The day is one of the fundamental experiences of our natural existence. The obvious cycle of the sun, the alternation of sleep and being awake provide a link between the life of the body and the great regularity that assigns their successive moments to light and to darkness. Only a simplified abstraction allows us to consider time lived as an homogeneous flow. Our existence, in its proper substance and in its larger environment, is dominated by the rhythm of days and nights. Our very experience of the reality of objects is subject to it: the universe of things depends on the light of day that reveals it. It shrivels and becomes uncertain when night falls, with terror and dreams taking its place. The evidence that appears with the clarity of day is not of the same order as apparitions that arise from the depth of darkness.

This survey reflects on a creative workshop which the authors ran for the ‘The State of Urban History: Past, Present, Future’ conference (July 2023). ‘Making manifestos for urban history’ was an experiment to encourage small group work and co-operative outputs in a conference setting, allowing for an atypical ‘many-to-many’ model of participation. During the session, five groups each produced a manifesto poster addressing issues that they thought were important for the future of urban history. The survey sets out the form the workshop followed, considers those who were involved and comments on how successful the workshop was in fostering conference community and active learning. Feedback recorded at the end of the session indicated that it was indeed successful in both these areas. Overall, the workshop demonstrated that when urban historians work together across generations and continents, they produce work of real value, which is resilient and sustainable.

The most ordinary events astonish only those who think about them. What can be more natural than two people talking? They are from the same country, they speak the same language, they understand one another. They have things to say to each other and they say them. Anyone who would try to question such evident truisms would be seen as attempting to be a spinner of paradoxes. And yet…

First of all is it as natural as it appears that two people should stop and speak? To an impartial observer of the behavior of one's peers this would not seem to be the case. Most of the people we rub elbows with daily—in the street, in the subway, on a beach, in a hotel or even in the apartment building where we have lived for ten years—are people whom we do not accost and to whom we never speak. In order for people to speak to one another, certain circumstances must exist; there must be a ritual of introduction and a mutual consent that often occurs only after a certain resistance has been overcome. There are important differences to be observed in this respect among different peoples and, within the same nation, among people of different classes. But in every case dialogue is preceded by a preparatory phase of prudent observation, reserve and mistrust during which the partners size one another up and seek to situate themselves in relation to each other.

Behind every Utopia there is always a territory, but a territory that “is not here”, a territory removed from immediate reality in space or in time. In time, when the Utopia invokes the past of an Age of Gold or a Paradise Lost “illo tempore,” but also when there is a gamble with the hope of a better world to be organized in the future. These are “ideal times” or “longed-for times,” past or future of which philosophers, writers or political men speak.

As part of a laboratory study of the hydrothermal alteration of kimberlite, a mass balance procedure has been developed for estimating the relative proportions of synthetic phyllosilicate phases— chlorite, vermiculite, smectite, kaolinite and serpentine—present in reaction products. The procedure is based on a combination of X-ray powder diffraction (XRD) measurements (for phase identification), atomic absorption determinations (for total Si, Al, Fe, and Mg) and published analyses of clay minerals (for stoichiometric deductions). It centers on the computer inversion of a 4 × 4 matrix form of four simultaneous equations representing the mass balance of Si, Al, Fe, and Mg in four chosen minerals and incorporates a systematic routine for selecting from all possible permutations of high and low estimates of the mineral chemical analyses acceptable sets of product stoichiometries and phase proportions consistent with the total metal analyses. To minimize uncertainties and computing time, the program takes account of elemental relationships and water mass balances associated with phyllosilicates. It also accommodates data relevant to poorly crystalline phases for which a range of theoretical type-analyses modeled on aluminum oxyhydroxides and 9–11-Å, 2:1 layered aluminosilicates are employed.

The procedure produces reliable trends in phase proportions consistent with the intensities of characteristic XRD peaks of clay minerals present in the analyzed mixture; for example, increases in estimated kaolinite proportions correspond with larger 7-Å (and other) peaks in analyzed samples. A precision of 7–25% has been routinely achievable.

