The sorption of Cd, Cu, Pb, and Zn ions by Na-rich bentonite, Al and Zr-pillared Na-rich bentonite (Al-MX80, Zr-MX80), the uncalcined hydroxy-intercalated precursors (HAl, HZr-MX80), and commercial Al-pillared bentonite EXM 534 was investigated. Experiments were conducted in ultrapure water and artificial leachate with varying pH. The experiments were performed over periods to 30 wk. Sorption characteristics were described with one and two-site Langmuir isotherms. The non-exchangeable quantities of heavy metals were determined by fusion of the sorbents after ion exchange with ammonium acetate.

The sorption of Cd, Cu, Pb, and Zn by bentonite was dominated by cation exchange. In artificial leachate, the sorption was reduced due to competition with alkali and alkaline-earth cations. The sorption of Cu, Zn, and Pb at pH 4.9 and Cd at pH 6.9 by Al and Zr-hydroxy-intercalated and pillared MX80 was governed also by cation exchange. In contrast, the sorbed quantities of Zn at pH 6.9 exceeded the cation exchange capacity (CEC) of HAl, HZr, Al, Zr-MX80, and EXM 534 and were partially non-exchangeable. The increase of the sorption of Zn with pH and its independence of the ionic strength of the solution at neutral pH suggest a complexation of Zn ions to surface hydroxyl groups of the intercalated Al and Zr-polyhydroxo cations and pillars. This complexation is the dominating sorption mechanism. Removal of dissolved Zn from solution with time is attributed to surface precipitation. Al-hydroxy and pillared bentonites are considered potential sorbents of Zn ions from neutral pH aqueous solutions, such as waste waters and leachates.

In May 1885, the Apache chief Geronimo, along with three other chiefs and a large band of adherents, absconded from their reservation in Arizona and fled to the mountains of New Mexico. The reservation life that had been imposed upon Indians by the United States government was a life that endeavored to mold them into good citizens; they attended school and church, wore European style clothes, farmed rather than hunted, and gave up many Indian traditions. It was a life Geronimo and his followers were unwilling to endure, and after some years of uneasy equilibrium, the chief led a revolt that turned into the so-called ‘Apache War.’ Geronimo held out for over a year, and it was not until the summer of 1886 that the war ended, and the chief surrendered. Eighteen years later, in 1904, the old Apache appeared at the Louisiana Purchase Exposition, the great World's Fair held in St. Louis, one of the grandest of the many such expositions staged in the late nineteenth and early-twentieth centuries. Here, he earned himself some money by charging fairgoers to have their photograph taken with him. There proved to be no shortage of whites eager to have a souvenir image of themselves posed with him; and others even bought the buttons off his coat as more tangible mementos of the old warrior.

The binary exchange of cations on clays and soils is generally regarded as a thermodynamically reversible process. The literature on soil chemistry and geochemistry, however, abounds with reports on cation exchange reactions that appear to have only limited reversibility, i.e., that exhibit hysteresis. A satisfactory explanation of this phenomenon is still lacking, even though a number of mechanisms have been advocated, e.g., charge or site heterogeneity at the surface, differential hydration of cations, dehydration of the exchanger, crystalline swelling hysteresis, and inaccessibility of sites caused by domain or quasi-crystal formation. In the present article, the relevant literature is reviewed and analyzed critically. On the basis of available evidence, it is shown that exchangeable cations can be classified into three groups, defined in such a way that hysteresis has, in the literature, generally not been observed when exchange reactions involved cations belonging to the same group, but has often been found when the reactions involved cations from different groups. Furthermore, it is argued that none of the five mechanisms mentioned can, in and of itself, account fully for the observed exchange hysteresis. A conceptual model is proposed that combines elements of these five mechanisms and is able to describe, at least qualitatively, the effects of factors such as clay type, electrolyte concentration, and extent of dehydration.

The introduction of Universal Credit, a new means-tested benefit for working-aged people in the UK, entails a significant expansion of welfare conditionality. Due to mothers’ disproportionate responsibility for unpaid care, women are particularly affected by the new conditionality regime for parents who have the primary responsibility for the care of dependent children. This article draws upon qualitative longitudinal research with twenty-four mothers subject to the new conditionality regime to analyse the gendered impacts of this new policy and whether there is variation in experiences according to social class. The analysis demonstrates that the new conditionality regime devalues unpaid care and is of limited efficacy in improving sustained moves into paid work. It also shows that the negative gendered impacts of the conditionality within Universal Credit are at times exacerbated for working-class mothers.

