Grain growth of copper films prepared by chemical vapour deposition

Copper films having thickness 600 nm were prepared on TiN using chemical vapour deposition (CVD). The deposited films were annealed at various temperatures (350–550°C) in Ar and H₂(10%)-Ar ambients. The changes in the grain size of the films upon annealing were investigated. Annealing in an H₂(10%)-Ar ambient produced normal grain growth; annealing in an Ar ambient caused grain growth to stop at 550°C. The grain size followed a monomodal distribution and the mean size increased in proportion to the square root of the annealing time, indicating the curvature of the grain is the main driving force for grain growth. Upon annealing at 450°C for 30 min in an H₂(10%)-Ar ambient, the average grain size of the film increased from 122 nm to 219 nm, and the resistivity decreased from 2.35 μΩ cm to 2.12 μΩ cm at a film thickness of 600 nm. This revised version was published online in July 2006 with corrections to the Cover Date.     

High Performance Liquid Chromatography of 2,5-Dimethyl-4-Hydroxy-3 (2H)-Furanone in Pineapple and Grapefruit Juices

A reversed-phase HPLC method was developed for rapid analysis of 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF), the compound responsible for the “burnt-pineapple” flavor in pineapple juices. A Zorbax ODS column was used with a mobile phase of 0.05M sodium acetate (pH 4.0)/methanol (70:30); detection was by UV at 290 nm. Sample clean up was accomplished by solid-phase extraction with C-18 Sep-Pak cartridges. DMHF contents ranged from 1.6 to 27.3 ppm from 10 fresh pineapple juices. Using this system, the production of DMHF was monitored in canned grapefruit juices during storage at varying temperatures.     

PURIFICATION AND CHARACTERIZATION OF LIPOXYGENASE ISOZYMES FROM CANOLA (Brassica napus cv, WESTAR) SEED

Four isozymes, I', II'a, II'b and III’ of lipoxygenase (EC 1.13.11.12) from Canola (Brassica napus, cv Westar) seed were purified by successive chromatography on ion-exchange and size-exclusion columns using a Fast Protein Liquid Chromatograph (FPLC). The homogeneity of each isozyme was demonstrated by a single protein band on SDS-polyacrylamide gel electrophoresis. The molecular weights of isozymes I', II'a, II'b and III’ were 72, 000, 106, 000, 78, 000 and 62, 000, respectively. The optimum pH for lipoxygenase activity was 6.5 for isozyme I’ and 6.0 for isozymes II'b, II'b and III'. Apparent K_m value for isozymes I', II'a, II'b and III’ were 5.5 × 10^?4 M, 3.4 × 10^?4 M, 4.0 × 10^?4 M and 3.8 × 10^?4 M, respectively. Isozyme I’ displayed preferential activity towards monolinoleate and dilinoleate, while isozyme II'a demonstrated preferential activity towards dilinoleate followed by mono- and trilinoleate. No enzymatic activity was observed with both isozymes I’ and II'a toward free linoleic acid. Isozyme II'b showed activity towards free linoleate as well as mono-, di- and trilinoleate. Isozyme III’ showed preferential activity towards free linoleate. The activity of isozymes I’ and II'a was inhibited completely by the addition of 10 mM and 4 mM KCN, respectively, while the addition of 3 mM and 10 mM KCN to isozymes II'b and III', respectively, increased activity by approximately 20%.     

开闸式异重流前峰行进规律:数值求解

本文首先以数值方法求得开闸式异重流前峰行进规律。数值求解基于重在化群（ＲＮＧ）ｋ－ε湍流应力封闭模式，能合理反映异重流的过渡性局部湍流特征，结果与实验相符，表明开闸式湍动重流的前峰行进有两个阶段，先是坍塌段，峰速不变，后是自相似段，峰这随时间以－１／３次规律递减。     

EFFECT OF GROWTH TEMPERATURE AND MEDIA ON INACTIVATION OF LISTERIA MONOCYTOGENES BY CHLORINE

The objective of this study was to determine the effect of growth environment on the susceptibility of Listeria monocytogenes to inactivation by hypochlorite sanitizer. Cells were grown in tryptic soy broth (TSB) at 35, 21, and 6°C and in 1:15 dilution of TSB (low nutrient medium, LNM) at 35°C. Late exponential phase cells were harvested, washed, and exposed to a 1 ppm sodium hypochlorite solution for periods up to 5 min. After 30 s exposure, cells grown at 35°C in TSB were reduced in number by 2.1 ± .3, at 21°C, 3.1 ± .3 and at 6°C, 3.4 ± .3 log units. After 30 s exposure to 5 ppm free chlorine cells grown at 35°C in TSB were reduced in number by 5.2 ± .2 and in LNM by 3.1 ± .1 log units. These data demonstrate that growth environment has a significant effect on chlorine inactivation of L. monocytogenes.     

Assessment of Cheddar Cheese Quality by Chromatographic Analysis of Free Amino Acids and Biogenic Amines

The free amino acids and biogenic amines extracted from normal and late-gassing Cheddar cheeses were derivatized with heptafluorobutyric anhydride and trifluoroacetic anhydride, respectively, before quantification by gas-liquid chromatography. On a microgram scale, twenty amino acids were positively identified in both types of cheese, but only high levels of γ-amino acid butyrate (0.3 to 19.4 mg/g) and small quantities of arginate were found to be associated with “poorly aged” Cheddar cheeses. Histamine (1.54 and 1.22 mg/g) and tyramine (0.32 and 0.43 mg/g) were the bioamines present in highest concentrations in both cheeses.