bluuebunny/crossref_metadata_2025 huggingface dataset:
Trace Element Concentration in Amorphous Clays of Volcanic Ash Soils in Oregon
Authors: Borchardt G. A. , Harward M. E. , Knox E. G.
Published: August 2006

Clay fractions in soils from a transect of the Mazama ash deposit (6600-yr-old) contained more than 80% amorphous material. Instrumental neutron activation analysis was used to compare the trace element composition of the soil clay with the unweathered volcanic glass. The clay fractions had only 10% as much Na as the volcanic glass. Conversely, the rare earth element concentrations were about three times greater and the transition metal concentrations were up to nine times greater in the clay than in the glass. The < 2μ size fraction therefore contained mostly weathering products rather than fine glass.

The abundances of Cr, Co, Sc, and Fe in the clay fraction decreased with depth. The Sc/Fe ratio was approximately 4 × 10−4 for both clay and the unweathered glass. The relationship between elemental concentration in clay and fine sand size separates from the same soil horizons indicated that the clay exists in association with the larger size particles, probably as coatings.

Dilute nitric acid removed about 80% of the rare earth elements La, Nd, Sm, Eu, Tb, Yb, and Lu from the clay. Deferration was necessary to remove Ce, a rare earth element that forms insoluble oxides upon oxidation to the Ce4+ state. The residue of the KOH dissolution treatment contained 2:1 layer silicates that may be derived from primary biotite.
An Analysis of X-Ray Diffraction Line Profiles of Microcrystalline Muscovites
Authors: Kodama H. , Gatineau L. , Méring J.
Published: August 2006

Previous studies of the line profiles of the basal reflections of microcrystalline muscovites were refined by an adaptation of the method developed by Maire and Méring. In order to evaluate the variation of interlayer spacings, the method required only relative values of Fourier coefficients, without the correction for instrumental broadening, which was the source of one of the most critical problems previously. Instead of Kα radiation, Kβ radiation was used to record line profiles since difficulties associated with the separation of Kα1 and Kα2 radiations could not be overcome satisfactorily.

The data reconfirmed that the line broadening of 00l reflections was due not only to a small particle-size effect, but also to structural disorders involving the variation of the interlayer spacings. For the four specimens investigated here, the mean squares of the variation of interlayer spacings ranged from 0 to 0·0358, the square roots of which were inversely proportional to the total number of interlayer cations. It is considered that the observed distortions were mainly attributed to non-uniform interlayer spaces between silicate layers arising from an irregular distribution of interlayer cations. The data also indicated that the crystallites of all four specimens consisted of a similar number of layers. The method showed promise for the study of the nature and extent of structural disorders in micas or other silicate minerals.
Structures, Compositions, and X-Ray Diffraction Identification of Dioctahedral Chlorites
Authors: Bailey S. W. , Lister Judith S.
Published: August 2006

Al-rich di, trioctahedral chlorite exists as the species cookeite and sudoite. Di,dioctahedral chlorite exists as the species donbassite. Cookeite has essential Li in its structure, sudoite has essential Mg, and donbassite has only small amounts of either element. To date, sudoite has been reported to have only IIb structural units and donbassite to have only Ia structural units. Cookeite is based primarily on Ia structural units, but IIb units are present in specimens from two localities. Most Al-rich chlorite species have regular-stacking “r” or “s” 2-layer stacking sequences, but 1-layer Ia-2 and Ia-6 polytypes also are known. The structural units (Ia or IIb) and the specific stacking sequences can be explained by a combination of local charge balance and minimization of cation-cation repulsion involving the interlayer and tetrahedral cations. X-ray powder diffraction data are adequate to differentiate Al-rich chlorite from trioctahedral chlorite and to identify the type of structural unit present, but single crystal study is necessary to identify the 2-layer and 1-layer sequences with certainty.
Stacking Faults in the Kaolin-Group Minerals: Defect Structures of Kaolinite
Authors: Plançon A. , Giese R. F. , Snyder R. , Drits V. A. , Bookin A. S.
Published: August 2006

Previous studies of the defect structure of kaolinite have examined samples having a restricted level of defects. This study examined nine kaolinite samples having a large diversity of defect contents, as indicated by Hinckley indexes ranging from 1.44 to 0.18. The samples were chosen so as to cover this range in as regular a manner as possible. The types and abundances of the defects were determined by examining the X-ray powder diffraction profiles for the 02,11 and 20,13 bands. The diffraction intensities were measured by counting for a fixed time in steps of 0.01°2θ. Analysis of these diffraction profiles indicated that (1) the major defect is the existence of a translation between adjacent layers, which is not the usual (approximately a/3), but is related to that translation by the pseudo-mirror plane coincident with the long diagonal of the unit cell; (2) the existence of a few C layers among the B layer stacking is a minor defect; (3) many of the samples could be accurately modeled only by assuming the existence of two kaolinite phases; (4) the existence of only a few C layers in some samples does not support the idea of a continuous series from kaolinite to dickite through disordered intermediates; and (5) the Hinckley indexes of several samples depend on the relative proportions of the two types of kaolinite in the mixture.

