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  • 1
    Digitale Medien
    Digitale Medien
    Radiolytic Yields of the Hydrated Electron from Transient Conductivity. Improved Calculation of the Hydrated Electron Diffusion Coefficient and Analysis of Some Diffusion-Limited (e-)aq Reaction Rates (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 10530-10539 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100026a016
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  • 2
    Digitale Medien
    Digitale Medien
    Long range order in 2-D arrays of nanometer-sized Fe islands on CaF2/Si(111) (invited) (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5056-5056 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The effective magnetic moment was measured as a function of Fe island size during the initial stages of Fe growth on CaF2/Si(111) in an ultrahigh vacuum scanning electron microscope equipped with an in situ SMOKE analysis chamber. This substrate was selected for its wide bandgap, chemical inertness, viability of integration into an Si based technology and the availability of nanopatterning using electron beams for producing devices. Fe grown at room temperature initially nucleates into a monodisperse distribution of 3-D islands at very high nucleation densities (8×1012/cm2). Increased Fe coverages lead to 2-D island growth. A room temperature superparamagnetic to ferromagnetic phase transition occurs as a function of Fe island radius. Mean field and Monte Carlo calculations illustrate that three distinct magnetic phases exist as a function of island diameter. Ferromagnetic order is present at room temperature when r(approximately-greater-than)3 nm, superparamagnetism is favored when 2 nm 〈 r 〈3 nm, and a frustrated random antiferromagnetic phase exists when r〈2 nm. Further depositions of Ag on superparamagnetic Fe island arrays produce Ag islands which couple the covered Fe island moments in-plane, implying that the Ag mediates the magnetic exchange between individual Fe islands within an Ag island. Implications for 2-D giant magnetoresistance devices will be discussed. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.361570
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  • 3
    Digitale Medien
    Digitale Medien
    Enhanced superparamagnetism in two-dimensional arrays of nanometer-sized Fe islands (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2878-2880 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Iron grown on room-temperature CaF2/Si(111) substrates form two-dimensional arrays of nanometer-sized superparamagnetic islands. Deposition of Ag on the Fe/CaF2/Si(111) produced a superparamagnetic response where the effective moment was proportional to the number of Fe islands covered by an average-sized Ag island. The nonmagnetic Ag overlayer mediates a long-range exchange between neighboring Fe islands within an individual Ag island. Monte Carlo methods are used to examine ordering in two dimensions and to set minimum interisland coupling strengths. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.114815
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  • 4
    Digitale Medien
    Digitale Medien
    Size distribution of coherently strained InAs quantum dots (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 4268-4272 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The influence of the InAs coverage on the size and density of coherently strained InAs islands was investigated. At moderate InAs coverages the photoluminescence signal reflects the Gaussian size distribution of small coherently strained islands. However, before the coherently strained islands transform into dislocated ones the Gaussian line shape of their photoluminescence signal changes and a narrow peak appears on the low-energy tail. We attribute this change to an accumulation of coherently strained islands at a maximum size before dislocated island transformation occurs. Effects of luminescence from dislocated islands, size-dependent relaxation processes, capture efficiencies, and dot-dot coupling are also discussed. However, our calculations and the magnetophotoluminescence, as well as the photovoltage experiments, confirm our interpretation of a size accumulation process of coherently strained islands. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.368644
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  • 5
    Digitale Medien
    Digitale Medien
    Size quantization effects in InAs self-assembled quantum dots (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1727-1729 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We study size quantization effects in InAs self-assembled quantum dots (QDs) that are embedded in GaAs. Using capacitance, photoluminescence and photovoltage spectroscopy, we correlate the measured quantized level energies with the quantum dot sizes and densities obtained from transmission electron microscopy. With increasing dot size, we observe a strong redshift of the QD features in all our data. In the capacitance spectra, a band gap renormalization of the two-dimensional wetting layer system appears when the first excited QD state crosses the wetting layer ground state. The relative size dependence and absolute energetic position of the QD transitions determined with photoluminescence provide some information about the influence of lateral confinement and height of the QD. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.118682
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  • 6
    Digitale Medien
    Digitale Medien
    Size distribution of Ge islands grown on Si(001) (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 410-412 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Atomic force microscopy analyses were performed on Ge islands on Si(001) grown by low pressure chemical vapor deposition in the temperature range from 525 to 700 °C. A comparison with theoretical models describing the growth of coherently strained and plastically relaxed islands is given to describe the observations. The mean diameter of coherently strained islands is found to be 170 nm over a wide range of temperature, whereas plastically relaxed islands grow up to diameters 〉500 nm. The aspect ratio turns out to be independent of the presence of dislocations. For the sample grown at 700 °C three size regimes could be observed, whereas the sample grown at the lowest temperature exhibits no island formation. At 550 °C islands with an average diameter of 33 nm and a low aspect ratio were observed; these could prove to be interesting in applications using quantum confinement effects. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.119553
