bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption of Cations on Imogolite and their Effect on Surface Charge Characteristics
Authors: Harsh James B. , Traina S. J. , Boyle J. , Yang Ying
Published: August 2006

Noncrystalline aluminosilicates termed allophane and imogolite are common constituents of spodosols, soils derived from volcanic ash, and many inceptisols. The surface charge characteristics of their synthetic analogues may be used to better understand their ion retention properties. In this study, we determined the point of zero salt effect (PZSE) by potentiometric titration of allophanes with Al/Si ratios of 1.12, 1.52, and 2.04 and of imogolite with an Al/Si ratio of 2.02. We also used microelectrophoresis to determine the point of zero charge (PZC) at the particle shear plane for the same materials in CI solutions of Li, Na, Cs, and tetramethyl ammonium. The PZSE decreased with decreasing Al/Si ratio for the allophanes, but the imogolite PZSE was much lower than that of the allophane with 2.04 Al/Si. The PZC was always higher than the PZSE of the same material, especially for imogolite. The results are best explained if cations reside within the hollow tubes of imogolite. This conclusion is supported by a fluorescence study that showed that only quenchers smaller than the inner diameter of the imogolite tube could fully quench Ce-imogolite.
Adsorption and Spectroscopic Studies on the Interactions of Cobalt(III) Chelates with Clays
Authors: Kaneyoshi Masami , Yamagishi Akihiko , Tanaguchi Masahiro , Aramata Akiko
Published: August 2006

The interactions of the following three kinds of racemic and enantiomeric cobalt(III) chelates with montmorillonite and saponite are studied: [Co(en)3]3+ (en = ethylenediamine), [Co(diNOsar)]3+ (diNOsar = (1,8-dinitro-3,6,10,13,16,19-hexaazabicyclo[6,6,6]-eicosane)cobalt(III))and [Co(diAMsar)]3+ (diAMsar = (1,8-diamino-3,6,10,13,16,19-hexaazabicyclo-[6,6,6]eicosane)-cobalt(III)). At neutral pH, these complexes are adsorbed as a trivalent cation up to 90%–100% of the cation exchange capacity of a clay. No difference is observed in the maximum adsorption amount between the racemic and enantiomeric isomers. The basal spacings of the clay-chelate adducts are determined by the X-ray diffraction measurements of non-oriented powder samples: 14.3 Å for [Co(en)3]3+ montmorillonite, 16.5 Å for [Co(diNOsar)]3+ montmorillonite, and 16.9 Å for [Co(diAMsar)]3+ montmorillonite. The results imply that the chelates form a monolayer in the interlayer space. From the one-dimensional Fourier analyses of the diffraction pattern of [Co(diNOsar)]3+ montmorillonite, the chelate is concluded to be adsorbed with its three-fold symmetry axis in parallel with the layer surface. This is in contrast with the previous results of [Ru(phen)3]2+ and [Ru(bpy)3]2+, which are adsorbed with their three-fold symmetry axes perpendicular to the surface. The conclusion is consistent with the angular dependence of the infrared absorption spectrum of the film of the adduct.
Boxwork Fabric of Halloysite-Rich Kaolin Formed by Weathering of Anorthosite in the Sancheong Area, Korea
Authors: Jeong Gi Young , Kim Soo Jin
Published: August 2006

Boxwork fabric in which numerous thin or thick halloysite walls are interconnected into a microscopically porous cellular pattern is widely developed in the halloysite-rich kaolin formed by weathering of anorthosite in Sancheong, Korea. Studies using optical microscopy, scanning electron microscopy, and transmission electron microscopy have been carried out in order to elucidate the detailed features and origin of the boxwork.

In the early stage of weathering, halloysite spheres formed in etch pits on the walls of microstructural discontinuities in the slightly weathered rock. With further weathering, the halloysite spheres grew to discs or flattened globules, which in turn coalesced to form large planar halloysite plates amid narrow fissures. The halloysite plates were detached by dissolution of the plagioclase in groundwater. Continued growth of the halloysite tubes in the plates resulted in the wrinkling of the plates. Finally, the plagioclase was completely dissolved by groundwater, leaving the boxwork of wrinkled halloysite walls and large pores. The relatively high rigidity of the boxwork is due to the compact agglomeration of halloysite tubes within the wrinkled halloysite walls.

Cation balance calculation shows that Al was significantly mobilized during the formation of the boxwork in the weathering environment. The well-developed microfissures, the high dissolution rate of the calcic plagioclase, and the rapid flow of groundwater in a mountainous topography with relatively steep (20°) slope have been the factors controlling the formation of the porous boxwork in the halloysite-rich kaolin of the Sancheong area.
Development of Ammonium-Saponites from Gels with Variable Ammonium Concentration and Water Content at Low Temperatures
Authors: Kloprogge J. Theo , Breukelaar Johan , Jansen J. Ben H. , Geus John W.
Published: August 2006

Ammonium-saponite is hydrothermally grown at temperatures below 300°C from a gel with an overall composition corresponding to (NH4)0.6Mg3Si3.4Al0.6O10(OH)2. The synthetic saponite and coexisting fluid have been characterized by means of X-ray powder diffraction, X-ray fluorescence, Induced Coupled Plasma-Atomic Emission Spectroscopy, thermogravimetric analysis, transmission electron microscopy, CEC determination using an ammonia selective electrode, and pH measurement. In the crystallization model developed, crystallization started with the growth of individual tetrahedral layers with an aluminum substitution not controlled by the A1IV/A1VI ratio in the gel and hydrothermal fluid, on which the octahedral Mg layers can grow. During the synthesis, individual sheets stacked to form thicker flakes while lateral growth also took place. The remaining A1VI partly replaced ammonium as the interlayer cation.
Comparison of I/S Transformation and Maturity of Organic Matter at Elevated Temperatures
Authors: Velde B. , Lanson B.
Published: August 2006

