The natural world is a frequent touchstone for the Swiss-born Austrian composer Beat Furrer. In the operatic work Violetter Schnee (2019), for instance, images of snow and coldness take on a central role. Other works, such as Wüstenbuch (2009) and the Spazio Immergente triptych (2015), refer more indirectly to notions of barren landscapes and ecological excess. At the basis of all these works are sentiments of slippage and loss, of far-reaching melancholia and an unrepairable detachment from reality. The composer's multi-layered use of repetition further underlines these sentiments and aids in the creation of constantly shifting sonic landscapes. This article argues that the recurrent use of nature imagery in Furrer's work signposts a latent ecological dimension in his oeuvre. In doing so, the article focuses on the slipperiness of musical repetition, and more particularly on the heavily destabilising power of the loop. Taking Violetter Schnee as the starting point for inquiry, and using Timothy Morton's philosophical project of ‘dark ecology’ as a heuristic framework, the article reads Furrer's recent work against the background of ecological critique.

The present study investigated the anisotropy in the orientation of particles in synthetic swelling clay media prepared from the sedimentation of particle-sized fractions of vermiculite. The different size fractions (<0.1, 0.1–0.2, 1–2, and 10–20 μm) were chosen because they represent the wide range of particle sizes of swelling clay minerals encountered in natural environments. Small-angle neutron scattering (SANS) and neutron diffraction measurements allowed the characteristic scattering/diffraction features to be derived and the quantitative information about the particle orientation distributions along two directions with respect to the sedimentation plane to be extracted. The results obtained confirmed that the increase in particle size was associated with the development of a random orientation for the particles, whereas the hydration state had a negligible impact on the organization of the porous media. For finer vermiculite particles, the rocking curves demonstrated an anisotropy of the systems that is similar to those reported previously on natural montmorillonite minerals. This result suggests that the location of the layer charge has little or no impact on the anisotropy features of particle orientation. For the coarsest fraction (10–20 μm), quantitative information about the particle orientation revealed that the relative proportion of the isotropic contribution represents up to 85% of the material. The anisotropy in the 2D SANS patterns revealed a pore-network anisotropy that was consistent with the particle size.

Clinoptilolite-rich materials from widespread pyroclastic and epiclastic deposits of northern Sardinia were investigated to assess their cation exchange properties and to find the most reliable experimental method to determine their cation exchange capacity (CEC). The CECs were evaluated using a cross exchange method (CEM) and a batch exchange method (BEM). The CEM resulted in values 30–35% lower than the theoretical or expected CEC calculated from the chemical analyses of the clinoptilolite-rich materials. The BEM resulted in CECs 6–12% lower than the expected CECs. Various parameters, such as the grain-size of powders (<64 µm and 125–250 µm) and replacement cation (Na+, K+, Li+, Cs+, NH4+, Ca2+, Mg2+, Sr2+) were evaluated in order to optimize the cation exchange process, i.e. enhance complete exchange. The particle size did not affect the exchange process appreciably. The type of replacement cation had a substantial effect on the experimental CEC determined by the BEM. The NH4+ and Cs+ replacement solutions resulted in the best experimental CECs ranging between 75% and 94% of the theoretical CEC with NH4+ as the replacement cation and 79% and 88% of the theoretical CEC with Cs+ as the replacement cation. The exchange efficiency was also measured as a function of ammonium concentration in the replacement solution (0.50, 1.00, 2.00 and 3.00 M). Experimental CECs ranged between 94% (0.5 M NH4Cl solution) and 99% (1 M NH4Cl solution) of the theoretical CEC for one epiclastic rock sample and between 79% (3 M NH4Cl solution) and 87% (2 M NH4Cl solution) of the theoretical CEC for one pyroclastic rock sample.

A detailed structural characterization of organo-clays is a key in understanding their properties. In this work, mono-, di-, tri-, and tetra-butylammonium (nBA; n = 1–4) cations intercalated in the layered clay mineral montmorillonite (Mnt) have been studied for the first time by combining a theoretical approach based on density functional theory (DFT) and infrared spectroscopy. The DFT calculations revealed the detailed structure and position of nBA cations in the interlayer space. A relation between the basal spacing (d001 parameter) and the cation size and structure was found, and explained with respect to the structure, composition, and size of the organic cations. Hydrogen bonds between -NHx/-CH3/-CH2 groups of the nBA cations and oxygen atoms of the basal planes of the Mnt layers were found to be an important factor for the arrangement and energetic stabilization of cations in the interlayer space. The N-H-O hydrogen bonds are stronger than C-H-O hydrogen bonds and the stabilization decreases with decreased number of bands. Analysis of DFT-calculated vibrational modes helped in understanding a problematic region of the experimental infrared spectra (4000–3000 cm-1), in which assignment of all vibrational modes unambiguously was not possible because of a significant overlap of broad bands.

