bluuebunny/crossref_metadata_2025 huggingface dataset:
Flexible Conceptual Projection of Time Onto Spatial Frames of Reference
Authors: Torralbo Ana , Santiago Julio , Lupiáñez Juan
Published: September 2006

Flexibility in conceptual projection constitutes one of the most challenging issues in the embodiment and conceptual metaphor literatures. We sketch a theoretical proposal that places the burden of the explanation on attentional dynamics in interaction with mental models in working memory that are constrained to be maximally coherent. A test of this theory is provided in the context of the conceptual projection of time onto the domain of space. Participants categorized words presented at different spatial locations (back–front, left–right) as referring to the past or to the future. Responses were faster when the irrelevant word location was congruent with the back–past, front–future metaphoric mapping. Moreover, when a new highly task‐relevant spatial frame of reference was introduced, it changed the projection of past and future onto space in a way that was congruent with the new frame (past was now projected to left space and future to right space), as predicted by the theory. This study shows that there is substantial flexibility in conceptual projection and opens a venue to study metaphoric variation across tasks, individuals, and cultures as the result of attentional dynamics.
An Embodied Model for Sensorimotor Grounding and Grounding Transfer: Experiments With Epigenetic Robots
Authors: Cangelosi Angelo , Riga Thomas
Published: September 2006

The grounding of symbols in computational models of linguistic abilities is one of the fundamental properties of psychologically plausible cognitive models. In this article, we present an embodied model for the grounding of language in action based on epigenetic robots. Epigenetic robotics is one of the new cognitive modeling approaches to modeling autonomous mental development. The robot model is based on an integrative vision of language in which linguistic abilities are strictly dependent on and grounded in other behaviors and skills. It uses simulated robots that learn through imitation the names of basic actions. Robots also learn higher order action concepts through the process of grounding transfer. The simulation demonstrates how new, higher order behavioral abilities can be autonomously built on previously grounded basic action categories following linguistic interaction with human users.
Metacognitive Control and Optimal Learning
Authors: Son Lisa K. , Sethi Rajiv
Published: September 2006

The notion of optimality is often invoked informally in the literature on metacognitive control. We provide a precise formulation of the optimization problem and show that optimal time allocation strategies depend critically on certain characteristics of the learning environment, such as the extent of time pressure, and the nature of the uptake function. When the learning curve is concave, optimality requires that items at lower levels of initial competence be allocated greater time. On the other hand, with logistic learning curves, optimal allocations vary with time availability in complex and surprising ways. Hence there are conditions under which optimal strategies will be relatively easy to uncover, and others in which suboptimal time allocation might be expected. The model can therefore be used to address the question of whether and when learners should be able to exercise good metacognitive control in practice.
The Interpretation of Classically Quantified Sentences: A Set‐Theoretic Approach
Authors: Politzer Guy , Van der Henst Jean‐Baptiste , Delle Luche Claire , Noveck Ira A.
Published: September 2006

We present a set‐theoretic model of the mental representation of classically quantified sentences (All P are Q, Some P are Q, Some P are not Q, and No P are Q). We take inclusion, exclusion, and their negations to be primitive concepts. We show that although these sentences are known to have a diagrammatic expression (in the form of the Gergonne circles) that constitutes a semantic representation, these concepts can also be expressed syntactically in the form of algebraic formulas. We hypothesized that the quantified sentences have an abstract underlying representation common to the formulas and their associated sets of diagrams (models). We derived 9 predictions (3 semantic, 2 pragmatic, and 4 mixed) regarding people's assessment of how well each of the 5 diagrams expresses the meaning of each of the quantified sentences. We report the results from 3 experiments using Gergonne's (1817) circles or an adaptation of Leibniz (1903/1988) lines as external representations and show them to support the predictions.
Arteries define the position of the thyroid gland during its developmental relocalisation
Authors: Alt Burkhard , Elsalini Osama A. , Schrumpf Pamela , Haufs Nele , Lawson Nathan D. , Schwabe Georg C. , Mundlos Stefan , Grüters Annette , Krude Heiko , Rohr Klaus B.
Published: September 2006

During vertebrate development, the thyroid gland undergoes a unique relocalisation from its site of induction to a distant species-specific position in the cervical mesenchyme. We have analysed thyroid morphogenesis in wild-type and mutant zebrafish and mice, and find that localisation of growing thyroid tissue along the anteroposterior axis in zebrafish is linked to the development of the ventral aorta. In grafting experiments, ectopic vascular cells influence the localisation of thyroid tissue cell non-autonomously,showing that vessels provide guidance cues in zebrafish thyroid morphogenesis. In mouse thyroid development, the midline primordium bifurcates and two lobes relocalise cranially along the bilateral pair of carotid arteries. In hedgehog-deficient mice, thyroid tissue always develops along the ectopically and asymmetrically positioned carotid arteries, suggesting that, in mice (as in zebrafish), co-developing major arteries define the position of the thyroid. The similarity between zebrafish and mouse mutant phenotypes further indicates that thyroid relocalisation involves two morphogenetic phases, and that variation in the second phase accounts for species-specific differences in thyroid morphology. Moreover, the involvement of vessels in thyroid relocalisation sheds new light on the interpretation of congenital thyroid defects in humans.
Megane/Heslike is required for normal GABAergic differentiation in the mouse superior colliculus
Authors: Guimera Jordi , Weisenhorn Daniela Vogt , Wurst Wolfgang
Published: September 2006

