bluuebunny/crossref_metadata_2025_split huggingface dataset:
Position Statement
Authors: Simner Marvin L. 
Published: December 2006

Each spring teachers throughout Canada are required to administer a series of provinciallymandated tests to the students in their classes. Approximately six months later the results are made available to the public. It is now common practice for the press the report the results, to rank the schools according to the results, and to invite the public to engage in a school-by-school comparison of the rankings. It is also common practice for the press, in commenting on the poor performances displayed by certain schools, to place the blame for these performances largely, if not solely, on the schools themselves. Our concern over this practice is with the failure on the part of the press to acknowledge the many other factors aside from schooling that are known to influence test performance. These include, but are not limited to, family stability, parental involvement and expectations for student success in school, early and ongoing home stimulation, and student motivation, student absenteeism, as well as student capacity for learning. Because students are not randomly assigned to schools and because schools have little or no control over the majority of these factors, any attempt to place the blame for poor test performance on the schools alone without giving proper consideration to each of these other factors is problematic at best and misleading at worst. Hence, by taking such a narrow position when dealing with an issue as complex as the cause of students' test performances, we believe the public is being misinformed on a matter that is extremely important to the operation of schools and therefore to the education and well being of children. Our greatest concern, however, is over the possibility that this singular emphasis on the schools as the cause of students' test performances could generate considerable harm by placing unwarranted pressure on teachers, administrators, and ultimately on the students themselves to increase test scores or risk losing status within the community. Indeed, there is growing evidence that such harm is already occurring in the United States from similar comments in the US press concerning the poor performance of certain schools on the state-mandated tests. With the hope of preventing similar situations from occurring in Canada, and in line with the view expressed by the Ontario Education Quality and Accountability Office, which is responsible for the development and scoring of the Ontario exams, it is our position that it is improper for the press to invite the public to compare schools based solely on the outcome of the mandated test results. We also recommend that in any future articles that deal with the results, in order to avoid misleading the public, the press should ensure that the public is fully informed of the various factors, in addition to schooling, that are likely to account for differences that may exist among schools.
Interaccion de fosdrin con montmorillonita
Authors: Sanchez Martin M. J. , Sanchez Camazano M. 
Published: December 2006

ResumenSe ha estudiado la interacción de fosdrín (pesticida organofosforado) con montmorillonita mediante difracción de rayos X y espectroscopia infrarroja. Este insecticida forma con montmorillonita dos tipos de complejos, con espaciados basales 16·05 y 20·06 Å. La formación de uno u otro tipo depende del estado de hidratación y del catión interlaminar de las muestras, de la naturaleza del disolvente y de la concentración de fosdrín. En los espectros de infrarrojo de los complejos, las vibraciones de valencia P =O y C =O del fosdrín se desplazan hacia frecuencias más bajas. La magnitud del desplazamiento de estas vibraciones es función del poder polarizante del catión interlaminar. El desplazamiento de la vibración de valencia C =O depende además del tipo de complejo y de su grado de hidratación. La vibración de valencia C=C se desplaza hacia frecuencias altas en los complejos de espaciado basal 16·05 Å. Los resultados obtenidos indican que el complejo de 16·05 Å es monocapa y que las moléculas de fosdrín (forma trans) deben interaccionar con los cationes interlaminares a través de ambos grupos P =O y C =O. El complejo de 20·06 Å es de dos capas y las moléculas (forma cis) interaccionan solamente a través del grupo P =O.
Structure de l'espace interlamellaire de la vermiculite Mg bicouche
Authors: Alcover J. F. , Gatineau L. 
Published: December 2006

RésuméL'étude des diffusions, en dehors des taches de Bragg, produites par les molécules d'eau et les cations échangeables des vermiculites magnésium bicouches (d001 ∼ 14·4 Å) permet de proposer un modèle de l'espace interlamellaire. Les groupements cation-molécules d'eau (Mg-12H2O) présentent une organisation bipériodique (maille centrée 3a,b) dans des domaines limités. Chaque motif est constitué par un octaèdre Mg-6H2O auquel est liée fortement une seconde ‘sphère’ d'hydratation, formée également par six molécules d'eau (distances entre atomes d'oxygène des deux sphères d'hydratation de l'ordre de 2·65 Å).
Organisation de l'espace interlamellaire dans les vermiculites monocouches et anhydres
Authors: Rausell-Colom J. A. , Fernandez M. , Serratosa J. M. , Alcover J. F. , Gatineau L. 
Published: December 2006

