bluuebunny/crossref_metadata_2025 huggingface dataset:
Metabolic Imaging Predicts Response, Survival, and Recurrence in Adenocarcinomas of the Esophagogastric Junction
Authors: Ott Katja , Weber Wolfgang A. , Lordick Florian , Becker Karen , Busch Raymonde , Herrmann Ken , Wieder Hinrich , Fink Ulrich , Schwaiger Markus , Siewert Jörg-Rüdiger
Published: September 2006

Purpose

A previous study suggested that measurement of therapy-induced changes in tumor glucose metabolism by positron emission tomography (PET) with the glucose analog [18F]fluorodeoxyglucose (FDG) allows to select patients most likely to benefit from preoperative chemotherapy in adenocarcinomas of the esophagogastric junction (AEG). The aim of this study was to prospectively validate these findings by using an a priori definition of metabolic response.

Patients and Methods

Sixty-five patients with locally advanced AEGs were included. Tumor glucose utilization was quantitatively assessed by FDG-PET before chemotherapy and 14 days after initiation of therapy. Patients were classified as metabolic responders when the metabolic activity of the primary tumor had decreased by more than 35% at the time of the second PET.

Results

Metabolic responders showed a high histopathologic response rate (44%) with a 3-year survival rate of 70%. In contrast, prognosis was poor for metabolic nonresponders with a histopathologic response rate of 5% (P = .001) and a 3-year survival rate of 35% (P = .01). A multivariate analysis (covariates: ypT-, ypN-category, histopathologic response) demonstrated that metabolic response was the only factor predicting recurrence (P = .018) in the subgroup of completely resected (R0) patients.

Conclusion

This study prospectively demonstrates that changes in tumor metabolic activity during chemotherapy predict response, prognosis, and recurrence. These data provide the basis for clinical trials in which preoperative treatment is changed for patients without a metabolic response early in the course of therapy. PET-guided induction therapy may even be applicable to earlier tumor stages because surgery is only minimally delayed in nonresponding patients.
Relations, Objects, and the Composition of Analogies
Authors: Gentner Dedre , Kurtz Kenneth J.
Published: September 2006

This research addresses the kinds of matching elements that determine analogical relatedness and literal similarity. Despite theoretical agreement on the importance of relational match, the empirical evidence is neither systematic nor definitive. In 3 studies, participants performed online evaluations of relatedness of sentence pairs that varied in either the object or relational match. Results show a consistent focus on relational matches as the main determinant of analogical acceptance. In addition, analogy does not require strict overall identity of relational concepts. Semantically overlapping but nonsynonymous relations were commonly accepted, but required more processing time. Finally, performance in a similarity rating task partly paralleled analogical acceptance; however, relatively more weight was given to object matches. Implications for psychological theories of analogy and similarity are addressed.
Uncertainty About the Rest of the Sentence
Authors: Hale John
Published: September 2006

A word‐by‐word human sentence processing complexity metric is presented. This metric formalizes the intuition that comprehenders have more trouble on words contributing larger amounts of information about the syntactic structure of the sentence as a whole. The formalization is in terms of the conditional entropy of grammatical continuations, given the words that have been heard so far. To calculate the predictions of this metric, Wilson and Carroll's (1954) original entropy reduction idea is extended to infinite languages. This is demonstrated with a mildly context‐sensitive language that includes relative clauses formed on a variety of grammatical relations across the Accessibility Hierarchy of Keenan and Comrie (1977). Predictions are derived that correlate significantly with repetition accuracy results obtained in a sentence‐memory experiment (Keenan & Hawkins, 1987).
Unsupervised Discovery of Nonlinear Structure Using Contrastive Backpropagation
Authors: Hinton Geoffrey , Osindero Simon , Welling Max , Teh Yee‐Whye
Published: September 2006

We describe a way of modeling high‐dimensional data vectors by using an unsupervised, nonlinear, multilayer neural network in which the activity of each neuron‐like unit makes an additive contribution to a global energy score that indicates how surprised the network is by the data vector. The connection weights that determine how the activity of each unit depends on the activities in earlier layers are learned by minimizing the energy assigned to data vectors that are actually observed and maximizing the energy assigned to “confabulations” that are generated by perturbing an observed data vector in a direction that decreases its energy under the current model.
Ephrin A/EphA controls the rostral turning polarity of a lateral commissural tract in chick hindbrain
Authors: Zhu Yan , Guthrie Sarah , Murakami Fujio
Published: September 2006

Most post-crossing commissural axons turn into longitudinal paths to make synaptic connections with their targets. Mechanisms that control their rostrocaudal turning polarity are still poorly understood. We used the hindbrain as a model system to investigate the rostral turning of a laterally located commissural tract, identified as the caudal group of contralateral cerebellar-projecting second-order vestibular neurons (cC-VC). We found that the caudal hindbrain possessed a graded non-permissive/repulsive activity for growing cC-VC axons. This non-permissiveness/repulsion was in part mediated by glycosyl-phosphatidylinositol (GPI)-anchored ephrin A. We further demonstrated that ephrin A2 was distributed in a caudal-high/rostral-low gradient in the caudolateral hindbrain and cC-VC axons expressed EphA receptors. Finally,perturbing ephrin A/EphA signalling both in vitro and in vivo led to rostrocaudal pathfinding errors of post-crossing cC-VC axons. These results suggest that ephrin A/EphA interactions play a key role in regulating the polarity of post-crossing cC-VC axons as they turn into the longitudinal axis.
MES-4: an autosome-associated histone methyltransferase that participates in silencing the X chromosomes in theC. elegansgerm line
Authors: Bender Laurel B. , Suh Jinkyo , Carroll Coleen R. , Fong Youyi , Fingerman Ian M. , Briggs Scott D. , Cao Ru , Zhang Yi , Reinke Valerie , Strome Susan
Published: September 2006

