bluuebunny/crossref_metadata_2025 huggingface dataset:
Human Hydroxysteroid (17-β) Dehydrogenase 1 Expression Enhances Estrogen Sensitivity of MCF-7 Breast Cancer Cell Xenografts
Authors: Husen Bettina , Huhtinen Kaisa , Saloniemi Taija , Messinger Josef , Thole Hubert H. , Poutanen Matti
Published: August 2006

Hydroxysteroid (17-β) dehydrogenase 1 (HSD17B1) catalyzes the conversion between estrone (E1) and estradiol (E2). The reaction is reversible in vitro, but the data in cultured cells suggest that E2 production is the predominant reaction in physiological conditions. However, the hypothesis has not been verified in vivo. In the present study, estrogen-dependent MCF-7 human breast cancer cells were stably transfected with an expression plasmid for human HSD17B1. The enzyme efficiently converted E1 to E2 and enhanced the estrogen-dependent growth of cultured MCF-7 cells in the presence of hormonally less active E1. The HSD17B1-expressing cells also formed estrogen-dependent tumors in immunodeficient nude mice. After treating the mice with an appropriate dose of the substrate (E1, 0.1 μmol/kg·d), a marked difference in tumor growth was observed between nontransfected and HSD17B1-transfected MCF-7 cells, mean tumor weights at the end of E1 treatment being 23.2 and 130.4 mg, respectively. Furthermore, estrogen-dependent growth of the HSD17B1-expressing xenografts in the presence of E1 was markedly inhibited by administering 5 μmol/kg·d of a specific HSD17B1 inhibitor. After a 4-wk treatment, the tumor size was reduced by 59.8% as compared with the nontreated tumors, whereas the uterine growth of the mice was not affected by the HSD17B1 inhibitor used. This was in line with the induction of apoptosis of the tumors. The results evidently show that estrogenic response for E1 is enhanced by the local action of HSD17B1 in vivo, and thus, the enzyme is a potential target for pharmacological inhibition of estrogen action.
French Tragedy and the Civil Wars
Authors: Frisch Andrea
Published: August 2006

Andrea Frisch, author of The Invention of the Eyewitness: Witnessing and Testimony in Early Modern France (2004), is assistant professor of French at the University of Maryland. She is writing a book on the impact of post-civil war discourses of amnesty and forgetting on the literature and culture of seventeenth-century France.
Immigrant Rage: Alienhood, “Hygienic” Identities, and the Second World
Authors: Marciniak Katarzyna
Published: August 2006

katarzyna marciniak is Associate Professor in the English Department at Ohio University, where she teaches feminist theory and transnational literature and cinema. Currently she holds the position of Affiliated Scholar at the Center for Feminist Research at the University of Southern California. She is the author of Alienhood: Citizenship, Exile, and the Logic of Difference (University of Minnesota Press, 2006), and her interdisciplinary work on transcultural cinema and literature, exile, immigration, discourses of transnationalism, and visual culture have appeared in Camera Obscura, Cinema Journal, and, most recently, in the afi Film Reader, East European Cinemas (Routledge, 2005). A new essay, “New Europe: Eyes Wide Shut,” is forthcoming in Social Identities. Her work in progress includes a book titled “Immigrant Rage,” and a coedited collection of essays, “Transnational Feminist Encounters in Film and Media.”
The Linguistic Turn Revisited: On Time and Language
Authors: Rudolph Katherine
Published: August 2006

katherine rudolph is Associate Professor of Philosophy at Rhode Island College and a Research Affiliate at the Pembroke Center of Brown University. She has completed a book-length manuscript, This Body of My Dreams: Descartes and Augustine on the Body of Language: Linguistic Constructivism in Historical Perspective. She has published articles on Augustine and Descartes, as well as on topics in twentieth-century Continental philosophy. She has also written on issues in contemporary art.
Japanese-Korean Exchange within the Proletarian Visual Arts Movement
Authors: Kida Emiko
Published: August 2006

Translated by Brian Bergstrom
The Wnt/β-catenin pathway regulates Gli-mediatedMyf5expression during somitogenesis
Authors: Borello Ugo , Berarducci Barbara , Murphy Paula , Bajard Lola , Buffa Viviana , Piccolo Stefano , Buckingham Margaret , Cossu Giulio
Published: August 2006

Canonical Wnt/β-catenin signaling regulates the activation of the myogenic determination gene Myf5 at the onset of myogenesis, but the underlying molecular mechanism is unknown. Here, we report that the Wnt signal is transduced in muscle progenitor cells by at least two Frizzled (Fz)receptors (Fz1 and/or Fz6), through the canonical β-catenin pathway, in the epaxial domain of newly formed somites. We show that Myf5activation is dramatically reduced by blocking the Wnt/β-catenin pathway in somite progenitor cells, whereas expression of activated β-catenin is sufficient to activate Myf5 in somites but not in the presomitic mesoderm. In addition, we identified Tcf/Lef sequences immediately 5′ to the Myf5 early epaxial enhancer. These sites determine the correct spatiotemporal expression of Myf5 in the epaxial domain of the somite, mediating the synergistic action of the Wnt/β-catenin and the Shh/Gli pathways. Taken together, these results demonstrate that Myf5is a direct target of Wnt/β-catenin, and that its full activation requires a cooperative interaction between the canonical Wnt and the Shh/Gli pathways in muscle progenitor cells.
A conserved sequence motif in 3′ untranslated regions of ribosomal protein mRNAs in nematodes
Authors: Hajarnavis Ashwin , Durbin Richard
Published: August 2006

