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  • 1
    Electronic Resource
    Electronic Resource
    Collision induced dissociative chemisorption of CH4 on Ni(111) by inert gas atoms: The mechanism for chemistry with a hammer (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5756-5777 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dissociation of CH4 physisorbed on Ni(111) at 46 K is observed to be induced by the impact of incident inert gas atoms. The dynamics and mechanism of this new process, collision induced dissociative chemisorption, are studied by molecular beam techniques coupled with ultrahigh vacuum electron spectroscopies. The absolute cross section for collision induced dissociation is measured over a wide range of kinetic energies (28–109 kcal/mol) and incident angles of Ne, Ar, and Kr atom beams. The cross section displays a complex dependence on the energy of the impinging inert gas atom characteristic of neither total nor normal energy scaling. Quantitative reproduction of the complex dependence of the cross section on the Ar and Ne incident energy by a two-step, dynamical model establishes the mechanism for collision induced dissociation. Collision induced dissociation occurs by the impulsive transfer of kinetic energy upon collision of Ar or Ne with CH4, followed by the translationally activated dissociative chemisorption of the CH4 upon its subsequent collision with the Ni surface. The dependence of the probability of activated dissociation on the resultant CH4 normal energy derived from the fit of the model to the experimental cross section is in excellent agreement with the results of a previous study of the translationally activated dissociative chemisorption of CH4 on Ni(111). Collision induced activation and translational activation are shown to be consistent mechanisms for providing energy to CH4 to surmount the barrier to dissociative chemisorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457529
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  • 2
    Electronic Resource
    Electronic Resource
    Mid-infrared In1−xAlxSb/InSb heterostructure diode lasers (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 931-933 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stimulated emission at 5.1 μm was demonstrated from a broad area In1−xAlxSb/InSb heterostructure diode laser grown by molecular beam epitaxy. For a 5 μs pulse and a 500 Hz repetition rate the threshold current density was 1480 A cm−2 at 77 K and the maximum operating temperature was 90 K at a current density of 2680 A cm−2. Maximum peak power output was estimated to be 28 mW per facet at 77 K and 4500 A cm−2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118444
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  • 3
    Electronic Resource
    Electronic Resource
    LACK OF COMMON HAPLOTYPE AMONG FOUR FAMILY MEMBERS WITH LATE-ONSET KAPOSI'S SARCOMA (1989)
    Oxford, UK : Blackwell Publishing Ltd
    International journal of immunogenetics 16 (1989), S. 0 
    Details
    ISSN: 1744-313X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Kaposi's sarcoma is associated with an increased frequency of HLA-DR5. The hypothesized model of a susceptibility gene in linkage disequilibrium with DR5 may be tested by haplotype analysis in familial Kaposi's sarcoma. Our finding of no common haplotype among afflicted members of a family provides evidence against the hypothesized linkage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1744-313X.1989.tb00467.x
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of benzene from methane over a nickel(111) catalyst (1989)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 111 (1989), S. 8748-8749 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00205a043
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  • 5
    Electronic Resource
    Electronic Resource
    A Comparative Study of Normal B Cells and the EBV-Positive Burkitt's Lymphoma Cell Line, Raji, as Activators of the Complement System (1997)
    Oxford, UK : Blackwell Science Ltd
    Scandinavian journal of immunology 46 (1997), S. 0 
    Details
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Contradictory reports regarding the ability of complement receptor type 2 (CR2,CD21) on normal B cells to activate complement (C′) via the alternative pathway (AP), prompted us to compare the performance of human peripheral blood B cells and the Epstein–Barr virus-positive Burkitt's lymphoma cell line, Raji (a well characterized AP activator) by using flow cytometry. Measured in terms of the membrane deposition of C3 fragments per cell, Raji cells were significantly (6- to 26-fold) more effective as complement activators than were normal B cells. Raji cells were also found to express approximately four to five times as many CR2 as normal B cells. In addition, they distinguished themselves by displaying a greater Ca2+-dependent activation, with pooled normal human sera (NHS) as the complement source, and by degrading unprotected C3b fragments from iC3b to C3dg/C3d at a significantly lower rate than the B cells. The Ca2+ dependency of Raji cell activation was found to be partially a result of classical pathway (CP) triggering by specific antibodies in the NHS, although other triggering mechanisms may also be involved. If the influence of these variations between Raji cells and normal B cells was excluded, by relating deposition of anti-C3d-reactive fragments, during AP activation, to the number of CR2 expressed, the difference in performance between the two cell types was found to be insignificant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3083.1997.d01-122.x
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  • 6
    Electronic Resource
    Electronic Resource
    Recording sagittal condylar angles using a mandibular facebow (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of oral rehabilitation 24 (1997), S. 0 
    Details
