The oxidation state of structural iron greatly influences the physical-chemical properties of clay minerals, a phenomenon that may have significant implications for pollutant fate in the environment, for agricultural productivity, and for industrial uses of clays. Knowledge of redox mechanisms is fundamental to understanding the underlying basis for iron's effects on clays. Past studies revealed that the extent of Fe reduction varied depending on the reducing agent used, but this variation may not have been a simple function of the reduction potential of the reducing agent. The objective of this study was to identify the relationship between the Fe reduction mechanism and free radical activity in the reducing agent. Several reducing agents and their mixtures with the Na-saturated, 0.5 to 2 μm size fraction of ferruginous smectite (SWa-1) were analyzed by electron spin resonance (ESR) spectroscopy to determine the presence of unpaired electrons or free radicals. Only Na2S2O4 exhibited paramagnetic free-radical behavior with a signal at about g = 2.011, which was attributed to the sulphoxylate (S02− ·) free radical. The free radical was labile in aqueous solution, and the ability of Na2S2O4 solution to reduce structural Fe in the smectite decreased with age of the solution and paralleled the disappearance of the free radical signal in the ESR spectrum. The paramagnetic species was preserved and enhanced if Na2S2O4 was added to the clay suspension, indicating that either the clay surface stabilized the SO2− · radical or the additional unpaired electrons were produced in the clay structure.

The scene takes place in O'Higgins Park, in Santiago, Chile, on 1 October 1995. Some women have just taken their place on the stage and the enthusiastic audience is applauding, the women have started singing accompanied by a guitar, but they cannot be heard, for the audience is still applauding. One of the women gets up. Like the others, she is wearing a white blouse and a long black skirt, she is old and her hair is grey. She moves to the front of the stage, chooses her place and stops, her eyes search the horizon but do not wander aimlessly, her eyes are fixed somewhere between the here and the hereafter. When she finds what she is looking for, she raises her right hand to wave a white handkerchief, and the dance begins. The audience, suddenly attentive, watches. And what do they see? Not the woman alone on the stage, but the empty space which she traces. The empty space disturbs us, as Chilean spectators, because the cueca, the national folklore dance, is danced by two people, or it is not danced at all. The invisible other is invoked by this woman's every gesture and we do not smile when faced with the absence of her man because we have a premonition that she is not pretending, we have a premonition that she can see him. The image of women dancing alone has become one of the symbols of the struggle of the families of the disappeared under the dictatorship of General Pinochet. The families are commemorating, on 1 October 1995, the twentieth anniversary of their organization into an association in 1975. The term “the disappeared” has progressively become accepted to indicate the victims of a novel, coercive practice in Chile, since the coup d’état on 11 September 1973. The forced disappearance of people differs from political assassination, as Amnesty International never ceases to indicate in the various reports which it commissions on them. In the Chilean case, this speciality is in part due to the security system which has taken on the responsibility of destroying all organized opposition to the military dictatorship: the DINA, the intelligence service created by the military junta, which is only answerable for its actions to the junta. More fundamentally, the special character of disappearance is due to the invisibility of the victim's body and to the doubt that this invisibility arouses within the victim's family circle: the disappeared is not identified as dead because his death is never certified, on the other hand his sudden and unexplained absence indicates that he is a person in danger and that this danger extends to all those who notice his absence.

Kaolinite from the Black Ridge, Clermont, has relatively low δ18O (12.3‰ to 14.8‰) and very low δD values with a large variation (−120‰ to −85‰). Comparison of these data with those from the nearby Denison Trough and elsewhere in eastern Australia, together with previous studies of the mineralogy of the sedimentary rocks, suggests that extensive kaolinization of the “White Section” resulted from weathering during the Late Triassic to Early Jurassic periods. The relatively large variation in δD values of kaolinite probably derives from post-formational isotopic exchange with other fluids.

The similarity between δ18O values of kaolinites from Black Ridge and from the Denison Trough suggests that the small Miclere-Black Ridge basin may have been part of the Denison Trough before the Late-Triassic inversion. The preservation of original δD values in kaolinite at Black Ridge indicates that unlike the Denison Trough, which was reburied at more than 1000 m, the Miclere-Black Ridge basin was not rebuffed at great depth during the Mesozoic period.

The experience of the body, which all speaking subjects share, is at the origin of many corporeal metaphors and figurative expressions which are laced throughout all of our productions of language, and which reveal the diverse representations of the body as elaborated within linguistic communities. For instance, when the French say that someone “does nothing with his ten fingers,” to signify his inactivity or laziness, this expression reveals a representation of the hand, which is viewed as “THE SEAT OF ACTIVITY.”