Tumor theranostics (a portmanteau of therapeutics and diagnostics) is now achieved in various ways with complex nanoparticle systems. Layered double hydroxide (LDH) nanoparticles are effective at drug/gene delivery and as imaging agents in potential tumor theranostics. This mini-review paper summarizes recent progress in developing LDH nanoparticles as a pH-sensitive magnetic resonance imaging (MRI) contrast agent, as a positron emission tomography (PET) imaging agent, and as a co-delivery platform for two therapeutic agents for tumor diagnosis and therapy. These results have indicated clearly the potential application of LDH nanoparticles for simultaneous diagnosis and treatment of cancers.

Caliche in various forms, namely powdery, nodule, tube, fracture-infill, laminar crust, hard laminated crust (hardpan), and pisolitic crust, is widespread in the Mersin area in southern Turkey. It generally occurs within and/or over the reddish-brown mudstone of the Kuzgun Formation (Tortonian, Miocene) and alluvial red soils of the Quaternary. The mineralogical distribution along representative caliche profiles was examined by X-ray diffraction, scanning electron microscopy, differential thermal analysis-thermal gravimetry, and chemical techniques. Calcite is the most abundant mineral associated with minor amounts of palygorskite in caliche samples, whereas smectite is prevalent mainly in the reddish-brown mudstone and alluvial red soils of the caliche parent materials and is associated with appreciable amounts of palygorskite. These minerals are also accompanied by trace amount of illite, quartz, feldspar, and a poorly crystalline phase. Palygorskite fibers and fiber bundles were developed authigenically on euhedral or subhedral calcite crystals of the caliche units and at the edges of smectite flakes in the caliche host-rocks or sediments. Intense, continuous evaporation of subsurface soil-water resulted in an increase in pH and the dissolution of detrital smectite within the red mudstones and alluvial red soils that enclose the isolated caliche forms, and caused an increase in the Al+Fe and Mg/Ca ratio, favoring the formation of palygorskite under alkaline conditions. The calcium required for caliche formation may have originated from eolian dust, detrital carbonate minerals, and/or other caliche materials, which are dissolved by carbonic acid.

Polarized micro-Raman spectra of a single large crystal of Keokuk kaolinite were recorded in the OH-stretching region with the laser beam directed along the different crystal axes. The Raman spectra are characterized by five OH-stretching bands at 3694, 3683, 3668, 3650 and 3620 cm−1 labeled A, Z, B, C and D, respectively. The relative intensities of these five bands depend on the orientation of the crystal and the scattering geometry. The spectra agree with the assertion that bands A and Z arise from out-of-plane vibrations, whereas band D corresponds to an in-plane vibration. The area ratios of the various bands were calculated from fitted curves of spectra recorded with the electric vector of the laser beam parallel to different crystallographic planes. The increments in the relative areas of bands B and C were parallel to those of bands A and Z and it appears that out-of-plane vibrations made considerable contributions to these bands also. From the change of area ratios with the change in the direction of the electric vector of the laser beam, bands A and Z were attributed to LO and TO frequencies of one inner-surface hydroxyl vibration. Bands A + Z, B, C and D were attributed to the vibrations of the hydroxyls assigned by Bish (1993) as OH(3), OH(4), OH(2) and OH(1), respectively. These observations were supported by photoacoustic and transmission IR spectra.

Electro-osmotic chemical treatment is an innovative method to improve the strength of soft clays for geotechnical engineering purposes; the effectiveness of the treatment may be related to treatment time, the concentration of the solutions injected, and to variation of pH in the clay. The objective of this study was to investigate the relationship between the above-mentioned factors and the improvement in strength when calcium chloride solution was used as an injection material. A series of tests was carried out by injecting different concentrations of calcium chloride solution into a kaolin suspension, for different treatment times, during electro-osmosis. After the tests, the pH, cone resistance, water content, and concentration of Ca2+ in the kaolin at different locations were measured and analyzed. The results show that the concentration of Ca2+ in the kaolin, the pH, and the strength were increased near the cathode with increases in concentration of CaCl2 and treatment time. An insignificant increase in strength, due to ion exchange over the entire specimen, for short treatment times of 2 to 24 h, was observed because of a small increase in concentration of Ca2+ and in pH. During long-term treatment (120 h), a considerable increase in concentration of Ca2+ (137.0 mg/g) and pH (pH = 10) was observed near the cathode. This led to a pozzolanic reaction, which in turn caused a significant increase in the mechanical strength of the kaolin.