Copper adsorption on a hydroxy-aluminum-hectorite complex (OH-Al-hectorite) at pH 4.5, 5.7, 7.4, and 7.8 was examined by means of electron spin resonance. The spectra of these samples were compared to those of Cu2+-hectorite and various aluminum hydrous oxides. Copper on the OH-Al-hectorite in aqueous gels occurred as mobile Cu(H20)62+ and chemisorbed to discrete sites of the OH-Al interlayer. As pH was increased, the ratio of chemisorbed to mobile Cu2+ increased. At pHs above 7 the solubility product of Cu(OH)2 was exceeded, but chemisorbed Cu2+ remained as the dominant species. These results contrast with the precipitation of Cu observed on microcry stalline gibbsite above pH 5 and indicate that the interlayer OH-A1 retained more Cu2+ on discrete sites. The greater adsorption capacity probably resulted in part from a higher specific surface area. Electron spin resonance spectra of Cu2+ in air-dried films of the OH-Al-hectorite at pH 4.5 and 7.4 showed Cu2+ in square planar symmetry, oriented with the z-axis perpendicular to the OH-Al-hectorite a-b plane. At the higher pH, the spectrum resembled that of Cu(OH)42- on alumina, suggesting a ligand exchange mechanism for Cu2+ adsorption on the complex.

Air-dried samples of homoionic Na-, Ca-, Al-, and Fe-smectite were equilibrated with 2,6-dimethylphenol vapor for 24 hr. Infrared spectra of the complexes formed indicated that a portion of the sorbed phenol was transformed into quinone-type compounds. Both sorption and transformation were greatly influenced by the nature of the exchangeable cation and followed the order Fe ≫ Al > Ca > Na. Changes in the electron spin resonance spectra of the clays following interaction with the phenol followed the same order, indicating that these reactions are enhanced by a transition metal cation, such as Fe3+, on the exchange complex. The reaction products from the clay complexes were extracted with methanol and identified using ultraviolet/visible spectrophotometry, high-pressure liquid chromatography (HPLC), and mass spectrometry. The extracts contained mixtures of products including the parent phenol, di-, tri-, and tetramers of the phenol, as well as quinone and quinone dimers. The identities of these compounds were further confirmed by the coincidence of the retention times of HPLC peaks obtained from extracts of the clays with those from compounds produced by oxidation of 2,6-dimethylphenol with Ag2O.

Several new minerals, structurally and chemically similar to the hydrotalcite-manasseite group, have been found in the saline deposits of the central pre-Caspian depression and in those of Middle Asia. Their structures consist of layers of (Mg1-xAlx)(OH)2 plus interlayers of anions and molecular water. In addition to manasseite itself, [(Mg4Al2)(OH)12][(CO3)-3H2O], having unit-cell parameters of a = 3.042, c = 2 × 7.56= 15.12 Å and a calculated density of Dc = 2.15 g/cm3, other varieties were identified whose interlayers contain alternately SO42− or SO42− and CO32− anions. The following new phases were recognized: (1) an 8.85-Å phase having the composition [(Mg4Al2)(OH)12][(SO4)·3H2O], subcell dimensions of a' = 3.04, c' = 8.85 Å, and Dc = 1.96 g/cm3; (2) an 11-Å phase having the composition [(Mg3.96Fe0.06Al1.98)(OH)12][Na0.56(SO4)1.30·7.3H2O], hexagonal unit-cell parameters of a = √3 · 3.042 = 5.28 Å, c = 11.16 Å, and Dc = 1.90 g/cm3; (3) a 16.5-Å mixed-layer phase having the composition [(Mg4Al2)(OH)12][(SO4)0.5(CO3)0.5·3H2O] and an ordered ABAB... alternation of 7.56-Å layers (i.e., a brucite-like layer + a CO32−-containing interlayer) and 8.94-Å layers containing SO42− anions in interlayers; this phase has unit-cell dimensions of a' = 3.05, c' = 16.5 Å and Dc = 2.06 g/cm3; and (4) an 18.5-Å ordered mixed-layer phase having the ideal composition [(Mg8Al4)(OH)24][M+0.5(SO4)1.25(CO3)1.0·9H2O] and an alternation of 7.56-Å, CO3-containing layers and 11-Å layers having SO42− anions and Na and Mg cations in interlayers (M+0.5 corresponds to interlayer cations). This last phase has unit-cell dimensions of a = 3.046, c = 3 × 18.54 = 55.62 Å and Dc = 1.99 g/cm3. Some of the varieties containing SO42− in the interlayers swelled with ethylene glycol or glycerol.

