OH defects in forsterite     

Eugen Libowitzky  Anton Beran 《Physics and Chemistry of Minerals》1995,22(6):387-392

Polarized FTIR spectra of near endmember forsterite single crystals from Pamir, Tadzikistan show the existence of sharp strongly pleochroic absorption bands in the region of the OH stretching fundamental. Bands centered at 3674/3624, 3647/3598 and 3640/ 3592 cm^-1 are attributed to OH dipoles oriented parallel to [100]. An OH band doublet at 3570/3535 cm^-1 shows both, a strong absorption parallel to [100] and a strong component parallel to [001]. On the basis of the pleochroic scheme and under the assumption of vacancies on Si- and M-sites it is proposed that O1 is partially replaced by OH defects pointing to the vacant Si-site. O3 is donator oxygen of OH dipoles lying near the O3-O1 tetrahedral edge or roughly pointing to a vacant M2-site. Also O2 can act as donator oxygen of an OH group oriented along the O2-O3 edge of a vacant M1 octahedron. The splitting of the bands is explained by the presence of Fe²⁺ in cation sites surrounding the OH defects.  相似文献   

Capabilities of radar,sodar and lidar for measuring the structure and motion of the stably stratified atmosphere     

K. A. Browning  D. Beran  M. J. S. Quigley  C. G. Little 《Boundary-Layer Meteorology》1973,5(1-2):195-200

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The laser satellite range measurement at ondřejov observatory     

Pavel Navara  Tomáš Daříček  Karel Hamal  Antonín Novotný  Reviewers B. Chán  R. Rajchl 《Studia Geophysica et Geodaetica》1971,15(3-4):393-395

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Messung des Ultrarot-Pleochroismus von Mineralen. XIII. Der Pleochroismus der OH-Streckfrequenz in Axinit     

Dr. A. Beran 《Mineralogy and Petrology》1971,16(4):281-286

Zusammenfassung Die räumliche Absorptionsfigur für die OH-Streckfrequenz in Axinit (=3,03 ) ist in erster Näherung eine Lemniskate, die um ihre Längsachse rotiert. Die Richtung dieser Achee—und damit die ungefähre Dipolrichtung der OH-Gruppe—liegt unter einem Winkel von etwa 70° zur positiven Richtung derc-Achse geneigt und schließt mit der negativen Richtung dera-Achse einen Winkel von etwa 40° ein.

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Measurement of the infrared-pleochroism in minerals. XIII. The pleochroism of the OH-stretching frequency in axinite

Summary The 3-dimensional absorption figure for the OH-stretching frequency in axinite (=3300 cm^–1) can be described in a first approximation as a lemniscate which rotates around the longer axis. The direction of this rotation axis which corresponds to the approximate direction of the OH-dipoles includes an angle of nearly 70° with the positive direction of thec-axis, and an angle of nearly 40° with the negative direction of thea-axis.

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Herrn Prof. DDr.H. Wieseneder zum 65. Geburtstag gewidmet.  相似文献   

RARE EARTH ELEMENT CONCENTRATIONS IN USGS AND CCRMP IGNEOUS ROCK STANDARDS DETERMINED BY HIGH PERFORMANCE ION CHROMATOGRAPHY     

Ronald T. WATKINS  Anton P. le  ROEX 《Geostandards and Geoanalytical Research》1993,17(1):105-111

Eleven rare earth elements (REE) have been determined in ten USGS and two CCRMP igneous rock standards using high performance ion chromatography. Duplicate analyses of two or more separately prepared aliquots of each sample were undertaken; reproducibility was better than 5% for each of the REE. In most cases, the results compare closely with published REE values for those samples for which the REE are well characterised. Where the results for individual elements are in disagreement with published data, the more erratic patterns yielded by the earlier data when plotted on chondrite-normalised REE diagrams suggest that values determined in this study are of greater accuracy.  相似文献   

Seismic codas on the Earth and the Moon: a comparison     

Anton M. Dainty  M.Nafi Toksöz 《Physics of the Earth and Planetary Interiors》1981,26(4):250-260

