bluuebunny/crossref_metadata_2025 huggingface dataset:
GBF1, a cis-Golgi and VTCs-localized ARF-GEF, is implicated in ER-to-Golgi protein traffic
Authors: Zhao Xinhua , Claude Alejandro , Chun Justin , Shields David J. , Presley John F. , Melançon Paul
Published: August 2006

The formation and maturation of membrane carriers that transport cargo from the ER to the Golgi complex involves the sequential action of the coat protein complexes COPII and COPI. Recruitment of COPI to nascent carriers requires activation of ADP-ribosylation factors by a BrefeldinA-sensitive guanine nucleotide exchange factor. Using new antisera and a GFP-tagged protein, we demonstrate that the exchange factor GBF1 localized to both Golgi membranes and peripheral puncta, near but separate from ER exit sites. Live cell imaging revealed that GFP-GBF1 associates dynamically with both membranes through rapid exchange with a large cytosolic pool. Treatment with BrefeldinA dramatically altered this rapid exchange, causing accumulation of GBF1 on both Golgi and peripheral puncta before eventual redistribution to the ER in a microtubule-dependent manner. Measurement of diffusion coefficients and subcellular fractionation confirmed this shift in GBF1 from cytosolic to membrane bound. BrefeldinA-induced accumulation of GBF1 coincided with loss of COPI from peripheral puncta. Furthermore, recruitment of GBF1 to cargo-containing peripheral puncta coincided with recruitment of COPI, but not COPII. Strikingly, microinjection of anti-GBF1 antibodies specifically caused dissociation of COPI from membranes. These observations strongly suggest that GBF1 regulates COPI membrane recruitment in the early secretory pathway.
Ca2+-independent phospholipase A2 enhances store-operated Ca2+ entry in dystrophic skeletal muscle fibers
Authors: Boittin François-Xavier , Petermann Olivier , Hirn Carole , Mittaud Peggy , Dorchies Olivier M. , Roulet Emmanuelle , Ruegg Urs T.
Published: August 2006

Duchenne muscular dystrophy is caused by deficiency of dystrophin and leads to progressive weakness. It has been proposed that the muscle degeneration occurring in this disease is caused by increased Ca2+ influx due to enhanced activity of cationic channels that are activated either by stretch of the plasma membrane (stretch-activated channels) or by Ca2+-store depletion (store-operated channels). Using both cytosolic Ca2+ measurements with Fura-2 and the manganese quench method, we show here that store-operated Ca2+ entry is greatly enhanced in dystrophic skeletal flexor digitorum brevis fibers isolated from mdx5cv mice, a mouse model of Duchenne muscular dystrophy. Moreover, we show for the first time that store-operated Ca2+ entry in these fibers is under the control of the Ca2+-independent phospholipase A2 and that the exaggerated Ca2+ influx can be completely attenuated by inhibitors of this enzyme. Enhanced store-operated Ca2+ entry in dystrophic fibers is likely to be due to a near twofold overexpression of Ca2+-independent phospholipase A2. The Ca2+-independent phospholipase A2 pathway therefore appears as an attractive target to reduce excessive Ca2+ influx and subsequent degeneration occurring in dystrophic fibers.
Regioselective Synthesis of Lipophilic Dithiocarbamate Derivatives of Cellulose to Prepare a Novel Solvent Extraction Reagent for Selective Extraction of PGM Ions and Cu(II)
Authors: Dhakal Rabindra Prasad , Inoue Katsutoshi , Ohto Keisuke , Baba Yoshinari
Published: August 2006

Regenerated cellulose from cellulose triacetate was regioselectively converted into its lipophilic amino and dithiocarbamate derivatives to prepare novel solvent extraction reagents with series of substitutions and deoxy substitution reaction. The 6-deoxydithiocarbamate-2,3-didecyl cellulose prepared in this work significantly demonstrated the high lipophilicity coupled with high selectivity for PGM ions and also to the Cu(II) over Ni(II) and Zn(II) in liquid–liquid extraction.
Disproportionation Reaction of Seven-coordinate [ReVO(tpen)]3+ into [ReIVO(tpen)]2+ and [ReVII(O)3(tpenH-κ3N,N″,N′″)]2+ where tpen is N,N,N′,N′-Tetrakis(2-pyridylmethyl)ethylenediamine
Authors: Tabeya Toshihiro , Abe Masaaki , Sasaki Yoichi
Published: August 2006

UV–vis and 1H NMR spectra provide unambiguous evidences for the disproportionation reactions of [ReVO(tpen)]3+ to give [ReIVO(tpen)]2+ and [ReVII(O)3(tpenH-κ3N,N″,N′″)]2+ (tpen = N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine) in 2:1 ratio with the important participation of water molecules.
Non-galvanic Hydrogen Production Using High Steam Pressure Gradients
Authors: Song Sun-Ju , Wachsman Eric D
Published: August 2006

Equilibrium defect concentrations calculated by numerical modeling based on a point defect model showed that protons and electrons were predominant defects under reducing and high pH2O conditions. Hydrogen permeation flux for 1 mm SrCe0.95Y0.05O3−d membranes was derived on the basis of chemical diffusion theory as functions of pO2 and pH2O. Hydrogen permeation flux keeps increasing with increasing water vapor pressure gradient with a reference to 10−6 atm of pH2O.
Efficient Formation of Homo and Hetero Metal Clusters by Triangular Trisaloph Ligand as a Partial Template
Authors: Nabeshima Tatsuya , Miyazaki Hayato , Iwasaki Atsushi , Akine Shigehisa , Saiki Toshiyuki , Ikeda Chusaku , Sato Soichi
Published: August 2006

