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  • 1
    Electronic Resource
    Electronic Resource
    Radiative recombination centers induced by stacking-fault pairs in ZnSe/ZnMgSSe quantum-well structures (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3944-3946 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stacking-fault pairs in ZnSe/ZnMgSSe quantum-well structures are found to induce enhanced radiative recombination visible as pairs of bright spots in microphotoluminescence intensity maps. Structural investigation by atomic-force microscopy and transmission electron microscopy (plan view as well as cross section) reveal that a widening and bending of quantum wells occurs when they are intersected by Frank-type stacking faults. The enlargement of the well width by up to 12 bilayers evokes an efficient localization of excitons. The localizing potential related to Shockley-type stacking-fault pairs is found to be much shallower. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125502
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  • 2
    Electronic Resource
    Electronic Resource
    Stepwise equilibrated graded GexSi1−x buffer with very low threading dislocation density on Si(001) (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2083-2085 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have grown stepwise equilibrated graded GexSi1−x(x≤0.20) buffers with threading dislocation densities between 102 and 103 cm−2 in their unstrained cap layers. The Ge content of the buffer was increased stepwise. The equilibrating treatment was performed as an in situ annealing in hydrogen at 1050 °C after each and every layer of the buffer. Subsequently, the buffer was grown relaxed layer by relaxed layer. The extreme low threading dislocation density was present on the whole area of 4 in. wafers. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113910
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  • 3
    Electronic Resource
    Electronic Resource
    Submicron-scale film morphology effects on media noise of CoCrTa thin films on smooth substrates : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 3958-3960 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of submicron-scale morphology on media signal-to-noise ratio (SNR) has been evaluated for Cr/CoCrTa thin films deposited on super-smooth Al/NiP substrates. Two types of morphology and topography variations were studied. First, the underlayer X was made either smooth or rough in the submicron scale, and the subsequent Cr and magnetic layers deposition replicated the topography of layer X. For the second case, two different buffer layers were deposited with flat and smooth topography in the submicron scale. The subsequently deposited Cr/CoCrTa layers are either morphologically homogeneous or inhomogeneous. In both cases SNR measurements show a dramatic dependence on the morphology. It is concluded that the submicron-scale morphology variation was a profound contributor to the difference in media SNR. To make high-performance ultrahigh-density media, morphology homogeneity in the submicron-scale is essential. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365022
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  • 4
    Electronic Resource
    Electronic Resource
    Addition of N2 as a polymer deposition inhibitor in CH4/H2 electrocyclotron resonance plasma etching of Hg1−xCdxTe (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3750-3752 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An approach is presented which eliminates the problems caused by hydrocarbon polymer deposition in etching compound semiconductor with CH4/H2 based plasmas. We find that atomic nitrogen, created by the addition of N2 to the plasma, inhibits polymer deposition in the chamber and on the sample. Atomic nitrogen has several beneficial effects; the elimination of polymer precursors, the reduction of the atomic hydrogen concentration, and a potential increase of methyl radical concentration. It is also demonstrated that the addition of N2 to CH4/H2 based electrocyclotron resonance plasmas used to etch HgCdTe eliminates the roughness normally formed during etching. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115371
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrasound acoustic emissions from dehydrating leaves of deciduous and evergreen trees (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: While drying, detached leaves produced ultrasound acoustic emissions (UAE) comparable to emissions from stem and twig wood. Experiments on Ilex aquifolium L. showed that the main source of these signals was cavitation in the veins, to which conduits and fibres probably both contributed. Regions of the leaf blade with abundant mesophyll and only small veins emitted few signals. More signals were counted on the adaxial side of the midrib than on the abaxial one and on the proximal third than on the distal one, in accordance with the anatomical structure. Sound attenuation was pronounced. Eight species were compared with respect to cavitation behaviour, field water relations and pressure–volume curves, and the data showed differences in cumulative number of events and resistance of leaves to cavitation. Data were generally in good agreement with anatomical structure and habitat preferences. The number of signals per conduit counted on cross-sections was in some leaves much higher than unity, which suggests short xylem elements or an acoustic activity of cells other than conduits. There was no correlation between cavitation threshold or cumulative number of signals and the degree of sclerophylly; unexpectedly, there was a correlation between the cumulative number of signals at a water potential of -1.3 MPa and the bulk modulus of elasticity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1997.d01-34.x
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  • 6
    Electronic Resource
    Electronic Resource
    Experimental studies on the suitability of human mesothelial cells for seeding vascular prostheses: shear stress resistance in vitro (1996)
    Springer
