bluuebunny/crossref_metadata_2025 huggingface dataset:
Children's Story Retelling and Comprehension Using a New Narrative Resource
Authors: John Shonna Francis , Lui Mariko , Tannock Rosemary
Published: December 2006

This study used the Strong Narrative Assessment Procedure (SNAP) to examine story retelling in children. The skills assessed include story grammar, comprehension, story length, and retelling errors. The 6i participants (grade 2-6) we.re randomly assigned to one of three stories that were then seen and heard. Each child. responded. to lo comprehension questions after retelling the story. Analysis of the transcripts revealed an age effect in retelling Internal Responses, and an age-related trend in reporting Attempts. As well, girls outperformed boys when answering inferential comprehension questions. Importantly, the results show that the SNAP stimulus stories are not equivalent, thus limiting their usefulness for test-retest purposes. These results support expected age differences in story structure as well as the relatively stronger verbal working memory in girls. Issues that relate to the use of the SNAP for assessing children's narrative skills are discussed.
A Combined Phonotogical Awareness, Whole Language, and Metacognitive Approach to Teach Reading to Reading Resistors
Authors: McKenna Gregory S. , VioLato Claudio
Published: December 2006

In the present study we investigated the effectiveness of a reading remediation program for reading disabled (RD) students that was based on phonological awareness, as well as incorporating aspects of whole language and netacognitive instruction. Participants consisted primarily of treatment resistant RD students (N = 68; age range: 6-17 years) with a mean age Of 11.3 years, referred to a reading clinic at a school dedicated to working with children with learning disabilities. Pre/post intervention measures were analyzed by repeated measures multivariate analyzed of variance (MANONVA). Results (Wilk's Lambda = .33, F(7,49) = 14.16, p< .ooi) indicated students' phonological awareness, reading comprehension and, to a lessor extent, spelling had improved post intervention (Cohen's d ranged from .14 to .82). The results are discussed in relation to current research on remedial reading programs and reading treatment resistors.
Twelve-Year Review of In Vivo Exposure: Treating Specific Phobias in Children
Authors: MacPhee Angela R. , Andrews Jac J.W.
Published: December 2006

This article reviews 15 studies using in vivo exposure to treat specific phobias in children. Six elements of research methods are considered: (a) participants clinically diagnosed; (b) subjective, behavioral, and physiological components of the fear reaction measured; (c) research design; (d) inclusion of a control group; (e) follow-up data collected; and, (f) necessity of including other treatments with in vivo exposure. The studies were obtained through a computerized search of PsycINFO and CISTI This investigation revealed that all six elements of research mc-,ethods examined inthis reiew are in need of improvement. Suggestions for future research in this area are provided.
Criminality Among Female Drug Users Following an HIV Risk-Reduction Intervention
Authors: Theall Katherine P. , Elifson Kirk W. , Sterk Claire E. , Stewart Eric A.
Published: December 2006

The main objectives of this article are to determine the prevalence of criminality among a sample of female African American drug users and to examine change in criminality over time, including the correlates associated with this change. Data were collected from 336 adult women who participated in an HIV risk-reduction intervention focused on the context of the women's daily life. Face-to-face structured interviews were conducted at baseline, prior to enrolling in the intervention, and at follow-up, 6 months after completion of the intervention. Bivariate and correlated multivariate methods were utilized to examine changes in criminality and other behaviors over time. Both violent and nonviolent criminality declined significantly between baseline and follow-up assessments. Of the correlates considered, drug-using characteristics and victimization played the greatest role in explaining the decrease in criminality. Low self-control and depressive symptoms also contributed to the reduction in criminality. The findings suggest the importance of considering individual characteristics that may influence the women's criminal behavior as well as the impact of their routine activities.
Identifying Pregnant Women Experiencing Domestic Violence in an Urban Emergency Department
Authors: Datner Elizabeth M. , Wiebe Douglas J. , Brensinger Colleen M. , Nelson Deborah B.
Published: December 2006

The article describes characteristics of pregnant women presenting to the Emergency Department (ED) who are experiencing current violence and presented a screening tool to identify pregnant women experiencing violence. Women completed an in-person interview regarding violence, sociodemo-graphic factors, health status, and drug use. Fifteen percent of women reported at least one episode of violence during the pregnancy. Young age (OR = 3.37, 95% CI: 1.79-6.36), current alcohol use (OR = 1.53, 95% CI: 1.06-2.19), current marijuana use (OR = 1.96, 95% CI: 1.32-2.92), less than a high school education (OR = 1.46, 95% CI: 1.01-2.12), and a prior diagnosis of trichomonas (OR = 1.81, 95% CI: 1.20-2.72) were significantly related to experiencing current violence. Screening patients using these five characteristics identified 8 out of 10 women reporting violence (sensitivity = 75.6%). These results identify a set of predictors that may be helpful in identifying pregnant women who are experiencing current domestic violence.
Benthic biofacies to interpret Holocene environmental changes and human impact in Alexandria's Eastern Harbour, Egypt
Authors: Bernasconi Maria Pia , Melis Romana , Stanley Jean-Daniel
Published: December 2006