The electrochemical properties of kaolinite before and after modification with chlorodimethyl-octadecylsilane have been studied by electrophoretic mobility, surface charge titration, and extrapolated yield stress measurements as a function of pH and ionic strength. A heteropolar model of kaolinite, which views the particles as having a pH-independent permanent negative charge on the basal planes and a pH-dependent charge on the edges, has been used to model the data. The zeta potential and surface charge titration experimental data have been used simultaneously to calculate acid and ion complexation equilibrium constants using a surface complex model of the oxide-solution interface. The experimental data were modeled following subtraction of the basal plane constant negative charge, describing only the edge electrical double layer properties. Extrapolated yield stress measurements along with the electrochemical data were used to determine the edge isoelectric points for both the unmodified and modified kaolinite and were found to occur at pH values of 5.25 and 6.75, respectively. Acidity and ion complexation constants were calculated for both sets of data before and after surface modification. The acidity constants, pKa1 = 5.0 and pKa2 = 6.0, calculated for unmodified kaolinite, correlate closely with acidity constants determined by oxide studies for acidic sites on alumina and silica, respectively, and were, therefore, assigned to pH-dependent specific chemical surface hydroxyl groups on the edges of kaolinite. The parameters calculated for the modified kaolinite indicate that the silane has reacted with these pH-dependent hydroxyl groups causing both a change in their acidity and a concomitant decrease in their ionization capacity. Infrared data show that the long chain hydrocarbon silane is held by strong bonding to the kaolinite surface as it remains attached after washing with cyclohexane, heating, and dispersion in an aqueous environment.

Fe(II) and Fe(III) in various proportions were coprecipitated by NH3 at pH ≈ 11. The Fe(II)/Fe(III) ratio (x) was varied from 0.10 to 0.50. After stabilization by aging at pH ≃ 8 in anaerobic conditions, hydrous precipitates were characterized by electron microscopy, Mössbauer spectroscopy, and kinetics of dissolution in acidic medium. At any x value, all stable products exhibited the structure of (oxidized) magnetite. For x ≤ 0.30, two distinct species were coexisting: the one (“m”) was made up of ca. 4nm-sized particles with a low Fe(II) content (Fe(II)/Fe(III) ≈ 0.07), and the other (“M”) consisted of particles of larger, more or less distributed sizes, and composition Fe(II)/Fe(III) ≈ 0.33; “M” increased relative amount with increasing x. For x ≥ 0.35, “M” was the only constituent and its Fe(II)/Fe(III) ratio was equal to x. “M” is identified with (nonstoichiometric) magnetite, whereas “m” is likely to be an oxyhydroxide. Mechanisms of formation are discussed, and a phase diagram is proposed which schematizes the evolution of the coprecipitation products with x and with time. Addition of Fe(II) after the precipitation of Fe(III), instead of coprecipitation, yielded very similar results.

The acidic properties of acid-modified montmorillonite and vermiculite were determined by pyridine and ammonia adsorption to correlate with the alkylating and dehydrating activity of the activated samples. Treatment of the minerals with different concentrations of hydrochloric acid results in the variation of overall acidity and density of acidic sites. Infrared (IR) spectral and differential scanning calorimetric analyses have revealed the presence of Bronsted and Lewis acid sites on the activated samples. The catalytic activity towards the above reaction has been correlated to the acid strength and density of Lewis acid sites. Treatment of montmorillonite with hydrochloric acid in the range of 0.1 and 0.3 M and vermiculite with 0.2 to 0.3 M seemed to be suitable for the conversion of methanol into olefin-rich hydrocarbons. Acid-activated montmorillonite catalyzed the isopropylation of benzene to a maximum extent of 16%, whereas acid-activated vermiculite gave a maximum conversion of only 4%.

The amount of Mn2+ adsorbed or removed from solution by birnessite is several times greater than its reported cation exchange capacity. Extractability of the sorbed Mn2+ decreases with aging. It is uncertain whether the sorbed Mn2+ is oxidized on the surface or incorporated into the structure of birnessite. Using X-ray powder diffractometry and transmission electron microscopy, a study was conducted to examine the mineralogical alteration of birnessite after treatment with various concentrations of MnSO4 and solution pH.

The sorbed Mn2+ was not directly oxidized and remained on the birnessite surface. The sorption of Mn2+ was followed by alteration of birnessite with the formation of new Mn minerals. The specific Mn minerals formed were governed by the pH of the reaction, and the rate of the transformation was determined by Mn2+ concentration and pH. Nsutite and ramsdellite were identified at pH 2.4, crypto-melane at pH 4, groutite at pH 6, and manganite at pH 8. Other Mn minerals formed at these and other pH levels could not be identified. As the concentration of Mn in the solution decreased, the time required to form new minerals from the birnessite increased. The newly formed phases were the result of structural conversion since dissolution of birnessite and reprecipitation of new phases were not observed.

