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  • 1985-1989  (3)
  • 1975-1979
  • 1989  (3)
Material
Years
  • 1985-1989  (3)
  • 1975-1979
Year
  • 1
    ISSN: 0942-0940
    Keywords: Hydrocephalus ; intraventricular tumour ; postoperative complication ; subdural fluid collection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Subdural fluid collections appeared in 15 cases (39%) after removal of 38 intra- and paraventricular tumours in the third or lateral ventricle through 18 frontal and 20 parietal transcortical approaches. Transient fluid collections which disappeared within 2 weeks occurred in 6 cases (16%) and persistent ones in 9 cases (24%). Four of the 9 cases (11%) of collections required surgical treatment because of positive clinical signs and symptoms. Two cases had expansive fluid collections and the other two contained subdural haematomas at surgery. The risk factors likely to contribute to a persistent collection were preoperative ventriculomegaly (frontal horn index 〉 0.38) and a frontal transcortical approach. A symptomatic collection should be considered as a potential complication of the transcortical approach to intraventricular tumours and some methods should be devised to prevent it when intra- or paraventricular tumours with ventriculomegaly are removed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0649
    Keywords: 82.50 ; 33
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have been studying the practical CO2-laser-induced13C separation by a two-stage IRMPD process. The IRMPD of natural CHClF2 in the presence of Br2 mainly produced CBr2F2, which was found to be highly enriched with13C. The yield and13C-atom fraction of CBr2F2 were examined as functions of pulse number, laser line, laser fluence, total pressure, and Br2 pressure using a CO2 TEA laser with an output less than 1 J pulse−1 in order to optimize experimental conditions for13C separation. For example, we obtained CBr2F2 at a13C concentration of 55% in the irradiation of the mixture of 100-Torr CHClF2 and 10-Torr Br2 with the laser radiation at a wavenumber of 1045.02 cm−1 and at a fluence of 3.4 J cm−2. The mechanism for the IRMPD is discussed on the basis of observed results. Using 8-J pulses, we were able to obtain 1.9×10−4 g of13C-enriched CBr2F2 (13C-atom fraction, 47%) per pulse under selected conditions. It is possible to produce 90% or higher13C by the second-stage IRMPD of the CBr2F2 in the presence of oxygen.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0649
    Keywords: 82.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Difluoromethane CH2F2 containing 90–98% 13C was obtained in the selective IRMPD of mixtures of CBr2F2/HI, CCl2F2/HI, and CBrClF2/HI. In CBr2F2/HI mixtures, the intermediate product CHBrF2 resulting from the reaction between the initial decomposition fragment CBrF2 and HI underwent secondary selective IRMPD to form highly 13C-enriched CH2F2 in continuous laser irradiation. The intermediate product in the mixtures of CCl2F2/HI and CBrClF2/HI was found to be CHClF2, but no significant secondary photodecomposition in CBrClF2/HI mixtures occurred owing to the low absorption cross section of CHClF2 at the adopted laser frequencies and fluences. The observed decomposition probabilities and selectivities under different conditions with respect to laser frequency, fluence, and partial pressures of halogenated difluoromethanes and HI suggest that CBr2F2 is one of the better candidates for practical 13C separation by IRMPD.
    Type of Medium: Electronic Resource
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