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  • 1
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Zusammenfassung Styrol-Acrylnitril-Mischpolymer-Latices wurden unter Verwendung von Wasserstoffperoxyd als Initiator von Emulsionspolymerisation hergestellt. Verteilungen der Partikelgrößen wurden durch !Messen des Teilchen-Durchmessers auf Elektronenmikrographien bestimmt. Die chemische Zusammensetzung der Latex-Teilchen wurde durch Elementar-Analyse festgestellt. Stabilität und elektrophoretische Beweglichkeit dieser Latex-Dispersionen gegen einfache inorganische Elektrolytlösungen wurden untersucht. Der Wert der kritischen Koagulationskonzentration nahm mit abnehmendem Anteil von Acrylnitril in den Polymer-Partikeln zu. Der Wert desStern Potentials war unabhängig von der chemischen Zusammensetzung der Polymere. Der Unterschied in der Stabilität scheint vorwiegend auf den Unterschied der Anziehungsenergie zwischen Partikeln zurückgeführt werden zu können, d. h. dieHamaker Konstante nimmt beinahe geradewegs mit der Zunahme des Gehaltes von Acrylnitril im Mischpolymer zu.
    Notes: Summary Styrene-acrylonitrile copolymer latex dispersions were prepared using hydrogen peroxide as an initiator by emulsion polymerization. Particle size distributions were determined by measuring the diameter of particles on electron micrographs. The chemical composition of the latex particles was determined by elemental analysis. The stability and electrophoretic behaviour of these latex dispersions against simple inorganic electrolyte has been investigated. The value of the critical coagulation concentration was found to increase with the decrease of the fraction of acrylonitrile in the polymer particles. The value ofStern potential calculated was found to be independent on the chemical composition of polymers. The difference present in the latex stability seems to be mainly due to the difference in the attractive energy between particles, i.e., theHamaker constant increases almost linearly with the increase of the content of acrelonitrile in the copolymer.
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2255-2257 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nanometer-sized Si dot multilayers have been prepared by repeating a sequence of low-pressure chemical vapor deposition for dot formation and thermal oxidation for dot isolation. For the multilayer with Si dots in the range of 3–5 nm, the onset of photoconductivity is observable at a photon energy of 2 eV, corresponding to the optical absorption edge of the Si dots. This result indicates that the nanometer-sized Si dot multilayers are promising as photoconductors that work at various wavelengths because the optical band gap can be varied by controlling the dot size. © 2001 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3126-3128 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogenation effects on the structural relaxation and defect evolution in amorphous silicon (a-Si) prepared by ion implantation and evaporation have been investigated using Raman scattering spectroscopy and positron lifetime measurements. Bond angle deviation Δθ in nonhydrogenated a-Si was significantly reduced due to 300 °C annealing in atomic hydrogen atmosphere. This indicates that the reduction in Δθ of hydrogenated amorphous silicon (a-Si:H) is not only due to relaxation during the deposition process of a-Si:H films as proposed by Jackson et al. [Philos. Mag. B 64, 611 (1991)] but also due to posthydrogenation of nonhydrogenated a-Si. It was also found that agglomeration of vacancy-type defects in evaporated a-Si during 450 °C annealing is enhanced after posthydrogenation, while no remarkable enhancement can be seen in a-Si prepared by ion implantation. © 1996 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 1378-1380 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultralong pulse ((approximately-greater-than)40 μs) fluorescence of ArF excimer molecules at 193 nm has been generated by dynamically mixing a pulse discharge excited He jet with neutral Ar/F2 gas located downstream in a vacuum chamber. Rapid cooling of the high temperature He plasma through neutral gas collisions and efficient energy transfer to Ar gas create Ar metastable atoms, which form ArF excimer molecules through harpoon reactions with F2, in relatively field-free space. The fluorescence intensity increased with increasing F2 concentration up to ∼10% F2 in Ar with 2-atm backing pressure. In a preliminary experiment with an ArF probe laser, this mixture showed an amplification gain.
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 115-116 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: AlGaAs layers with a featureless specular surface morphology were grown successfully on an exactly (111)B oriented GaAs substrate by migration-enhanced epitaxy (MEE) even at growth temperatures below 500 °C. We have also observed reflection high-energy electron diffraction (RHEED) intensity oscillation of AlGaAs on a (111)B oriented substrate by MEE. The single quantum well (SQW) is prepared by MEE on a (111)B and a (100) substrate simultaneously, and the photoluminescence intensity from (111) SQW is shown to be about 50 times higher than that from (100) SQW.