    Journal of materials science 7 (1996), S. 543-550 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: This investigation forms part of a study on the suitability of human omentum mesothelial cells (HOMES) as an alternative to endothelial cells (EC) for seeding vascular grafts. Isolated HOMES were grown in primary culture and characterized by their morphology (light microscopy and scanning electron microscopy (SEM)), as well as by fluorescence-activated cell sorting (FACS) and immunocytochemistry. The latter two methods showed cells which were positive for smooth muscle-type actin and cytokeratin, but negative for factor VIII-related antigen. HOMES were grown to confluence on glass with or without a fibronectin coating. Controlled shear stress was applied for up to 30 min using a plate and cone rheometer at 20 dynes/cm2. These dynamic culture conditions led to loss of only occasional cells. The most marked alterations seen on SEM were some cell elongation, marked raising of the nucleus and loss of luminal cytoplasmic microvilli. Time-lapse video microscopy revealed that shear stress also increased the spreading capacity of some cells. Similar experiments with venous endothelial cells gave a shearing off of a confluent monolayer. This investigation shows the marked shear-stress resistance of HOMES, a pre-requisite for their use to seed vascular prostheses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122177
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  • 7
    Electronic Resource
    Electronic Resource
    Screening of biomedical polymer biocompatibility in NMRI-mice peritoneal cavity: A comparison between ultra-high-molecular-weight polyethylene (UHMW-PE) and polyethyleneterephthalate (PET) (1997)
    Springer
    Journal of materials science 8 (1997), S. 239-245 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The peritoneal resident cell population is influenced by various inflammatory and immunogenic stimuli. The influence of intraperitoneal application of polyethyleneterephthalate (PET) (group A) and ultra-high-molecular-weight polyethylene (UHMW-PE) (group B) powders on peritoneal cell count and macrophage activity was investigated. Powders were tested to mimic wear particles from solid implant devices as these particles often cause chronic granulomatous inflammation. The results were compared with the inflammatory response following an abdominal midline incision (group C) and untreated animals (group D). On days 1, 7, 14 and 30 peritoneal cells were quantified and the number of active macrophages was assessed. Groups A and C mice showed a significant loss of macrophages in the peritoneal lavage at day 1 but this returned to normal values (group D) on day 7. In contrast, group B animals remained at low peritoneal cell counts but showed the highest number of active macrophages. Only in this latter group was adhesion formation and granulomatous clustering of polymer powder observed. Applying the parameters macrophage count and the number of active macrophages it can be concluded that PET elicits a weaker inflammatory reaction than UHMW-PE in mice peritoneal cavity. Thus this animal model may be used as a screening test for biomedical materials, especially their wear products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018595825048
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  • 8
    Electronic Resource
    Electronic Resource
    New Y-TZP powders for medical grade zirconia (1997)
    Springer
    Journal of materials science 8 (1997), S. 113-118 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract There is interest in using zirconia for biomedical applications as ballheads for total hip prostheses. Two potential types are under discussion:partially stabilized zirconia (PSZ) and tetragonal zirconia polycrystals (TZP)materials. Because of its enhanced material properties, TZP stabilized withyttria is favourable. To eliminate high amounts of natural radioactiveimpurities, the precursors are purified. The kind of precursor and purificationmethod determine the powder impurity level. The disadvantage of Y-TZP is thatthe hydrothermal decomposition reaction method is that it depends very stronglyon the grain size and the distribution of the stabilizing yttria within thezirconia grains. Thermodynamical and kinetic investigations on high puritycoprecipitated and yttria-coated zirconia powders show different behaviours.Y-TZP materials based on yttria-coated zirconia powders show excellentmechanical strength of more than 1000 MPa, a Weibull modulus of up to 20 a!nd a fracture toughness of 9 MPa√m. The material properties of Y-TZP ceramicsbased on coprecipitated powders and prepared under the same conditions are lessattractive. It is expected that materials based on yttria-coated zirconia willshow enhanced properties compared to materials derived from coprecipitatedpowders. Therefore Y-TZP materials derived from yttria-coated powders are veryattractive as medical grade zirconia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018562917779
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesen und Massenspektren von 3,17β-Dihydroxyandrostan-11,16-dionen und 17β-Hydroxyandrostan-3,11,16-trionen (1976)
    Springer
    Monatshefte für Chemie 107 (1976), S. 459-472 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The syntheses and mass spectra of the four 3,17β-dihydroxyandrostane-11,16-diones and of the two 17β-hydroxyandrostane-3,11,16-triones are described. These compounds decompose in the mass spectrometer in a different way than androstanes containing a carbonyl group in the position 11 or 16: First they eliminate the C-atoms 15 to 17. Then a cleavage of the C-atoms of the ringA plus C-6 follows resulting in key ions which contain the ringC and the C-atom 7. The connection of theA/B-ring system can be deduced by the spectra for all described compounds. The unequivocal determination of the configuration of the 3-hydroxy group is possible only for the 3,17β-dihydroxy-5β-androstan-11,16-diones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00906875
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  • 10
    Electronic Resource
    Electronic Resource
    Excitation of aliphatic tertiary amines by electrical discharge (1976)
    Springer
    Applied physics 11 (1976), S. 175-177 
    Details
    ISSN: 1432-0630
    Keywords: 82.50 ; 42.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Trimethylamine and triethylamine are shown to luminesce at their wavelengths of fluorescence when excited by electrical discharge. When excited at low pressures or at high frequencies, a longer wavelength emission is observed at 380 nm. This emission, rather than being due to excimers which are known to exist for some tertiary aliphatic amines, is shown to be due to emission from a decomposition product. Lasing using electrical discharge pumping was attempted, but yielded negative results due to the rapid decomposition. Optical pumping might be successful however, and produce a tunable gas-phase ultraviolet laser
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00920600
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