The 3′ untranslated regions (3′ UTR) of eukaryotic genes can contain motifs involved in regulation of gene expression or localization at the post-transcriptional level. This study concerns the identification of novel, conserved elements in 3′ UTRs of many ribosomal protein mRNAs in Caenorhabditis elegans and Caenorhabditis briggsae. Analysis of the region around the polyadenylation signal in many ribosomal protein mRNAs indicates the conservation of a sequence motif UUGUU occurring both before and immediately after the polyadenylation signal. Building a statistical model of this motif and searching a database of C. elegans 3′ UTRs reveals that this motif is also present in the 3′ UTR of some genes involved in translation and ribosome maturation, among others. We suggest that this signal may be involved in translation or other message-level regulation of ribosomal genes in C. elegans.
Experimental Evaluation of Ca-K Exchange Selectivity Reactions in Estuarine Sediments
Authors: Ferrell R. E. , Murthy A. S. P.
Published: August 2006

Clay materials separated from estuarine sediments in Louisiana exhibit a selectivity for exchangeable calcium in laboratory experiments. The studies were conducted at 25°C and 60°C in mixed calcium and potassium chloride solutions in which the equivalent fraction of potassium varied from 0.12 to 0.54. Calcium selectivity was observed to increase with an increase in the equivalent fraction of potassium in the external solution and the temperature. The results suggest the possible importance of ion exchange reactions in the regulation of calcium availability during early diagenetic reactions in sediments.
Low Frequency Conductivity Dispersion in Clay-Water-Electrolyte Systems
Authors: Mehran Mohsen , Arulanandan Kandiah
Published: August 2006

The electrical conductivity of a colloid-water-electrolyte system increases with the frequency of the applied alternating electric current. The phenomenon is referred to as conductivity dispersion. This paper reports on the effects of electrolyte type, electrolyte concentration, and water content on the dispersion characteristics of kaolinite, illite, and silty clay soils, with emphasis on the mechanisms governing the dispersion phenomenon. It was observed that magnitude of conductivity dispersion increases with a reduction in water content, electrolyte concentration, and cation-exchange capacity of the clay. The type of ions influence the electrical dispersion through their size and mobility. Frequency effect increases as the hydrated radius of the counterions associated with the clay surface increases. Conductivity dispersion is explained primarily in terms of counterion/co-ion ratio in the diffuse double layer. Increase in the ratio of counterions to co-ions is an indication of a larger contribution to conduction by counterions than by co-ions, which in turn results in a larger frequency effect. Although diffusion coupling has an important role in the electrical dispersion characteristics of clay—water—electrolyte systems, other coupling phenomena, particularly electro-osmotic coupling, plays a significant part.
Microporosity in Montmorillonite from Nitrogen and Carbon Dioxide Sorption
Authors: Aylmore L. A. G.
Published: August 2006

Nitrogen adsorption at 78°K and carbon dioxide sorption at 195°K on homoionic lithium, sodium, caesium, calcium, lanthanum and hexane diammonium saturated montmorillonites have been examined by means of V-n plots. In the case of carbon dioxide, sorption on the lithium saturated clay was used as a standard for comparison of the other samples.

The nitrogen plots indicate that most of the surface area lies in super-micropores of approximately 10 Å equivalent plate separation. Variations between cations are attributed to differences in the structure of the porous matrix formed on drying rather than differences in the degree of entry into quasi-crystalline regions. While the initial sorption of carbon dioxide clearly is influenced by the solvation properties of the cations, the subsequent reversibility of the isotherms and linearity of the V-n plots indicates that for all but the largest cations the same sorption process is occurring on surfaces external to the quasi-crystalline regions
Surface Charge Density Determination of Micaceous Minerals by 235U Fission Particle Track Method
Authors: Lee S. Y. , Jackson M. L.
Published: August 2006

The surface charge density of mica (001) cleavages was determined by counting the number of fission particle tracks in a given area of a 6-mm muscovite disc replica with optical and scanning electron microscopy after saturation of the layer charge by washing with 0.5 M UO2(NO3)2 solution, dilution of the excess salt by washing with 0.01 M UO2(NO3)2 in 0.005 M HNO3 (pH 2.4), blotting off the excess liquid, thermal neutron activation in contact with the muscovite disc, etching the muscovite, and counting the 235U fission tracks/cm2. In initial studies, the uranyl cations were found to hydrolyze from the cleavage surface continuously during the washings with water, ethanol or acetone to remove excess salts, but the uranyl cations in the interlayers near broken edges and crystallographical steps were strongly retained even against washings with 0.5 M CaCl2 solution. The hydrolysis of UO22 + from the smooth portions of the flake surfaces was avoided by the use of three 1-hr final washings with the 0.01 M UO2(NO3)2 in 0.005 M HNO3 solution. Each flake was pressed between filter papers three times to remove the excess solution. A negligible amount of excess salt remained on the cover glass controls. The UO22 + cations retained (mean, 3.6 ± 0.2 × 10−7 mequiv./cm2) on the cleavage surfaces of various micas were nearly equivalent to the theoretical surface charge (cation exchange capacity, 3.5 × 10−7 mequiv./cm2), showing that hydrolysis was prevented. The uranium on the unblemished mica planar surfaces increased with increasing uranyl concentrations in the final washing solution, indicating that the excess salt remaining on the surfaces had become significant. With a given UO22 + salt concentration, the uranium on the surface increased on increasing the solution pH from 2.5 to 3.5, attributable to the formation of polymeric ions such as U2O52 + and U3O82 + with higher uranium retention per unit positive charge equivalent to the fixed negative charge of the mineral surface. Uranyl cations replaced much of the interlayer cations from vermiculites even after K, Rb and Cs presaturation and drying from 110°C were employed. Strong adsorption of uranyl cations (in a form not replaced by washings with a neutral salt solution), which occurred in the defects of micaceous minerals, is important in the interpretation of actinide element retention in soils and sediments wherein these minerals are abundant.
Classification of Kaolins Exemplified by Their Textures in Scan Electron Micrographs
Authors: Keller W. D.
Published: August 2006

Varieties of kaolin, a rock, may be classified geologically, mineralogically, crystallographically, genetically, texturally, morphologically, by industrial use, and in other ways which are desired. In this paper, the first-order of classification used is geological, i.e., transported and residual, after which other categories are used as subdivisions.