Holocene molluscan and foraminiferal faunas, sensitive ecological markers, are statistically treated to define their temporal and spatial distributions in radiocarbon-dated cores in Alexandria's Eastern Harbour. Up-core variations of these benthic biofacies record the evolution of depositional environments during the past 8000 years in this long-occupied Eastern Mediterranean port. The most important change occurred in the mid-Holocene between 6300 and 4300 yr ago, a time of lower sea level and minimal human activity. This faunal change, indicating a transition from a somewhat protected to a more open and higher-energy marine environment, resulted primarily from rise of sea level, lowering of the harbour floor and diminished shielding by Pleistocene coastal ridges and reefs near the bay mouth and within the harbour. Since that time, faunal assemblages have remained generally constant, except during the period from 2100 to 1800 yr ago when Greeks and Romans built the Heptastadion that connected Alexandria to Pharos Island; this construction effectively separated the Eastern from the Western Harbour. Absence of a well-marked faunal change during the past 18 centuries is unexpected, particularly in light of the much-increased population and associated human effects. The harbour's overall large size, rise in relative sea level and continued exchange of marine water between the open shelf and port have maintained an active circulation pattern. The strong current regime and reworking of bottom sediments have generally masked short-term human effects and altered the harbour's late-Holocene sediment stratigraphy. These factors help explain why benthic biofacies primarily record influences of natural processes that prevailed in this relatively unconfined, high-energy marine setting rather than those of a more constricted and anthropogenically impacted port.
Flexural Vibration of Rotating Cracked Timoshenko Beam
Authors: Al-Said Samer Masoud , Naji Malak , Al-Shukry Adnan A.
Published: December 2006

In this study, a simple model is proposed that describes the flexural vibration characteristics of a rotating cracked Timoshenko beam. The cracked beam is modeled using two uniform segments connected by a massless torsional spring at the crack location. The equation of motion is derived using Lagrange’s method in conjunction with the assumed mode method. The proposed model is used to study the effect of crack depth, shear deformation, and rotation speed on the dynamic characteristics of the beam, and compare the results with those obtained from the widely used Euler-Bernoullibeammodel. Itisshownthatforthe same crack depth the proposed model has a higher reduction in frequency compared to that of Euler-Bernoulli beam. Model verification is carried out using three dimensional finite element analysis, which reveals good agreement with the assumed mode results.
Variable Structure Control with Adaptive Fuzzy Sliding Surface
Authors: Sadati N. , Talasaz A.
Published: December 2006

An adaptive fuzzy sliding mode control scheme is presented in this article. Despite the advantages of sliding mode control design for uncertain dynamic systems, classical sliding mode control has a major problem in the form of chattering, produced by the rapid switching used to conduct the state trajectories toward the sliding surfaces. A variety of methods are used to achieve chattering-free motion by smoothing out the switching functions; a fuzzy method is introduced in this article. In the proposed approach, the switching functions are replaced by adaptive fuzzy control signals such that the Lyapunov stability conditions are satisfied. This adaptive fuzzy controller can improve the performance and also eliminate the high frequency chattering in the control signals by preventing the application of large control gains where these are unnecessary, especially when the state trajectories are close to the sliding surfaces. The proposed approach and the classical sliding mode control are both applied to a flexible transmission system and comparisons between these control schemes are shown using simulations. The results confirm that the proposed adaptive fuzzy sliding mode control scheme is a powerful tool for the elimination of chattering and for obtaining smooth control signals for applying to the system.
The Work of Elderly Men Caregivers
Authors: Russell Richard
Published: December 2006

Approximately 1,000,000men currently care for spouses with cognitive impairment after leaving market-economy careers through normative or early retirement. In the process, they made the difficult transition from work in the public arena to the private, largely invisible world of family care. This article explores how elderly men caregivers adapt to such drastic changes in social location, what resources they call upon to ameliorate the impact of those changes, and what we can learn from their experiences that will inform future research and practice. Data are from a qualitative study of thirty elderly men care-givers in Rochester, New York. Two major themes emerged, demonstrating both struggle and success. The most significant struggle was coping with the isolation of home care; by contrast, many men were able to successfully make the transition through the use of a style of caregiving that incorporated a combination of management and nurturing skills.
Buying Sex
Authors: Peng Yen-Wen
Published: December 2006

In this article, I attempt to deepen feminists’ understanding of the power dynamics in the practice of client-prostitute relations by exploring how clients (in Mandarin, Piao-ke) make sense of their relationships with prostitutes. On the basis of tens of online and in-person interviews with Taiwanese Piao-ke, I explore the diverse and subtle details that surface in the clients’ narratives and that might otherwise have been neglected. Instead of totalizing Piao-ke as problematic, I suggest a postmodernist feminist understanding of the practice, namely, one founded on a distinction between acceptable from dominant practices and discourses that should be targeted.
Raymond Prince and the R. M. Bucke Memorial Society for the Study of Religious Experience
Authors: Bartocci Goffredo , Rovera Giovanni Giacomo , Lalli Nicola , Ascoli Micol
Published: December 2006

The study of the relationship between psychiatry and religion has become an issue of increasing importance for both research and clinical practice. This article presents the history of the R. M. Bucke Memorial Society for the Study of Religious Experience, established by Raymond Prince in Montréal in 1964 as one of the first scientific societies whose aim was to investigate those characteristics of religious experience of interest to psychiatry. It also describes some of Prince’s own studies on religious experience.
Shafts for daylighting underground spaces: sizing guidelines
Authors: Gugliermetti F , Grignaffini S
Published: December 2006

