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  • 1
    ISSN: 1476-5535
    Keywords: Keywords: bacteriocin; Bacillus thuringiensis; tochicin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bacillus thuringiensis subsp tochigiensis HD868 was identified as a bacteriocin producer which exhibited a bactericidal effect against closely related species. This bacteriocin designated as tochicin, was partially purified by 75% ammonium sulfate precipitation followed by subsequent dialysis. This partially purified tochicin showed a narrow antibacterial spectrum of activity against most of 20 typical B. thuringiensis strains and a strain of B. cereus, but not against other bacteria and yeasts tested. The antibacterial activity of tochicin on sensitive indicator cells disappeared completely by proteinase K treatment (1 mg ml−1), which indicates its proteinaceous nature. Tochicin was very stable throughout the range of pH 3.0–9.0 and was relatively heat-stable at 90°C, but bacteriocin activity was not detected after boiling for 30 min. The relationship between cell growth and bacteriocin production was studied in a semi-defined medium. Tochicin activity was detected at the mid-log growth phase, reached the maximum at the early stationary phase, but decreased after the stationary phase. Direct detection of tochicin activity on sodium dodecyl sulfate-polyacrylamide gel suggested it has an apparent molecular mass of about 10.5 kDa. Tochicin exhibited a bactericidal activity against B. thuringiensis subsp thompsoni HD522 in phosphate buffer (pH 7.0).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a systematic study of the dependence of the optical nonlinearities on quantum well thickness for GaAs/AlGaAs multiple quantum wells (MQW's) at room temperature and compare them with bulk GaAs. The maximum change in the refractive index is greatest for the MQW's with the smallest well size and decreases with increasing well size, reaching a minimum for bulk GaAs. The maximum index change per photoexcited carrier increases by a factor of 3 as the well size decreases from bulk to 76 A(ring) MQW.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 2082-2085 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature-dependent photoluminescence (PL) measurements in Mg-doped GaN epitaxial layers grown on sapphire substrates by plasma-assisted molecular beam epitaxy have been performed in order to investigate the process of donor–acceptor pair (DAP) recombination. The PL intensity of the DAP peak decreases below 35 K, and then it increases as the temperature increases in the temperature range between 35 and 100 K. This behavior originates from the interaction between two different Mg-related traps, one shallow and the other deep level. The ionization energies of the shallow trap and the deep level trap determined from the calculations and the PL experiments are 126 and 160 meV, respectively. The DAP recombination process suggests that holes are caught in the shallow trap and that they subsequently transfer, via a tunneling process, from the shallow trap to the deep trap, where recombination with electrons takes place. © 1998 American Institute of Physics.
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  • 4
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaN epilayers grown by molecular beam epitaxy were photoelectrochemically (PEC) oxidized in an aqueous KOH solution. The oxidation effect was investigated by defect-related photoconductivity and photoluminescence. The PEC treated GaN show decreased extrinsic photoresponse and concentration of deep level states in comparison with the as-grown sample. The PEC process also results in enhanced donor-bound exciton photoluminescence at 3.47 eV and restrained 3.4 eV band. No strain is detected in the PEC oxidized GaN. The 3.4 eV band is related to structural defects instead of oxygen impurities. Rather, the defects can be passivated by the PEC oxidation. © 2001 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 977-979 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of perovskite manganite La0.7Ca0.3MnO3 were grown epitaxially on SrTiO3(100), MgO(100) and LaAlO3(100) substrates by the pulsed laser deposition method. Microscopic structures of these thin film samples as well as a bulk sample were fully determined by x-ray diffraction measurements. The unit cells of the three films have different shapes, i.e., contracted tetragonal, cubic, and elongated tetragonal for SrTiO3, MgO, and LaAlO3, respectively, while the unit cell of the bulk is cubic. It is found that the samples with a cubic unit cell show smaller peak magnetoresistance at low fields ((approximately-less-than)1 T) than the noncubic ones do. The present result demonstrates that the magnetoresistance of La0.7Ca0.3MnO3 at low fields can be controlled by lattice distortion via externally imposed strains. © 1997 American Institute of Physics.