Scan electron micrographs, SEM, of the textures of kaolin show that distinctive textures characterize the several categories of classification. Varieties in texture of kaolin include similarities to those typical of sedimentary, igneous and metamorphic rocks. Because word descriptions of the textures are inadequate in comparison to pictures of them, the reader is referred to the micrographs.

SEM's illustrate differences between kaolins which were transported, formed, or deposited from solution, a colloidal phase, or as orthodox clastic particles. The parent source of kaolin deposited, or “grown,” from solution may be difficult to ascertain. It is suggested that the total role of solution work in kaolin petrology can be more important than has ordinarily been credited.
Semiquantitative Chemical Analysis of Asbestos Fibers and Clay Minerals with an Analytical Electron Microscope
Authors: Hayashi Hisato , Aita Saburo , Suzuki Mikio
Published: August 2006

By using a transmission electron microscope equipped with an energy dispersive spectrometer, it was possible to detect the morphological, structural, and chemical characteristics of individual asbestos fibers and clay minerals without any realignment of the equipment. A rapid and convenient procedure for semiquantitative analysis is proposed. Analyses are given for 21 hydrous silicates, asbestos and clay minerals, by both ordinary chemical and energy dispersive methods. The energy dispersive results were comparable to those obtained by chemical analysis. Application of this procedure to asbestos fibers proved this method to be practical and valid for characterization of asbestos in environmental and tissue samples.
Electron Spin Resonance Studies of Iron Oxides Associated with the Surface of Kaolins
Authors: Angel B. R. , Vincent W. E. J.
Published: August 2006

The different types of iron oxide phases associated with the surfaces of two suites of kaolins from Georgia, U.S.A., and from the Southwest Peninsula of England, have been identified using electron spin resonance (ESR) spectroscopy combined with magnetic-filtration, thermal, and chemical treatments. It has been shown that the English kaolins are coated with a lepidocrocitelike phase, which is readily removed by de Endredy's method of deferrification, while the Georgia kaolins are coated with a hematite- or goethitelike phase, which is not removed by this treatment. Throughout the course of this study, the effects of the various physical and chemical treatments on the brightness values of the kaolins were examined.
Relation Between Swelling, Surface Area and b Dimension of Na-Montmorillonites
Authors: Odom John W. , Low Philip F.
Published: August 2006

From swelling and surface area measurements, it was found that the swelling of a montmorillonite depends linearly on the fraction of its layers that fully expand in water and that this fraction, in turn, depends linearly on the b dimension of the unit cell. Therefore, swelling is a linear function of the b dimension. However, the specific surface area of a montmorillonite is a linear function of its b dimension only if no partially expanded layers exist. It was also found that the distance between fully expanded layers at a given applied pressure is the same for all montmorillonites.
Potassium- and Ammonium-Treated Montmorillonites. I. Interstratified Structures with Ethylene Glycol and Water
Authors: Číčel Blahoslav , Machajdík Daniel
Published: August 2006

Monoionic K- and NH4-smectites saturated with ethylene glycol form mixed-layer structures which usually consist of three kinds of layers: a 10-Å, non-expanded layer; a 14-Å, partly expanded layer; and a 16.8-Å, completely expanded layer. In some samples, the 14-Å layers formed 60–70% of all layers present. When saturated with water vapor the smectites commonly consisted of three kinds of layers (10-, 12.6-, and 15.5-Å). Generally these samples contained fewer expanded layers than those saturated with ethylene glycol. This result is attributed to the smaller dipole moment of water compared with that of ethylene glycol. The greater solvation energy of NH4+ in comparison with that of K+ causes the expansion of a part of layers which did not expand in the K forms. This result indicates that there is an inhomogeneous distribution of layer charge in the smectite structure. The prevalent type of mixed layering in the studied samples is that of random distribution of layers.
Effect of SiO2/Al2O3 Ratio on the Thermal Reactions of Allophane. II. Infrared and X-Ray Powder Diffraction Data
Authors: Henmi Teruo , Tange Kazuhiko , Minagawa Tetsuo , Yoshinaga Naganori
Published: August 2006

Allophanes with SiO2/Al2O3 molar ratios from 1.38 to 1.92 were heated at temperatures up to 500°C, and the changes induced were investigated by means of infrared spectroscopy (IR) and X-ray powder diffraction (XRD). Heat treatment caused the IR absorption band near 1000 cm−1 due to Si-O stretching to shift towards higher frequencies, and the band near 450 cm−1 due to O-Si-O bending to increase markedly in intensity. These results are probably due to condensation of SiO tetrahedra, following breakdown of Si-O-Al linkages and dehydroxylation of SiOH groups. Concurrent intensity increase of the IR absorption at about 700 cm−1 suggested an increase in the amount of 4-coordinated Al in the heated materials. ‘Imogolite structures’ were decomposed progressively at higher temperatures and were almost absent at about 400°C, as indicated by the weakening and disappearance of the IR band at 348 cm−1 and of the XRD reflections at 2.25 and 1.40 Å. The XRD reflection at 3.3–3.45 Å shifted to about 3.6 Å, probably as a result of thermal condensation of the silica component. The observed thermal changes were much greater for samples with low SiO2Al2O3 ratios (1.38–1.51) than for those with high ratios (1.81–1.92), indicating a lower thermal stability for the former materials. Thus, the thermal stability of allophanes appears to be related to the content of ‘imogolite structures’ and to the polymerization status of the silica component.
Interaction of Chlordimeform with Clay Minerals
Authors: Hermosin Maria C. , Perez Rodriguez J. L.
Published: August 2006