Homo metal cluster containing seven Zn atoms was efficiently synthesized in high yield via a template effect of a trisaloph ligand and characterized by NMR, MS, X-ray crystallography, etc. The homo cluster can be converted quantitatively to Zn3·La hetero metal cluster.
Promoting Effect of Pd Addition to Ni0.2Mg0.8Al2O4 in Oxidative Steam Reforming of Methane
Authors: Nurunnabi Mohammad , Mukainakano Yuya , Kado Shigeru , Kunimori Kimio , Tomishige Keiichi
Published: August 2006

Addition of Pd to Ni0.2Mg0.8Al2O4 promoted oxidative steam reforming of methane, and it gave high activity under high partial pressure of steam and low W/F, where Ni0.2Mg0.8Al2O4 showed very low activity. The Ni0.2Mg0.8Al2O4 requires the H2 reduction pretreatment; however, Pd/Ni0.2Mg0.8Al2O4 can be activated automatically by the reactant gases of oxidative reforming of methane.
Paroxetine Use During Pregnancy: Is it Safe?
Authors: Thormahlen Genine M
Published: August 2006

Objective:

To evaluate the literature assessing the neonatal risks of antepartum paroxetine use.

Data Sources:

MEDLINE (1966–August 2006) and International Pharmaceutical Abstracts (1970–August 2006) searches were performed. Key search terms included paroxetine, SSRI, pregnancy, malformations, neonate, and fetus.

Data Synthesis:

Selective serotonin-reuptake inhibitors (SSRIs) are associated with neonatal withdrawal symptoms such as respiratory distress, irritability, lethargy, and tremors. In a cohort study, 30% of infants exposed to SSRIs had poor neonatal adaptation, compared with 9% of controls (p = 0.018). Some reports indicate that paroxetine is more commonly associated with neonatal withdrawal than other SSRIs. Recently, paroxetine was associated with a 1.82-fold (95% CI 1.17 to 2.82) increased risk of congenital malformations compared with other antidepressants. Other SSRIs were also associated with an increased risk of congenital malformations; however, the results were not statistically significant. Literature supporting these findings includes case reports and case–control or cohort studies. The Food and Drug Administration recommendations regarding paroxetine use during pregnancy have been added to the labeling information.

Conclusions:

Paroxetine may cause adverse outcomes in the neonate when used during pregnancy and should be discontinued in women who are pregnant or trying to become pregnant. The risks and benefits of other antidepressant use should be analyzed on an individual basis.
Alteration of Smectite in a System Including Alanine at High Pressure and Temperature
Authors: Hashizume Hideo , Yamada Hirohisa , Nakazawa Hiromoto
Published: August 2006

Transformation of montmorillonite was experimentally investigated using a model system of montmorillonite-alanine at 100 MPa and up to 500°C. Sodium-montmorillonite changed to a mixed layer mineral of sodium- and ammoniumn-montmorillonites (Na/NH4-Mnt) in the temperature range from 150 to 400°C. Ammonium ions were the decomposition product of alanine above 150°C. The Na/NH4-Mnt transformed to regularly and randomly interstratified minerals of NH4-montmorillonite and NH4-mica (o. NH4-Mnt/NH4-Mic and d. NH4-Mnt/NH4-Mic) at 400°C. These mixed layered minerals transformed to ammonium-mica at 500°C. Ammonium-analcime appeared and coexisted with the smectites at temperatures over 200°C, and with albite for those over 400°C.

In comparison with the results of previous experiments in which there was no organic component, the present results revealed that (1) some uncommon mineral phases appeared by replacement of sodium ions in montmorillonite with ammonium ions, i.e., NH4-Mic, o. and d. NH4-Mnts, o. and d. NH4-Mnt/NH4-Mics, and (2) ammonium-analcime appeared. The mineral assemblages and alteration sequences correspond better with those observed in the natural system than those known from experimental results in aluminosilicate-water system.
Morphology of Zeolites in Sedimentary Rocks by Scanning Electron Microscopy
Authors: Mumpton Frederick A. , Ormsby W. Clayton
Published: August 2006

In the nearly 2000 occurrences of zeolites in sedimentary rocks of volcanic origin about 15 zeolite minerals have been identified. The mode of occurrence of six of these, clinoptilolite, erionite, chabazite, phillipsite, analcime, and mordenite, is described, and their morphology is illustrated with scanning electron micrographs.
Organomineral Derivatives Obtained by Reacting Organochlorosilanes with the Surface of Silicates in Organic Solvents
Authors: Ruiz-Hitzky E. , Fripiat J. J.
Published: August 2006

Stable organomineral derivatives are formed by reaction of organochlorosilanes with certain phyllosilicates. Organosiloxyl functions are grafted on silanol groups present at external mineral surfaces.

Water molecules adsorbed on external mineral surfaces may cause hydrolysis of the reactant organosilicon products, with liberation of HCl. This, in turn, may react with the silicate: octahedral cations are extracted from the lattice and fresh Si-OH groups, capable of further grafting, are formed on the mineral surface.

On the other hand, when difunctional reagents such as methylvinyldichlorosilane are used and if the ratio of adsorbed water to added reactive is adequate, then polymeric species with polysiloxane chains are grafted on the mineral.