Germ cell development in C. elegans requires that the X chromosomes be globally silenced during mitosis and early meiosis. We previously found that the nuclear proteins MES-2, MES-3, MES-4 and MES-6 regulate the different chromatin states of autosomes versus X chromosomes and are required for germline viability. Strikingly, the SET-domain protein MES-4 is concentrated on autosomes and excluded from the X chromosomes. Here, we show that MES-4 has histone H3 methyltransferase (HMT) activity in vitro, and is required for histone H3K36 dimethylation in mitotic and early meiotic germline nuclei and early embryos. MES-4 appears unlinked to transcription elongation, thus distinguishing it from other known H3K36 HMTs. Based on microarray analysis, loss of MES-4 leads to derepression of X-linked genes in the germ line. We discuss how an autosomally associated HMT may participate in silencing genes on the X chromosome, in coordination with the direct silencing effects of the other MES proteins.
A Group Theoretical Derivation of a More General Mobility Criterion for Parallel Manipulators
Authors: Rico J M , Aguilera L D , Gallardo J , Rodriguez R , Orozco H , Barrera J M
Published: September 2006

This contribution presents a group theoretical derivation of the mobility criterion applicable to parallel manipulators, which has been previously presented by the authors [1]. Unlike previously employed mobility criteria based on the well-known Kutzbach-Grübler criterion that often fails to provide the correct number of degrees of freedom of parallel manipulators, the mobility criterion, whose group theoretical derivation is presented here, provides the correct number of degrees of freedom for a wider class of parallel manipulators. In this reference the authors proved the mobility criterion by resorting to the Lie algebra, se(3), also known as screw algebra, of the Euclidean group; SE(3). In this contribution, the authors prove the same criterion but, in this case, by an analysis of the subgroups and subsets of the Euclidean group, SE(3).
Investigation of a Cylindroid Engendered by the Bennett Linkage
Authors: Baker J E
Published: September 2006

Most studies of the Bennett linkage over the past century have been concerned with the characteristics of its instantaneous motion, revealing a large number of features and relationships. Latterly, work has been carried out on properties of the finite motion, an evidently separate area of consideration. However, there is one item of commonality between the two zones of activity, namely, the instantaneous screw axis of the loop's coupler. This fact is directed towards the employment of results from the former area of study to the benefit of the latter.
Freedom and Constraint in Coupling Networks
Authors: Davies T H
Published: September 2006

Kirchhoff's circulation law has previously been adapted for studies of under-constraint. Here Kirchhoff's cutset law is also adapted for studies of overconstraint. The two procedures are presented in tandem to emphasise their duality. The same tasks are then undertaken using dual virtual power methods. One is a new procedure for underconstraint that introduces the concepts of cutset motion and virtual action, dual with previously reported circuit action and virtual motion. Of the four methods described, the superior ones for each task are identified.
Study of Dead-Centre Positions of Single-Degree-of-Freedom Planar Linkages Using Assur Kinematic Chains
Authors: Pennock G R , Kamthe G M
Published: September 2006

The article presents an original technique, using the concept of Assur kinematic chains (AKCs), to determine whether a single-degree-of-freedom planar linkage is in a dead-centre position, i.e. a position where the input link is instantaneously stationary. An AKC is a special structure with mobility zero from which it is not possible to obtain a simpler substructure of the same mobility by removing one or more links. The article presents the concept of modularization of planar linkages into AKC based on the choice of the input link. Then, the article presents the constraints on the locations of the instantaneous centres of zero velocity (or instant centres) for a single-degree-of-freedom planar linkage to be in a stationary configuration, i.e. a configuration where one, or more, of the links is instantaneously stationary. The article shows that constraints on the locations of the instant centres for a stationary configuration are satisfied if an AKC, as part of the linkage, gains a degree of freedom. As the modularization of a planar linkage is based on the choice of the input link, the stationary configurations, determined by this method, are in fact dead-centre positions. Finally, this method is applied to indeterminate linkages, i.e. a class of single-degree-of-freedom planar linkages for which it is not possible to locate all the secondary (or unknown) instant centres by the direct application of the Aronhold—Kennedy theorem.
Kinematic Synthesis of Spatial Serial Chains Using Clifford Algebra Exponentials
Authors: Perez-Gracia A , McCarthy J M
Published: September 2006

This article presents a formulation of the design equations for a spatial serial chain that uses the Clifford algebra exponential form of its kinematics equations. This is the even Clifford algebra C+( P3), known as dual quaternions. These equations define the position and orientation of the end effector in terms of rotations or translations about or along the joint axes of the chain. Because the coordinates of these axes appear explicitly, specifying a set of task positions these equations can be solved to determine the location of the joints. At the same time, joint parameters or certain dimensions are specified to ensure that the resulting robotic system has specific features.
Expandable Polyhedral Mechanisms Based on Polygonal One-Degree-of-Freedom Faces
Authors: Gosselin C M , Gagnon-Lachance D
Published: September 2006

