Diffusion in gold and Au-Ag alloys

The self-diffusion coefficients of gold in pure gold and alloys of gold and silver have been measured over a range of temperatures. Chemical interdiffusion coefficients have been measured on pure metal and incremental couples, but are of lower accuracy because of the development of porosity. The results are compared with earlier work and internally on the basis of Darken’s equations.     

Relationship of senescence of corn (Zea mays L.) stalk pith, cob parenchyma and first developed leaf tissues to RNA content and synthesis

In stalk parenchyma tissue of WF9 X 38-11 single corn (Zea mays L.), there was a per cell increase in RNA synthesis and a slight increase in total RNA as cells became older. In cob parenchyma tissue of WF9 X 38-11 single cross corn, both total RNA content and RNA synthesis per cell decreased with the age of cells. In first developed leaf tissue of FR43 X FR14A single cross corn, RNA synthesis increased steadily but only slightly over its life span. The pattern of RNA synthesis and destruction in senescing leaf tissue of seedlings and two sources of parenchyma tissue of maturing plants appeared to differ.     

Heat storage in eutectic alloys

Classical thermodynamic equations based on the regular solution approximation yield enthalpic changes for eutectic transformation that agree roughly with values measured for several binary and ternary alloy systems by differential scanning calorimetry or differential thermal analysis. Restricting measurements to binary and ternary alloys of the relatively plentiful elements Al, Cu, Mg, Si and Zn, it has been verified that the best heat storage densities on a mass or volume basis are obtained with alloys rich in Si or Al, elements that have large heats of fusion. Several of these alloys have the highest heat-storage density reported for phase change materials that transform between 780 and 850 K. The Mg₂Si-Si eutectic, which has outstanding storage density at 1219 K, illustrates the utility of ordered intermetallic phases with large heat of formation that dissolve in the eutectic liquid to contribute to the entropy change.     

Determination of density changes during melting by X-ray absorption

Continuous measurement of X-ray transmission through a sample confined in a rigid holder permits thermal expansion coefficients of solids, density change during melting, and thermal expansion coefficients of liquids to be determined by a single method as temperature is increased. Application to melting of pure metals and binary eutectics is illustrated for aluminum, the aluminum-silicon eutectic, and the aluminum-copper eutectic. Parameters affecting design and operation of the system are discussed. Formerly Postdoctoral Fellow, University of Delaware formerly Graduate Student,University of Delaware.     

New eutectic alloys and their heats of transformation

Eutectic compositions and congruently melting intermetallic compounds in binary and multi-component systems among common elements such as AI, Ca, Cu, Mg, P, Si, and Zn may be useful for high temperature heat storage. In this work, heats of fusion of new multicomponent eutectics and intermetallic phases are reported, some of which are competitive with molten salts in heat storage density at high temperatures. The method used to determine unknown eutectic compositions combined results of differential thermal analysis, metallography, and microprobe analysis. The method allows determination of eutectic compositions in no more than three steps. The heats of fusion of the alloys were measured using commercial calorimeters, a differential thermal analyzer, and a differential scanning calorimeter. Formerly a Graduate Student, University of Dela     

Nursing in war-time Guernsey: a preliminary review

The research for this article was carried out in the Channel Island of Guernsey during 1996-97 and focuses on the remarkable resilience of a small group of nurses as they strove to provide an emergency hospital service to the civilian population of Guernsey between 1940 and 1945, during which time German forces were in occupation. Insights are provided into a unique period of nursing history, giving a flavour of the harsh environment in which care was provided. Hospital records at the time described a nurse as 'someone who earns her living nursing', therefore the title 'nurse' is used collectively to describe both the qualified State Registered Nurse and the unqualified junior staff. The article is part of an ongoing oral history project representing a collaborative venture between the Department of Health Studies at the University of Lincolnshire and Humberside, and the School of Healthcare Studies at the University of Leeds. Data for this study were obtained from a series of semi-structured audio-taped interviews with 13 former nurses who worked at the States of Guernsey Emergency Hospital during the occupation. Supporting data were derived from official archives, news reports and other published literature. The article is based on the author's inaugural lecture delivered at The University of Lincoln Campus, Friday 30 May 1997.     

On the Mechanism and Kinetics of the Scaling of Iron

The transport mechanisms previously proposed in wustite and hematite have been confirmed by movement of inert markers during the growth of these phases. By similar measurements the mechanism for magnetite has been determined. The rates of growth of multilayer scales on iron, magnetite and hematite on wustite, and hematite on magnetite have been measured. All rates are found to be diffusion controlled under the conditions of the experiments.     

Diffusion and Marker Movements in Beta Brass

Diffusion coefficients and marker movements have been determined in β brass using welded couples. Three different concentration ranges were employed at 750°C, while a fourth concentration range was measured at 500°, 600°, 700°, and 800°C. Marker displacements toward and porosity development in the high zinc side of the couple were observed in all cases. The results were interpreted as favoring a vacancy diffusion mechanism.     

Oxidation of Titanium

The rate of oxidation of titanium in the temperature range 650° to 950°C has been measured. The linear rate law obtained is explained by interface reaction control of the process. Tracer experiments indicate the oxygen diffuses in at least one phase of the scale.