Comparing the state of reaction advancement of I/S (illite content of illite/smectite mixed layer minerals) and organic matter (vitrinite reflectance) in instances of high temperature gradients allows one to observe the evolution of geologic materials under extreme conditions. In a geothermally heated sedimentary series (Salton Sea area, California), both clays and organics have reacted to completion in the temperature gradient range of 200°-400oC/km during heating episodes of 104 years. We observed an instance of rapid heating, through magmatic intrusion into the Meso-Paleozoic eastern Paris Basin sedimentary series in late Permian time, which induced changes in the organic material, but where clays are apparently unaffected.
Implications of Linearly Correlated Oxygen and Hydrogen Isotopic Compositions for Kaolinite and Illite in the Magnus Sandstone, North Sea
Authors: Fallick A. E. , Macaulay C. I. , Haszeldine R. S.
Published: August 2006

Authigenic kaolinite and illite are important diagenetic minerals in the Magnus Sandstone, a giant oil reservoir in the northern North Sea. These clay minerals, separated from three wells, show considerable ranges in their oxygen isotopic composition (δ8OSMOW = +9 to + 16%) and hydrogen isotopic composition (δDSMOW = - 55 to - 105%). The variations in δ18O and δD are positively linearly correlated with a high degree of statistical significance for both kaolinite and illite:

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Formation of the clays in a pore fluid of uniform isotopic composition over a range of temperatures appears unlikely. It is suggested that the observed relationships between clay mineral δ18O and δD are perhaps best explained by a model of precipitation at more or less constant temperature from pore fluids which varied isotopically across the oilfield. The isotopic composition of the formation waters would then lie along the line: δDw = 6.2 δl8Ow - 50. This is most plausibly interpreted as a mixing line with suggested minimal endmembers at (δ18O, δD) values of (+4, -24) and (-4, -76). The first of these represents reasonable isotopic values for Magnus Sandstone formation waters. Although δ18O of the second is compatible with an evolved Cretaceous meteoric water, its δD value is difficult to understand in the context of the model.
Changes in Particle Morphology During Illitization: An Experimental Study
Authors: Whitney Gene , Velde Bruce
Published: August 2006

Smectite was reacted at several temperatures between 200°C and 500°C to produce interstratified illite/smectite (I/S) with different proportions of expandable layers. Dispersed and sedimented products were examined using a transmission electron microscope. Particle size and aspect ratio showed no systematic change as a function of reaction extent during R0 illitization. However, particles exhibited rounded edges during the early stages of the reaction, suggesting some dissolution of primary smectite. Additionally, increasing particle contrast in the electron beam suggests thickening of particles with increasing reaction extent. The thickening of particles is thought to be produced by the nucleation and precipitation of secondary illite layers on primary smectite layers. In the most extensively reacted I/S, particles have become aggregated into clumps or quasicrystals by lateral growth of illite layers. Internal uniformity of crystallographic alignment of individual growing crystals within each aggregate was reflected in the increasing frequency of 60° and 120° interfacial angles within each aggregate. In highly illitic I/S, these aggregates took on an overall euhedral form and became crystallographically contiguous, producing single crystal electron diffraction patterns.
Rietveld Refinement and Fourier-Transform Infrared Spectroscopic Study of the Dickite Structure at Low Temperature
Authors: Bish David L. , Johnston Clifford T.
Published: August 2006

The full structure of dickite from St. Claire, Pennsylvania, including hydrogen atoms, was refined in space group Cc using time-of-flight neutron powder diffraction data obtained at 12 K and Rietveld refinement/difference-Fourier methods (Rwp = 2.62%, reduced χ2 = 1.915, 113 variables, a = 5.1474(6)Å, b = 8.9386(10)Å, c = 14.390(2)Å, and ß = 96.483(1)°). The non-hydrogen structure is essentially identical to published structures for dickite, but the hydrogen positions are distinct. The inner hydroxyl group is approximately parallel to the (001) plane, inclined by 1.3° towards the tetrahedral sheet. Contrary to published low-temperature infrared (IR) spectra, there is no evidence that dickite possess lower symmetry at low temperatures although there is tentative evidence for statistical occupancy of H3 on more than one site. Low-temperature IR spectra of St. Claire and Wisconsin dickites do not show evidence for more than four hydroxyl groups and are consistent with the reported structure. Upon cooling from 300 to 15 K, the position of the OH3 stretching band increased from 3710 to 3731 cm−1. This large, positive shift in frequency was attributed to the increase in the internuclear O-H3 ⋯ O distance upon cooling. The frequency of the 3655 cm−1 band initially decreased by 2 cm−1 to 3653 cm−1 upon cooling from 300–125 K; however, the band increased in frequency by 1 cm−1 upon further cooling to 15 K. This unusual change in frequency upon cooling is consistent with the assignment of this band to OH2 and OH4. The position of the OH1 stretching band decreased from 3622 to 3620 cm−1 upon cooling, which was attributed, in part, to the observed increase in the Al-O(H1)-Al angle at low temperature.
The Surface Coulomb Energy and Proton Coulomb Potentials of Pyrophyllite {010}, {110}, {100}, and {130} EDGES
Authors: Bleam William F. , Welhouse Gereon J. , Janowiak Mark A.
Published: August 2006

This paper describes structural models of four pyrophyllite edge faces: {010}, {110}, {100}, and {130}. Water molecules chemisorbed to Lewis acid sites stabilize edge faces both crystallochemically and electrostatically. The detailed assignment of protons to surface oxygens and the orientation of OH bond-vectors both influence the surface Coulomb energy.