RésuméLes vermiculites Mg, Ca, Sr et Ba ont été étudiées par diffraction des rayons X et absorption infra-rouge.Pour les vermiculites monocouches, l'espacement interréticulaire est compris entre 12·2 et 11·45 Å.On distingue: (i) les vermiculites Ba; le cation, entouré de 5 à 6 molécules d'eau, est à environ 1Å du plan médian et il intéragit avec un hydroxyle structural du feuillet le plus proche, (ii) les vermiculites Mg, Ca et Sr; le cation, entrouré de 3 ou 4 molécules d'eau,est dans le plan médian ou dans son voisinage (0·3 Å), et il n'interagit pas avec les hydroxyles des feuillets.Pour les vermiculites anhydres, l'espacement interréticulaire est inférieur à 10 Å, le cation est dans le plan médian et il intéragit avec les hydroxyles de 2 feuillets opposés.A partir de ces résultats, complétés par les données de la bibliographie, des modéles sont proposés pour représenter l'organisation de l'espace interlamellaire.
Determination, a l'echelle absolue, de l'intensite diffractee aux rayons X par les argiles
Authors: Pons C. H. , Ben Brahim J. , Yücel A. , Tchoubar D. , Tchoubar C. 
Published: December 2006

RésuméLa mesure de l'intensité à l'échelle absolue consiste à déterminer le pouvoir diffusant de l'objet rapporté au motif élémentaire de la structure, c'est-à-dire exprimé en nombre d'électrons libres équivalents diffusant indépendamment et qui donnerait, en chaque point de l'espace réciproque, le même effet que l'objet. Les avantages de cette méthode sont les suivants: (i) elle permet de corriger la courbe expérimentale de la diffusion incohérente et ainsi d'augmenter le nombre de réflexions quantitativement exploitables; (ii) elle permet une meilleure caractérisation de la nature des défauts structuraux et, pour des systèmes hétérogènes tels que des particules en suspensions, elle rend possible la séparation des effets de diffraction spécifiques de chaque phase; (iii) elle rend possible l'interprétation des fonds de diffusion. Ces propriétés sont illustrées sur quelques exemples d'application (kaolinite, sépiolite mal cristallisée et suspension de montmorillonite-Na dans l'eau).
Morfologia y genesis de caolinitas en rocas silicificadas de la provincia de Avila (Espana)
Authors: Marfil R. , Bustillo A. , Garcia Palacios MaC. 
Published: December 2006

ResumenSe realiza un estudio detallado de las distintas fases minerales (caolínicas y silíceas) que aparecen en rocas silicificadas tanto graniticas como sedimentarias de la provincia de Avila.Las técnicas utilizadas (A.T.D., difracción de rayos X, microscopía electrónica de trasmisión y de barrido) permiten establecer una clasificación de estos minerales segun sus propiedades térmicas, parámetros cristaloquímicos, y morfologías identificadas al scaning.Sa dá una interpretación genética a cada uno de los tipos de caolinitas encontrados (macrocaolinitas en acordeón, microcaolinitas en gusanillo y criptocaolinitas). Los dos primeros tipos pueden ser explicados por procesos conjuntos de alteración hidrotermal y ‘weathering’ de feldespatos y micas. El tercer tipo (criptocaolinitas) es de más difícil interpretación al aso-ciarse con ópalo C-T en diques que cortan a rocas granitoideas y otras veces al presentarse como matriz de areniscas sedimentarias.
Etude de la couche interfoliaire des hydrates a deux couches des vermiculites calcique et magnesienne
Authors: Fornés V. , De La Calle C. , Suquet H. , Pezerat H. 
Published: December 2006

RésuméL'étude porte sur la décomposition du massif de bandes de vibration de valence O-D centré vers 2500 cm−1 que présentent les spectres infrarouge des hydrates à deux couches des vermiculites -Ca et -Mg partiellement deutérées. La détermination des bandes composantes a été effectuée à partir, d'une part de l'étude du dichroïsme des bandes de vibration infrarouge, d'autre part des données structurales disponibles sur les couches interfoliaires de ces minéraux. Ces deux méthodes conduisent—avec un accord satisfaisant—à une décomposition en 4 bandes composantes correspondant à 4 types de liaisons O-D...O. Parmi ces liaisons entre molécules d'eau, certaines sont relativement courtes, ce qui conduit à penser qu'il existe dans la couche interfoliaire de ces hydrates une charpente de molécules d'eau un peu analogue à une charpente anionique.
Adsorption of alcohols by smectites: IV. Models
Authors: Annabi-Bergaya F. , Cruz M. I. , Gatineau L. , Fripiat J. J. 
Published: December 2006