The nine kaolinite samples fall into three groups: those having a low to moderate abundance of defects (Hinckley index > 0.43) are mixtures of two types of kaolinite (one almost free of defects, the other richer in defects); those having low Hinckley indexes (0.43 to 0.18) are single phases with different proportions of defects; and those which contain a single type of kaolinite, unlike the others in the nature of the interlayer translations and the greater abundance of C layers. The agreement between calculated and observed X-ray diffraction profiles is excellent for all specimens, except one sample (from Charentes) for which the fit is acceptable but not perfect.
Convenient Technique for Estimating Smectite Layer Percentage in Randomly Interstratified Illite/Smectite Minerals
Authors: Inoue Atsuyuki , Bouchet Alain , Velde Bruce , Meunier Alain
Published: August 2006

The validity of the saddle/001 method for estimating the percentage of smectite layers in randomly interstratified illite/smectite (I/S) minerals as a routine laboratory technique has been examined with respect to the effects of the crystallite size distribution (N = number of layers) of I/S and the degree of preferred orientation of crystallites in the prepared specimen. X-ray powder diffraction experiments of I/S clays indicated that the crystallite size distribution was 3 < N < 12; these values were supported satisfactorily by the variation of the d(002) value of the samples. An analysis of the Lorentz factor concerning the degree of preferred orientation of crystallites indicated that a calibration curve calculated using the random powder Lorentz factor and the above crystallite size distribution fit the data better than an assumption of perfect orientation. Consequently, if a calibration curve of the saddle/001 ratio is used to estimate the percentage of smectite layers in I/S, an error of 10–15% should be expected from the variable crystallite size distribution of actual samples, in which I/S dominates over other phyllosilicate phases that give reflection between 10–14 Å. This method is useful, however, in estimating the relative percentage of smectite layers in randomly interstratified I/S for samples examined under identical experimental conditions.
Properties of Organo-Mineral Complexes Formed by Different Addition Sequences of Hydroxy-Al, Montmorillonite, and Tannic Acid
Authors: Buondonno A. , Felleca D. , Violante A.
Published: August 2006

A study was carried out on the influence of the sequence of addition of montmorillonite, hydroxy-Al ions, and tannic acid ([Al] = 0.015 M; 6 mmole Al/g of clay; tannic acid/Al molar ratio = 0.1) on the nature of organo-clay complexes formed at pH 4.5. A negligible amount of tannate was held on the clay surfaces in the absence of Al, whereas in the presence of Al, hydroxy-Al-tannate species were easily adsorbed on clay surfaces. Their distribution on the external surface and in the interlayer space of montmorillonite, however, was a consequence of how the components reacted with each other. The complexes showed broad X-ray powder diffraction peaks at 15.6 to 19.2 Å at room temperature. They also showed different behavior to preheating, ethylene glycol solvation, and chemical treatments. Whereas tannic acid showed two prominent exothermic peaks at 390° and 510°C, all hydroxy-Al-tannate-mont-morillonite complexes showed a broad exotherm at about 400°–450°C. Some complexes showed, in addition, a small inflection between 350° and 420°C. The complexes also showed distinct differences in cation-exchange capacity, carbon content, extractable Al, titratable acidity, and mode of aggregation after drying.
Mechanism of Acid Activation of Magnesic Palygorskite
Authors: Gonzalez F. , Pesquera C. , Benito I. , Mendioroz S. , Pajares J. A.
Published: August 2006

This paper compares the texture of palygorskite after acid leaching with that of the product after extraction silica is removed. These effects were evaluated on the basis of nitrogen adsorption-desorption and mercury penetration porosimetry. Acid leaching at reflux temperature with 2 N HCl resulted in an increase in surface area from 138 to 399 m2/g, due to a partial (~50%) dissolution of the octahedral sheet and the creation of microporosity. This microporosity disappeared if the silica generated by the leaching was removed. The surface area also decreased from 399 to 214 m2/g, and the pore volume decreased from 0.538 to 0.507 cm3/g. The microporosity must therefore have been due to texture development in the generated silica.
Influence of Exchangeable Cations on the Surface Free Energy of Kaolinite as Determined from Contact Angles
Authors: Jańczuk Bronisław , Chibowski Emil , Hajnos Mieczysław , Białopiotrowicz Tomasz , Stawiński Janusz
Published: August 2006

The influence of adsorbed H+, Na+, K+, Ca2+, Mg2+, Ba2+, and Al3+ ions on the wettability of a kaolinite surface was determined from contact angles, which were measured in kaolinite-water drop-air (saturated water vapor) and kaolinite-diiodomethane drop-air systems. From the results and using a modified Young equation, the dispersion and nondispersion components of the free energy of the kaolinite hydrated surface were determined. The dispersion component of all the tested samples was between 32.8 and 38.9 mJ/m2, but the nondispersion component changed almost linearly from 53 to 95.9 mJ/m2 with the change of the entropy of hydration of the adsorbed ions, except for K+ and Ba2+. The latter ions were exceptions, probably due to their large ionic radii.
Influence of Structural and Adsorbed Si on the Transformation of Synthetic Ferrihydrite
Authors: Vempati R. K. , Loeppert R. H.
Published: August 2006

The transformation of ferrihydrite to goethite and/or hematite, as influenced by the presence of co-precipitated Si, was investigated by infrared spectroscopy (IR), X-ray powder diffraction (XRD), and transmission electron microscopy (TEM). Ferrihydrite samples having Si/Fe molar ratios ranging from 0 to 1 were synthesized by reacting Fe2(SO4)3 with NaOH to an equilibrium pH of 8.2 in the presence of Na2SiO3. The XRD pattern of the Si-free sample contained five distinct but weak peaks, whereas the patterns of ferrihydrite samples containing Si had only two broad bands. With an increase of the Si/Fe molar ratio from 0.10 to 1.0, the 2.54-Å XRD peak shifted to 2.97 Å, and broad IR bands were observed at 990 cm−1 (Si-O stretching region) and 450 cm−1 (silicate bending region). The intensities of both IR bands increased with increasing Si/Fe molar ratio.