The geometry chosen for the electrostatic calculations was infinite pyrophyllite ribbon the thickness of a single phyllosilicate layer and the width of 50 to 70 unit cells. Such a phyllosilicate ribbon has only two edges, a top and bottom, which were simulated using the edge-face models mentioned above. About 94% of the surface Coulomb energy is confined to the edge-face repeat unit. The surface Coulomb energies of the four edge faces are on the order of 2–3 nJ/m, varying ± 1 nJ/m with proton assignment. The Coulomb potential, measured either within the layer or parallel to the layer, has a distinct negative trend near the edge face that can be traced to chemisorbed water molecules. Finally, the correlation between proton Coulomb potentials at the edge face and the coordination environment of the protons is poor, obscured by long-range interactions.
Preparation and Characterization of Hydroxy-Feal Pillared Clays
Authors: Zhao Dongyuan , Wang Guojia , Yang Yashu , Guo Xiexian , Wang Qibin , Ren Jiyao
Published: August 2006

Solutions containing hydroxy-FeAl oligocations (HFA) were prepared by two procedures: (1) treatment of a mixture of FeCl3 and AlCl3 with aqueous Na2CO3, followed by aging of the product and (2) preliminary preparation and aging of hydroxy-Al13 oligocations followed by reaction of the latter with aqueous FeCl3. Ion-exchange of Na-montmorillonite with HFA yield pillared clay (designated as FeAl-PILC) with d(001) values of 1.98–1.56 nm and a surface area of 230 m2/g. The pillar structure, thermal stability, surface acidity, and reduction behavior of the pillared clays were determined by 27Al-NMR, XRD, DTA, Mössbauer spectroscopy, Py-IR, TPD, TPR. Fe/Al ratios greatly affect the pillar structure, surface area and thermal stability of FeAl-PILC. The pillar in FeAl-PILC with Fe/Al ratio <0.5 has a Keggin structure, similar to that of Al-PILC, but the pillar structures of FeAl-PILC with Fe/Al ≥0.5 are the ferric tripolymer species similar to those of Fe-PILC. The basal spacings, surface area, and thermal stability are decreased with increasing Fe/Al ratio. There is relatively strong interaction between Fe and Al in the pillars. The interaction is enhanced with decreasing Fe/Al ratio. Reduction of the Fe phase in FeAl-PILC was reduced by the interaction of Fe with Al.
Pillared Clays Prepared from the Reaction of Chromium Acetate with Montmorillonite
Authors: Jimenez-Lopez Antonio , Maza-Rodriguez Jose , Olivera-Pastor Pascual , Maireles-Torres Pedro , Rodriguez-Castellon Enrique
Published: August 2006

Refluxing chromium (III) acetate with a Na+-montmorillonite suspension gives rise to the intercalation of linear Cr(III) polyhydroxo-acetate oligomers. Thermally stable chromia pillared mont-morillonite materials are obtained upon calcination under ammonia up to 625°C, and basal expansions up to 6 Å are maintained. The porous materials retain high surface areas (366–464 m2 g−1), a micropore volume of 0.1 cm3 g−1 and narrow pore size distributions centered between 7.5 and 12 Å. The most thermally stable materials in air were those prepared under ammonia at 625°C, containing NH4+ as the exchangeable ion.
Effect of Prolonged Aging on the Transformation of Short-Range Ordered Aluminum Precipitation Products Formed in the Presence of Organic and Inorganic Ligands
Authors: Violante A. , Gianfreda L. , Violante P.
Published: August 2006

More than 40 samples of Al precipitation products formed in the presence of organic (aspartic, oxalic, citric, tartaric, malic, salicylic, and tannic acid, and acetylacetone) and inorganic (chloride, sulfate and phosphate) ligands, which were short-range-ordered materials after 2–5 months of aging, were analyzed by X-ray diffraction (XRD), infrared spectroscopy (IR), and transmission electron microscopic (TEM) examination after prolonged periods of aging in the mother liquids (from 7–15 years). Noncrystalline materials were found after 7–10 years of aging in samples formed in the presence of citrate, tartrate, and tannate at pH ≤ 8.0 and at ligand/Al molar ratios (R) ranging from 0.05–0.1; they were found as well in the presence of phosphate and malate at ligand/Al molar ratios from 0.1–0.5. Poorly crystalline Al-oxyhydroxides (pseudoboehmite) without Al(OH)3 polymorphs were found in solutions with a wide range of pH (from 6.0–11.0) in the presence of tartrate, citrate, tannate, malate, salicylate, sulfate, and phosphate after 7–15 years. The crystallinity of these samples was indeed very poor. On the contrary, gibbsite formation was observed in samples formed at pH 7.0 or 8.0 in the presence of oxalate (R = 0.1 or 1.0), aspartate (R = 0.1 and 0.5), malate (R = 0.03 or 0.17), salicylate (R = 0.05), and in samples containing very high concentrations of chloride (R = 700 or 1000). Finally, the formation of gibbsite was promoted in the presence of montmorillonite, but some samples at pH ≤ 6.0 in the presence of citrate (R = 0.1), tartrate (R = 0.1), or tannate (R = 0.02 or 0.1) showed after 6 years of aging interstratification of OH-Al species in the interlayers of the clay mineral and complete lack of Al(OH)3 polymorphs.
Swelling Properties of Microbially Reduced Ferruginous Smectite
Authors: Gates W. P. , Wilkinson H. T. , Stucki J. W.
Published: August 2006