In this article, a new family of expandable mechanisms is presented. The proposed mechanisms are expandable polyhedra built using one-degree-of-freedom (one-DOF) planar linkages. The latter planar linkages have the shape of polygons and can be expanded while preserving their shape in any of their configurations. The planar mechanisms are used to form the faces of a polyhedron. They are assembled using spherical joints at the vertices of the polyhedron. The result is a one-DOF movable polyhedron which can be expanded while preserving its shape. The application of the principle on regular polyhedra is first presented. For the five Platonic solids, theoretical maximum expansion ratios are computed, simulation results are given, and two prototypes are shown. Then, two additional examples are provided to illustrate the application of the principle to irregular polyhedra.
Kinetostatic Design of an Innovative Schönflies-Motion Generator
Authors: Angeles J , Caro S , Khan W , Morozov A
Published: September 2006

In this paper, a novel parallel robot is introduced. The robot, a Schönflies-motion generator (SMG), is capable of a special class of motions, namely those produced with serial robots termed SCARA (selective-compliance assembly robot arm). These motions involve three independent translations and one rotation about an axis of fixed direction. Such motions are known to form a subgroup of the displacement group of rigid-body motions, termed the Schönflies subgroup. The SMG is composed of two identical four-degree-of-freedom serial chains in a parallel array, sharing one common base and one common moving platform. The proximal module of each chain is active and has two controlled axes, the motors being installed on the fixed base. The links can thus be made light, thereby allowing for higher operational speeds. The distal module, in turn, is passive and follows the motions of its active counterpart, the whole mechanism giving, as a result, a four-degree-of-freedom motion to its end platform.
Elastohydrodynamic lubrication calculation and measure for crossed helical gears
Authors: Xu L , Yang C
Published: September 2006

In this article, based on the mesh theory, the principal curvatures of the tooth surfaces for the crossed helical gears and their induced normal curvatures are analysed. The equation of the minimum oil film thickness for the crossed axis helical gears has been presented using the elastohydrodynamic lubrication theory. The minimum oil film thickness for the crossed helical gears has been calculated. Physical and mathematical models for the measure of the oil film thickness have been presented and a measure device designed and manufactured. Using the above measure device, tested results of the oil film thickness for the drive have been given and compared with the calculated values. The calculated values are in good agreement with the tested results.
Bifurcation and chaos of a flexible rotor supported by turbulent journal bearings with non-linear suspension
Authors: Chang-Jian C-W , Chen C-K
Published: September 2006

This study presents a dynamic analysis of a rotor supported by two turbulent model journal bearings with non-linear suspension. The dynamics of the rotor centre and bearing centre are studied. The analysis of the rotor-bearing system is investigated under the assumptions of turbulent lubricant flow and a short bearing approximation. The spatial displacements in the horizontal and vertical directions are considered for various non-dimensional speed ratios. The dynamic equations are solved using the fourth-order Runge-Kutta method. The analysis methods employed in this study is inclusive of the dynamic trajectories of the rotor centre and bearing centre, power spectra, Poincaré maps, and bifurcation diagrams. The maximum Lyapunov exponent analysis is also used to identify the onset of chaotic motion. The numerical results show that the stability of the system varies with the non-dimensional speed ratios. Specifically, it is found that the dynamic behaviours of the system include 3 T-periodic, jump phenomena, and chaotic motions. The modelling results thus obtained by using the method proposed in this paper can be employed to predict the stability of the rotor-bearing system and the undesirable behaviour of the rotor and bearing centre can be avoided.
Dynamic performance of a thin film temperature sensor in a lubricated contact
Authors: Jia Y , Araya G
Published: September 2006

A thin film temperature sensor integrated onto mechanical component surface is promising for real-time machine condition monitoring. In this article, a one-dimensional heat conduction model has been developed to study the dynamic performance of the thin film sensor designed for monitoring the temperature distribution in an elastohydrodynamic lubrication contact. A control volume approach was used to numerically analyse the effects of sensor film thickness (from 0.1 to 100 μm), sensing materials, and substrate materials on the transient time response of the thin film sensor. The numerical model was evaluated by an analytical solution in a semi-infinite domain. The sensor time constant is obtained on the basis of a constant heat load and sensor sensitivity is studied when a typical elastohydrodynamic pressure distribution in a lubricated contact is applied. Faster response time and short time delay of a thin film sensor are expected in a higher conductivity of substrate. It is also clear that the response time decreases with increasing sensor film thickness and with increasing conductivity of the substrate. The results show that when the thickness of the sensor is < 1 μm, the sensor is feasible to capture transient temperature profile in real time for machine health monitoring under various operating conditions. One of the experimental validations given in this article has proven the robustness of the developed model.
Comparative study on wear behaviour of magnesium and aluminium alloys
Authors: Elleuch R , Elleuch K , Mnif R , Fridrici V , Kapsa P , Khélifati G
Published: September 2006