Ferrihydrite samples were incubated at room temperature in sodium acetate/acetic acid buffer solutions at pH 3, 5, 7, and 10 and in CaCO3 suspension at pH 8.3 for 10 months. Additional samples were incubated at pH 12.5 at 24°, 40°, 60°, and 91°C for 36 hr. Room-temperature incubation of ferrihydrite samples having Si/Fe molar ratios ≥0.1 at pH 3 for one week resulted in the dissolution of Fe and the precipitation of silica gel. Ferrihydrite samples having Si/Fe molar ratios ≤0.05 transformed to poorly crystalline goethite during room-temperature incubation at pH 5. The rate of transformation and the degree of crystallinity of the product were inversely related to Si/Fe molar ratio, and, with heat treatment, were also dependent on incubation temperature. Siliceous ferrihydrite samples having Si/Fe molar ratios ≥0.10 did not transform to phases having greater crystallinity during incubation at either room temperature in buffered solutions at pH ≥7 for as long as 10 months or at pH 12.5 at 91°C for 36 hr. The XRD peak at 2.97 Å did not shift significantly during incubation procedures, providing evidence that the structure of the high-Si ferrihydrite was not significantly altered.
Transmission Electron Microscopic Study of the Kaolinitization of Muscovite
Authors: Jiang Wei-Teh , Peacor Donald R.
Published: August 2006

Hydrothermally kaolinitized muscovite from the Otago schist of Brighton, New Zealand, has been studied by transmission and analytical electron microscopy (TEM and AEM) to determine the mechanism of alteration and to compare reactant-product relations for di- and trioctahedral micas. The muscovite is a primary metamorphic phase having a phengitic composition. It occurs as well-ordered, two- and three-layer polytypes, in grains as thick as 30 μm. Kaolinite occurs as packets of layers, each about 100–600 Å thick, which alternate with packets of muscovite or smectite-like layers. Most of the kaolinite is highly disordered in stacking sequence, although a one-layer polytype is also present, occurring as relatively thick sequences of layers. Phase boundaries between kaolinite and muscovite are invariably parallel to the 001 lattice fringes with no strain contrast; i.e., no transitions exist along layers. Parallelism of 00l and 11l reflection rows of both kaolinite and muscovite implies a topotaxial intergrowth. A smectitelike phase is also present, occurring as packets of wavy layers, which locally have periodic contrast that may reflect R1 ordering of illite/smectite. This material appears to be a direct, “along-layer” alteration product of muscovite. Electron diffraction data and lattice-fringe images imply that kaolinite alternates with micaceous phase(s) with some regularity; i.e., micaceous layers are separated by approximately equal numbers of kaolinite layers. Similar long-range periodicity occurs in contrast variations within packets of kaolinite layers.

The data collectively suggest that the alteration interface was self-perpetuating and that alteration proceeded rapidly along layers once it initiated in 2:1 layers at crystal edges or strained areas, with no observable component normal to the layers. They also suggest that smectite may have formed as an intermediate phase during the hydrothermal kaolinitization of muscovite. In the previous study of alteration of biotite in the same sample, “along-layer” transition boundaries were commonly observed, and a second, intermediate product phase was not detected, implying a relation between the alteration mechanisms and the chemical differences between reactants and products.
Mercury Adsorption by Sulfurized Fibrous Silicates
Authors: Daza L. , Mendioroz S. , Pajares J. A.
Published: August 2006

To eliminate mercury vapor from gas streams, three major methods are used: condensation, absorption, and adsorption. This work deals with adsorption, using elemental sulfur as an active phase supported on sepiolite and palygorskite fibrous clays. Sulfur loads of 5–30% were deposited by catalytic oxidation of hydrogen sulfide at temperatures of <200°C, the clays acting first as a catalyst of the reaction and then as a carrier of the obtained sulfur. The ability of the sulfurized clay adsorbents to retain mercury was studied at 45°C and 1 mm Hg pressure. The high values found, about 4 g Hg/g S supported on clays, compared with 1.69 g Hg/g S on activated carbon under the same conditions are related to a more appropriate pore size distribution, with more of the pore widths >6 nm for the sulfurized silicates. Also, the allotropic state of the deposited sulfur, where Sπ (octo-catena) is better than Sλ (octo-cycle), may also be a contributing factor.
Compaction and Swelling of Ca-Smectite in Water and in CaCl2 Solutions: Water Activity Measurements and Matrix Resistance to Compaction
Authors: Denis Jérôme H.
Published: August 2006

