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  • Engineering  (10)
  • Gadolinium  (3)
  • polyethylene  (3)
  • 79.20  (2)
  • 1
    Electronic Resource
    Electronic Resource
    CPS K 843 Radiation-induced crosslinking: Effect on structure of polyethylene (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 109-115 
    Details
    ISSN: 1435-1536
    Keywords: Crosslinking ; radiation ; polyethylene ; density ; crystallinity ; d-spacings ; phase densities ; crosslink locations ; lateral grain boundaries ; crosslink mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Branched polyethylene irradiated (0–400 Mrad) with a Co60 source at room temperature under vacuum was studied by density, wide- and small-angle X-ray scattering (WAXS and SAXS) measurements. The radiation effects on the structure of bulk, branched polyethylene are quite similar to those observed by others on single crystals or oriented preparations. These effects include changes in bulk densityϱ, crystallinity(w c orv c) and¯d 100 and¯d 200 spacings as a function of irradiation. A decrease in crystallinity is seen to begin at radiation dose ≈100 Mrad whereas lattice expansion indicating onset of an orthorhombic-hexagonal transition can begin as low as 10 Mrads. The decrease in crystallinity can be attributed to additional lattice distortions primarily introduced by the crosslinks occurring at the lateral grain boundaries, while lattice expansion can be associated with the same crosslinking mechanism which begins at the defects both within the crystals as well as those outside the crystals at the lateral grain boundaries. Strong evidence for a primary crosslinking-at-the-defects mechanism has also come fromϱ c andϱ a data obtained in this study as a function of radiation dose. The same data have also led to an excellent correspondence between the measured density crystallinityv c and the measured WAXS crystallinityw c. Without consideration of the effects of crosslinks onϱ c andϱ a one would have obtained a divergence of the two crystallinities, especially at radiation doses greater than 100 Mrads.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01412784
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  • 2
    Electronic Resource
    Electronic Resource
    Trapping and reflection coefficients for3He in Ni at oblique incidence (1983)
    Springer
    Applied physics 31 (1983), S. 37-44 
    Details
    ISSN: 1432-0630
    Keywords: 79.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The areal density and the depth distribution of3He trapped in Ni as a function of the bombarding fiuence was measured in the energy range of 1–25 keV and at angles of incidence between 0 and 85° using nuclear reaction analysis. At fluences below saturation a linear relation is found between the areal density and the fiuence. From its slope the trapping and reflection coefficients can be determined. The experimental data for trapping and reflection coefficients and for the depth profiles were compared with computer simulation results from the TRIM program. To reduce uncertainties in the absolute values of the experimental trapping coefficients, they were normalized to the TRIM values at normal incidence. The dependence of the measured reflection coefficient on the angle of incidence between 0 and 80° shows good agreement with the calculated data for incident energies from 3 to 25 keV, but for 1 keV the measured reflection coefficients are higher than the calculated ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617186
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  • 3
    Electronic Resource
    Electronic Resource
    Trapping and reflection coefficients for deuterium in graphite at oblique incidence (1984)
    Springer
    Applied physics 33 (1984), S. 265-268 
    Details
    ISSN: 1432-0630
    Keywords: 79.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Trapping and particle reflection coefficients for 0.4–10keVD on graphite have been measured for angles of incidence 0≦α≦85° by determining the areal density of implanted D as a function of the implanted fluence. The experimental data are compared to computer calculations with the TRIM-program. The agreement between measurement and calculation is good.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614669
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  • 4
    Electronic Resource
    Electronic Resource
    The MRI signs of spinal arachnoid diverticula (1997)
    Springer
    Neuroradiology 39 (1997), S. 446-449 
    Details
    ISSN: 1432-1920
    Keywords: Key words Arachnoid diverticula ; Spine ; Magnetic resonance imaging ; Gadolinium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Our goal was to find MRI signs of use for identifying a spinal arachnoid diverticulum. Three cases of spinal arachnoid diverticula, one extradural and two intradural, were examined on a 1.5 T imager. There was obvious mass effect on the adjacent structures in one case and increased signal intensity in the diverticulum on proton density- and T2-weighted images in two cases. Signal changes due to turbulent movement of the spinal fluid inside the diverticula were seen in all cases on sagittal fast spin-echo (FSE) proton density- and T2-weighted images; it was difficult to tell whether these signal changes imply a communication or are simply FSE artefacts. On contrast-enhanced studies, all cases showed partial enhancement inside the diverticula. There thus are four signs of diverticula: mass effect, the increased signal, signal void sign and partial enhancement; the last of these, the most reliable, has never been reported before.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050443
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  • 5
    Electronic Resource
    Electronic Resource
    Central gadolinium enhancement of an acute spontaneous spinal epidural haematoma (1996)
    Springer
    Neuroradiology 38 (1996), S. S114 
    Details
    ISSN: 1432-1920
    Keywords: Key words Spine ; haemorrhage ; Gadolinium ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Spontaneous spinal epidural haematoma (SSEH) is uncommon, but central gadolinium (Gd) enhancement of the haematoma is even rarer. To our knowledge, only one case has been reported, but no explanation was given concerning the mechanism of this enhancement. We present a case of SSEH with unusual central Gd enhancement which we believe is due to oozing from the injured posterior internal venous plexuses. Therefore, although rare, central Gd enhancement of an epidural mass should not rule out the possibility of a haematoma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050934
