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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of radiosurgery 1 (1998), S. 17-30 
    ISSN: 1573-8752
    Keywords: Brain metastases ; prognostic factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The last decade has witnessed an exponential proliferation of radiosurgery facilities in the United States and around the globe, and consequently, several tens of thousands of patients have undergone this procedure for a variety of intracranial and skull-base abnormalities. Since brain metastases represent the most common intracranial neoplasm, these have become a common target for radiosurgery. We present a review paper summarizing the major issues surrounding the management of brain metastases as well as an English-language literature review of 20 independent reports, using either γ-knife or linear accelerator-based radiosurgery, with 〉1250 patients and 〉2100 lesions available for analysis. Variable reporting in the studies precludes a definitive analysis and comparison of all factors in a rigorous statistical fashion, but the composite data reveal an average local control rate of 83% and a median survival of 9.6 months, which are comparable to those in recent surgical reports. Prognostic factors for survival are beginning to be unraveled, and the most important ones appear to be the presence of fewer than three lesions, controlled extracranial disease, and Karnofsky performance score. The exact impact of dose has not been clarified, but a dose–response relationship, especially for ≥18 Gy, is emerging. The role of whole-brain radiotherapy remains unresolved; it may enhance local control but does not convincingly improve survival and, in some series, is associated with an increased risk of late complications, which appear to be less than 5% on average. The concerns regarding chronic steroid dependance and increased intracranial edema do not appear to be a common problem. With such a large base of uncontrolled evidence, this is an opportune time for conducting and completing randomized trials to validate these observations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 130 (2000), S. 151-179 
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Perturbed angular correlation of gamma rays (PAC) was applied to measure concentrations of point defects in quenched and milled intermetallic compounds. Two systems with high ordering energies were studied, PdIn and NiAl, with principal results obtained for PdIn. The defects, lattice vacancies and antisite atoms, were detected by quadrupole interactions induced at nuclei of nearby In/Cd probe atoms. Measurements on annealed, quenched and milled samples are compared to identify quadrupole interaction signals with specific configurations of defects near probe atoms. Müller and Hahn had previously identified signals with a Pd-vacancy in the first near-neighbor shell of the In probe and a Pd-antisite atom in the second shell. Six additional signals are identified in this work, including two distinct configurations of two Pd-vacancies in the first shell, a Pd-vacancy in the fourth shell, an In-vacancy in the second or third shell, and an In-antisite atom in the first shell. After quenching, observation of both Pd and In-vacancies after quenching from 1100-1500 K demonstrates that the high temperature equilibrium defect is the Schottky vacancy pair. An activation energy of 0.91(18) eV was determined for formation of a Schottky pair. After milling, the site fraction of probes having one Pd-vacancy in the first shell increased rapidly and saturated at a value of about 20%. This implies a Pd-vacancy concentration of about 3.3 at.%, with a corresponding enthalpy of the order of 3 kJ mol−1, making a significant fraction of the excess enthalpy in the milled intermetallic. After milling NiAl, a Ni-vacancy concentration of order 1–10 at.% was observed. A comparison is made of defect combinations observed after mechanical milling of PdIn and NiAl by PAC and of other intermetallics by Mössbauer spectroscopy. Dominant defects produced by milling are the Schottky pair for PdIn, triple defect for NiAl and FeRh and antisite atom pair for FeAl.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 80 (1993), S. 1117-1120 
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The technique of perturbed angular correlations of gamma rays (PAC) is applied for the first time to study the structure of small metal clusters. Metal clusters containing111In probe atoms with 50 nm radii were synthesized by dissolving InCl3 containing111In in hexane using a surfactant, thereby creating an inverse micellar solution. The salt was then reduced to metal form by addition of NaBH4. 100% conversion efficiency of In salt to metal clusters was achieved. PAC measurements at 293 K on the111Cd daughter nuclide exhibited a nuclear quadrupole interaction with coupling frequency ω0=16.0(5) Mrad/s and a small asymmetry parameter, η=0.20(4). The frequency is as observed for bulk In crystals, but a non-zero value of η has not been previously reported. Lack of inhomogeneous signal broadening and the faceted shape of some nanoclusters suggest high crystal perfection.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 92 (1994), S. 949-953 
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High-purity Fe powder was mechanically milled under argon at ambient temperature using an SPEX 8000 mill. The local atomic and magnetic structure was studied using57Co/Fe Mössbauer and111In/Cd perturbed angular correlations (PAC) spectroscopies. After 32 hours of milling, X-ray diffraction revealed effective grain diameters of 18 nm and energy-dispersive X-ray analysis indicated a Cr impurity concentration of ∼5%, presumably introduced by mechanical attrition of steel ball bearings used for milling. In addition to a spectral component very similar to bulk iron metal, the Mössbauer spectra exhibited hyperfine field shifts attributed to the Cr impurities. PAC spectra on Fe milled for 5 h, with no contamination, exhibited two components: (1) A slightly broadened magnetic interaction attributed to interior, defect-free sites of In/Cd probes with a mean hyperfine field slightly greater than in macroscopic grains. The defect-free site fraction grew appreciably during milling, even though In is essentially insoluble in Fe. (2) An indistinct signal due to mixed magnetic and quadrupole interactions attributed to probes at surface or other defect sites.
    Type of Medium: Electronic Resource
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