Quartz Sand: Apparent dehydroxylation – rehydroxylation and water retention

The lack improvement in the capillary rise and retention of water in quartz sand dehydroxylated by calcination after its hydroxylation and rehydroxylation by alkali, hot water and H₂O₂ treatments, can be accounted for by its instantenous hydroxylatiton and rehydroxylation or by the limited effect of the OH groups on those hydric properties. An alternative interpretation could be a lack analogy between silica and quartz.     

Measuring yield-reducing plant water potential depressions in wheat by infrared thermometry

Summary Measurements of foliage and air wet- and dry-bulb temperatures were made over six differentially irrigated plots of Produra wheat grown at Phoenix, Arizona, in the spring of 1976. These data were used to evaluate a newly developed plant water stress index each day from the initiation of heading to the commencement of senescence. Daily measurements on total plant water potential were also obtained over this period; and after demonstrating how the atmospheric-induced component can be removed from these data, the resultant soil-induced component was plotted as a function of the new water stress index. The result was a simple linear relationship, which was found to be identical to one previously derived for alfalfa. Finally, it was shown that grain yield was directly related to the mean plant water stress index over the reproductive growth period from heading to senescence.Contribution from Agricultural Research, Science and Education Administration, US Department of AgricultureResearch physicist, soil scientist, research physicist, and research entomologist, respectively     

Plasma alpha-fetoprotein concentrations in pregnant cows exposed to Sarcocystis cruzi, Campylobacter fetus, or Aspergillus fumigatus

Bovine alpha-fetoprotein (AFP) was determined in maternal plasma, using radioimmunoassay in an attempt to detect and monitor fetal distress in pregnant cows. Plasma from pregnant cows in the 4th to 5th month of the gestation which had been exposed to Sarcocystis cruzi, Campylobacter fetus, or Aspergillus fumigatus was used. Plasma AFP concentrations were determined at intervals from before the cows were exposed until they had aborted or calved. The plasma AFP concentration of the exposed pregnant cattle remained at 6.5 +/- 5.0 mg/ml until 24 to 48 hours before abortion or parturition, when the value increased to 25.0 +/- 8.0 ng/ml. This pattern was similar for cattle exposed to each of the infective agents. Unlike in persons, rats, or monkeys, fetal-maternal transfer of AFP seems to be minimal in cows even with inflammation or necrosis of the placentome, Thus, changes in AFP concentrations in bovine plasma cannot be used as a diagnostic tool for fetal distress or fetal death.     

A stress transformation approach to predicting the failure mode of wood

Summary A simple model, based on the use of transformations of second-order tensors, is presented in this paper to predict the failure mode of wood members stressed in various degrees of parallel-and perpendicular-to-grain tension and parallel-to-grain shear. This type of loading is indicative of structural wood members with cross grain or grain deviations in the vicinity of knots subjected to bending or tension. The model is based on the assumptions that failure is dictated by the presence of any of the aforementioned stresses that exceed the clear wood strength in that mode and that failure does not result from stress interactions. The magnitudes of the applied stresses are normalized relative to the wood strength in that mode. The ratio of applied stress to material strength that is greatest at any particular angle of load to grain is presumed to be the failure mode at that angle. To verify model predictions, optical and microscopic analyses of surfaces of failed specimens loaded in uniaxial tension at angles between 0° and 90° to grain were compared to previously obtained, or otherwise known, surfaces of specimens tested in tension and shear. Specimens tested at various angles to grain demonstrated failed surfaces very much like those associated with specimens loaded in the modes predicted by the model.