This paper presents an experimental study on Daylight Factors (DFs) distribution in underground multi-level open spaces which use continuous light shafts to reduce energy consumption by the artificial lighting system and to improve the human acceptability of the spaces. Experimental measurements were carried out in a scale model, which could be assembled to provide different shapes and could be placed in an unobstructed site. The use of a real sky, which very seldom shows a fully overcast CIE luminance distribution, required the development of a special procedure to guarantee the accuracy of the experimental results. Level height, slab floor thickness, aspect ratio and glass covering of the light shaft were some of the parameters considered. Measured DFs were correlated by dimensionless parameters and reported in the form of charts which can be used to size the width of the shafts on the basis of the required illuminance and on the frequency distribution of the diffuse natural illuminance. An example of DFs calculation for an underground space is also reported.
A comparative study of the morphology, chemical composition and weathering of rhyolitic and andesitic glass
Authors: Kirkman J. H. , McHardy W. J.
Published: December 2006

The morphology of volcanic glass particles in rhyolitic and andesitic tephra of central North Island and Taranaki areas of New Zealand has been studied by scanning electron microscopy. Electron probe analyses of the glasses are compared with those of the clays to which they weather. Loss of silica characterizes the weathering of both glasses. The rapid rate of weathering of andesitic glass is attributed to its occurrence as fine, soft microlites and extensive substitution of Al for Si in the structure. Rhyolitic glass weathers more slowly because it occurs as hard and brittle particles containing relatively little alumina. It is suggested that the structure, chemical composition and chemical activity of allophane is governed largely by the chemical composition and bonding characteristics of the parent glass.
Quantitative determination of the interlamellar volume in an interstratified mica-smectite soil clay
Authors: Jones A. A. , Greenland D. J.
Published: December 2006

Two well-characterized soils containing substantial amounts of interstratified mica-smectite have been examined by a combination of techniques in an attempt to correlate the characteristics of the interlamellar surfaces with other properties. The techniques used included XRD and chemical analyses, determination of surface area by nitrogen sorption and by desorption of water and ethylene glycol monoethyl ether vapour, and determination of cation exchange capacity. Reasonable agreement was found between the results obtained for the proportion of expanding or smectite-like surfaces, although estimates by XRD, especially when coarser material (> 2/µm) was included, were generally lower than those obtained by the other methods. The mean density of charge on the surfaces of the soil clays appeared to be similar to that of smectite. The decrease in porosity observed for both soils dried by the critical point method was largely accounted for by the decrease in volume associated with the loss of interlamellar water from the smectite-like interlamellar surfaces included within the clay fraction.
Structure de l'espace interlamellaire des vermiculites Ba monocouches
Authors: Alcover J. F. , Gatineau L.
Published: December 2006

L'interprétation des diffusions en dehors des taches de Bragg dans une vermiculite saturée par du baryum (d001 = 12·20 Å) permet de préciser l'organisation de l'espace interlamellaire. Le motif élémentaire est constitué par un groupement Ba-6 H2O où le baryum est engagé dans une cavité ditrigonale et les 6 molécules d'eau sont dans le plan médian, l'ensemble forme une pyramide très aplatie de base hexagonale. La répartition de ces motifs est bipériodique avec une maille 2 a,b centrée en projection. Cette organisation se développe dans des domaines identiques, orientés à 120° les uns des autres.
Clay mineral diagenesis in two East African lake sediments
Authors: Singer A. , Stoffers P.
Published: December 2006

The vertical clay mineral distribution pattern in two sediment cores taken from two East African lakes has been studied in detail. In the core from Lake Albert (Mobutu Sese Seko) a clay assemblage consisting principally of smectite with some illite and kaolinite in the uppermost segment of the core changed with depth into first a mixed-layer illite-smectite dominated clay and then at 6·60 m into an iltite dominated clay. Lower in the core there was again a transition towards interlayer mixtures, and in the bottom segment towards smectite. These changes are interpreted as a diagenetic transformation of smectite into illite, effected by saline palaeo-lake water with an unusually high K/Na ratio. Three smectite→illite-smectite→illite transition cycles were recognized in a 56 m deep sediment core from Lake Manyara. The sections in which illite dominated contained silt-sized analcime, while those with interlayer mixtures contained alkaline zeolites. The diagenetic illitization of smectite appeared to parallel the process of analcime formation, the K necessary for illitization being released during K,Na-zeolite→analcime transformation. These occurrences suggest that high temperature and pressure may not constitute absolute prerequisites for the diagenetic illitization of smectite.
The application of electron spin resonance spectroscopy to studies of clay minerals: I. Isomorphous substitutions and external surface properties
Authors: Hall Peter L.
Published: December 2006

Electron spin resonance (ESR) spectroscopy has contributed significantly to the identification and characterization of paramagnetic impurities associated with clays. Following a brief discussion of the general principles of the technique, a review is given of the application of ESR to the study of those paramagnetic species (chiefly iron and radiation-induced lattice defects) located either within the aluminosilicate structure or present as an external impurity phase.
Effect of thermal treatment on lanthanide montmorillonites: dehydration
Authors: Mozas T. , Bruque S. , Rodriguez A.
Published: December 2006