Structural Fe in ferruginous smectite (sample SWa-1, Source Clays Repository of the Clay Minerals Society) was reduced by a mixture of five Pseudomonas species of bacteria in a defined Fe-free medium to determine the effect of microbial reduction on clay swelling. Iron(II), total Fe, and gravimetric water content (mw/mc) were determined in clay gels equilibrated at applied pressures of 0.1, 0.3, and 0.5 MPa. The water content of microbially reduced SWa-1 decreased at all three applied pressures as the Fe(II) content approached about 0.8 mmol Fe(II)/g-clay. As Fe(II) increased from 0.8 mmol/g-clay, however, further change in mw/mc was negligible. Concurrent with microbial reduction of structural Fe was a significant decrease in the swelling pressure (PI) of SWa-1: for example, when mw/mc = 1.2 (g/g), PI changed from 0.47 MPa at Fe(II) = 0.2, to 0.19 MPa at Fe(II) = 0.9 mmol/g-clay. Both biologically and chemically reduced smectites displayed lower values of mw/mc and a concurrent decrease in II as Fe(II) content increased, but the effect of Fe(II) on mw/mc was greater for the microbially reduced smectites at all applied pressures.
Size of Mica Domains and Distribution of the Adsorbed Na-Ca Ions
Authors: Lebron I. , Suarez D. L. , Amrhein C. , Strong J. E.
Published: August 2006

Mica domains have received less attention in the literature than smectite quasi-crystals. This study was conducted to determine whether mica crystals form domains in suspension, the conditions in which those domains exist, and the distribution of adsorbed Na and Ca ions in the domains. Particle size distributions and electrophoretic mobilities (EM) of Silver Hill illite in suspension densities of 0.5 g liter−1 were determined by photon correlation spectroscopy (PCS). Solutions at salt concentration from 2 to 10 mmolc liter−1, sodium adsorption ratio (SAR) from 0 to ∞ (mmol liter−1)0.5, and pH values 5, 7, and 9 were used to prepare the clay suspensions. The particle size of Silver Hill illite suspensions showed a bimodal distribution. Through PCS measurements at low angles, the second peak of the bimodal distribution of the illite was found to be associated with the rotational movement of the b-dimension of the particles. Illite domains broke down in the range of SAR 10 to 15 (mmol liter−1)0.5 equivalent to exchangeable sodium percentages (ESP) of 13 to 18. Illite thus demonstrates a similar stability to smectites that require ESP ≈ 15 to disaggregate quasi-crystals. The EM of the illite particles increased drastically when the SAR increased from 2 to 10 (mmol liter−1)0.5. This increase in EM could not be explained exclusively by the change in the particle size. Cation demixing is required to explain the increase of the zeta potential at the shear plane. The EM of the Silver Hill illite was doubled when the pH increased from 5 to 9 at SAR > 15, but no pH effect was found when SAR < 15. The effect of pH on the EM at SAR values > 15 can be understood if we consider that at SAR > 15 most of the particles are single platelets. The relative importance of variable charge on single platelets or crystals is apparently greater than on domains because the pH affected the mobility of the individual crystals but not the mobility of the domains. The combination of particle size distribution and EM data gives additional information about the zero point of charge of the variable charge, also called point of zero net proton charge (PZNPC) of the clay. For Silver Hill illite, we estimate a PZNPC value between 5 and 7.
Analyses of Palygorskites and Associated Clays from the Jbel Rhassoul (Morocco): Chemical Characteristics and Origin of Formation
Authors: Chahi Azzedine , Duplay Joelle , Lucas Jacques
Published: August 2006

The “Formation Rouge” from the Jbel Rhassoul in Morocco is composed of detrital sediments which have a lacustrine origin. The clays contained in the less than 2 µm fraction of the sediments are detrital phengites and illites, illite/smectites or smectites, and palygorskite. Due to the presence of well preserved long fibers, the palygorskite could not have been transported. They are authigenic and must have formed directly by precipitation from solutions rich in Mg and Al. The detrital illites are impoverished in K and tetrahedral Al. The illite/smectites or smectites, on the contrary, are K-rich but have a low tetrahedral charge. They are also richer in Mg and Fe and have a different crystal size, composition, and crystallinity from the illites. They most probably formed by crystallization, similar to the palygorskites, directly from the solution. The Al could have been provided by the detrital illite, which may have been unstable in an alkaline environment and released K and Al to the solutions.
The Electrophoretic Mobility of Imogolite and Allophane in the Presence of Inorganic Anions and Citrate
Authors: Su Chunming , Harsh James B.
Published: August 2006