AbstractIn the three previous papers of this series the role played by the exchangeable cations in the adsorption of methanol by homoionic montmorillonites has been investigated by different techniques, namely desorption isotherms, X-ray determination of the basal spacings and IR spectroscopy. In this last paper, models based on the previous discussions are presented. In the adsorbed state, methanol shows a strong tendency to form on the clay surface, hydrogen-bonded zig-zag chains analogous to those in crystalline CH3OH. The exchangeable cations perturb this arrangement to different extents. For Li+ the perturbation is negligible, for Ca2+ a complete rearrangement is observed and for Na+ and Ba2+ the chains are broken into smaller fragments.
A swelling hematite/layer-silicate complex in weathered granite
Authors: Wilson M. J. , Russell J. D. , Tait J. M. , Clark D. R. , Fraser A. R. , Stephen I. 
Published: December 2006

AbstractA naturally occurring hematitic iron oxide/layer-silicate complex has been found in red mottled patches of a deeply weathered granite in north-east Scotland. X-ray diffraction shows a basal spacing of 36 Å—also observable by high resolution electron microscopy—which expands to 40 Å with glycerol and contracts to 33·5 Å on heating. Selected area electron diffraction reveals a composite hematite/layer-silicate pattern with the a-axis of hematite parallel to the b-axis of the silicate. The IR spectrum of the complex clearly shows the contribution made by each of the components. The silicate, with bands due to OH stretching at 3602 cm−1, OH deformation at 855 cm−1, and Si-O stretching at 1085, 1035, 540 and 471 cm−1 resembles ferruginous pyrophyllite, while the hematite, with a perpendicular band at 647 cm−1, in-plane bands at 519, 438, 400, 302 and 227 cm−1 and a characteristic pattern of relative band intensities, is similar to a platy form of soil hematite. Electron microprobe analysis of individual particles gives the complex an (Fe + Al): Si ratio of 6:1, which is consistent with a structure made up of twelve octahedral sheets terminated on both sides by a silicate sheet. It seems likely that the complex developed from a siliceous ferrihydrite which became progressively more organized with geological time.
Etude en microscopie electronique a balayage de quelques kaolins d'origines differentes: apports de cette technique pour la comprehension de leurs geneses
Authors: Esteoule-Choux J. 
Published: December 2006

RésuméL'examen des textures de kaolins au M.E.B. apporte des données complémentaires utiles pour la compréhension de leur genèse. Les kaolins provenant d'une altération météorique ont une texture poreuse constitutée par de gros paquets de plaquettes hexagonales empilées de façon lâche ce qui les différencie nettement des kaolins d'origine hydrothermale dont la texture est compacte et la porosité faible. Les kaolins sédimentaires montrent une association de petites plaquettes accolées les unes aux autres quand on les volt suivant les plans de clivage, ou présentent une orientation plus ou moins marquée dans la direction perpendiculaire. Enfin I'observation des textures permet de mesurer I'influence et I'importanee de la diagenèse dans les dépôts argileux.
Depositional facies, diagenetic clay minerals and reservoir quality of Rotliegend sediments in the Southern Permian Basin (North Sea): a review
Authors: Seemann U. 
Published: December 2006

AbstractThe Southern Permian Basin of the North Sea represents an elongate E-W oriented depo-centre along the northern margin of the Variscan Mountains. During Rotliegend times, three roughly parallel facies belts of a Permian desert developed, these following the outline of the Variscan Mountains. These belts were, from south to north, the wadi facies, the dune and interdune facies, and the sabkha and desert lake facies. The bulk of the gas reservoirs of the Rotliegend occur in the aeolian dune sands. Their recognition, and the study of their geometry, is therefore important in hydrocarbon exploration. Equally important is the understanding of diagenesis, particularly of the diageneticaily-formed clay minerals, because they have an important influence on the reservoir quality of these sands. Clay minerals were introduced to the aeolian sands during or shortly after their deposition in the form of air-borne dust, which later formed thin clay films around the grains. During burial diagenesis, these clay films may have acted as crystallization nuclei for new clay minerals or for the transformation of existing ones. Depending on their crystallographic habit, the clay minerals can seriously affect the effective porosity and permeability of the sands.
The brittle mica-like KNiAsO4 and its organic derivatives
Authors: Beneke Klaus , Lagaly Gerhard 
Published: December 2006

