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  • 1990-1994  (10)
  • 1900-1904
  • 1990  (10)
  • 1
    Electronic Resource
    Electronic Resource
    Interaction of hole trapping and transit effects in the temporal response of InP/InGaAs p-type insulator n-type photodiodes (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5343-5347 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photodiodes with thin (∼0.2 μm) InGaAs light absorbing layers placed inside much wider (∼2 μm)InP depletion regions were studied to understand the interaction of hole trapping at the InGaAs/InP heterojunction interface and carrier transit effects. In the three devices studied, the absorbing region was located (i) near the n+ side, (ii) in the center, and (iii) near the p+ side of the depletion region. The optical impulse response of these devices consists of a short pulse and a long exponential tail with a bias-dependent time constant. The relative charge in the fast and slow components could be measured and it was shown that the charge ratios correspond to the fraction of the depletion region transited before and after trapping. These studies show that electron trapping times are much shorter than hole trapping times, and that fast photodetection can occur even in the presence of a severe hole trapping problem if the distance between the trap and the p+ side of the depletion region is much smaller than the total depletion width.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347029
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  • 2
    Electronic Resource
    Electronic Resource
    The Phenotypes of Smooth Muscle Expressed in Human Atheroma (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 598 (1990), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1990.tb42286.x
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  • 3
    Electronic Resource
    Electronic Resource
    Film panel cases Society of Pediatric Radiology (1990)
    Springer
    Pediatric radiology 20 (1990), S. 212-217 
    Details
    ISSN: 1432-1998
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02012984
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Biosolubilization of low-rank coal by aTrametes versicolor siderophore-like product and other complexing agents (1990)
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 401-406 
    Details
    ISSN: 1476-5535
    Keywords: Siderophore ; Chelation ; Trametes versicolor ; Biosolubilization ; Leonardite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A heat stable, low molecular weight (〈1000) extracellular product inTrametes versicolor (=Coriolus versicolor=Polyporous versicolor) cultures was demonstrated to be a principal factor in the solubilization of leonardite and other low-rank coals. The solubilization of leonardite byT. versicolor cell-free cultures and active fractions was inhibited by Fe3+ and was mimicked by the siderophore desferal mesylate and the iron chelating agents EDTA and 8-hydroxyquinoline. Leonardite solubilization by these later compounds was also inhibited by Fe3+. The ferrated and unferrated form of the partially purified active component fromT. versicolor cultures demonstrated absorption spectra that were similar to the ferrated and unferrated form of desferal mesylate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01578100
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  • 5
    Electronic Resource
    Electronic Resource
    Multi-elemental depth profiling by microbeam PIXE of phenolic coatings exposed to sulphuric acid (1990)
    Springer
    Journal of materials science 25 (1990), S. 5173-5178 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The phenolic coatings used to protect the steel of railway tanks during the shipment of concentrated sulphuric acid have been studied by microbeam PIXE and a.c. impedance measurements. After repeated washing and filling cycles, these coatings begin to lose their resistance to corrosion but the breakdown mechanism is not presently well understood. A 20 μm focused proton beam has been used to scan the approximately 200 μm thick coatings to obtain the depth profiles of sulphur, which, as sulphate ions, are thought to migrate towards the steelcoating interface and initiate the breakdown process. Parallel electrochemical impedance spectroscopy (EIS) measurements have been performed to determine the electrical properties of the metal-coating system. Samples were exposed to concentrated sulphuric acid for periods of up to six months. The microbeam PIXE results indicate that the sulphur concentration has reached a saturation level after about ten weeks, which coincides with the onset of appreciable corrosion as determined from the impedance measurements. Two additional samples, which were treated to repeated cycles of immersion in acid followed by rinses in water, lost a large fraction of titanium at the exposed surface and after some twenty cycles were easily delaminated from the substrate, suggesting one possible breakdown mechanism. The use of an inexpensive proton microprobe provides a simple and rapid quantitative evaluation of sulphur concentrations and depth profiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00580147
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  • 6
    Electronic Resource
    Electronic Resource
    The mass spectra of 4-aminophenanthrene and its trifluoroacetic anhydride and perflnoropropionic anhydride derivatives (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 613-618 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several aminophenanthrenes have been examined with electron impact mass spectrometry. The trifluoroacetic anhydride (TFAA) and perfluoropropionic anhydride (PFPA) derivatives of 4-aminophenanthrene have been studied with electron impact as well as both positive and negative ion chemical ionization mass spectrometry utilizing methane as a reagent gas. The resulting mass spectra indicate a loss of water from the derivatives and a mechanism is proposed to account for this loss. The spectra also indicate unique fragmentation patterns associated with the position of the substituent, particularly the four position which is in the region of the molecule termed the bay region. Another interesting aspect is the spectral differences observed for the TFAA and PFPA derivatives of 4-aminophenanthrene. The positive ion chemical ionization mass spectrum of the TFAA derivative indicates an ion [M + H — H2O]+; however, the mass spectrum of the PFPA derivative of 4-aminophenanthrene indicates no water loss from the [M + H]+ ion. The negative ion chemical ionization mass spectra of the two derivatives are also very different. The mass spectrum of the TFAA derivative shows an [M — 18]- ion and the PFPA derivative shows successive losses of HF with no apparent loss of water.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200191007