The adsorption-desorption of the cationic pesticide chlordimeform from aqueous solutions on montmorillonite, kaolinite, illite, and vermiculite appears to be a cation-exchange process coupled with the coadsorption of neutral molecules and the extraction of Al from the structure of the mineral. Chlordimeform adsorption on montmorillonite, illite, and vermiculite by cation exchange is an irreversible process, whereas chlordimeform adsorbed on kaolinite is weakly bonded to the clay and easily removed by washing with water. X-ray powder diffraction and infrared spectroscopic data show that chlordimeform cations are adsorbed in the interlamellar spaces of montmorillonite at charge sites, lying in a flat position in contrast to kaolinite, illite, and vermiculite, where they adsorb on external surfaces or charge sites close to the crystal edges.
Interactions of Some Large Organic Cations with Bentonite in Dilute Aqueous Systems
Authors: Narine Deoraj R. , Guy Robert D.
Published: August 2006

Adsorption studies indicate that paraquat, diquat, and thionine are bound on bentonite by amounts greater than the measured cation-exchange capacity (CEC) of the clay. Methylene blue, new methylene blue, and malachite green are bound by amounts equal to the CEC. The unipositive organocations form aggregates on the clay surface. Aggregation increases with ionic strength and increases the apparent adsorption capacity by 25%. The aggregates are removed by washing with distilled water. Desorption studies show that the dyes are irreversibly bound, whereas the dipositive organocations are reversibly bound. Ionic strength variation reduces adsorption by 15 and 36% in the monovalent and divalent organocation-clay systems, respectively. In the clay-divalent organocation systems adsorption is greater on Na-saturated clay than on K-saturated clay. Adsorption is unchanged over the pH range 4.5–8.5 and decreases steadily below pH 4.0. Changes in adsorption due to changes in temperature are small. The study indicates that ionic strength is the most important variable in clay-organocation interactions.
Chromium-Bearing Dickite and Chromium-Bearing Kaolinite from Teslić, Yugoslavia
Authors: Maksimović Zoran , White Joe L. , Logar Mihovil
Published: August 2006

Three samples of bluish chromium-bearing dickite and chromium-bearing kaolinite were examined by X-ray powder diffraction, chemical analysis, electron microprobe, optical, and infrared techniques to determine whether chromium is part of the mineral structure or present in an impurity phase. Two of the samples studied contain a single dominant chromium-bearing phase (either dickite or kaolinite); the third contains equal proportions of both minerals. The optical absorption and infrared spectra are consistent with the presence of octahedrally coordinated chromium. The range of Cr3+-Al3+ substitution is rather limited: up to 0.06 atoms per unit cell. The electron microprobe study revealed the presence of very rare, minute grains of chromite, as well as a uniform distribution of chromium in dickite and kaolinite, indicating that chromium occupies octahedral sites in the structure of these minerals.
Zeolite Reactions in the Tuffaceous Sediments at Teels Marsh, Nevada
Authors: Taylor Marsha W. , Surdam Ronald C.
Published: August 2006

The most prominent authigenic reaction in Holocene tuffaceous sediments at Teels Marsh, Nevada, is the hydration of rhyolitic glass by interstitial brines and the subsequent formation of phillipsite. This reaction has the form: rhyolitic glass + H2O → hydrous alkali alumninosilicate gel → phillipsite. Phillipsite is the most abundant authigenic phase in the tuffaceous sediments (>95%), analcime is the next most abundant phase, and clinoptilolite occurs as a trace mineral in the <2-mm fraction. Analcime forms by the reaction of phillipsite and Na+. Gaylussite and searlesite also are common authigenic phases at Teels Marsh. The concentration of silica in the interstitial brines is controlled by one or more of the authigenic reactions at less than 100 ppm. A stoichiometric equation for the reaction of phillipsite to analcime at Teels Marsh is:
$$0.43N{a + }\, + {K_{0.43}}N{a_{0.57}}AlS{i_{3.1}}{O_{8.2}}\, \cdot \,3.2{H_2}O\, \to \,NaAlS{i_2}{O_6}\, \cdot \,{H_2}O\, + \,1.1{H_4}Si{O_4}\, + \,0.43{K + }.$$

Sodium and potassium activities of brines associated with both phillipsite and analcime were used to estimate the equilibrium constant for this reaction as 3.04 × 10−5. The ΔG0 value for the reaction is +6.2 kcal/mole at 25°C and 1 atm pressure. The estimated ΔG0 value of phillipsite, using this reaction, is −1072.8 kcal/mole at 25°C and 1 atm.
Surface Characteristics of Kaolinitic Clays and Clay-Humic Acid Complexes by Potentiometric and Conductometric Titrations
Authors: Lockhart N. C.
Published: August 2006

