Dielectrophoretic alignment of gallium nitride nanowires (GaN NWs) for use in device applications.

We report on a simple and effective ac and dc dielectrophoresis (DEP) method that can be used to align and manipulate semiconductor gallium nitride (GaN) nanowires (NWs) with variations in the type of electrical fields as well as variations of frequency. We observed that the ability of the alignment and the formation of the assembling nanowires (single or a bundle configuration) strongly depend on the magnitude of both the ac and dc electric fields. The yield results indicate that the GaN NWs, using ac DEP, are better aligned with a higher yield rate of approximately 80% over the entire array in the chip than by using dc DEP. In addition, we first demonstrated the simple hybrid p-n junction structures assembled by n-type GaN nanowires together with a p-type silicon substrate (n-GaN NW/p-Si substrate) using dielectrophoresis. From the transport measurements, the p-n junction structures show well-defined current rectifying behaviour with a low reverse leakage current of approximately 3 x 10(-4) A at -25 V. We believe that our unique p-n junction structures can be useful for electronic and optoelectronic nanodevices such as rectifiers and UV nano-LEDs.

Single-Crystalline Diluted Magnetic Semiconductor GaN:Mn Nanowires.

Single-crystalline diluted magnetic semiconductor GaN:Mn nanowires with controlled Mn concentrations have been successfully synthesized and incorporated into devices. These nanowires exhibit Curie temperatures above room temperature, magnetoresistances near room temperature, and spin-dependent transport. The nanowires are used as building blocks for the fabrication of GaN:Mn/n-SiC based light-emitting diodes.

Occurrence of coagulase serotype among Staphylococcus aureus strains isolated from healthy individuals--special reference to correlation with size of protein-A gene--.

One-hundred-and-nineteen strains of Staphylococcus aureus isolated from healthy individuals for 3 years between 1991 and 1993 were subjected to an investigation on the producibility of proteins including protein A, coagulase, enterotoxins and toxic-shock syndrome toxin-1. Especially, protein A was the center of our interest. Among these strains, 69, 43, 3 and 1 strains were found to have the protein-A gene containing 5, 4, 3 and 2 IgG-binding domains, respectively. On the other hand, only one strain was devoid of the protein-A gene. There were some differences in the profile of the coagulase serotype between the group with 4 IgG-binding domains and that with 5 IgG-binding domains. Differences in the profile of toxin production were also observed between the two groups.

Auxiliary method for clonal identification of Staphylococcus aureus by protein band pattern of released proteins on SDS-polyacrylamide gel.

A supportive method for clonal identification of Staphylococcus aureus strains was devised. Culture supernatant obtained by cellophane surface culture was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) without performing any concentration procedure prior to electrophoresis. The combined use of cellophane surface culture and SDS-PAGE was convenient for determining whether the strains belonged to the same clone or not when conducted in conjunction with other tests for bacteriological characterization.

Biochemical and genetic heterogeneity of staphylococcal protein A.

We investigated the biochemical and genetic heterogeneity of protein A from Staphylococcus aureus. SpA genes (spas) of various strains were heterogeneous when detected as DraI and EcoRV fragments of chromosomal DNA. Polymerase chain reaction using primers to detect DNA encoding the IgG-binding domains in spa revealed that they numbered between 2 and 5. Protein A from several S. aureus strains showed two types of reactivities to immunoglobulins in normal canine serum according to the number of active domains.