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  • 1
    Electronic Resource
    Electronic Resource
    Morphologie et propriétés optiques des cristaux de lysozyme de poule de type quadratique et orthorhombique (1974)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 30 (1974), S. 645-648 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Large crystals of hen egg-white (HEW) lysozyme, both tetragonal and orthorhombic, have been studied with a goniometer and optical methods. As the crystals are particularly stable, some of their optical properties have been measured, mainly the refractive indices determined from reflectance measurements under a photometric microscope. Orthorhombic HEW lysozyme: crystals show the faces (010), (011) and (110). Refractive indices n[001] = ng = 1-562 to 1.547 (λ = 480-640 nm); n[100] = nm = l.560 to 1.544; n[010] = np = 1.550 to 1.532. Maximum birefringence 0.013 (λ) = 589 nm). Optic axial angle 2V =48 to 51°. Tetragonal HEW lysozyme: crystals formed by the association of a tetragonal {110} prism and a {101} tetragonal bipyramid. Refractive indices n[001] = nc and n[100] = no, with an aging phenomenon in these crystals, ne varying between 1-580 and 1.545, no between 1.575 and 1.538 (λ = 589 nm). Maximum birefringence 0.007. HEW lysozyme crystals are examples of good-quality protein crystals. Their refractive indices are surprisingly high for organic substances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739474001550
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  • 2
    Electronic Resource
    Electronic Resource
    RbNbB2O6: structure de la maille multiple et propriétés optiques (1976)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 32 (1976), S. 2211-2215 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567740876007395
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  • 3
    Electronic Resource
    Electronic Resource
    Mitteilungen (1983)
    Springer
    Mineralogy and petrology 32 (1983), S. 79-81 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081546
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  • 4
    Electronic Resource
    Electronic Resource
    Étude de spinelles de synthèse de la série Mg(Cr x Al2−x )O4 et de chromites naturelles par microsonde Raman-Laser (1983)
    Springer
    Mineralogy and petrology 32 (1983), S. 171-185 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Summary A possibility of studying the Raman effect of minerals “in situ” is now offered by the Raman microprobe which presents the two following characteristics: the ability to produce a point-size illurnination: the size of the laser beam impact may be as narrow as 1 μm2; a wide aperture optics permitting to catch the diffuse light. The spectra obtained from synthetic spinels belonging to the series Mg(Cr x Al2−x )O4 display noticeable shifts for some frequency bands and particularly a major shift of the high frequency band corresponding to the A1g mode. This displacement is included between 685 cm−1 for the Cr end-member and 770 cm−1 for the Al one. An identical phenomenon is shown by the spectra obtained from natural chromites of general formula (Mg,Fe2+)(Al, Cr, Fe3+)2O4. Thus one correlate the location of this high frequency band with the ratio Cr/Cr+Al of each member belonging to the synthetic spinels serie and each natural chromite sample. On the ground of the hypothesis that spinels belong to theFd3m spatial group, the group theory expects five Raman active vibrational modes: A1g +E g +3T2g . These expectations in agreement with the experimentation on the natural MgAl2O4 spinel, but the spectra of synthetic spinels as well as those of natural chromites, show a number of bands greater than five. Two hypothesis are given to explain the existence of some of those supplementary bands.
    Notes: Résumé La microsonde Raman-Laser permet d'étudier l'effet Raman des minéraux “in situ” et ce grâce à ses deux caractéristiques principales. la possibilité de produire un éclairement ponctuel, la surface d'impact du faisceau laser est de l'ordre du μm2; un objectif à grande ouverture numérique qui collecte la lumiêre diffusée. Les spectres obtenus à partir de spinelles de synthèse de la série Mg(Cr x Al2−x )O4 montrent un phénomène de variation de fréquence pour un certain nombre de bandes et plus particulièrement pour la bande de haute fréquence correspondant au mode A1g. En ce qui conceme cette dernière, la variation est comprise entre 685 cm−1 pour le terme purement chromifère et 770 cm−1 pour le terme purement alumineux. Un phénomène identique se produit dans les spectres obtenus à partir de chromites naturelles de formule générale (Mg, Fe2+) (Al, Cr, Fe3+)2O4. Ainsi la position de la bande de haute fréquence est corrélée avec le rapport Cr/Cr+Al de chaque terme appartenant soit à la série des spinelles de synthèse soit aux chromites naturelles. En partant de l'hypothèse que les spinelles appartiennent au groupe spatialFd3m, la théorie des groupes prévoit cinq modes actifs en Raman, à savoir: A1g +E g +3T2g . C'est ce que nous constatons pour le spinelle alumineux naturel MgAl2O4, mais les membres de la série Mg(Cr x Al2−x )O4 aussi bien d'ailleurs que les chromites naturelles présentent un nombre de bandes supérieur à cinq. Deux hypothèses sont formulées pour expliquer l'existence de certaines de ces bandes supplémentaires.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081108
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  • 5
    Electronic Resource
    Electronic Resource
    Comportement du Nickel Lors de L'Altération des Roches Nickélifères (1984)
    Springer
    Mineralium deposita 19 (1984), S. 118-122 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract Infrared and visible absorption spectra of inorganic silico-magnesian gels were measured in order to study the nickel evolution during the meteoric alteration of rocks. The samples are obtained by mixing solution of nickel, magnesium sulfate with a sodium silicate solution in variable proportions. Measurement of spectra was carried out on sample after they were air dried. These spectra show bands which point that nickel atoms are inserted in a site configuration similar with the lizardite configuration. This results suggest that silico-magnesian gels observed in the neocaledonians minerals could be considered as proto-serpentines. Garnieritics minerals are obtained by cristallization of those proto-serpentines. Two pictures of migration of nickel are proposed, one for the nickeliferous peridotite, other for the serpentine.
