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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5018-5020 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermally activated magnetization reversal processes become manifest in the dependence of the remanent coercivity on the time during which a magnetic field is applied opposite to the initial magnetization direction. They have important consequences for the long term stability and short time writeability of future high density recording media. In this paper, we report on a new experiment using a contact write/read tester to study the time dependence of the remanent coercivity over more than 10 orders of magnitude (from 6 ns to 〉60 s). Remanence coercivity and signal decay measurements of a CoPtCr recording medium with 5.5 nm thickness are presented. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 3625-3640 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article describes the design of a versatile ultrahigh vaccum (UHV) low temperature scanning force microscope system. The system allows scanning probe microscopy measurements at temperatures between 6 and 400 K and in magnetic fields up to 7 T. Cantilevers and samples can be prepared in UHV and transferred to the microscope. We describe some technical details of our system and present first measurements performed at different temperatures and in various scanning force microscopy operation modes. We demonstrate distortion free and calibrated images at temperatures ranging from 8 to 300 K, atomic resolution on NaCl at 7.6 K and various magnetic force microscopy images of vortices in high transition temperature superconductors. It is demonstrated that our instrumentation reaches the thermodynamically determined sensitivity limit. Using standard cantilevers force gradients in the 10−6N/m range, corresponding forces of about 10−15N can be measured. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a series of magnetic force microscope (MFM) images of epitaxial magnetic thin films. The films studied, Ni/Cu/Si(001) capped by 2 nm of Cu, exhibit perpendicular anisotropy over an exceptionally broad thickness range, 2 nm〈h〈14 nm. The magnetic domain structure of the as-grown films shows a sharp transition to a finer length scale above a finite critical thickness of 12 nm. Micromagnetic theory provides the first quantitative description for these general but previously unexplained phenomena. Further we discuss MFM data obtained on films with a thickness larger than 14 nm. These films show a pronounced in-plane anisotropy. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6489-6490 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the characteristics of model magnetic media using different strategies for the "anisotropy design." We modeled media with intragrain anisotropy oriented random in the plane of the media, random in 3D, and aligned along the track direction, and for a large range of anisotropy field Hk and intergranular exchange J. We report a possible scaling function which collapses data for all three geometries onto a single universal curve. The rescaled data were then analyzed along with the signal-and-noise functions from the various model materials. For any geometry, we find a relation between exchange and anisotropy which maximizes the signal-to-(media) noise function. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 5609-5620 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a transfer-function approach to calculate the force on a magnetic force microscope tip and the stray field due to a perpendicularly magnetized medium having an arbitrary magnetization pattern. Under certain conditions, it is possible to calculate the magnetization pattern from the measured force data. We apply this transfer function theory to quantitatively simulate magnetic force microscopy data acquired on a CoNi/Pt multilayer and on an epitaxially grown Cu/Ni/Cu/Si(001) magnetic thin film. The method described here serves as an excellent basis for (i) the definition of the condition for achieving maximum resolution in a specific experiment, (ii) the differences of force and force z-derivative imaging, (iii) the artificial distinction between domain and domain wall contrast, and finally (iv) the influence of various tip shapes on image content. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1604-1606 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermal processes may limit the lifetime of stored data and ultimately the achievable areal density in magnetic recording. To quantify this important problem, we have studied a series of state-of-the-art thin film CoPtCr longitudinal recording media samples with thicknesses ranging between 5.5 and 13 nm. Static write/read tester experiments are used to measure the remanent coercivity of these films as a function of the applied magnetic field pulse width, which is varied in the range of nanoseconds to seconds. The data are analyzed in terms of an inverse slope parameter, 1/C, which in the framework of a Neel-Arrhenius model is equivalent to the familiar stability ratio EB/kBT. This ratio is then correlated with signal decay measurements, performed over a time range after writing of 2.8 s to (approximate)1 day. Both measurements are carried out at variable temperatures, T, between 300 and 390 K. The onset of strong signal decay in low density square wave bit patterns occurs when 1/C drops below about 36. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 804 (1996), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1435-1463
    Keywords: Parkinson's disease ; salsolinol ; hallucinations ; dopamine metabolites ; 5-hydroxyindole acetic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We could quantify the tetrahydroisoquinoline derivative salsolinol in urine of patients with Parkinson's disease and normal control subjects by means of high performance liquid chromatography and electrochemical detection. Urine levels of salsolinol were positively related to the homovanillic acid/3-O-methyl-dopa ratio in the cerebrospinal fluid that reflects dopamine metabolism. In the patient group with visual hallucinations, mean salsolinol level was significantly increased to almost the 3-fold of those found in patients without hallucinations. Since the daily L-dopa doses of both patient groups were nearly identical this result is not due to different L-dopa medications. Additionally, either high values of the main serotonin metabolite, 5-hydroxyindole acetic acid (HIAA) or the L-dopa/3-O-methyl-dopa ratio were found in cerebrospinal fluid of patients with hallucinations. The enhanced salsolinol levels in patients with visual hallucinations seem to be due to an overloaded dopaminergic pathway with an imbalance between dopaminergic and serotonergic systems. Thus, salsolinol appears as a predictor for hallucinosis in Parkinson's disease.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Bioprocess and biosystems engineering 12 (1995), S. 173-179 
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Biotechnological processes call for an overall process optimization. One of the major possibilities of optimizing biotechnological processes lies in immobilization technologies, which may increase productivities and product concentrations. This paper gives a systematic approach to the various immobilization techniques reported in literature. The most important levels of influence on overall process performance are considered within a classification system by three criteria: Substrates and products flow pattern criterion, catalyst criterion and apparatus criterion. Some important immobilization systems are discussed, and the classification system is applied to these examples.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Bioprocess and biosystems engineering 13 (1995), S. 97-103 
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The mechanical characteristics of a new type of ejector are presented and discussed in view of its application as an aeration device for bioreactors. The experiments performed with two geometrically similar sizes allowed to do a systematic scale comparison setting forth the main scale-up criteria. Excellent performances are revealed from the investigation of pressure drops and gas entrainment rates. A perfect consistency of the two scales is obtained, even in case of gas entrainment. Using a reference velocity, empirical relationships are deduced allowing to predict the performances for any size of ejector. The dependence of the gas entrainment capacity on the backpressure is shown to be ruled out by the extremely low values of the specific aspiration energy of the ejector, and the use of a pressurized gas is only of interest in case of high backpressures. Experimental evidence is provided for the intensity of contact between the gas and liquid phases inside the ejector.
    Type of Medium: Electronic Resource
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