Acid and non-acid forms of kaolinite clays were found by potentiometric and conductometric titrations to possess a weak acid species, the concentration of which was increased by acidic preparation conditions and by the presence of soil organic matter bound to the clay. A stronger acid species was also found in untreated and in organic-free, HCl-treated samples (washed free of excess acid). The end points for organic-free and/or ion-exchanged samples were used to predict the end points for untreated samples. A surface-chemical model involving MOH2+, MOH, and MO− species (where M = Al and/or Fe) was fitted to the titration data and to the cation-exchange capacities. MOH2+ is the stronger acid and MOH the weaker acid; exchange of Na+ counterions by H+ converts MO−Na+ sites to MOH sites. Humic acid was probably complexed or chelated to some hydroxylated Al/Fe sites through COOH and phenolic OH groups. The COOH groups contributed supplementary stronger acid species which were not exchangeable, whereas the OH groups contributed supplementary weaker acid species and also increased the CEC relative to that for organic-free samples.
Formation of Iddingsite Rims on Olivine: A Transmission Electron Microscope Study
Authors: Eggleton Richard A.
Published: August 2006

Iddingsite rimming olivine in a basanite from the Limberg, Germany, is composed of saponite and goethite. Transmission electron microscopy of ion-thinned, oriented crystals suggests a two-stage alteration process. At first, the olivine breaks into a mosaic of 50-Å diameter {110} bounded needle-shaped domains which change to a metastable hexagonal phase having a = 3.1 Å and c = 4.6 Å, probably of close-packed, metal-oxygen octahedra. This reaction opens solution channels in the olivine which are detectable from about 20-Å diameter and are parallel to the olivine y-axis. Laths of smectite, one or two layers thick, 20 Å wide, and as much as 100 Å long parallel to their y-axis nucleate from the metastable phase and begin to fill in the solution channels. The laths orient with smectite (001) parallel to olivine (100). As the channels widen, prismatic {110} goethite crystals form directly from the metastable hexagonal phase. This first stage thus provides heterogeneous nuclei of smectite and goethite, formed epitactically and perhaps topotactically from a metastable intermediary.

In a second stage,these nuclei enlarge by deposition from solution as water migrates readily through the solution channels. A reduction in total volume allows smectite veins to form, misoriented with respect to the olivine. The reaction conserves iron, requires the addition of aluminum and water, and releases magnesium and silicon. Electron microprobe analyses of the iddingsite indicate that the smectite is saponite.
Influence of Chloride on the Formation of Iron Oxides From Fe(II) Chloride. II. Effect of [Cl] on the Formation of Lepidocrocite and its Crystallinity
Authors: Taylor R. M.
Published: August 2006

Diffractograms of lepidocrocites formed from the oxidation of Fe(II) chloride solutions at pH 7 and 25°C showed differential line broadening with (0k0) reflections being much sharper than (hk0) or (hkl). As the initial [Cl]/[Fe] ratio was increased from 2, crystallinity increased in all axial directions, as defined by the width at half height of diffraction peaks. At [Cl]/[Fe] ratios greater than ~8, the crystallinity did not increase further, and for reflections involving the a-axis direction, it appeared to decrease. Increased [Cl]/[Fe] ratios changed the rate of the oxidation/hydrolysis reactions. These variations reflect changes in the stability and/or composition of the intermediate green rust phase, (Fe(II)Fe(III) hydroxychloride) in the high [Cl] environment. The influence of the [Cl]/[Fe] ratio was related to the experimental conditions employed, especially where they influenced the rate of oxidation.
Weathering of Ilmenite in a Lateritic Pallid Zone
Authors: Anand R. R. , Gilkes R. J.
Published: August 2006

In a lateritic pallid zone ilmenite crystals alter via pseudorutile to porous leucoxene grains composed of randomly oriented aggregates of ~0.06 μm anatase crystals. This style of alteration differs from that in beach sands where parallel oriented rutile crystals develop from pseudorutile. Increased Si and Al in the altered grains is due to the crystallization from soil solution of halloysite, kaolinite and gibbsite within pores rather than to the incorporation of these elements into anatase crystals. Manganese was a significant constituent (3.2% Mn2O3) of the original ilmenite but was not retained by the leucoxene grains. The minor constituents Ni, Zn, Cu, Mg, Co and Ca were also lost, but Cr and V were retained.
Synthesis and Characterization of Zeolites in the System Na2O-K2O-Al2O3-SiO2-H2O
Authors: Donahoe Rona J. , Liou J. G. , Guldman Sandra
Published: August 2006

Zeolites having the structures of phillipsite, merlinoite, and gobbinsite were synthesized from clear solutions at 80°C in the system Na2O-K2O-Al2O3-SiO2-H2O and their morphologies, cell parameters, and compositions determined. At 3.5 M silica concentration, the formation of merlinoite (synthetic zeolite W) is favored over the formation of phillipsite (synthetic zeolite ZK-19) by solution conditions of high pH (> 13.6) and low Na/(Na + K) ratios (<0.5).