Direct water-activity measurements were made for calcium-smectite-CaCl2 mixtures. The samples used were prepared by high-pressure filtration and had water contents <0.60% by weight of clay. For deionized water, the water activity (aw) ranged between 1 and 0.4 and was independent of the pressure history of the clay cake. Good agreement was found with the results of an adsorption isotherm. Samples were also prepared in 1,3, and 5 M CaCl2 solutions. The final concentration of chloride present in the cakes was measured: substantial anion exclusion was observed. The water activity of the clay-salt mixtures depended on both the water content and the concentration of CaCl2. The data can be well represented by the expression aw = min(aw0, aw*c × aw*s), where aw0 is the water activity of the brine used to prepare the cake, and aw*c and aw*s are water activities calculated for clay (in absence of salt) and salt (in absence of clay), respectively. The compaction and swelling behavior of a core of the same Ca-smectite was also investigated for pressures (P) between 0.5 and 800 bar. In two compaction-swelling cycles total recovery of the void ratio (e) was observed with, however, large hysteresis in the relationship between e and P. The osmotic pressure developed in the core at equilibrium, evaluated using the water-activity data, was intermediate between the compaction and swelling pressures. Apparently, another force, Pm, linked to irreversible changes in the structure of the matrix was contributing to the resistance to compaction. Pm values agreed with literature results for Ca-smectite suspensions.
Surface Free Energy Components of Clay-Synthetic Humic Acid Complexes from Contact-Angle Measurements
Authors: Jouany Claire
Published: August 2006

The surface free energy components of clay-organic complexes were determined to assess to what extent an organic adsorbate modified the surface properties of the mineral, insofar as the stability of soil aggregates is concerned. Adsorption isotherms for two synthetic, humic acid-like polymers were determined on a Ca-montmorillonite. From contact-angle measurements performed on dry surfaces, the surface free energy properties of the clay-organic complexes were determined using the two-liquid-phases method (water and hydrocarbons). This method allows both the dispersive and nondispersive components of the solid surface free energy, γDS and γPS, to be determined. The results show that a very small amount of polymer (1% by weight) adsorbed on the external surfaces of the montmorillonite decreased markedly the surface free energy components of the clay: γDS decreased from 75 to 28 mJ/m2 for polycondensate catechol (PC) and from 75 to 30 mJ/m2 for polycondensate catechol triglycine (PCT), whereas γPS ranged from 35 to 16 mJ/m2 (PC) and from 35 to 17 mJ/m2 (PCT). Although their chemical compositions were different, both polymers similarly modified γDS and γPS. Increasing the amount of polymer adsorbed (from 1% to 3.5% by weight) affected mostly γPS, which became as low as 5 mJ/m2; meanwhile, γDS decreased from 30 to 23 mJ/m2. Possibly, the molecular orientation of the adsorbate changed in the process of dehydration. Following adsorption of synthetic humic acid-like polymers, dry Ca-montmorillonite complexes displayed γS values < 50 mJ/m2, which were consistent with the solid-water contact angles measured in air.
Diagenetic Structural Transformations in North Sea Jurassic Illite/Smectite
Authors: Lindgreen Holger , Jacobsen Hans , Jakobsen Hans Jørgen
Published: August 2006

The Kimmeridgian-Volgian(-Ryazanian) clay stone is the principal oil source rock in the troughs of the North Sea. Randomly (R0) ordered mixed-layer illite/smectite (I/S) appears to have transformed to R1-(IS) or R3-(ISII) ordered simultaneously with oil generation. The proportion of illite layers in I/S increased to 95% during diagenesis in these claystones. Exceptions are three samples of I/S of probably bentonitic origin; these have apparently changed during diagenesis to R0-ordered I/S containing 40-50% illite layers. Fine fractions of the claystones dominated by I/S were analyzed by 27Al and 29Si magic-angle spinning (MAS)-nuclear magnetic resonance (NMR) spectroscopy, 57Fe Mössbauer spectroscopy, and X-ray powder diffraction (XRD), and for total chemical composition. Si/Al ratios determined from MAS-NMR agree closely with those calculated from total chemical analysis; however, tetrahedral and octahedral Al occupancies were most accurately determined by NMR. An increase in the percentage of illite layers and in the ordering of the I/S was accompanied by fixation of K+ and NH4+ in the I/S, by tetrahedral Al-for-Si substitution, and by octahedral Al-for-(Mg + Fe) substitution, resulting both in an increase of charge in the 2:1 layers and in a migration of charge from octahedral to tetrahedral sheets. The I/S of probably bentonitic origin had a larger tetrahedral and a smaller octahedral charge than expected from its content of illite layers. MAS-NMR showed a significantly higher content of tetrahedral Al (most likely in smectitic sites) than expected from the percentage of illite layers calculated from XRD. Correspondingly, XRD of K+-saturated and glycolated specimens showed that several smectite layers possessed a significant charge. A constant b-dimension of the I/S and the presence of a significant charge in the smectite layers suggest that a transformation of smectite to illite layers in the I/S by tetrahedral Al-for-Si substitution followed by interlayer cation fixation and interlayer contraction is the most probable genesis for the I/S investigated.
Genesis and Morphology of Iron Sulfides in Gray Kaolins
Authors: White G. Norman , Dixon J. B. , Weaver R. M. , Kunkle A. C.
Published: August 2006