Dynamical and thermodynamic properties of water at room temperature in Ca- and hexade-cyltrimethylammonium- (HDTMA) exchanged bentonite were determined for 4 different water contents (~0.03–0.55 g water g-1 clay). Incoherent quasi-elastic neutron scattering (QENS) was used to measure the translational and rotational mobility of water in the clays, while chilled mirror dewpoint psychrometry measured water activity of the samples, differential scanning calorimetry (DSC) provided information about the temperature of dehydration and X-ray diffraction (XRD) quantified layer spacings for the clays. The neutron scattering data were fit to a jump diffusion model that yielded mean jump lengths, jump diffusion residence times and rotational relaxation times for water in the clays. Mean jump lengths were quite similar for the 2 different cation saturations at equivalent water contents, and decreased with increasing water content. The fitted jump lengths ranged from 0.27–0.5 nm and were 2–4 times larger than that found for bulk water (0.13 nm). Jump diffusion residence times were 3–30 times longer than that for bulk water (1.2 ps) and also decreased with increasing water content. The residence times were somewhat shorter for HDTMA-clay as compared with Ca-clay at equivalent water contents. Rotational motion was less strongly influenced than translational motion by the presence of the clay surface. The energy state of water in the 2 cation saturations were quite different; dehydration temperatures for the HDTMA-clay were approximately 30 °C lower than the Ca-clay at equal water contents, while water activities, as P/P0, were up to 0.6 units higher. A linear relationship was found between water activity and the translational diffusion coefficient, although at the highest water content, the diffusion coefficient of water for the HDTMA-clay was approximately 30% higher than that measured for bulk water.

The reality of the internet raises questions about our experience of the world. In the name of positivist science the colonial enterprise constructed a whole hierarchy of civilizations, putting Africa at the bottom of the scale - an issue of power. African society's relationship to the internet should be viewed within the general context of the encounter between Africa and techno-scientific rationality. The internet raises large questions about African received experience and lived experience, and the African conception of time. The internet's instantaneous time challenges the cyclical and linear nature of time in African cultures. Also, the its virtual space has little meaning in the African context of the generally two-dimensional - the visible and invisible.

It was precisely when printing became popular in Europe - which, for the first time in history, permitted the conservation and mass diffusion of ancient Greek, Arab, and Latin writings, a fact that signalled the beginning of the Renaissance - that the Letters of Amerigo Vespucci first appeared. These letters, like a revelation, speak of a novus mundus, a new world of unknown flora, fauna, and men, that contradicts the findings of Ptolemy‘s eminent Cosmography (published in 1478, in Rome), Theophrastus's History of Plants (published in 1498, in Venice), and the hallowed treatises of Aristotle, which were then in fashion.

The forms of Central Asian shamanism owe their relative homogeneity both to a commonly shared tradition and the influence of Islam. It is, however, possible to distinguish two distinct tendencies, which correspond to the two ethnic groups that inhabit this region, one Iranian-speaking and the other Turkish-speaking. At the same time, the process of Islamization does not in itself prevent the preservation of certain elements of shamanism pertaining both to the thought and practice of these Muslim peoples, nor to their secondary, non-official religious activities. In addition, certain customs that were developed within Islam itself, such as Sufism and transvestism, are believed by some investigators to have points of contact with shamanism.

Saponites were hydrothermally grown in the presence of amounts of NH4+, Na+, K+, Rb+, Ca2+, Ba2+, and Ce4+ equivalent with the CEC of the saponite (155 meq/100 g), with or without F−, at a temperature of 200°C for 72 hr. XRD and CEC data revealed the formation of a two-water-layer saponite with mainly Mg2+ as interlayer cation. Dehydration occurred between 25° and 450°C and dehydroxylation occurred in two steps between 450° and 790°C and between 790° and 890°C. The relatively small length of the b-axis between 9.151 and 9.180 Å is explained by considerable octahedral Al substitution (between 0.28 and 0.70 per three sites) and minor tetrahedral Al substitution (between 0.28 and 0.58 per four sites). Under the synthesis conditions applied in this study, less than 13% of the interlayer sites are occupied by Na+, K+, and Rb+; between 13.3% and 21% by Ca2+ and Ba2+; while NH4+ gives the highest value at 34%. The remaining sites are mainly filled by Mg2+. Ce4+ is not found in the saponite structure due to the formation of cerianite, CeO2. The presence of F− had little influence on the saponite composition. The formation of Mg-saponites is explained by a model in which an increased bayerite formation resulting in a higher octahedral Al3+ substitution and more Mg2+ in solution. Mg2+ is preferentially incorporated compared with the other interlayer cations due to its smallest ionic radius in combination with its 2 + charge.