    Notes: Resumé Afin de déterminer le comportement du nickel lors de l'altération météorique des roches nickélifères, une étude en spectroscopie d'absorption infrarouge et visible a été réalisée sur des gels silico-magnésiens synthétiques enrichis en nickel. Les échantillons sont obtenus par coprécipitation en mettant en présence une solution de sulfate de nickel et de magnésium et une solution de silicate de sodium. Les spectres, enregistrés à partir d'échantillons séchés à l'air, présentent des bandes d'absorption qui indiquent que le nickel est dans une configuration cristallochimique semblable à celle qu'il possède dans les lizardites. Ces résultats confirment l'hypothèse selon laquelle les fractions silicatées riches en nickel des minerais de type néocalédoniens sont issues, par cristallisation, de gels silicomagnésiens, considérés comme des proto-serpentines. Ils permettent d'envisager deux schémas de cheminement du nickel selon que l'on part d'une péridotite nickélifère ou d'une serpentine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204670
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  • 6
    Electronic Resource
    Electronic Resource
    Signatures of Ni2+ and Fe3+ in the optical spectra of limonitic ore from new caledonia: Application to the determination of the nickel content (1981)
    Springer
    Mineralium deposita 16 (1981), S. 357-373 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract A spectrometric study has been made over the range from 400 to 1500 nm on powdered specimens of saprolitic, nickel-bearing ore minerals from New Caledonia; analysis of the absorption spectra enables a distinction to be made between features due to Fe3+ and those due to Ni2+. Measurement of diffuse reflectance in the visible range makes it possible to estimate (to about 2% relative) the amount of nickel in the saprolites. The simplicity of the method and the fact that it is applied to powdered material enable these spectral characteristics of nickel to be used in prospecting for nickel or in the estimation of resources, eventually by remote-sensing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01798963
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  • 7
    Electronic Resource
    Electronic Resource
    Dosage rapide du magnésium dans les ilménites par microréflectométrie (1971)
    Springer
    Mineralium deposita 6 (1971), S. 34-40 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé Une méthode rapide et un appareil simple sont proposés pour la détermination de la teneur en magnésium d'échantillons microscopiques d'ilménites. Fondée sur la proportionnalité entre la réflectance et le pourcentage de MgO des termes de la série ilménite-geikielite, cette méthode est précise, rapide, peu onéreuse et non destructive. Servie par un appareil très simple, le «magnésiomètre» (Brevet B. R. G. M. numéro 1553 106), utilisable dans un laboratoire de terrain, elle peut être pratiquée par un personnel non spécialisé. Cet appareil trouvera des applications dans la détection des ilménites provenant de kimberlites, et de manière plus générale, dans tout autre domaine où la variation de composition chimique d'un matériau entraîne une variation proportionnelle des propriétés optiques, tel qu'en pétrologie, minéralogie, métallogénie et métallurgie.
    Notes: Abstract A rapid method with simple apparatus is proposed for the determination of the magnesium content of microscopic crystals of ilmenite. The method is based upon the proportional relation existing in the series ilménite-geikielite between the percentage of MgO and the reflectance. The method is precise, rapid, trouble-free and non-destructive. A very simple apparatus, the “magnesiometer” (Brevet B. R. G. M. No. 1553 106), can be used in a field laboratory by operators without special training. This apparatus can be used in the detection of ilmenites coming from kimberlites. It also has a very general application to any problem where the variation of the optical properties of a substance is proportional to the variation of its chemical composition, as in petrology, mineralogy, ore mineralogy and metallurgy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00207115
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  • 8
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    Parametrisable skeletonization of binary and multi-level images (1990)
    Elsevier
    Details
    Publication Date: 1990-01-01
    Print ISSN: 0167-8655
    Electronic ISSN: 1872-7344
    Topics: Computer Science
    Published by Elsevier
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  • 9
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    Visible spectrometric indices of hematite (Hm) and goethite (Gt) content in lateritic soils: The application of a Thematic Mapper (TM) image for soil-mapping in Brasilia, Brazil (1997)
    Taylor & Francis
    Details
    Publication Date: 1997-09-01
    Print ISSN: 0143-1161
    Electronic ISSN: 1366-5901
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Taylor & Francis
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  • 10
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    Extraction et analyse automatiques d'un réseau hiérarchisé de talwegs. Application à un modèle numérique de terrain dérivé d'un couple stéréoscopique SPOT (1992)
    Taylor & Francis
    Details
    Publication Date: 1992-01-01
    Print ISSN: 0143-1161
    Electronic ISSN: 1366-5901
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Taylor & Francis
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