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1388-1390 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A short-period (AlGaAs)m(GaAs)n superlattice has been applied to the barrier layers in a single and a multiple quantum well structure prepared by molecular beam epitaxy in order to improve the interface quality. With a 38 A(ring) thin GaAs quantum well without employing aluminum, a low threshold current density of 260 A/cm2, a high characteristic temperature (T0) of 205 K, and a high differential quantum efficiency of 75% have been achieved in a double quantum well ridge waveguide laser diode emitting at 780 nm.
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  • 7
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Localization of carbonic anhydrase activity was studied electron microscopically on cells of the rat choroid plexus epithelium. For the ultracytochemical detection of these activities, Yokota's technique (1969), which is the modification of Hansson's method (1967) was employed. Numerous electron dense reaction products were observed in the microvilli of the choroidal epithelial cell. The reaction deposits were also remarkably present in the infoldings of the basal plasmalemma but to a lesser extent than in the microvilli. The localization sites were mainly on the plasma membrane, but some reaction products were also observed in the cytoplasm near the plasma membrane. Hardly any reaction product was found in the intracellular organelles except for the mitochondria in which reaction products were occasionally observed on the cristae. These activities were completely inhibited by acetazolamide. As the carbonic anhydrase activity was histochemically seen in the microvilli and the basal infoldings, it is likely that carbonic anhydrase is related to an active transport process in the secretion of cerebrospinal fluid as is Na+, K+-ATPase (Masuzawa et al. 1980).
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  • 8
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Electron microscopic cytochemical studies on the rat choroid plexus epithelium have revealed enzymatic sites for the activities of acid phosphatase, glucose-6-phosphatase and thiamine pyrophosphatase on different organelles. Only the activity of acid phosphatase has been previously described. Acid phosphatase, glucose-6-phosphatase and thiamine pyrophosphatase were respectively situated mainly in the lysosomes, in the endoplasmic reticulum and nuclear envelope, and in the Golgi complex. These three enzymes can thus be considered as marker enzymes for their respective organelles in the choroid plexus epithelial cells as well as in other tissue cells. The possible function of these enzymes in the choroid plexus epithelial cells is also briefly discussed.
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  • 9
    ISSN: 1432-203X
    Keywords: Key words Callus ; ERF (EREBP) ; Osmotin-like protein ; Root ; Tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The constitutive accumulation of tobacco neutral PR-5 (osmotin-like protein; OLP, PR-5d) in roots and cultured cells was studied in transgenic tobacco plants harboring the OLP promoter::GUS gene. This construct showed strong β-glucuronidase expression in vascular tissues and cortex of roots as well as in cultured cells. Analysis using a mutated promoter showed that ethylene-responsive elements (AGCCGCC) were necessary for constitutive expression in roots and cultured cells. An electrophoretic mobility shift assay indicated that ERF3 (EREBP3), an ethylene-responsive-element-binding factor that was reported to be expressed in roots and in cultured cells as well as in ethephon-treated leaves, could bind to the AGCCGCC sequences of the OLP gene. These findings suggest that AGCCGCC sequences and ERFs mediate the constitutive expression of the OLP gene in roots and cultured cells of tobacco.
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  • 10
    ISSN: 1432-203X
    Keywords: Key wordsAgrobacterium rhizogenes ; β-Glucuronidase ; Hairy root ; Lithospermum erythrorhizon ; Stable transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seedling hypocotyls of Lithospermum erythrorhizon were infected with Agrobacterium rhizogenes (strain 15834) harboring a binary vector with an intron-bearing the β-glucuronidase (GUS) gene driven by cauliflower mosaic virus (CaMV) 35S promoter as well as the hygromycin phosphotransferase (HPT) gene as the selection marker. About 20% of the hairy roots isolated were hygromycin resistant and had co-integrated GUS and HPT genes in their Lithospermum genomic DNA. Because GUS activity was detected in almost all the hygromycin-resistant root tissues, the CaMV 35S promoter seems to be ubiquitously active in L. erythrorhizon hairy roots. In pigment production medium M9, the hairy root cultures had shikonin productivity similar to that of cell suspension cultures of Lithospermum. They also showed light-dependent inhibition of shikonin biosynthesis similar to that of Lithospermum cell cultures. These findings suggest that this hairy root system transformable with A. rhizogenes is a suitable model system for molecular characterization of shikonin biosynthesis via reverse genetics.
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