I am quite prepared to admit that modern western thought is shot through with contradictions. For example, it is not coherent to think both that the idea of human nature is an illusion and that eugenics is an out-and-out evil; or to claim to be a democrat and exclude a priori the topic of eugenics from political debate. However, I personally very much doubt that the notions of nature and democracy are themselves in crisis. In my view they simply give rise to semantic confusion and false problems that certain basic twentieth-century discoveries - in the field of physics, anthropology and political science - ought to be able to clear up, if they were better known. We shall just touch on a few thinkers whose work may give us some pointers to a clearer, calmer view of things. First a philosopher, Raymond Ruyer (1902-1987), and an economist, Joseph Schumpeter (1883-1950), two of whose key ideas this paper will combine: a neo-Aristotelian conception of nature, implying the existence of regulating principles and norms, to which humans and their societies, like everything else, are subject; a procedural conception of democracy that says it is not an end in itself but, under certain conditions, an appropriate means of making political decisions and settling disputes. And in addition some anthropologists, who helped either to put human beings back into a neo-Aristotelian world, or to define more accurately the essence of the political: Claude Lévi-Strauss, whose structuralism gave back its full importance to the notion of formal cause and even to the idea of final cause, and André Leroi-Gourhan, who confirmed that ‘art imitates nature’ by demonstrating that technical skill is a natural extension of life, whose processes and results it mimics; Arthur Maurice Hocart, who demonstrated the ritual origin of all institutions, particularly political ones.

A macroscopic energy balance model for crystalline swelling of 2:1 phyllosilicates is presented. Crystalline swelling for a static system is modeled by a balance among the potential energies of attraction, repulsion and resistance. The potential energy of attraction is due to both the electrostatic interaction between the interlayer cations and the negative surface charge sites and to van der Waals attraction between layers. The potential energy of repulsion is due to the net hydration energy for the interlayer cations, the net hydration energy for the negative surface charge sites and Born repulsion. The potential energy of resistance represents irreversible work needed to overcome the mechanical resistance of the clay water system to both expansion and collapse. The potential energy of resistance is responsible for both hysteresis and the stepwise nature of crystalline swelling.

A numerical solution of the crystalline swelling model is presented and shown to yield reasonable estimates of basal spacings for octahedrally charged clays. Measured and predicted basal spacings are directly compared and are in general agreement (r2 = 0.39). Most of the scatter for the measured vs. predicted basal spacing relationship is attributed to inaccuracies of the assumptions used for the numerical solution. The crystalline swelling model readily accounts for the effects of layer charge and nature of the interlayer cations upon crystalline swelling, but does not account for the effect of charge site location upon crystalline swelling.

In May 2000 a group of researchers, university teachers and publishers met to consider the impact of the new media for knowledge transmission on the intellectual world and listed the projects ongoing in France for publishing content electronically. Eighteen months later no one is able to say whether there will one day be a significant body of electronic publishing with French content. Such a transformation calls for a moment's consideration. So what has happened?

This paper suggests an approach to the various possibilities of reading as a practice responsible for generating thought. It might be said that it is an approach to the dismissal of reading as the origin of other paths of thought. Utopia, understood as anticipation, yields its place to the figure of redemption (in Benjamin's sense of the word) as imminence of the absolutely other, expectation and extreme attention. The text invites the reader to try other routes in the practice of reading (other than solitary silent reading), in which the body and the senses play a part, and - especially - the other, to allow the advent of a thinking that welcomes justice. In an act of memory, reading - as heteronomy - opens onto the future.

The cultures here in question are those of mathematics and of physics that I shall interpret with the goal of exploring different modes of creativity. As case studies I will consider two scientists who were exemplars of these cultures, the mathematician Henri Poincaré (1854-1912) and the physicist Albert Einstein (1879-1955). The modes of creativity that I will compare and contrast are their notions of aesthetics and intuition. In order to accomplish this we begin by studying their introspections.

