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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 54 (1992), S. 470-473 
    ISSN: 1432-0630
    Keywords: 71.70 ; 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The emission spectrum of Cr3+ in Y3Ga5O12 crystalline thin films at 10K is composed of the sharp R 1-line, its phonon sideband, and the very weak broadband. The lineshape of R 1-line at the peak wavelength of 689.8 nm cannot be fitted to a single Gaussian. This suggests that there exist several different Cr3+ sites in the thin film. This fact is confirmed by lifetime measurements; the radiative decay of the fluorescence is decomposed into multiple-exponential curves. The dominant component (2.8 ms) of the decay curve for the broadband emission is equal to those (2.4 ms) for R 1-line and its phonon sidebands. This result is discussed in terms of a tunneling model.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 50 (1990), S. 565-572 
    ISSN: 1432-0630
    Keywords: 78.40 ; 78.55 ; 42.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This paper describes measurements of the R-line emission from Cr3+ ions in Y3Ga5O12, Gd3Sc2Ga3O12, and Gd3Sc2Al3O12. Discrete splittings of the lines are interpreted as due to disorder on the cation sublattices. Assuming statistical distributions of the cations on the different cation sublattices enables estimates to be made of the degree of non-stoichiometry in the crystals.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 53 (1991), S. 209-213 
    ISSN: 1432-0630
    Keywords: 42.70 ; 78.50 ; 78.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This paper reports on the luminescence spectrum, its excitation-wavelength dependence and decaytime of Cr3+:LiF crystals. In contrast to Al2O3 and MgO, where the Cr3+ luminescence at low temperature is due to the R-line and its vibronic sideband, luminescence from Cr3+:LiF is assigned to the broad-band 4 T 2→4 A 2 transition. A periodic structure in the vibronic sidebands of this transition occurs with energy separations of ca. 60 meV. The linear polarisation of the vibronic sidebands shows that their radiative transition takes place from the lowest excited level of the 4 T 2 state, i.e. 4 B 1, into the 4 A 2 ground state of Cr3+ ions in orthorhombic symmetry sites. The crystal-field parameters calculated from the experimental data, and luminescence decay-time of the two polarized configurations of the 4 B 1(4 T 2)→4 A 2 transition are also reported.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 72 (1981), S. 545-550 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Blocks of tissue from various organs of the rat have been chilled by precipitate immersion in n-hexane cooled to −70° C, and then stored at −70° C. At various intervals (up to 14 days) after chilling, cryostat sections were prepared from these blocks and assayed for the activity of a variety of enzymes. Enzyme activity was measured by scanning and integrating microdensitometry. With the exception of acid phosphatase and cytochrome oxidase, all enzymes assayed were stable for at least 7 days after storage at −70° C and most were stable for 14 days. Storage of fresh-frozen sections at −30° C in the cabinet of the cryostat, for up to 24 h, had little effect on enzyme activity.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 72 (1981), S. 617-623 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The efficacy of Meldola Blue (MB), a new intermediate electronacceptor, has been compared with that of phenazine methosulphate (PMS) in the assay of oxidoreductase activity in cryostat sections; various tetrazolium salts have been used as the final electron-acceptors. Three enzymes: succinate dehydrogenase, glucose 6-phosphate dehydrogenase and lactate dehydrogenase were investigated, the activity in sections being quantitated by scanning and integrating microdensitometry. Phenazine methosulphate was superior to Meldola Blue in transferring reducing equivalents from reduced coenzyme to all the tetrazolium salts examined.
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 72 (1981), S. 91-99 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A method is described by which a numerical value can be assigned to the amount of DNA-synthesis shown graphically by population-histograms obtained by Feulgen cytophotometry. The index appeared to give a reasonable measure of DNA-synthetic activity in populations having very low, moderate and high mitotic indices and closely followed labelling indices obtained by autoradiography. Thus the advantage of a numerical value is that the DNA-synthetic activities in different populations can be compared for statistical analysis.
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Research in nondestructive evaluation 12 (2000), S. 133-143 
    ISSN: 1432-2110
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract. This paper is concerned with the influence of vacancies on the elastodynamic response of a periodic (square) array of identical spherical elastic inclusions embedded in an unbounded elastic matrix. A response function of the array is defined as H * (ω)\equiv R * (ω)/T * (ω) , where R * (ω) and T * (ω) are, respectively, the reflection and transmission spectra of the lattice. H * (ω) was measured for a ``perfect lattice,'' i.e., one without any vacancies, and was found to be characterized by lattice resonances. H * (ω) was also measured for lattices containing one and three vacancies within the 72 lattice site area insonified by the ultrasonic beam. A counter-intuitive observation is that the presence of even one vacancy significantly reduces the amplitude of the fundamental lattice resonance. Furthermore, in the case of the specimen containing three closely spaced vacancies, the reduction is not three times the reduction due to one vacancy; it is significantly less than that.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular histology 15 (1983), S. 275-276 
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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  • 19
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Synopsis Different grades of the colloid stabilizer, polyvinyl alcohol, used for protecting unfixed cryostat sections during cytochemical reactions, may have different effects on enzymatic activity. The influence of three grades of polyvinyl alcohol on the activities of ‘soluble’, membrane-bound and membrane-enclosed enzymes has been investigated in unfixed sections; the activities were measured microdensitometrically. The largest molecular weight polyvinyl alcohol (G18/140, mol. wt. about 90 000) did not retain glucose-6-phosphate dehydrogenase activity in sections of rat liver even when used at the maximum convenient concentration (12%); G04/140 and M05/140 (molecular weights of 15 000 and 25 000 respectively) retained this soluble enzyme if used at concentrations of 30 and 20% respectively. At these concentrations, lactate dehydrogenase activity was apparently decreased when G04/140 and M05/140 were used; this diminished activity has been shown to be due to the need to establish optimal concentrations of reactants for each grade of polyvinyl alcohol and for each reaction. When optimal concentrations of reactants were used, the activities of this enzyme in the presence of each grade of polyvinyl alcohol were identical. The presence of any type of polyvinyl alcohol did not influence the activities of mitochondrial succinate dehydrogenase or of the smooth endoplasmic reticulum enzyme, Δ5,3β-hydroxysteroid dehydrogenase. However, the presence of polyvinyl alcohol improved the state of the section.
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular histology 16 (1984), S. 111-122 
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A technique for the cytochemical demonstration of peroxidase activity in unfixed guinea-pig thyroid tissue is described in this paper. The substrate 3,3′-diaminobenzidine tetrahydrochloride (DAB) is oxidized by the peroxidase to form an insoluble reaction product. Optimal results were obtained after 20 min incubation at 37° C in reaction medium containing 1.4mm DAB (in 0.1m Tris-HCl) and 0.15mm hydrogen peroxide at pH 8.0. Peroxidase activity was seen in the thyroid follicle cells as a diffuse brown reaction product (which was more dense and granular in erythrocytes). The enzyme activity was quantified using a scanning-integrating microdensitometer, and the effects of two specific peroxidase inhibitors were evaluated. Both 3-amino-1,2,4-triazole and methimazole inhibited peroxidase activity in the follicle cells (enzyme activity was still seen in the erythrocytes), maximal inhibition occurring at 10mm. Stimulation of peroxidase in the thyroid was observedin vivo (1 I.U. TSH administered every 8 h for two days), with the maximal stimulation occurring after 1 day.
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