For this diverse family of minerals whose structures are based on brucite-like layers of the composition (R2+1-xR3+x)(OH)2, a unifying system of nomenclature is offered for consideration. In describing these brucite-like structures intercalated with anion- and cation-containing interlayers, the composition of the hydroxide sheet and the interlayers, the periodicity of the layers, and the mixed-layer nature of the material should be described. By means of symbols, a single term might be used to describe the crystal chemistry of any member of the group having a given cation composition for the brucite-like layers, for example, manasseite, a 2H polytype of hydrotalcite that has a repeat distance of 7.56 Å and CO3-containing interlayers, might be designated as 7.56-Å CO3-hydrotalcite-2H.

Smectites exchanged to various degrees with mono- or biprotonated 1,4-diazobicyclo(2,2,2)-octane (Dabco) have a porous structure in which the organic molecule acts as a “pillar.” Less Dabco2+ than Dabco1+ was necessary both to initiate and to complete expansion, whereas for both Dabco1+ and Dabco2+ the threshold for expansion increased with the charge density of the clay. Interstratification of 9.7-Å and 14.5-Å (Dabco1+) or 14.1-Å (Dabco2+) layers was observed before full expansion occurred.

Nitrogen sorption isotherms on partially exchanged Dabco1+- and Dabco2+-clays are of the BET II and Langmuir type respectively, whereas n-butane adsorbed according to BET type II for both cationic forms. The specific surface area was governed by the number of Dabcoz+ pillars, irrespective of the inorganic cation, and increased with Dabcoz+ content even beyond the composition where full expansion was reached and notwithstanding the increasing number of silicate layers in the c direction of the crystal units. This relationship is explained by an enhanced random interleaving of clay platelets in the stacking units containing Dabcoz+.

The rehydration properties of Ca-, Mg-, Na-, and K-saturated homoionic beidellites after heating at various temperatures were compared with those of montmorillonites. The behavior of interlayer Na+ during dehydration and rehydration was also investigated by means of one-dimensional Fourier analysis. The K- and Mg-saturated specimens exhibited fast and slow rehydration rates, respectively, during exposure to air of 50% RH after heating at 800°C. These homoionic specimens showed strong rehydration properties on saturation with deionized water after heating <900°C for 1 hr. On the basis of Fourier analysis, the interlayer cations appeared to have migrated into the hexagonal holes of SiO4 network on thermal dehydration, and the migrated cations returned to the interlayer space on rehydration. This behavior of the interlayer cations appears to have been strongly dependent on value of the octahedral negative charge and on the sizes of interlayer cations. The small octahedral negative charge of beidellite produced a weaker attractive electrostatic force between the octahedral sheets and the migrated interlayer cations. Therefore, the migrated interlayer cations in beidellite were easily extracted from the hexagonal holes, and rehydration was rapid. The small cation migrated easily into hexagonal holes and was fixed to the holes. On the contrary, large cations were probably difficult to fix and were easily extracted from the hexagonal holes. Consequently, the rehydration rate of K-saturated beidellite was fast, and that of Mg-saturated beidellite was slow.

The structures of 11 smectites and 2 interstratified mica/smectites containing mainly Ca2+ and Na+ as exchangeable cations in variable ratio were studied under a relative humidity of about 40%. Observed X-ray powder diffraction patterns were compared with diagrams calculated from interstratification models containing 15.2-Å Ca-smectite layers (C), 12.4-Å Na-smectite layers (N), and 10.0-Å mica layers (M) in various combinations. The smectites appear to be a random interstratification of component layers C and N, and display a tendency towards segregation. One of the interstratified minerals studied is a regular interstratification of C and M layers; the other is a regular interstratification of C, N, and M layers, in which N and C layers are randomly distributed in equal proportion and show a tendency towards segregation.