The surface thermodynamic properties of a series of n-alkylammonium and quaternary ammonium treated clay films were determined by contact angle measurement of drops of test liquids using the Young equation for polar materials. The two clays were a Wyoming montmorillonite (SWy-1) and Laponite RD. For a series of primary n-alkyl (6 ≤ n ≤ 15) and several quaternary organic cations, the organo-clay (both SWy-1 and Laponite RD) showed very little change in the value of γLW compared to the equivalent ammonium-saturated clay. Also, γ⊕ remained small or increased slightly compared to the ammonium-saturated clay. For SWy-1 exchanged by both quaternary ammonium and primary n-alkylammonium cations, the value of γ⊖ was smaller (0.1 ≤ γ⊖ ≤ 15.8 mJ/m2) than for the ammonium-saturated clay (γ⊖ = 36.2 mJ/m2) and decreased linearly with the number of carbon atoms. The γ⊖ values for the organic cation-exchanged Laponite RD samples (24.2 ≤ γ⊖ ≤ 31.2 mJ/m2) were smaller than or comparable to the ammonium saturated clay (γ⊖ = 30.7 mJ/m2), and were relatively insensitive to the number of carbon atoms in the organic cation. Thus, for both clays the increased adsorption of organic molecules resulting from replacement of inorganic cations by organic cations is due primarily to the decrease in the value of the Lewis base parameter, γ⊖.

Among the most important problems related to Russia's development, which are considered in depth in various kinds of forum and the media, both here and in the west, there is, however, an almost total absence of such a crucial strategic topic as working out an urban policy. In the meantime the crises that Russia is continually facing as it undergoes reforms are caused by the disparity between the tasks that have to be completed and the stage of civilization we are at. In order to fast forward to another level we have only the strategic role of the cities, in particular the largest of them, to guide us. Without real cities with a developed urban culture no effective solution can be found to the problems we are up against, whether they are economic, cultural, social or human rights issues.

Shales have often been cited as the source of authigenic material that occurs in coarser grained sediments, but there are few comprehensive studies of diagenesis in shales that rigorously attempt to determine if they are sources for potentially mobile constituents or if they retain those constituents within the shale body. The silicate diagenesis of a Lower Cretaceous marine mudstone, the Harmon Member, was investigated by determining the bulk chemistry, clay mineral compositions and mineral modes using standard analytical techniques and linear programming. Changes in mineralogy are observed in hemipelagic laminated mudstones (LM) that are attributable to diagenesis despite relatively constant bulk compositions. These include authigenic kaolinite formation and illitization of detrital muscovite, K-feld-spar and authigenic kaolinite. No diagenetic trends in mineralogy are observed in rapid and episodically deposited transition zone (TZ) sediments because of primary (depositional) mineralogical variability. Diagenetic changes in mineral modes for shales of the Harmon Member are small, suggesting that silicate diagenesis proceeds under relatively “closed system” conditions. The occurrence of authigenic quartz suggests that much of the Si released from the dissolution of quartz and chert is precipitated within the Harmon Member. Al, Ti, and K apparently are conserved. Burial induced increase in temperature is inferred to be the primary control on silicate diagenesis within the Harmon Member.

The controversy currently surrounding national literatures in foreign languages can be summed up by the famous statement: “to be or not to be, that is the question.”* But how is one to be oneself without having been that other whom one cannot deny (in the Marxist sense) since one sings as one grows? How, whatever effort one makes to deny one's father, can one fail to be presently what one is by separating oneself from the story of one's own birth or from the birth of one's own story?

To my mind, the most urgent current task in the social sciences is one in the context of which the unduly cut-and-dried distinctions between positive and normative, between sociology and ethics, between secular pluralism and religious spirituality, and so on, should be abandoned. I would like to reclaim the legacy of a Marxian-type dialectic by stating that the social sciences today (and I would even risk speaking of a single present-day ‘social science’) have the threefold task of (1) thinking through in depth the directions of a desirable social change, (2) asking what are the ‘resources for action’ already available for this end within the totality of social actors and (3) identifying the moral capacities that need to be stimulated and/or created so that the resources for action which are not yet available, but which are desirable under point (1), may be able to take root and flourish. I defy anyone to disentangle clearly and analytically the positive and normative parts of such a task …

If the somewhat acrimonious debate on the status of the gift that I have had with Alain Caillé for the last two years continues to hold my interest and if I have eventually overcome my irritation in the face of what has occasionally seemed to me a failure of understanding linked to the defence of an ‘article of local faith’, it is because our debate is a fundamental part of the worthwhile task of the social sciences. Nevertheless, I shall make it clear straight away that the expression ‘sociological gift’ hardly satisfies me, in the light of the description of this task which I have just supplied.

