Investigation of AlGaN/GaN Heterostructures Grown on Sputtered AlN Templates with Different Nucleation Layers.

In this work, a sputtered AlN template is employed to grow high-quality AlGaN/GaN heterostructures, and the effects of AlN nucleation layer growth conditions on the structural and electrical properties of heterostructures are investigated in detail. The optimal growth condition is obtained with composited AlN nucleation layers grown on a sputtered AlN template, resulting in the smooth surface morphology and superior transport properties of the heterostructures. Moreover, high crystal quality GaN material with low dislocation density has been achieved under the optimal condition. The dislocation propagation mechanism, stress relief effect in the GaN grown on sputtered AlN, and metal organic chemical vapor deposition AlN nucleation layers are revealed based on the test results. The results in this work demonstrate the great potential of AlGaN/GaN heterostructures grown on sputtered AlN and composited AlN nucleation layers for microelectronic applications.

Long-term effects of N-acyl-homoserine lactone-based quorum sensing on the characteristics of ANAMMOX granules in high-loaded reactors.

Laboratory experiments were carried out to determine the long-term effects of N-acyl-homoserine lactone (AHL)-based quorum sensing on the characteristics of ANAMMOX granules in high-loaded reactors. Results clearly showed that adding 30 mg L-1 N-octanoyl-DL-homoserinelactone (C8-HSL) at the initial stage (1-40 d) of the experiment had long-term positive effects on the settleability of granules and controlled the sludge floatation effectively. C8-HSL decreased the content of bound extracellular polymeric substances (B-EPS) and the ratio of protein to carbohydrate (PN/PS) by 17% and 48%, respectively and increased the relative hydrophobicity (RH) of the granules by 28%. The results of batch tests indicated that C8-HSL significantly reduced the content of loosely-bound EPS (LB-EPS) in the B-EPS, which was responsible for variations in granule settleability and stability. Thus, the settleability of the granules was improved significantly due to addition of C8-HSL, contributing to operational stability and the high TN removal efficiency of the reactor. On day 150, when the nitrogen loading rates of all reactors were 13.4 kg TN m-3 d-1, the nitrogen removal rate and nitrogen removal efficiency of the reactor with C8-HSL (R3) were up to 11.2 kg TN m-3 d-1 and 88%, respectively. N-hexanoyl-DL-homoserine lactone (C6-HSL) improved activity of the granules, while N-dodecanoyl-DL-homoserine lactone (C12-HSL) had no effect on the characteristics of the granules. The long-term effects of C8-HSL on the settleability of granules may be attributed to sustainable release of endogenous signals induced by exogenous signal.

[Influence of intestinal dysbacteriosis on immune and hematopoietec function in mice].

OBJECTIVE: To study the effects of intestinal microflora alteration on specific and nonspecific immune function and hematopoietic function of mice. METHODS: Sixty BALB/C mice were divided at random into two groups, experimental group and control group, with 30 mice in each. The mice in the experimental group were given kanamycin 50 mg while those in the control group were given distilled water intragastrically everyday for consecutive 10 days. After the 10 day treatment all the mice were sacrificed, and the cecal contents were collected for quantitative analysis of the intestinal bacterial flora. Certain indexes of immune function, including phagocytosis rate of macrophages, number of T lymphocytes positively stained by esterase and serum interleukin 2 (IL-2) content, and the weight of the spleen, granulocyte-macrophage colony stimulating factor etc. as indexes of hematopoietic function were determined. RESULTS: In the group, the quantity of Enterobacteriaceae, Enterococcus, Bifidobacterium and Lactobacillus were significantly lower than that in the control group (P < 0.01). The number of PFC (plaque forming cells), the phagocytosis rate of macrophage, the number of T lymphocytes with positive NANE staining, the level of IL-2 significantly decreased when compared with that in the control group (P < 0.01). The weight of the spleen in the experimental group decreased when compared with that in the control group (P < 0.01). Levels of IL-3, GM-CSF, the total number of WBC and the proportion of neutrophil remarkably decreased as compared to that in the control group (P < 0.01). Analysis of the correlations between normal microflora, immunologic and hematopoietic indexes showed that marked positive correlations between the quantity of Bifidobacteria and each immune index including the levels of IL-3 and GM-CSF. There was a positive correlation between IL-2 and IL-3, IL-2 and GM-CSF as well. CONCLUSION: The application of antibiotics may cause changes in the structure and quantity of intestinal microflora. The dysbacteriosis may decrease the immune function of organism. The dysbacteriosis may decrease the hemopoietic function. The dysbacteriosis, the decrease in immune and hematopoietic function may affect one another. The balance in microecosystem should be emphasized and antibiotics should be applied rationally to reduce the side effects such as dysbacteriosis.