The mouse Mgn protein (Helt) is structurally related to the neurogenic Drosophila hairy and Enhancer of split [h/E(spl)]proteins, but its unique structural properties distinguish it from other members of the family. Mgn expression shows a spatiotemporal correlation with GABAergic markers in several brain regions. We report here that homozygous Mgn-null mice die between the second and the fifth postnatal week of age, and show a complete depletion of Gad65 and Gad67 expression in the superior colliculus and a reduction in the inferior colliculus. Other brain regions, as well as other neural systems, are not affected. The progenitor GABAergic cells appear to be generated in right numbers but fail to become GABAergic neurons. The phenotype of the mice is consistent with reduced GABAergic activity. Thus, our in vivo study provides evidence that Mgn is the key regulator of GABAergic neurons, controlling their specification in the dorsal midbrain. Another conclusion from our results is that the function of Mgn shows a previously unrecognized role for h/E(spl)-related transcription factors in the dorsal midbrain GABAergic cell differentiation. Vertebrate h/E(spl)-related genes can no longer be regarded solely as a factors that confer generic neurogenic properties, but as key components for the subtype-neuronal identity in the mammalian CNS.
The journey of developing hematopoietic stem cells
Authors: Mikkola Hanna K. A. , Orkin Stuart H.
Published: September 2006

Hematopoietic stem cells (HSCs) develop during embryogenesis in a complex process that involves multiple anatomical sites. Once HSC precursors have been specified from mesoderm, they have to mature into functional HSCs and undergo self-renewing divisions to generate a pool of HSCs. During this process,developing HSCs migrate through various embryonic niches, which provide signals for their establishment and the conservation of their self-renewal ability. These processes have to be recapitulated to generate HSCs from embryonic stem cells. Elucidating the interactions between developing HSCs and their niches should facilitate the generation and expansion of HSCs in vitro to exploit their clinical potential.
Invariant Measures of Closeness to Linear Dependency of Screw Systems
Authors: Kerr D R , Hartley D M
Published: September 2006

This paper describes a new, general analytical method of determining the closeness to linear dependence of any system of lines and screws, giving n invariant scalars for an n-system of screws. The method proposed evaluates the maximum available scalar or Klein product between the unit screw under test and any unit combination of screws reciprocal to all of the set except the test screw. Examples are given of the application of this theory to the behaviour of a partially complete system of kinematic restraint such as those used in manufacturing fixtures of a simple structure and of a serial robotic manipulator.
Workspace Analysis of Stewart-Gough-Type Parallel Manipulators
Authors: Pernkopf F , Husty M L
Published: September 2006

In this paper, for the first time, a complete analysis of the reachable workspace of a spatial Stewart—Gough platform with planar base and platform (SGPP) is presented. The devised workspace algorithms are applied to a commercial 6–6 design. Major importance is given to the visualization of the results of this workspace analysis to provide fast information to the designer on the overall kinematic behaviour of the designed mechanism. Furthermore, it is shown that the reachable workspace also gives the necessary information on how to construct a building enclosing all motion instances of an actual hexapod design.
On the Invariance of Gear Tooth Curvature
Authors: Dooner D B
Published: September 2006

A method is presented for the determination of the principal curvatures along with their principal directions of two gear teeth in direct contact. The procedure used to determine these extreme curvatures and directions is based on the nominal position of contact. Moreover, these extreme curvatures and directions are invariant with tooth type (viz. involute and cycloidal) and manufacturing process. Such curvatures and directions depend on the instantaneous pressure angle, spiral or helix angle, and position of contact. This generalized method is applicable to cylindrical gears (spur and helical), conical gears (straight and spiral), as well as hyperboloidal gears (hypoid and worm). Three examples are included to illustrate the determination of principal curvatures and directions. The first example is a helical gear pair, the second is a spiral bevel gear pair, and the third example is a hypoid gear pair.
Geometric Analysis and Characteristics of a Three-Fixed-Pivoted Multi-Phalanx Robotic Finger
Authors: Luo Z , Dai J S
Published: September 2006

This paper investigates the kinematic structure of robotic fingers, presents a linkage type of multi-phalanx (multi-joint) robotic fingers, and delivers geometric analysis. The new type of robotic fingers is driven by a three-pivoted linkage constituting a mechanism of two degrees of freedom. On the basis of mechanism decomposition with decoupled kinematics, this paper produces the closed-form kinematic equations for modelling the linkage. Decoupling the linkage into a loop linkage and a function generator of a four-bar linkage, the linkage geometric property and workspace are explored and a stiffness map is produced.