Hydration/dehydration behaviour and the effect of various thermal treatments on montmorillonites saturated with lanthanide ions have been investigated by X-ray diffraction, thermal analysis (DTA, TG, DTG), IR spectroscopy and sorption-desorption of water vapour techniques. Heating at 150°C under 10−5 torr did not eliminate all the interlayer water of the montmorillonite, neither did it affect the CEC. Heating above 160°C caused a reduction in CEC. At 25°C La-montmorillonite takes up a maximum of three water layers in the interlayer space, the water molecules adopting a nonacoordinated distribution around the La3+ cation.
Alteration of imogolite by dry grinding
Authors: Henmi Teruo , Yoshinaga Naganori
Published: December 2006

The effects of dry grinding on the structure, morphology and properties of imogolite have been investigated by means of X-ray powder diffraction analysis, IR, DTA, and measurements of CEC and specific surface area. Imogolite is very susceptible to alteration by grinding compared to layer silicate minerals such as halloysite, kaolinite and montmorillonite. In the earlier stages of grinding, the parallel array of imogolite tubular structure units is markedly disturbed. On further grinding, disruption of Si-O-Al linkages, polymerization of the silica component released and loss of structural OH groups proceed simultaneously, these changes eventually resulting in complete breakdown of the structure. Ground imogolite is reaggregated finally into granular particles of irregular shape. All these changes are associated with a decrease in water holding capacity, CEC and specific surface area.
X-ray identification of randomly interstratified illite-smectite in mixtures with discrete illite
Authors: Środoń Jan
Published: December 2006

Proportions of the component layers in randomly interstratified illite-smectites can be determined precisely in the presence of discrete illite if two reflections (at 15–16 and 31–32°2θ Cu Kα) are strong enough to be measured accurately. The method takes into account the variable thickness of the smectite-ethylene glycol complex and involves a correction for the interference from illite reflections.
A mineralogical and geochemical study of turbidite sandstones and interbedded shales, Mam Tor, Derbyshire, UK
Authors: Spears D.A. , Amin M.A.
Published: December 2006

Eleven shales and fourteen turbidite sandstones from the Mam Tor Beds were analysed chemically and by XRD. The ratio of kaolinite to illite plus mixed-layer clay was higher in the sandstones than in the shales, size fractions demonstrating that this ratio decreased as the grain size decreased. Shales more basinal in character than those of the Mam Tor Beds contain more illite and mixed-layer clay and less kaolinite and it is suggested that there was a lateral variation in clay mineralogy with distance from the shore line due to particle size sorting and that the character of the clay mineral fraction was retained as the turbidity current transported sediment from a nearshore environment deeper into the basin. Support for this model was obtained from the geochemistry which showed that the sandstone matrix differed compositionally from the shales. Systematic variations occurred in the turbidite sandstones but not in the shales which are therefore considered to be non-turbiditic. Only minor mineralogical changes appear to have occurred during diagenesis.
Clay mineral diagenesis in Rotliegend aeolian sandstones of the southern North Sea
Authors: Rossel N. C.
Published: December 2006

The distribution of diagenetically-formed clay minerals in Rotliegend dune sandstones of the Southern North Sea Basin is closely related to the following factors: (i) the petrography of the sandstones, (ii) the paleoburial depth and tectonic setting of the area, (iii) the thickness of gas-generating Carboniferous strata underlying the Rotliegendes, and (iv) the facies distribution of the overlying Zechstein. The diagenetic clay minerals are mainly conversion products of feldspars and, to a lesser extent, of detrital clays and micaceous lithic fragments. Sandstones containing dominant drusy illitic and chloritic clay minerals have been buried to depths > 3000 m; if kaolinite is the dominant clay mineral, burial depths were less. Sandstones containing feldspars (detrital and authigenic) up to approximately 7% of bulk volume have permeabilities that are about four times higher than sandstones with similar amounts of kaolinite, and as much as 200 times higher than sandstones with similar amounts of illite and/or chlorite.
Surface-charge determination of crocidolite particles in suspension
Authors: Isherwood R. , Jennings B. R.
Published: December 2006

The translatory and rotatory diffusion coefficients, electrophoretic mobility, permanent dipole moment, electrical polarizability and optical anisotropy factor for a crocidolite sol have all been measured in a single optical apparatus. Electrophoretic light-scattering and electrically-induced birefringence were the methods used, these being rapid and well-suited to particles in the micron and sub-micron size-range, where conventional electrophoresis is difficult. Electric birefringence offers a fast means of sizing mineral particles in suspension and the electrical polarizability and electrophoretic mobility have a common origin in such sols. This is discussed in terms of the surface-charge and electric double-layer characteristics of the particles.
Reaction products of organic dye molecules with acid-treated montmorillonite
Authors: Fahn R. , Fenderl K.
Published: December 2006