Because of its high content of silanol groups, sepiolite forms organomineral compounds having a relatively high organic matter content. With chrysotile, the amount of organic matter grafted to the silicate, is considerably smaller, but it increases appreciably if water is added to the reacting products. This is attributed to hydrolysis of the organic reactant and subsequent destruction of external “brucitic” layers by acid attack.
Chrome Chlorite (Kotschubeite) from the Nuggihalli Schist Belt
Authors: Damodaran K. T. , Somasekar B.
Published: August 2006

Chrome chlorite associated with the chromite deposits of the Nuggihalli schist belt has been investigated by detailed mineralogical, chemical, X-ray diffraction, differential thermal and i.r. spectral analyses. Following the nomenclature of Lapham (1958) it is inferred that the chromium of the chrome chlorite is in the tetrahedral position and therefore the mineral is kotschubeite and not kaemmererite as suggested by earlier workers.
Structural Analysis of Sepiolite by Selected Area Electron Diffraction—Relations with Physico-Chemical Properties
Authors: Rautureau M. , Tchoubar C.
Published: August 2006

The electron structural analysis of a Madagascar sepiolite (Ampandrandava) was carried out by selected area electron diffraction obtained from monocristals. Fourier projections, derived from the experimental intensity of Okl, hOl and hkO reflections, show that the Mg2+ cations on the edges of the sheets are distributed between two sites. Correlatively the water molecules bound to these Mg2+ occupy two distinct positions. These principal structural differences with the Brauner and Preisinger model explain details of the i.r. spectra during the desorption of water or the adsorption of polar molecules. The differences between the two models can be considered as a consequence of treating the mineral in vacuum.
A Mössbauer and I.R. Spectroscopic Study of the Structure of Nontronite
Authors: Goodman B. A. , Russell J. D. , Fraser A. R. , Woodhams F. W. D.
Published: August 2006

Mössbauer and i.r. spectra of a series of nontronites show that Fe3+ and Al3+ are distributed between tetrahedral and octahedral sites. The Mössbauer results have reaffirmed the occupation by Fe3+ of octahedral sites at which these ions are coordinated to pairs of OH groups in both cis and trans configurations. The distribution of Fe3+ between these two sites varies considerably but in all of the nontronites some Fe3+ occurs in the trans site in contrast to the all cis occupancy of the centro-symmetric structure proposed by Mering and Oberlin (1967). In one of the nontronites the distribution of Fe3+ between these two sites approaches that in the ideal non-centrosymmetric structure proposed for montmorillonite.
Triethylene Diamine-Clay Complexes as Matrices for Adsorption and Catalytic Reactions
Authors: Mortland M. M. , Berkheiser V.
Published: August 2006

Complexes of 1,4-diazabicyclo [2.2.2] octane (triethylene diamine) with smectite and vermiculite were made for the purpose of exposing the internal surfaces of the clays for adsorption of gases and possible catalytic activity. When the diprotonated form of the amine saturated the exchange sites, internal surfaces of the clays were found to be available to nitrogen, ethane, and 2,4-dimethyl pentane. Proton lability in the smectites was studied with NH3, D2O, and C6D6 experiments. Catalytic function was demonstrated in the conversion of acetonitrile to acetamide in the smectite.
A New Nuclear but Non Radioactive Method for Rapid Elemental Analysis of Clays
Authors: Demortier G. , Hoffelt-Fontaine G.
Published: August 2006

A method using the bombardment of samples with protons and other positive ions of energy in the MeV range is described: the prompt atomic (γ-rays) and nuclear (γ-rays and charged particles) events generated during the bombardment, are detected with energy sensitive solid state detectors: cooled Ge(Li) for γ-rays and hard γ-rays, cooled Si(Li) detectors for soft γ-rays (3–20 keV) and Si-barrier detectors for charged particles. These 3 types of detectors can be simultaneously used for multipurpose experiments. These techniques are particularly useful for simultaneous detection of all the elements of interest in the sample. Comparisons are made with other microtechniques. Analyses of Li, Na, K, Ca, Rb, Cs and Cl exchanged in appropriate chloride solutions have been achieved for several clays (Geisenheim, Isola di Ponza, Layton). A new phenomenon relative to the anion contribution in cation exchangers is observed. A method of profile analysis of Na by resonant nuclear reactions is discussed.
The Influence of Crystallite Size on the Apparent Basal Spacings of Kaolinite
Authors: Trunz Volkmar
Published: August 2006

For very small crystallites diffraction theory shows not only broadening of powder lines, but generally also a shift of the line position, depending on the change of the structure factor over the range of broadening. For decreasing thickness of kaolinite crystals (less than 50 layers) an increasing shift of reflections is found: the lines (001), (002), (004) and (006) are shifted to apparently larger spacings, the lines (003) and (005) to smaller spacings, resulting in a nonintegral series. Presuming a known crystallite size, tables are given for evaluating true spacings from measured values of 2θ.
Origin and Position of Exchange Sites in Kaolinite: An ESR Study
Authors: McBride Murray B.
Published: August 2006

Electron spin resonance (ESR) spectroscopy is used to investigate the nature of exchange sites on kaolinite. ESR spectra of exchangeable Cu2+ and Mn2+ on kaolinite indicate that divalent exchange ions are about 11–12Å apart on kaolinite surfaces and that planar Cu (H2O)42+ ions are oriented parallel to the surfaces. Solution-like spectra for exchangeable Cu2+ and Mn2+ are observed at high relative humidities, suggesting a high degree of mobility of exchange cations on kaolinite surfaces. The evidence seems to eliminate edge sites as being active in cation exchange at least in the acidic range of pH. Similar conclusions are derived from ESR studies of Cu2+-saturated talc and pyrophyllite. It is proposed that most exchange sites arise from ionic substitutions or mineral impurities in phyllosilicates.
Scan Electron Micrographs of Kaolins Collected from Diverse Environments of Origin—I
Authors: Keller W. D.
Published: August 2006

Scan electron micrographs are shown of (1) kaolinite and dickite which crystallized from solution within cavities, (2) kaolinite weathered from clastic primary silicate material, (3) residual kaolinite from primary silicate rock, (4) kaolinite above and below a basal unconformity on granitic rock, and (5) hydrothermally altered kaolinite. The texture of kaolin reflects the environment in which the clay was formed.

