Medium-energy ion scattering has been used to determine the atomic structure of two-dimensional and three-dimensional (3D) dysprosium silicide films on the Si(1 1 1) surface. A quantitative study of the ion yield from the dysprosium has enabled the positions of the atoms in the top three layers of the Si(1 1 1)1×1–Dy to be precisely determined. For the case of the Si(1 1 1)(√3×√3)R30°–Dy 3D silicide surface the experimental blocking curves are in agreement with simulations for the structural model determined by surface X-ray diffraction for the Si(1 1 1)(√3×√3)R30°–Er 3D silicide surface. A contraction of 2.0±0.6% in the c-axis lattice constant compared to bulk dysprosium disilicide is found.

The growth of holmium on the Si(111) surface in the sub-monolayer region was investigated using STM. Several metastable reconstructions, including 5×2 and (23×23)R30° were observed during the nucleation of the 1×1 2D rare earth (RE) silicide surface. The authors attempt to combine this data into a detailed picture of the development of the surface, and identify future directions for improving interface quality. Scanning tunnelling spectroscopy data were taken from the 1×1 surface, and compared with published theoretical and photoemission results from other 2D RE silicides.

Holstein cows exposed to simulated summer diurnal ambient temperature cycles of Phoenix, Arizona and Atlanta, Georgia and diurnal modifications of these climates displayed daily cycles fluctuations in plasma thyroxine (T4) and rectal temperatures (Tre). There were daily diurnal changes in T4 and Tre under all simulated climate conditions. Maximal values generally occurred in the evening hours and minimum values in the morning. Although the diurnal rhythm was influenced by the various simulated climates (diurnal modifications) a diurnal rhythm was very evident even under constant conditions at thermoneutral (Tnc) and at cyclic thermoneutral conditions (TN). The major significance of the study is that the initiation of night cooling of the animals at a time when their Tre was highest was most beneficial to maintenance of a TN plasma T4 level. There was a highly significant negative relationship of average T4 and average Tre. There was also a significant negative relationship of feed consumption and average temperature-humidity index (THI).

Protein extract from crown gall tumour tissue, induced on Nicotiana tabacum by Agrobacterium tumefaciens strain T37, synthesized nopalinic acid [N2-(1,3-dicarboxypropyl)ornithine] from l-ornithine and α-ketoglutarate in the presence of NADPH. Label was incorporated into nopalinic acid from both l-ornithine-[14C] and α-ketoglutarate-[14C] in vivo. Nopaline [N2-(1,3-dicarboxypropyl)arginine] did not appear to be metabolized to nopalinic acid in vivo.

Plasma thyroxine levels were measured in twelve species of desert mammals ranging in altitude from the desert floor to montane forest regions. Rodent species from the low desert had lower circulating thyroxine levels than those species found at 1800 m elevation. Total thyroxine plasma levels were significantly related to metabolic rate and ecologic distribution. The low T4 values of species restricted to the desert floor may play a role in adaptation to summer heat and to the scarcity of food and water.

1.1. Plasma glucocorticoids were measured in six species of desert rodents. The data indicated that the primary glucocorticoid in all desert rodents is corticosterone.2.2. Corticosterone plasma levels appeared to be related to ecological distribution of desert rodents.3.3. It is suggested that lower corticosterone plasma levels may play an adaptive role in water conservation and lowered metabolic rates of desert rodents.

1.1. Metabolism, thermoregulatory patterns, pulmocutaneous water loss and hibernation cycles were studied in the rock pocket mouse, Perognathus intermedius.2.2. The thermoneutral zone for P. intermedius was not evident when measurements of rate of oxygen consumption, VO2, were made in April. However, the zone was from about 33 to 36°C when measurements were made in January.3.3. The average VO2 was about 23 per cent higher in January than in April.4.4. At Ta below 30°C, VO2 increased at a rate of 0·2 and 0·22 ml/g. hr for every 1°C decrease during January and April respectively. The rate of increase in VO2 in January was about 13 percent lower as compared to the rate of increase in April.5.5. At ambient temperature Ta above 37°C, VO2 increased during January and showed no appreciable change during April even at a Ta above 40°C.6.6. The Tre is labile even at Ta of 30°C. Tre ranges between 33 and 36°C, and changes in Tre appear to be related to time of day and Ta. Lethal Tre is about 41°C, and the rate of hyperthermia is less rapid than in other species of heteromyids.7.7. The pulmocutaneous water loss increases with rising Ta. Water loss is similar in P. intermedius to other species of Perognathus at Ta of 20–30°C, but at Ta above 30°C, P. intermedius evaporated more than P. californicus.8.8. Daily hibernation occurs spontaneously at Ta below the lower critical temperature and can be induced by food restriction.

Fifteen species of rodents representing three families and a wide range of ecologic distribution were used to investigate relationships between body fat and metabolic rates (Vo2). There was no apparent relationship between fat content and Vo2. The correlation between Vo2, body weight, body water and fat free body weight was essentially the same. Ecologic distribution appears to be of more importance than fat content in modification of Vo2.