The phenomenon of the seismic coda, which is composed of seismic energy delayed by scattering, is seen on both the Earth and the Moon. On the Moon the scattered coda is very large relative to body wave arrivals with a delay of the time of maximum energy, whereas on Earth scattered codas are relatively small and show no delay of the energy maximum. In both cases the form of the coda is controlled by three distance scales, the mean free path L, which is the average distance seismic energy travels before it is scattered, the attenuation distance $\text{x1}$, which is the average distance seismic energy travels before it is attenuated, and the source-receiver distance R. Two coda models are discussed based on these parameters; a strong scattering (diffusion) model, and a weak scattering (single scattering) model. A discussion of the diffusion scattering model indicates that if $\text{x1/L ? 1}$, diffusion scattering is an appropriate model, but if $\text{x1/L ? 1}$, single scattering is the appropriate model, within the appropriate range of R. A survey of the literature indicates that for the frequency range 0.5–10 Hz, diffusion scattering is important in lunar codas, but for the frequency range 1–25 Hz single scattering is important in terrestrial codas. Another important effect of attenuation is the elimination of scattering paths much longer than $\text{x1}$. On the Moon, this means that seismic energy in the coda can only propagate directly in the near-surface strong scattering zone between surface sources and the seismometer for source-seismometer separations of the order of $\text{(x1L)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$; otherwise, scattering is limited to regions near the source and the receiver. On Earth, this effect probably prevents multiple scattering.  相似文献   

Effects of water-soluble fractions of crude oil and dispersants on nitrate generation by sandy beach microfauna     

Beryl Harty  Anton McLachlan 《Marine pollution bulletin》1982,13(8):287-291

Effects on sandy beach microfauna of soluble pollutants, such as might be associated with an oil spill, were investigated in terms of nitrate generation. Nitrate generation by the microfauna in small sand columns in the laboratory was severely inhibited by water-soluble fractions of crude oil, dispersant and oil/dispersant mixtures in order of increasing effects. Short-term effects of such pollutants on nutrient regeneration by exposed sandy beaches are discussed.  相似文献   

MELIMEX,an experimental heavy metal pollution study: Effects of increased heavy metal loads on phytoplankton communities     

René Gächter  Dr. Antonín Máreš 《Aquatic Sciences - Research Across Boundaries》1979,41(2):228-246

Long-term impacts of increased metal loading (Hg, Cu, Cd, Zn and Pb) on phytoplankton communities of large limno-corrals (diameter 12 m, depth 10 m) were studied. Increased metal concentrations initially lowered phytoplankton biomass, as well as species number and photosynthetic activity of phytoplankton. They caused changes in metal speciation and shifts in phytoplankton community structure, favoring less susceptible species. Although adaptation was not sufficient to completely prevent the metal-induced depression of photosynthesis, due to depressed zooplankton grazing, at the end of the experiment even higher phytoplankton densities were observed in the metal-loaded corrals than in the control.  相似文献   

Geochemistry of Karroo dolerite sills in the Calvinia district,Western Cape Province,South Africa     

Anton P. le Roex  David L. Reid 《Contributions to Mineralogy and Petrology》1978,66(4):351-360

Two Karroo dolerite sills display chemical and mineralogical variation compatible with cumulus enrichment. The Blaauwkrans sill is an olivine tholeiite and contains a central zone slightly enriched in olivine, plagioclase and clinopyroxene. The thicker Hangnest sill is a quartz tholeiite and shows evidence of crystal settling and has a lower zone enriched in cumulus orthopyroxene and plagioclase.The two sills differ quite markedly in their trace element compositions, with the Hangnest magma enriched by a factor of two in LIL elements (Rb, Ba, Nb, Zr, Y) relative to the Blaauwkrans magma. The Hangnest magma contained extremely low Ni contents (3–5 ppm), whereas the Blaauwkrans magma contained higher but more normal Ni (100–110ppm). Such contrasting trace element compositions preclude any simple genetic relationship between the two Karroo magmas but they may be related either through a common parent or are derivatives from separate parental magmas.South African Contribution No. 24 to the International Geodynamics Project  相似文献   

Messung des Ultrarot-Pleochroismus von Mineralen. IX. Der Pleochroismus der OH-Streckfrequenz in Titanit     

Dr. A. Beran 《Mineralogy and Petrology》1970,14(1):1-5

Zusammenfassung Die räumliche Absorptionsfigur für die OH-Streckfrequenz in Titanit (=2,90 ) ist in erster Näherung eine Lemniskate, welche um die längere Achse rotiert. Die Richtung der Drehachse — und damit die Richtung der OH-Dipole, die teilweise die O₁-Punktlagen besetzen — fällt ungefähr mit der Schwingungsrichtung von n zusammen.

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Measurement of the infrared-pleochroism in minerals. IX. The pleochroism of the OH-stretching frequency in titanite

Summary The 3-dimensional absorption figure for the OH-stretching frequency in titanite (=2.90 ) can be described in a first approximation as a lemniscate which rotates around the longer axis. The direction of this rotation axis and also the direction of the OH-dipoles, which replace partially the O₁-positions, coincides approximately with n.

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Mit 2 Abbildungen  相似文献