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  • 1
    ISSN: 1432-1084
    Keywords: MRI ; MRA ; Meningiomas ; Arterial displacement ; Tumor-feeding vessels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A group of 41 patients with intracranial meningiomas were examined by MR imaging (MRI) and MR angiography (MRA) to assess the. clinical value of MRA in the preoperative evaluation of these patients. The results of MRA were compared with the results of intraarterial cerebral catheter X-ray angiography (XRA; n = 19) and with the operative findings (n = 41 ): Our results showed a good correlation between MRA and XRA/surgery in demonstrating the relationship between the tumor and adjacent venous and arterial structures. Use of MRA was also helpful in demonstrating the degree of intrinsic tumor vascularity. It also supplied important information for operative planning Adjunct XRA was mandatory if detailed information about tumor-feeding vessels was requested by the neurosurgeon, especially in highly vascularized angiomatous meningiomas and in meningiomas suspected of tumor feeding by vessels of the internal carotid artery.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 8586-8590 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We measured thermally irreversible line broadening features of photochemical holes burnt into a phthalocyanine doped Shpol'skii crystal. The broadening, as obtained from temperature cycling hole burning experiments is significant, indicating that irreversible structural changes do occur in Shpol'skii matrices. Different sites show a different behavior. As far as line broadening is concerned, the observed features are similar to glasses. The thermal recovery curve of the holes, however, differs very much from glasses. It can be fitted by a bimodal Gaussian distribution. This bimodal distribution is interpreted in terms of two categories of photoproduct states, which the phthalocyanine molecule can possibly occupy: In category one, the two inner protons are neighbors in category two, they are diagonal.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 8600-8603 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: From the pressure induced frequency shift of photochemical holes burnt into mesomorphyrin substituted horseradish peroxidase, we determined the compressibility of the protein and the vacuum frequency of the chromophore. From the compressibility, an estimation of the volume fluctuations of the biomolecule is possible.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 3134-3136 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We compare the spectral diffusion broadening of mesoporphyrin substituted horseradish peroxidase with the chromophore doped host glass. Whereas the broadening in the glass is smooth and follows a power law with an exponent close to (3)/(2) , there is a a steplike broadening in the protein which occurs around 14 K. The observed phenomena are interpreted on the basis of a two domain interaction of the chromophore with its environment.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 7619-7624 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We applied hydrostatic pressure to spectral holes burned into a resorufin doped ethanol/methanol glass. We found that the line shift is perfectly linear with pressure and showed a pronounced dependence on the burn frequency as predicted by theory [J. Chem. Phys. 90, 3274 (1989)]. We exploited the burn frequency dependence to determine the solvent shift of the dye probe and the compressibility of the alcohol glass used. On the other hand, the behavior of the hole width under pressure shows features not predicted by theory: The broadening is, like the line shift, dependent on the burn frequency within the inhomogeneous band, yet in a nonlinear fashion. We attribute the color effect in the pressure induced broadening of the hole to a breakdown of the Gaussian approximation.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 5501-5507 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We measured the pressure-induced shift and broadening of spectral holes for 14 different impurity sites in a polycrystalline solid solution of chlorin (17,18-dihydro-21H,23H-porphine) in benzophenone. In addition, we investigated the glassy phase of the same system in a frequency range which covered the entire inhomogeneously broadened band. The temperature range of the experiments was between 1.5 and 4.2 K. Pressure levels up to 10 MPa were applied. In the glassy phase, we observed a linear frequency dependence of the shift per pressure. However, in the crystalline phase, the general trend of the data clearly indicated a nonlinear frequency dependence. Yet, the individual sites, especially those with lower frequencies, showed a kind of stochastic scattering around the general trend behavior. The results were interpreted within the frame of existing models. The experiments demonstrate that matrix isolation combined with hole burning spectroscopy of large molecular impurities in polymorphic host materials under varying pressure conditions is a useful technique for determining molecular as well as bulk parameters, for examining problems of microelasticity and microplasticity, and for investigating the fundamental differences between glasses and crystals.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 189-194 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigated the hole-burning photoreaction of a dye complex in alcohol glass which undergoes both photochemical and photophysical transformations. By measuring separately the disappearance of the photoproduct at the respective wavelength ranges under thermal cycling conditions, we found that the photochemically transformed species recovered according to a Gaussian distribution of barrier heights, whereas the photophysically transformed species recovered in accordance with a 1/(V)1/2 distribution. It is suggested that this behavior is rather general and is intimately related to the nature of the phototransformation process.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 2210-2214 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 7887-7889 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 9262-9270 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present comparative investigations of doped benzophenone in its glass and crystal phases by using thermal cycling hole burning techniques. Chlorin and s-tetrazine were used as probe molecules. We measured the distribution of reactive barriers and the spectral diffusion behavior in both phases. The distribution in the glass is broad and is well described by a Gaussian. In the crystal, there are rather well-defined barriers, yet they are different for different sites. The respective kinetics is exponential and its temperature dependence is Arrhenius-like in contrast to the glass phase. Thermally induced spectral diffusion broadening in the glass phase is strong and shows the pattern well known from other organic glasses. In the crystal, it is much weaker, yet it is not completely absent. The experiments seem to indicate a threshold temperature ∼40 K. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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