Magnesium is the lightest metal used in structural applications, such as aerospace industry, and therefore, it provides the greatest potential for weight or energy reduction. It is particularly suitable for transport technology applications. In order to substitute aluminium alloys in aeronautical engines, wear behaviour of magnesium alloys is considered. A comparison of the unlubricated wear resistance of an aluminium alloy (A 357) and two magnesium alloys (AZ 91 and WE 43) rubbed against 52 100 bearing steel in a pin-on-ring configuration over a range of sliding speed (1-7 m/s) and applied normal loads (20-80 N) is established. In addition to the measurement of the friction force and wear depth, the temperature near the sliding contact is also measured using a thermocouple placed at the back of the pin sample. Thermal effect on friction and worn surfaces are observed and characterized. Wear transitions are found for the AZ 91 and the A 357 alloys. These transitions are controlled by critical temperatures at the contact surfaces. Scanning electron microscopy observations and profilometric analyses are conducted to confirm these transitions and identify the wear mechanisms.
Swelling Characteristics of Hydroxy-Aluminum Interlayered Clays
Authors: Kidder Gerald , Reed Lester W.
Published: September 2006

The hypothesis tested was that macroscopic swelling of montmorillonitic clays is reduced by the presence of interlayer minerals. Fine and coarse clay fractions of Camargo and Panther Greek bentonite samples were artificially interlayered by reaction of Al2(SO4)3 and NaOH in 0∙5% suspensions of the clays. All four clay fractions reacted similarly to artificial interlayering. At an Al:clay ratio of 16 meq Al/g clay the CEC was completely lost, surface area was reduced and X-ray basal spacings were altered. No macroscopic swelling occurred in samples treated with 16 meq of Al/g of clay. At smaller concentrations of hydroxy-aluminum 8 and 2 meq Al/g clay, the clay properties were less drastically altered. Extraction of interlayered clays with Na citrate restored the original C.E.C., surface area, and basal spacings of all samples and resulted in some slight enhancement of C.E.C. and surface areas of the coarse fractions. Treatment with hot Na citrate resulted in an increase in swelling ability but only slight increases in C.E.C. and surface area. Evidence presented supports the hypothesis that macroscopic swelling of montmorillonitic clays is greatly reduced by interlayer materials. Reduced swelling due to interlayering occurs even when other clay properties may be slightly different from those of nontreated samples. Indications are that interlayer material occurs naturally in the clays studied and this may apply to other bentonite deposits.
Calcium-Magnesium Exchange in Montmorillonite and Vermiculite
Authors: Levy Rachel , Shainberg I.
Published: September 2006

An experimentally determined Ca-Mg exchange isotherm of montmorillonite is reported. The selectivity coefficient of this exchange over a wide range of Mg saturation was calculated and found constant.

Standard free energies of exchange, thermodynamic equilibrium constants and activity coefficients of the exchangeable Ca and Mg ions in vermiculite and montmorillonite, were predicted from knowledge of the microstructure of these two clays, assuming that coulombic forces are the main ones playing a role in the interaction between the counterions and the charged clay surface. The standard free energies of exchange (ΔGCa°Mg = 238 cal/mole) predicted a preference for Ca in montmorillonite and a preference for Mg in vermiculite (ΔGCa°Mg = - 1665 cal/mole). The predicted thermodynamic equilibrium constants were compatible with the experimentally determined selectivity coefficients KsCaMg = 0·67 as compared with KsCaMg = 0·68 in montmorillonite, which remains constant over all the range of Mg saturation, and KCaMg = 16·7 as compared with KsCaMg = 13·9 in vermiculite at 95% Mg saturation. The activity coefficients of Ca and Mg counterions in montmorillonite were found to be and , respectively, and to remain constant. The activity coefficients of exchangeable Ca and Mg in vermiculite were found to be and , respectively, at an equivalent fraction of unity. The activity coefficient of exchangeable Mg increased as the saturation with Mg decreased, and was found to be 1·7 × 10-3 in the range of the low Mg saturation.

The microstructure, the isomorphic substitution and the surface charge density provided an understanding of the changes taking place in the activity coefficients of the counterions.
The I.R. Spectrum of Structural Hydroxyls of K-Depleted Biotites
Authors: Chaussidon J.
Published: September 2006

The i.r. spectrum of K depleted biotites (structural OH stretching range) has been studied with monocrystals equilibrated at various water contents. Prior to spectroscopic measurements, the samples were submitted to deuteration treatments which displaced the hydration water spectrum to the OD region and made it possible to observe the behaviour of the structural hydroxyls without interference from hydration water.

In these conditions it was shown that the high frequency absorption of K depleted biotites (N + I bands) is the sum of two absorptions: the first corresponds to the initial mica spectrum, the second corresponds to the hydrated phase in which component bands (according to Vedder and Wilkins) are shifted by 36 cm-1 towards low frequencies.

