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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5639-5645 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Annealing processes of vacancy-type defects in 3 MeV electron-irradiated and as-grown 6H-SiC have been studied by positron lifetime spectroscopy. Vacancy-type defects giving rise to a positron lifetime of 183 ps were detected in as-grown n-type specimens. They were found to be annealed at around 1400 °C and were related to silicon vacancies, possibly complexes of silicon vacancies and nitrogen atoms. Defects related to carbon vacancies, silicon vacancies, and divacancies were found to be created by electron irradiation. The defects related to carbon vacancies and divacancies were found to be annealed up to 500 °C. The defects related to silicon vacancies were found to be annealed at around 750 and 1400 °C. The former annealing stage was inferred to be due to migration of silicon vacancies to internal sinks or nitrogen atoms to form complexes of silicon vacancies and nitrogen atoms. The latter annealing stage was explained as due to annihilations of the complexes as well as the case of as-grown specimens. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 837-842 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Photoluminescence (PL) has been used to study defects introduced by 1-MeV-electron irradiation in cubic silicon carbide (3C-SiC) films epitaxially grown on Si substrates by means of chemical vapor deposition. A dominant PL line of 1.913 eV observed in 3C-SiC irradiated with electrons was found to disappear at annealing stages of ≈100 and 700 °C. The annealing stages of the 1.913 eV PL center and its fraction annealed at each annealing stage were in good agreement with those obtained for the T1 electron spin resonance center, which is attributed to isolated vacancies at silicon sublattice sites [H. Itoh, M. Yoshikawa, I. Nashiyama, S. Misawa, H. Okumura, and S. Yoshida, IEEE Trans. Nucl. Sci. NS-37, 1732 (1990)]. This result indicates that the 1.913 eV PL line arises from silicon vacancies in 3C-SiC. The characteristics of other PL lines induced in 3C-SiC epilayers by irradiation are also discussed. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3861-3863 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A comparative study of electron cyclotron resonance (ECR) and radio frequency (rf) plasma as a nitrogen source for molecular-beam epitaxy GaN was carried out. The effects of differences in the excited nitrogen species on the optical signals during GaN growth were investigated by 77 K photoluminescence (PL). For epitaxial layers grown at optimum V/III ratio using ECR and rf plasma, the PL spectra were dominated by near band-edge emission at 3.47 eV. However, when the V/III ratio was less than the optimum V/III ratio, a broad emission band at about 3.2–3.3 eV was observed in the PL spectrum for the GaN epilayer grown using rf plasma, while in the case of growth using ECR plasma, a deep level emission at about 2.2 eV appeared. These characteristics in PL spectra can used to identify differences in the chemical species in the nitrogen plasma. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract A type II restriction endonuclease, named AaaI, was purified from Acetobacter aceti subsp. aceti No. 1023. The optimum pH and temperature were determined to be 8.5 and 37°C, respectively. The enzyme activity was stimulated by the addition of either NaCl or KCl and their optimum concentrations were 100 mM for both cations. AaaI recognized the hexanucleotide sequence and cleaved it at the positions indicated by the arrows. AaaI was an isoschizomer of XmaIII from Xanthomonas malvacaerum and Eco52I from Escherichia coli.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1432-0614
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary The acetic acid concentration in a batch culture of Acetobacter aceti M23 increased up to 90 g/l by adding ethanol intermittently. Although the bacterial cells ceased growth at about 60 g acetic acid/l, non-viable cells still preserved ethanol oxidation activity. Cell recycling by filtration in a repeated fed-batch culture increased the overall acetic acid production rate 2.84-fold compared to that without cell recycling for the purpose of obtaining an acetic acid concentration of 80.8 g/l. Repeated fed-batch cultivation with cell recycle was effective for increasing the production rate of acetic acid and obtaining high amounts close to a lethal concentration (90 g/l).