Activity expressions are presented for a six end-member, regular solution, site-mixing model for chlorites. The end members are ideal 14-Å chlorites for which experimental stability data are lacking. Estimates were made of the standard state 25°C and 1 bar molar 3rd law entropies, volumes, and the Maier-Kelley heat capacity coefficients. Experimental stability data from the literature for 14-Å chlorites were used with different sets of exchange energies, for cations on adjacent sites, to compute estimates of the standard state chemical potentials of the end members at 25°C and 1 bar. More experimental data are needed for an adequate definition of the exchange energies and the standard state chemical potentials. The model was applied to diagenesis in clastic reservoirs. Aqueous activity ratios of Mg2+:Fe2+ were computed as an equilibrium function of the corresponding molar ratios in authigenic chlorites. The aqueous activity ratio was independent of the chlorite Al content at a constant molar ratio of Mg2+:Fe2+ in the chlorite. The model predicts a wide range of molar Mg2+:Fe2+ ratios in authigenic chlorites in equilibrium with reservoir fluids. Trends in these molar ratios should be independent of the Al content in the chlorites. The model can be applied directly to 7-Å chlorites when experimental data become available to estimate the various thermodynamic parameters of the 7-Å end members.

Dans la Lettre sur les aveugles, Denis Diderot décrit, en se basant sur la physique mathématique, une méthode pour l’évaluation des hypothèses dans des situations où la certitude ne peut pas être atteinte. La thèse de cet article est que l'auteur de la Lettre étend cette méthode aux questions métaphysiques du finalisme et de l'idéalisme. Diderot présente les positions antagonistes de manière telle que la personne lisant le texte est invitée à peser et soupeser les arguments et à choisir celle qui lui paraît la meilleure, ou la plus probable.

Bhakti is a remarkable existential tendency that shows itself in the rich expanse of the tradition originating from the Vedas. Recognized as a prize possession of the religions, philosophies, and culture of India, it has often won fascination and admiration from students of Eastern heritage. However, its nature, role, and history remain misunderstood and have not received all the attention they deserve. Its role as a gatherer of life, love, thought, and the divine is missed in its partial characterizations as “Hindu devotion” or “divine love” or “theism implicit in polytheism.” Its status as a perennial thematic concept of the Indian civilization is missed when its pervasiveness is overlooked by the cultural historians preoccupied primarily with its periodic eruptions. Furthermore, the philosophical role of bhakti is missed when it is deemed as an alternative to jnana (knowledge) rather than “the living of jnana.”

Dimethylselenoxide (DMSeO) forms three structurally resolvable intercalates with kaolinite (d(001) = 10.95, 11.26, and 11.38 Å). The 11.26-Å kaolinite: DMSeO intercalate is structurally analogous to the 3-D ordered kaolinite: DMSO intercalate (d(001) = 11.22 Å). Infrared and solid-state 77Se nuclear magnetic resonance data indicate that all DMSeO molecules are equivalent in the structure and, therefore, that the 11.26-Å kaolinite: DMSeO intercalate structure is C-face centered. Structural model refinement from X-ray powder diffraction (XRD) data further support this conclusion (Pl, a = 5.195(2), b = 8.990(4), c = 11.946(5) Å, α = 91.33(2)°, β = 109.39(2)°, γ = 89.77(2)°). The kaolinite: DMSO intercalate structure was subsequently re-refined from the XRD profile in C-face centered Pl. The derived orientation of the DMSO and DMSeO molecules with respect to the basal plane of their respective intercalates is in agreement with polarized infrared measurements of the angles with ab of S=O (40.3°) and Se=O (38.8°) for the 11.26-Å intercalate. The locations of the organic molecules also agree with observed infrared band splittings and perturbations. Interatomic distances calculated from the band shifts agree with those for the XRD derived structures.

The 11.38-Å kaolinite: DMSeO intercalate is closely related to the 11.26-Å intercalate, the main differences being a 2-fold disorder in the orientation of the DMSeO molecule and less penetration of the kaolinite ditrigonal cavity by that molecule. The 10.95-Å kaolinite: DMSeO intercalate, displaying disorder parallel to [110], was obtained from the 11.26- or 11.38-Å intercalates by removal of some DMSeO.