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  • 1
    Electronic Resource
    Electronic Resource
    Rotational spin-glass properties of nearly ferromagnetic Tb0.15Y0.85Zn : 35th annual conference on magnetism and magnetic materials San Diego, California (USA) 29 Oct − 1 Nov 1990 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5243-5245 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For this cubic pseudobinary compound, the bifurcation of the magnetization (M) vs temperature for warming and cooling in low fields (after zero-field cooling) indicates a spin-glass freezing point (Tg) of ∼20 K. Isotherms of M vs cooling field show zero spontaneous moments down to 4.2 K but an initial susceptibility that almost diverges below Tg〈sbxs〉. From rotational measurements of M as a vector in a fixed field (H) at 4.2 K, the anisotropy field produced by field cooling (HK) is found to turn rigidly with the sample for H below ∼1 kOe. At higher H, HK rotates up to some angle relative to H and then stays fixed as the sample continues to turn, thus exhibiting a frictional rotation relative to the sample. Nevertheless, HK remains sizeable in magnitude (∼12 kOe). Comparisons are made with analogous results for isostructural (Tb, Y) Ag, where spin-glass order coexists with antiferromagnetism, as well as for various prototypal spin-glass alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348092
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  • 2
    Electronic Resource
    Electronic Resource
    Alteration of heme axial ligands in hemoglobin by organic solvents analyzed by CD, FTIR and XANES techniques (1991)
    s.l. : American Chemical Society
    Biochemistry 30 (1991), S. 2804-2810 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00225a010
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  • 3
    Electronic Resource
    Electronic Resource
    Research and Development in Algeria (1991)
    Oxford, UK : Blackwell Publishing Ltd
    R & D management 21 (1991), S. 0 
    Details
    ISSN: 1467-9310
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Economics
    Notes: Since 1971, that is nine years after gaining its independence, Algeria has among some Third World countries formulated an ambitious Science and Technology (S&T) Policy. In the last few years, the relevant administrative structure has been completed by installing a centralised body at the highest level. Policy itself has changed very little, and remained in some aspects well behind developments in the structure. In this paper, the author intends to consider the evolution of both structure and policy of Algeria's research and development (R&D); and the extent of their coherence or harmony and their linkages with industry.Even though structure and policy are the key factors affecting R&D effectiveness of a country, no significant success could be achieved without strengthening the relevant network allowing for the technical competence to be used effectively. Hence, the main theme of the paper concentrates on Algeria's need to review its R&D system to allow both structure and policy to be effective or cause relevant activities to be integrated within the production system, build better technological capabilities, and work for a more efficient industrial development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1467-9310.1991.tb00730.x
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  • 4
    Electronic Resource
    Electronic Resource
    Femtosecond time-resolved refractive index changes in CdS0.75Se0.25 and CdS (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1878-1880 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A pump-probe, light by light deflection technique employing 120 fs pulses at λ=620 nm has been used to measure the temporal and irradiance (I) dependence of the refractive index (n) in 100-μm-thick single crystals of CdS0.75Se0.25 and CdS at 295 K. For I〈3 GW/cm2 only instantaneous negative changes in n are observed and are attributed to Stark and two-photon resonance effects while for higher I negative changes with onset times of approximately 2 ps are attributed to the cooling of two-photon generated carriers. For I(approximately-greater-than)30 GW/cm2 a partial recovery of n occurs within 10 ps and is attributed to possible threshold dependent recombination processes. The variation of probe-beam deflection with pump irradiance has been determined for different probe delays and related to two photon absorption of the pump beam.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106175
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  • 5
    Electronic Resource
    Electronic Resource
    Vasoactive Intestinal Polypeptide (VIP) in Asthma (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 629 (1991), 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.1749-6632.1991.tb37985.x
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  • 6
    Electronic Resource
    Electronic Resource
    Cadmium and membrane ion transport in a French urban male population (1991)
    Springer
    Bulletin of environmental contamination and toxicology 47 (1991), S. 850-857 
    Details
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01689515
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis of certain pyrrolo[2,3-b]pyridine-5-carboxylic acid derivatives as potential antimicrobial agents (1991)
    Springer
    Monatshefte für Chemie 122 (1991), S. 725-730 
    Details
    ISSN: 1434-4475
    Keywords: Synthesis ; Pyrrolo[2,3-b]pyridine ; Cyclization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Synthese von neuen 1-Benzyl-7-alkyl-2,3-dimethyl-4-oxopyrrolo[2,3-b]pyridin-5-carbonsäuren durch Verwendung von 5,6-Dimethyl-2,4-dioxopyrrolo[2,3-d][1,3]oxazinen als Ausgangsmaterial wird beschrieben. Die antimikrobielle Aktivität dieser Substanzen wurde geprüft.