Many of the presently oxidized Georgia kaolins probably existed originally in the reduced (gray) state. For that reason, the distribution of iron sulfides in presently gray kaolins may elucidate features observed in oxidized kaolins. An understanding of the nature of gray kaolins may also aid in the development of processing strategies for the exploitation of these abundant resources. The size, morphology, and degree of crystallite bonding of iron sulfides (pyrite and marcasite) in three gray kaolin cores from the Macon, Georgia kaolin district were examined by X-ray powder diffraction, X-ray fluorescence, scanning electron microscopy, and other physical and chemical methods. Pyrite and marcasite were identified as dominantly gravel- and sand-size equant crystals and crystal aggregates, rather than as framboids. Pyrite crystals commonly showed rough octahedral faces, which extended over minor cube faces. Locally, spiral growth dislocations were also observed. Marcasite was found in radiating, prismatic, and tabular crystals. In general, the marcasite crystal aggregates were much more fragile than those of pyrite. The dominance of octahedral crystal shapes and textures of the pyrite suggest inorganic precipitation from solutions supersaturated with respect to octahedral crystal faces.
X-Ray Powder Diffraction Studies on the Rehydration Properties of Beidellite
Authors: Kawano Motoharu , Tomita Katsutoshi
Published: August 2006

The rehydration properties of Ca-, Mg-, Na-, and K-saturated homoionic beidellites after heating at various temperatures were compared with those of montmorillonites. The behavior of interlayer Na+ during dehydration and rehydration was also investigated by means of one-dimensional Fourier analysis. The K- and Mg-saturated specimens exhibited fast and slow rehydration rates, respectively, during exposure to air of 50% RH after heating at 800°C. These homoionic specimens showed strong rehydration properties on saturation with deionized water after heating <900°C for 1 hr. On the basis of Fourier analysis, the interlayer cations appeared to have migrated into the hexagonal holes of SiO4 network on thermal dehydration, and the migrated cations returned to the interlayer space on rehydration. This behavior of the interlayer cations appears to have been strongly dependent on value of the octahedral negative charge and on the sizes of interlayer cations. The small octahedral negative charge of beidellite produced a weaker attractive electrostatic force between the octahedral sheets and the migrated interlayer cations. Therefore, the migrated interlayer cations in beidellite were easily extracted from the hexagonal holes, and rehydration was rapid. The small cation migrated easily into hexagonal holes and was fixed to the holes. On the contrary, large cations were probably difficult to fix and were easily extracted from the hexagonal holes. Consequently, the rehydration rate of K-saturated beidellite was fast, and that of Mg-saturated beidellite was slow.
Weathering of Granitic Muscovite to Kaolinite and Halloysite and of Plagioclase-Derived Kaolinite to Halloysite
Authors: Robertson Ian D. M. , Eggleton Richard A.
Published: August 2006

Weathered perthite and mixed muscovite-kaolinite from a kaolinitic granite at Trial Hill in east Queensland and kaolinized sericitic alteration from a granite from the Ardlethan Tin Mine of New South Wales were examined by optical, scanning electron (SEM), and transmission electron microscopy (TEM) to determine the alteration process of muscovite to kaolinite and kaolinite to halloysite (7Å). Muscovite was found intimately interleaved with kaolinite in a variety of proportions on a sub-micrometer scale. The contact was generally parallel to the (001) layers of both minerals, and the thickness of the contact layer alternated between 10 and 7 Å over short distances. Where the kaolinite to muscovite contact was at an acute angle to the muscovite layers, a small angle existed between the layering of the two phases, consistent with a topotactic alteration of muscovite to kaolinite. One tetrahedral sheet in the muscovite appeared to have been removed over 50–100 Å, converting a 10-Å layer to a 7-Å layer. The mica near the contact with kaolinite was easily damaged in the electron beam and showed Al loss during analytical transmission electron microscopy; thus, H3O+ probably substituted for K+ in this transitional phase.

An SEM examination of completely weathered plagioclase showed kaolinite plates having attached, parallel, polygonal rods of halloysite (7Å), which had planar sides and a central void, partly fused with the surfaces of the kaolinite crystals. TEM study showed that the kaolinite altered to halloysite, and that, where the kaolinite was partly altered to halloysite, a series of sharp kinks were present in the kaolinite plate in which alteration had occurred. These kinks were interspersed with linear kaolinite relics, 0.1–0.2 μm long, which appear to have provided local rigidity to the clay packet. Apparently, the altered clay first curled into loosely wound spirals, which ranged in cross-section from triangles to irregular octagons, with pentagons and hexagons being most common. The tendency to pentagons and hexagons compares well with a statistical study of the angles, which were most commonly grouped around 120°. As alteration of the kaolinite relics progressed, the linear parts of the spiral lost their rigidity and became circular or oval shaped. The long axis of the halloysite spirals was parallel to the X axis of the kaolinite. Halloysite spirals formed most readily if they had space to curl; if space was not available, the halloysite formed sheaves. Rare, thin layers of muscovite were present projecting through kaolinite into halloysite. Where muscovite relics reached open spaces, the 10-Å structure expanded to 14 Å.
Transformation of Akaganéite Into Goethite and Hematite in the Presence of Mn
Authors: Cornell R. M. , Giovanoli R.
Published: August 2006

