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  • 1
    Electronic Resource
    Electronic Resource
    Use of CO as probe molecule for characterization of mixed Ru-Ni sulphide phases supported over alumina (1992)
    Springer
    Catalysis letters 13 (1992), S. 213-219 
    Details
    ISSN: 1572-879X
    Keywords: Nickel ; ruthenium ; sulphide ; CO adsorption ; hydrogenation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Infrared spectroscopy was used to characterize mixed ruthenium-nickel sulphides prepared by step-wise impregnation over alumina and further sulphidation. The hydrogenation of biphenyl was compared over samples containing different amounts of nickel and ruthenium and a large increase was observed for a catalyst with an atomic Ni /(Ni + Ru) ratio near 0.4. Infrared spectra of adsorbed CO indicate that the increase in catalytic activity is ascribed to the presence of a very large number of Ru-Ni sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00770993
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  • 2
    Electronic Resource
    Electronic Resource
    Garnet pyroxenite and eclogite in the Bohemian Massif: geochemical evidence for Variscan recycling of subducted lithosphere (1995)
    Springer
    International journal of earth sciences 84 (1995), S. 489-505 
    Details
    ISSN: 1437-3262
    Keywords: Bohemian Massif ; Variscan ; Geochemistry ; Garnet pyroxenite ; Eclogite ; Lithosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract High-temperature, high-pressure eclogite and garnet pyroxenite occur as lenses in garnet peridotite bodies of the Gföhl nappe in the Bohemian Massif. The high-pressure assemblages formed in the mantle and are important for allowing investigations of mantle compositions and processes. Eclogite is distinguished from garnet pyroxenite on the basis of elemental composition, with mg number 〈80, Na2O 〉 0.75 wt.%, Cr2O3 〈 0.15 wt.% and Ni 〈 400 ppm. Considerable scatter in two-element variation diagrams and the common modal layering of some eclogite bodies indicate the importance of crystal accumulation in eclogite and garnet pyroxenite petrogenesis. A wide range in isotopic composition of clinopyroxene separates [εNd, +5.4 to −6.0; (87Sr/86Sr)i, 0.70314–0.71445; δ18OSMOW, 3.8–5.8%o] requires that subducted oceanic crust is a component in some melts from which eclogite and garnet pyroxenite crystallized. Variscan Sm-Nd ages were obtained for garnet-clinopyroxene pairs from Dobešovice eclogite (338 Ma), Úhrov eclogite (344 Ma) and Nové Dvory garnet pyroxenite (343 Ma). Gföhl eclogite and garnet pyroxenite formed by high-pressure crystal accumulation (±trapped melt) from transient melts in the lithosphere, and the source of such melts was subducted, hydrothermally altered oceanic crust, including subducted sediments. Much of the chemical variation in the eclogites can be explained by simple fractional crystallization, whereas variation in the pyroxenites indicates fractional crystallization accompanied by some assimilation of the peridotite host.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00284516
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  • 3
    Electronic Resource
    Electronic Resource
    Image quality and dose in spiral computed tomography (1996)
    Springer
    European radiology 6 (1996), S. 485-488 
    Details
    ISSN: 1432-1084
    Keywords: Computed tomography ; Helical technology ; Image quality ; Radiation exposure ; Dosimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Image quality and dose produced by a spiral CT with various pitch values were investigated on the basis of test-object images and measurements of CT dose indexes. No major difference in image quality or dose was observed when comparing sequential and spiral mode acquisition with a pitch of one. Increase in pitch value produces a loss of contrast which leads to a loss of detectability. Nevertheless, in realistic protocls the image quality in the transverse plane remains acceptable up to pitch values of 1.3 – 1.6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00182477
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  • 4
    Electronic Resource
    Electronic Resource
    Application of the thermoluminescent dosimetry to a pion beam (1979)
    Springer
    Radiation and environmental biophysics 16 (1979), S. 225-229 
    Details
    ISSN: 1432-2099
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Summary The thermoluminescent dosimetry is currently applied to radiation therapy in order to measure dose distributions on phantoms or to control the dose in vivo for special procedures or critical organs. The application of this method to the SIN's (Switzerland) pion beam has been studied. Measurements have been made on the following thermoluminescent materials:7LiF,6LiF, Li(nat)F, Li2B4O7, CaF2 : Mn, and CaF2 : Dy. Except for the last one a reduction (10%) of the sensitivity of the phosphors has been observed in the peak relative to the plateau region. An increase of the6LiF sensitivity relative to that of7LiF has been pointed out due to the neutron background through the (n,α) reaction on6Li. Glow curves of the LiF phosphors have been measured. A reduction (5%) of the intensities of peak 3 and 4 relative to peak 5 has been observed for irradiation in the peak region. This effect however can't be used in order to localize the dosimeter in the beam because the intensity of the thermoluminescence peaks shows a larger variability in a batch of dosimeters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01358282
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  • 5
    Electronic Resource
    Electronic Resource
    Radiation doses delivered to radiologists during contrast-enhanced helical-CT examinations (1999)
    Springer
    European radiology 9 (1999), S. 1919-1922 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Helical CT ; Power injector ; Radiation ; Protective device
