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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 142 (2000), S. 1369-1375 
    ISSN: 0942-0940
    Keywords: Keywords: Central; lumbar disc herniation; outcome; surgery.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary  A follow-up study which describes the experience of the Department of Neurosurgery in Berne in the treatment of patients with central lumbar disc herniation (CLDH).  Background Data. The anatomical position of lumbar disc herniation, in general, does not seem to affect postoperative outcome. However, according to other studies a subgroup of patients with central lumbar disc herniations appears to have poorer results.  Objectives. The aim of the present study was to assess clinical outcome in a recent cohort of patients, to investigate whether there is a difference in outcome with regard to the surgical approach (unilateral vs bilateral) and to compare the postoperative results between the subcategories of CLDH: central massprolaps (CMP) and central contained disc herniation (CCDH).  Methods. Between 1990 and 1997, 40 out of 3150 patients operated on for lumbar disc herniation were diagnosed with CLDH (1.2%). The patients were operated on through unilateral or bilateral fenestrations with microdiscectomy. Recent follow-up studies were obtained by standardized questionnaires. The retrospective investigation was performed by an unbiased observer.  Results. Long-term follow-up was available for 34 of the 40 patients (85%) at a mean of 3.3 years. Eight patients had an excellent result (24%), 15 patients a good result (44%), 8 patients a fair (24%) and 3 patients had a poor result (9%). Overall, the operation was considered successful in 68% of patients. There was no statistically significant difference in outcome in patients with CMP as compared with those with CCDH (75% versus 64%). There was also no significant difference for better outcome between bilateral as compared with unilateral approaches.  Conclusions. Postoperative outcome of central lumbar disc herniation (CLDH) is poorer as compared with other types of lumbar disc herniation. The reason seems to be the anatomical position of the disc herniation with a peculiar derangement of the disc architecture. The surgical approach itself or the subcategories of CLDH appear to have only minor impact on postoperative outcome. Interlaminar fenestrations, in general, are appropriate for removal of the disc fragments.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 166-169 (July 1994), p. 523-528 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 28 (1972), S. 645-647 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The deviation of symmetry equivalent intensities from their mean values was used to determine a probable reflexion symmetry for the zeolite NaPl. The method of investigation is based on the χ2 test and compares the measured deviation with the one expected from counting statistics. The lattice dimensions of zeolite NaPl are cubic, but it was suspected that its symmetry is tetragonal and that the crystal is multiply twinned, thus simulating a near cubic X-ray pattern. Cubic symmetries were clearly rejected by the test and it was shown that reflexion symmetry mmm is a good approximation for the observed intensities.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0022-4596
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 352 (1991), S. 320-323 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The search for new zeolite-like structures was first extended beyond the traditional alummosilicates to the aluminophos-phate-based molecular sieves4, followed by explorations of more exotic structures such as beryllo-5 and zinco-phosphate and arsenate molecular sieves6. Some of these syntheses ...
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 25 (1992), S. 539-543 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A new method for unravelling the intensities of severely or exactly overlapping reflections in a powder diffraction pattern has been developed. The fast iterative Patterson squaring (FIPS) method involves an iterative procedure in which (1) a Patterson function is calculated using equipartitioned data (intensity ratio for overlapping reflections set to 1.0), (2) each point in the map is squared, (3) the new map is back-transformed to obtain new Fourier coefficients, and (4) these coefficients are then extrapolated to give a new set of |F|2 overlaphkl values and a new intensity distribution for the overlapping reflections (non-overlapping ones remain unaffected). The cycle is repeated until the intensity statistics of the overlapping reflections approximate those of the non-overlapping ones. Only after a redistribution of the intensities by the FIPS method was the ab initio structure solution possible for the molecular sieve SAPO-40 (structure-type code AFR), in which 65% of the reflections severely overlap.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 30 (1997), S. 1167-1172 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Given just a few strong low-index reflections, a periodic nodal surface (PNS), which divides the unit cell into regions of high and low electron density, can be generated. Fourteen known zeolite structures were examined to verify the validity of the procedure developed and in all cases the framework atoms were found to lie on just one side of the calculated curved surface. In other words, the surface defines a structure envelope. The same approach was applied to a few ionic and organic structures and was found to be equally valid. Since these reflections, with large d spacings, are precisely the ones that are least likely to be involved in overlap in a powder diffraction pattern, such a PNS can also be calculated using powder data. The resulting restriction in the region of the asymmetric unit in which atoms are likely to be found has immediate implications for any of the direct-space methods of structure determination from powder data. The use of this structure envelope as a mask in a straightforward grid search procedure reduced the computer time required to solve several framework structures by as much as two orders of magnitude.
    Type of Medium: Electronic Resource
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