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  • 1
    Electronic Resource
    Electronic Resource
    Negative surface ionization of hydrogen atoms and molecules (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2896-2901 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The total yield of H− ions, Y(Ein), produced in backscattering of low-energy H+ and H+2 ions from polycrystalline gold, tungsten, and molybdenum converter surfaces was measured at normal incidence in the energy range Ein=2–30 eV per nucleus. The yield per nucleus is independent of the ion mass. This indicates that the molecular ions are dissociated before colliding with the converter surface. A universal expression for Y(Ein) was developed by combining the electron tunneling theory with atomic scattering theory. This expression agrees well with measurements. The yield is completely characterized by two parameters, Eth/RE and RNη0, which can be determined experimentally: Y=0 for Ein=Eth/RE, and Y approaches the maximum yield Rη0 as Ein increases. These parameters were determined from measured H− yields in ion beam backscattering experiments, as well as for backscattering of thermal distributions of hydrogen atoms. For beam experiments, the maximum yield of 0.3 per nucleus was obtained for Mo/Cs converters with 1.5 eV work function. A higher maximum yield of 0.42 was obtained from experiments on backscattering thermal distributions of H atoms. This is attributed to high extraction fields. The universal yield formula made it possible to compare the results of the two different types of experiments. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361285
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  • 2
    Electronic Resource
    Electronic Resource
    The microwave absorbing and resonance phenomena of Y-type hexagonal ferrite microwave absorbers : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6109-6111 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microwave absorbing characteristics and resonance of Y-type hexagonal ferrite–rubber composites were investigated. The complex permeability and permittivity of Ni2−xZnxY ferrite bodies were measured using a network analyzer in the frequency range of 200 MHz–14 GHz. Two types of resonance, the domain wall and the spin rotational resonance, were observed. With a ferrite particle with a diameter of about 1 μm, only spin rotational resonance was observed. The first matching frequency, found in the ferrite–rubber composites, which was higher than that of spin rotational resonance, increased with spin rotational resonance frequency. It was also found that domain wall resonance had no effects on the microwave absorbing characteristics. Based on these findings, it could be concluded that the microwave absorbing characteristics were caused by only one type of resonance, the spin rotational resonance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355476
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  • 3
    Electronic Resource
    Electronic Resource
    Source of low-energy hydrogen ions for measuring electron transfer in surface scattering experiments (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 5289-5293 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present the design and performance of a beamline which is the source of 5–50-eV protons for surface scattering experiments. The beamline also incorporates a collector for measuring total secondary ion and electron yields. The beam forming optics are built around a commercially available gas discharge ion gun and produce a mass-selected, energy-filtered beam. Results of computer ray tracing are included to illustrate the operation of the beam optics. Tests have produced 50-pA proton beams 3.5-mm wide at 5 eV with an energy spread of about 1 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143441
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic quantum oscillation of Hg"1"-"x"-"yCd"xMn"yTe in the open-gap range grown by LPE
    Amsterdam : Elsevier
    Physica B: Physics of Condensed Matter 184 (1993), S. 445-450 
    Details
    ISSN: 0921-4526
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0921-4526(93)90395-M
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  • 5
    Electronic Resource
    Electronic Resource
    Enhanced biosynthesis of clavulanic acid in Streptomyces clavuligerus due to oxidative challenge by redox-cycling agents (1998)
    Springer