Simultaneously it was shown that low frequency bands (V bands) decreased in intensity. This unexpected observation has been explained by a partial deuteration of structural OH, which takes place during the preliminary contacts of the samples with D2O vapour.
Geochemical Mechanics for the Dissolution, Transport, and Deposition of Aluminum in the Zone of Weathering
Authors: Huang W. H. , Keller W. D.
Published: September 2006

Organic acids in the 0·01M concentration range representing amino-, aliphatic, and aromatic types present in humus dissolve 70–85 ppm Al from Arkansas bauxite at room temperature, whereas 0-03 ppm is dissolved in water. The species of Al in aqueous solution, calculated from stability data, range from Al3+ at pH 3 and lower, through Al2(OH)24+ at a maximum concentration at pH 4·5, Al(OH)2+ at a maximum at pH 4·7, Al(OH)2+ at a maximum at pH 60, to Al(OH)4- at pH 8·5 and higher. In salicylic acid an Al-Sal+ complex occurs between pH 1·5 and 8·5, and is at a maximum at pH 4·2. Solubility of Al obviously is pH dependent; also because of the vulnerability of organic acids to oxidation, the solubility and transport of Al is indirectly Eh dependent. Anions that combine with Al include OH- to form bauxite, PO43- to form lateritic phosphate such as the Bone Valley Formation, Fla., and SiO44- to form allophane or kaolin as noted in the kaolin synthesis by Linares and Huartes. Spongelike, pisolitic or oolitic structures, and mineral veins in bauxites, lateritic phosphates, and some flint clays attest to mobilization of Al in solution. Lignites and humus zones associated with latentes are a logical geologic source of these complexing organic solvents. Although Al is inherently mobile, such commonly available precipitating anions render Al relatively immobile.
Catalytic Activity of Sodium Kaolinites
Authors: Hawthorne D. G. , Solomon D. H.
Published: September 2006

Kaolinites, catalytically active for the polymerization of styrene, can be deactivated by treatment with 1N aqueous sodium chloride. Subsequent washing of the sodium kaolinite results in a facile hydrolysis yielding an active hydronium/aluminum kaolinite in which the exchangeable cations act as surface Br0onsted acid initiation sites.
The I.R. Spectra of Lysine Adsorbed on Several Cation-Substituted Montmorillonites
Authors: Do Jang Sung , Condrate Robert A.
Published: September 2006

The i.r. spectra (4000-1200 cm-1) are obtained for several cation-substituted-montmonl-lonite-lysine complexes that were prepared at their natural pH’s. Analyses of the spectra of copper-, cobalt-, nickel- and zinc-montmorillonite films indicate that bidentate chelate complexes which contain protonated ∈-amino-groups are present in the interlamellar spaces. Investigation of the spectra of the hydrogen-, calcium- and natural-montmorillonite films indicates that the dominant adsorbed species for these complexes is a lysine cation in which both the α- and the ɛ-amino-groups are protonated while the carboxyl group is ionized.
Relation Between Swelling, Water Properties and b-Dimension in Montmorillonite-Water Systems
Authors: Ravina Israela , Low Philip F.
Published: September 2006

The b-dimensions of the unit cells of six different Na-saturated montmorillonites were determined by X-ray diffraction at water contents ranging from 0 to 20 g per g of montmorillonite. In every case, the b-dimension increased progressively with water content from its initial value, which was characteristic of each dry montmorillonite, to a final value of ~9•0Å, which was common to all montmorillonites. The latter value was reached when the water contents of the respective montmorillonites were equal to those at maximal swelling. When these water contents were plotted against the corresponding changes in b-dimension, a straight line that passed through the origin was obtained.

Different structure-sensitive properties of the water in montmorillonite-water systems (i.e. the partial specific volume, the amount remaining unfrozen at −5°C and the activation energy required for ions to move through it) were available, as functions of the species of exchangeable cation, from previous studies. Relevant b-dimensions were determined in the present study. It was found that all of these water properties were correlated with the b-dimension of the associated montmorillonite.

Our results indicate that epitaxy exists between the crystal lattices of montmorillonite and adsorbed water and that these lattices undergo mutual adjustment with each increment of water. The resulting loss of free energy causes water adsorption, i.e. swelling, to occur spontaneously. Swelling stops when no further adjustment takes place. This does not happen until the adsorbed water is several hundred angstroms thick and has achieved a preferred configuration.
Acid-Base Interactions and the Properties of Kaolinite in Non-Aqueous Media
Authors: Solomon D. H. , Murray H. H.
Published: September 2006

In non-aqueous systems, kaolinite can show, in addition to the physical interactions, considerable chemical activity. This study considers the chemical reactions that can occur at the kaolinite surface and explains these reactions in terms of acid-base interactions. In certain applications the chemical activity must be controlled if satisfactory products are to be obtained; for example, when kaolinite is used as a filler in rubber or as a diluent for insecticide powders. The concept of acid-base interactions is used to explain rheological and film properties in kaolinite-organic systems. The strength of the surface acid sites of kaolinite varies with the moisture content. At 1% moisture the surface is equivalent to 48% sulphuric acid whereas at 0% it is equivalent to 90% sulphuric acid. Therefore, the moisture level is extremely important and dry kaolinite will promote or catalyze many chemical reactions and where acid-base interactions are involved the presence of even small amounts of water usually retards or inhibits the reaction. Several examples explaining these interactions are given in the paper.
The Transformation of Lepidocrocite to Goethite
Authors: Schwertmann U. , Taylor R. M.
Published: September 2006

The conversion of lepidocrocite (-γFeOOH) to its more stable polymorph, goethite (αFeOOH) was followed by observing changes in crystal morphology, oxalate solubility, surface area and X-ray diffraction. In conjunction, kinetics were measured as functions of surface area, temperature, alkalinity and seeding with goethite crystals.