AbstractThe nickel arsenate KNiAsO4 has a mica-like layer structure with surface charge densities similar to brittle micas. In contrast to micas it easily exchanges alkylammonium ions. The interlayers have paraffin-type chain arrangements, as in alkylammonium vermiculites and alkylamine smectites and vermiculites, but the very regular chain packing causes a marked odd/even alternation of the basal spacings. The reactions of KNiAsO4 throw light on the exchange behaviour of micas.
Quantitative determination of goethite and hematite in kaolinitic soils by X-ray diffraction
Authors: Kämpf N. , Schwertmann N. 
Published: December 2006

In the past, two factors have impeded the quantitative estimate of Fe-oxides in soils by X-ray diffraction. First, Fe-oxides are still quite often considered X-ray amorphous, although numerous results, e.g. a low ratio of oxalate- to dithionite-soluble Fe, have indicated the opposite. Second, even if crystalline, the cocentration of Fe-oxides in many soils is low, thereby complicating their identification by XRD. Recently, however, more sensitive methods such as Mössbauer spectroscopy and Differential-XRD (Schulze, 1981) have been introduced, which substantially reduce the lower limit of detection. Because these two methods are not generally available and, especially in the case of M&oum;ssbauer spectroscopy, are rather time consuming, ordinary XRD should be adapted for quantitative estimation of Fe-oxides.Determination can be facilitated by using samples in which the Fe-oxides are concentrated by particle-size separation and a 5 M NaOH boiling treatment (Norrish & Taylor, 1961). The latter treatment is particularly suitable for kaolinitic soils as the Fe-oxides are unaffected―provided certain precautions are taken (Käimpf & Schwertmann, 1982a). This paper gives details of a procedure for the quantitative estimation of goethite (Gt) and hematite (Hm) by XRD.
Two examples of quantitative analysis by simulated X-ray powder diffraction patterns
Authors: Corbato C. E. , Tettenhorst R. T. 
Published: December 2006

AbstractQuantitative estimates were made by visually matching computer-simulated with experimental X-ray powder diffractometer patterns for two samples. One was a natural mixture of dickite and nacrite in about equal proportions. The second sample contained mostly quartz with corundum and mullite in small (0.5–1%) amounts. Percentages deduced from pattern matching agreed to within ±10% of the weight fractions of the components determined by an alternative method of analysis.
Selective liquid adsorption on dodecylpyridinium clay by HPLC
Authors: Stul M. 
Published: December 2006

Traditionally, adsorption from binary solutions is determined as the difference between the adsorbate concentration in the solution before and after contacting with the solid adsorbent e.g. hexadecylpyridinium-clay. this is essentially a static method. The bulk composition can be measured by means of a differential liquid interferometer (Dékány et al., 1978b) or by gas chromatography (Nikulitchev et al., 1979). The specific excess adsorption of the mixtures, n1°, is then calculated as (Kipling, 1965):1where n0 is the total amount of the liquid mixture referred to unit mass of the adsorbent (mmol/g adsorbent), xl,0 is the mole fraction of the ith component before adsorption, and xi is the mole fraction of the ith component in the equilibrium homogeneous liquid phase.
Mineralogical facies of a weathered serpentinized lherzolite from the Pyrenees, France
Authors: Fontanaud A. , Meunier A. 
Published: December 2006

AbstractWeathering products of a serpentinized Iherzolite were investigated using optical microscopy, X-ray diffraction, infrared spectroscopy, and electron microprobe and wet-chemical analysis methods. The original mineral assemblage of the rock was chrysotile-enstatite-diopside-picotite-magnetite-calcite. Rock porosity governed the types of chemical microsystems from which the clay minerals were derived. These microsystems were grouped into three types. (1) Grain microcracks and grain boundaries. These were the earliest manifestations of weathering. Only pyroxenes were affected and transformed into talc + iron oxides. (2) Plasma zones in which the rock structure was preserved. The talc + oxide and chrysotile were both altered into a saponitic mineral. Picotite was oxidized to oxipicotite. (3) Fissure zones. In the argillized zones the rock was restructured. Saponite was altered to nontronite + magnesium silicate gel. Talc was also transformed to the same gel. Fissures were often filled with clay cutans and some were edged with iron oxides. Mineral facies in the different zones have been plotted in Si-R2-R3 coordinates.
Characterization of iron(II)-and iron(III)- exchanged montmorillonite and hectorite using the Mössbauer effect
Authors: Helsen J. A. , Goodman B. A. 
Published: December 2006

