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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic resonance imaging in the evaluation of the lumbar herniated intervertebral disc (1993)
    Springer
    International orthopaedics 17 (1993), S. 241-244 
    Details
    ISSN: 1432-5195
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Deux cent onze patients atteints de hernie discale lombaire, confirmée par imagerie par résonance magnétique (IRM) et représentant 242 niveaux, ont été répartis en cinq groupes. Le diagnostic IRM a été comparé aux constatations opératoires afin d'évaluer de façon prospective la précision diagnostique de la classification IRM. Il n'y a pas eu d'exploration discale négative. Pour la distinction entre protrusion et autres types de hernie discale, la sensibilité, la spécificité et l'exactitude de l'IRM ont été respectivement de 92%, 91% et 92%. Pour la séquestration discale, la sensibilité a été de 92%, la spécificité de 99% et l'exactitude de 97%. En ce qui concerne l'extrusion sous-ligamentaire, on a noté une sensibilité de 71%, une spécifité de 82% et une exactitude de 79%, tandis que pour les extrusions trans-ligamentaires la sensibilité a été de 52%, la spécifité de 92% et l'exactitude de 79%. L'exactitude moyenne pour la prévision du type de hernie discale a donc été de 85%. L'IRM de haute résolution est donc très efficace pour la détection des lésions discales et leur classification.
    Notes: Summary Two hundred and eleven patients with lumbar disc herniation at 242 levels were divided into 5 groups by their appearances on magnetic resonance imaging (MRI), and the findings at operation were compared to assess the accuracy of the MRI classification. There were no negative explorations. There was 92% sensitivity, 91% specificity and 92% accuracy for MRI in distinguishing protruded discs from other forms of lumbar disc herniation. For sequestrated discs there was 92% sensitivity, 99% specificity and 97% accuracy. In the extruded subligamentous type there was 71% sensitivity, 82% specificity and 79% accuracy, and 52% sensitivity, 92% specificity and 81% accuracy in the extruded transligamentous type. The overall accuracy of MRI predicting the types of herniated lumbar intervertebral disc was 85%. High resolution MRI is sensitive in detecting disc disease and specific in characterizing various subgroups of disc herniation, especially those which are sequestrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194188
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetotransport and electron subband studies of edge delta-doped Al0.27Ga0.73As/GaAs single quantum wells (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2863-2867 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Shubnikov–de Haas and Van der Pauw Hall effect measurements at 1.5 K have been carried out to investigate the existence of a two-dimensional electron gas and to determine subband energies in a Si-delta-doped Al0.27Ga0.73As/GaAs single quantum well. The fast Fourier transformation results for the S-dH data indicate clearly the occupation of two subbands in edge delta-doped Al0.27Ga0.73As/GaAs quantum wells. Capacitance-voltage profiling and temperature-dependent photoluminescence measurements have been performed to characterize the properties of edge delta-doped Al0.27Ga0.73As/GaAs quantum wells. Using these experimental results and a self-consistent numerical method which took into account the exchange-correlation effects, the electron subband energies were determined. These results indicate that edge delta-doped Al0.27Ga0.73As/GaAs single quantum wells are similar to the asymmetrical potential wells occupied by relatively high electron carrier densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357523
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  • 3
    Electronic Resource
    Electronic Resource
    Epitaxial (GaAs)1−x(Si2)x metastable alloys on GaAs(001) and (GaAs)1−x(Si2)x /GaAs strained-layer superlattices: Crystal growth, spinodal decomposition, and antiphase domains (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1644-1655 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructure of single-crystal zincblende-structure (GaAs)1−x(Si2)x metastable semiconducting alloys with 0≤x≤0.40 has been investigated using triple-crystal x-ray diffraction (XRD), plan-view and cross-sectional transmission electron microscopy (TEM and XTEM), scanning transmission electron microscopy, and convergent-beam electron diffraction. The alloys, typically 1–3 μm thick, were grown using a hybrid sputter-deposition/evaporation technique on As-stabilized GaAs(001) and (GaAs)1−x(Si2)x/GaAs(001) strained-layer superlattices, (SLS). Alloy XRD peak widths