During the reaction of solutions of the leuco dyes crystal violet lactone and N-benzoyl leuco methylene blue with acid-treated montmarillonite (as occurs with carbonless copying papers), most of the offered dye is intercalated within the interlayers of the montmorillonite structure remaining after acid attack. This phenomenon was demonstrated by XRD and also by high-resolution transmission electron microscopy. During acid treatment, octahedral cations are dissolved from exposed edges of the montmorillonite lamellae and amorphous silica builds up in these areas. As a result, the BET(N2) specific surface area increases from ∼60 m2/g to ∼300 m2/g and, consequently, the theoretical reactivity towards leuco dyes. Nevertheless, only small quantities of the dye molecules are adsorbed onto the amorphous silica. The excellent colour intensity and, in particular, the resistance to fading in the light of the montmorillonite dye complexes may be explained by the protected position of the dye molecules within the interlayers of the montmorillonite.
Iron substitution in aluminosilicate sols synthesized at low pH
Authors: McBride M. B. , Farmer V. C. , Russell J. D. , Tait J. M. , Goodman B. A.
Published: December 2006

The procedure for synthesizing proto-imogolite (an acid-soluble hydroxy-aluminium orthosilicate complex) and imogolite (a tubular aluminosilicate mineral) was used to produce ferruginous aluminosilicates over a range of Al/Fe ratios to determine whether Fe3+ can be incorporated in the imogolite structure. Analysis of the synthesized products by transmission electron microscopy, electron diffraction, and IR spectroscopy indicated that, while imogolite was formed in the presence of iron, increased Fe3+ in the systems caused the formation of ferrihydrite and poorly-organized aluminosilicates resembling proto-imogolite allophane. Treatment of these materials with Na-citrate/dithionite/bicarbonate dissolved the ferrihydrite and poorly-organized aluminosilicate, and concentrated products with tubular morphology. Analysis of the structural Fe3+ by ESR spectroscopy suggested that little or no Fe3+ was incorporated in the structure of imogolite, although the less crystalline proto-imogolite allophane may have accommodated some structural Fe3+. A separate iron-rich product, identified as ferrihydrite, was formed at low Al/Fe ratios. Mössbauer spectroscopic analysis of 57Fe3+ doped at very low levels into proto-imogolite and imogolite indicated that the sites of substitution were better defined in the latter. At least part of this Fe3+ may have been incorporated in the structure of boehmite, an impurity formed during synthesis.
The influence of aluminium on iron oxides: IX. Dissolution of Al-goethites in 6 M HCl
Authors: Schwertmann U.
Published: December 2006

The rate of dissolution of synthetic Al-goethites with 0–10 mole% Al in 6 m HCl at 24°C decreases markedly with increasing extent of Al substitution. Most of the dissolution-time curves are S-shaped, suggesting some increase in surface area during the initial stages of dissolution. Based on electron microscopic examination, the increase in surface area is explained by preferential dissolution of less ordered ‘interdomainic’ zones and the consequent production of isolated ‘domains’. Thin sections of crystals provided some support for defect zones oriented parallel to the crystallographic c-direction. Stepwise multiple correlation analysis employing various properties of the goethites was used to investigate the large variation in half-dissolution time (1–96 h). 94% of the variation could be explained by the variation of the mean crystallite dimension perpendicular to the planes (110) and (111) (MCD110, MCD111). Inclusion of Al-substitution increased R2 to only 97%. As shown in a separate experiment, increasing Al concentration in the system retarded crystal growth. It is therefore believed that Al affects the dissolution rate of goethites not directly, but indirectly, by influencing crystal growth rate which, in turn, affects crystal size and order as measured by MCD110 and MCD111.
Weathering products of andesitic rocks from Sulawesi, Indonesia
Authors: Müller H. W. , Riedmüller G. , Schwaighofer B.
Published: December 2006

Mineralogical investigations of weathered andesitic bedrock and overburden on the valley flank of the Tondano river, Manado, Sulawesi, indicated that these had been subjected to different weathering conditions. The underlying andesite was completely altered to 7Å-halloysite and allophane. In the transported latosols of the overburden, 10Å- and 7Å-halloysites were found. The ratio of 10Å- to 7Å-halloysite increased linearly with depth in the profile. It is considered that weathering of the andesitic bedrock reflects a palaeoclimate with more strongly pronounced seasonal desiccation and lower annual rainfall. Neoformations by weathering of the overburden took place under the recent tropical climate.
The Mössbauer spectra of hydroxycarbonate green rusts
Authors: Murad E. , Taylor R. M.
Published: December 2006

Mössbauer spectra of Fe2+Fe3+ and Fe2+Al hydroxycarbonates taken in the paramagnetic state were fitted using two Fe2+ and Fe3+ doublets each. These spectra can be interpreted in terms of an ordered cation arrangement in the pyroaurite-type structure. The inner Fe2+ doublet seems to be the outcome of excess Fe3+ in the samples studied. The outer Fe2+ doublet (quadrupole splitting ∼2·8 mm s−1, FWHM = 0·26 mm s−1) is relatively well-defined and can, together with the fact that this doublet disappears on oxidation, possibly serve to identify these compounds in natural systems.
Fibrous silica gel obtained from sepiolite by HCl attack
Authors: Gozález L. , Ibarra L. M. , Rodríguez A. , Moya J. S. , Valle F. J.
Published: December 2006

Sepiolite is an Mg-silicate with fibrous morphology. Its structure consists of talc-like ribbons parallel to the fibre axis. Although the tetrahedral sheets are continuous, the apices in adjacent ribbons point in opposite directions, each ribbon alternating with an open channel along the fibre axis. Tetrahedral positions are normally filled with Si atoms. The width of the ribbons corresponds to eight octahedral positions, which are, normally occupied by Mg atoms, and the channel cross-section is 3·8 x 9·4 Å. This structure gives the mineral a high adsorptive capacity and molecular sieve capability. The ideal mineralogical formula is (OH2)4(OH)4Mg8Si12O30.8H2O (Brauner & Preisinger, 1956).