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. This work monitors the radiation doses to a radiologist during supervision of automatic contrast media injections during helical-CT examinations of the chest and abdomen. Forty consecutive standard helical-CT examinations of adult's chest and/or abdomen were monitored with five dosimeters worn by the radiologist supervising the entire injection with the hand on the injection site. Mean doses per examination measured at chest, thyroid gland, and hand levels were 11, 16, and 130 μGy, respectively, during chest examinations, and 5, 7, and 55 μGy during abdominal examinations. According to the high number of CT examinations performed, wearing lead apron, special lead glove protection, and thyroid shield is highly recommended.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050949
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  • 6
    Electronic Resource
    Electronic Resource
    Ternary feldspar thermometry in granulites from the Oaxacan Complex, Mexico (1985)
    Springer
    Contributions to mineralogy and petrology 89 (1985), S. 215-225 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Coexisting feldspars from across 2,000 km2 of the granulite facies Oaxacan Complex, southern Mexico exhibit variable amounts of solid solution from nearly binary (Ab-An and Ab-Or) to substantially ternary (Ab-An-Or). Reintegrated analyses of 21 coarsely exsolved perthite (AF)-plagioclase (PL) pairs yield AF=Or30–63 Ab30–56An2–15 and PL=Or1–2Ab70–84An11–28. These data have been used to test existing two feldspar geothermometers for this extended composition range. For all compositions, temperature estimates show relatively little spread in value (660° to 795° C, 7 kbar) using the Haselton et al. (1983) calibration (HHHR). These temperatures are in fair agreement with estimates of 750±40° C for feldspar pairs with nearly binary compositions using the Stormer (1975) thermometer (STO). However, STO temperatures increase significantly (to 990° C) with increasing ternary solid solution in AF, suggesting that thermometers derived for binary systems are inaccurate for ternary compositions. Isotherms drawn from HHHR which take into account variable anorthite solution in alkali feldspar show that estimated temperature decreased by 50–100° C for each 5 mole percent anorthite in alkali feldspar. Experimentally determined solvus relations (Seck 1971) require feldspars with significant ternary solid solution to have crystallized or to have equilibrated at higher temperature than feldspars with more binary compositions. However, petrographic and field relations of ternary and binary feldspars in the Oaxacan Complex suggest they were all equilibrated at similar metamorphic pressures and temperatures and do not support a model where ternary feldspars have preserved higher premetamorphic temperatures. The composition of coexisting feldspars from other Precambrian granulite-facies terranes are also inconsistent with Seck's (1971) results. Hence, thermometers which fit Seck's solvus relations may not yield accurate temperatures in high grade metamorphic terranes. Parallel tie-lines for ternary and binary feldspars in the Oaxacan Complex and the consistency of inferred temperatures (HHHR) for many granulite terranes suggest that estimation of temperature using tie-line slopes rather than solvus width may yield more accurate results for these samples. Peak metamorphic conditions in the Oaxacan Complex are inferred to have been 730±50° C, 7±1 kbar. Pressure estimates from four garnet-plagioclase barometers show good agreement. Results of feldspar thermometry are consistent with diopside-forsterite equilibria in marbles which restrict T=720–765° C at P=7 kbar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379455
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  • 7
    Electronic Resource
    Electronic Resource
    Ion microprobe analysis of oxygen isotope ratios in quartz from Skye granite: healed micro-cracks, fluid flow, and hydrothermal exchange (1996)
    Springer
    Contributions to mineralogy and petrology 124 (1996), S. 225-234 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Quartz grains in hydrothermally altered granites from the Isle of Skye are highly heterogeneous and not equilibrated in oxygen isotope ratio at the 20 μm scale. Ion microprobe analysis of one grain shows a gradient of 13‰ over 400 μm and a greater range in δ 18O than all quartz previously analyzed on the Isle of Skye. Other crystals from the same outcrop are homogeneous. Digitized cathodoluminescence images reveal patterns of magmatic zoning and brittle fracturing not otherwise detectable. The ion probe analysis correlates low δ 18O values on a micro-scale to one set of healed cracks. Thus, quartz exchanges oxygen isotopes primarily by solution and reprecipitation along fractures, in contrast to more reactive feldspar that appears to exchange from the grain boundary inward. Macroscopic models of isotope exchange are not realistic for these rocks; the flow of hydrothermal fluids was heterogeneous, anisotropic and crack controlled.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050188
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  • 8
    Electronic Resource
    Electronic Resource
    The correlation of reaction and isotope fronts and the mechanism of metamorphic fluid flow (2000)
    Springer