    Materialart: Digitale Medien
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  • 6
    ISSN: 1432-0614
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Membrane-bound alcohol dehydrogenase (ADH) was purified from the membrane fraction of an industrial-vinegar-producing strain, A. polyoxogenes sp. nov. NBI1028 by solubilization using Triton X-100 and subsequent column chromatography on DEAE-Sepharose CL-6B and hydroxyapatite. The purified enzyme was homogeneous on polyacrylamide disc gel electrophoresis (PAGE). Upon sodium dodecyl sulphate-PAGE, the enzyme showed the presence of two subunits with a molecular mass of 72 000 daltons and 44 000 daltons, respectively. The small subunit was identified as cytochrome c. In addition, absorption and fluorescence spectra showed the the presence of pyrroloquinoline quinone in the purified ADH. The ADH preferentially oxidized aliphatic alcohols with a straight carbon chain except for methanol. Formaldehyde and acetaldehyde were also oxidizable substrates. The apparent K m for ethanol was 1.2 mM. The optimum pH and temperature were 5.0–6.0 and 40°C, respectively. p-Chloromercuribenzoic acid and heavy metals such as CuSO4 were inhibitory to the enzyme activity. Ferricyanide was effective as an electron acceptor.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-0614
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Membrane-bound aldehyde dehydrogenase (ALDH) was purified from the membrane fraction of an industrial-vinegar-producing strain, Acetobacter polyoxogenes sp. nov. NBI1028 by solubilization with Triton X-100 and sodium N-lauroyl sarcosinate and subsequent column chromatography on DEAE-Sepharose CL-6B and hydroxyapatite. The purified enzyme was homogeneos on polyacrylamide disc gel electrophoresis. Upon sodium dodecyl sulphate-polyacrylamide gelelectrophoresis, the enzyme showed the presence of two subunits with a molecular mass of 75 000 daltons and 19 000 daltons, respectively. From the absorption and fluorescence spectra, the absence of cytochrome c and the presence of pyrroloquinoline quinone in the purified enzyme were demonstrated. The ALDH preferentially oxidized aliphatic aldehyde with a straight carbon chain except for formaldehyde. The apparent K m for acetaldehyde was 12 mM. The optimum pH and temperature were 7.0 and 50°–60°C, respectively. The enzyme remained active after storage at 4°C for 20 days. p-Chloromercuribenzoic acid and heavy metal salts such as CuSO4 were inhibitory to the enzyme. Ferricyanide was effective as an electron acceptor.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1432-0630
    Schlagwort(e): PACS: 61.70; 61.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 2 + and Al+ at temperatures from room temperature (RT) to 1200 °C at doses of 1013 and 1015/cm2. It is found from Doppler broadening spectra of annihilation gamma-rays obtained by varying the incident positron energy that hot-implantation gives rise to clustering of vacancies, whereas it suppresses amorphization and diminishes the thickness of damaged layers. The average size of such clusters increases with increasing implantation dose and temperature. Vacancy clustering by hot-implantation can be interpreted by the combination of vacancies during implantation. Vacancy type defects in the low-dose (1013/cm2) implanted samples are found to be removed by annealing at 1400 °C, whereas large vacancy clusters still remain after 1400 °C annealing in the high-dose (1 015/cm2) implanted samples. It is also derived from the depth profile of positron diffusion length that positron scattering centers are produced after annealing at 1400 °C in all implanted samples.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 918-923 
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The continuous production of acetic acid by Acetobacter aceti M23 was carried out using a fermentor equipped with a hollow fiber filter module. The culture continued for 830 h with various dilution rates, which were changed stepwisely from low to high. The final cell concentration was 21.9 g dry cell/L and the maximum productivity of acetic acid was 12.7 g/L·h for the exit acetic acid concentration of about 50 g/L. The productivity was higher than any literature's values surveyed so far. The cell concentration was 62.8 times and the productivity was 4.6 times as high as those of the fermentor without the filter module. The productivity increased with the increase of dilution rate up to 0.3 h-1. It is interesting to note that the viable cell concentration was kept almost constant about 1.1 × 109 cells/ml in spite of the increase of dilution rate. Use of oxygen-rich air was indispensable to establish the high productivity of acetic acid.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 10
    ISSN: 1573-6776
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary A comparison of volumetric production rates of acetic acid inAcetobacter aceti M23 was conducted for repeated batch (RB), cell-recycling repeated batch (CRB) and continuous (C) cultures. Best result was obtained with CRB culture. The magnification of productivity was 1.7 (to RB culture) and 3.3 (to C culture) for aiming final acetic acid concentration of 60 g/l and 42 g/l, respectively.
    Materialart: Digitale Medien
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