Euhedral crystals of kaolin minerals characterize cavity fillings. The weathering environment produces large crystal flakes of kaolinite, expanded books, mats of elongates, high porosity, and low bulk density (less than 2.0). The hydrothermal environment produces smaller crystals, singles, sheaves and packets of crystals, low porosity and high bulk density (2.0 and above).

The interrelationships of genetic environment of kaolin minerals and accompanying texture are discussed in light of available geochemical information.
Effect of Compaction on the Pore Fluid Chemistry of Montmorillonite
Authors: Rosenbaum Michael S.
Published: August 2006

An apparatus for consolidating fine grained materials under controlled conditions of total stress, pore fluid pressure and temperature is described and the variation in chemistry of pore fluid expelled during compaction from a montmorillonitic material at 40°C is reported. The decrease in concentration of dissolved salts in the pore fluid is related exponentially to the effective axial pressure.
The Orientation of Ornithine and 6-Aminohexanoic Acid Adsorbed on Vermiculite from Polarized I.R. ATR Spectra
Authors: Raupach M. , Janik L. J.
Published: August 2006

Determinations of the molecular orientation of ornithine and 6-aminohexanoic acid on the surface of vermiculite using polarized i.r. attenuated total reflectance have shown that the ornithine molecules lay almost flat on the clay surface, except for a C–N bond projecting towards, and hydrogen bonded to, the surface. Ornithine formed two adjacent layers in the interlayer space, whereas 6-aminohexanoic acid formed only one layer. The terminal C-N bond of 6-aminohexanoic acid was at 46° to the surface, the plane of the carbon chain having a tilt of 34°, and the molecular axis sloped at 36° to the surface. The amino acids, thus orientated, were positioned in the interlayer space using van der Waals contact distances and hydrogen bond lengths obtained from i.r. spectra. The i.r. results agreed with two dimensional electron density projections. In the ornithine complex, some of the methylene groups were so close to the clay surface that interaction may have caused the marked reduction observed in the intensity of the C–H stretching vibrations.
Tosudite from the Hokuno Mine, Hokuno, Gifu Prefecture, Japan
Authors: Ichikawa Atsuko , Shimoda Susumu
Published: August 2006

Tosudite was found in the Hokuno pottery stone mine, Gifu Prefecture, Japan. The pottery stone ore body, altered from the Cretaceous rhyolitic rock, is composed of tosudite, interstratified illite-montmorillonite, kaolinite and quartz. Prepared by normal sedimentation method, the specimen is composed of 75.6% tosudite, 24.0% kaolinite and 0.4% quartz. The chemical composition of the specimen is SiO2 45.09%, TiO2 tr., Al2O3 37.31%, Fe2O3 0.94%, MgO 0.41%, CaO 1.94%, Li2O 0.45%, Na2O 0.09%, K2O 0.44%, H2O(−) 1.50% and ignition loss 12.11%. After subtracting the compositions of the impurities, the structural formula of tosudite is given as; interlayer cations K0.23, Na0.07, Ca0.86 + nH2O; ‘gibbsite’ layer Li0.76, Mg0.35, ${\rm{Fe}}_{0.29}^{3 + }$, Al3.34 (OH)12.00; silicate layer Al8.00 [Si13.83 Al2.17] O40.00 (OH)8.00.

Syntheses of tosudite were made from a starting material which is an interstratified illite-montmorillonite obtained from the same ore body. At 450°C, 400atm., reacting for 5 days, a tosudite-like mineral was synthesized.
Stability of Soil Smectite From a Houston Black Clay
Authors: Carson C. D. , Kittrick J. A. , Dixon J. B. , McKee T. R.
Published: August 2006

The stability of smectite separated from a Houston Black clay soil was studied by solubility methods in an acid environment. High Silicon levels (supersaturated with respect to amorphous Si) probably were due to dissolution of the smectite and slow precipitation of amorphous Silicon. Also, mica and vermiculite impurities may have contributed to high solution Si values. Solubility data from equilibrium solutions of various treatments and chemical structural analyses permitted the formulation of a solubility equation. The ΔG°f for the Houston Black smectite computed from pK values was —2433.9 ± 0.8 kcal/mole. The stability of this clay could then be determined by calculations for any desired solution environment. It was found that under some conditions this soil smectite could be more stable than Belle Fourche and Aberdeen montmorillonites. Therefore, it appears that this soil clay has the required stability area in which it can form in nature.
Transformations of Micas in the Process of Kaolinitization of Granites and Gneisses
Authors: Stoch Leszek , Sikora Wanda
Published: August 2006

Micas are described from the kaolin type Tertiary weathering crusts formed on granites and gneisses of Lower Silesia, Poland. In the weathering crust, large scale processes of transformation of micas (muscovite, biotite) take place. Weathering of micas is a gradual transformation of their structures by removal of the mobile cations Mg2+ Fe2+ Fe3+ and finally K +. Muscovite transforms into kaolinite through the intergrowths of two phases, mica and kaolinite. A degradation series, muscovite → mica/montmorillonite → montmorillonite → kaolinite also is observed. Biotite passes directly into kaolinite, but at higher concentrations of K and Al one observes the following sequence of biotite degradation: biotite → dioctahedral mica rich in Fe → dioctahedral mica poor in Fe → kaolinite. This process involves the exchange of Mg2+ and then Fe2+ of octahedral layers by Al3+ less mobile under weathering conditions. In the next stage of degradation, K + removal and kaolinite formation takes place. The micas representing different stages of this transformation, dark green, light-green, and silver-white, have been separated and investigated.
Protonation of Organic Bases in Clay—Water Systems
Authors: Karickhoff Samuel W. , Bailey George W.
Published: August 2006

