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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of the green fraction of humic acids (1996)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of soil science 47 (1996), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The green fraction of humic acids (HAs), Pg, was fractionated by gel chromatography on Sephadex G-50. Repeated chromatography of the crude Pg obtained by the first chromatography of HA yielded a sharp peak (G1) and two broad bands (G2) of purified Pg. The recovery of Pg in G1 and G2 as percentages of the total Pg content of the HA were 16.2 and 14.5%, respectively. Distinct peaks were detected at 615, 570, 450 and 280 nm in the UV-visible spectra of both G1 and G2 in alkali solutions. Estimates of weight-average molecular weight were 9.7 * 103 for G1 and 1.23 * 104 for G2. In the 1H-NMR spectra the percentage of hydroxyl groups of 4,9-dihydroxy-perylene-3, 10-quinone (DHPQ) nuclei, which are known to be the chromophore of Pg, was 4.1 and 4.5% of the total H, respectively. Based on these values and the H/C ratios, DHPQ-C was estimated as 28% of total C. 13C-NMR spectra obtained using inverse-gated decoupling yielded 40–41% aromatic C, which suggested the presence of aromatic rings other than DHPQ. All of the IR, 13C- and 1H-NMR spectra indicated that the two purified Pg samples largely differed from each other in their contents of alkyl and polysaccharide components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.1996.tb01390.x
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  • 2
    Electronic Resource
    Electronic Resource
    Nitridation process of sapphire substrate surface and its effect on the growth of GaN (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3487-3491 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nitridated layer formed on a (0001) sapphire (α-Al2O3) substrate surface by heating at 1050 °C in ammonia (NH3) gas was analyzed by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), transmission electron microscope (TEM) and energy dispersive x-ray spectrometry (EDX). Their influence on the growth of GaN in the combined usage of initial nitridation and successive deposition of a buffer layer was examined by AFM observations. The intensity of the N1s nitrogen peak in the XPS rapidly increased with nitridation time, reaching saturation in a few minutes, and then continued to increase gradually. This change was found to correspond to morphological change revealed by AFM observations, that is, from a flat nitridated layer to high-density (109–1010 cm−2) nitridated protrusions. TEM observations and EDX measurements showed that the nitridation forms an amorphous layer consisting of AlNxO1−x. The flat nitridated layer, when combined with a buffer layer, favors two-dimensional growth of a thick GaN layer on it, while the layer with protrusions results in three-dimensional growth. Thus, thick GaN layers with smooth surfaces can be grown by controlling the surface of the nitridated layer, where a crystal-amorphous-crystal growth mechanism is successfully operating. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361398
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  • 3
    Electronic Resource
    Electronic Resource
    Erratum: "Nitridation process of sapphirre substrate surface and its effect on the growth of GaN'' [J. Appl. Phys. 79, 3487 (1996)] (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1942-1943 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363832
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  • 4
    Electronic Resource
    Electronic Resource
    Real-time observation of molecular beam epitaxy growth on mesa-etched GaAs substrates by scanning microprobe reflection high-energy electron diffraction (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2542-2544 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microscopic distribution of growth rates on mesa-etched GaAs(001) wafers was measured in real time during molecular beam epitaxy growth by scanning microprobe reflection high-energy electron diffraction. It has been observed that the growth rate on the GaAs(001) surface near the edge of (111)A surfaces becomes larger. The exponential variation of the growth rate as a function of the distance from the edge reflects surface diffusion of Ga atoms. The diffusion length on the (001) surface is estimated to be about 1 μm at 560 °C. The relatively larger diffusion length suggests that the incorporation rate of migrating Ga atoms by steps is much smaller than unity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102881
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  • 5
    Electronic Resource
    Electronic Resource
    High-power operation of 830-nm AlGaAs laser diodes (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2907-2911 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a high-power, semicylindrical-shaped waveguide inner stripe laser diode (SCILD) using a current confinement structure. The structure is optimized for high-power operation without catastrophic optical damage (COD) which limits the maximum available optical power. We confirm that the optical electric field shape in the LD waveguide layer obtained from our analysis coincides with the micrograph of the COD on the device facet. The SCILD is emitted in the fundamental transverse mode up to 190 mW. The full beam angles between the half-power points were 10° and 30° in the directions parallel and perpendicular to the junction plane, respectively. The characteristic temperature of the threshold current was 152 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342737