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  • 7
    Digitale Medien
    Digitale Medien
    Determination of the activation energy for the heterogeneous nucleation of misfit dislocations in Si1−xGex/Si deposited by selective epitaxy (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 324-326 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Si0.84Ge0.16/Si heterostructures with variable finite lateral dimensions (10–300 μm) and different layer thicknesses grown by selective low pressure chemical vapor deposition epitaxy at a temperature of 700 °C were investigated with regard to relaxation by formation of misfit dislocations. While in small structures only nucleation and propagation occur, the dislocation–dislocation interaction (mainly multiplication) becomes more and more important in larger structures. Therefore it was possible to separate the three different mechanisms which play a role in relaxation, i.e., nucleation, propagation, and multiplication, and to study them independently. From the analysis of the misfit dislocations at the initial stage of relaxation it was possible to determine the nucleation site density and an activation energy of 2.8 eV for the heterogeneous nucleation of misfit dislocations. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.118404
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  • 8
    Digitale Medien
    Digitale Medien
    Intermixing and shape changes during the formation of InAs self-assembled quantum dots (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2014-2016 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The initial stages of GaAs overgrowth over self-assembled coherently strained InAs quantum dots (QDs) are studied. For small GaAs coverages (below 5 nm), atomic force microscopy (AFM) images show partially covered island structures with a regular size distribution which are elongated in the [011] direction. Analysis of the AFM profiles show that a large anisotropic redistribution of the island material is taking place during the initial GaAs overgrowth. Short time annealing experiments together with photoluminescence spectroscopy on annealed QDs are consistent with a Ga and In intermixing during the overgrowth. Surface QDs capped with 5 nm or more GaAs show a strong luminescence intensity indicating that surface QDs are remarkably insensitive to surface recombination effects. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.119772
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  • 9
    Digitale Medien
    Digitale Medien
    Exopolysaccharide production from whey lactose by fermentation with Lactobacillus delbrueckii ssp. bulgaricus (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 62 (1997), S. 0 
    Details
    ISSN: 1750-3841
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Ropy Lactobacillus delbrueckii ssp. bulgaricus (strain RR) was used for production of exopolysaccharide in sweet whey and simulated whey permeate (SWP) supplemented with combinations of lactose, KH2PO4, NH4Cl, casamino acids, and mineral salts. Media were incubated at 32, 37, and 44°C for 72h. Periodic adjustment of pH to ∼6.2 increased viscosity and lactose utilization, and the free galactose and lactic acid in the media. The effect of pH adjustment was greater than that of supplementation with nutrients or minerals. Fermentation of supplemented SWP generally produced lower viscosities than did fermentation of supplemented sweet whey. After 24h fermentation, viscosity decreased in pH adjusted media. Viscosity of media was highest when incubation was at 32°C and lowest with incubation at 44°C.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2621.1997.tb04393.x
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  • 10
    Digitale Medien
    Digitale Medien
    Release of nitric oxide from donors with known half-life: a mathematical model for calculating nitric oxide concentrations in aerobic solutions (1997)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 355 (1997), S. 457-462 
    Details
    ISSN: 1432-1912
    Schlagwort(e): Key words Nitric oxide donor ; Release of nitric oxide ; Concentration-time profile ; Mathematical modeling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The NO concentrations released from donor compounds are difficult to predict as they are determined by formation and inactivation reactions. To calculate the concentrations of NO over time, we have developed a mathematical model which is based on a system of two differential equations describing the first order decomposition of the NO donor in association with the third order reaction of NO with oxygen. Although there is no closed formula for the solution, it can be easily computed by any standard numerical differential solver or simulation software with the following input parameters: initial concentration and decomposition rate constant of the NO donor, O2 concentration, and rate constant for NO autoxidation. The model was validated by monitoring NO release from 2,2-diethyl-1-nitroso-oxyhydrazine (DEA/NO) with a Clark-type NO-sensitive electrode at two different temperatures (25 and 37°C) and DEA/NO concentrations ranging from 1 to 10μM. Under all conditions, there was an excellent agreement between experimental and calculated data. In addition to the computer modeling, we present graphical plots which allow a rough but very easy estimation of the actual NO concentrations if appropriate computer software should not be available.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00004969
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