The extent of protonation of organic bases in clay—water systems depends upon the adsorptive properties of the organo-clay species involved, and upon the structure and degree of hydration of the clay system. Organic molecules that can disperse cationic charge over two or more condensed aromatic rings give rise to greater surface-induced protonation than do single-ring organic molecules with similar solution pKa. Protonation in clay suspensions is frequently far in excess of that predicted on the basis of electrolytic suspension pH and solution pKa of the organic base. For a given organic base, protonation in a clay film exceeds that in the suspended clay system. Protonation in an organo-clay film increases as the film moisture content decreases. The extent of protonation in organo—clay systems varies with cationic species, cationic saturation, and clay type.
Organic Derivatives of Attapulgite—I. Infrared Spectroscopy and X-Ray Diffraction Studies
Authors: Mendelovici E. , Carroz Portillo D.
Published: August 2006

Highly significant differences are observed between the methyl derivatives of attapulgite, produced when this mineral is reacted with (CH3)2Si(OC2H5)2, in the presence or in absence of HCl. In the first case, the corresponding infrared spectra show characteristic absorption bands due to the Si(CH3)2 radicals at 1260, 850 and 800 cm−1 as well as a shoulder at 960 cm−1, the latter assigned to silanol groups. The 850 cm−1 frequency which is usually exhibited by trimethylsilicon compounds is also detected when —O—Si(CH3)2 radicals are grafted in the silicates, but only if HCl is present in the reaction. Neither this band nor the 960 cm−1 shoulder appear in the spectrum of the derivative synthetized in absence of HCl. A comparative study by both i.r. spectroscopy and X-ray diffraction does not reveal structural modifications in attapulgite after it has been methylated in absence of HCl. However, although the i.r. spectra of the HCl-methylated derivatives, prepared at different periods, do not indicate substantial structural perturbations, X-ray diffraction patterns show a gradual weakening of the peaks due to attapulgite, as reaction time increases; the intensity of the (110) order reflection is drastically reduced after a 165 hr attack. The most viable mechanism for the grafting of the dimethylsiloxy units in attapulgite is through the HCl induced silanol sites. When the reaction is taking place in anh. benzene medium (absence of HCl), dimethyldiethoxysilane may be hydrolyzed by a fraction of water contained in attapulgite; the hydrolysis products which do incorporate on the surface of the silicate are identified by i.r. spectroscopy.
Experimental Alteration of a Chlorite into a Regularly Interstratified Chlorite-Vermiculite by Chemical Oxidation
Authors: Ross G. J. , Kodama H.
Published: August 2006

A IIb orthochlorite (brunsvigite), from the chloritic metabasalt in the Middletown Valley of Maryland, was altered to a regularly interstratified chlorite—vermiculite after four months reaction in saturated bromine water on the steambath. The artificial weathering product resembles the regularly interstratified chlorite—vermiculite in a soil in Adams County, Pennsylvania, that has developed in greenstone similar to the chloritic metabasalt in the Middletown Valley of Maryland. The results of this and previous investigations on artificial and natural weathering of chlorites indicate that oxidation of structural Fe2+ is an important reaction in the alteration of chlorites into vermiculitic products. The results also show that IIb orthochlorites, apparently structurally similar but having different Fe2+ contents may react differently under the same weathering conditions. For example the acid oxidation treatment altered a IIb chlorite (diabantite) directly into a vermiculite, whereas the same treatment altered another IIb chlorite (brunsvigite) into a regularly interstratified chlorite—vermiculite. Detailed investigations of the chlorite structures are probably necessary to determine whether or not these alteration processes are structurally controlled.
Effect of Swelling on the Infrared Absorption Spectrum of Montmorillonite
Authors: Lerot Luc , Low Philip F.
Published: August 2006

The i.r. spectra of mixtures of different Na-montmorillonites were determined at several water contents between 2 and 22 g of water/g of montmorillonite. It was found that Si—O absorption is represented by four closely-spaced bands, one of which is pleochroic. The pleochroic band appeared only at higher water contents. All of these bands, excepting that with the highest wave number, shifted in frequency with increasing isomorphous substitution. None of them shifted in frequency with increasing water content.

The absorption coefficient for the principal Si—O absorption decreased with increasing isomorphous substitution but increased with increasing water content. Niether isomorphous substitution nor water content appeared to have any significant effect on absorption due to O—H stretching or H—O—H bending in the interlayer water.

At a critical water content for each montmorillonite, an abrupt change occurred in the absorption coefficient for the principal Si—O absorption. This change was ascribed to a sudden rearrangement of the particles.
Formation of Phyllosilicates and Zeolites from Pure Silica-Alumina Gels
Authors: De Kimpe C. R.
Published: August 2006

The hydrothermal aging of pure silica—alumina gels in presence of 10 ml of 0.1 N sodium hydroxide solution at 175, 150 and 130°C for 8–30 days led to the synthesis of zeolites and the phyllosilicates, beidellite and kaolinite. The solution was neutralized by a partial hydrolysis of the gel which readily reorganized into a prezeolitic material. At pH values ⩾ 9, with 300 or 600 mg of gel, it evolved towards the crystalline zeolites P and S, with low surface area (7–100 m2/g) but high exchange capacity (300–475 m-equiv./100 g). With gel amounts of 600–2400 mg, and pH values of 8–5.5, the prezeolitic material provided rows of O—Si—O—Al—OH which recombined to form the phyllosilicate structures. Surface area increased (170–325 m2/g) but exchange capacity decreased (100–250m-equiv./100 g). The results obtained by various techniques (XRD, DTA, IR) indicated a moderate degree of crystallinity of these phyllosilicates; in addition, X-ray powder diffraction suggested that hk bands were the first to develop.