The results suggest that the transformation is not topochemical, but proceeds through the solution phase. The main steps governing the rate of transformation are, (1) the dissolution of lepidocrocite, and (2) the formation of goethite nuclei and subsequent growth. Either of these processes can be rate-determining under appropriate conditions.
The Influence of Silicate on the Transformation of Lepidocrocite to Goethite
Authors: Schwertmann U. , Taylor R. M.
Published: September 2006

The mechanism of the transformation of lepidocrocite (γFeOOH) to goethite (αFeOOH) has previously been established and the effect of silicate on the transformation was investigated. Rather than completely inhibiting the reaction, as had been suggested, the presence of Si was found to merely retard the nucleation stage of the transformation. There was found to be no decrease in the dissolution rate of the lepidocrocite due to surface adsorption of Si.

Si has no effect if introduced after the nucleation stage, and under conditions of pH and temperature where the dissolution rate of the lepidocrocite largely determines the rate of transformation, the presence of Si has a reduced effect. The results show that Si is adsorbed and incorporated into the goethite structure, and due to its retarding effect on the nucleation, larger crystals of goethite are formed, many of which are twinned.

It is inferred from the results that the apparent stability of lepidocrocite occurring in soils in association with goethite cannot be attributed solely to the presence of Si in the soil system.
Some Naturally Occurring Illite-Smectite Interstratifications
Authors: Heller-Kallai L. , Kalman Z. H.
Published: September 2006

Two different types of interstratified illite-smectite are found in a section of Paleozoic sediments in the Negev, Israel. One of these is detectable only by a decrease in peak width and a concomitant increase in symmetry of the 10 Å peak on glycolation. This material is regarded as illite, randomly interstratified with about 20 per cent expanding layers.
Recognition of Interstratified Clays
Authors: Mills J. G. , Zwarich M. A.
Published: September 2006

Difficulties in the interpretation of X-ray diffractograms of soil clays are discussed with reference to clay fractions obtained from glacial till and lacustrine soil parent materials. Diffracto-grams of the coarse clay fractions are readily interpreted by conventional means but it is difficult to determine if the dominant mineral species of the fine clay fraction is an interstratified mineral or a mixture of discrete montmorillonite and mica. A number of methods of interpretation of diffractograms of interstratified minerals are used with varying results. In the case of clays of small particle size, diffraction peaks crucial to the recognition of interstratification are not resolved due to the peak broadening. This phenomenon causes the diffractogram of a mixture of discrete minerals to resemble that of an interstratified mineral.
Interlamellar Metal Complexes in Layer Silicates III Silver(I)—Arene Complexes in Smectites
Authors: Clementz D. M. , Mortland M. M.
Published: September 2006

The complexation of benzene and several methyl substituted benzenes with exchangeable silver(I) on the interlamellar surfaces of Ag(I)-montmorillonite has been studied using spectroscopic methods. There are no physically adsorbed molecules interacting with the internal silicate surfaces and the only chemisorbed species present are those which are coordinated through π electrons to the exchangeable Ag(I) ions. In each case the coordinated species are similar to the previously studied Cu(II)-montmorillonite Type I complexes where aromaticity is retained. Complete replacement of coordinated and other interlamellar water molecules was accomplished with relative ease. Stoichiometric determinations indicate a 2:1 benzene: Ag(I) complex. Similarities between the Cu(II) and Ag(I) complexes are discussed in relation to electronic configurations.
A Sepiolite-Rich Playa Deposit in Southern Nevada
Authors: Papke Keith G.
Published: September 2006

Sepiolite is seldom reported in playa deposits, even though it is generally believed to form in a highly saline, alkaline environment. Its rareness suggests that unusual conditions are necessary for formation of sepiolite. Sepiolite is a major constituent of a near-surface playa bed 4 ft thick in the Amargosa Desert, southern Nye County, Nevada. Associated materials include dolomite and small to trace amounts of quartz, feldspar, montmorillonite, illite, and volcanic glass. The dolomite, averaging about 2μ in size, makes up about 40% of the bed. The overlying beds and the underlying ones down to a sampled depth of 13½ ft are montmorillonitic (saponite) clays with moderate to trace amounts of sepiolite; dolomite is abundant in all these clays except in the uppermost several feet, where calcite is a major constituent. Ground water in this area contains abundant magnesium compared with that in the rest of the Amargosa Desert. An initial high concentration of magnesium in the playa lake water probably promoted the development of sepiolite and dolomite. Concentration of dissolved salts through evaporation of water is believed to have started chemical precipitation of dolomite, and this precipitation and the continued evaporation later caused deposition of sepiolite.
A Ferroan Nontronite from the Red Sea Geothermal System
Authors: Bischoff James L.
Published: September 2006

A smectite rich in ferrous iron and low in aluminum occurs abundantly in the Red Sea Geothermal Deposits, and appear to be forming at present.

