Effective properties of cemented granular materials

An analytical model is developed to describe the effective elastic properties of a cemented granular material that is modeled as a random packing of identical spheres. The elastic moduli of grains may differ from those of cement. The effective bulk and shear moduli of the packing are calculated from geometrical parameters (the average number of contacts per sphere and porosity), and from the normal and tangential stiffnesses of a two-grain combination. The latter are found by solving the problems of normal and tangential deformation of two elastic spherical grains cemented at their contact. A thin cement layer is approximated by an elastic foundation, and the grain-cement interaction problems are reduced to linear integral equations. The solution reveals a peculiar distribution pattern of normal and shear stresses at the cemented grain contacts: the stresses are maximum at the center of the contact region when the cement is soft relative to the grain, and are maximum at the periphery of the contact region when the cement is stiff. Stress distribution shape gradually varies between these two extremes as the cement's stiffness increases. The solution shows that it is mainly the amount of cement that influences the effective elastic properties of cemented granular materials. The radius of the cement layer affects the stiffness of a granular assembly much more strongly than the stiffness of the cement does. This theoretical model is supported by experimental results.     

Effects of supplemental protein source on intraruminal fermentation, protein degradation, and amino acid absorption

Cannulated steers were used to determine the effects of supplemental soybean meal, heated soybean meal, fish meal, and a combination of fish meal, heated soybean meal, and corn gluten meal on intraruminal protein degradation and absorption of AA from the small intestine. Organic matter digestion in the reticulo-rumen was greater in steers fed diets supplemented with soybean meal, but whole tract digestibility was not affected by protein source. Total and bacterial CP flows to the abomasum were lower in steers fed diets supplemented with fish meal than in steers fed diets supplemented with heated soybean meal or the combination supplement. Dietary CP flow was 33.5% higher in steers fed diets supplemented with heated soybean meal than in steers fed diets supplemented with soybean meal, fish meal, or the combination supplement. Less essential and nonessential AA flowed to the abomasum and were absorbed from the small intestine of steers receiving diets supplemented with soybean meal. Digestibility of small intestine AA was 21.9% lower in steers receiving the soybean meal treatment. Abomasal flows of Met and Thr and absorption of Lys, Met, and Thr were increased in steers fed diets containing heated soybean meal, fish meal, and the combination supplement. These results suggest that the supply of AA deficient in microbial CP (Lys, Met, and Thr) can be increased and that absorbed AA balance can be changed markedly by selection of rumen escape protein supplements.     

Affect, generalization, and the perception of risk.

Investigated the role of affect in judgments of risk in 4 experiments. 557 Ss were recruited on college campuses and read paragraphs modeled after newspaper reports that described fatal or nonfatal accidents or (Exp III) positive events. Ss were later asked to estimate the chances of specific fatal or nonfatal accidents happening to them and/or to the population in general. Experimental manipulations of affect induced by report of a tragic event produced a pervasive increase in Ss' estimates of the frequency of many risks and other undesirable events. Contrary to expectation, the effect was independent of the similarity between the report and the estimated risk: An account of a fatal stabbing did not increase the frequency estimate of homicide more than the estimates of unrelated risks such as natural hazards. An account of a happy event that created positive affect produced a comparable global decrease in judged frequency of risks. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rapid evaluation of oxidation catalysts supported on activated carbon

Electron spin resonance and thermal analysis have been used to investigate the catalytic oxidation of organic vapors adsorbed on activated carbon. Particular attention is given to determination of the temperature interval between oxidation of the adsorbate and burnoff of the carbon, and to the study of the oxidation states of the catalyst during repeated adsorption-oxidation cycles.     

Attribution and alcohol-mediated aggression.

