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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cellular magnetic domain patterns in magnetic garnet films are an example of a spatially-extended metastable system whose evolution is limited by topological constraints. For sufficiently large applied magnetic fields, the entire pattern is under tension and can respond to local perturbations via large collective motions. In this regime disordered cellular patterns respond to small increases in applied field or to manual cell breakage via avalanches of sequential cell destruction which sweep through the pattern via the motion of cell walls. After one avalanche has stopped another can be started by a small increase in field or by another manual cell breakage; the system thus tends to self-organize into barely stable states. The measured distributions of avalanche size and duration are best fit by power laws. These features suggest that cellular avalanches may be an example of self-organized criticality.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4438-4440 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic force microscopy (MFM) has been shown to give high-resolution imaging of magnetic domain structures in a variety of high-coercivity permanent magnets [Folks et al., J. Magn. Magn. Mater. (in press)]. We show that this technique can be extended by the application of external fields during imaging, thus allowing direct observation of submicron microstructural evolution as a function of field. Electromagnets mounted on the MFM supplied fields up to 7 kOe laterally and 3 kOe vertically. In sintered materials, submicron processes such as depinning of domain walls at grain boundaries, domain fragmentation, and hysteresis were observed. MFM tips having very low coercivity highlighted domain walls, whereas higher-coercivity tips suffered unpredictable rotation of their magnetic moment due to both the sample and applied fields, leading to images which are difficult to interpret. For imaging of the finer-grained melt-quenched magnets, however, relatively high-coercivity tips were superior. These results show promise for the direct observation of the submicron-scale processes that dictate bulk magnetic properties, and the quantification of their field dependence. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 705-707 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a technique for characterizing the magnetic state of a magnetic force microscopy (MFM) probe as a function of uniform external magnetic field H. A local magnetic field is generated by micron-scale current carrying conductors and directly imaged by MFM. As H alters the magnetic state of the probe, changes in image contrast yield componentwise measures of the tip's net magnetic moment m, tip hysteresis loops and coercivities, and possible orientations (vertical vs lateral) of remanent states mr used for most MFM imaging. Results are presented for a variety of thin-film probes. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 165 (1970), S. 110-124 
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The synthesis of protein and nucleic acids was studied by isotope incorporation and dilution in the plasmodia ofPhysarum polycephalum during periods of growth and differentiation (spherule formation). The total protein content decreased during starvation, but protein synthesis still occurred, probably at the expense of proteins previously synthesized during growth. Studies on leucine incorporation showed that protein synthesized during growth had a greater turnover than did protein formed by starving cultures, when both types of cultures were transferred to starvation conditions. Protein synthesis after prolonged starvation was rapidly and markedly decreased following the inhibition of RNA synthesis, whereas no such direct dependence on RNA synthesis was observed in growing cultures or during early starvation. The kinetics of RNA synthesis and the types of RNA formed were also shown to differ in growth and starvation. RNA turnover was low in growing cultures but substantial in starving cultures that were returned to growth medium. Qualitative differences in pulse-labeled RNA extracted from growing or starving cultures were revealed by methylated-albumin-kieselguhr column chromatography and sucrose gradient centrifugation. In starving cultures proportionately more labeled RNA was found in the lighter, non-ribosomal region of the gradient, and RNA from this region hybridized with denatured DNA to a greater extent than did other RNA fractions.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 36 (1972), S. 681-692 
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The net uptake of Na, K, Li, and Ca or Mg by excised barley roots was studied from bi-ionic and tri-ionic bentonite suspensions. The net uptake of Li from Li-Ca system progressed linearly with progressive Li levels and was related to the concentration of soluble lithium. Calcium in this system was taken up only at the 100 per cent Ca level. At lower Ca levels calcium was lost from the roots to the suspensions. In K-Mg and Na-Mg systems the net uptake of Na or K by the excised roots was related to the concentration of the cation in the solution phase. Magnesium uptake took place at 80 and 100 per cent Mg levels. It was much less than that of K or Na at similar levels. At lower levels of Mg the roots lost some of their initial Mg contents to the suspensions. In the Na-K-Mg system magnesium was not taken up by the excised roots. Sodium uptake was not practically affected by the Mg level, but K uptake was greatly enhanced by magnesium.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 36 (1972), S. 681-692 
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The net uptake of Na, K, Li, and Ca or Mg by excised barley roots was studied from bi-ionic and tri-ionic bentonite suspensions. The net uptake of Li from Li-Ca system progressed linearly with progressive Li levels and was related to the concentration of soluble lithium. Calcium in this system was taken up only at the 100 per cent Ca level. At lower Ca levels calcium was lost from the roots to the suspensions. In K-Mg and Na-Mg systems the net uptake of Na or K by the excised roots was related to the concentration of the cation in the solution phase. Magnesium uptake took place at 80 and 100 per cent Mg levels. It was much less than that of K or Na at similar levels. At lower levels of Mg the roots lost some of their initial Mg contents to the suspensions. In the Na-K-Mg system magnesium was not taken up by the excised roots. Sodium uptake was not practically affected by the Mg level, but K uptake was greatly enhanced by magnesium.
    Type of Medium: Electronic Resource
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