The purpose of this study was to investigate bonding mechanisms of representative inorganic anions and citrate with imogolite and allophane using electrophoresis. The electrophoretic mobility (EM) of synthetic imogolite and allophanes with Al/Si molar ratios of 2.02, 1.64, and 1.26 was determined in 0.001 and 0.01 M sodium solutions. The highest point of zero mobility (PZM) values for imogolite and the highest point of zero charge (PZC) values for allophane occurred in the presence of ClO4, NO3, Br, I, and Cl. Below the PZM and PZC, Cl and I lowered the EM relative to the other anions but did not shift the PZM and PZC significantly. This indicates that Cl and I formed more outer-sphere complexes than the other ions. The EM of imogolite and allophane was negative at pH < 6 in 0.001 and 0.01 M NaF probably due to a phase change. We observed the formation of cryolite (Na3AlF6) with transmission electron microscopy (TEM) and X-ray diffraction (XRD) in the NaF systems at low pH. Conversely, phosphate at 0.001 and 0.01 M concentrations lowered both the PZM and the EM in imogolite and both the PZC and the EM in allophane compared with ClO4. Phosphate-treated allophane had the same PZC as a synthetic amorphous aluminum phosphate. The PZM values of imogolite and allophane with 2:1 Al/Si in 0.0001 M Na-citrate were 10.9 and 5.9, respectively. At pH 7.3, Na-citrate lowered allophane EM more than it lowered imogolite EM relative to ClO4.

The EM in NaClO4 and Na2SO4 was reversible by forward- and back-titration with NaOH and HClO4, indicated that ClO4 and SO4 were not specifically adsorbed. Chloride likely formed more outer-sphere complexes than ClO4. Imogolite EM and allophane EM in dilute NaF and NaH2PO4 solutions were not reversible, indicating either surface inner-sphere complexes or surface precipitates of aluminum fluoride and amorphous aluminum phosphate-like materials on these minerals. Sulfate gave a lower EM than the monovalent anions, implying a greater tendency to form outer-sphere complexes. Citrate appeared to form inner-sphere complexes on both imogolite and allophane, but formation was concentration-dependent. The tendency of anions to form surface complexes with imogolite and allophane is consistent with the tendency of anions to form soluble aluminum complexes.
Polytype Diversity of the Hydrotalcite-Like Minerals II. Determination of the Polytypes of Experimentally Studied Varieties
Authors: Bookin A. S. , Cherkashin V. I. , Drits V. A.
Published: August 2006

Polytype diversity of hydrotalcite-like minerals is mainly a function of the nature of the interlayer anion. Among the varieties with CO32− anions, only two- and three-layer polylypes having the same structure as manasseite and hydrotalcite have been confirmed. Stichtite and reevesite, which have been previously identified as six-layer polytypes, are in fact three-layer polytypes.

Among SO42− varieties, one-layer and three-layer polytypes have been identified, but the one-layer types are only present in more hydrated minerals with larger interlayer spacings. The three-layer varieties are of three different polytypes, with both P- and O-types of interlayers. Both rhombohedral and hexagonal varieties exist. Interlayer type may change during hydration-dehydration or anion exchange. Thus, in contrast with the CO32−-bearing minerals, a complete description of the polytype of the SO42−-bearing minerals cannot be made by simply indicating the number of the brucite-like layers in the unit cell.

The two-layer unit cell seen in refined crystal structures of some minerals with SO42− interlayers is not due to a doubled periodicity of alternation of brucite-like layers but to periodicity of interlayer anions, or layer cations.
Diagenetic Kaolinite/Dickite (Betic Cordilleras, Spain)
Authors: Ruiz Cruz M. D. , Moreno Real L.
Published: August 2006

The lower Permo-Triassic sediments of the Maláguide Complex contain abundant dickite. Whole rocks were studied by optical microscopy, scanning electron microscopy, and X-ray powder diffraction. The 2–20 µm and < 2 µm size fractions were extracted and analyzed by scanning and transmission electron microscopy, X-ray powder diffraction, infrared spectroscopy, differential thermal analysis, and thermogravimetry.

In the coarse-grained samples, the 2–20 µm size fraction consisted of well-crystallized dickite associated with minor quantities of kaolinite, illite, quartz, and hematite. XRD patterns of the fine-grained samples and the <2 µm fractions showed the existence of well-crystallized minerals in which several reflections of dickite (11l, 02l) were absent and the 132/13$\bar 2$ reflections were shifted. These patterns suggest the presence of an intermediate member between well-crystallized dickite and well-crystallized kaolinite. Only locally high-order reflections are present at 10.5 Å and 18–22 Å. DTA and IR data agree with those from XRD.

The observed compositional and structural variations are a function of the lithology and the particle size of the sample. The sequence kaolinite → kaolinite/dickite → dickite is proposed for the development of these materials during Alpine metamorphism.
Layer Silicates from Serpentinite-Pegmatite Contact (Wiry, Lower Silesia, Poland)
Authors: Jelitto J. , Dubińska E. , Wiewióra A. , Bylina P.
Published: August 2006

Highly tectonized contact between serpentinite and younger pegmatite in the magnesite mine of Wiry contains various layer silicates. Vermiculite, chlorite, smectite, and interstratified mica-vermiculite were recognized by means of routine XRD examination. Two three component interstratifications of mica-vermiculite-chlorite and chlorite-swelling chlorite-smectite were identified by a combined procedure of deconvolution of the XRD patterns and simulation of XRD tracings. A mineral with large diffraction maxima, displaying “chlorite intergrade” characteristics, appeared to be a mixture of chlorite, mixed layer chlorite-smectite, and vermiculite. Polytypes of phyllosilicates were determined by the X-ray transmission method. Due to the heritage of parent mineral polytype structure by transitional products of alteration, two distinct sequences of layer silicates were observed: one formed from trioctahedral mica (vermiculite, mixed layer mica-vermiculite); and one evolved from chlorite (e.g., mixed layer chlorite-swelling chloritesmectite). A tentative scheme of the primary contact zone structure, not obscured by subsequent brittle tectonics either by transformation of layer silicates, is proposed.
Multiobjective Inverse Modeling for Soil Parameter Estimation and Model Verification
Authors: Mertens J. , Stenger R. , Barkle G. F.
Published: August 2006