Activation of sepiolite by acid attack has been extensively studied (Fernández-Alvarez, 1972; Jiménez-López et al., 1978; Rodríguez-Reinoso et al., 1981). This note describes the changes undergone by sepiolite during dissolution of the octahedral Mg-sheet by HCl attack, silica gel being the end-product. This process was followed by IR spectroscopy, study of Mg-extraction kinetics, and morphological observations by SEM and TEM.
Ferrihydrite in pyrophosphate extracts of podzol B horizons
Authors: Kassim J. K. , Gafoor S. N. , Adams W. A.
Published: December 2006

The amount of Fe and Al extracted from soil by 0·1 M pyrophosphate (Fep, Alp) has long been used as a criterion in the designation of spodic horizons of podzols (Avery, 1973). Although Adamset al.(1980) showed that in a group of podzolic soils developed from Lower Palaeozoic sedimentary (LPS) rocks Fepwas very closely correlated with the quantities of Fe eluviated and illuviated, such evidence validating the use of pyrophosphate is not generally available. Recently there has been renewed interest in the identification of forms of Fe and Al extracted by pyrophosphate in order that greater confidence might be gained in the use of Fepand Alpin soil classification (McKeague & Schuppli, 1982).

Our interest in pyrophosphate extraction was stimulated when Nto (1981) discovered that Fepwas an excellent predictor of P sorption in soils developed from LPS rocks. Indeed, the level of predictability was not improved by the inclusion, in multiple regressions, of either Fe or Al extracted by any other of the commonly used selective extractants.
The adsorption of quadrivalent cerium by kaolinite
Authors: Laufer F. , Yariv S. , Steinberg M.
Published: December 2006

The adsorption of cerium(IV) by both natural and Na-exchanged kaolinite from aqueous solutions of ceric ammonium nitrate was studied in equilibrium systems. Cerium may be adsorbed either as a monomeric species or as a polymeric hydroxy cation. The species adsorbed depends on the concentration of cerium in the stock solution, the age of this solution prior to the preparation of the equilibrium system and on the equilibration period. Adsorbed cations undergo polymerization on the surface of the kaolinite; the resulting polymeric species forms strong bonds with the clay surface—it is not desorbed by sulphuric acid—and may be considered fixed. Adsorption of cerium reaches a maximum in solutions containing 0·15 M sulphuric acid.
Influence de la lyophilisation sur la structure d'une argile sensible du Québec
Authors: Delage P. , Pellerin F. M.
Published: December 2006

Resume

L' étude de la structure d' une argile sensible du Québec est abordée en porosimétrie au mercure après lyophilisation et en microscopie électronique à balayage sur une surface obtenue par fracture de l' échantillon congelé (système Cryoscan). On observe une structure en agrégats définissant deux classes de pores. A grande vitesse de congélation, la cristallisation de la glace semble surtout affecter les points faibles de la structure, qui sont les ponts de plaquettes reliant les agrégats les uns aux autres.
Relation entre surface specifique taille et morphologie des particules: applications a la kaolinite
Authors: Cambier P.
Published: December 2006

Resume

La relation entre la surface développée par les particules d'une poudre et leur paramètre de taille et de morphologie est abordée de façon théorique, rigoureuse et générale. A l'aide d'un nouveau choix des grandeurs mesurées, il est possible de ne prendre en compte qu'une seule distribution statistique, de l'un des paramètres, les autres paramètres n'apparaissant dans la formulation qu'à travers leurs moyennes arithmétiques. Dans le cas de plaquettes, le problème est analysé de façon théorique et expérimentale. La formulation est encore simplifiée et on voit que la formule la plus simple consistant à négliger surfaces latérales et distribution de taille est finalement parmi les meilleures, les deux approximations se compensant.
Transformation of an aluminosilicate gel into pre-kaolinitic and pre-zeolite structures: effects of the solution media
Authors: De Kimpe C. R. , Kodama H.
Published: December 2006

Rodrique et al. (1972) reported that kaolinite was formed at 200°C from gels with an A12O3/(A12O3 + SiO2) weight ratio ⩽0·315 and pH values ranging from 4·8 to 5·8. At this temperature and using a gel with an A12O3/(A12O3 + SiO2) weight ratio >0.315, boehmite and pseudoboehmite, were obtained at pH values of up to 5·8. The latter minerals were also observed in the products formed under similar conditions at 175°C.