    Applied microbiology and biotechnology 49 (1998), S. 77-83 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Streptomyces clavuligerus produces a clinically important β-lactamase inhibitor, clavulanic acid. When several of the selected redox-cycling agents were treated, an increase in clavulanate production was observed. The stimulatory effect was seen when the reaction was fed with menadione, plumbagin and phenazine methosulfate (PMS), whereas feeding with methyl viologen had a negative effect. PMS exerted the strongest effect, enhancing the accumulation of clavulanic acid by 150%. Induction of superoxide dismutase upon the addition of PMS suggested an involvement of superoxide in the enhancing process. The stimulatory effect of PMS was offset by the addition of butylated hydroxyanisole, further supporting the involvement of the active oxygen. The enhanced production of clavulanic acid correlated well with the increased total activity of clavaminic acid synthase, a key enzyme in its biosynthesis, and the transcription of cas2, its coding gene. The results suggested that active oxygen species could enhance the biosynthesis of secondary metabolites through the transcriptional activation of the biosynthetic gene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051140
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular basis for enhanced biosynthesis of clavulanic acid by a redox-cycling agent, phenazine methosulfate, in Streptomyces clavuligerus (1999)
    Springer
    Applied microbiology and biotechnology 53 (1999), S. 57-62 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Phenazine methosulfate (PMS), a generator of superoxide, evoked the transcription of cas2 and cefF, ultimately resulting in the enhanced biosyntheses of clavulanic acid (CA) and cephamycin C (CMC) in Streptomyces clavuligerus. The transcriptional activation of cas2 and cefF was accompanied with that of ccaR, a regulatory gene for biosyntheses of CA and CMC. PMS or H2O2 in cell-free extract exerted a positive regulation on in vitro protein phosphorylation. The PMS-mediated activation of protein phosphorylation was significantly offset by butylated hydroxyanisole, a radical scavenger. Staurosporine, a protein kinase inhibitor, was shown to have a negative effect on PMS-promoted CA accumulation. Therefore, it is suggestive that PMS-activated transcription of cas2 and cefF is mediated by protein phosphorylation and the expression of a pathway- specific transcriptional activator as found in other streptomycetes. These experimental results present an example of the functional relationship between oxidative stimuli and secondary metabolite production in streptomycetes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051614
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  • 7
    Electronic Resource
    Electronic Resource
    Fractional ac Josephson effect in p- and d-wave superconductors (2003)
    Springer
    The European physical journal 37 (2003), S. 349-361 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. For certain orientations of Josephson junctions between two p x -wave or two d-wave superconductors, the subgap Andreev bound states produce a $4\pi$ -periodic relation between the Josephson current I and the phase difference $\phi$ : $I\propto\sin(\phi/2)$ . Consequently, the ac Josephson current has the fractional frequency $eV/\hbar$ , where V is the dc voltage. In the tunneling limit, the Josephson current is proportional to the first power (not square) of the electron tunneling amplitude. Thus, the Josephson current between unconventional superconductors is carried by single electrons, rather than by Cooper pairs. The fractional ac Josephson effect can be observed experimentally by measuring frequency spectrum of microwave radiation from the junction. We also study junctions between singlet s-wave and triplet p x -wave, as well as between chiral $p_x\pm ip_y$ -wave superconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2004-00066-4
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  • 8
    Electronic Resource
    Electronic Resource
    Production of a novel transfructosylating enzyme from Bacillus macerans EG-6 (2000)
    Springer
    Bioprocess engineering 23 (2000), S. 11-16 
    Details
    ISSN: 0178-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A new bacterium producing a novel transfructosylating enzyme was isolated from soil and designated as Bacillus macerans EG-6. Various culture conditions for enzyme production were optimized in a flask culture. 1% (w/v) sucrose as a carbon source and a mixed nitrogen source (1% yeast extract, 1% polypeptone, and 0.5% ammonium chloride) gave the best enzyme production. Addition of phosphate and magnesium ion into the medium enhanced the enzyme yield. Optimum culture pH and temperature were 7.0 and 37 °C, respectively. Under optimal culture conditions, transfructosylating enzyme was rapidly produced in the early growth period, thereafter invertase activity was predominant as the culture proceeded. Using the culture filtrate, production of fructooligosaccharides from sucrose was preliminarily carried out. In a low sucrose concentration (200 g/l), transfructosylating activity competes with invertase activity in sucrose utilization. Subsequently, low fructooligosaccharide yield (20%) was achieved due to liberation of high amounts of glucose and fructose. The best oligosaccharide yield (43%) was achieved when 500 g/l sucrose was utilized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004499900078
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