Due to the exponential increase in computational power and increasing awareness of problems associated with vadose zone parameter estimations based on laboratory and in situ measurements during the last decades, the process of automatic model calibration against laboratory or field data is being increasingly used. This is often referred to as inverse modeling and has as a major limitation the inability to identify a single optimal parameter set. A coupled HYDRUS1D‐SCE (shuffled complex evolution) simulation global optimization technique was developed and its suitability for multiobjective inverse modeling evaluated. In particular, the trade‐off between goodness of fit against leachate volume and soil moisture content in unirrigated and irrigated lysimeters was evaluated. After identification of the most sensitive model parameters using a Monte Carlo based sensitivity analysis, the technique was capable of finding effective Pareto optimal parameter sets that well simulated leachate volume and soil moisture content in both unirrigated and irrigated lysimeters. The parameter variation along the Pareto fronts was large and differences existed between soil hydraulic parameter distributions along the Pareto fronts of the irrigated and unirrigated treatments. The multiobjective optimization technique was then adopted for the verification of the suitability of the conceptual model of equal parameter sets for both treatments. The technique was able to objectively reject the hypothesis of equal parameter sets for both treatments. This is probably due to (i) physical parameter changes with time due to the effect that long‐term irrigation has on soil structure, and (ii) differences in acting transport mechanisms between the unirrigated and irrigated lysimeters.
Effective Parameter Functions for the Richards Equation in Layered Porous Media
Authors: Neuweiler Insa , Eichel Hartmut
Published: August 2006

Upscaling of the Richards equation is important for large‐scale modeling of water flow in the unsaturated zone. We derive an upscaled model for Richards' equation in a layered porous medium. Homogenization theory is applied to derive the upscaled equations for slow flow processes. Two flow regimes are compared. The first flow regime is quantified by small Bond numbers, meaning forces due to pressure gradients are dominant on the small scale. The second flow regime is quantified by large Bond numbers, meaning that forces due to pressure gradients and gravity contribute equally on the small scale, while the large scale is dominated by gravity forces. The case of intermediate Bond numbers is also addressed. We compare the effective relative permeability function and the effective capillary pressure head–saturation function for both flow regimes. In the case of small Bond numbers the effective curves can be derived based on capillary equilibrium. The procedure to calculate effective curves is then quite simple. In the case of large Bond numbers the procedure is more complex. However, comparing effective curves of different test cases showed that the difference between the effective curves for different Bond numbers is not that large for moderate parameter contrasts and when the gradients of the capillary–saturation curve do not become too small. The effective parameter functions calculated with a capillary equilibrium assumption are therefore often a good estimate.
Scaling Approach to Deduce Field Unsaturated Hydraulic Properties and Behavior from Laboratory Measurements on Small Cores
Authors: Basile A. , Coppola A. , De Mascellis R. , Randazzo L.
Published: August 2006

Hydraulic properties should be determined at the scale of the process modeled. The methods to hydraulically characterize a soil in situ remain extremely difficult to implement, requiring measurements of water content and pressure head with adequate time–depth resolution. We recently proposed a method that reduced the number of field measurements required for complete field hydraulic characterization. In this paper, we extend the previous method to cases where the only available information consists of laboratory hydraulic properties, along with a measurement of the maximum water content in the field, whose value depends on the way the wetting of the porous medium is performed. Specifically, the field hydraulic parameters were estimated with a scaling procedure accounting for the ratio between the total porosity estimated by the maximum water content in the laboratory and the partial porosity effectively involved in the field, as estimated by the field‐measured maximum water content. The scaling method was evaluated with data from four soils (three volcanic sandy loam soils and one silty clay loam soil). Soil hydraulic properties were measured both in situ by a field internal drainage test and in the laboratory in an evaporation experiment (Wind's method). Scaling‐based hydraulic properties were also compared with those estimated by applying a simplified method based on the unit‐gradient water flow assumption where only water content measurements performed during the internal drainage test were of concern. The hydraulic properties estimated with the scaling method were compared with the measured ones and with those from the unit‐gradient method in terms of the Relative Mean Error (RME) and Relative Root Square Mean Error (RRMSE). The scaling method proved to be especially effective when applied to the three sandy loam soils, where scaled retention and hydraulic conductivity curves to a large extent reproduced those measured in the field. For the silty clay loam soil, appropriate results were observed only for the water retention curve, while poorer scaled hydraulic conductivity was obtained.
Quantifying the Pore Size Spectrum of Macropore‐Type Preferential Pathways under Transient Flow
Authors: Kung K.‐J.S. , Kladivko E. J. , Helling C. S. , Gish T. J. , Steenhuis T. S. , Jaynes D. B.
Published: August 2006