Chemical analyses and Mössbauer spectra indicate the mineral is intermediate in composition between nontronite and the as yet undescribed trioctahedral ferrous iron end member.
Formation of an Interstratified Mineral by Extraction of Potassium from Mica with Sodium Tetraphenylboron
Authors: Tomita Katsutoshi , Dozono Mitsuhiko
Published: September 2006

Interlayer K was extracted with sodium tetraphenylboron solution from a powdered sericite heated to the temperature of dehydroxylation and quenched to room temperature. By this procedure, sericite of the 2M1 type was changed to an interstratified mineral. The X-ray diffraction properties of this interstratified mineral are similar to “rectorite”.
The Relationship Between the Hydrated and Dehydrated States of an Halloysite
Authors: Churchman G. J. , Aldridge L. P. , Carr R. M.
Published: September 2006

A study of the mineralogical changes taking place during the loss of interlayer water in an halloysite has been carried out in order to clarify the relationship between the most hydrated and least hydrated states of the mineral. A number of samples of halloysite which together exhibit a variety of average interlayer water capacities were obtained by the conditioning of a largely hydrated sample with different atmospheres of known relative humidities. Profiles were obtained of X-ray peaks which characterize the interlayer water capacities of halloysite samples. An attempt has been made to analyse these profiles into a sum of peaks attributable to the fully hydrated and dehydrated states of the mineral. Such an analysis does not satisfactorily explain the profile shapes. A mechanism of interstratification of hydrated and dehydrated kaolin layers in which there is a tendency towards the segregation of these layer types gives a more satisfactory explanation of these profile shapes. It is concluded that dehydration takes place through an interstratification in which there is a partial segregation of the two basic layer types. This conclusion implies that halloysites with all average interlayer water contents between 0 and 2 molecules per unit cell may exist and that fully hydrated halloysite and dehydrated halloysite are the end members of a continuous series of hydration states.
A Chloritized Montmorillonite from the Rio Chiflon Formation (TR) of Argentina
Authors: Bossi Gerardo E.
Published: September 2006

X-ray, chemical, and genetic characteristics of a chloritized montmorillonite mineral species, found in The Río Chiflón Formation (La Torre, La Rioja, Argentina) are described. The mineral is associated with illite, montmorillonite, and chlorite, plus the non-clay associates analcite and hematite. The Río Chiflón Formation is of Upper Triassic age, and consists of red sandstones and siltstones representing poorly developed fluviatile cyclothems.

Studies of the Li+, K+ and Mg2+ varieties of the clay, and solvation with glycerol or ethylene glycol have shown that the mineral is a smectite which behaves peculiarly with heating. Between 200° and 600°C the mineral collapses gradually from a basal spacing of 13–10 Å. Regular expansibility with ethylene glycol and glycerol is completely preserved (in the Li+ and K+ clays) up to a preheating of 400°C and partially preserved up to 600°C. This behavior has been interpreted as caused by the presence of interlayer contaminants of a hydroxy-cation type. The interlayer cations may be Al, Mg, and Fe, (in this order).

The environment of the Río Chiflón Formation has been evaluated in the light of well-known occurrences of intergradient clays in soils, and the presence of analcite and hematite. It is proposed that chloritization has taken place during a soil weathering process, under alkaline conditions with great availability of sodium during alternating dry-humid seasonal climates (oxidation conditions). The stability of the interlayer developed under these circumstances was increased during long burial and diagenesis.
Directional Variation of Elastic Wave Velocities in Oriented Clay
Authors: Franklin Arley G. , Mattson Phillip A.
Published: September 2006

Sonic anisotropy of clay resulting from particle orientation was studied by means of velocity measurements on anisotropically consolidated kaolinite. Samples were prepared from a kaolin-water slurry under consolidation pressures ranging from 80 to 400 psi, with two distinct stress histories. Directional velocity measurements were made over a wide range of water contents as saturated samples were allowed to dry by evaporation to water contents below the shrinkage limit. Directional variation was most pronounced with partial saturation, when directional velocities differed by as much as a factor of two. The degree of sonic anisotropy is seen to correlate with variation in the shrinkage limit, showing a systematic dependence on particle orientation, but no unique relation to consolidation stress exists because of the overriding influence of stress history.
Morphological Effects on Illite as A Result of Potassium Depletion
Authors: Huff Warren D.
Published: September 2006

Several illites and a mixed-layer illite-montmorillonite developed fractures in some particles during progressive removal of interlayer potassium by solutions containing sodium tetraphenylboron. The appearance of the splinters in bundles, some connected to incompletely broken plates, suggests the process is related to the differential release of stresses known to exist as a consequence of octahedral-tetrahedral misfit. The formation of splinters produces additional surface area for ion removal and may influence the rate of vermiculite development.
The Oxidation of Octahedral Iron in Biotite
Authors: Gilkes R. J. , Young R. C. , Quirk J. P.
Published: September 2006

Oxidation of octahedral ferrous iron in biotite by saturated bromine water results in a loss of both octahedral and interlayer cations. The hydroxyl adjacent to vacant octahedral cation sites adopt an inclined orientation resulting in a more stable environment for interlayer cations. The only structural change accompanying these processes is a decrease in b-axis dimension which is linearly related to octahedral ferric iron content. These findings are in agreement with observations made on naturally weathered biotites.
Zeolite as Catalysts for the Synthesis of Amino Acids and Purines
Authors: Fripiat J. J. , Poncelet G. , Van Assche A. T. , Mayaudon J.
Published: September 2006

