In-situ TEM observations of abnormal grain growth, coarsening, and substrate de-wetting in nanocrystalline Ag thin films

Abnormal grain growth is studied in nanocrystalline sputtered Ag films. Eighty nanometer thick Ag films are DC sputter deposited onto back-etched amorphous silicon nitride membranes. Specimens are annealed in a heating stage in an in-situ TEM for various temperatures and hold times. With the same specimen, we proceed to higher temperatures after the apparent halt of growth for sufficiently long hold times. The grain size distribution of the as-deposited films is bi-modal, with large abnormal grains with 100 nm diameters, embedded in a matrix of smaller grains of 15 nm diameters. Coarsening begins at temperatures of approximately 100°C, and quickly reaches a plateau. The growth process restarts only after sufficient temperature increases, and plateaus at each succeeding temperature. Using a variation of the Mullins–Von Neumann law, the activation energy for the abnormal growth is found to be 0.274 eV, consistent with the value reported for pore formation during electromigration via surface diffusion in Ag. Grain growth appears to stop above temperatures of 350°C, eventually leading to triple junction pore formation at 350°C and de-wetting of the film from the substrate at 600°C. The de-wetting is the high temperature limit of the thermal grooving which cancels the driving force for grain growth at the lower temperatures. TEM images as evidence of this effect are presented, along with observations on the pore formation that support surface diffusion as the mass transport mechanism for grooving, pore fomation, and as the limiting mass transport mechanism for the grain growth.     

Enhanced cyclooxygenase-2 gene expression in alcoholic liver disease in the rat

BACKGROUND & AIMS: Inflammatory stimuli and lipid peroxidation up-regulate cyclooxygenase (COX)-2. This study evaluated the relationship between inflammatory mediators, COX expression, and pathological changes in experimental alcoholic liver disease. METHODS: Rats (5 per group) were fed ethanol and a diet containing saturated fat, corn oil, or fish oil by intragastric infusion. Dextrose isocalorically replaced ethanol in controls. In the first set of experiments, whole livers were analyzed. In the second set of experiments, Kupffer cells, endothelial cells, and hepatocytes were isolated from rats in each group. Pathological analyses and measurements of lipid peroxidation, tumor necrosis factor (TNF)-alpha, COX-1 and COX-2 messenger RNA (mRNA), endotoxin, and liver and plasma thromboxane were performed. RESULTS: Increased expression of COX-2 mRNA was detected in the livers of rats showing necroinflammatory changes. The Kupffer cell was the cell primarily responsible for the increase in COX-2 mRNA level. Increased expression of COX-2 was associated with increased levels of endotoxin, TNF-alpha mRNA, lipid peroxidation, and synthesis of thromboxane. COX-1 mRNA was decreased in Kupffer cells in rats with the most severe liver injury. CONCLUSIONS: Up-regulation of COX-2 in alcoholic liver injury occurred in the presence of proinflammatory stimuli and resulted in increased synthesis of inflammatory and vasoactive eicosanoids. Down-regulation of COX-1 may result in decreased synthesis of cytoprotective eicosanoids and additionally exacerbate liver injury.     

Optimization of Settling Behavior for an Efficient Solvent‐Extraction Process for Biobased Components

Extraction is a downstream process option in biobased processes. Because knowledge of phase‐separation behavior is essential for designing efficient separation processes, this study investigates the settling and coalescence behavior of biobased extraction systems by using a standard laboratory‐scale settling cell. The influence of different buffer media and Escherichia coli cells on coalescence was determined for the reactive extraction of hexane‐1,6‐diamine with isostearic acid and di(2‐ethylhexyl)phosphoric acid by using kerosene and oleyl alcohol as diluents. As a result, an increasing pH value of the buffer significantly increases the settling time. The presence of E. coli cells hinders phase separation of the investigated systems, in particular, with dispersed organic phases.     

Compact Quantum-Dot Microbeads with Sub-Nanometer Emission Linewidth

Fluorescent microbeads are widely used for applications in life sciences and medical diagnosis. The spectral contrast and sharpness of photoluminescence are critical in the utilities of microbeads for imaging and multiplexing. Here, microbeads capable of generating single-peak laser emission with a sub-nanometer linewidth are demonstrated. The microbeads are made of quantum dots that are tightly packed and crosslinked via ligand exchange for high optical gain and refractive index as well as material stability. Bright single-mode lasing with no photobleaching is achieved with particle diameters as small as 1.5 µm in the air. Sub-nm lasing emission is maintained even inside high-index surroundings, such as organic solvents and biological tissues. Feasibility of intracellular tagging and multi-color imaging in vivo is demonstrated.     

Comparative effects of omeprazole on xenobiotic metabolizing enzymes in the rat and human

Omeprazole induces CYP1A in the human liver and gut, which has led to concern about possible side effects. The purpose of this study was to compare the effects of omeprazole on phase 1 and phase 2 enzymes in the rat and human. Male rats were treated with intraperitoneal (40 or 80 mg/kg) or oral omeprazole (40 mg/kg) for 5 or 14 days, respectively. The activities and amounts of CYP1A, uridine diphosphate-glucuronosyltransferase, and glutathione transferase were determined in liver and gut. Enzyme activities were also determined in duodenal biopsy specimens from six healthy human volunteers before and after treatment with omeprazole (20 mg/day) for 10 days. Treatment with intraperitoneal omeprazole (40 mg/kg; 80 mg/kg) coinduced uridine diphosphate-glucuronosyltransferase (36%; 66%), glutathione transferase (22%; 50%), and CYP1A (26%; 50%) in rat liver. In rat small intestine, comparable levels of induction were observed for uridine diphosphate-glucuronosyltransferase and glutathione transferase; CYP1A was unaffected. Oral omeprazole had similar effects. Immunoblotting showed corresponding changes in the amounts of these enzymes. Omeprazole increased the activities of CYP1A (19% to 167%; p = 0.014) and uridine diphosphate-glucuronosyltransferase (11% to 68%; p = 0.04) in the duodenal biopsy specimens of all six human volunteers; glutathione transferase was unaffected. Thus, omeprazole coinduced multiple xenobiotic metabolizing enzymes in the rat and human. The pattern of induction differed in the rat and human, consistent with known differences in genetic regulatory elements in the two species.     

Kinetics and regioselectivity of the Autoxidation of o-Substituted Isopropyl Aromatics

The relative chain propagation constants and the regioselectivities of the oxidations of o-cymene and 2-isopropyl-1,4-dimethylbenzene were determined by competitive oxidations of the hydrocarbons with cumene. As expected, the reactivity of the tertiary C H bond of the isopropyl group is considerably decreased by o-methyl groups. Also in α-isopropylnaphthalene a considerable decrease in the reactivity of the tertiary C H bond takes place. The decrease of the chain propagation constants effects a decrease of the oxidabilities of o-substituted isopropyl aromatics. In the case of the methyl isopropyl benzenes the increase of the chain termination constants by primary peroxy radicals must also be taken into consideration. This results in a decrease of the oxidabilities which can be observed even in p-cymene (in comparison with cumene).