Vermiculite from Santa Olalla, Spain, was intercalated with tetramethylphosphonium [P(CH3)4+ = TMP], using a TMP-bromide solution at 70°C for three weeks. The resulting TMP-exchanged vermiculite, which contained a small (<5% of a site) amount of residual interlayer Ca, showed near perfect three-dimensional stacking. Cell parameters are a = 5.3492(8) Å, b = 9.266(2) Å, c = 14.505(6) Å, β = 97.08(2)°, space group is C2/m, and polytype is lM. Single-crystal X-ray refinement (R = 0.052, wR = 0.061) located two crystallographically unique sites for the phosphorus atoms (TMP molecule). The phosphorus atoms are occupied partially [P1 = 0.146(6), P2 = 0.098(5)] and are offset from the central plane of the interlayer by 1.23 Å to form two P-rich planes in the interlayer. Electrostatic interactions between the P cations and basal oxygen atoms essentially balance the negative charge associated with Al for Si substitutions in the tetrahedral sites. In addition, the orientations of the TMP molecules are probably different owing to packing constraints. The H2O site is located in the center of the interlayer, at the center of the silicate ring, and ∼3.09 Å from the Ca, which is also located on the central plane of the interlayer. Other H2O molecules are present in the interlayer, but could not be located by the diffraction experiment because they are randomly positioned in the interlayer. The tetrahedral rotation angle, α, is affected by the intercalation of TMP relative to tetramethylammonium (TMA), thus indicating that 2:1 layers are not simply rigid substrates, and that dynamic interactions occur during reactions involving adsorption and exchange.

The objective of this work was to prepare series of reduced-charge materials from different parent Li-saturated dioctahedral smectites, to investigate the effects of temperature, chemical composition and charge location in smectites on the charge reduction and to characterize reduced-charge smectites (RCSs) using methylene blue (MB) adsorption. The layer charge decrease, induced by Li fixation, is correlated with the trends in the spectra of MB-RCS dispersions in the visible region (VIS) spectra. Distribution of the negative surface charge of the clay minerals controls the distance between the adsorbed MB cations and thus affects the formation of MB dimers and higher agglomerates. Because each form of MB (monomer, dimer, higher agglomerate, J-aggregates) absorbs light at a different wavelength, the VIS spectra of MB depend sensitively on the charge density at the clay surface. Both cation exchange capacity (CEC) values and spectra of MB-clay dispersions clearly detect extensive reduction of the layer-charge density in reduced-charge montmorillonites (RCMs) upon Li-thermal treatment. The extent of charge reduction depends on the temperature of the thermal treatment, as well as on the octahedral charge of the montmorillonite. Reduction of the layer charge proceeds to a much lesser extent for smectites with mainly tetrahedral charge and high Fe content (Fe-rich beidellite and ferruginous smectite). Both CEC data and MB spectra detect only a slight decrease of the layer charge density, which relates to the low octahedral charge of these minerals. Following heating at higher temperatures (120-160°C), slightly higher Li fixation is indicated by CEC values; however, no charge reduction is confirmed by MB spectra. Release of protons accompanying Li+ fixation in Fe-rich smectites heated at 180 or 200°C was detected in the spectra of MB-clay dispersions and confirmed by potentiometric titrations.

Transmission electron microscopy (TEM) observation shows narrow regions in a Ti-containing Mg-rich annite of composition (K0.90Na0.02)(Mg0.72Fe2+1.78Mn0.03Ti0.27Al0.05)(Si2.77Al1.23)O10(OH,F)2 from a granitic rock, where the ±60° and 180° stacking angles occur extensively. These regions are a few hundreds of nanometers thick along the [001]* direction and are within 1M or 2M1 annite. The stacking sequence in one of these regions was determined by two atomic-resolution images recorded along [1̄10] and [010] of the same crystal. Stacking sequences with ± 120° or 180° rotations are dominant, although those with ±60° rotations occur also. Locally 2O and more complex sequences exist. Compositional analysis by TEM indicated no difference in the chemical compositions between these regions and the adjacent ones with regular 1M or 2M1 stacking sequence. The origin of these unusual stacking sequences in annite is discussed.