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  • 6
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Large optical nonlinearities have been observed in molecular beam epitaxially grown thin films of ZnSe at room temperature and at T=150 K. A comparison with a plasma theory indicates that in both cases exciton screening is the dominating mechanism for the nonlinearity. The maximum nonlinear index per excited electron-hole pair at room temperature is comparable to that of bulk GaAs and GaAs-AlGaAs multiple quantum wells. The measured absorption and nonlinear index spectra agree quite well with our calculated values.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 8041-8045 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear optical properties of CdSe quantum dots are investigated using self-saturation and degenerate four-wave mixing techniques. The saturation of the room temperature absorption coefficient, for a wavelength in the vicinity of the first exciton peak, is measured. The measured data can be predicted from a description of the quantum dot as a two level, homogeneously broadened, saturating system. The variation of the four-wave mixing reflectivity with intensity and with wavelength is reported. All four-wave mixing data are also consistent with the homogeneously-broadened two-level model.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 279-281 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated a band gap shrinkage in both lattice-matched and compressive strained GaInAs/GaInAsP/InP multi-quantum well lasers. The band gap shrinkage is obtained from the broadening of the low energy side in the spectrum by considering effects of an intraband scattering and a fundamental band edge. It amounts to 20–25 meV at sheet carrier densities of above 1012 cm−2, and shows n1/1.3 dependence at low carrier densities and n1/3 dependence at higher densities. These dependencies agree well with theoretical predictions in the quantum well.
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  • 9
    ISSN: 1435-232X
    Keywords: Key words Bone mineral density ; FokI ; DNA polymorphism ; Vitamin D receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We undertook this study in order to examine the association between bone mineral density (BMD) and a polymorphism at the first of two potential translation initiation codons in the vitamin D receptor (VDR) gene. This polymorphism was detected by restriction fragment length polymorphism analysis, using polymerase chain reaction (PCR) and the restriction endonuclease FokI. The f allele indicates the presence of the FokI site, and the F allele its absence. The FokI genotype was determined in 174 postmenopausal Korean women, aged 43–71 years. The distribution of FokI genotypes in Koreans was found not to differ significantly from those found in Caucasians and Japanese, although it does differ significantly from that found in the black American population. We observed a significant association between the FokI polymorphism and lumbar BMD; P = 0.048, analysis of covariance [ANCOVA], but no association with femoral neck BMD (P = 0.505, ANCOVA). Those with the ff genotype had a 13.3% lower BMD in the lumbar spine than the FF subjects. In addition, a significantly higher prevalence of the ff genotype was observed in osteoporotic compared with osteopenic or normal women (P = 0.036, χ2 test). These data suggest that the ff genotype of the VDR gene correlates with decreased BMD in the lumbar spine in postmenopausal Korean women.
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  • 10
    ISSN: 1439-6327
    Keywords: Power ; Performance ; Endurance runners
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of this study was to assess the relationship between anaerobic ability and middle distance running performance. Ten runners of similar performance capacities (5 km times: 16.72, SE 0.2 min) were examined during 4 weeks of controlled training. The runners performed a battery of tests each week [maximum oxygen consumption (VO2max), vertical jump, and Margaria power run] and raced 5 km three times (weeks 1, 2, 4) on an indoor 200-m track (all subjects competing). Regression analysis revealed that the combination of time to exhaustion (TTE) during theVO2max test (r 2=0.63) and measures from the Margaria power test (W·kg−1,r 2=0.18 ; W,r 2=0.05) accounted for 86% of the total variance in race times (P〈0.05). Regression analysis demonstrated that TTE was influenced by both anaerobic ability [vertical jump, power (W·kg−1) and aerobic capacity (VO2max, ml·kg−1·min−1)]. These results indicate that the anaerobic systems influence middle distance performance in runners of similar abilities.
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