The hydrogen isotopic composition (δ2H) of authigenic clay minerals has been used extensively in paleoclimate studies. The separation of clay minerals from sediments/soils, using various chemicals, is a prerequisite for isotope ratio measurements, where carbonate, Fe-(oxyhydr)oxides, and organic matter are removed successively from the sediments for a greater clay yield. The commonly adopted organic matter-removal method using hydrogen peroxide (H2O2) is thought to either alter directly the pristine δ2H values of the smectite clay minerals or to introduce organic hydrogen-bearing impurities through the ineffective removal of organic matter. The objective of the present study was to test whether H2O2 treatment can alter the δ2H values of kaolinite (Kln) by comparing two organic matter-removal methods, namely, H2O2 and disodium peroxodisulfate (Na2S2O8) combined with a neutral buffer. In doing so, kaolinite-rich, old (~56 Ma) sediment samples and pure kaolinite internal laboratory reference materials were used to understand the effectiveness and suitability of the above-mentioned methods in clay-sample preparation for δ2H measurements. The δ2H values of the H2O2-treated aliquots show smaller δ2H values than those for the Na2S2O8-treated aliquots. Estimated ambient water δ18O values (−4‰) from the Na2S2O8-treated aliquots agreed well with the bio-phosphate (fish vertebrae) based environmental water δ18O estimation (−3.3‰). The present study indicated, therefore, that δ2H values obtained after Na2S2O8 treatment are likely to be more realistic for paleoclimate reconstruction.

A wick structure is the core part of a heat pipe that produces capillaries to move liquid from a condenser to an evaporator. The purpose of the current study was to develop a wick structure from zeolite and kaolin using various sintering methods. Due to significant porosity and water-adsorption properties, zeolite and kaolin can produce a large capillary force inside the heat pipe. A porous wick specimen is developed from pure zeolite together with a mixture of zeolite and kaolin by using pressureless (loosely packed) and conventional pressurized sintering for thermosiphon heat-pipe applications. Major properties such as porosity, water adsorption, and permeability were noted to be better under pressureless sintering compared to pressurized sintering. Significant and uneven shrinkage in both radial and linear directions is a major problem in loosely packed sintering of pure zeolite. However, the addition of kaolin helps to overcome the problem of porosity and shrinkage in pure zeolite; but the permeability and strength of the wick structure are reduced with the addition of kaolin. A general trend is that increasing porosity causes increasing permeability. Due to grain size and compaction, however, permeability is reduced with the addition of kaolin. Based on the experimental results for porosity and permeability, the wick structure formed from zeolite with 5–10% of kaolin has better thermal properties for heat-pipe applications.

The crystal structure of cronstedtite-2H2 was refined in a hexagonal cell, space group P63, Z = 2, using two acicular crystals from Wheal Maudlin, Cornwall, England, and from Pribram, Czech Republic. The Wheal Maudlin sample has the chemical composition $\left({\text{Fe}}_{2.291}^{2+}{\text{Fe}}_{0.709}^{3+}\right)\left({\text{Si}}_{1.298}{\text{Fe}}_{0.707}^{3+}{\text{Al}}_{0.004}\right){\text{O}}_5{\left(\text{OH}\right)}_4$ and the Příbram sample has the composition $\left({\text{Fe}}_{2.269}^{2+}{\text{Fe}}_{0.731}^{3+}\right)\left({\text{Si}}_{1.271}{\text{Fe}}_{0.724}^{3+}{\text{Al}}_{0.005}\right){\text{O}}_5{\left(\text{OH}\right)}_4$. The results of refinements are as follows: a = 5.500(1), c = 14.163(2) Å, V = 371.08(8) Å3, R = 3.83%, from 381 independent reflections, and a = 5.4927(1), c = 14.1481(2) Å, V = 369.70(4) Å3, R = 4.77%, from 1088 independent reflections for the Wheal Maudlin and Příbram samples, respectively. The best Fovs.Fc agreement was achieved when the structure was interpreted as merohedral twin; several possible twinning laws are discussed. The cronstedtite layer consists of one tetrahedral sheet and one octahedral sheet. There is one octahedral (M1) position, occupied by Fe only, and two tetrahedral (T1, T2) positions in the structure. Refinement of occupancy of tetrahedral sites led to values Si:Fe = 0.45:0.55(1) (Wheal Maudlin) and 0.432:0.568(8) (Příbram) in T1, and Si: Fe = 0.99:0.01(1) (Wheal Maudlin) and 0.888:0.112(7) (Příbram) in 72. Whereas the size of T1 is reasonable (average dT1-O = 1.693 Å (Wheal Maudlin), 1.691 Å (Příbram)), T2 is unusually large: (dT2-O= 1.740 Å (Wheal Maudlin), 1.737 Å (Příbram)) with respect to the small or almost zero Fe content. As an explanation, an alternative structure model comprising a certain amount of vacancies in T2 is presented. The tetrahedral rotation angle α is highly positive (+12.1° and +12.5° for the Wheal Maudlin and Příbram samples, respectively), and the layer belongs to the Franzini type A. Distortion parameters of octahedra and tetrahedra are given for both samples. One hydrogen atom engaged in the hydrogen bond was located in the Wheal Maudlin sample.