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  • 7
    Electronic Resource
    Electronic Resource
    Study of the reaction of diazomethane with dansylated amino acid derivatives by gas chromatography/mass spectrometry (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 520-522 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Since the methylation of acids with diazomethane is widely used in trace analysis, it is extremely important for those using this technique to be alert to the analysis of compounds containing other functional groups which might become methylated with high concentrations of diazomethane. We have shown that by adding an excess of diazomethane to dansylated amino acids, not only is the methyl ester formed, but the products can be further methylated. The only remaining acidic hydrogen in the molecule is the hydrogen attached to the sulfonamide nitrogen, and the mass spectrometry results indicate that the methyl ester is formed first, and the N-methylated derivative is formed with excess diazomethane.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200190810
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  • 8
    Electronic Resource
    Electronic Resource
    (R,R)-2,3-Butanediol and (s)-pinanediol allylboronates in chiral synthesis of (2S,3S)-3-methyl-5-hexen-2-ol (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 1 (1990), S. 109-115 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (R,R)-Butanediol (dichloromethyl)boronate (1) with 1 equiv. allylmagnesium halide yields (R,R)-2,3-butanediol (1S)-(1-chloro-3-butenyl)boronate (3) together with the diallylated product (R,R)-2,3-butanediol (1-allyl-3-butenyl)boronate (4). The formation of 4 is unprecedented in reactions of α-chloroboronic esters with Grignard reagents. With methylmagnesium bromide 3 yielded (R,R)-2,3-butanediol (1S)-(1-methyl-3-butenyl)boronate (5), which failed to hydrolyze with water. Hydrolysis of 3 yielded impure α-chloroboronic acid, which was esterified with pinacol and treated with methylmagnesium bromide to form 6, which with (dichloromethyl)lithium followed by methylmagnesium bromide yielded diastereomeric boronic esters 7 and 8. Oxidation by hydrogen peroxide yielded (2S,3S)- and (2R,3S)-3-methyl-5-hexen-2-ol (9 and 10, ees unknown). Treatment of (s)-pinanediol allylboronate (11) with (dichloromethyl)lithium at -100°C followed by zinc chloride at up to 25°C has proceeded in the normal way to form (s)-pinanediol (1S)-(1-chloro-3-butenyl)-boronate (12), which has been elaborated via 13, 14, and 15 to (2S,3S)-3-methyl-5-hexen-2-ol (9) in 95% de.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hc.520010114
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  • 9
    Electronic Resource
    Electronic Resource
    Automatic delineation of drainage basins within digital elevation data using the topographic primal sketch (1990)
    Springer
    Mathematical geology 22 (1990), S. 189-209 
    Details
    ISSN: 1573-8868
    Keywords: artificial intelligence ; topographic analysis ; image analysis ; drainage networks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract A new technique for automatic delineation of drainage basin perimeters within digital elevation data is described which applies the topographic primal sketch to digital terrain data, and is much more natural and much more efficient than usual methods that rely upon moving a window over the array of data. This method is able to find drainage channels, mark water flow direction, and recover drainage basin areas. Results appear to be comparable to drainage patterns which can be interpreted visually from contours of the elevation data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00891823
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  • 10
    Electronic Resource
    Electronic Resource
    Poly(Phenylene oxide)/polyamide blends via reactive extrusion (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 1056-1062 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Reactive extrusion of functionalized polymers provides a convenient, commercially attractive route for the preparation of copolymers useful in compatibilization of polymer blends. In the current study, the grafting chemistry of maleic anhydride to poly(phenylene oxide) in the absence of a radical initiator is contrasted to that of efficient quinone-methide trapping agents such as maleimides. In the case of maleic anhydride, functionalization is shown to occur randomly along the polymer backbone whereas maleimides react to give both main chain and end-group derivatives. Use of this anhydride-functionalized polyfphenylene oxide and an end-group functionalized analog in blends with polyamide-6,6 affords high levels of graft and diblock copolymers respectively, sufficient for the preparation of highly ductile materials. The properties of these polyamide blends are found to depend on the amount of copolymer formed during extrusion with final copolymer levels being in turn returned to the degree of anhydride functionalization. The properties and morphology of blends containing graft or diblock copolymers derived from main-chain and end-group functionality respectively, are rationalized in terms of the relative effectiveness of different copolymer structures in blend compatibilization.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760301709
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