48 males participated in an aggression task after receiving either alcoholic or placebo beverages and after being told that they had received either a high or a low dose of alcohol. All Ss in the alcohol group actually received the same dose. Measures of aggression were the intensity and duration of shock given to a bogus partner in a RT-pain perception task and a score on a posttask attitude questionnaire. Blood alcohol readings were taken 3 times during the session, and a locus of control scale was administered before and after drinking. For Ss in the alcohol conditions, blood alcohol levels averaged .079% before the task and .085% afterwards. Alcohol resulted in higher aggression scores only on the questionnaire measure, and an interaction between drug and attribution was found for the measure of shock duration. Attribution alone resulted in greater aggression on the measure of shock intensity. Ss in groups where the attribution was discrepant with the drug condition were the most aggressive on the measures of shock intensity and duration. These Ss became more external, reflecting a high correlation between their aggression and a stimulus tone. Results suggest that a person's increased aggressiveness when intoxicated results from an interaction between alcohol and an altered responsivity to provoking stimuli. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tremorgenic Indole Alkaloids. 10. An Improved Asymmetric Synthesis of a Tricyclic Common Intermediate

An efficient third-generation asymmetric synthesis of tricyclic lactone (+)-1, designed to serve as the common intermediate for construction of the indole tremorgens, has been developed. The major challenge was stereocontrolled introduction of the vicinal quaternary methyl groups. Our initial approaches employed enolate chemistry to install the second methyl moiety; herein we exploit instead a hydroxyl-directed Simmons-Smith cyclopropanation followed by reductive opening of the three-membered ring. The new 15-step synthesis proceeds in 8.3% overall yield, nearly an eightfold increase over the second-generation route, and is amenable to large-scale production of (+)- 1.      

Low‐Cost Self‐Assembled Oxide Separator for Rechargeable Batteries

Rechargeable battery cells having a liquid electrolyte require a separator permeable to the electrolyte between the two electrodes. Because the electrodes change their volume during charge and discharge, the porous separators are flexible polymers with an electronic energy gap E_g large enough for the Fermi levels of the two electrodes to be within it. In this work, a porous film of self‐assembled SiO₂ nanoparticles is developed as the separator for a Li‐ion battery with a liquid electrolyte. This coating does not require the plasticity of a polymer membrane and has the required large E_g. If adsorbed water is removed from the SiO₂ surface, the nanoparticles bond to one another and to an oxide cathode to form a plastic self‐assembling porous layer into which the liquid electrolyte can penetrate. The Li‐ion batteries with a LiCoO₂ cathode coated with SiO₂ as a separator show similar performance to cells with a traditional polypropylene separator and improved cyclability with a reduced volume of liquid electrolyte owing to the electrolyte wetting properties of the SiO₂ nanoparticles. The SiO₂ nanoparticles are easy to prepare, cheap, and environmentally friendly.     

Ultrastructural features of bone marrow cells from patients with acquired sideroblastic anemia

The ultrastructural findings of the bone marrow cells from 15 patients with acquired sideroblastic anemia are presented. The red cell precursors from all patients showed the presence of electron-dense material in the mitochondria, representing most probably iron deposits. A great number of these mitochondria were completely destroyed. The erythropoietic precursors from one of the patients showed markedly elongated mitochondria that measured up to 3 microm. In addition numerous cytoplasmic vacuoles were observed. The red cell precursors from 60% of the patients showed signs of dyserythropoiesis, such as incomplete nuclear division and nuclear distortion. The polymorphonuclears from 47% of the patients presented nuclear abnormalities expressed as nuclear bridges, appendices, and blebs. In addition, phagocytosis of red blood cells was observed. The results of the study underline the advantages of the transmission electron microscope examination in visualization of intricate alterations in hematopoietic cells that cannot be detected with a light microscope.     

Brain‐Penetrant Triazolopyrimidine and Phenylpyrimidine Microtubule Stabilizers as Potential Leads to Treat Human African Trypanosomiasis

In vitro whole‐organism screens of Trypanosoma brucei with representative examples of brain‐penetrant microtubule (MT)‐stabilizing agents identified lethal triazolopyrimidines and phenylpyrimidines with sub‐micromolar potency. In mammalian cells, these antiproliferative compounds disrupt MT integrity and decrease total tubulin levels. Their parasiticidal potency, combined with their generally favorable pharmacokinetic properties, which include oral bioavailability and brain penetration, suggest that these compounds are potential leads against human African trypanosomiasis.