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  • 1
    Electronic Resource
    Electronic Resource
    EPR and optical spectroscopy of Cr3+ ions in Y3Ga5O12 crystalline thin films (1992)
    Springer
    Applied physics 54 (1992), S. 470-473 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324174
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  • 2
    Electronic Resource
    Electronic Resource
    Charge compensation and the luminescence of Cr3+ in KMgF3 (1994)
    Springer
    Applied physics 59 (1994), S. 365-372 
    Details
    ISSN: 1432-0630
    Keywords: 71.70.Ch ; 71.55.Ht
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Studies of the photoluminescence spectra of Cr3+ ions in KMgF3 crystals co-doped with Cr3+ and Ni2+ ions are reported. Several crystal field sites are identified by the different R-line spectra due to the 2 E→4 A 2 transition and broadband luminescences associated with the 4 T 2→4 A 2 transitions. Cr3+ ions substituting without local charge compensation on the octahedral Mg2+ site give rise to a low temperature R line in photoluminescence at λ=702.3 nm with a radiative decaytime of 3 ms at T=14 K. At T=300 K this isotropic centre gives rise to an unpolarized broadband 4 T 2→4 A 2 emission, which results from the thermal occupancy of an excited 4 T 2 state just above the 2 E level which, at lower temperature, gives rise to emission in the R-line. Other crystal field sites are due to some Cr3+ ions having Mg2+ or K+ vacancies in nearest-neighbour positions, these vacancies being required to maintain charge neutrality in doped fluoride perovskites. The Cr3+−K+ vacancy complex results in the centre having trigonal symmetry, and low temperature, photoluminescence via R 1 and R 2 lines at 716.8 nm and 716.0 nm, respectively. Finally, Cr3+ ions having a nearest neighbour Mg2+ vacancy have tetragonal symmetry, experiencing weak crystal fields. In consequence, the 4 T 2 level lies below 2 E and the photoluminescence spectrum at low temperature takes the form of a polarized broad 4 T 2→4 A 2 band with peak at 760 nm and radiative decaytime of 54 μs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331713
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular Chaperones Stimulate Bone Resorption (1999)
    Springer
    Calcified tissue international 64 (1999), S. 214-218 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Bone resorption — Molecular chaperones — Heat shock proteins — Cytokines — Bacteria — Bone disease.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Molecular chaperones, also known as heat shock proteins (hsp), are intracellular proteins found in all cells that catalyze protein folding. We have discovered that one class of bacterial molecular chaperone, the chaperonins, are potent inducers of bone resorption. To address the question of whether the osteolytic activity of the chaperonins was unique to this protein class, or was a common attribute of molecular chaperones generally, we have examined a number of bacterial and mammalian molecular chaperones for activity in the murine calvarial bone resorption assay. All the Escherichia coli molecular chaperones (groEL, groES, and dnaK) were active. The osteolytic activity of groEL was inhibited by indomethacin and the natural antagonist of interleukin-1 receptor antagonist (IL-1ra) but was unaffected by neutralization of tumor necrosis factor (TNF) or inhibition of 5-lipoxygenase. Mammalian molecular chaperones of molecular mass 27, 47, 70, and 90 kDa were also tested and, with the exception of the 47 kDa protein, all showed activity in the murine calvarial assay. Molecular chaperones appear, therefore, to have the capacity to modulate the cellular processes in bone explant cultures, resulting in resorption of the calcified matrix. The possibility that these proteins could play a role in the normal or pathological remodeling of bone is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900605
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  • 4
    Electronic Resource
    Electronic Resource
    Temperature dependence of the lifetime of Cr3+ luminescence in garnet crystals I (1990)
    Springer
    Applied physics 50 (1990), S. 425-431 
    Details
    ISSN: 1432-0649
    Keywords: 42.70 ; 79.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The lifetimes of the R-lines from the 2 E level and the broad bands from the 4 T 2 level of Cr3+ ions in various garnet crystals vary with the energy separation between the 2 E and 4 T 2 levels, which change systematically with the composition of host crystal. The trend of the Cr3+ lifetimes, as well as their temperature dependences in garnet crystals, is explained by zero-point vibration and phonon-assisted tunnelling between the 2 E and 4 T 2 states of Cr3+ ion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00325096
