To determine the dependency of rheological properties on mineralogical characteristics, eleven organophilic hectorite and nine organophilic saponite samples were prepared from hydrothermally synthesized smectites and a quaternary ammonium salt containing mainly octadecyl groups as alkyl chains and were examined by X-ray powder diffraction (XRD), particle size, chemical, and rheological procedures. The rheological properties of the organophilic products dispersed in toluene were found to depend chiefly on (1) particle size, (2) the expansion behavior of the stacked clay platelets, in which the amount and location of negative charge of the silicate layer affected the expandability, and (3) the amount of methanol added as a polar activator. By the addition of 2–4% methanol, apparent viscosities of the hectorite clays were drastically increased at low shear rate, although even a 10% addition did not significantly affect the saponite clays. Under the most suitable gellation conditions, the saponite clays showed lower apparent viscosity than the hectorite clays. Inasmuch as the former had its negative charge near the surface of the silicate layer and formed strong bonds to the organic ion, the expansion of the platelets was apparently difficult. An optimum layer charge for increasing the viscosity was found; specifically 0.45–0.50 and 0.50–0.55 equivalents per half unit cell for saponite and hectorite clays, respectively. Because the saponite clays contained a denser population of organic ions than the hectorite clays, the ion density in the interlayer of both clays was considered to be the same, i.e., about 0.4 organic ions per unit ab area.

An X-ray powder diffraction study of a vermiculitized chlorite in an amphibole schist near Limoges, France, shows the following weathering sequence: chlorite → ordered interstratified chlorite/vermiculite → vermiculite. Mössbauer spectroscopy indicates that vermiculitization proceeded by the release of ferrous iron from the 2:1 mica layer of the chlorite. The ferric iron content of the vermiculite product is almost the same as that of the initial chlorite. Infrared spectroscopy and chemical microprobe analyses show that Mg was preferentially extracted from the hydroxide sheet of the chlorite, whereas the Si and Al contents progressively increased to the point of the formation of a pure dioctahedral aluminous vermiculite. The Si, Al, and Mg removal processes support currently accepted vermiculitization mechanisms, but the behavior of Fe is slightly different. In this weathering sequence, vermiculitization does not appear to have taken place by the oxidation of Fe2+, but rather, by the simultaneous leaching of Fe2+ and Mg.

During the epigenetic alteration of boehmitic karstic bauxite in the Vlasenica region of Yugoslavia, which was caused by siliceous water descending through the deposit by means of cracks, fissures, etc., oolites were less altered compared with the coexisting matrix material, which was intensely kaolinized. The following zonal alteration pattern of the oolites was identified: a diaspore enrichment zone, followed by a diaspore-boehmite enrichment zone, and then the original bauxite. Considering this alteration pattern and that determined previously for the matrix material, the following overall pattern of alteration was established: a kaolinite-diaspore zone, followed by a boehmite-diaspore zone, and then the original bauxite. The alteration solutions reacted with the bauxite to form solution-matrix and solution-oolite subsystems, which were characterized by different types of diffusion and geochemistry.

In the kaolinite-diaspore zone Si-metasomatism kaolinized the matrix, and excess Al partly migrated into the oolites, forming diaspore, and outward into the bauxite. The latter Al-remobilization resulted in a transition zone, in which new boehmite was formed in both the matrix and the oolites, and diaspore only in the oolites. Thermodynamic models of oolites and whole bauxite alterations were established, on the basis of stability diagrams calculated for the mineral assemblages of both the oolites and the matrix, in the alteration zones and in the deposit as a whole. Based on these models, the genesis of the diaspore and the relationship of diaspore-boehmite-kaolinite assemblages in natural systems at low temperature and low pressure can be described.

Mythologies generally devote much attention to the birth of heroes and gods whose coming into the world is described as particular. Our first examples come from Greek mythology.