The paper further develops the linkage Jacobian matrix and investigates the workspace characteristics.
Numerical Approach to the Kinematic Analysis of Deployable Structures Forming a Closed Loop
Authors: Gan W W , Pellegrino S
Published: September 2006

This article is concerned with spatial linkages forming a closed loop. In one extreme configuration (deployed), these linkages form a frame of polygonal shape, such as a square or a hexagon, and in the other extreme (folded), configuration form a tight bundle. Throughout their motion range, they have mobility one. These linkages have potential applications for next-generation deployable spacecraft structures. The article presents a systematic study of the kinematics of closed-loop structures with these special properties and a numerical scheme for simulating their deployment without making any assumptions about particular symmetry features. The proposed simulation technique is applied to three examples that show different behaviour during deployment.
A mechanistic model of spherical particle entrapment in elliptical contacts
Authors: Nikas G. K.
Published: September 2006

The dynamic interaction of solid, spherical particles with the counterfaces of concentrated, dry or lubricated, conforming or non-conforming, rolling-sliding elliptical contacts is mathematically analysed. Criteria for the entrapment or rejection of particles are postulated on the basis of the resolution of mechanical and fluid forces on a particle for given contact geometry and operating conditions. Three-dimensional maps of the various force components on a particle are presented for a typical application, together with the maps of the zones where a particle would be ‘conditionally’ entrapped, ‘weakly’ rejected, or ‘unconditionally’ rejected, where the previous terms are defined in a comprehensive evaluation system in the model to assess the risk of damage of the contact from the presence of contaminants. This study is concerned with the process of particle entrapment, meaning that a particle must be in contact with both the counterfaces of a concentrated contact, and not entrainment (particle wandering in the lubricant, which has been studied by the author (Nikas, 2002)). To the best of the author's knowledge, this is the first study explicitly dealing with the general case of elliptical contacts. Elliptical contacts cover circular contacts and, taken to the limit, can also simulate line contacts; thus, the model's applicability and validity as a design tool are generalized. In summary, the purpose of the article is to expand previous models developed for simpler geometries and to present an effective computational tool for the simulation of particle entry into elliptical contacts and the resulting risks of contact damage.
Effects of starvation and viscous shear heating in hydrodynamically lubricated rolling/sliding line contacts
Authors: Anandan N , Pandey R. K. , Jagga C. R. , Ghosh M. K.
Published: September 2006

Combined effects of viscous shear heating and starvation in hydrodynamically lubricated high-speed rolling/sliding line contacts have been investigated numerically by using an efficient computational method for the solution of energy equation in which temperature distribution across the film is approximated by Legendre polynomial. Effects of starvation on minimum film thickness, traction coefficient, and mid-film temperature rise are computed for lightly loaded, lubricated rolling/sliding line contacts. Lubricant starvation in the contact has been created by gradually reducing the length of the computational domain from the inlet side. The performance parameters in the line contact have been evaluated for high-rolling speeds (15–45 m/s), light loads (10 × 103−17 × 103 N/m), and slip values varying up to 10 per cent. Significant reduction in minimum film thickness, traction coefficient, and maximum mid-film temperature rise has been observed with the increase in the severity of starvation. The analysis reveals that the existence of starvation seems to be beneficial in terms of reduced traction and temperature rise provided there is a continuous film at the contact. On the basis of this work, empirical relations are developed for the prediction of non-dimensional minimum film thickness, traction coefficient, and non-dimensional maximum mid-film temperature rise in the contact in terms of various operational parameters viz. thermal loading parameter ( Q), non-dimensional load ( W), slip ( S), and starvation parameter (| X s|).
Effect of thermo-elastic deformation on lubricated point contacts
Authors: Wang W-Z , Hu Y-Z , Wang H , Liu Y-C
Published: September 2006

In lubricated contacts, viscous shearing of lubricant and frictional heating inevitably result in thermo-elastic deformation of contacting surfaces, which will change the distribution of contact pressure, and hence affect the behaviour of the contact. This study presents a thermo-mechanical model for lubricated point-contacts problem. The model takes into account the interactions between pressure and temperature, and asperity distortion due to thermal and elastic deformations. A unified Reynolds equation system is used to obtain the pressure distribution, and an FFT-based algorithm is applied to speed up the calculation of temperature rise and surface deformations caused by the normal pressure and surface temperature rise. The results show that interfacial frictional heating results in thermo-elastic deformation comparable with elastic deformation. As a result, the gap between mating surfaces will be decreased, and the pressure near the centre of contact will be elevated, especially for rough surface and high speed.
The Nature of Kenya Vermiculite and its Aluminum Hydroxide Complexes
Authors: Brydon J. E. , Turner R. C.
Published: September 2006

A specimen of Kenya vermiculite contained no mica or chlorite layers either as separate phases or as components of an interstratifled structure. Dehydroxylation occurred in two stages, at 550° and 850°C, with approximately equal amounts of hydroxyl liberated in each stage. Al-saturated Kenya vermiculite showed low temperature dehydration characteristics similar to those of the natural Mg-saturated specimen, but the DTA, TGA and oscillating-heating X-ray diffraction patterns showed that the three stage dehydration process was not as clear-cut with the Al-saturated specimen.

