Rupture Properties of Wheat Gluten in Simple Tension: The Role of Hydrogen Bonds

Gluten obtained from hard red winter wheat flour was freeze-dried and reconstituted wth deuterium oxide and aqueous solutions of urea to selectively alter the extent of hydrogen bonding. The rupture properties of the modified glutens were studied in simple tension at seven rates of strain covering three orders of magnitude (2.86 × 10^-2 to 28.6 min^-1). Tensile strength and rupture strain decreased steadily with the extent of hydrogen bonding disruption, i.e., with increase in urea concentration. For a given type of modified gluten, the strain at rupture was independent of the rate at which the material was deformed and the tensile strength increased with increasing deformation rate.     

Grain growth of copper films prepared by chemical vapour deposition

Copper films having thickness 600 nm were prepared on TiN using chemical vapour deposition (CVD). The deposited films were annealed at various temperatures (350–550°C) in Ar and H₂(10%)-Ar ambients. The changes in the grain size of the films upon annealing were investigated. Annealing in an H₂(10%)-Ar ambient produced normal grain growth; annealing in an Ar ambient caused grain growth to stop at 550°C. The grain size followed a monomodal distribution and the mean size increased in proportion to the square root of the annealing time, indicating the curvature of the grain is the main driving force for grain growth. Upon annealing at 450°C for 30 min in an H₂(10%)-Ar ambient, the average grain size of the film increased from 122 nm to 219 nm, and the resistivity decreased from 2.35 μΩ cm to 2.12 μΩ cm at a film thickness of 600 nm. This revised version was published online in July 2006 with corrections to the Cover Date.     

Apparent shear viscosity of native egg white

Temperature and shear dependency of the apparent viscosity of the thick and thin portions of egg white from fresh hen eggs, in their native state was investigated. The viscosity of the egg white was determined in the temperature range of 5–30°C and the shear rate range 34–600 sec^-1. The viscosity of both the thick and thin portions of the egg white decreased with increase in temperature. The thin portion showed no decrease in viscosity with shearing time at constant shear rates while the viscosity of the thick portion decreased within the first 6 min of shearing and then remained constant. The rate of decrease in viscosity with shearing time was more at higher temperatures. At 20°C and a shear rate of 34.2 sec^-1, the equilibrium-apparent viscosity of the thick portion was 160 cp, approximately forty times greater than that of the thin portion (4cp). This difference in viscometric properties may be due to the presence, in the thick portion, of high molecular weight complexes which are disrupted under shearing.     

Release of Single-Cell Protein by Induced Cell Lysis

A temperature sensitive lysis mutant of Saccharomyces cerevisiae JD 109, which grows normally at 27°C, stops growing and partially lyses at a nonpermissive temperature (37°C). In studies in a 14L fermentor with temperature shifted (from 27°C to 37°C) at 3.0 g/L cells, the effect of pH was investigated with the result that the rate of lysis is faster at pH 8 than at pH 5.6; the protein in the cells decreases from 45 to 35%. When both pH (from 5.6 to 8.0) and temperature are shifted, the culture showed a more noticeable inhibition of growth and lysis than when only pH was changed and the temperature was maintained at 27°C.     

Silver-palladium alloy deposited by DC magnetron sputtering method as lubricant for high temperature application

The silver-palladium(Ag-Pd) alloy coating as a solid lubricant was investigated for its application to the high temperature stud bolts used in nuclear power plants. A hex bolt sample was prepared in the following steps: 1) bolt surface treatment using alumina grit blasting for cleaning and increasing the surface area; 2) nickel(Ni) film coating as a glue layer on the surface of the bolt; and 3) Ag-Pd alloy coating on the Ni film. The films were deposited by using a direct current(DC) magnetron sputtering system. The thickness and composition of the Ag-Pd alloy film have effect on the friction coefficient, which was determined using axial force measurement. A 500 nm-thick Ag-Pd (80:20, molar ratio) alloy film has the lowest friction coefficient of 0.109. A cyclic test was conducted to evaluate the durability of bolts coated with either the Ag-Pd (80:20) alloy film or N-5000 oil. In a cycle, the bolts were inserted into a block using a torque wrench, which was followed by heating and disassembling. After only one cycle, it was not possible to remove the bolts coated with the N-5000 oil from the block. However, the bolts coated with the Ag-Pd (80:20) alloy could be easily removed up until 15 cycles.