Abstract
At room temperature both Fe(III)-exchanged montmorillonite and Fe(III)-hectorite gave similar Mössbauer spectra, each consisting of a single doublet with parameters characteristic of ferric iron. At 77 K the Fe(III)-hectorite gave a spectrum similar to that observed at room temperature, but with the montmorillonite an additional distinct doublet, with relatively large values of both isomer shift and quadrupole splitting, was observed. The Fe(II)-exchanged samples behaved very differently at room temperature and 77 K. At 77 K well-defined doublets were produced; these had quadrupole splittings similar to those shown by the ion and appreciably greater than those observed for Fe(II) in the structural sites in layer-silicates. At room temperature, however, there was no absorption corresponding to ferrous ions in either of the specimens, because the recoil-free fraction was low as a result of the loose association between the ion and the mineral lattice.
Elements traces des argiles: des marqueurs
Authors: Mosser Christine 
Published: December 2006

Resume
L'étude d'une vingtaine de cas montre que les caractéristiques principales du cortège d'éléments traces des roches éruptives et métamorphiques sont conservées par les fractions fines des produits d'altérations. On peut ainsi, à partir de l'ensemble des éléments traces contenus dans une fraction fine, identifier la famille pétrographique de la roche mère. La mémoire de la roche mère est partiellement conservée par la fraction fine après érosion des profils d'altération, et sédimentation des matériaux érodés dans des environnements divers. La conservation de la mémoire de la roche mère est cependant inversement proportionnelle à l'activité chimique du nouveau milieu de sédimentation. L'influence du milieu de sédimentation peut devenir prépondérante. Les exemples cités montrent que les éléments traces des argiles peuvent être interprétés, dans de nombreux cas, comme des marqueurs d'héritage: héritage direct d'une roche mère dans des conditions d'altération, héritage d'une histoire sédimentaire antérieure à des remaniements de dépôs; comme des marqueurs d'environnements sédimentologiques divers.
Organic reactions in a clay microenvironment
Authors: Ballantine J. A. , Purnell J. H. , Thomas J. M. 
Published: December 2006

AbstractAlthough natural Na-bentonite has little catalytic activity, various cation-exchanged bentonites have proved to be effective catalysts for a wide variety of organic reactions. In the presence of these catalysts alkenes can be induced to add (a) water, to yield branched-chain symmetrical ethers; (b) alcohols, to give a variety of ethers; (c) thiols, to yield thio-ethers; (d) carboxylic acids, to give esters. The number of products obtained in each reaction depends on the ease of rearrangement of the carbocation intermediates. High yields are obtained where a single carbocation intermediate is formed, A variety of elimination reactions is also catalysed by these sheet silicates. Water is eliminated from alcohols to produce ethers, ammonia is eliminated from amines to make secondary amines, and hydrogen sulphide is eliminated from thiols to give dialkyl sulphides. In most cases the ion-exchanged bentonites react as acidic heterogeneous catalysts.
Catalysis by montmorillonites
Authors: Adams J. M. , Clapp T. V. , Clement D. E. 
Published: December 2006

AbstractA preliminary set of ‘rules’ for acid-catalysis by ion-exchanged montmorillonites has been derived from the reaction of alkenes, alcohols and alicyclic acids over such catalysts. It has been shown that: 1. Cr(III) and Fe(III) are the most active interlayer cations. Although Al is also active, the exact procedures used for the ion-exchange and washing steps appear to be critical for giving catalysts of reproducible activity. 2. Below 100°C, the reactions proceed provided they involve tertiary or allylic carbocation intermediates, whereas at 150–180°C reactions involving primary and secondary carbocations are possible. 3. Reactions of carbocations with unsaturated hydrocarbons take place overwhelmingly in the interlayer region of the clay, where the hydrocarbon double bond can be effectively polarized. Reactions of carbocations with polar, oxygenated, species can take place on the surface of the clay particles as well as in the interlayer space. 4. When the acid-catalysed reactions are performed in the liquid phase and involve tertiary carbocations, the most suitable solvents are those which provide miscibility; 1,4-dioxan is especially good. However, when more acid conditions are required for the formation of primary and secondary carbocations a non-polar solvent is more efficacious.