As with montmorillonite, when small amounts of aluminum were precipitated by the addition of Ca(OH)2 in the presence of vermiculite, the Al(OH)x, was taken up and held indefinitely by the clay, the ion product (Al)(OH)3 in solution was maintained at 10-33∙0 and no gibbsite was formed with time. With large amounts, 800 and 1600 me Al(OH)x per 100g vermiculite, the hydroxide was held initially in the interlayer space, but gibbsite was eventually formed as (Al)(OH)3 approached the solubility product of gibbsite. Unlike montmorillonite, the vermiculite specimens retained an appreciable amount of the interlayer hydroxide and did not regain the original C.E.C. values as gibbsite was formed.

Al-vermiculite which was repeatedly suspended in AlCl3 with (Al)(OH)3 maintained at a value less than 10-33∙8 liberated 435 me Mg, took up 208 me Al as an interlayer hydroxide and caused a reduction in C.E.C. from 130 to 28 me per 100g clay. With vermiculite an appreciable amount of the interlayer Al(OH)x was stable with respect to gibbsite whereas with montmorillonite it was not.
Alkylammonium Decomposition on Montmorillonite Surfaces in an Inert Atmosphere
Authors: Durand B. , Pelet R. , Fripiat J. J.
Published: September 2006

A study of the thermal transformation of alkylammonium cations adsorbed on the surface of a montmorillonite in various conditions of hydration has been carried out. The experimental conditions were: inert atmosphere, temperatures below 250°C and time periods up to 270 days. The reactions observed are mainly transalkylations, for which a mechanism of acid catalysis is proposed. A high degree of dissociation of the water remaining on the surface of the clay is required and is attained for an optimal, and rather low, water content of the clay.
Thermodynamics of the Exchange of n-Alkylammonium Ions on Na-Montmorillonite
Authors: Vansant E. F. , Uytterhoeven J. B.
Published: September 2006

A thermodynamic study has been made of the ion exchange equilibria of the n-alkylammonium ions in sodium montmorillonite. Exchange isotherms of ammonium, methylammonium, ethylammonium, propylammonium and butylammonium with sodium montmorillonite were determined at 4°, 25° and 55°C. From these data the changes in free energy, enthalpy and entropy for the exchange reactions were calculated. In the temperature region used in this work, no enthalpy change was observed. Thus the exchange was only controlled by entropy effects. The thermodynamic excess functions were calculated from the surface activity coefficients. The affinity of the organic ions for the clay increases with chain length. It is shown that this increase can not be ascribed to van der Waals forces, but must be due to the combined effect of variations in electrostatic interactions with the clay lattice and of the hydration state.
Electron Optical Observations on Marblehead Illite
Authors: Güven Necip
Published: September 2006

Electron optical observations on Marblehead illite showed the presence of twinned aggregates of lath-shaped crystallites. The selected area diffraction patterns of these aggregates indicate a strict orientational relationship between them.

Original twinned mica flakes display all possible stages of the transformation of these micas into lath-shaped illites, where the a and b dimensions of layers do not show any noticeable changes, but c-dimension becomes shortened in the illites. The transformation seems to involve parting along (110) of the micas, subsequent H2O and OH inclusion in the structure and other possible chemical changes resulting from the hydration. The morphology and the size of lath-shaped crystallites displaying (001) and (110) forms seem to be responsible for the excess of water and K-deficiency in the Marblehead illite compared to the micas.

Individual illite laths commonly have a length 0·1–4 μ, a width of 0·01–0·1 μ and a thickness varying between 10 and 50 Å.
X-Ray Diffraction and Electron Optical Studies on Smectite and α -Cristobalite Associations
Authors: Güven Necip , Grim Ralph E.
Published: September 2006

Alteration products of volcanic materials from various localities in Wyoming, U.S.A., Italy, Yugoslavia and Mozambique are mainly smectites and cristobalites with small amounts of kaolinite.

Smectite and cristobalite form separate and intergrown aggregates of microcristallinity. X-ray diffraction studies show that the silica is α-cristobalite with a noticeable stacking disorder. Small aggregates of optically pure α-cristobalite, which were separated by an appropriate mixture of bromo-form and carbon tetrachloride, are shown to contain a noticeable amount of smectite on Debye-Scherrer diffraction photographs for the samples from Italy and Wyoming, U.S.A.

Transmission electron micrographs and selected area electron diffraction photographs show, in addition to smectite and α-cristobalite aggregates, the presence of idiomorph single crystals of kaolinite.
Selective Sorption and Fixation of Cations by Clay Minerals: A Review
Authors: Sawhney B. L.
Published: September 2006

Investigations concerning selective sorption and fixation of K and similar cations by clay minerals and soil clays and the mechanisms of these reactions are reviewed. In particular, recent observations on selective sorption of these ions in dilute solutions by weathered micas and vermiculite in relation to the interlayer structures are discussed in detail. Also, implications of the resistance to weathering of small mica particles to cation selectivity by soils are described. Despite the increased understanding of sorption and fixation reactions, the following aspects remain unclear.