The ability of hydrotalcites to retain anionic wastes was studied. In particular, Cr(VI)-adsorbed hydrotalcites were heated to immobilize Cr(VI) in the solid sample. When the heating temperature increased up to 500°C, the lamellar structure of hydrotalcite was lost. At high temperatures (1200°C), the solids were recrystallized in the form of a spinel. Lixiviation with 1 N and 5 N NaCl solutions were utilized to simulate the effect of sea water and of concentrated NaCl solutions in salt mines on the immobilization of Cr. Radiation damage on the solid containing the immobilized Cr was studied by γ-irradiating with a 60Co source at 1000 and 6000 kGy. The Cr-containing samples heated at 1200°C, whether irradiated or not, safely immobilized Cr in the hydrotalcite mainly in the form of MgCr2O4 spinel. Irradiation of hydrotalcites revealed two different effects: (1) samples heated up to 1200°C evolved as a solid in which chromium was retained more firmly than in the non-irradiated material, irradiation enhancing the spinel formation; (2) the structure of samples heated at 1200°C developed a preferential crystallite orientation rather than a purely random one or new location of chromium ions, this effect did not affect Cr immobilization in the solid. Chromium lixiviation with 5 N NaCl solution was always less than the corresponding value with 1 N NaCl solution, probably due to the poor mobility of Cl− ions in the highly concentrated NaCl solution.

The objective of this study was to explore the geological origin of glauconite, which is believed to precipitate and mature very slowly (~1 Myr) in neritic environments (shallow water, oceanic coastal zones, at water depths of 100–200 m) with very low sedimentation rates. A series of simulation experiments was designed and carried out in sealed tubes placed in an oven and heated to a constant temperature of 50°C (±2°C) for 60 or 150 d. The parent materials used for these experiments were two low-Fe montmorillonites with different crystallinities. The montmorillonites were introduced to solutions with concentrations of 0.02–0.1 mol/L Fe3+ and 0.05–0.2 mol/L K+ with various values of pH and Eh. The products were analyzed using X-ray powder diffraction (XRD), Fourier-transform infrared (FTIR) spectrometry, electron spin resonance (ESR) spectrometry, scanning electron microscopy (SEM), and Mössbauer spectroscopy. The morphological changes from parent material to product were observed under SEM, which revealed the formation of a flaky mineral (e.g. a product formed in the interstitial spaces between montmorillonite crystals). The formation of a flaky mineral indicates that the product is a layer silicate. Qualitative analysis of XRD patterns revealed that the main product phase was a mica group mineral and the d060 value was consistent with the presence of glauconite (0.152 nm) and/or Fe-illite (0.150 nm). A glauconite and Fe-illite mineral assemblage formed in a weakly acidic solution, while Fe-illite, mixed-layer Fe-illite, and montmorillonite formed in neutral and alkaline solutions. Stretching vibrations of Fe(III)Fe(III)OH-AlFe(II)OH and/or MgFe(III)OH were observed in FTIR spectra (3550–3562 cm−1) of the products formed in acidic solutions, which along with the g = 1.978 ESR signal indicated that Fe(III) entered octahedral positions in the tetrahedral/octahedral/tetrahedral layer (TOT) platelets. The AlFe(II)OH-MgFe(III)OH (3550–3562 cm−1) and AlFe(III)OH (870 cm−1) vibrations were only observed in products formed in neutral and alkaline solutions. Analysis of the Mössbauer spectra showed that Fe(III) substituted for Al and Mg in the cis octahedral sites of montmorillonite. The simulation experiments demonstrated that the pH and redox conditions (Eh) of the environment controlled the nature of the product mineral species. Results of the present study revealed that glauconitization and illitization occurred under different conditions, where glauconitization preferentially occurred in an acidic environment and illitization preferentially occurred in a nearly neutral to alkaline environment.