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  • 5
    Electronic Resource
    Electronic Resource
    The influence on enzyme activity of storage of tissue blocks at −70° C (1981)
    Springer
    Histochemistry and cell biology 72 (1981), S. 545-550 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00493274
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  • 6
    Electronic Resource
    Electronic Resource
    Intermediate electron-acceptors in quantitative cytochemistry (1981)
    Springer
    Histochemistry and cell biology 72 (1981), S. 617-623 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00493278
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  • 7
    Electronic Resource
    Electronic Resource
    The assessment of DNA-synthetic activity (1981)
    Springer
    Histochemistry and cell biology 72 (1981), S. 91-99 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00496783
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  • 8
    Electronic Resource
    Electronic Resource
    Elastodynamic Response of a Periodic Layer of Spherical Particles Containing Vacancies (2000)
    Springer
    Research in nondestructive evaluation 12 (2000), S. 133-143 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001640000011
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  • 9
    Electronic Resource
    Electronic Resource
    Killing of the Yeast and Hyphal Forms of Candida albicans Using a Light-Activated Antimicrobial Agent (1999)
    Springer
    Lasers in medical science 14 (1999), S. 150-157 
    Details
    ISSN: 1435-604X
    Keywords: Keywords:Candida albicansCandidosis; Hyphae; Lethal photosensitisation; Toluidine blue O; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. Oral infections due to Candida albicans are a common occurrence in patients with acquired immunodeficiency syndrome (AIDS). The purpose of this investigation was to determine whether the yeast and hyphal forms of the organism could be killed using the light-activated antimicrobial agent toluidine blue O (TBO). Three variables were investigated: TBO concentration, laser light dose and pre-irradiation time (PIT). Irradiation with light from a helium neon (HeNe) gas laser used in conjunction with the photosensitiser TBO resulted in substantial kills of both the yeast and hyphal forms. Killing was light dose-dependent with 42 J being the most effective dose. The optimum PIT for the yeast form was 5 min, whereas killing of the hyphal form was not affected by PIT. The results of this study have shown that both forms of C. albicans are susceptible to lethal photosensitisation using TBO in conjunction with HeNe laser light, suggesting the possibility that this approach could be useful for eliminating the organism from diseased lesions in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101030050037
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  • 10
    Electronic Resource
    Electronic Resource
    Polarization of emission spectra from Ti3+-doped oxide crystals (1991)
    Springer
    Applied physics 52 (1991), S. 225-229 
    Details
    ISSN: 1432-0649
    Keywords: 42.55R ; 42.70 ; 79.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Ti3+ ion in YAlO3 (YAP), Y3Al5O12 (YAG), and Al2O3 crystals occupies distorted octahedral sites relative to the nearest neighbour ligand ions. Such distortions are of even-parity in YAG where the zero-phonon lines in emission occur via magnetic dipole transitions. In contrast, the zero-phonon transitions occur by electric dipole processes in Ti3+:YAP and Ti3+:Al2O3 where there are odd-parity distortions from octahedral symmetry. This paper reports measurements of the zero-phonon lines of Ti3+ ions in YAP, YAG, and Al2O3 at 10 K. The zero-phonon lines of Ti3+:YAP are strongly polarized perpendicular to the tetragonal axis and those of Ti3+:Al2O3 parallel to the trigonal axis. The experimental results are shown to be in accord with a molecular orbital model of the radiative transition according to which the transition intensities derive from odd-parity ligand wavefunctions induced into even-parity ground and excited Ti3+ wavefunctions by odd-parity crystal distortions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750955
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