First, the mechanism of the collapse of alternate layers in vermiculite on K or Cs sorption has not been unequivocally established. Second, factors that impart stability to the central core of mica particles so that K extraction becomes progressively difficult are not known. Third, inability of Ca or Mg ions to expand interlayers of Cs-saturated vermiculite in contrast to K-saturated vermiculite is not completely understood.
Dodecylammonium-Mica Complexes—II Characterization of the Reaction Products
Authors: Mackintosh E. E. , Lewis D. G. , Greenland D. J.
Published: September 2006

Interlayer potassium was removed from a wide range of mice minerals by treatment with dilute solutions of n-dodecylammonium chloride. On subsequent reaction with the appropriate metal methoxide, the Na+ or Ca2+ form of the altered mica was produced. The properties of the original and sodium saturated samples were compared to assess the changes in water content, charge density and chemical composition (particularly ferrous iron) which resulted from the displacement of potassium.

Calculation of structural formulae was not attempted since it was established that for the altered samples accurate distinction could not be made between adsorbed and structural water. Changes in layer charge are thus expressed on the basis of samples ignited to 1000°C. Charge losses of up to 76 me/100 g were recorded for biotites, smaller charges were noted for phlogopites and no loss was observed for the two muscovites examined.

Oxidation of ferrous iron occurred for all trioctahedral samples, the greatest oxidation occurring in the samples initially high in iron. There was no consistent relationship between the amount of iron oxidized and the loss of layer charge.

All altered samples contained greater amounts of H2O+ than the original materials suggesting that protonation of structural oxygens occurred during, or following, removal of potassium.

It is concluded that the alteration of micas by reaction with organic cations is a complex process, differing in detail for different micas, and following a similar path to alteration by reaction with inorganic salts.
The Occurrence of Sepiolite and Attapulgite on the Southern High Plains
Authors: McLean S. A. , Allen B. L. , Craig J. R.
Published: September 2006

Sepiolite and attapulgite have been found to be common, sometimes the major, clay minerals in calcareous lacustrine deposits on the southern High Plains in West Texas and eastern New Mexico. Deflation debris derived from the basins and calcareous soils developed in the debris and in the lacustrine deposits also often contain either or both minerals. Dolomite is the carbonate commonly associated with sepiolite and calcite has a similar relationship to attapulgite in the lacustrine deposits. Pedogenic formation of sepiolite and attapulgite appears unlikely in the area studied since an association with lacustrine materials was made in a very high percentage of the occurrences.

Sepiolite was found to be highly concentrated in the < 0•2μ fraction. A similar, but less pronounced, distribution was noted for attapulgite. The studies suggest that the minerals have developed authigenically in alkaline lacustrine environments during periods of desiccation. Such an environment, interrupted by more humid periods, would have obtained during dry Pleistocene intervals. Volcanic ash is suggested as the source of the essential silica. The Mg concentration would appear to determine whether sepiolite-dolomite or attapulgite-calcite were formed.
Selectivity Effect of Cesium on Clay Size Weathered Mica; Transmission Electron Microscopy Studies
Authors: Gal M. , Rich C. I.
Published: September 2006

The use of electron diffraction contrast to detect local concentrations of interlayer cations in mica-vermiculites was examined. Cs and Mg, because of their contrasting atomic scattering amplitudes for electrons, were chosen as exchange ions for Ca. Cs was absorbed to the near exclusion of Mg by the clays from the three soils and by weathered clay-size muscovite and phlogopite. The presence of Cs in addition to the other interlayer cations, K and Ca, caused bending and perhaps splitting of the mica-verrmculite layers. Extinction bend contours were common in Cs-treatea specimens but not those Ca-treated. After freeze-drying of specimens of Cs-Ca Nason clay, differential destruction by the electron beam of the central core in clay-size vermiculite containing hydrated Ca ions may indicate the edge location of Cs.
Transmission Electron Microscopy of Fine-Grained Phyllosilicates in Ultra-Thin Rock Sections
Authors: Phakey P. P. , Curtis C. D. , Oertel G.
Published: September 2006

A method is described for preparing electron-transparent sections of fine-grained argillaceous rocks suitable for making transmission micrographs. A sediment and a slate are used as examples. Sections perpendicular to bedding or cleavage yield diffraction patterns with clearly defined 00l reflections. These allow immediate identification of 7, 10 and 14 Å structures. The combination of detailed textural information with structural identification of individual phyllosilicate particles affords a powerful method for the investigation of late diagenetic and early metamorphic changes in sediments.
Irreversible Collapse of Montmorillonite
Authors: Ertem Gözen
Published: September 2006

A number of variable charge montmorillonites were prepared. One portion of each sample was extracted with ammonium chloride, while a second portion was first saturated with calcium chloride, washed, and then extracted with ammonium chloride. In both cases, the number of cations displaced by ammonium chloride was determined. The number of calcium ions displaced from Ca-saturated samples was higher than the sum of the number of lithium and calcium ions displaced from Li, Ca-mixed samples. The differences, increasing towards Li-rich end of the series are assumed to be due to protons liberated from the reaction of lithium ions with either structural hydroxyl groups or residual water molecules, as has been shown by other investigators. Supplementary X-ray and i.r. data lend support to this idea.
Extinction Bend Contours in Electron Microscopy of Clay-Size Mica-Vermiculites
Authors: Gal M. , Rich C. I.
Published: September 2006

