Local Proactive Interference in Delayed Matching to Sample: The Role of Reinforcement.

Discriminability in delayed matching to sample was lower when the samples on consecutive trials differed compared with when samples on consecutive trials were the same. This local proactive interference occurred when correct choices on the previous trial were reinforced but not when correct choices on the previous trial were not reinforced. When the choice on the previous trial was incorrect, discriminability was higher on different consecutive trials than on same trials. These effects were amplified by varying the ratio of reinforcers for correct choices, as predicted by a model that attributes local proactive interference to an interaction between control by the sample on the current trial and the influence of reinforcers for correct choices on previous trials. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The effect of stabilisers on the viscosity of an ice cream mix

The effect of locust bean gum, guar gum, sodium carboxymethylcellulose and carrageenan on the viscosity of an ice cream mix has been investigated over a range of shear rates. The effect of temperature on mix viscosity was also determined. The behaviour of the added polysaccharides was compared with their behaviour in other systems and carrageenan was found to show the most significant changes. The relative viscosity of mixes containing anionic polysaccharides increased with decreasing temperature; the relative viscosity of mixes containing neutral polysaccharides was independent of temperature.     

Effect of substituents in the styrene aromatic ring on water absorption and thermal stability of an unsaturated polyester resin

The water absorption at 50°C and dynamic and isothermal thermogravimetric properties were studied for a series of resins made from the same maleic/phthalic anhydride-based unsaturated polyester cross-linked with each of styrene, 4-methyl styrene, 4-ethyl styrene, 4-n-butyl styrene, 4-isopropyl styrene, tertiary butyl styrene, 4-chlorostyrene and 3,4-dichlorostyrene. Chloro substituents and most alkyl groups give rise to a loss of water resistence. However, the tertiary butyl group leads to a decrease in both water absorption and water damage. The thermal stability of the resin is decreased by chloro substituents and increased by n-alkyl groups, and the results suggest that the main degradation step involves styrene residues, but that the initial decomposition does not do so.     

A rapid method for selectively determining small amounts of niacin,riboflavin and thiamine in foods

Niacin, riboflavin and thiamine (as thiochrome) were determined in enzymic hydrolysates of foods by high performance liquid chromatography. Paired ion chromatography, combined with ultraviolet and fluorescent spectroscopy, allowed for highly selective and sensitive detection of the vitamins.The results of the assays were similar to the more time-consuming manual methods but the accuracy and sensitivity were much higher using fluorescent detection.     

The development of a solid state reference electrode for use in soil measurements

A pressed pellet liquid junction membrane and a solid state reference electrode have been developed which, having no solution flow, are not liable to blockage by soil particles. The electrodes provide a reasonably constant “reference” voltage over the range of pH and concentration conditions usually encountered in soils and soil extracts.     

Rapid polymerisation and cross-linking reactions in thin film (1) the stopped-flow rotational viscometer: Construction and preliminary studies

The design and construction of a stopped flow rotational viscometer is described. This novel technique enables rapid polymerisation reactions in thin films to be studied in a controlled environment over a range of temperatures. The apparatus enables two components of a polymerisation system (typically monomer/solvent and initiator/solvent) to be separately and rapidly delivered to the sample cavity of a cone and plate viscometer. The flow of the components can be simultaneously arrested and the viscosity of the resultant monomer/initiator/solvent mixture monitored as a function of time. The system was designed for the study of cyclo olefin-based polymerisation and cross-linking reactions in the development of metal coating systems capable of high cross-linking rates. An initial evaluation was however carried out using the well characterised free radical polymerisation of styrene and the cationic polymerisation of styrene catalysed by boron trifluoride etherate in toluene.     

Mechanisms of reactive sputtering of indium I: Growth of InN in mixed Ar-N2 discharges

Optical absorption and emission spectroscopies were used for in situ investigations of process occuring in the plasma and at the electrode-gas interfaces which control the reactive sputter etching of indium targets and the reactive deposition of InN films in mixed Ar-N₂ glow discharges. The sputtering parameters used were a d.c. target voltage of -2.5 kV, a total sputtering pressure P of 30–70 m Torr (4–9.3 Pa), N₂ mol.% C_N2 values of 0–100 and a target-to-substrate separation d of 3–6 cm. Under these conditions no indication of complete nitride formation at the target surface or of sputter ejection of InN molecular species was obtained. Increasing C_N2 at a constant value of P caused a decrease of the target sputtering rate R. This decrease was due primarily to a decrease in the ion current i_T, which was caused by thermalization of low energy electrons in the plasma through excitation of vibrational modes in molecular N₂. Atomic absorption provided a real-time monitor of R over the entire range of sputtering parameters. The optical emission intensity from sputtered indium atoms in the cathode glow was found to increase with C_N2 (even though R decreased) because of enhanced excitation through collisions with N₂ metastable species.The nitrogen concentration in the deposited films, as determined by X-ray photoelectron spectroscopy and X-ray diffraction, was found to depend strongly on C_N2, P_N2 and d. The dependence on d was caused by the position of the growing film surface with respect to the negative glow region where most of the atomic nitrogen was formed through the reaction N₂⁺ + N₂ → N₂ + N⁺ + N In discharges with short mean free paths this is the primary mechanism of nitrogen incorporation since indium does not chemisorb N₂, only atomic nitrogen. InN films grown on glass substrates at about 80°C were found to be polycrystalline n-type semiconductors with a room temperature resistivity of 40 mΩ cm, a carrier concentration of about 5×10¹⁸ cm^-3 and an electron mobility of approximately 20 cm² V^-1 s^-1. The refractive index at a wavelength of 1 μm and the room temperature direct band gap were found to be 2.85 and 1.7 eV respectively.