This paper attempts to show that the catalytic properties of zeolitic material may play a role in the synthesis of simple biological molecules from gases commonly found in extraterrestrial atmospheres. Linde X and Y molecular sieves cation-exchanged by Ca2+ and Fe3+ have been heated in the presence of carbon monoxide and ammonia. Amino-acids and u.v. absorbing substances identified by paper chromatography have been extracted from the solid. HCN, the basic molecule involved in the synthesis of those substances has been detected in the gas phase. It is proposed, on the basis of i.r. results, that the amino-acids are hydrolysis products of an undefined polymer.
Laboratory Alteration of Trioctahedral Micas
Authors: Hoda Syed N. , Hood William C.
Published: September 2006

Artificial alteration of thirty-five trioctahedral and one dioctahedral micas by solutions varying in strength from 0·001 to 1·00 molal magnesium sulfate was found to approximate a normal exchange reaction after surface effects are eliminated. The equilibrium constants for the reaction:

<mml:math xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mnf="http://cambridge.org/core/manifest" xmlns:cup="http://contentservices.cambridge.org" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://cambridge.org/core/metadata" xmlns:core="http://cambridge.org/core" xmlns:c="http://cambridge.org/core/content">1/2Mg2++K−mica=Mg1/2−mica+K+(vermiculite)$1/2 {Mg^{2+}}+K-mica=Mg_{1/2}-mica+K^+(vermiculite)$

range from 0·0001 to 0·0028 and average 0·0010 in value. X-ray diffraction study reveals that iron-rich micas tend to develop a 1:1 mixed-layer biotite-vermiculite structure in weak magnesium sulfate solutions whereas magnesium-rich biotite and phlogopite alter to vermiculite. Mica composition also influences the degree of alteration of mica to vermiculite. High fluorine and octahedral multivalent cation contents tend to retard the reaction whereas high magnesium content and perhaps high calcium contents tend to favor the alteration. The equilibrium constant data indicate that vermiculite and hydrobiotite are more stable than trioctahedral micas in most weathering environments.
Chlorite Examination by Ultramicrotomy and High Resolution Electron Microscopy
Authors: Brown J. L. , Jackson M. L.
Published: September 2006

Mafic chlorite from Benton, Arkansas was comminuted by rotary blending of a suspension, and the — 2 μm fraction separated by sedimentation in H2O. Droplets of suspension of the < 2 μm fraction were dried on a layer of Epoxy resin and then additional Epoxy was added and heat-cured at 48°C to form a resin sandwich. Cross-sections of 600–900 Å thickness were cut on a Reichert automated ultramicrotome. The sections were collected on standard electron microscope specimen screens, reinforced by vacuum evaporated C and examined by transmission electron microscopy (TEM). The Phillips EM 200 electron microscope was equipped with a “microgun” source to minimize heating of the specimen and to improve contrast and high resolution (HREM). Images of the (001) chlorite crystallographic planes spaced at 13·9Å intervals were visible on many of the particle sections. Imaging of the planes depended upon their being nearly parallel to the electron beam (within 0° 10’) and therefore, many particles which had other orientations did not show the 13·9Å image. Micrographs made before appreciable irradiation by the electron beam revealed images of fringes corresponding to the 7·22Å (002) spacing of chlorite. Loss of the 7·22 Å fringes and reinforcement of those at 13·9 A resulted from heating of the chlorite in the electron beam. This behavior is analogous to the well-known crystallographic effects of heating chlorite at 550–760°C.
The Effect of Cation Exchange of Tris(Ethylenediamine)Cobalt (III) for Sodium on Nitrogen Sorption by Montmorillonite
Authors: Knudson M. I. , McAtee J. L.
Published: September 2006

The cation exchange process between tris(ethylenediamine)cobalt(III) and Na+ on mont-morillonite was studied by atomic absorption spectrophotometry, X-ray diffraction, differential thermal analysis, and nitrogen sorption at 78°K. The exchange of Co(en)33+ for Na+ was found to be extremely favorable, with a tendency toward segregation of the two kinds of cations in the mixed clays studied. Small amounts of Co(en)3+3 were found to lower the nitrogen sorption capacity of Na+ mont-morillonite while clays with high Co(en)3+3 content had greatly enhanced sorption. An explanation is offered in terms of a dual role of the Co(en)3+3 in determining the kind and amount of nitrogen sorption in the exchanged montmorillonite.
The Nature of Garnierites — II Electron-Optical Study
Authors: Uyeda Natsu , Hang Pham Thi , Brindley G. W.
Published: September 2006

Electron micrographs of 7 Å-type and 10 Å-type garnierites have been recorded at 5·104–105X magnifications to show the morphological character of these minerals, and at 106X magnification to show structural features of the particles. The 7 Å, serpentine-like minerals show a greater variety of morphological forms including tube- and rod-shaped particles and also platy forms and poorly defined, fluffy particles, probably aggregates. The 10 Å, talc-like minerals show mainly platy forms and fluffy aggregates, and generally very few tube or rod-shaped particles. At 106X magnifications, the 7 and 10 Å layer spacings are seen directly. In the samples examined, the 7 Å spacings are more clearly and more regularly defined than the 10 Å spacings.