The positive results obtained with a 0.40 ratio Al2O3 gel compared with the negative results obtained with 0.30 or 0.50 Al2O3 gels indicate that the gel composition is very important for the formation of phyllosilicates under the experimental conditions.
The Nature of TiO2 in Kaolinite
Authors: Weaver Charles E.
Published: August 2006

SEM, TEM, and electron probe studies indicate that the anatase in Georgia kaolins, and probably anatase in general, consists of subspherical particles (TiO2 pellets) 0.05–0.1 µm dia. Some pure anatase aggregates may be pseudomorphic after ilmenite and have a tabular shape, but much of the anatase is formed from Ti that occurs as scattered ions in the octahedral sheets of biotite. When removed from the biotite this material forms TiO2 pellets. These pellets can occur as: single pellets; irregular aggregates; layered aggregates; spherical aggregates; mixed aggregates (with kaolinite); coated aggregates (with kaolinite). Physical energy can be used to break TiO2—kaolinite aggregates, separate single TiO2 pellets from kaolinite plates and remove kaolinite coatings from TiO2 aggregates.

Al and Si are present in all TiO2 aggregates and the Si—Al ratio is lower in the aggregates than in the kaolinite. An amorphous Si—Al compound may be present and act as a cement.

The anatase apparently is formed from Ti that is released from the parent mineral as Ti (OH)4. The Ti (OH)4 precipitates to form an amorphous hydrous oxide gel which dehydrates to form a granular aggregate of small anatase crystals.
New Approach to the Problem of the Interlayer Bonding in Kaolinite
Authors: Więckowski Tadeusz , Wiewióra Andrzej
Published: August 2006

The possibility of recording the absorption band which is related to oscillations of free OH in a superficial plane of the octahedral sheet of kaolinite inspired the present authors to review the problem of cohesion forces in kaolinite. Structural and spectroscopic criteria as applied to kaolinite proved that the cohesion of adjacent kaolinite layers may be estimated in terms of bent hydrogen bonds. Energy calculations were performed with the aid of a Lennard-Jones function using a modified linear model of the hydrogen bonds. The entire energy is composed of four terms described by the general potential function, van der Waals repulsion and an electrostatic attraction. The energy values of the individual terms are within the limits characteristic of each of them.
Quantitative X-ray Powder Diffraction Analyses of Clays Using an Orienting Internal Standard and Pressed Disks of Bulk Shale Samples
Authors: Cody R. D. , Thompson G. L.
Published: August 2006

Quantitative analysis of clay minerals by X-ray powder diffraction requires oriented clays in order to increase detection limits of the analyses. This is achieved commonly either by smear or sedimentation techniques; however, these techniques can lead to poor analytical precision when used with an internal standard because they often produce non-homogeneous internal standard—clay mineral mixtures. Compaction of bulk shale material at 8000 psi in an hydraulic press produces preferred orientations comparable to that produced by smear or sedimentation. When used with a suitable platy internal standard which provides an estimate of clay mineral preferred orientation, excellent analytical precision is achieved routinely. Several lines of experimental evidence indicate that 1–5 µm MoS2 is an ideal orienting internal standard for use with compaction mounts.
Microstructure, Mineralogy and Chemistry of Cambrian Glauconite Pellets and Glauconite, Central U.S.A.
Authors: Odom I. Edgar
Published: August 2006

Glauconite pellets in the Cambrian of the central U.S.A. frequently contain two textural forms of glauconite–aggregate and oriented—which differ in both mineralogy and chemistry. The aggregate glauconite composes the bulk of most pellets and consists of crystals in a nearly random arrangement. The oriented glauconite occurs primarily as rims on the periphery of pellets. It has a honeycomb-like structure—the crystals are oriented with their c-axes tangent to the aggregate-textured cores. Scanning electron photomicrographs show that the aggregate and oriented textures grade one into the other.

The aggregate glauconite has a 1 M structure and less than 5% expandable layers, whereas the oriented form has a 1 Md structure and ∼ 10% expandable layers. The aggregate glauconite contains 5–8% more total iron oxides and 2–3% less Al2O3 than the oriented glauconite. The b-cell dimension of individual samples increases nearly linearly with increasing octahedral Fe3+ + F2+ + Mg content. Chemical and crystallographic variations among various samples are, for the most part, related to the ratio of aggregate to oriented glauconite.

The transition between the texture of the aggregate and oriented glauconite suggests that some glauconite pellets may form by concretionary growth. It is proposed that Cambrian glauconite pellets grew through the repetitive development of a smectite-like clay at the margin of pellets. The smectite was later altered, both chemically and texturally, first to the oriented and then to the aggregate-textured glauconite.
Clay Mineral Stability as Related to Activities of Aluminium, Silicon, and Magnesium in Matrix Solution of Montmorillonite-Containing Soils
Authors: Weaver R. M. , Jackson M. L. , Syers J. K.
Published: August 2006