    Contributions to mineralogy and petrology 138 (2000), S. 364-375 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Infiltration of a metabasite sill from Islay, Scotland by an H2O-CO2 fluid caused (1) modification of δ18O and (2) carbonation at the sill margins. Maps of δ18O and reaction progress were constructed from a 20 × 47.7 metre sample grid across the sill. The grid consisted of 300 samples, spaced at m, dm and cm intervals, many of which were analysed for both δ18O and reaction progress. The δ18O was determined by laser fluorination of whole rock silicate powders and reaction progress was determined by rapid field-based measurement of % calcite (“fizz-o-meter”, Skelton et al. 1995). Reaction and isotope fronts outlined tube-like features that emanate from the sill margin and discrete nodes that, although detached from the sill margin in two dimensions, are thought to represent sections through similar tubes in three dimensions. We envisage that these protrusions are the fossil record of metamorphic “fluid pathways” whereby fluid permeated the sill. Isotope and reaction fronts are found to correlate spatially as predicted by a modified form of the chromatographic equation which describes this envisaged geometry, that is where isotopic and reactive transport in the fluid phase are facilitated by advection along specific fluid pathways and transverse diffusion in the surrounding rock. These fluid pathways consist of bundles of anastomosing grain boundary channels or micro-cracks, which are thought to propagate through transient cyclic infiltration, reaction, porosity enhancement and fracturing. This mechanism is self-perpetuating and accentuates random perturbations at the sill margin to form the observed tubes. We argue that this is the earliest stage of the infiltration process which has affected metabasites of the SW Scottish Highlands and that subsequent shear deformation of the reacted rims of these pathways, has caused their re-orientation and juxtaposition to form the reacted sill margins described by Skelton et al. (1995).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050569
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  • 9
    Electronic Resource
    Electronic Resource
    Fluid heterogeneity during granulite facies metamorphism in the Adirondacks: stable isotope evidence (1984)
    Springer
    Contributions to mineralogy and petrology 85 (1984), S. 158-173 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The preservation of premetamorphic, whole-rock oxygen isotope ratios in Adirondack metasediments shows that neither these rocks nor adjacent anorthosites and gneisses have been penetrated by large amounts of externally derived, hot CO2-H2O fluids during granulite facies metamorphism. This conclusion is supported by calculations of the effect of fluid volatilization and exchange and is also independently supported by petrologic and phase equilibria considerations. The data suggest that these rocks were not an open system during metamorphism; that fluid/rock ratios were in many instances between 0.0 and 0.1; that externally derived fluids, as well as fluids derived by metamorphic volatilization, rose along localized channels and were not pervasive; and thus that no single generalization can be applied to metamorphic fluid conditions in the Adirondacks. Analyses of 3 to 4 coexisting minerals from Adirondack marbles show that isotopic equilibrium was attained at the peak of granulite and upper amphibolite facies metamorphism. Thus the isotopic compositions of metamorphic fluids can be inferred from analyses of carbonates and fluid budgets can be constructed. Carbonates from the granulite facies are on average, isotopically similar to those from lower grade or unmetamorphosed limestones of the same age showing that no large isotopic shifts accompanied high grade metamorphism. Equilibrium calculations indicate that small decreases in δ 18O, averaging 1 permil, result from volatilization reactions for Adirondack rock compositions. Additional small differences between amphibolite and granulite facies marbles are due to systematic lithologie differences. The range of Adirondack carbonate δ 18O values (12.3 to 27.2) can be explained by the highly variable isotopic compositions of unmetamorphosed limestones in conjunction with minor 18O and 13C depletions caused by metamorphic volatilization suggesting that many (and possibly most) marbles have closely preserved their premetamorphic isotopic compositions. Such preservation is particularly evident in instances of high δ 18O calcites (25.0 to 27.2), low δ 18O wollastonites (−1.3 to 3.5), and sharp gradients in δ 18O (18 permil/15m between marble and anorthosite, 8 permil/25 m in metasediments, and 6 permil/1 m in skarn). Isotopic exchange is seen across marble-anorthosite and marble-granite contacts only at the scale of a few meters. Small (〈5 m) marble xenoliths are in approximate exchange equilibrium with their hosts, but for larger xenoliths and layers of marble there is no evidence of exchange at distances greater than 10 m from meta-igneous contacts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371706
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  • 10
    Electronic Resource
    Electronic Resource
    Akermanite in the Cascade Slide xenolith and its significance for regional metamorphism in the Adirondacks (1980)
    Springer
    Contributions to mineralogy and petrology 74 (1980), S. 143-152 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Akermanite (Ak90) coexists with monticellite (Mo92) and wollastonite (Wo99) in an unusual calc-silicate xenolith in anorthosite at Cascade Slide in the Adirondack Mountains, New York. Experimental results bearing on the stability of akermanite have been evaluated through calculations based on thermochemical data and by chemical analysis of experimental products (Yoder 1975). A temperature of 750°±30° C and a pressure less than 7 kb are inferred. These estimates are in agreement with the conditions of regional metamorphism previously inferred from other nearby rock types. When errors are considered, all existing data show that the Cascade Slide mineral assemblages last equilibrated at a slightly higher pressure of 7.4±1 kb and at a temperature of 750°±30° C during regional granulite facies metamorphism. The exotic mineralogy at Cascade Slide (akermanite, monticellite, cuspidine and wilkeite) was stabilized by low carbon dioxide fugacity. Posttectonic anorthosite intrusion is ruled out by the absence of a preserved contact aureole.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01132000
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