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  • 6
    Electronic Resource
    Electronic Resource
    p-type conduction in Mg-doped GaN and Al0.08Ga0.92N grown by metalorganic vapor phase epitaxy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 593-594 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature dependences of the hole concentration and Hall mobility in Mg-doped GaN and Al0.08Ga0.92N grown by metalorganic vapor phase epitaxy were measured by the van der Pauw method over a wide temperature range from 100 to 500 K. Assuming that the effective mass of holes in Al0.08Ga0.92N is equal to that of GaN, the activation energy of the Mg shallow acceptor in Al0.08Ga0.92N is estimated to be about 35 meV deeper than that in GaN.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112309
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  • 7
    Electronic Resource
    Electronic Resource
    Auger electron spectroscopy of molecular beam epitaxially grown GaAs surfaces exposed to trimethylgallium (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2248-2250 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In situ Auger electron spectroscopy is employed to study the dynamics of the desorption process of carbon and its related species from clean molecular beam epitaxially grown GaAs surfaces exposed to trimethylgallium under the conditions where atomic layer epitaxy takes place by metalorganic molecular beam epitaxy. The direct real time spectroscopic observation of the surfaces by Auger electron spectroscopy shows that, after exposure to trimethylgallium, the initial carbon signal intensity exponentially decreases with an activation energy of 1.3 eV and reaches a steady state level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109635
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  • 8
    Electronic Resource
    Electronic Resource
    Palladium(0)-catalyzed reaction of .alpha.,.beta.-epoxy ketones leading to .beta.-diketones (1980)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 102 (1980), S. 2095-2096 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00526a059
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  • 9
    Electronic Resource
    Electronic Resource
    Millimeter wave amplification in a free electron laser with a focusing wiggler (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 36-42 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A mm wave amplifier experiment on a free electron laser was performed using an intense, mildly relativistic electron beam (0.7–0.9 MeV) with a combination of a focusing planar wiggler and a weak additional axial magnetic field in the so-called "group 1'' region. A beam transport ratio of over 80%, through the whole wiggler length, was realized. In an amplification experiment, a spatial growth rate of 56 dB/m was obtained at a frequency of 45 GHz, and a power saturation was observed at a level of 6 MW, where the total gain was estimated to be 52 dB. It was shown that the off-axis component of the beam contributes considerably to the rf amplification in the focusing wiggler.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355861
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  • 10
    Electronic Resource
    Electronic Resource
    Humus composition of soils under forest, coffee and arable cultivation in hilly areas of south Sumatra, Indonesia (2001)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 52 (2001), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: To understand the effect of land use changes on the composition of humus in tropical soils, samples from land under primary forest, secondary forest, coffee plantation, and arable crops were investigated at three sites in south Sumatra, Indonesia. Total carbon and total nitrogen contents were 1.7 to 4.3 times and 1.1 to 2.8 times greater in the topsoil under primary forest than under the other types of land use. Following change from primary forest to other uses, the proportion of humic acids in the organic matter of the topsoils decreased while that of the fulvic acid fraction increased. Within the range of land uses, differences in the yields of humic acids and fulvic acid fractions were, respectively, larger and smaller than those in total carbon content. The humic acids were classified into the low and middle classes in the degree of humification. Absorption due to the green fraction of humic acids, Pg, was detected in the UV-visible spectra of almost all the humic acids. No relation was observed between the degree of humification of humic acids or the strength of Pg absorption in their spectra and land use change. The fulvic acid fractions were fractionated on insoluble polyvinylpyrrolidone (PVP) into the adsorbed fractions consisting of humic substances and the non-adsorbed fractions consisting of non-humic substances. A positive correlation between the amount of the fulvic acid fraction and the percentage of the PVP-adsorbed fraction within it indicated that the variation in the amount of the fulvic acid fraction was attributable to acid-soluble humic substances. The ionization difference spectra of solutions between pH 12 and pH 7 suggested that the chemical structures of the PVP-adsorbed fulvic acids have been altered by land use change.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.2001.00410.x
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