A commercial bentonite (primarily smectite) from Fischer Scientific Company (F bentonite) and a natural bentonite from Peru (P bentonite) were used in the preparation of pillared clays with polyoxymetal cations of Al that were subsequently modified with Ce and La. Several Al/metal ratios (5 and 9) were used to investigate the effects on the thermal and hydrothermal stability of these synthetic clays. The structure of these materials was studied by X-ray diffraction. Isotherms were determined by N2 adsorption. Thermal stability was determined using thermogravimetric (TG) measurements and ara-monia-TPD (temperature programmed desorption) was used to obtain acidity data. These materials exhibited basal spacings from 16 to 20 Å, with surface areas from 239 to 347 m2g−1, with microporosity contributing from 50 to 80% of the total surface area. Pillared clays prepared from F bentonite generally showed larger basal spacings and surface areas than those prepared from P bentonite. Pillared clays modified with Ce or La did not show any apparent structural changes relative to the Al-pillared clays. Pillared clays modified with Ce and La had similar acid properties as Al-pillared clays. In contrast, the thermal and hydrothermal stabilities of these materials were greater than Al-pillared clays. However, Ce-pillared clay appears to be more effective than La-pillared clay in delaying the dehydroxylation of pillared clays with increasing temperature. The intercalation of Ce and La into Al-pillared clays improved the thermal stability, which may increase the utility of these materials as catalysts.

Five montmorillonites, one hectorite, and two vermiculites were treated with OH-Al solutions containing rapid- and slow-reacting polymers of similar concentrations. With all smectites, both rapid- and slow-reacting OH-Al polymers were much more preferentially adsorbed than monomeric species. Relatively slow-reacting OH-Al polymers were more preferentially adsorbed than rapid-reacting ones. The average basicity of the adsorbed Al was 2.46, which was close to that of the OH-Al polymers in the original solution. The OH-Al polymers that enter the interlayer resemble those in original solutions.

With vermiculites, the solution concentration of rapid-reacting OH-Al polymers was much reduced after reaction. The average basicity of the adsorbed Al was 1.99, which was considerably lower than that in the original solution. It is postulated that OH-Al polymers break to monomeric Al ions and then enter the clay. The monomeric Al species that enter the clay interlayers hydrolyze and polymerize in situ and become fixed. The H+ ions released from hydrolysis convert the rapid-reacting OH-Al polymers to monomeric Al in solution. Limited amounts of slow-reacting polymers were adsorbed because of their resistance to acid depolymerization.

The interaction of H+- and Cu2+-ions with Ca-montmorillonite was investigated in 0.1 mol/dm3 solutions of Ca(CIO4)2 at 298.2 K by Potentiometrie titrations using both glass electrodes (for H+) and ion specific electrodes (for Cu2+ ). The experimental data were interpreted on the basis of the surface complexation model. The calculations were performed with the least-squares program FITEQL (Westall, 1982) using the constant capacitance approximation. The best fit was obtained with a set of equilibria of the general form

$\begin{array}{c}p{H}^{+}+qC{u}^{2+}+\equiv SOH\iff \left(H^{+}{)}_p\right(C{u}^{2+}{)}_q(\equiv SOH{)}^{(p+2q)+}\\ {\beta }_{p,q\left(int\right)}^s=\frac{\text{[}{H}_{p}C{u}_q(\equiv SOH{)}^{(p+2q)}]}{\text{[}{H}^{+}{]}^p\left[C{u}^{2+}{]}^q\right[\equiv SOH]}\end{array}$

$\equiv TOH-H^{+}\iff \equiv {TO}^{-}log{\beta }_{-1,0\left(int\right)}^S=-5.77(\pm 0.07).$

