were generally observed to decrease as the salt concentration in the background electrolyte was increased from 10 to 50 mM. This decrease in affinity was greatest in the presence of the salt counter-ion with the smallest hydrodynamic radius and is primarily due to an increased resistance to mass transfer. Furthermore, interaction of hydrophobic analytes with the micelles is greater than that of hydrophilic analytes at all salt concentrations due to the greater strength of the hydrophobic interactions and this effect is also enhanced in the presence of a smaller counter-ion. No negative effects due to Joule heating or electromigrative dispersion were observed for low to moderate concentrations of salt, which suggests that the use of simple univalent salts to modify analyte/micelle affinities can be a practical method for improving the separation of complex mixtures.     

Characterization of implantable microfabricated fluid delivery devices

The formal characterization of the performance of microfluidic delivery devices is crucial for reliable in vivo application. A comprehensive laboratory technique was developed and used to optimize, calibrate and validate microfabricated fluid delivery devices. In vivo experiments were carried out to verify the accuracy and reliability of the pressure driven devices. Acute guinea pig experiments were conducted to measure the response to /spl alpha/-amino-3-hydroxy-5-methyl-4-isoxalone propionic acid, an excitatory neurotransmitter, at multiple locations in the inferior colliculus. A nondimensional parameter, Q/spl tilde/, was successfully used to classify devices in terms of geometry alone (i.e., independent of fluid properties). Functional devices exhibited long-term linearity and reliability in delivering single phase, Newtonian fluids, in discrete volumes with a resolution of 500 picoliters at less than 0.45 lbf/in/sup 2/ (30 mbar) pressure drop. Results for non-Newtonian fluids are not presented here. The acute results showed a proportional increase in the firing rate for delivered volumes of 2 nL up to 10 nL (at rates of between 0.1 and 1 nL/s). Flow characteristics are maintained during acute experiments and post-implant. A control experiment conducted with Ringer solution produced negligible effects, suggesting the results to be truly pharmacological. The experimental techniques employed have proven to be reliable and will be used for future calibration and testing of next generation chronic microfluidic delivery devices.     

The one dimensional quantised ballistic resistance in GaAs/AlGaAs heterojunctions with varying experimental conditions

The quantisation of the one-dimensional ballistic resistance has been investigated in “split-gate” high electron mobility structures where the gates define a narrow quasi-one-dimensional channel in an otherwise two-dimensional electron gas. Various authors have made theoretical predictions about the effects on this quantisation of device geometry and experimental conditions. We present new experimental data from a series of such structures, and focus on two phenomena: length-dependent resonances in the resistance and the possibility of negative differential resistance.     

Sampling techniques applied to the derivation of impedance characteristics for use in power-system protection

Impedance is measured by sampling the voltage and current magnitudes. The sampling period is 50?s, and the point at which sampling takes place is measured from either the current or the voltage zero. Compound impedance characteristics can be achieved by sampling at a number of points in each halfcycle.