The Furies, goddesses of vengeance, were born of the blood of Uranus who had been castrated by his son Cronos. Athena sprang, completely armed, from the head of Zeus which Prometheus had struck with an axe, an act sometimes attributed to Hephaistos. The Centaurs came from a union of Ixion with a cloud to which Zeus had given the appearance of Hera with whom he was in love. Adonis came into the world from a myrrh tree (Smyrna in Greek ) which opened magically to give him birth. Ten years earlier a woman named Smyrna (myrrh) had committed incest with her father, Theios, without his realizing it; when he discovered the fact, he changed her into the tree known by that name. Bacchus was drawn out, a six months old fetus, from the body of his mother by Zeus. The body was lying in coals lit by the lightning and thunder accompanying the god's chariot as he came to visit Semele. Terrified at the sound of nature's fury, she had died of shock. Zeus sewed the fetus in his thigh and, when the time came, gave birth to Dionysius.

Mobility measurements were made for dry-ground mica particles dispersed in aqueous KCl, Cr(NO3)3, and cetyltrimethylammonium bromide (CTAB) solutions. In the latter solutions charge reversal occurred at about 2 × 10-6 M and 3 × 10-5 M, respectively. Negative zeta potentials in KCl solutions calculated using the Smoluchowski equation are about one third of the corresponding values obtained from streaming potentials and force measurements using mica sheets. Good agreement, however, was obtained when positively charged groups created during grinding were neutralized, and the zeta potentials were corrected according to the procedure of O'Brien and White with an assumed average particle size of 0.25 μm. When the zeta potentials of positively charged particles were corrected in this way, agreement with values calculated from force measurements was also improved.

With the current interest in the use of transition metal-exchanged phyllosilicates as catalysts for novel organic syntheses, investigations into the factors which affect the movement of reactant, product, and solvent molecules into and out of their interlamellar region are of considerable importance. Mixed organic-water intercalates of a Wyoming montmorillonite, exemplified by the Na-montmorillonitepyridine-water system which can form four different intercalates exhibiting basal spacing of 29.3, 23.3, 19.4, and 14.8 Å depending on the pyridine: water ratio, have been used as a model system. X-ray and neutron diffraction and quasielastic neutron scattering data relating to the interconversion of interlayer species indicate that access to and exit from the interlayer space is hindered at high partial pressures of water by a water-film diffusion barrier in the interparticulate voids which exist between the aggregated silicate layers. At lower water vapor pressures the rate-limiting step for interconversion from one intercalate to another is the rate of transport of reagents and products to and from the clay particles. Under conditions where these rates are fixed, the rate-limiting step is the rate of diffusion of the pyridine molecule in the lower-spacing intercalate. Processes which involve a change in basal spacing do not necessarily proceed via a single discrete step, but are also affected by the amount of water made available to the system. In organic reactions catalyzed in the interlamellar space of various cation-exchanged montmorillonites (e.g., the conversion of alk-1-enes to di-2,2’-alkyl ethers and the reaction of alcohols to form ethers), rate-determining steps similar to those found above are likely to be operative. In particular, for reactions carried out in the liquid phase, where mass transport is facile and where phase-transfer problems are avoided, such reactions are likely to be diffusion controlled.

What is the difference between the earthly paradise, the Golden Age and the ideal city? This question is most important for whoever is interested in the various ways human societies have had for imagining an ideal state of perfection or social harmony. If we are not to confuse such different systems of representation as mythical thought, millenarianism and Utopia, it is absolutely necessary that we do not reduce the descriptions of an earthly paradise and a Golden Age to simple precursors of the ideal city of the Utopians. It is especially important not to call “Utopian” every representation of the ideal society, Utopia being only one— and the most, recent—of its modalities. The Utopian dream Translated by Jeanne Ferguson takes up and at the same time alters the paradisiacal and millenarian imagination: it would be difficult to believe that the passage of primitive societies to great urban civilizations, then to modern society occurred without major repercussions on the vision of these societies, that the ideal state of social perfection did not vary from one to the other.