were approximately equal to those of the GaAs substrates, 30 arcsec, and lattice constants, uncorrected for strain, obeyed Vegard's "law'' and decreased linearly with increasing x. TEM and XTEM examinations of (GaAs)1−x(Si2)x alloys with 0≤x≤0.20 grown on GaAs revealed no evidence of dislocations or other extended defects. Film/substrate lattice misfit strain in alloys with 0.11〈x〈0.20 was partially accommodated by the formation of a thin interfacial spinodal layer whose average thickness increased with x to (approximately-equal-to)70 nm. The spinodal region, which remained epitaxial, consisted of lenticular platelets extending along the [001] direction with a compositional modulation in orthogonal directions. Films with x≥0.20 exhibited, together with the interfacial zones, inhomogeneously distributed a0/2〈110〉-type threading dislocations. Antiphase domains were observed in alloys with x≥0.23. The use of (GaAs)1−x(Si2)x/GaAs SLS buffer layers extended the composition range to x=0.3 over which dislocation-free alloys, with no evidence of interfacial spinodal decomposition, could be obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357749
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  • 4
    Electronic Resource
    Electronic Resource
    The relationship between the microstructure and magnetic properties of sputtered Co/Pt multilayer films (abstract) : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6099-6099 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Co/Pd multilayer films (MLFs) are of interest because of their potential application as high-density magneto-optical recording media. Co/Pd MLFs with varying Co and Pd layer thicknesses were grown by sputter-deposition onto (100) Si wafers. X-ray diffraction and high resolution electron microscopy were used to study the microstructure of the films, and Lorentz microscopy was used to analyze their magnetic domain structure. The films show an fcc crystal structure with a compromised lattice parameter and a strong (111) crystallographic texture in the growth direction. The compromised interplanar spacing parallel to the surface increased with decreasing thickness ratio (tCo/tPd), and the columnar grain size decreased with increasing Pd layer thickness. Films with tCo=0.35 nm and tPd=2.8 nm (columnar grain diameter 20 nm) showed promising magnetic properties, namely a high perpendicular magnetic anisotropy (1.85×105 J m−3), with a perpendicular coercivity of 98.7 kA m−1, a perpendicular remanence ratio of 99%, and a perpendicular coercivity ratio of 88%. The magnetic domains were uniform and of a narrow stripe type, confirming the perpendicular easy axis of magnetization. The Curie temperature was found to be about 430 °C. Films of pure Co and Pd, grown for comparison, also showed columnar grain structure with grain-sizes of the same order as those seen in the MLFs. In addition the Pd films showed a (111) textured fcc structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358384
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  • 5
    Electronic Resource
    Electronic Resource
    Nanocrystalline Nd12Fe80B6Nb1Ga1 melt-spun ribbon with textured surface (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4756-4758 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In Nd-Fe-B melt-spun ribbon, Ga addition is found to be effective for the orientation of c axis of 2-14-1 grains normal to the ribbon plane even at high wheel surface velocity. A Nd12Fe80B6Nb1Ga1 melt-spun ribbon quenched with optimum wheel surface velocity was found to have textured structure on the free-side surface. Furthermore, this melt-spun ribbon was composed of fine grains of about 30 nm in size which is believed to be enough to provoke intergrain exchange interaction. The remanence and energy product of the field aligned powder of this melt-spun ribbon was about 7% and 20% higher than those of the not-aligned powder, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355904
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  • 6
    Electronic Resource
    Electronic Resource