The interaction of Mn and akaganéite in neutral to alkaline media has been investigated using X-ray powder diffraction and transmission electron microscopy. Akaganéite transformed into goethite and/or hematite, whereas Mn precipitated as hausmannite and birnessite at pH > 12 and as manganite at pH 7.5–8.5. Mn influenced the kinetics of the transformation of akaganéite: the rate-determining step, i.e., the dissolution of akaganéite, was retarded by adsorbed Mn species. Hematite formation was not suppressed. By catalyzing the air oxidation of adsorbed Mn(II), akaganéite promoted the formation of birnessite. Akaganéite did not retard recrystallization of the Mn phases. The incorporation of Mn in the structure of goethite formed in this system was negligible, and jacobsite (MnFe2O4) did not form. The formation of mixed Mn-Fe phases appeared to require a ratio of Mn2+: Fetotal > 0.02; this ratio was not achieved due to the oxidation of Mn2+ at the akaganéite surface.
Formation of Organic Derivatives of Boehmite by the Reaction of Gibbsite with Glycols and Aminoalcohols
Authors: Inoue Masashi , Tanino Hirokazu , Kondo Yasuhiko , Inui Tomoyuki
Published: August 2006

The reaction of gibbsite in various organic solvents at 250°–300°C under spontaneous vapor pressure of the solvents was examined. Glycols and aminoalcohols afforded the organic derivatives of boehmite in which one of the oxygen atoms of the glycol molecule or the alcoholic oxygen atom of aminoalcohol was incorporated into the boehmite layers. By increasing the molecular size of the solvent, the yield of the boehmite derivative decreased, and, at the same time, the basal spacing of the boehmite derivative increased. The product had a honeycomb texture on the surface of the particle, which suggests a dissolution-recrystallization mechanism for the formation of the boehmite derivatives. A hydroxyl group and a functional group, such as hydroxyl, methoxyl, or amino group having the ability to donate its lone pair electrons, were apparently necessary for the organic solvent molecules to form the boehmite derivative by this mechanism.
Interactions of Citric Acid and Synthetic Hydroxy-Aluminum Montmorillonite
Authors: Cambier P. , Sposito Garrison
Published: August 2006

Hydroxy-Al-montmorillonite was prepared by mixing Na-Wyoming montmorillonite with Al(OH)2.5 polycations and aging the mixture for 10 days. The reactions of this complex with citric acid at millimolar concentrations were investigated at different pHs for a 4-hr reaction time. The citrate sorption data, X-ray powder diffraction patterns of the montmorillonite adsorbent, and solubility products for Al(OH)3, estimated after computer speciation of the aqueous solution phase, suggested two reaction mechanisms, depending on pH. At 4 < pH < 5.5, the complex was stable, and only external hydroxy-Al polycations could react with citrate, yielding a sorption envelope characteristic of an acid having a low pKa. At higher pH, and particularly at pH > 7, the interlayer Al-polymers became accessible to the ligand and desorbed quickly from the montmorillonite basal planes to form a new, external, X-ray-amorphous solid phase with citrate. This reaction produced a large second peak in the sorption envelopes near pH 8, which was controlled by the increasingly negative surface charge at high pH and by the initial concentration of citric acid. This ligand accelerated, i.e., favored kinetically, the dissociation of adsorbed hydroxy-Al polymers from montmorillonite at pH > 7.
Preparation and Properties of Large-Pore La-Al-Pillared Montmorillonite
Authors: Sterte Johan
Published: August 2006

Large-pore La-Al-pillared montmorillonite was prepared by reacting montmorillonite with hydrothermally treated mixtures of aluminum chlorohydrate and lanthanum chloride. The large-pore La-Al-pillared montmorillonite is characterized by basal spacings of about 26 Å, surface areas of 300–500 mVg, and pore volumes in the range 0.2–0.3 cm2/g. Large-pore pillared montmorillonite products were obtained from solutions refluxed for >72 hr or treated in autoclaves at 120°–160°C for 12–96 hr. The most favorable pillaring solution for the production of large-pore La-Al-pillared montmorillonite had an OH/Al ratio of 2.5, a La:Al ratio of 1:5, and was 2.5 M with respect to Al. The elemental composition of large pore La-Al-pillared montmorillonite is similar to that of a conventional Al-pillared montmorillonite that has a basal spacing of about 19 Å. The 26-Å spacing is believed to be associated with the formation of large polymeric La-bearing Al-cations upon hydrothermal treatment of the solutions.
Neural Representation of Task Difficulty and Decision Making during Perceptual Categorization: A Timing Diagram
Authors: Philiastides Marios G. , Ratcliff Roger , Sajda Paul
Published: August 2006

When does the brain know that a decision is difficult to make? How does decision difficulty affect the allocation of neural resources and timing of constituent cortical processing? Here, we use single-trial analysis of electroencephalography (EEG) to identify neural correlates of decision difficulty and relate these to neural correlates of decision accuracy. Using a cued paradigm, we show that we can identify a component in the EEG that reflects the inherent task difficulty and not simply a correlation with the stimulus. We find that this decision difficulty component arises ≈220 ms after stimulus presentation, between two EEG components that are predictive of decision accuracy [an “early” (170 ms) and a “late” (≈300 ms) component]. We use these results to develop a timing diagram for perceptual decision making and relate the component activities to parameters of a diffusion model for decision making.
Interactions between Speed and Contrast Tuning in the Middle Temporal Area: Implications for the Neural Code for Speed
Authors: Krekelberg Bart , van Wezel Richard J. A. , Albright Thomas D.
Published: August 2006

A car driving through the fog appears to move more slowly than one driving on a clear and sunny day. In the laboratory, this observation has been confirmed as a pronounced reduction of perceived speed caused by a reduction in contrast.