Using the information obtained from the synthesis experiments, the presence of merlinoite was predicted in sediments from Searles Lake, a saline, alkaline lake in California with ideal physiochemical conditions for its formation. Merlinoite was subsequently discovered to occur in tuffaceous sediments as part of an authigenic silicate zonation pattern from phillipsite → phillipsite + merlinoite → merlinoite → K-feldspar with increasing depth. Because of the close similarities in the physical properties of phillipsite and merlinoite, merlinoite may be much more common as an authigenic mineral than is currently realized.
Effects of Exchangeable Cation Composition on the Thermal Expansion/Contraction of Clinoptilolite
Authors: Bish David L.
Published: August 2006

To understand and predict the effects of a thermal pulse induced by a radioactive waste repository on clinoptilolite-bearing rocks, the lattice parameters of 6 natural and 3 cation-exchanged (Ca, K, Na) clinoptilolites were studied as a function of temperature. The samples were examined at room temperature, under vacuum, and at 50°C increments to 300°C using a high-temperature X-ray powder diffractometer. The unit cell of all samples decreased in volume between 20° and 300°C Na-saturated clinoptilolite underwent the greatest volume decrease (8.4%) and K-saturated clinoptilolite the smallest (1.6%), of the clinoptilolites studied. The volume decrease for the Ca-saturated clinoptilolite was 3.6%. The highest percentage decrease for each sample was along the b axis, generally 80–90% of the total volume decrease. The change in the a axis was the smallest and was usually <5%, although 26.5% of the contraction of the Na-exchanged clinoptilolite was along a. The bulk of the volume contraction of many samples occurred on evacuation at room temperature, demonstrating that the observed changes were due to water loss and not to temperature-induced structural changes. Low-angle scattering was significantly reduced upon evacuation for every sample, and the 110 reflection of clinoptilolite at 7.45°2θ became obvious, whereas it was not in the untreated samples.

These data show that the effects of heating on the unit-cell volume of clinoptilolite depend strongly on the exchangeable cation content. Significant reductions in the unit-cell volumes of natural, mixed Na-K-Ca clinoptilolites could take place in rocks in a repository environment, particularly if the clinoptilolites occurred in unsaturated, dehydrated rock. The unit-cell volumes of clinoptilolites in partially saturated rocks at temperatures below 100°C, however, should not decrease significantly.
Natroalunite in a Laterite Profile Over Deccan Trap Basalts at Matanumad, Kutch, India
Authors: Chitale D. V. , Güven N.
Published: August 2006

An end-member natroalunite of composition (K0.04Na0.96)(Al2.98Fe0.02)(SO4)2(OH)6 occurs in saprolitic clays in a laterite profile developed over Deccan Trap basalts at Matanumad in the Kutch region of Gujarath state, India. Pseudocubic natroalunite crystals, ranging from 0.5 to 1 µm in size, have replaced pseudohexagonal, 2-µm-size platelets of kaolinite. The reverse reaction (kaolinization of natroalunite) has also been observed in the laterites and bauxites immediately adjacent to the saprolite. The kaolinite crystallites that replaced natroalunite occur as a mosaic of anhedral platelets that range in size from 0.1 to 0.3 µm. The formation of natroalunite at Matanumad postdates the laterization of the basalts. It is related to the post-diagenetic formation of sulfuric acid-rich solutions by the oxidation of pyrite in the Eocene-Oligocene black shales of the Matanumad basin. The kaolinitic clays at the top of the saprolite zone have been intensely altered by the acidic solutions, leading to a high concentration of natroalunite.
Structural Study of a Benzidine-Vermiculite Intercalate Having a High Tetrahedral-Iron Content by 57Fe Mössbauer Spectroscopy
Authors: Cardile C. M. , Slade P. G.
Published: August 2006

57Fe Mössbauer spectra obtained at room temperature and 78 K for natural Mg-saturated, Ca-saturated, and benzidinium-intercalated vermiculite having a high tetrahedral iron content are presented. For all samples the spectra were computer-fitted with five overlapping doublets, representing Fe in both tetrahedral and octahedral sites. One doublet has parameters consistent with the weathered ilmenite known to be present as inclusions. For the intercalated vermiculite, the δ value of the doublet assigned to the tetrahedral Fe3+ increased with respect to the untreated sample, suggesting that the electron densities about the Fe sites had decreased following intercalation. A charge movement from the silicate layers towards the interlayer monovalent benzidinium ions is also implied. The direction of this charge movement is opposite to that found when blue monopositive radical cations form on montmorillonite surfaces. The Mössbauer evidence suggests the absence of an interlayer-Fe3+ complex.
Petrology of the Desmoinesian Excello Black Shale of the Midcontinent Region of the United States
Authors: Ece Omer Isik
Published: August 2006

The Excello Shale is one of the best exposed and most laterally continuous of the Pennsylvanian cyclothemic black shales in the midcontinent region of the United States. Its petrology and paleoenvi-ronmental significance were studied to understand the nature of cyclic black shales in general and how they relate to the habitat of hydrocarbon source beds. The Excello is thinly laminated, fissile where weathered, and rich in organic matter and phosphate nodules; it is 90–120 cm thick. Its thin laminations, fine particle size, and high total organic carbon (TOC) content suggest that it was deposited in a quiet water environment of an epeiric sea having anaerobic bottom water. The Excello Shale consists of two lithofacies: non-bioturbated black shale and bioturbated yellow-brown shale. Petrographic studies show that the black shale contains wavy to straight laminations and that the yellow-brown shale contains discontinuous and random laminae and mottled stratification. The close association of organic matter and phosphate-controlled nodule morphology (spherical, elongated, bladed, and platy) appear to be related to progressive decreases in nutrient supply of the sea water from the ancient ocean (Panthalassa).

