Czochralski-growth of germanium crystals containing high concentrations of oxygen impurities

Oxygen-containing germanium (Ge) single crystals with low density of grown-in dislocations were grown by the Czochralski (CZ) technique from a Ge melt, both with and without a covering by boron oxide (B(2)O(3)) liquid. Interstitially dissolved oxygen concentrations in the crystals were determined by the absorption peak at 855 cm(-1) in the infrared absorption spectra at room temperature. It was found that oxygen concentration in a Ge crystal grown from melt partially or fully covered with B(2)O(3) liquid was about 10(16) cm(-3) and was almost the same as that in a Ge crystal grown without B(2)O(3). Oxygen concentration in a Ge crystal was enhanced to be greater than 10(17) cm(-3) by growing a crystal from a melt fully covered with B(2)O(3); with the addition of germanium oxide powder, the maximum oxygen concentration achieved was 5.5 x 10(17) cm(-3). The effective segregation coefficients of oxygen in the present Ge crystal growth were roughly estimated to be between 1.0 and 1.4.ArticleJOURNAL OF CRYSTAL GROWTH. 312(19):2783-2787 (2010)journal articl

18th International Conference on Defects in Semiconductors

Proceedings of the 18th International Conference on Defects in Semiconductors (ICDS-18), Sendai, Japan, July 1995

<i>Pseudomonas aeruginosa serA</i> Gene Is Required for Bacterial Translocation through Caco-2 Cell Monolayers

<div><p>To specify critical factors responsible for <i>Pseudomonas aeruginosa</i> penetration through the Caco-2 cell epithelial barrier, we analyzed transposon insertion mutants that demonstrated a dramatic reduction in penetration activity relative to <i>P</i>. <i>aeruginosa</i> PAO1 strain. From these strains, mutations could be grouped into five classes, specifically flagellin-associated genes, pili-associated genes, heat-shock protein genes, genes related to the glycolytic pathway, and biosynthesis-related genes. Of these mutants, we here focused on the <i>serA</i> mutant, as the association between this gene and penetration activity is yet unknown. Inactivation of the <i>serA</i> gene caused significant repression of bacterial penetration through Caco-2 cell monolayers with decreased swimming and swarming motilities, bacterial adherence, and fly mortality rate, as well as repression of ExoS secretion; however, twitching motility was not affected. Furthermore, _L-serine, which is known to inhibit the D-3-phosphoglycerate dehydrogenase activity of the SerA protein, caused significant reductions in penetration through Caco-2 cell monolayers, swarming and swimming motilities, bacterial adherence to Caco-2 cells, and virulence in flies in the wild-type <i>P</i>. <i>aeruginosa</i> PAO1 strain. Together, these results suggest that <i>serA</i> is associated with bacterial motility and adherence, which are mediated by flagella that play a key role in the penetration of <i>P</i>. <i>aeruginosa</i> through Caco-2 cell monolayers. Oral administration of _L-serine to compromised hosts might have the potential to interfere with bacterial translocation and prevent septicemia caused by <i>P</i>. <i>aeruginosa</i> through inhibition of <i>serA</i> function.</p></div

Influence of _L-serine addition on swarming motility in the wild-type strain.

<p>Swarming motility of the wild-type strain (WT), PAO1Tn::<i>serA</i> mutant (<i>ΔserA</i>), PAO1Tn::<i>flgE</i> mutant (<i>ΔflgE</i>) (as a negative control), and WT in the presence of _L-serine (20, 30, 40, and 50 mM). A representative image of the swarming motility assay is shown. The major axis of swarming is the longest length of the swarming area. The assay was performed in triplicate, and the results are expressed as the mean ± SD. Significant differences were observed between WT and <i>ΔserA</i> (*: P < 0.05), between WT and <i>ΔflgE</i> (*: P < 0.05), between WT and WT in the presence of 30 mM _L-serine (*: P < 0.05), between WT and WT in the presence of 40 mM _L-serine (*: P < 0.05), and between WT and WT in the presence of 50 mM _L-serine (*: P < 0.05).</p

PCR primers used in this study.

<p>PCR primers used in this study.</p