Interfacial chemistry and adhesive durability

The improved understanding of adsorption chemistry which has arisen from the development of new surface analytical techniques during the last twenty years has had a major effect on the understanding of catalytic reaction mechanisms. However, there are many other areas of technology where Interfacial chemistry has a determining role but where the understanding is much less developed. In this paper examples are presented of the role of interfacial chemistry in adhesion. In particular, It Is shown that modification of a surface to the extent of just a few atomic layers in depth can have dramatic effects on the performance of adhesive bonds, particularly when exposed to hostile environmental conditions. These examples will be used to highlight a need for greater fundamental understanding of the interfacial chemistry of adhesion and also other technologies where interface effects are dominant.     

A note on computing environments and network reliability

Interest has increased during recent years in using microcomputers for implementation of network reliability algorithms. There are indications that some implementations suffer severe restrictions imposed by such a computing environment, whereas some other results indicate otherwise. This brief note attempts to clarify the apparently contradictory conclusions that would be naturally drawn from recent papers that treat this subject.     

Increase in leukocyte adhesiveness and aggregation with stress: a model of human congestive heart failure

Stress has a significant influence on the function of the human organism. A simple, rapid, inexpensive, and reliable marker for stress would therefore be of great value. We have recently noted that stress increases the state of leukocyte adhesiveness and aggregation in the peripheral blood. We evaluated 64 patients who had various degrees of congestive heart failure, a condition known to induce a state of physiologic stress, to verify whether a relation exists between the intensity of the stress response and the magnitude of leukocyte adhesiveness. Included in the 64 were 53 patients without congestive heart failure, 23 with compensated failure, 22 with significant congestive heart failure, and 19 with florid pulmonary edema. The percentage of aggregated leukocytes in these four group was 6% +/- 4%, 6% +/- 4%, 10.5% +/- 5%, and 15% +/- 14%. Values for the third and fourth group differed in a statistically significant way. Thus, with further investigation into additional stress-inducing conditions, the state of leukocyte adhesion and aggregation may prove to be a reliable marker for the detection of stress and an inexpensive tool for quantifying its severity.     

An analysis of pH tolerance and substrate preference of isolated skeletal muscle mitochondria from Bufo marinus and Rana catesbeiana

1. The effects of varying pH and substrate on isolated skeletal muscle mitochondria from Bufo marinus and Rana catesbeiana were investigated. 2. For both species, VO2 max significantly decreased at all pH < 7.3 (P < 0.05), while maximum values were observed at a pH range of 7.3-7.6 with B. marinus maintaining a greater VO2 max than R. catesbeiana. 3. Respiratory control values (RCR) decreased significantly at all pH < 6.9 for both species (P < 0.05). 4. Isolated mitochondria from both species were maintained at pH = 7.2 and O2 consumption measured under five separate substrate conditions. 5. A rank preference was established based upon state 3 and RCR values. 6. Substrate preference was identical for both species and interspecific comparisons revealed differences in state 3 respiration and coupling.     

Investigation methods of cerebral perfusion

Brain energy metabolism is essentially oxydative, through the glycolysis and the Krebs cycle. Brain tissue cannot survive more than a few minutes if the substrate (glucose, for which there is no endogenous reserve) or oxygen supply is abolished. Otherwise, there is a precise matching between perfusion (cerebral blood flow-CBF) and oxydative (oxygen consumption-CMRO2) and glycolytic regional metabolism. When intraarterial pressure is decreased (due to a systemic arterial pressure impairment or an arterial obstructive lesion), CBF is maintained constant through an increase of the pial vessels caliber and therefore an enhancement of the cerebral blood volume (CBV); this is cerebral circulatory autoregulation. In physiologic conditions, any increase of the local metabolic demand (during a motor, sensory, or cognitive activation) is supplied through a local enhancement of perfusion, and reversely. Therefore, the measurement of brain perfusion is useful not only to assess the consequences of cerebrovascular or some other diseases, but also to observe the functions involved in the normal working brain. This measurement is most frequently focused on CBF (flow) parameter, but in some clinical circumstances the access to CBV will be also of major importance for a correct understanding of the physiological or pathophysiological situation. We shall describe the different methods available both in clinical and experimental practice, and shall indicate for each one its characteristics, advantages and pitfalls.