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  • Articles  (12)
  • Chemistry  (8)
  • Chlorophyta  (1)
  • Effective mass andg factors  (1)
  • Engineering General
  • Nitrate
  • 1990-1994  (12)
  • 1993  (5)
  • 1991  (3)
  • 1990  (4)
  • 1
    Electronic Resource
    Electronic Resource
    A simple analysis of the einstein relation in bismuth under different physical conditions (1993)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 15 (1993), S. 39-58 
    Details
    ISSN: 0392-6737
    Keywords: Electron density of states determinations ; Effective mass andg factors ; Band structure of crystalline semiconductor compounds and insulators
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have studied the Einstein relation of the diffusivity-mobility ratio of the carriers in Bi in accordance with the McClure and Choi, the hybrid, the Cohen, the Lax and the ellipsoidal parabolic energy band models under magnetic quantization, cross-field configuration, quantum wells, electric-field-aided quantum wells, quantum wells under cross-field configuration, quantumwell wires, electrifield-aided quantum well wires and quantum well wires under cross-field configurations, respectively. The Einstein relation varies with various physical variables in different manners which are totally band structure dependent. We have also suggested an experimental method of determining the diffusivity-to-mobility ratio in degenerate materials having arbitrary dispersion laws.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02455849
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  • 2
    Electronic Resource
    Electronic Resource
    Phytoplankton of Ogelube Lake, Opi, Anambra State, Nigeria (1990)
    Springer
    Hydrobiologia 199 (1990), S. 81-86 
    Details
    ISSN: 1573-5117
    Keywords: Chlorophyta ; Desmidiales ; Clorococcales ; new records ; West Africa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ogelube, a small, shallow natural lake at Opi, a township near the University of Nigeria's Nsukka campus yielded 231 algal taxa. Most belonged to the Desmidiales, dominated by Cosmarium, and to the Chlorococcales dominated by Scenedesmus, giving 73 taxa new to West Africa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007836
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  • 3
    Electronic Resource
    Electronic Resource
    Nitrate distribution and accumulation in an Ustochrept soil profile in a long term fertilizer experiment (1991)
    Springer
    Nutrient cycling in agroecosystems 28 (1991), S. 173-177 
    Details
    ISSN: 1573-0867
    Keywords: Nitrate ; nitrogen rates ; ground water contamination ; NPK fertilizers ; apparent N recovery ; farm yard manure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Distribution and accumulation of NO3—N, down to 210 cm depth, in the soil profile of a long term fertilizer experiment were studied after 16 cycles of cropping (maize-wheat-fodder cowpea). The application of fertilizer N without P and K or in combination with only P resulted in higher NO3—N concentration in the soil profile than the application of N with P and K. With an annual application of 320 kg N ha−1 alone, a peak in NO3—N accumulation occurred at 135 cm soil depth. However, with the application of NPK, no peak in NO3—N distribution was discernible and its content at most of the sampling depths was either less than or equal to N and NP treatments. The annual application of 10 tons farm yard manure (FYM) per ha along with NPK resulted in a relatively lower NO3—N content in the sub soil. The amount of NO3—N accumulation in the soil profile decreased as the cumulative N uptake by the crops increased. Application of fertilizer amounts greater than that of the recommended (100% NPK) resulted in low percent N recoveries in crops and greater NO3—N accumulation in the soil profile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01049747
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  • 4
    Electronic Resource
    Electronic Resource
    Phenomenological model for the unified studies of different physical properties of polymers (1993)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 207 (1993), S. 9-21 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wird ein phänomenologisches Modell vorgestellt, mit dem sich das Entstehen starker Anisotropien der physikalischen Eigenschaften semikristalliner Polymerer nach einachsigem Verstrecken beschreiben 1äßt. Dieses Modell führt die Temperatur als expliziten Parameter in die Orientierungsfunktion ein. Es enthält zwei frei wählbare Parameter, die für jedes Polymere durch Anpassen der experimentellen Daten der Doppelbrechung als Funktion des Verstreckverhältnisses bei einer bestimmten Temperatur ermittelt werden konnen. Die berechneten Werte für Elastizitätsmodul, thermische Leitfähigkeit und Expansibilität parallel und senkrecht zur Streckrichtung stimmen in einem wäiten Bereich des Verstreckverhältnisses und der Temperatur mit den experimentellen Ergebnissen gut überein.