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  • 6
    Electronic Resource
    Electronic Resource
    Central gadolinium enhancement of an acute spontaneous spinal epidural haematoma (1996)
    Springer
    Neuroradiology 38 (1996), S. S114 
    Details
    ISSN: 1432-1920
    Keywords: Spine, haemorrhage ; Gadolinium ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Spontaneous spinal epidural haematoma (SSEH) is uncommon, but central gadolinium (Gd) enhancement of the haematoma is even rarer. To our knowledge, only one case has been reported, but no explanation was given concerning the mechanism of this enhancement. We present a case of SSEH with unusual central Gd enhancement which we believe is due to oozing from the injured posterior internal venous plexuses. Therefore, although rare, central Gd enhancement of an epidural mass should not rule out the possibility of a haematoma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02278136
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  • 7
    Electronic Resource
    Electronic Resource
    Radiation-induced crosslinking: II. Effect on the crystalline and amorphous densities of polyethylene (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 469-476 
    Details
    ISSN: 1435-1536
    Keywords: Crosslinking ; radiation ; polyethylene ; density ; crystallinity ; d-spacings ; phase densities ; crosslink locations and mechanisms ; defects ; lateral grain boundaries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Small-angle x-ray scattering (SAXS) was used to determine the structural changes in polyethylene induced by radiation. The changes in densities of the crystalline and amorphous phases, ρ c and ρ a , were calculated after direct determination of the mean square density fluctuation 〈η2〉. ρ a increases with increasing radiation dose for both linear and branched polyethylene. This accounts for the serious discrepancy between crystallinities determined from wide-angle x-ray scattering and density measurements. This study confirms our previous proposal that crosslinks occur primarily in the noncrystalline phase, most likely at the defects in the lateral grain boundary regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655884
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  • 8
    Electronic Resource
    Electronic Resource
    Radiation-induced crosslinking: III. Effect on the crystalline and amorphous density fluctuations of polyethylene (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 353-363 
    Details
    ISSN: 1435-1536
    Keywords: Crosslinking ; radiation ; polyethylene ; density ; crystallinity ; phasedensities ; densityfluctuation ; phasedensityfluctuations ; Crosslink locations and mechanisms ; defects ; lateral grainboundaries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Small-angle x-ray scattering (SAXS) was used to determine density fluctuation in radiation-induced crosslinked polyethylene of varying degrees of crystallinity. Density fluctuation FL decreases with increasing crystallinity, while it increases linearly with increasing radiation dose or degree of crosslinking. By means of extrapolation, density fluctuations in the crystalline and the amorphous phasesFL c andFL a were obtained. At a given dose,FL a is greater thanFL c . The increase inFL a with radiation is found to be much greater than that ofFL c compared with the initial values at 0 Mrad,FL c showing only a negligible increase event at 312 Mrad. The present findings suggest that crosslinks are not introduced within the crystalline phase; they take place primarily in the noncrystalline phase, in agreement with the conclusions reached previously on the basis of changes in crystalline and amorphous densities in irradiated polyethylene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654582
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  • 9
    Electronic Resource
    Electronic Resource
    The method of fundamental solutions for non-linear thermal explosions (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 675-681 
    Details
    ISSN: 1069-8299
    Keywords: blow-up ; method of fundamental solutions ; BEM ; thin plate spline ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical method based on the method of fundamental solutions, thin plate spine interpolation and monotone iteration is devised to find the minimal solution of the steady-state blow-up problem. The method of fundamental solutions requires neither domain nor boundary discretization and results in high accuracy and efficiency. For illustration, critical values of the Frank-Kamenetskii parameter are given for different geometrical boundaries in the two-dimensional case.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1640110806
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  • 10
    Electronic Resource
    Electronic Resource
    The method of fundamental solutions and quasi-Monte-Carlo method for diffusion equations (1998)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 43 (1998), S. 1421-1435 
    Details
    ISSN: 0029-5981
    Keywords: method of fundamental solutions ; particular solution ; diffusion equations ; quasi-Monte-Carlo method ; Laplace transform ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The Laplace transform is applied to remove the time-dependent variable in the diffusion equation. For non-harmonic initial conditions this gives rise to a non-homogeneous modified Helmholtz equation which we solve by the method of fundamental solutions. To do this a particular solution must be obtained which we find through a method suggested by Atkinson. To avoid costly Gaussian quadratures, we approximate the particular solution using quasi-Monte-Carlo integration which has the advantage of ignoring the singularity in the integrand. The approximate transformed solution is then inverted numerically using Stehfest's algorithm. Two numerical examples are given to illustrate the simplicity and effectiveness of our approach to solving diffusion equations in 2-D and 3-D. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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