Scanning electron microscopy has revealed the presence of spherical, lath and platy kaolinite in gels with Si/Al atomic ratio ranging from 1.84 to 0.76 that are hydrothermally treated under different temperature and time conditions. Hemispherical structures and excavated zones, at different stages of evolution, have been observed on the surface of the gel grains, indicating that spherical particles do not precipitate from the solution but are generated from the gels. The quantity of spherical particles depends on temperature, time and the chemical composition of the starting gel. Products from starting material with Si/Al ≈ 1 yield the highest quantity of these particles. Being metastable, sphere dissolution controls the chemistry of the solution and consequently the morphology of the precipitating crystals thus producing more elongated, curved and irregular outlines when gels with Si/Al ≈ 1 are hydrothermally treated.

One day a newly hatched eagle fell from its mother's clutches as she was flying over a chicken yard. The young eagle grew up in the chicken yard with young chickens and took on the habits, customs, and behavior of chickens. He ate like a chicken, walked like a chicken, and generally performed his daily routine like the birds who surrounded him. One day an eagle flew over the chicken yard, perhaps a parent eagle, looking for the lost eagle. Perched high on a tree's limb over-looking the chicken yard, the eagle saw the young eagle that had fallen out of its mother's clutches. The old eagle called to the young eagle, “Eagle, can you hear me?” The young eagle thought of himself as a chicken and did not respond to the call of the eagle in the tree. However, the old eagle continued to call out to him, “Eagle down there, hello.” Finally the eagle in the chicken yard thought, can that eagle in the tree be yelling to me? So he looked up at the tree and saw that the old eagle was beckoning to him to fly up to the tree's branch. The young eagle said, “I cannot fly. I am a chicken.” Insisting that he try to fly the old eagle said, “No, you are not a chicken you are an eagle and I know your parents, in fact, I am your mother and your father is waiting for me to bring you.”

The adsorption of arsenate (As(V)) on kaolinite, montmorillonite and illite was investigated at varying pH and competing anion concentration while holding As(V) concentration (6.7 × 10−7M), clay suspension density (2.5 g L−1) and ionic strength (0.1 M NaCl) constant. The effects of 2 concentrations of phosphate (P) or molybdate (Mo) (6.7 × 10−7 and 6.7 × 10−6M) on As(V) adsorption envelopes (adsorption vs. pH) gave evidence for direct competitive adsorption (in the case of As(V) + P) and possibly site-specific non-competitive adsorption (As(V) + Mo). Distinct As(V) adsorption maxima occurred at approximately pH 5.0 for kaolinite, 6.0 for montmorillonite and 6.5 for illite, and ranged from 0.15 to 0.22 mmol As(V) kg−1. When both As(V) and P were present at equimolar concentrations (6.7 × 10−7M), As(V) adsorption decreased slightly, whereas As(V) adsorption substantially decreased in binary As(V)/P systems when the P concentration was 6.7 × 10−6M, which was 10 times greater than As(V). The presence of Mo at equimolar (6.7 × 10−7 M) and 10 times greater (6.7 × 10−6M) concentrations than As(V) caused only slight decreases in As(V) adsorption because the Mo adsorption maximum occurred at pH < 4. The constant capacitance surface complexation model was applied to As(V) and P adsorption data and was used to predict As(V) adsorption at varying P concentrations. The model gave reasonable descriptions of As(V) adsorption on the 3 clay minerals at varying pH and in the presence of a competing oxyanion (P), indicating that surface complexation modeling may be useful in predicting As(V) adsorption in soils.

Hydraulic conductivity tests were conducted on thirteen compacted clayey soils being used for compacted clay liners at landfills throughout the United States. The soils were prepared to various molding water contents and then compacted and permeated in the laboratory. Results of the tests show that for all of the soils, zones exist in the compaction plane (i.e., dry unit weight vs. water content) where the hydraulic conductivity is similar. These zones fall roughly parallel to contours of constant initial saturation (degree of saturation at compaction), with lower hydraulic conductivities generally occurring for conditions corresponding to higher initial saturation. Wet of the line of optimums, lower hydraulic conductivity is also attained for soils that are more plastic and have a greater quantity of fines. A regression equation was developed from the data to estimate hydraulic conductivity given the initial saturation, compactive effort, plasticity index, and clay content.

Television, newspapers and magazines often discuss the presence in Japan of dekasseguis from Brazil. This migratory movement, which started in 1985, has started to show signs of decline. The recession in Japan has been accompanied by the laying off of around 20,000 Brazilian dekasseguis - employed in businesses in the industrial sector (cars, electronics and food production) - which explains the reduction in the number of candidates for departure.

The emigrants have generally been drawn by attractive salaries, while always aware that they were being offered work refused by the local population, considered kitsui (heavy), kitani (dirty) and kiken (dangerous). The hope of amassing sufficient savings in a few years to enjoy a better standard of living on their return to Brazil weighed significantly on their decision to leave.