Extinction bend contours, observed in Cs-treated mica-vermiculites by transmission electron microscopy, give information on the morphology and crystal orientation and continuity in individual particles of clay size. Interlayer Cs apparently stretches that part of the silicate sheet in closest proximity and when exchange by Cs is incomplete, warping of the particle occurs. Warping favors the appearance of bend contours in transmission electron microscopic images of the particles. These contours terminate at crystal boundaries within a particle. A specimen tilting stage is useful in bringing the contours into view and in “exploring” individual particles.
Montmorillonite Complexes With Dioxane, Morpholine, And Piperidine: Mechanisms of Formation
Authors: Brindley G. W. , Tsunashima Atsumu
Published: September 2006

The absorption of dioxane, morpholine and piperidine from dilute aqueous solutions by Li-, Ca-, and Cu-montmorillonite is measured by means of a differential refractometer. This instrument measures small differences in the refractive indices of two liquids and provides a useful method for determining the amount of organic material removed from solution by the clay. Corrections are required for the effect of desorbed cations on the differential refraction measurements. Neutral molecules are absorbed in amounts related to the exchange capacity of the clay probably by cation-dipole interactions. The results are consistent with the formation of complexes Li+-fi and R-Ca2+-R for the three organic materials used; Cu2+ ions behave like Ca2+ ions for dioxane, but form $\mathop >\limits_R^R C{u^{2 + }} - R$ complexes with morpholine and piperidine. Under acid conditions, morpholine and piperidine form organic cations RH+ which take part in cation exchange reactions and which are dominant at pH below about 5. Neutral molecule absorption also occurs by virtue of the presence of RH+ ions on the clay which form RH+-R complexes (hemisalt formation). When this last mechanism of absorption occurs, the total absorption is approximately twice that when a cation-dipole reaction or cation exchange alone operates. One-dimensional Fourier 00l syntheses of complexes in equilibrium with aqueous organic solutions indicate that water molecules are associated with the clay-organic complexes to the extent of about 5H2O/unit cell.
Adsorption of Ethylenediamine (EDA) on Montmorillonite Saturated with Different Cations—II. Hydrogen- and Ethylenediammonium-Montmorillonite: Protonation and Hydrogen Bonding
Authors: Cloos P. , Laura R. D.
Published: September 2006

The form under which ethylenediamine (EDA) is adsorbed from aqueous solution by hydrogen- and ethylenediammonium-montmorillonite was studied as a function of the amount of amine present in the system.

EDA added to the acid clay in quantities lower than or equal to the cation exchange capacity (C.E.C.) was exclusively adsorbed as ethylenediammonium (EDAH22+) ion. On further addition of diamine the pH of the suspension rose to alkaline values and the monoprotonated species (EDAH+) was the main charge balancing cation.

Evaporating at room temperature “EDA-H-montmorillonite-H2O” or “EDA-EDAH2-mont- morillonite-H2O” systems containing 300 me EDA/100 g clay did not cause loss of nitrogen, but degassing under high vacuum (10−5 mm Hg) did. Nevertheless, excess EDA molecules with respect to the C.E.C. were retained on the clay surface, at the expense of water molecules, through strong asymmetrical hydrogen bonds between their NH2 groups and the NH3+ groups of EDAH+ ions. On heating up to 160°C under vacuum the nitrogen content decreased further, but still remained at a level significantly higher than the C.E.C. value, all NH3+ groups remaining involved in strong hydrogen bonding. It is suggested that a “condensation” process takes place, implying evolution of EDA molecules and giving rise to “polymeric” associations between protonated and unprotonated diamine.

Washing the clay suspensions with distilled water did not completely remove excess EDA either, as a consequence of the equilibrium existing between the ionic species in solution (EDAH22+ and EDAH+) and on the clay surface. It seems that these species were preferentially adsorbed as “trimeric” associations in which two out of four NH3+ groups are hydrogen bonded to NH2 groups.

After heating at 200°C, nitrogen retained on the clay surface was mainly in the form of NH4+ ions. Ammonium formation was enhanced by the presence of excess EDA and was considerably faster than in montmorillonite systems containing EDA coordinated to Cu2+ ions.
The Chlorite Series of Flagstaff Hill Area, California: A Preliminary Investigation
Authors: Post J. L. , Plummer C. C.
Published: September 2006

The results of X-ray diffraction, DTA, i.r. spectroscopy, and chemical tests are presented for some chlorites typical of the Flagstaff Hill area. The area is notable for the large variety of chlorite types occurring in considerable quantities. Chlorite, in this area, is found as veins, as pseudomorphs, and as individual crystals. Textures vary from massive, fine-grained aggregates to books which are more than 20 mm in width. Crystals more than 5 mm in size occur in parallel groupings at rock interfaces. Judging from 45 chlorite samples studied, sheridanite is most abundant; clinochlore and ripidolite are common. Penninite and its Cr-chlorite equivalent are less abundant. The parent rock is an irregularly shaped ultramafic body surrounded by low-grade schists and located very close to a granodiorite stock. The original ultramafic rocks have been highly altered by metamorphism and metosomatism into assemblages comprised mainly of serpentine, talc, hornblende, and chlorite with relics of olivine, pyroxene, and other less abundant original minerals. Much of the exposed rock is essentially monomineralic, mostly consisting of various polytypes of serpentine. Preliminary investigation indicates that the area merits much more study because of the opportunity for readily observing the various chlorite types and determining their genesis, alteration sequences and weathering characteristics. The area, being easily accessible, could also serve as an adequate source for samples to be used as reference standards.
Comparative Chemical Composition of Sediment Interstitial Waters
Authors: Parashiva Murthy A. S. , Ferrell R. E.
Published: September 2006