It is well known that there is a spectrum of pores in a soil profile. The conventional use of a single lumped value of soil hydraulic conductivity to describe a spectrum of hydraulically active pores may have unintentionally impeded the development of field‐scale chemical transport theory and perhaps indirectly hindered the development of management protocols for chemical application and waste disposal. In this study, three sets of four field‐scale tracer mass flux breakthrough patterns measured under transient unsaturated flow conditions were used to evaluate the validity of an indirect method to quantify equivalent pore spectra of macropore‐type preferential flow pathways. Results indicated that there were distinct trends in how pore spectra of macropore‐type preferential flow pathways changed when a soil profile became wetter during a precipitation event. This suggests that the indirect method has predictive value and is perhaps a better alternative to the lumped soil hydraulic conductivity approach in accurately determining the impact of macropore‐type preferential flow pathways on water movement and solute transport under transient unsaturated flow conditions.
Polymorphisms in the Glucokinase-Associated, Dual-Specificity Phosphatase 12 (DUSP12) Gene Under Chromosome 1q21 Linkage Peak Are Associated With Type 2 Diabetes
Authors: Das Swapan Kumar , Chu Winston S. , Hale Terri C. , Wang Xiaoqin , Craig Rebekah L. , Wang Hua , Shuldiner Alan R. , Froguel Philippe , Deloukas Panos , McCarthy Mark I. , Zeggini Eleftheria , Hasstedt Sandra J. , Elbein Steven C.
Published: August 2006

Linkage of type 2 diabetes to chromosome 1q21-q23 is well replicated across populations. In an initial 50-kb marker map (580 markers) across the linked region, one of the two strongest associations observed in Utah Caucasians was at marker rs1503814 (P < 0.00001 in pools, P < 0.004 in individuals). Based on this association, we typed additional markers and screened for sequence variation in the nearby DUSP12 gene. The strongest associations mapped to a highly conserved nongenic sequence just telomeric to rs1503814 and extended 10 kb telomeric through the DUSP12 gene and into the 5′ end of the adjacent ATF6 gene. No coding variant could explain the association in the DUSP12 gene. An extended haplotype encompassing markers from −8,379 to +10,309 bp relative to the ATG start was more common in Caucasian case (0.381) than control subjects (0.285, P = 0.005) and was uniquely tagged by a 194-bp allele at either of two simple tandem repeat variants or by the T allele at marker +7,580. Markers −8,379 and +7,580 were nominally associated with type 2 diabetes in African-American subjects (P < 0.05), but with different alleles. Marker rs1503814 was strongly associated with postchallenge insulin levels among family members (P = 0.000002), but sequence variation in this region was not associated with type 2 diabetes in three other populations of European ancestry. Our data suggest that sequences in or upstream of DUSP12 may contribute to type 2 diabetes susceptibility, but the lack of replication suggests a small effect size.
Exercise Improves Insulin and Leptin Sensitivity in Hypothalamus of Wistar Rats
Authors: Flores Marcelo B.S. , Fernandes Maria Fernanda A. , Ropelle Eduardo R. , Faria Marcel C. , Ueno Mirian , Velloso Lício A. , Saad Mario J.A. , Carvalheira José B.C.
Published: August 2006

Prolonged exercise of medium to high intensity is known to promote a substantial effect on the energy balance of rats. In male rats, moderately to severely intense programs lead to a reduction in food intake. However, the exact causes for the appetite-suppressive effects of exercise are not known. Here, we show that intracerebroventricular insulin or leptin infusion reduced food intake in exercised rats to a greater extent than that observed in control animals. Exercise was associated with a markedly increased phosphorylation/activity of several proteins involved in leptin and insulin signal transduction in the hypothalamus. The regulatory role of interleukin (IL)-6 in mediating the increase in leptin and insulin sensitivity in hypothalamus was also investigated. Treatment with insulin or leptin markedly reduced food intake in exercised rats that were pretreated with vehicle, although no increase in sensitivity to leptin- and insulin-induced anorexia after pretreatment with anti–IL-6 antibody was detected. The current study provides direct measurements of leptin and insulin signaling in the hypothalamus and documents increased sensitivity to these hormones in the hypothalamus of exercised rats in an IL-6–dependent manner. These findings provide support for the hypothesis that the appetite-suppressive actions of exercise may be mediated by the hypothalamus.
Halofenate Is a Selective Peroxisome Proliferator–Activated Receptor γ Modulator With Antidiabetic Activity
Authors: Allen Tamara , Zhang Fang , Moodie Shonna A. , Clemens L. Edward , Smith Aaron , Gregoire Francine , Bell Andrea , Muscat George E.O. , Gustafson Thomas A.
Published: August 2006

Halofenate has been shown previously to lower triglycerides in dyslipidemic subjects. In addition, significant decreases in fasting plasma glucose were observed but only in type 2 diabetic patients. We hypothesized that halofenate might be an insulin sensitizer, and we present data to suggest that halofenate is a selective peroxisome proliferator–activated receptor (PPAR)-γ modulator (SPPARγM). We demonstrate that the circulating form of halofenate, halofenic acid (HA), binds to and selectively modulates PPAR-γ. Reporter assays show that HA is a partial PPAR-γ agonist, which can antagonize the activity of the full agonist rosiglitazone. The data suggest that the partial agonism of HA may be explained in part by effective displacement of corepressors (N-CoR and SMRT) coupled with inefficient recruitment of coactivators (p300, CBP, and TRAP 220). In human preadipocytes, HA displays weak adipogenic activity and antagonizes rosiglitazone-mediated adipogenic differentiation. Moreover, in 3T3-L1 adipocytes, HA selectively modulates the expression of multiple PPAR-γ–responsive genes. Studies in the diabetic ob/ob mouse demonstrate halofenate’s acute antidiabetic properties. Longer-term studies in the obese Zucker (fa/fa) rat demonstrate halofenate’s comparable insulin sensitization to rosiglitazone in the absence of body weight increases. Our data establish halofenate as a novel SPPARγM with promising therapeutic utility with the potential for less weight gain.
Variant of Transcription Factor 7-Like 2 (TCF7L2) Gene and the Risk of Type 2 Diabetes in Large Cohorts of U.S. Women and Men
Authors: Zhang Cuilin , Qi Lu , Hunter David J. , Meigs James B. , Manson JoAnn E. , van Dam Rob M. , Hu Frank B.
Published: August 2006