    Notes: Summary A synthetic approach to new 1-benzyl-7-alkyl-2,3-dimethyl-4-oxopyrrolo[2,3-b]pyridine-5-carboxylic acids using 5,6-dimethyl-2,4-dioxopyrrolo[2,3-d][1,3]oxazine as the starting material is reported. The antimicrobial activity of these compound is reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811472
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic-field dependence of hydrogenic impurity states in a quantum well wire (1991)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 13 (1991), S. 165-168 
    Details
    ISSN: 0392-6737
    Keywords: Surface and interface electron states
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The binding energy for on-centre impurities in a rectangular quantum well wire is calculated as a function of the width of the wire and perpendicular magnetic field. The results for zero-magnetic-field case are in perfect agreement with previous calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02463992
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  • 9
    Electronic Resource
    Electronic Resource
    The role of copper-chromium oxide catalysts in the thermal decomposition of ammonium perchlorate (1991)
    Springer
    Journal of thermal analysis and calorimetry 37 (1991), S. 959-967 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels DTA, Röntgendiffraktion und elektrischer LeitfÄhigkeit wurden die katalytischen Wirkungen von versetzten oder gemischten CuO-Cr2O3 Oxiden auf die thermische Zersetzung von Ammoniumperchlorat (AP) untersucht. Die erhaltenen Ergebnisse zeigen, da\ die Abnahme an Defektelektronen von CuO-Katalysator, versetzt mit 1 mol% Cr3+, seine AktivitÄt vermindern, wÄhrend ein entgegengesetzter Effekt bei Cr2O3 beobachtet wird, das mit 1 mol% Cu2+ versetzt ist. Durch Erhöhung der Konzentrationen beider Oxide zeigt der Katalysator bei der Zersetzung von AP die grö\te AktivitÄt bei einem Cr3+-Gehalt von 70 mol%. Mittels Röntgendiffraktion konnte bei dieser Zusammensetzung die Existenz von CuCr2O4 gezeigt werden. Die AktivitÄt dieser Spinellstruktur wurde durch einen Hüpfmechanismus zwischen Cr3+/Cr4+-aktiven Stellen erklÄrt. Weiterhin wurden die Aktivierungsenergien von verschiedenen Zersetzungsstufen von AP mit und ohne Katalysatoren berechnet.
    Notes: Abstract The catalytic effects of doped or mixed CuO-Cr2O3 oxides on the thermal decomposition of ammonium perchlorate (AP) were investigated by using DTA, electrical conductivity and X-ray diffraction techniques. The results obtained revealed that the decrease in the defect electron of CuO catalyst doped with 1 at.% Cr3+ inhibited its activity, while the opposite effect was observed when Cr2O3 was doped with 1 at.% Cu2+. On increase of the concentrations of both oxides, the catalyst containing 70 at.% Cr3+ was found to be the most active during the decomposition of AP. The existence of CuCr2O4 at this ratio was demonstrated by X-ray diffraction. The activity of this spinel was explained on the basis of a hopping mechanism between Cr3+/Cr4+ active sites. Finally, the activation energies of different decomposition stages of AP alone and mixed with catalysts were calculated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01932794
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal studies of some mixed complexes of Mn(II) with picrate and nitrogen donors (1991)
    Springer
    Journal of thermal analysis and calorimetry 37 (1991), S. 2473-2481 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels Thermogravimetrie wurde die thermische Zersetzung von neun Mn(II)-Mischligandenkomplexen mit Pikrat und monooder dizahnigen Stickstoffliganden untersucht. Die Kinetik der Zersetzung wurde mittels der Coats-Redfern und der Horowitz-Metzger-Gleichungen untersucht; in jedem Falle handelt es sich um eine Kinetik erster Ordnung. Die Aktivierungsenergie und andere kinetische Parameter wurden berechnet. Der Mechanismus der Zersetzungsreaktion zeigt für alle untersuchten Verbindungen einen ähnlichen Charakter. Anhand der TG-Kurven wurde beobachtet, daß bei der Zersetzung der Komplexe durch Substitution des Pikrates in die inneren Koordinationssphäre Zwischenprodukte mit der Koordinationszahl sechs entstehen. Diese Intermediäre zersetzen sich über Mn(II)-pikrat zu Mn2O3.
    Notes: Abstract The thermal decompositions of nine mixed ligand complexes of Mn(II) containing picrate and mono- or bidentate nitrogen ligands were studied by thermogravimetry. The kinetics of decomposition were examined by using the Coats-Redfern and Horowitz-Metzger equations; the decomposition was in all cases of the first order. The activation energies and other kinetic parameters were computed. The decomposition mechanisms exhibited a similar character for all the studied compounds. It was observed from the TG curves that the complexes decomposed to give six-coordinate intermediates, formed from substitution of the picrate into the inner coordination sphere. These intermediates decomposed to Mn(II) picrate and finally to Mn2O3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01912794
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