Hydroxyaluminosilicate (HAS) and hydroxyaluminum (HyA) ionic solutions having final Al concentrations ranging from 3.74 to 4.00 mM; NaOH/Al molar ratios of 1.0, 2.0 and 2.5; and Si/Al molar ratios of 0.00, 0.27–0.30, 0.51–0.56 and 0.95–1.01 were prepared through the interaction of AlCl3, or-thosilicic acid and NaOH solutions. When these solutions reacted with <2 µm sized vermiculite (Vt) and montmorillonite (Mt), varying amounts of Al and Si were fixed on Vt and Mt clays. Potassium fixation and exchange capacities of HyA/HAS (OH/Al = 1.0, 2.0 and 2.5)-Vt and HyA/HAS (OH/AI = 2.0)-Mt complexes were compared with those of untreated Vt and Mt at added K levels ranging from 21 to 319 cmolc kg−1. The untreated Vt clay showed K fixation as high as 94 cmolc kg−1, in contrast to only 16 cmolc kg−1 exchangeable K. The untreated Mt fixed a maximum of 9 cmolc K kg−1 out of a total K adsorption capacity of 67 creole kg−1. In the HyA/HAS-Vt complexes, K fixation reduced drastically in comparison to untreated Vt, and ranged from 9 to 24 cmolc kg−1 out of their total K adsorption capacities of 61 to 81 cmolc kg−1. In the HyA/HAS-Mt complexes, too, the amount of K fixed reduced to a great extent in comparison to Mt and ranged from 1.48 to 1.84 cmolc kg−1. Potassium became more exchangeable due to the presence of hydroxy-interlayers in the clays. The reduction in CEC and the well-known propping effects of hydroxy-cations’ islands in the interlayers might have hindered K fixation by the complexes. The relationships of maximum K fixing capacities of the HyA/HAS-Vt complexes with the amounts of Al, Si and Al + Si fixed on Vt were all exponential and negative. However, the amount of Al + Si or only Al fixed on Vt appeared to be the best indicator of K fixation capacities of hydroxyinterlayered Vt clay.

A process for treating smectite-bearing rock samples that utilizes LR White resin; allows TEM observation of expanded smectite interlayers and therefore preservation of original rock textures. Examples of several lattice fringe images are shown, including: (1) Dioctahedral smectite layers from a shale (1388.9 meter depth, Texas Gulf Coast) give fringes that consistently have spacings of 1.2–1.3 nm, yet duplicate other features previously observed in collapsed samples. (2) Packets of illite layers give fringes with 1.0-nm spacings coexisting with packets of (dominantly) R1 I/S having 2.1-nm lattice fringe spacings in a Gulf Coast shale from 4742.1 m. (3) Rectorite from Garland Co., Arkansas gives 2.3-nm lattice fringes. Samples with wide ranges of I/S ratios and lithologies have been found to be permanently expanded with retention of original textures, commonly leading to unambiguous identification of illite and smectite interlayers in lattice fringe images.

This paper is organized around the theme of political representation in India. Its first section deals with the changing politics of representation in India in the past two decades, the growing demands for proportional representation, and for political inclusion of two influential groups: the scheduled castes and tribes and Other Backward Classes. In the second section, representation is briefly explored in relation to women and minorities. The third section deals with some reflections on the challenges of political representation in India's diverse democracy. The author aims to account for the varied trajectories of caste, community and gender in Indian politics through an analysis of the politics of representation. The main argument developed here is that the politics of presence does not offer a resolution to the problems of under-representation nor to the more fundamental issue of the representation of the interests of constituents, especially the needs of the most vulnerable.

—The charge of the expandable interlayers in a series of fourteen diagenetic illite/smectites (I/S) from lower Paleozoic K-bentonites was determined by the alkylammonium ion exchange method. The magnitude (<0.50 equivalents per half formula unit) and characteristic heterogeneous distribution of interlayer charges in eight samples with expandabilities from 70% to about 15% confirm the smectitic character of the expandable interlayers in this range. This result coupled with the lack of a correlation between expandability and interlayer charge is consistent with the hypothesis of a layer-by-layer transformation from a precursor smectite to highly illitic I/S clays during K-bentonite diagenesis. The charge of the expandable interlayers in I/S samples with about 10% or less expandabilities have been inferred to be vermiculitic rather than smectitic. The K-fixed interlayers and expandable interlayers in these samples appear to be similar in charge. The significantly higher charges inferred for the highly illitic samples can be consistent both with a layer-by-layer transformation and the neoformation mechanisms proposed in the literature for the formation of illite.