We measured the influence of contrast on cells in the middle temporal area (MT) of the macaque, which has been hypothesized to underlie the perception of speed. The influence of contrast on the responsiveness and speed tuning of these cells was pervasive and highly regular. As expected, most cells responded less at low contrast. More importantly, the preferred speed of most cells shifted to lower speeds at lower contrasts. Moreover, approximately one-third of cells surprisingly responded more strongly to slow low-contrast stimuli than to slow high-contrast stimuli.

Current models of speed perception suggest that each MT cell votes for its preferred speed, with a vote determined by its firing rate. We tested a number of these labeled-line models by entering the neural responses we recorded from MT and comparing the predictions of the models with the perceptual reports of human subjects and monkeys. Contrary to the perceptual reports, the labeled-line models predicted that perceived speed should increase when contrast is decreased. We therefore conclude that perceived speed is not based on a labeled-line interpretation of MT cells.
Prolongation of Evoked and Spontaneous Synaptic Currents at the Neuromuscular Junction after Activity Blockade Is Caused by the Upregulation of Fetal Acetylcholine Receptors
Authors: Wang Xueyong , Engisch Kathrin L. , Teichert Russell W. , Olivera Baldomero M. , Pinter Martin J. , Rich Mark M.
Published: August 2006

It has been shown previously in a number of systems that after an extended block of activity, synaptic strength is increased. We found that an extended block of synaptic activity at the mouse neuromuscular junction, using a tetrodotoxin cuffin vivo, increased synaptic strength by prolonging the evoked endplate current (EPC) decay. Prolongation of EPC decay was accompanied by only modest prolongation of spontaneous miniature EPC (MEPC) decay. Prolongation of EPC decay was reversed when quantal content was lowered by reducing extracellular calcium. These findings suggested that the cause of EPC prolongation was presynaptic in origin. However, when we acutely inhibited fetal-type acetylcholine receptors (AChRs) using a novel peptide toxin (αA-conotoxin OIVA[K15N]), prolongation of both EPC and MEPC decay were reversed. We also blocked synaptic activity in a mutant strain of mice in which persistent muscle activity prevents upregulation of fetal-type AChRs. In these mice, there was no prolongation of EPC decay. We conclude that upregulation of fetal-type AChRs after blocking synaptic activity causes modest prolongation of MEPC decay that is accompanied by much greater prolongation of EPC decay. This might occur if acetylcholine escapes from endplates and binds to extrajunctional fetal-type AChRs only during large, evoked EPCs. Our study is the first to demonstrate a functional role for upregulation of extrajunctional AChRs.
Comparing and Combining Effort and Catch Estimates from Aerial–Access Designs as Applied to a Large-Scale Angler Survey in the Delaware River
Authors: Vølstad Jon H. , Pollock Kenneth H. , Richkus William A.
Published: August 2006

We used probability-based aerial−access surveys to estimate effort, catch, and harvest of American shad Alosa sapidissima and striped bass Morone saxatilis by recreational anglers in the Delaware River and upper estuary in 2002. Sampling of anglers at access points and flights over the river were conducted weekly from mid-March through October. Daily flight times were randomly selected; probabilities were proportional to the observed distribution of daily angler effort in a prior aerial−access survey (random count). Additional experimental flights were scheduled to occur at the time of day with expected peak effort (maximum count). Effort estimates derived from these maximum counts were more precise than estimates derived from the random flights, but the maximum-count observations caused bias except when the daily count expansions were based on effort distributions from the concurrent access survey. The aerial and access surveys produced similar estimates of boat angler effort and little evidence of bias, but shore anglers were undercounted in the aerial survey. We maximized the precision and minimized bias in total effort estimates by combining the estimates of boat angler effort and shore angler access. An estimated sevenfold increase in the access survey sampling effort (at nearly five times the cost) would be required to achieve the same precision in the total effort estimate produced by the aerial–access survey. Effective stratification and the use of efficient model-based estimators helped us to achieve the target precision of 20% in relative standard error (RSE) for estimated recreational catch of American shad (mean = 26,885 fish; RSE = 16%) and striped bass (mean = 47,671 fish; RSE = 15%). A single access survey during the American shad run would have required a 10-fold increase in sampling effort to achieve the same precision in estimated catch at six times the cost of the complemented surveys.
Development of a Rapid Bioassessment Protocol for Sampling Fish in Large Prairie Rivers
Authors: Utrup Nicholas J. , Fisher William L.
Published: August 2006

We used seining and hoop netting to collect fish at 15 sites in five large prairie rivers in Oklahoma to (1) determine the amount of effort needed to detect the maximum number of species at a sample site and (2) examine the selectivity of fish species detected by the two gear types. Analysis of the similarities of the fish collected in six different habitat types identified two distinct habitat types based on fish species composition: shallow–backwater (SBW) habitat (depth ≤ 0.75 m) and deep–nonwadeable (DNW) habitat (depth > 0.75 m). We estimated that between 6 and 10 (mean = 8) SBW habitats and between 1 and 6 (mean = 4) DNW habitats at each sample site were needed to obtain maximum species richness during a sampling event. The sampling distance needed to encounter the minimum number of habitats ranged from 400 to 1,600 m and averaged 887 m. Gear evaluation showed that seining captured more species per unit effort than hoop netting (3.6 and 1.4, respectively); however, hoop netting captured significantly larger fish (527 mm; P < 0.001) than seining (42 mm). Based on these collections, we present recommendations for sampling fish assemblages in large prairie rivers in the southern Great Plains to aid in the rapid bioassessment and monitoring of fish assemblages in large prairie rivers.
Performance of Passive Integrated Transponder Tags and Radio Tags in Determining Dam Passage Behavior of Adult Chinook Salmon and Steelhead
Authors: Burke Brian J. , Jepson Michael A.
Published: August 2006