Clay-mineral assemblages consist mainly of detrital illite, kaolinite, chlorite, and illite/smectite (I/S). Grain size and amount of these clays increase and TOC decreases shoreward towards the probable source areas of the clay minerals in the northern Ouachita region and northern Iowa. Quartz, carbonate-fluor-apatite, carbonate fossil fragments, and minor feldspar and pyrite are the principal minerals in the Excello Shale. Minor amounts of fine-silt-size carbonate minerals are present in some samples. Limestone concretions, 90–150 cm in diameter and 30 cm thick, were found at only one locality in Missouri where the Excello is a maximum of about 3 m thick. Fissility increases with weathering along the bedding plane, and laminae are separated by a limonite film. Four petrographically distinct microfabric variations of the Excello Shale appear to be related to the TOC content and bioturbation. Textural and structural properties of the shale are more developed with increasing organic matter content.
Parameters Influencing Layer Stacking Types in Saponite and Vermiculite: A Review
Authors: Suquet Hélène , Pezerat Henri
Published: August 2006

Saponites and vermiculites may assume at least 11 ordered or semi-ordered layer stacking sequences. For a given relative humidity, the layer stacking type assumed is a function of the nature of the interlayer cation, the layer charge density, the mean size of the particles, and the di- or trioctahedral character of the sheets. For each interlayer cation, a succession of layer stacking types can be observed as relative humidity increases. For high relative humidity, some particular layer stacking types exist, but only for low-charge minerals. No other differences have been found for saponites and vermiculites in each successive layer stacking type. The degree of order that these layer stacking types imply is probably due to the existence of electrostatic bonds between hydrated interlayer cations and surface oxygens of the substituted tetrahedra. For octahedrally substituted 2:1 phyllosilicates, however, the disorder of the layer stacking sequences is related to a highly delocalized distribution of negative charges on the surface oxygens of the layers.

A study of the superstructures detected in saponites and vermiculites indicates that the interlayer cations tend to be located as far as possible from one another. The superstructures exist only with some cations and some layer stacking types and if the layer charge density is compatible with the charge produced by the cation distribution in this kind of superstructure.
Charge Reduction, Octahedral Charge, and Lithium Retention in Heated, Li-Saturated Smectites
Authors: Jaynes W. F. , Bigham J. M.
Published: August 2006

Reference smectites were examined to determine relationships between Li uptake, cation-exchange capacity (CEC), and octahedral layer charge after Li saturation and heating at 250°C (Hofmann-Klemen effect). Direct measurements of exchangeable Li after heating led to overestimates of charge reduction due to entrapment of Li in collapsed interlayers. Expansion of interlayers by sequential washings with 1 N MgCl2, 0.01 N MgCl2, and ethanol and subsequent determinations of exchangeable Mg provided accurate measurements of reduced charge. The CEC reductions observed in dioctahedral samples as a result of Li saturation and heating equaled octahedral charge values derived from published mineral formulae, and interlayer charge estimates obtained by alkylammonium exchange confirmed that measured CEC reductions were a consequence of uniform decreases in octahedral layer charge.

Dioctahedral specimens retained 1 to 10 meq/100 g of non-exchangeable Li in excess of CEC reduction and were acidified in direct proportion to their total Fe contents, apparently as a result of the deprotonation of structural hydroxyl groups. Mild acid treatment reprotonated these hydroxyl groups, released excess Li, and resulted in total Li contents comparable to measured CEC reductions. Heating (250°C) Mg-saturated hectorite induced a loss of octahedral Li, acidification, and a reduction of CEC, indicating that Mg had partially replaced octahedral Li. These results suggest that octahedral Li is mobile at low temperatures and that cation movement into or out of the octahedral sheet is favored if the layer charge is reduced.
Quantitative Determination of Clinoptilolite in Soils by a Cation-Exchange Capacity Method
Authors: Ming Douglas W. , Dixon Joe B.
Published: August 2006

A cation-exchange capacity (CEC) method based on ion-sieving properties was developed for the quantitative determination of clinoptilolite in soils. In this method, both zeolitic and non-zeolitic exchange sites in the soil sample are saturated with Na+. The CEC of the non-zeolitic exchange sites is determined by replacing the Na− in these sites with tert-butylammonium ions. The tert-butylammonium ion cannot be exchanged into the zeolitic exchange sites because it is too large to pass through the channels in the clinoptilolite structure. The sample is next washed with NH4OAc to replace the Na+ in the zeolitic exchange sites. The amount of soil zeolite is then estimated by comparing the CEC of zeolitic exchange sites to the total zeolite CEC (175 meq/100 g for pure clinoptilolite). Prior to the CEC analyses, carbonates and organic matter must be removed to minimize interference with the exchange process. A high correlation (r2 = .96) was observed between the abundance of clinoptilolite estimated using the CEC method and the abundance estimated by semiquantitative X-ray powder diffraction analysis.

The CEC procedure was used to quantify clinoptilolite in an Aridic Calciustoll soil from south Texas. About 2–5% clinoptilolite occurs in the A and B horizons, and concentrations progressively increase with soil depth to as much as 20% in the CBk2 horizon.
Ferrian Saponite in a Gabbro Saprolite at Mont MéGantic, Quebec
Authors: Kodama H. , De Kimpe C. R. , Dejou J.
Published: August 2006

Gabbroic saprolite at Mont Mégantic, Quebec, was studied in detail mineralogically to gain a better understanding of the origin of ferruginous smectite reported previously from these rocks. The parent rock is a ferrogabbro composed of plagioclase, augite, calc-alkalic amphiboles, biotite, olivine, magnetite, ilmenite, and apatite. Extensive weathering has decomposed most of the mafic minerals and magnetite to goethite, lepidocrocite, and iron-rich clay minerals, which occur in numerous microcracks distributed irregularly in the outer shells of boulders and in cracks and fissures in the bedrock. Some of the felsic minerals have altered to kaolinite. The secondary minerals and the more resistant primary minerals, such as plagioclase, ilmenite, and apatite, have subsequently moved to the lower part of the saprolite. The major ferruginous clay minerals present are smectite and vermiculite, which are compositionally similar, except that the smectite is slightly richer in SiO2 and MgO and poorer in Fe2O3 than the vermiculite.

