Spectroscopic Observation of He Arcjet Plasma Expanding Through a Converging and Diverging Slit Nozzle

An arcjet plasma generator with a converging and diverging slit nozzle was constructed. This plasma source allowed us to directly observe the arc plasma in the discharge section, which provided useful information about a transition from ionizing thermal plasma to recombining phase. Spatial distributions of the electron temperature and density in the rectangular shaped anode nozzle were evaluated by visible emission spectroscopy. The temperature and density for a discharge current of 20 A were determined to be 0.18 eV and 3.7×1013 cm-3, respectively, at the nozzle throat. The values on the jet axis were compared with those calculated by the gas dynamic theory on one dimensional slit nozzle

Isolation of an X-factor-dependent but porphyrin-positive Escherichia coli from urine of a patient with hemorrhagic cystitis

An Escherichia coli isolate was recovered from a 92-year-old female patient with urinary tract infection. Gram-stained preparation of the urine sediment manifested some gram-negative rod-shaped cells, and the urine specimen culture yielded nonhemolytic colonies on sheep blood agar plate. However, no visible colonies appeared on modified Drigalski agar plate. The isolate was finally identified as an X-factor-dependent E. coli. The interesting finding was that the isolate revealed a positive reaction for porphyrin test despite the requirement of hemin. This finding suggested that some pyrrol-ring-containing porphyrin compounds or fluorescent porphyrins had been produced as chemical intermediates in the synthetic pathway from delta-amino-levulinic acid (ALA), although the isolate should be devoid of synthesizing hems from ALA. This was the first clinical isolation of such a strain, indicating that the E. coli isolate should possess incomplete synthetic pathways of hems from ALA.ArticleJOURNAL OF INFECTION AND CHEMOTHERAPY. 19(4):764-766 (2013)journal articl

Emission spectroscopy of a microhollow cathode discharge plasma in helium-water gas mixtures

A dc microhollow cathode discharge (MHCD) plasma was generated inflowing helium gas containing water vapor. The cathode hole diameters were 0.3, 0.7, 1.0, and 2.0 mm, each with a length of 2.0 mm. Emission spectroscopy was carried out to investigate the discharge mode and to determine the plasma parameters. For the 0.3-mm cathode, stable MHCDs in an abnormal glow mode existed at pressures up to 100 kPa, whereas for larger diameters, a plasma was not generated at atmospheric pressure. An analysis of the lineshapes relevant to He at 667.8 nm and to Hα at 656.3 nm implied an electron density and gas temperature of 2 × 1014 cm-3 and 1100 K, respectively, for a 100-kPa discharge in the negative glow region. The dependence of the OH band, and Hα intensities on the discharge current exhibited different behaviors. Specifically, the OH spectrum had a maximum intensity at a certain current, while the H atom intensity kept increasing with the discharge current. This observation implies that a high concentration of OH radicals results in quenching, leading to the production of H atoms via the reaction OH + e- → O + H + e-

Isolation and Molecular Characterization of Catalase-Negative Staphylococcus aureus from Sputum of a Patient with Aspiration Pneumonia

Staphylococcus aureus produces various virulence factors. The catalase enzyme, in particular, is considered to be involved in oxidative stress resistance, and catalase activity is an important criterion for differentiating staphylococci from streptococci. In this report, we describe the catalase-negative S. aureus strain SH3064, which was isolated from the sputum of a patient with aspiration pneumonia. To evaluate the causes of the lack of catalase activity in S. aureus SH3064, we analyzed the sequence of katA gene encoding the catalase enzyme in this strain. We amplified the complete sequence of katA gene of S. aureus SH3064 by polymerase chain reaction using 2 sets of primers. The katA sequence showed 99.6% sequence identity (1512/1518 bp) with that of S. aureus ATCC 12600. We detected 2 mutations in the katA gene from S. aureus SH3064, an A217T substitution leading to a threonine 73-to-serine substitution and a single-base pair deletion (c.637delG) resulting in a frameshift mutation. The lack of catalase activity in this strain was attributed to the shift of the nucleotide reading frame.ArticleJAPANESE JOURNAL OF INFECTIOUS DISEASES. 65(5):439-441 (2012)journal articl

Spatially Resolved Spectroscopic Study of Arcjet Helium Plasma Expanding through a Rectangular Converging and Diverging Nozzle

An arcjet discharge device with a rectangular converging and diverging nozzle was developed, which allowed us to optically observe high-density plasma inside the anode nozzle Spectroscopic observation along the plasma expansion axis was carried out to examine the characteristics of the arc plasma inside the nozzle Analyzing intense continuum and line emission spectra, we successfully obtained spatial variations in electron temperature and density. Moreover, we found that two-dimensional optical measurement is highly useful in visualizing the transition from atmospheric thermal plasma to a strongly nonequilibrium recombining plasma due to adiabatic expansion

Isolation and Molecular Characterization of Catalase-Negative Staphylococcus aureus from Sputum of a Patient with Aspiration Pneumonia

Staphylococcus aureus produces various virulence factors. The catalase enzyme, in particular, is considered to be involved in oxidative stress resistance, and catalase activity is an important criterion for differentiating staphylococci from streptococci. In this report, we describe the catalase-negative S. aureus strain SH3064, which was isolated from the sputum of a patient with aspiration pneumonia. To evaluate the causes of the lack of catalase activity in S. aureus SH3064, we analyzed the sequence of katA gene encoding the catalase enzyme in this strain. We amplified the complete sequence of katA gene of S. aureus SH3064 by polymerase chain reaction using 2 sets of primers. The katA sequence showed 99.6% sequence identity (1512/1518 bp) with that of S. aureus ATCC 12600. We detected 2 mutations in the katA gene from S. aureus SH3064, an A217T substitution leading to a threonine 73-to-serine substitution and a single-base pair deletion (c.637delG) resulting in a frameshift mutation. The lack of catalase activity in this strain was attributed to the shift of the nucleotide reading frame.ArticleJAPANESE JOURNAL OF INFECTIOUS DISEASES. 65(5):439-441 (2012)journal articl

Characterization of CIA-1, an Ambler Class A Extended-Spectrum β-Lactamase from Chryseobacterium indologenes

An Ambler class A β-lactamase gene, blaCIA-1, was cloned from the reference strain Chryseobacterium indologenes ATCC 29897 and expressed in Escherichia coli BL21. The blaCIA-1 gene encodes a novel extended-spectrum β-lactamase (ESBL) that shared 68% and 60% identities with the CGA-1 and CME-1 β-lactamases, respectively. blaCIA-1-like genes were detected from clinical isolates. In addition to the metallo-β-lactamase IND of Ambler class B, C. indologenes has a class A ESBL gene, blaCIA-1, located on the chromosome