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  • Singlet oxygen  (2)
  • 72.40.+w  (1)
  • Preoperative planning  (1)
  • 1
    Electronic Resource
    Electronic Resource
    A comparative study of the accuracy of Ranawat’s and Pierchon’s methods to determine the centre of rotation in bilateral coxopathy (2000)
    Springer
    Skeletal radiology 29 (2000), S. 652-655 
    Details
    ISSN: 1432-2161
    Keywords: Keywords Centre of hip rotation ; Bilateral hip disease ; Total hip prosthesis ; Preoperative planning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. The objective of the study was to compare two methods (Ranawat’s and Pierchon’s) used to determine the centre of rotation of the hip and establish which method calculates a position nearer to the real centre of rotation. Patients and design. We selected 24 patients with unilateral osteoarthritis of the hip. The centre of rotation of the healthy hip was determined in two consecutive radiographic studies by superimposing a template of circles and using two axes as the reference lines (X-axis=teardrop line; Y-axis=a line perpendicular to the X-axis, drawn from the intersection of the ilio-ischiatic line and the teardrop line). After ensuring the stability of these references, both methods were applied to the same radiograph to determine which one established a centre of rotation nearer to the anatomical centre identified by the template of circles. Results. When the values for the healthy hip are compared with those obtained using Ranawat’s method, highly significant differences are observed for both X (P〈0.0001) and Y (P〈0.0001). When the results for the healthy hip are compared with the values obtained using Pierchon’s method, neither the X (P=0.722 ) nor the Y values (P=0.112) show any significant differences. It would be advisable to use Pierchon’s method to determine the centre of rotation during the preoperative planning for a total hip arthroplasty when the anatomical alteration is bilateral.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560000279
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Sonoluminescence: A new electrical breakdown hypothesis (1996)
    Springer
    JETP letters 64 (1996), S. 907-910 
    Details
    ISSN: 1090-6487
    Keywords: 72.40.+w
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We discuss an hypothesis wherein single-bubble sonoluminescence is attributed to electrical breakdown due to large pressure gradients existing for small bubble radii. These large gradients produce large electric fields (the flexoelectric effect) that lead to electrical breakdown, releasing energies up to 10−10 J, which is much larger than the light energy released in each cycle. This hypothesis appears to be consistent with several observations made in studies of the sonoluminescence process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.567246
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of the nuclear and extranuclear substitution on the singlet molecular oxygen [O 2(1Δg)]-mediated photooxidation of tyrosine derivatives: A kinetic study (1995)
    Springer
    Amino acids 8 (1995), S. 367-377 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Tyrosine ; Tyrosine derivatives ; Singlet oxygen ; Photooxidation ; Kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of the substitution pattern on the kinetics of the Type II (O2(1Δg)-mediated) dye-sensitized photooxidation of a series of nine tyrosine derivatives was investigated. Overall (kt) and reactive (kr) rate constants for the interaction of the excited oxygen species with the amino acid derivatives were determined. A parallel study on solvent and pH effects was carried out. The presence of different substituents in nuclear positions or in the amino acid side chain greatly affect the photooxidation rates. An upper limit for photooxidation quantum yield, calculated from the kinetic data, varies from 0.03 to 0.25, being the higher for halogenated tyrosines and the lower for esterified tyrosines and for the nitro-derivative. The variation of solvent polarity and pH of the reaction medium confirm that the presence of the ionized phenolate group in tyrosine, clearly dominates the quenching process. As already postulated for generic phenolic derivatives, it proceeds through a polar intermediate complex which posses some component of charge-transfer character. Esterification of the carboxilic acid of tyrosine selectively decreases the contribution of the reactive step to the overall process of O2(1Δg) quenching. An amide group in the same position does not produce noticiable changes in this sense. The presence of a highly deactivating nitro group in nuclear positions greatly diminishes the magnitude of both overall and reactive interactions. For all three, o-, m- and p-tyrosine the values of photooxidation quantum yields show an excellent parallelism with the rates of consumption of the — NH2 group of the amino acid chain, upon sensitized irradiation. It could react, in the cases of 0- and m-tyrosine in a secondary, non photochemical, step.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806554
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of the pH on the photodynamic effect in lysozyme A comparative kinetic study with the sensitized photooxidation of isolated amino acids (1995)
    Springer
    Amino acids 9 (1995), S. 123-134 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Eosin ; Lysozyme ; Photodynamic effect ; Photooxidation ; Singlet oxygen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The kinetics of the eosin-sensitized photooxidation ([O2(1Δg)]-mediated) of the protein lysozyme (Lyso) was investigated under two different pH conditions (pH 7 and pH 11). Rates of oxygen consumption and the fade in the protein fluorescence spectrum upon sensitized irradiation were monitored. Parallel studies on both denatured Lyso (absence of the four-S-S- bridges in the protein) and different mixtures of the photooxidizable amino acids of Lyso were also carried out. The mixtures maintained the same molar ratio as in the native protein, and were selected just in order to throw into relief the preferential amino acids that were being photooxidized at both pH values. Under work conditions Lyso was only photooxidizable at pH 7, whereas the opposite accounted for the denatured protein: only measurable oxygen consumption was detected at pH 11. Nevertheless, Lyso at pH 11, evidenced an important physical quenching of O2(1Δg) due to the Tyr and Trp residues. The results for the native protein were interpreted on the basis of a previously described dark complex Eosin-Lyso, which selectively favours the photooxidation of the bounded protein. The Trp residues were the main reactive entities in the native protein. The photodinamic effect in denatured Lyso was characterized by the prevalence of Tyr residues as photooxidizable targets. In the discussion of the results, a comparisson with the photooxidation kinetics of the mixtures of free amino acids was made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00805833
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    Paper (German National Licenses)
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