Unlike the situation under acidic conditions, where gel composition is important, the gel/solution ratio becomes critical under alkaline conditions. When the gel/solution ratio is low, zeolites are produced from a gel with a weight ratio between 0·3 and 0·5 in the presence of NaOH at 130-170°C (De Kimpe, 1976). When the gel/solution ratio is high, kaolinite instead of zeolites is formed under similar conditions (De Kimpe, 1969, 1976). For an intermediate gel/solution ratio, smectite is produced from a gel with a weight ratio of 0.4 in the presence of NaOH at 175°C In the presence of KOH, however, kaolinite is the only crystalline product formed under similar pH and temperature conditions (De Kimpe et al., 1981).
Early carbonate diagenesis within Phanerozoic shales and sandstones of the NW European Shelf
Authors: Gluyas J. G.
Published: December 2006

Continuous nodular limestone beds in north-west European shale sequences developed during early diagenesis via anaerobic, bacterial catabolysis of organic matter which yielded both carbonate and sulphide. The high carbonate content of the nodular limestones (50–90%) demonstrates that they developed in the upper tens of metres of the sediment column. In addition, each of the nodular limestones displays a centrifugal decrease in carbonate, indicating that growth was synchronous with compaction of the host ooze. The chemistry of the carbonate changed with time, becoming more rich in magnesium and iron and reflecting a progressive change in the porewater chemistry from its initially marine composition. The earliest precipitate was calcite containing < 1 mole% MgO; later precipitates contained several percent MgO and ultimately dolomite was precipitated. Similarly, iron content of the carbonate increased as precipitation continued and sulphate reduction, and thus pyrite production, declined. The early diagenetic cementation of many marine sandstones followed a pattern similar to that of nodular limestones and much of the carbonate was also derived from organic matter via bacterial oxidation. Thus, early diagenetic bacterial oxidation of organic matter may not only reduce the source potential of shales but also reduce the reservoir potential of associated sandstones, or those more distant which lie along compactional-fluid pathways.
Diagenesis, porosity and permeability in the Corallian Beds (Upper Oxfordian) from the Harwell Research Site, South Oxfordshire, UK
Authors: Milodowski A. E. , Wilmot R. D.
Published: December 2006

The Corallian Beds beneath the Harwell Research Site, south Oxfordshire, are a highly variable sequence of sandstones, mudstones and limestones. The more permeable lithologies of the upper part of the sequence constitute an important local aquifer. Diagenetic and post-lithification processes have strongly influenced the porosity, permeability and mineralogy of the aquifer rocks. Calcite cementation reduced the porosity and permeability of the sandstones and limestones in the upper part of the aquifer. Cementation occurred in at least three stages ranging from early diagenesis to post-compactional diagenesis. Late-stage dissolution of calcite took place along fractures and bedding discontinuities, restoring the porosity and permeability of these sediments and developing secondary porosity and permeability where original clastic carbonate was removed. Invasion of the Corallian porewaters by waters charged with CO2 is postulated as a mechanism by which calcite was removed. At the base of the aquifer, early diagenetic dissolution of biogenic silica created a high secondary porosity. Silica was reprecipitated in the dissolution voids and matrix as opal-CT. Authigenic smectite and zeolites are also associated with opal-CT. These phases are believed to have precipitated from pore-waters rich in ions derived from the alteration of volcanogenic detritus associated with the Corallian sediments.
Diagenetic influences on reservoir properties of the Sherwood Sandstone (Triassic) in the Marchwood geothermal borehole, Southampton, UK
Authors: Knox R. W. O'B. , Burgess W. G. , Wilson K. S. , Bath A. H.
Published: December 2006

Petrological studies of the Sherwood Sandstone of the Marchwood Borehole show that the formation is made up of two units of differing primary lithological character: a lower unit with lithic sandstone and conglomerate, and an upper unit with arkosic sandstone. A combination of compaction and calcite cementation (early and late) has severely reduced porosity and permeability in the lower unit. In the upper unit compaction is again important, but several beds have largely escaped cementation, and their primary porosity has been enhanced by leaching of feldspars. The secondary porosity reaches 7% in some samples. Oxygen and carbon isotope data for the early (calcrete) cements indicate isotopic equilibrium with typical freshwater compositions. The later cements yield more variable values, indicating precipitation under a wider range of conditions.
Authigenic chlorites: problems with chemical analysis and structural formula calculations
Authors: Curtis C. D. , Ireland B. J. , Whiteman J. A. , Mulvaney R. , Whittle C. K.
Published: December 2006

Analytical transmission electron microscopy was applied to some authigenic chlorites occurring as grain coatings in sandstones. Compositional variation proved to be relatively slight: all were magnesian chamosites. The coating chlorites were often intimately mixed with extremely fine-grained (0·01–0·2 µm) hematite but analytical ‘contamination’ was avoided because of the very high resolution of both observation (spot location) and analysis. One example of a water-sensitive (‘swelling chlorite’) coating was also studied. This proved to have a very much more variable composition even within a single section. The coating appeared to include both chloritic and vermiculitic components. The effect of this on structural formulae is discussed and a model proposed in which the ‘talc’ layer may be common to both components.
The soil clays of Great Britain: I. England and Wales
Authors: Loveland P. J.
Published: December 2006

The mineralogy of the clay fractions (<2 µm) of the major soils of England and Wales is reviewed, and the data presented in terms of the 1:250 000 National Soil Map. Most soils developed in pre-Rhaetic sediments are dominated by mica with lesser amounts of chlorite and kaolin. Exceptions are soils developed in calcareous Coal Measure shales which have significant smectite contents, and freely drained soils in Keuper Marl which contain swelling chlorite, sepiolite and palygorskite. Soils developed in post-Triassic sediments are dominated generally by expansible minerals, except for those developed in Lower Lias and Estuarine Series rocks (Jurassic) which are dominated by mica and kaolin respectively. The presence of loess in soils seems to be associated with the occurrence of a complex interstratified mineral with X-ray diffraction properties akin to vermiculite. Weathering of soil clays is most marked in the wetter uplands, but over most of lowland England is detectable only by slight changes in non-exchangeable potassium content and cation-exchange capacity towards the soil surface. Applications of soil clay mineralogy in the fields of plant nutrition and soil mechanics are discussed, in particular the production of maps showing mineralogical provinces.
The soil clays of Great Britain: II. Scotland
Authors: Wilson M. J. , Bain D. C. , Duthie D. M. L.
Published: December 2006