Interstitial waters squeezed from modem sediments with a 100 psi pressure at laboratory temperature (23°C) are depleted in K and Ca and enriched in Mg when compared to the solutions obtained at in situ temperature (28°C). The changes are especially pronounced when the samples are refrigerated during transport back to the laboratory. The magnitude of the variation in chemical composition was dependent on the element being analyzed as well as the sediment used. The maximum observed depletion in the laboratory was about 12% per degree difference in temperature for potassium. Element ratios in the solutions were affected most seriously. The Mg/Ca and Na/K ratios increased 51 and 60% respectively.

A water extraction method using sediment to water ratios of 1:2, 1:5, and 1:10 was compared with the pressure method. The total composition of the pore fluids obtained by squeezing is greater than expected, corresponding to a sediment to water ratio less than 1:5. The artificially squeezed sediments are yielding pore fluids which are more concentrated than the “in-place” solutions.

The water extraction method yields results which are in agreement with the behavior predicted by the Donnan Principle. It is suggested that the values obtained by successive dilution analyses can be extrapolated to measured moisture contents and used to determine the elemental composition and element ratios in interstitial pore fluids.
Clay Mineral Synthesis — III Rapid Hydrothermal Crystallization of An Aluminian Smectite
Authors: Granquist W. T. , Hoffman G. W. , Boteler R. C.
Published: September 2006

An aluminian smectite with about one Al3+/Si4+ replacement per unit cell was batch- synthesized on a large scale (100-gal autoclave) at 3 00°C and 1240 psig with reaction times of several hours rather than days. This rapid crystallization was related to the use of NH4+ as the charge-balancing cation and to partial F/OH substitution. The short synthesis time prompted a study of continuous crystallization. Either of two techniques, flow through a stirred autoclave and through a multi-staged reactor column, produced crystalline product; neither gave the crystallinity of the batch process.
Reactions between Fulvic Acid and Cu2+-Montmorillonite
Authors: Schnitzer M. , Kodama H.
Published: September 2006

Shaking of water-soluble fulvic acid with Cu2+-montmorillonite at pH 2·5 increased the interlamellar spacing from 10·0 to 15·1 A. The spacings were measured at ≈ 0% relative humidity. The extent of interlayer adsorption decreased with increase in pH. Differential thermal analysis and thermogravimetric examinations showed that in addition to interlayer adsorption, fulvic acid was also retained on external clay surfaces. The FA was held so tightly by the Cu2+-clay that > 3/4 of the total amount adsorbed, including degradation products formed from it, resisted decomposition even when heated to 1000°C. I.R. spectra showed that β-diketone groups in fulvic acid reacted with Cu2+ in or on the clay to form acetylacetonate-type chelates. Indications were obtained that the mechanism postulated for the FA-Cu2+-clay interaction may also apply to reactions between FA and montmorillonite saturated with other di- and trivalent metal ions. Reactions of FA in aqueous solutions with metal ions in the presence of clays differ from those in the absence of clay. Montmorillonite appears to affect the conformation of the fulvic acid polymer in a way that favours reactions between C=O groups and metal ions, a type of reaction that has so far not been observed in aqueous solutions in the absence of clay.
The Stability of Gibbsite and Boehmite at the Surface of the Earth
Authors: Chesworth Ward
Published: September 2006

Two mutually exclusive views exist concerning the relative stabilities of gibbsite and boehmite in soils. These are examined in terms of experimental and thermodynamic evidence and it is shown that all three possible divariant assemblages of two phases that can exist between gibbsite, beohmite and H2O, may do so at 25°C and 1 atmosphere total pressure depending on the status of H2O. It is further shown that the conditions of H2O chemical potential needed to stabilize boehmite + H2O relative to gibbsite + H2O or gibbsite + boehmite, are unlikely to occur in natural waters in the zone of weathering.
Imogolite and Allophane Formed in Saprolite of Basalt on Maui, Hawaii
Authors: Wada K. , Henmi T. , Yoshinaga N. , Patterson S. H.
Published: September 2006

Inorganic gel and allophane collected from basaltic saprolite on Maui, Hawaii, and studied by Patterson in 1964 were reexamined. The main constituent of the gel is imogolite, and gibbsite and allophane are the minor constituents. Electron and X-ray diffraction patterns, DTA curve, and an infrared spectrum of the gel are characteristic of imogolite. The allophane is virtually noncrystalline to X-rays but contains a small amount of imogolite in relatively short threads. High-resolution electron micrographs indicate differences in structural organization between allophane and imogolite and suggest crystallization of imogolite from allophane.