    Notes: A phenomenological model has been proposed to understand the development of strong anisotropy in physical properties of semicrystalline polymers on uniaxial drawing. The proposed model introduces temperature as an explicit parameter in the orientation function. The model contains two free parameters for each polymer which can be evaluated by fitting the experimental data on birefringence versus draw ratio at a particular temperature. The calculated values of elastic moduli, thermal conductivity and expansibility along and perpendicular to the drawing direction over the entire range of draw ratio and a wide range of temperature are in good agreement with experimental values.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1993.052070102
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis and evaluation of a polyimide containing carbazole and naphthalene moiety (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 3795-3800 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080281322
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  • 6
    Electronic Resource
    Electronic Resource
    Production, purification, and characterization of xylanase from a hyperxylanolytic mutant of Aspergillus ochraceus (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 244-251 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Enhancement of the productivity of xylanase and β-xy-losidase of Aspergillus ochraceus was investigated by multistep mutagenesis. The spores of the wild strain were subjected to UV and N-methyl-N-nitro-N-nitro-soguanidine (NTG). The hyperxylanolytic mutant (NG-13), which showed good clearing on the surface of the xylan-agar plate, secretes xylanase and β-xylosidase at high levels during growth on commercial xylan and on agricultural wastes. Both liquid and solid state cultures were employed in the study for enzyme production. The xylanase from NG-13 was purified to homogeneity by ammonium sulfate precipitation and gel filtration. This purified enzyme showed a pH optimum of 6.0 and was stable in the range of pH 5 to 10. Prolonged stability of the enzyme was observed at 45°C though its activity was maximal at 50°C. The molecular weight of the enzyme was estimated to be 4.3 × 104 by SDS-polyacrylamide gel electrophoresis and 5 × 104 by gel filtration on Sephadex G-75. The kinetic data showed that the Km and Vmax values for xylan were 1 × 10-3M and 19.6 μmol/ min/mg protein, respectively. The enzyme was both more active and thermostable in the presence of K+and was inactivated by thiol reagents such as Hg2+, p-hydroxymercuribenzoate (PHMB), 3′, 5′-dithiobis (2′-nitrobenzoic acid) (DTNB), and N-ethylmaleimide (NEM).
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350305
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  • 7
    Electronic Resource
    Electronic Resource
    Phosphoric acid cation exchange resins from chemically modified polyvinyl chloride (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 40 (1990), S. 1703-1710 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: PVC modified by Cl displacement reaction with meta-aminophenol (MAP), bisphenol A (BISA), and phenolphthalein (PHEN) has been converted into phosphoric acid cation exchange resins. These resins have been characterized in regard to their structure, ion exchange properties, and thermal stability. The ion exchange capacities fall into the range 5.5-8.0 (meq/g) for the resins. The overall thermal stability is considerably higher than that for the corresponding sulfonic acid resins, as well as for the PVC-MAP, PVC-BIS A, and PVC-PHEN condensates. The resins exhibit ca. 4-6% capacity losses under isothermal hydrolytic cleavage at 100°C for 24 h.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070400924
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis and thermal stability, dielectric and conductivity characteristics of some aromatic anhydride-modified carbazole polymers (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 1989-1995 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: Copolycondensates have been prepared from carbazole, poly(N-vinylcarbazole) and various aromatic anhydrides, e.g., phthalic anhydride, trimellitic acid anhydride, pyromellitic dianhydride, naphthalene tetracarboxylic dianhydride, and benzophenone tetracarboxylic dianhydride in presence of the Friedel-Crafts catalyst anhydrous zinc chloride at high temperature. The polymers have been characterized by elemental analyses and IR spectroscopy. Thermal stabilities, dielectric, and conductivity behaviors of these polymers have also been evaluated and it has been observed that these properties show interesting differences depending upon the nature of the anhydride.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420724
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal characteristics of iron(III), cobalt(II), and copper(II) complexes of dipyridylamine anchored on polystyrene-divinylbenzene copolymer (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 1485-1492 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: Polystyrene-divinylbenzene (PS-DVB) (partially chloromethylated) has been modified by anchoring dipyridylamine (DPA) followed by subsequent complexation with Fe(III), Co(II), and Cu(II). Analytical and spectroscopic evidence has been presented to confirm the attachment of the metal-dipyridyl complex on the PS-DVB matrix. All the metal-loaded polymers exhibit appreciable improvement in thermal stability relative to the base polymer, the initial decomposition temperature and stability order being PS-DVB-DPA-Cu(315°C) 〉 PS-DVB-DPA-Fe(II) (310°C) 〉 PS-DVB-DPA-Co (300°C) 〉 PS-DVB-DPA (280°C) = PS-DVB.DTA studies reveal exothermic peaks between 300 and 380°C, 420 and 440°C, and 500 and 700°C, which are ascribable to the exothermic cleavage of the PS-DVB-DPA matrix. The glass transition temperatures of the modified polymers do not reveal any characteristic difference from the corresponding value for the base polymer. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070500901
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal stability, morphological, dielectric, and conductivity characteristics of pyrrole modified poly-N-vinyl carbazole (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 49 (1993), S. 2189-2196 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: N-vinyl-Carbazole (NVC) has been polymerized in the presence of pyrrole (PY) by anhydrous ferric chloride. The copolymer has been characterized by IR Spectroscopy. Thermal stability of P(PY-NVC) is intermediate between that of PNVC and PPY, respectively. DSC reveals a single glass transition break at 180-200°C for P(PY-NVC), which is higher than the Tg for polypyrrole (∼ 165°C), but is lower than that for PNVC (∼ 227°C). The XRD analysis reveals PPY to be totally amorphous and shows the percent crystallinity for P(PY-NVC) to be less than that of PNVC. Dielectric constants of the polymers follow the trend: PPY 〉 P(PY-NVC) 〉 PNVC, and fall sharply with the applied frequency to a limiting value. The polymers are characterized by a broad dielectric relaxation. DC conductivity is dependent on temperature and FeCl3/polymer mole ratio and at a particular temperature follows the trend: PPY 〉 P(PY-NVC) 〉 PNVC. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070491215
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