The soils of Scotland are relatively young, being developed mainly on glacial drift deposited some 10 000 years ago. Only a small number of genetic soil types are represented, but this is more than compensated for by the wide variety of parent materials from which the drift ultimately derives. The major parent materials include granite and granitic gneiss, gabbro, basalt/andesite, mica-schist and related metamorphic rock types, Lower Palaeozoic greywackes and shales, Old Red Sandstone sediments, Carboniferous sediments, fluvioglacial sands and gravels, and estuarine silts and clays. The clay mineralogy of the soil associations developed on these parent materials is described and the origin of the clay minerals is interpreted. It is concluded that the influence of inheritance is predominant, but that the effects of pre-glacial weathering and Holocene pedogenesis can also be discerned. Inheritance has contributed a wide variety of clay minerals to the soils, including illite, kaolinite, chlorite, smectite and a number of interstratified minerals, pre-glacial weathering has resulted in the widespread formation of kaolinite and halloysite, irrespective of soil parent material or drainage class, and recent pedogenesis has brought about the transformation of inherited layer silicates by vermiculitization processes, with concomitant interlayer alumination, particularly in surface horizons.
The crystallinity and surface characteristics of synthetic ferrihydrite and its relationship to kaolinite surfaces
Authors: Saleh A. M. , Jones Angela A.
Published: December 2006

Synthetic ferrihydrites with Si added at mass ratios of Si/Fe = 0, 10, 20, 40, 80, and 160 × 10−3 have been studied to examine the effect of Si on the properties of ferrihydrite. The Si proportionally reduces the point of zero charge but influences surface area, loss of weight to 800°C and solubility in acid oxalate solution to varying degrees. At a critical concentration of Si (when Si/Fe = 20 × 10−3) these measured properties indicate a greater particle size and a more ordered structure. The relationship between synthetic ferrihydrite and the surface of kaolinite has been studied by a combination of surface area and charge determinations and TEM. An attraction predicted at pH 3 between ferrihydrite particles and the basal surface of kaolinite has been confirmed, and resulted in a stable coating. However, at pH 6 any attraction between the minerals appears to be too weak to produce a coating of the kaolinite surfaces.
Interparticle diffraction: a new concept for interstratification of clay minerals
Authors: Nadeau P. H. , Wilson M. J. , McHardy W. J. , Tait J. M.
Published: December 2006

A new conceptual model for interstratified clays is proposed, based on complementary use of the transmission electron microscope (TEM) and X-ray diffraction (XRD). Clays yielding interstratified XRD patterns are shown to be composed of aggregates of fundamental particles (here defined as an individual or free particle which yields a single crystal pattern by electron diffraction) whose interfaces are capable of adsorbing water and organic molecules. In these circumstances, the interstratified XRD character results from an interparticle diffraction phenomenon. Smectites are shown to be primarily composed of particles 10 Å thick corresponding to elementary 2:1 silicate layers. Nearest-neighbour regularly interstratified illitesmectite (K-rectorite) is composed of particles of elementary ‘illite’ 20 Å. thick, corresponding to two silicate layers coordinated by a single plane of potassium ions. Regularly interstratified chlorite-smectite (corrensite) consists of particles 24 Å thick corresponding to two silicate layers coordinated by a single brucitic sheet. The layer sequence examined by XRD is determined by the types and proportions of particles present within the clay material. Thus a sedimented aggregate of 20 Å elementary ‘illite’ particles appears to be a regularly alternating sequence of illite and smectite layers by XRD. Randomly interstratified itlite-smectite and chlorite-smectite can be synthesised by making mixed suspensions of the <0·1µm fractions of smectite with those of K-rectorite and corrensite respectively, providing experimental confirmation of the proposed model. Unusual associations, such as three-component illite-chlorite-smectite interstratified systems can be synthesised by making mixed suspensions of K-rectorite and corrensite. Long range regularly interstratified illite-smectite of the IIS and IIIS types are composed primarily of fundamental ‘illite’ particles 20–50 Å thick. Conventional illite is composed primarily of particles > 50 Å thick. This conceptual model has implications for the chemistry, behaviour and genesis of interstratified clays which are common constituents of soils and sediments.
Thermal analysis in the investigation of zeolitized and altered volcanics of Latium, Italy
Authors: Lombardi G.
Published: December 2006

The data obtained on zeolites, kaolins, alunites, hydrated sulphates and soils by DTA-TG-EGA carried out under various experimental conditions are discussed. Among the main subjects dealt with are chabazite and phillipsite identification and their quantification by TG, clay mineral distribution in size fractions of kaolins, significance and use of thermoanalytical data from alunitic rocks, the influence of calcite and calcined kaolinite on the sulphate DTA curves, rates of decomposition of hydrated sulphates, and thermal analysis of soils in forensic studies.