Ca-K.-, Na-K-, and Ca-Na-exchange isotherms on four reference smectites were studied. The electric charge on the four smectites was due predominantly to cationic substitution in the octahedral layer and varied between 90 and 122 meq/g (cmole(+)/kg) clay. The affinity of the clays for K increased with a decrease in the fraction of K in the exchange phase. The selectivity coefficients of the smectites for K increased with an increase in charge density. The effect was similar in the Na-K- and Ca-K-exchange isotherms. Charge densities on the smectites had no effect on the Ca-Na-exchange isotherm. The electrostatic attraction forces between the platelets increased with increase in charge density. The low hydration energy of adsorbed K was apparently not enough to overcome these attraction forces as the charge density on the smectites increased. Equilibrium between the low hydration energy of adsorbed K and the electrostatic attraction energies between the platelets is postulated to explain the results.

To select as the subject of a study of limited size a topic as fundamental and, additionally, one so long discussed as has been the case with literary practice greatly risks—and we are fully aware of this—appearing to be an undertaking which is both presumptuous (how many studies, sometimes major ones, have been devoted to this question during recent decades?) and doomed to failure (is it serious to presume, in a few pages, to deal, even partially, with so vast and so complex a subject?). However, one precise reason causes us to think that it is time, today, to re-examine this ancient problem in new terms. The field of French literary research is at present characterized by a major institutional and ideological fact, the massive reality of which certain particular or collective efforts, no matter how remarkable these might be, cannot cover over. An airtight seal continues to separate, globally, traditional literary research from recent studies produced by certain linguists and speech historians in the domain of linguistic practices. Whence this scientifically paradoxical consequence: studies dealing with fundamentally similar objects—discursive practices—are presently being conducted in parallel, on the basis of theoretical premises which are radically opposed in most cases, with each one almost absolutely ignorant of the others. This situation, we believe, is exceedingly harmful to literary research. By making all interdisciplinary relation impossible as well as inhibiting certain questioning necessary within the realm of this research, it contributes to blocking progress in large measure. Need we point out that we nourish no naive hopes of overturning within the space of a few pages a situation whose roots, both institutional and ideological, are so deep? Nor does one distinguish oneself more by providing definitive answers for these basic problems which we propose discussing here, answers which one might even believe possible to guarantee as fully correct. We would only like to attempt to prove, by re-examining in new terms some fundamental problems of literary theory, the advantage which this theory might be able to find in certain data drawn from linguistics and the “analysis of discourse”, and inversely to propose certain theoretical readjustments which a specific reflection on literary practice seems to make necessary in the field of these two disciplines, particularly in that of the second. The pages which follow should, therefore, only be taken for what they are: an attempt, limited in its scope and problematic in its conclusions, to break down some barriers and to open a breach at certain critical points.

My purpose in this paper is to present a non-Marxist conception of exploitation. While this analysis of exploitation may share features with a Marxist conception, its acceptability is not dependent upon a prior agreement with that world view.

A study of the physics of separating and reattaching flows around bodies with sharp edges is reported. Data from direct numerical simulations of the flow around a rectangular cylinder with aspect ratio 5 at different Reynolds numbers are used. The flow is decomposed into multiple interacting flow phenomena such as the laminar boundary layer in the front face, the separated shear layer, the flow impingement at reattachment, the reverse boundary layer within the recirculating bubble and the near- and far-wake flow. A detailed analysis of the physics of these phenomena is provided, including the slow modulation induced by large-scale instabilities related with vortex shedding. The entrainment phenomena acting along the separated shear layer and their unbalance between its inner and outer sides are recognised as fundamental mechanisms determining the tendency of the flow to reattach and the overall fluxes of momentum and heat. The behaviour of entrainment is found to be strictly related with the shear-layer velocity difference that in turn is determined by the behaviour of the reverse boundary layer and by its strength in counteract adverse pressure gradients. The physical understanding of the compound role played by these and all the other mechanisms composing the flow, poses the basis for the formulation of theoretical frameworks able to unify all these interacting phenomena. Finally, the present work provides access to high-fidelity flow statistics of relevance for benchmark activities on bluff bodies with sharp edges.