A model to compensate the 2:1 layer having excess negative charge owing to the reduction of Fe3+ to Fe2+ by sodium dithionite buffered with citrate-bicarbonate in nontronite, beidellite, and montmorillonite is proposed. This model is based on reassessing published experimental data for Fe-containing smectites and on a recently published structural model for reduced Garfield nontronite. In the reduced state, Fe2+ cations remain six-fold coordinated, and increases of negative charge in the 2:1 layer are compensated by the sorption of Na+ and H+ from solution. Some of the incorporated protons react with structural OH groups to cause dehydroxylation. Also, some protons bond with undersaturated oxygen atoms of the octahedral sheet. The amount of Na+ (p) and H+ (ni) cations incorporated in the structure as a function of the amount of Fe reduction can be described quantitatively by two equations: p = m/(1 + K0mrel) and ni = K0mrel/(1 + K0mrel); with K0 = CEC (9.32 − 1.06mtot + 0.02mtot2), where mtot is the total Fe content in the smectite, m is the Fe2+ content, mrel is the reduction level (m/mtot), CEC is the cation-exchange capacity, and K0 is a constant specific to the smectite. The model can predict, from the chemical composition of a smectite, the modifications of its properties as a function of reduction level. Based on this model, the structural mechanism of Fe3+ reduction in montmorillonite differs from that determined in nontronite and beidellite owing to differences in the distribution of cations over trans- and cis-octahedral sites.

The Tazzeka Mountain, located approximately 20 km south of Taza, eastern Morocco, is composed of a Westphalian volcano-sedimentary complex. It contains rhyolitic ignimbrites with the following minerals: quartz, potassium feldspar, oligoclase-andesine, and biotite. The ignimbrites are extensively altered because of a dense network of fractures in the massif. Alteration has resulted in the formation of spheroidal rocks and saprolite, the thickness of which depends on local topography. The evolution of the biotites in the ignimbrites was investigated by microprobe analysis of the mica crystals. This technique provides data that are not accessible through classical analytical methods. Biotites are transformed into secondary clay minerals, mainly chlorites and illites; intermediate stages are related to the degree of alteration of biotite, the latter being expressed by the K2O content which decreases progressively from 7.3 to 1.3%. Next come protochlorites and chlorites sensu stricto, in which the K2O content is 0.3%. Several processes including retrodiagenesis, hydrothermal activity, fumarolic activity, and geochemical weathering contributed to the transformation of the biotites at Tazzeka.

In soil environments, the surfaces of clay minerals are often coated with hydrolytic products of Al. However, limited information is available on the effect of hydroxyaluminum coatings on the interlayering of enzymes for montmorillonite. The objective of this study was to compare the adsorption of tyrosinase onto montmorillonite as influenced by levels of hydroxyaluminum coatings. Tyrosinase is one of the strongest catalysts in the transformation of phenolic compounds. Adsorption of tyrosinase onto Ca-montmorillonite (Ca-Mte) and different hydroxyaluminum-montmorillomte complexes (Al(OH)x-Mte), containing 1.0, 2.5 and 5.0 mmol coated Al/g clay, was studied both in the absence and in the presence of a phosphate buffer at pH 6.5 and 25°C. Except for Ca-Mte in the absence of phosphate where the adsorption isotherm was of C type (linear), the adsorption isotherms were of L type (Langmuir). More tyrosinase molecules were adsorbed onto Ca-Mte than onto the Al(OH)x-Mte complexes, both in the absence and in the presence of phosphate. This indicated the easy accessibility of the enzyme to the uncoated Ca-Mte surfaces. The presence of phosphate did not significantly affect the amount of tyrosinase adsorbed onto Ca-Mte, but substantially reduced the adsorption of tyrosinase onto Al(OH)x-Mte complexes. The higher the level of hydroxyaluminum coatings, the lower the amount of tyrosinase was adsorbed. Because of their affinity to the aluminous surfaces, phosphate ions evidently competed strongly with tyrosinase for Al(OH)x-Mte complexes adsorption sites. The intercalation of tyrosinase by Ca-Mte was indicated by the increased d-spacing of the complex as the amount of the enzyme adsorbed increased. The infrared spectra of tyrosinase-Ca-Mte complex showed that the amide II band of tyrosinase at 1540 cm-1 was practically unaffected by adsorption. The amide I band at 1654 cm-1 was shifted toward a higher frequency, indicating a slight perturbation in the protein conformation. This perturbation became more noticeable in the presence of Al(OH)x-Mte complexes. The data indicated that hydroxyaluminum coatings play an important role in retarding the adsorption of tyrosinase by montmorillonite, and phosphate effectively competes with tyrosinase for the adsorption sites on Al(OH)x-Mte complexes.