Emerging evidence indicates that variation in the transcription factor 7-like 2 (TCF7L2) gene may play a role in the pathogenesis of type 2 diabetes. In a prospective, nested, case-control study (n = 3,520) within the Nurses’ Health Study (687 type 2 diabetic case and 1,051 control subjects) and the Health Professionals Follow-up Study (886 case and 896 control subjects), we examined the association of a common variant of the TCF7L2 gene (rs12255372 [T/G]) with type 2 diabetes risk among Caucasians. Frequencies of the T-allele were significantly higher among case than control subjects; each copy of the T-allele was associated with a 1.32-fold (P = 0.0002) and 1.53-fold (P < 0.0001) increased type 2 diabetes risk in women and men, respectively. The odds ratios (95% CI) associated with homozygous carriers of the T-allele were 1.86 (1.30–2.67) and 2.15 (1.48–3.13) in women and men, respectively. Population-attributable risks for diabetes associated with the T-allele were 14.8 and 22.3% for women and men, respectively. In a meta-analysis of 3,347 case and 3,947 control sujects, each copy of the T-allele was associated with a 1.48-fold increased risk (P < 10−16). Our findings confirm that the TCF7L2 gene represents an important locus for predicting inherited susceptibility to type 2 diabetes.
Ferritin and Transferrin Are Both Predictive of the Onset of Hyperglycemia in Men and Women Over 3 Years
Authors: Fumeron Frédéric , Péan Franck , Driss Fatti , Balkau Beverley , Tichet Jean , Marre Michel , Grandchamp Bernard ,   for the DESIR Study Group
Published: August 2006

OBJECTIVE—The aim of the present work was to determine, in a cohort of men and women, whether ferritin and transferrin were associated with glucose metabolism and whether they were predictive of the onset of hyperglycemia (impaired fasting glycemia or type 2 diabetes) after 3 years of follow-up.

RESEARCH DESIGN AND METHODS—Among 4,501 subjects from the French Data from an Epidemiological Study on the Insulin Resistance Syndrome (DESIR) cohort, 1,277 subjects (644 men and 633 women) were randomly selected for the analysis of iron biomarkers at baseline and at 3 years. In addition, to determine whether these parameters were relevant to pathological changes, all 231 subjects normoglycemic at baseline and hyperglycemic 3 years later were analyzed for iron biomarkers.

RESULTS—At baseline, plasma ferritin concentrations were positively correlated with fasting insulin and fasting glucose in the 1,277 subjects. Although transferrin and ferritin were negatively correlated, transferrin was also positively correlated with fasting insulinemia. Baseline ferritin concentration was an independent predictor of an increase in insulin concentration over a 3-year period (P = 0.002). Further, baseline ferritin and transferrin were independently associated with the onset of hyperglycemia over a 3-year period in the whole population (P < 0.001 for both) and in each sex.

CONCLUSIONS—Although negatively correlated, both transferrin and ferritin were positively associated with the onset of abnormalities in glucose metabolism in a prospective study. These results further support the hypothesis of a causative role of iron metabolism in the onset of insulin resistance and type 2 diabetes.
C-Peptide Does Not Affect Ocular Blood Flow in Patients With Type 1 Diabetes
Authors: Polska Elzbieta , Kolodjaschna Julia , Berisha Fatmire , Malec Maria M. , Simader Christian , Bayerle-Eder Michaela , Roden Michael , Schmetterer Leopold
Published: August 2006

OBJECTIVE—The aim of the present study was to investigate the effect of intravenous C-peptide infusion on ocular blood flow in patients with type 1 diabetes under euglycemic conditions.

RESEARCH DESIGN AND METHODS—The study was performed in a randomized, placebo-controlled, double-masked, two-way, crossover design in 10 type 1 diabetic patients. C-peptide was intravenously administered at two different dosages (dosage 1: 25 pmol · kg−1 · min−1 bolus followed by 5 pmol · kg−1 · min−1 continuous infusion; dosage 2: six times higher than dosage 1), each for 60 min. Physiologic saline solution was used as a control for C-peptide on a different study day. On both study days, euglycemic clamps were performed. To assess retinal blood flow, laser Doppler velocimetry (blood flow velocities) and retinal vessel analyzer (vessels diameters) measurements were performed. Laser interferometric measurements of fundus pulsation were used to assess pulsatile choroidal blood flow. Blood velocities in the ophthalmic artery were measured using color Doppler imaging.

RESULTS—Eight patients (two female and six male) completed the study according to the protocol and without adverse events. One patient developed an anaphylactic reaction to C-peptide, which resolved without sequelae. The following results originate from the remaining eight subjects. Systemic hemodynamic parameters remained stable during both study days. Infusion of C-peptide did not affect any ocular hemodynamic parameter.

CONCLUSIONS—The data of the present study indicate that exogenous C-peptide exerts no effect on ocular hemodynamic parameters in type 1 diabetic patients under euglycemic conditions. The maximum detectable change in these parameters was <25%.