X-ray diffraction shows that ordered interlayer structures form when high-charged Llano vermiculite is reacted with HDTMA-Br or HDTMA-acetate, but the structures differ from those given by low-charged vermiculites. The differences arise in two ways; firstly when both HDTMA+ cations and HDTMA-Br (or -acetate) ion pairs are present as interlayer guest species, a superstructure forms which is less commensurate with the host structure of high-charge vermiculite than it is for lower-charged material. Secondly, although a commensurate 3a × b interlayer superstructure forms when HDTMA+ cations are the only interlayer guests, an increasing number of charge-balancing cations must be accommodated as the layer charge increases. This results in some structural disorder which is only observed in the diffraction pattern of HDTMA+-intercalated, high-charge vermiculite. Organic ion pairs tend to order along widely spaced rows corresponding to the intersections of two sets of scattering planes. For the acetate form, one set of planes has spacings of 3.52 Å, but for the bromide form the value is 3.67 Å. Scattering planes in the second set have spacings of 4.02 Å, independently of counter-anion size. These two sets of planes diverge from one another by ∼10°. Ordering is more apparent in the presence of acetate anions than it is for the smaller Br− anions. In the high-charged intercalates, from which organic ion pairs have been removed, HDTMA+ cations occupy positions on a centered two-dimensional superlattice and also randomly, some interstitial positions as necessitated by layer charge.

Diagenesis of the Holocene-Pleistocene volcanogenic sediments of the Mexican Basin produced, in strata of gravel and sand, 1H2O- and 2H2O-smectite, kaolinite, R3-2H2O-smectite (0.75)-kaolinite, R1-2H2O-smectite (0.75)-kaolinite, R3-kaolinite (0.75)-2H2O-smectite and R1-1H2O-smectite (0.75)-kaolinite. Smectite platelets were formed from volcanic glass by loss of Si4+. Partially-formed platelets have Si4+ between 4.55−4.10 a.p.f.u., Mg+Mn and the interlayer charge are relatively uniform while VIAl+Fe3++Ti varies between 0.98 and 1.63 a.p.f.u. Almost fully transformed platelets have Si4+ of 4.08−4.04 a.p.f.u.; Mg+Mn and the interlayer charge decrease proportionally to increasing VIAl+Fe3++Ti. Smectite-kaolinite mixed layers have octahedral occupancies of 2.01–2.15 a.p.f.u., IVAl3+ 0.09–0.55 a.p.f.u. and interlayer charges about half that of smectite; structural formulae corresponding to smectite (0.75–0.80)-kaolinite indicate octahedral occupancy of 2.50 a.p.f.u., tetrahedral replacement 0–0.31 a.p.f.u., and interlayer charge 0.24–0.51 equivalents, some indicating interstratifications of beidellite. Kaolinite is presumed to have formed from K-feldspar; smectite-kaolinite interstratifications sustain the transformation of kaolinite to smectite in an increasingly siliceous high-cation environment. In the mudstones of low-hydraulic conductivity and practically stagnant alkaline fluids, glass was transformed to 2H2O-smectite lamellae of IVAl between 0 and 0.47 a.p.f.u., octahedral occupancy 1.70–2.00 a.p.f.u. and interlayer charge of 0.23–1.21 equivalents, some corresponding to beidellite. The interlayer charge increases with IVAl and decreasing occupancy of the octahedral sheet; the abundance of Mg+Mn is inverse to that of VIAl+Fe3++Ti.

Clay suspensions containing 1H2O- and 2H2O-smectite, kaolinite and R3-2H2O-smectite (0.75)-kaolinite lead to low-energy edge-to-edge particle associations, non-Newtonian pseudoplastic behavior, and maximum apparent viscosity of 180 Pa s at 0.008 s−1 followed by rapid descent. Clay fractions with slightly larger 2H2O-smectite contents and smaller kaolinite contents reach maximum viscosity of 3611 Pa s at a shear rate of 0.0018 s−1 and of 3300 Pa s at 0.0024 s−1. They denote two high-energy face-to-face particle associations, followed by slow descent of the apparent viscosity under viscous flow. Suspensions change from elastic to viscous behavior at shear stresses of 1.03 and 5.91 Pa, respectively. Clay suspension vibrated at a frequency of 1 Hz develops a shear storage dynamic modulus greater than the shear dynamic loss modulus or the energy is preferentially stored, whereas at 5 Hz more energy is dissipated than stored.