Carbon credits from the reducing emissions from deforestation and degradation (REDD+) projects have been criticized for issuing junk carbon credits due to invalid ex-ante baselines. Recently, the concept of ex-post baseline has been discussed to overcome the criticism, while ex-ante baseline is still necessary for project financing and risk assessment. To address this issue, we propose a Bayesian state-space model that integrates ex-ante baseline projection and ex-post dynamic baseline updating in a unified manner. Our approach provides a tool for appropriate risk assessment and performance evaluation of REDD+ projects. We apply the proposed model to a REDD+ project in Brazil and show that it may have had a small, positive effect but has been overcredited. We also demonstrate that the 90% predictive interval of the ex-ante baseline includes the ex-post baseline, implying that our ex-ante estimation can work effectively.

Fine kaolinite suspensions were mixed with unaged or aged FeCl3 in this experiment. The interaction between clay particles and Fe3+ hydrolysis products was studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The proportion of Fe adsorbed was measured and the electrical charge on the clay particles was determined by electrophoresis. The effect of this interaction on flocculation of clay suspensions was investigated in a series of sedimentation tests. The Fe3+ ions acted as counterions when their concentration was low and when unaged FeCl3 solution was used. Otherwise, their hydrolysis complexes acted as a bonding agent between kaolinite particles. The dispersion-flocculation behavior of kaolinite suspensions was found to be in agreement with the theory of Derjaguin, Landau, Verwey and Overbeek (DLVO), as the sedimentation behavior could be predicted from the data of zeta potentials (ζ).

Why does one hear so much about tolerance today, when as little as a few decades ago it was considered an obsolete virtue, anachronistic and outstripped by the progress of our civilization? When a virtue is lacking we remember it most! Must we conclude from the emphasis placed on tolerance these last few years that we have entered an era of generalized mutual incomprehension? The conquests of the intellect; local, national and international juridical practices; education open to global issues; the intermixing of humanity that has never before “moved” so much under the combined effect of emigration; tourism and the developments in transportation and vast information exchanges served by efficient techniques that make communication one of the greatest benefits of our culture; all this could have led mankind into a surplus of exchanges on all levels, and better mutual appreciation leading to more tolerance.

I intend to explore the relationship between the history of historians and the public use of history. This relationship, in my opinion, is both conflictual and convergent. As we shall see later on, this assertion is anything but obvious; among historians the idea of a neat opposition prevails, with no possibility of reconciliation, between professional practices of history (the profession of historians) and the extremely vast and confused domain of its “public use.”

Before undertaking an analysis, I must explain what I mean by the public use of history. I have adopted, at least initially, a purely extrinsic definition of the term. By the “public use of history” I am referring to all that is developed outside the domain of scientific research in its strictest sense, outside the history of historians which is usually written by scholars and intended for a very limited segment of the population. Public use of history includes not only the various means of mass communication, each with its own particularities (journalism, radio, television, cinema, theater, photography, advertisement, etc.), but also the arts and literature; public places such as schools, history museums, monuments and urban spaces, etc., and finally institutions, formal or otherwise (such as cultural associations, parties, and religious, ethnic and cultural groups, etc.), which, with more or less clearly partisan objectives, endeavor to promote a more or less polemic reading of the past as compared to the generally accepted common sense of history or historiography, a polemical reading based on the memory of their respective groups. Indeed, politicians have a large role in the most visible and most talked about manifestations of the public use of history and they have a particular responsibility in its degeneration (I shall return to this point in my conclusion).

During processing of Athabasca oil sands, the finely divided solids form an aqueous suspension, which ultimately stabilizes as a gel-like structure retaining up to 90% of the process water. This gelling phenomenon is believed to be caused by colloidal inorganic components. Kaolinite and mica are the main crystalline minerals in these colloidal solids; swelling clays are present in only trace amounts. Non-crystalline components are more concentrated in the finer fraction of the solids. Although the surfaces of the colloidal solids are virtually free of Fe, some contamination with polar organic matter is observed.

Français, vous avez la mémoire courte (You French have short memories) was the title of a film showing in a cinema opposite Saint-Sulpice church. It was the early 1960s; scarcely 15 years had passed since the end of the Second World War and the horrors of Nazism had not yet been fully revealed. Germany was an occupied and divided country. France was fighting in Algeria.