The influence of geomorphological site characteristics on soil clay mineral stability of montmorillonite-containing horizons of a southern Wisconsin soil catena was interpreted in terms of the solute activity function values of pSi(OH)4, pH-1/2pMg2+ and pH-1/3pAl3+ in suspensions of the separated clay fractions. Montmorillonite stability and/or formation vs that of kaolinite for the soil clays was evaluated by a plot of the solute activity functions on a three dimensional diagram derived for montmorillonite, kaolinite, and gibbsite at constant temperature (25°C) and constant pressure (one atm.). Although all the soil clays contained both montmorillonite and kaolinite, the position of the soil clay solute activity functions in the stability diagram clearly reflected the influence of the geomorphological—geochemical site conditions in which each soil horizon was developed, with corresponding differences in the SiO2/Al2O3 molar ratio of the reactive fraction. Montmorillonite stability positions of the solute activity functions were induced by soils (clays with reactive fractions with SiO2/Al2O3 molar ratios = 3–4) from calcareous or poorly drained horizons, while kaolinite stability positions of the functions were induced by soils (clays with reactive fractions of SiO2/Al2O3 molar ratios = 2) from acid, freely drained horizons.
Interaction between Alkali-Halides and Halloysite: I.R. Study of the Interaction between Alkali-Halides and Hydrated Halloysite
Authors: Yariv S. , Shoval S.
Published: August 2006

Halloysite was mechanically ground in the presence of NaCl, KCl, RbCl, RbCl and CsCl, and i.r. spectra were recorded after various periods of grinding, up to 10 min. Changes in the wave-numbers and sharpness of absorption bands were interpreted using assignments accepted for kaolinite. Diminution of absorption bands of OH groups and the appearance of new bands indicate formation of complexes of halloysite with KCl, KBr, RbCl, and CsCl. Water was essential in the complex formation, which may be formulated:

The amount of the complex formed depended on the salt and the time of grinding. Complex formation requires that the cation be large enough to serve as a “structure breaker” of the interlayer water sheet. Complex formation also requires that the cation be a weak electron acceptor. Grinding also led to changes in the fine structure of the tactoid.

The possibility of using the i.r. spectrum of halloysite as a finger print for identification of the mineral is discussed. It was concluded that NaCl is the most reliable dispersing agent to determine whether or not a mineral sample belongs to the kaolinite group. Disks in RbCl may be used to differentiate between kaolinite and hydrated halloysite.
Analysis of Iron-Bearing Clay Minerals by Electron Spectroscopy for Chemical Analysis (ESCA)
Authors: Stucki J. W. , Roth C. B. , Baitinger W. E.
Published: August 2006

Nontronite and biotite were analyzed by Electron Spectroscopy for Chemical Analysis (ESCA). Both minerals yielded ESCA spectra with well-defined peaks and the elements identified by the ESCA spectra were in good agreement with the molecular formulas. High resolution scans were made of the iron (2p3/2) and oxygen (1s) electron binding energies for oxidized and reduced forms of nontronite and biotite. Binding energies for Fe3+ were observed at 711.8 eV in dithionite-reduced nontronite and in oxidized biotite. Peaks for Fe2+ occurred at 710.0 eV for unaltered biotite, at 709 eV for oxidized biotite and at 708.6 eV for hydrazine-reduced and dithionite-reduced nontronite. The oxygen (1s) peak for unaltered nontronite was skewed to the high energy side of the 530.6 eV maximum, but became more symmetrical as the Fe2+ content increased.
Solubility Diagrams for Explaining Zone Sequences in Bauxite, Kaolin and Pyrophyllite-Diaspore Deposits
Authors: Tsuzuki Yoshiro
Published: August 2006

Solubility diagrams defined by log [Al3+] and log [H4SiO4] are given for hydrous alumina or aluminum silicate minerals which appear in bauxite, kaolin and pyrophyllite-diapore deposits. They are constructed based on thermodynamic data of relevant reactions both at the room temperature and at elevated temperatures.

An aqueous solution reacts to a mineral, in this case K-feldspar, and, by dissolving it, becomes saturated with respect to a certain mineral. This mineral begins to be precipitated and the solution changes its composition as a result of the precipitation as well as further dissolution of the original mineral. Then, it attains saturation with respect to another mineral, which is precipitated thereafter. Thus, different minerals are precipitated in turn.

The sequences of precipitation of minerals can be shown on the diagrams under different conditions. A sequence, aluminum hydroxide → kaolinite or pyrophyllite → silica mineral plus kaolinite or pyrophyllite is expected in a weakly acid solution. In contrast, a sequence, silica mineral → silica mineral plus kaolinite or pyrophyllite is expected in a strongly acid solution. The possibility of application of the sequence of precipitation thus expected to alteration zoning is also discussed.
Surface Charge Variation in Aging Ferric Hydroxide
Authors: Lahann R. W.
Published: August 2006

The variation with time of exchangeable surface charge of amorphous ferric hydroxide in aqueous suspension was monitored by a titration technique. After 120 days, the surface charge of suspensions with initial pH from 8.5 to 10.5 was about one-fourth of the initial value, and goethite had formed from the ferric hydroxide. After the same time interval, the exchangeable surface charge of suspensions with initial pH from 5.5 to 8.0 was about two thirds the original value and the ferric hydroxide was still largely amorphous. The initial rate of crystallization and surface charge reduction increased with initial pH for suspensions with pH from 8.5 to 10.5, whereas the rate of surface charge reduction appeared to be independent of pH for suspensions with initial pH between 5.5 and 8.0. Based on these results it is suggested that at pH from 8.5 to 10.5 ferric hydroxide ages to goethite via a solution stage involving the Fe(OH)4- ion, whereas at pH values below 8.5 ferric hydroxide aging proceeds via mechanisms which do not involve the particle surface or bulk solution.
Free Energy of Formation of Beidellite from Apparent Solubility Measurements
Authors: Misra U. K. , Upchurch W. J.
Published: August 2006