Passage of adult Pacific salmon Oncorhynchus spp. and steelhead O. mykiss at dams in the Columbia River basin has historically been determined by visual fish counts and radiotelemetry. Increasingly, however, passive integrated transponder (PIT) tags are being used for adult salmonid research and monitoring. Although both radiotelemetry and PIT tag technology provide accurate and cost-effective data under certain circumstances, neither alone meets all needs, and managers need to understand the strengths, weaknesses, and biases of each method. To evaluate the two tagging methods, we tagged over 3,200 adult Chinook salmon O. tshawytscha and steelhead during 2002 and 2003 with both a radio transmitter and a PIT tag as the fish migrated upstream past Bonneville Dam. We compared their performance in measuring upstream passage and fallback (i.e., downstream passage) behavior at each of four main-stem hydropower dams. Counts of fish passage at dams based on data from double-tagged fish were similar between methods (largest difference was 5.1%), but the two methods produced less consistent results for fallback behavior. Visual count escapement estimates based on PIT tags were 1% higher on average than those based on radio tags, suggesting there would be little impact on the management of salmonid populations with a switch from radiotelemetry to PIT tag systems as the primary data source. We also analyzed a broader group of PIT-tagged (but not radio-tagged) fish to simulate the analysis one could expect from PIT tag data without radiotelemetry validation. When compared with PIT tag data from double-tagged fish, data from the PIT tag-only fish showed slight differences in the timing of peak passage. These differences were due, at least in part, to the fact that the fish in each group comprised differing proportions of fish from multiple populations, highlighting the importance of having representative stocks of fish PIT-tagged as juveniles.
The Value of Care Algorithms
Authors: Myers Timothy
Published: August 2006

The use of protocols or care algorithms in medical facilities has increased in the managed care environment. The definition and application of care algorithms, with a particular focus on the treatment of acute bronchospasm, are explored in this review. The benefits and goals of using protocols, especially in the treatment of asthma, to standardize patient care based on clinical guidelines and evidence‐based medicine are explained. Ideally, evidence‐based protocols should translate research findings into best medical practices that would serve to better educate patients and their medical providers who are administering these protocols. Protocols should include evaluation components that can monitor, through some mechanism of quality assurance, the success and failure of the instrument so that modifications can be made as necessary. The development and design of an asthma care algorithm can be accomplished by using a four‐phase approach: phase 1, identifying demographics, outcomes, and measurement tools; phase 2, reviewing, negotiating, and standardizing best practice; phase 3, testing and implementing the instrument and collecting data; and phase 4, analyzing the data and identifying areas of improvement and future research. The experiences of one medical institution that implemented an asthma care algorithm in the treatment of pediatric asthma are described. Their care algorithms served as tools for decision makers to provide optimal asthma treatment in children. In addition, the studies that used the asthma care algorithm to determine the efficacy and safety of ipratropium bromide and levalbuterol in children with asthma are described.
The Role of Pharmacists in the Evolution of Health Care: An Open Forum Discussion
Authors: Kelly H. William
Published: August 2006

The pharmacy profession should be actively involved in the development of guidelines and protocols for various disease states. Good research to demonstrate that interventions by pharmacists result in good clinical outcomes and money saved is scarce. Pharmacy is in the early throes of change as a result of growth within the profession. In the future, pharmacists will be more involved in clinical evaluations and less with drug dispensing duties because of advances in automation. The new Medicare Part D program is a real opportunity for pharmacists to be actively engaged in patient education and treatment monitoring.
Ethylene effect on kochia (Kochia scoparia) and emission following dicamba application
Authors: Howatt Kirk A. , Westra Philip , Nissen Scott J.
Published: August 2006

The role of ethylene in kochia injury following the application of dicamba and other auxinic herbicides is not known. Experiments were conducted to evaluate kochia response to ethylene generated within plant tissue and to quantify ethylene emission from kochia following dicamba application to determine if ethylene production could be used to differentiate between dicamba-susceptible (S) and dicamba-resistant (R) kochia accessions. Dicamba at 0.28 kg ha−1and fluroxypyr at 0.28 kg ha−1caused severe stem and petiole twisting within 6 h of application, with S kochia exhibiting a greater level of epinasty than R kochia and fluroxypyr causing more epinasty than dicamba. Fluroxypyr provided similar control of S and R kochia, but dicamba provided less control of R kochia than S kochia. Ethylene evolution in S kochia from ethephon at 1.1 kg ha−1and dicamba at 0.28 kg ha−1was similar, approximately 70 ng (g fresh weight)−1h−1. Elevated ethylene concentration from as much as 2 kg ha−1ethephon did not produce epinastic symptoms or other plant response in S or R kochia. Ethylene evolution following dicamba application increased with time up to 48 h after application and with increasing dicamba rate up to 0.56 kg ha−1, which were the end points of the research. Ethylene evolution from the S accession was 2.5 times that of the R accession averaged across dicamba rates and harvest times. The greatest difference in ethylene evolution between S and R accessions occurred 24 h after treatment at 0.14 kg ha−1dicamba, with S kochia producing ethylene at 470%, compared with R kochia.