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: summary The aim of this study was to determine the average sagittal condylar inclination angles of dentate subjects using a mandibular facebow with pencil tracing styli, to relate these angles to values assigned to articulators, and to assess the repeatability accuracy of drawing a tangent to a traced curve. The right and left sagittal condylar inclination angles of 103 subjects were recorded using a mandibular facebow with pencil tracing styli which marked a graph card during protrusive excursions. Tangents to the tracings were measured with a protractor allowing assessment of reproducibility. The mean left and right sagittal condylar inclination angles were 32° and 31.5°, respectively, with no significant differences (P=0.609). Individual right and left measurements within each group showed significant differences (P= 0.0000). The mean of the tangents drawn through three sagittal condylar angle tracings by 10 operators was 33.3°, and the mean of 10 tangents drawn through the same three tracings by one of the authors was 32.9°, with no significant difference (P= 0.634). The average sagittal condylar inclination angles found in this study are in agreement with those reported in the literature. In fixed sagittal condylar angle articulators 30° appear to be an appropriate setting. The reproducibility of this method of recording sagittal condylar inclination angles was found to be accurate for the individual operator and between operators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2842.1997.tb00293.x
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  • 7
    Electronic Resource
    Electronic Resource
    Crystallization and preliminary X-ray studies of rhamnogalacturonase A from Aspergillus aculeatus (1997)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 53 (1997), S. 105-107 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Recombinant rhamnogalacturonase A from Aspergillus aculeatus has been crystallized and X-ray diffraction data has been collected. Crystals were grown by the hanging-drop vapour-diffusion technique, under the conditions 10% PEG 8000, 0.05 M KH2PO4 and 0.1 M sodium acetate buffered at pH 3.5. The crystals diffract beyond 2.0 Å resolution and belong to one of the orthorhombic space groups I212121 or I222, with the unit-cell parameters a = 62.9, b = 125.4 and c = 137.0 Å. There is one molecule in the asymmetric unit and a solvent content of approximately 54%. The enzyme is highly glycosylated corresponding to 5.9 kDa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444996010785
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  • 8
    Electronic Resource
    Electronic Resource
    The First Structure at 1.8 Å Resolution of an Active Autolysate Form of Porcine α-Trysoin (1997)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 53 (1997), S. 311-315 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The first crystal structure of an active autolysate form of porcine α-trypsin (APT), a two-chain molecule obtained from the limited autolysis of porcine β-trypsin at position Lys145–Ser146, has been determined. APT crystallizes in space group P212121 with one protein molecule in the asymmetric unit. The structure was solved by molecular replacement followed by refinement using X-PLOR to an R factor of 0.200 and an Rfree of 0.285 for 8.0–1.8 Å data with r.m.s deviations from ideal values of 0.01 Å and 1.7° for bond lengths and bond angles, respectively. Comparison with inactive autolysate porcine ε-trypsin (EPT) and porcine β-trypsin in complex with bittergourd trypsin inhibitor (MCT) revealed a small but systematic directional chain shift around the active-site residues from APT to EPT to MCT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444997000358
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  • 9
    Electronic Resource
    Electronic Resource
    Case 23 nomination of precursory seismic quiescence as a significant precursor (1997)
    Springer
    Pure and applied geophysics 149 (1997), S. 79-113 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Conclusions Several cases of extremely strong quiescences have been investigated in great detail, and it was found that they are statistically highly significant and that they cannot be reasonably explained by catalog heterogeneity. Several additional cases of quantitatively measured quiescence have been documented. The method of measuring quiescence has progressed from using visual means to using a quantitative approach, and the understanding of the noise sources has significantly advanced during the last few years. Therefore I feel that quiescence is a real phenomenon and the method to detect it has matured to a point that is acceptable for the List of Significant Precursors, although considerably more work needs to be done to understand this parameter and its role in the earthquake generation process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00945162
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  • 10
    Electronic Resource
    Electronic Resource
    A hierarchical framework for the analysis of scale (1989)
    Springer
    Landscape ecology 3 (1989), S. 193-205 
    Details
    ISSN: 1572-9761
    Keywords: hierarchy theory ; nonequilibrium ; thermodynamics ; catastrophe theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Landscapes are complex ecological systems that operate over broad spatiotemporal scales. Hierarchy theory conceptualizes such systems as composed of relatively isolated levels, each operating at a distinct time and space scale. This paper explores some basic properties of scaled systems with a view toward taking advantage of the scaled structure in predicting system dynamics. Three basic properties are explored: (1) hierarchical structuring, (2) disequilibrium, and (3) metastability. These three properties lead to three conclusions about complex ecological systems. First, predictions about landscape dynamics can often be based on constraints that directly result from scaled structure. Biotic potential and environmental limits form a constraint envelope, analogous to a niche hypervolume, within which the landscape system must operate. Second, within the constraint envelope, thermodynamic and other limiting factors may produce attractors toward which individual landscapes will tend to move. Third, because of changes in biotic potential and environmental conditions, both the constraint envelope and the local attractors change through time. Changes in the constraint structure may involve critical thresholds that result in radical changes in the state of the system. An attempt is made to define measurements to predict whether a specific landscape is approaching a critical threshold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00131538
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