The structural formula for K and Mg saturated beidellite was calculated from the total elemental analysis of the < 0.2 μm clay fraction of the B2t horizon of a Mexico soil. The free energies of formation (ΔGfo) of K-beidellite and Mg-beidellite as determined from their apparent solubilities were -2491.3 and -2484.0 ± 3.2 kcal per mole, respectively. The free energies of formation correspond to a clay mineral structure calculated on the basis of a 24 oxygen cell.
The Interaction Between Roundup (Glyphosate) and Montmorillonite. Part II. Ion Exchange and Sorption of iso-Propylammonium by Montmorillonite
Authors: Shoval S. , Yariv S.
Published: August 2006

The adsorption mechanism of iso-propylammonium (PAH+), the cationic component of Roundup, by various homoionic montmorillonites and the structures of the associations obtained in the interlayer space were investigated, using infrared, X-ray, and carbon analysis methods. Adsorption from aqueous and ethanol solutions of Roundup was studied. The infrared spectra were compared with those obtained by the treatment of montmorillonites with ethanol and CCl4 solutions of the free iso-propylamine (PA). The adsorption of PA from ethanol gives rise to protonation of the amine. PA sorbed from CCl4 solution forms an ammonium-amine association. Adsorption of PAH+ from alcohol solution of Roundup occurs by the mechanism of cation exchange. With transition metal exchangeable cations, PAH+ is sorbed in excess, forming hydrogen bonds between NH3+ groups and hydroxyls resulting from dissociation of water molecules. The process of adsorption of PAH+ from aqueous solutions of Roundup depends on the concentration of the solution. If montmorillonite is reacted with 0.5% solution of Roundup, PAH+ is adsorbed by exchanging metal cations and the adsorption capacity of the clay does not exceed the c.e.c. If the montmorillonite is reacted with 5.0% solution of Roundup, the PAH+ exchanges protons originating from the hydrolysis of the interlayer water. Protons which are transferred from the interlayer space to the water solution are accepted by the anion component of Roundup. The amounts of PAH+ adsorbed from concentrated Roundup solutions are much higher than the cation exchange capacity of montmorillonite. Hydrogen bonds are formed between the ammonium and water or hydroxyl groups on the interlayer space. With the trivalent exchange ions Al and Fe, which tend to polymerize in the interlayer space, excess sorption gives rise to hydrogen bonding of NH3+ to oxygen of the polymer.
Neutron Diffraction from Clay-Water Systems
Authors: Cebula D. J. , Thomas R. K. , Middleton S. , Ottewill R. H. , White J. W.
Published: August 2006

The use of neutron diffraction to determine some of the structural properties of montmorillonite-water systems at low water concentrations is described. The samples were prepared by compression or suction to give clay samples with between one and three molecular layers of water between the plates.

About 10% of the platelets in the clay are randomly oriented. The remainder are partially oriented in the plane of the sample, with an angular spread of 40° about the mean orientation. It is suggested that these oriented domains are formed from the larger platelets present in the system. The Bragg diffraction pattern is better explained by a disordered lattice model rather than by a mixture model with small particles having a well-defined lattice spacing. We have fitted both the intensities of (00l) reflections and the shape of the (001) reflection quantitatively to a model which allows for a Gaussian spread of platelet spacing about a mean value. The half width of the spread is about 10% of the lattice spacing.

No significant structural differences are found between Li, Na, K, and Cs montmorillonites. The method of preparation has no effect on the structural properties of the large platelet particles but does affect the randomly oriented fraction. The lattice spacing of the latter appears to be better defined for samples prepared by compression.

Experiments on the variation of lattice spacing with humidity indicate that the structural model we have used is adequate except at humidities where the system is changing over from one to two, or two to three water layers.
Synthesis of the Trimethylsilylation Derivative of Halloysite
Authors: Kuroda Kazuyuki , Kato Chuzo
Published: August 2006

The trimethylsilyl derivative from halloysite was prepared by the reaction of halloysite powder with a trimethylsilylating reagent. The product was organophilic and the results of its infrared spectrum, X-ray powder diffraction pattern, and elemental analysis indicated that the trimethylsilylation occurred on silanol groups in the tetrahedral layer of halloysite after the acid decomposition of the octahedral layer. The thermal stability of the product was evaluated by means of differential thermal analysis. It was not possible to obtain the organic derivative from kaolinite by the same procedure. It is suggested that the differences in the reactivity between halloysite and kaolinite is due to the difference in susceptibility of the clay minerals to acid attack.
Titration of pH-Dependent Sites of Kaolinite in Water and Selected Nonaqueous Solvents
Authors: Loeppert R. H. , Zelazny L. W. , Volk B. G.
Published: August 2006

K-saturated kaolinite was titrated in 13 different solvents with tetrabutylammonium hydroxide using a combination electrode for potentiometric determination. The titer of base required to reach the final potentiometric endpoint was dependent on the solvent and increased according to the following solvent order in both the presence and absence of excess neutral salt: methanol ⩽ water < ethanol ⩽ 1-propanol < 1-butanol < 2-propanol < DMF < t-butanol < DMSO < pyridine ⩽ acetonitrile ⩽ methylethyl ketone < acetone. With the protic solvents, titratable acidity increased according to decreasing dielectric constant of the solvent and increasing size and/or branching of the aliphatic constituent. The largest titratable acidities were obtained in the dipolar aprotic solvents with negligible basic character (e.g., acetonitrile, acetone, methylethyl ketone). These results are discussed in terms of solvent properties, solvation characteristics of ions in the solvents, and acid-base behavior of crystalline edge sites.