To establish a structural formula for the ferruginous smectite, the oxidation state of Fe in a sample treated with dithionite-citrate-bicarbonate was examined by Mössbauer spectroscopy. All structural iron was found to be ferric. The calculated structural formula of a Na-saturated sample is:
$$N{a_{0.61}}\left( {M{g_{1.39}} + Fe_{0.85}^{3 + }A{l_{0.17}}M{n_{0.03}}} \right)\left( {S{i_{3.49}}A{l_{0.51}}} \right){O_{10}}{\left( {OH} \right)_2},$$ which has a total octahedral population of 2.44. Octahedral (Mg + Mn) exceeds octahedral (Fe3+ + Al). The 060 reflection at 1.527 Å is closer to the 1.530-Å value typical of saponite than to the 1.518-Å value typical of nontronite. The infrared spectra of the ferruginous smectite is also similar to that of saponite. Thus, the mineral is best described as a ferrian saponite. Ferroan saponite originally formed, and due to subsequent oxidation, some Fe3+ was expelled from the octahedral sheets, giving rise to a ferrian saponite containing octahedral vacancies. The expelled iron presumably formed the iron oxyhydroxides that coexist with the saponite.
Statistical Analysis of Clay Mineral Assemblages in Fault Gouges
Authors: Klima K. , Riedmüller G. , Stattegger K.
Published: August 2006

The clay mineral distributions in fault gouges from shear zones in several slates, phyllites, mica schists, and gneisses of the Eastern Alps were statistically analyzed for consistencies in their occurrence. Discriminant analyses suggested significant groupings of the most common minerals: illite, smectite, kaolinite, and chlorite. The clay mineral distributions in the fault gouges appeared to be related to regional geological units. No relationship, however, was found with the piles of nappes of the Alps. The influence of the mineralogical composition of the parent rock on the clay mineral assemblages appeared to be minor, but the shear behavior of the parent rocks, which is mainly a function of rock strength, was found to control the formation of the clay minerals. In hard rocks (e.g., gneisses), solution transfer at an early stage of the shear process was apparently extensive enough to favor kaolinite formation. As shearing continued, the rate of solution transfer gradually decreased and favored the formation of smectite. In softer rocks (e.g., phyllites), the extent of solution transfer during the shear process was less than in the gneisses and generated an environment that favored smectite formation, even during the early stages of shearing.
Interaction of Phenamiphos with Montmorillonite
Authors: Rodríguez J. Maza , López A. Jiménez , Bruque Sebastián
Published: August 2006

Phenamiphos interacted with homoionic montmorillonites of Ca2+, Mn2+, Co2+, and Ni2+ to form interlayer complexes having basal spacings of about 16.5 Å. In the infrared spectra, the ν-PO bands were displaced towards lower frequencies suggesting that this group interacted with the exchange cations. Moreover, a small shoulder at 1600 cm−1 indicated the partial protonation of the phenamiphos. After heating the complexes to 110°, 160°, and 200°C, however, the bands corresponding to δ-NH2+ and ν-NH intensified because of increased protonation, whereas the ν-PO bands had the same intensity as in pure phenamiphos. The fundamental implication of these observations is that phenamiphos interacts with exchange cations through molecules of coordinated water, possibly by means of the P=O group.
Electron Transfer Processes Between Hydroquinone and Iron Oxides
Authors: Kung K.-H. , McBride M. B.
Published: August 2006

The kinetics of hydroquinone oxidation by aqueous suspensions of pure hematite and goethite-ferrihydrite mixtures at pH 6.0, 7.4, and 9 was studied using an on-line analysis system. The electron transfer between hydroquinone and the Fe oxides was monitored by UV-visible and electron spin resonance spectroscopy. The adsorption of organics on the Fe oxide surface was detected by Fourier-transform infrared spectroscopy. For different Fe oxides, a higher surface area was correlated with a greater oxidizing ability and greater adsorption of organics, suggesting that the oxidation reaction was a surface process. A reversal of the initially rapid redox reaction was found in this system, suggesting a delayed release of Fe2+ into solution as the reduction of the Fe oxide proceeded. Redox potential calculations confirmed the thermodynamic favorability of the reaction reversal. A distribution of the reduced state over neighboring Fe atoms on the oxide surface probably was responsible for the initial suppression of Fe2+ release into the aqueous phase. Based upon these observations and detection of the semiquinone radical as an intermediate of hydroquinone oxidation, an inner-sphere one-electron transfer mechanism for the oxidation of hydroquinone at the oxide surface is proposed.
Hypothetical Structures of Magadiite and Sodium Octosilicate and Structural Relationships Between the Layered Alkali Metal Silicates and the Mordenite- and Pentasil-Group Zeolites
Authors: Garcés Juan M. , Rocke Stephen C. , Crowder Cyrus E. , Hasha Dennis L.
Published: August 2006

Hypothetical model structures for magadiite and sodium octosilicate, based on the structure of the zeolite dachiardite, are proposed that consist of layers of 6-member rings of tetrahedra and blocks containing 5-member rings attached to both sides of the layers. The infrared (IR) and nuclear magnetic resonance spectra of magadiite and sodium octosilicate have features in common with spectra of zeolites in the ZSM-5 and mordenite groups. A peak at 1225 cm-1 in the IR spectra of magadiite and sodium octosilicate is characteristic of zeolites containing 5-member rings, such as ZSM-5- and mordenite-type zeolites. The defect structures of pentasil zeolites may therefore be akin to layered alkali metal silicates containing zeolite-like domains, in which part of the silanol groups from adjacent silicate layers are condensed (cross-linked) forming siloxane linkages.