    Intramolecular energy flow and bond dissociation in iodoacetylene and iododiacetylene (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4668-4681 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Intermolecular and intramolecular energy flow and subsequent bond dissociation in collinear collisions I–C≡C–H+Ar and I–C≡C–C≡C–H+Ar have been studied by classical trajectory techniques over the collision energy range of 0 to 10 eV. When the molecule is initially in the ground state, the overall energy transfer in I–C≡C–H+Ar is very small, but in I–C≡C–C≡C–H+Ar it is large. The collisionally perturbed C–H bond stores a large amount of energy from translation for a brief period during the early stage of collision and transfers most of it to the inner region of the molecule, specifically to the low frequency C–I vibration. Thus the high-frequency vibration of the perturbed C–H bond during the collision plays a crucial role in determining the extent of intramolecular energy transfer and, in turn, C–I dissociation. But in nondissociative collisions, there is another series of the C–H vibration at the latter stage of collision, transferring energy back to translation. This study also considers collision-induced intramolecular energy flow in the molecule with an initially excited C–H bond. The relaxation of the low-lying C–H excitation is very slow on a nanosecond time scale. However, when the excitation is high, the vibrational frequency of the C–H bond is significantly weakened, thus becoming comparable to that of the triple bond, in which case the isolating effect of the adjacent C≡C bond is no longer important and intramolecular energy flow becomes efficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467456
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  • 7
    Electronic Resource
    Electronic Resource
    Preparation and characterization of poly(.beta.-hydroxyalkanoates) obtained from Pseudomonas oleovorans grown with mixtures of 5-phenylvaleric acid and n-alkanoic acids (1991)
    s.l. : American Chemical Society
    Macromolecules 24 (1991), S. 5256-5260 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00019a004
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  • 8
    Electronic Resource
    Electronic Resource
    Kinetic and mechanistic investigations of the formation of polyimides under homogeneous conditions (1993)
    s.l. : American Chemical Society
    Macromolecules 26 (1993), S. 1344-1358 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00058a024
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  • 9
    Electronic Resource
    Electronic Resource
    Electromagnetic radiation from doubly rotated piezoelectric crystal plates vibrating at thickness frequencies (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6633-6642 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Exact solution of the three-dimensional linear equations of piezoelectromagnetism is obtained for doubly rotated piezoelectric crystal plates surrounded by vacuum and excited by face traction. A generalized Poynting's theorem is derived for general media in which electromagnetic and mechanical fields interact with each other. For linear piezoelectric crystals it is shown that the generalized theorem may still be interpreted as an energy theorem, and hence densities of energy stored in the electric, magnetic, and elastic strain fields can be identified. Radiated power, per unit surface area and averaged over the period, and induced strain and electric fields in the middle plane of the plate are calculated for doubly rotated quartz plates whose cut orientations follow the upper and lower loci of zeros of the first-order temperature coefficient of frequency of the x1 -thickness-shear mode. Quality factors and partition of stored energies are also examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345096
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  • 10
    Electronic Resource
    Electronic Resource
    Formation of a metastable ferromagnetic τ phase during containerless melt processing and rapid quenching in Mn-Al-C alloys (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 676-680 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Solidification of selected Mn-Al-C alloys during containerless levitation and rapid quenching has yielded the first report for a ferromagnetic metastable τ (L10) phase formed directly from the melt. Complete solidification to τ phase was interrupted by the competitive evolution of an equilibrium ε phase during recalescence. The amount of undercooling required to produce the metastable ferromagnetic τ phase in a Mn0.55Al0.433C0.017 alloy during solidification was estimated as approximately 470 K based on differential thermal analysis results. When the alloy carbon content was increased to 3.4 at. % (i.e., Mn0.55Al0.416Co0.034 alloy), a transition in structure development occurred so that the samples exhibited γ2 phase formation as well as τ and ε phases. Both microstructural observations and x-ray diffraction examination were used to guide the interpretation and the analysis of solidification pathways. The attainment of the high liquid undercooling required to nucleate the metastable τ phase from the melt may be facilitated by containerless processing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351326
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