The occurrence of imogolite as a weathering product has been reported in many localities from pyroclastic materials but not from massive rocks. Probably the exceptionally high rainfall, excellent subsurface permeability of the weathered material, and the low pH and high organic content of the leaching solution provide favorable conditions for formation of imogolite from basalt on Maui.
Determination of Chlorite Compositions by X-Ray Spacings and Intensities
Authors: Bailey S. W.
Published: September 2006

The cell dimensions and compositions of four chlorites whose crystal structures have been determined in detail are used to test existing graphs and regression equations designed to give tetrahedral and octahedral compositions. It is found that the thicknesses of the tetrahedral sheet, the 2:1 octahedral sheet, the interlayer sheet, and the space between the 2:1 layer and the interlayer can vary appreciably from specimen to specimen quite independently of tetrahedral composition. Total octahedral composition, the number of octahedral vacancies, cation ordering, and the distribution of trivalent cations and of charge between the two octahedral sheets must have effects on d(001) that are additional to the effect of tetrahedral composition. Nevertheless, Brindley’s d(001) graph and a regression equation by Kepezhinskas both should give tetrahedral compositions with an average error of 10%, or about 0·1 AlIV, for most trioctahedral chlorites. They are not valid for dioctahedral or di, trioctahedral species. Equations derived from the data of von Engelhardt and of Shirozu relating the b parameter to octahedral Fe, Mn content give results with an average error of 10%, or 0·1 Fe, Mn, for the four test chlorites provided Cr is included with the Fe, Mn, as does a regression equation by Kepezhinskas that contains terms for both the b parameter and d(001). Methods using the (00l) intensities or structure amplitudes give less consistent results for heavy atom contents than the spacing methods, but can be used to give approximate values for the asymmetry in distribution of heavy atoms between the 2:1 octahedral sheet and the interlayer.
Tioga Bentonite (Middle Devonian) of Indiana
Authors: Droste John B. , Vitaliano Charles J.
Published: September 2006

The petrography of shale partings in carbonate rocks from eleven cores in the Illinois (Jeffersonville Formation) and Michigan Basins (Detroit River Formation) of Indiana indicates the presence of a K-bentonite which is interpreted as the Tioga Bentonite, an important stratigraphic marker in the middle Devonian rocks throughout the central and eastern United States. The clay mineral composition of the Tioga Bentonite of Indiana is interstratified illite and smectite, usually with admixed kaolinite. This composition stands in striking contrast to the simple illite suite without kaolinite in the normal terrigenous shale partings in the Devonian rocks of Indiana. Euhedral sanidine, high temperature albite, zircon, apatite, and the angularity of quartz grains found associated only with the interstratified clay mineral suite support the volcanic origin of these clay partings.
Mixed-Layer Kaolinite-Montmorillonite: A Comparison of Observed and Calculated Diffraction Patterns
Authors: Sakharov B. A. , Drits V. A.
Published: September 2006

X-ray diffraction patterns for mixed-layer kaolinite-glycerine-saturated montmorillonite were calculated, taking into account the differences of scattering power of kaolinite and montmorillonite layers. The data were compared with the experimental results for two kaolinite-montmorillonite mixed-layer minerals. The probability parameters and the total number of layers in crystals were established.
The Nature of Garnierites —I Structures, Chemical Compositions and Color Characteristics
Authors: Brindley G. W. , Hang Pham Thi
Published: September 2006

X-ray diffraction patterns of garnierites indicate that most samples resemble serpentine-group minerals or a talc-like mineral, or a mixture of these forms, and give respectively 7 Å and 10 Å basal reflections. From a survey of some 40 garnierites, four of predominantly serpentine type and seven of predominantly talc-like type were selected for detailed study. The talc-like garnierites exhibit little variation of the 10 Å basal spacing with low-temperature heating or with immersion in liquids, though some may contain a small proportion of expandable layers. Chemical analyses show considerable deviations of octahedral/tetrahedral cation ratios from the values 3/2 and 3/4 for normal serpentine and talc minerals, and may be interpreted in terms of mixed 1:1 and 2:1 layer types, either as separate phases and/or as interstratifications, or as defect structures of various kinds. The H2O + contents of the talc-like forms of garnierite are considerably greater than that of normal talc and point to a mineral of composition 3(Mg, Ni)O·4SiO2. 2H2O or [(Mg, Ni)3Si4O10(OH)2]H2O—a talc mono-hydrate formula. The green color of garnierites is related to the NiO weight per cent and a color index is derived based on the Munsell color charts.
Optical Absorption Spectra of Clay Minerals
Authors: Karickhoff Samuel W. , Bailey George W.
Published: September 2006

A preliminary survey of electronic absorption spectra of clay minerals reveals the utility of u.v.-visible spectroscopy in the elucidation of structural, physical, and chemical properties of such systems. Spectra, which were obtained in the suspension, film, and single crystal states (where applicable), are interpreted in terms of iron-associated transitions. Microcrystalline clay minerals typically show Fe(lll) in octahedral oxo-ligand geometry whereas mica-type minerals may show a range of iron species, including octahedral Fe(III), tetrahedral Fe(III), and octahedral Fe(II). Iron affects the local site geometry and in “high iron” minerals may dictate layer geometry and subsequently the crystalline form.