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Electrical conductivity in non-polar media is a subject which recently regained interest. If most of experiments and theoretical developments were done more than 50 years ago, new experiments and theories have been recently published. As the electrical conductivity describes, at low field, the equilibrium state of a system, it is natural to apply theories based on equilibrium thermodynamics. In this article, well-established classical thermodynamics and solvations models are applied to recently published data. This enables to get a new insight in intriguing phenomena, such as the linear dependence of the conductivity on the concentration of ionic surfactant and the evaluation of conductivity for the mixture of two miscible fluids, such as alcohol and alcane, which have very different conductivities. [ABSTRACT FROM AUTHOR]

In the framework of irreversible thermodynamics, we show that the sedimentation current in electrolyte solutions is mathematically equivalent to the low frequency limit of the ionic vibration current, appearing in the presence of an acoustic wave. This non-trivial result is obtained thanks to a careful choice of the reference frame used to express the mass fluxes in the context of electroacoustics. Coupled transport phenomena in electrolyte solutions can also be investigated in a mechanical framework, with a set of Newtonian equations for the dynamics of charged solutes. Both in the context of sedimentation and of electroacoustics, we show that the results obtained in the mechanical framework, in the ideal case (i.e., without interactions between ions), do satisfy the Onsager's reciprocal relations. We also derive the general relation between corrective forces accounting for ionic interactions which must be fulfilled so that the Onsager's reciprocal relations are verified. Finally, we show that no additional diffusion term needs to be taken into account in the flux of solutes (far from the walls), even if local concentration gradients exist, contrarily to what was done previously in the literature. [ABSTRACT FROM AUTHOR]

In electrolyte solutions, an electric potential difference, called the Ionic Vibration Potential (IVP), related to the ionic vibration intensity, is generated by the application of an acoustic wave. Several theories based on a mechanical framework have been proposed over the years to predict the IVP for high ionic strengths, in the case where interactions between ions have to be accounted for. In this paper, it is demonstrated that most of these theories are not consistent with Onsager's reciprocal relations. A new expression for the IVP will be presented that does fulfill the Onsager's reciprocal relations. We obtained this expression by deriving general expressions of the corrective forces describing non-ideal effects in electrolyte solutions. [ABSTRACT FROM AUTHOR]

In this article, the relations for electroacoustic phenomena, such as sedimentation potential, sedimentation intensity, colloid vibration potential, colloid vibration intensity/current, or electric sonic amplitude, are given, on the basis of irreversible thermodynamics. This formalism allows in particular to discuss the different expressions for concentrated suspensions found by various authors, which are of great practical interest. It was found that some existing expressions have to be corrected. Relations between the electrophoretic mobilities assessed by the different experiments are derived. [ABSTRACT FROM AUTHOR]

• Flocculation can be studied applying logistic growth models. • These models reduce to well-known linear interpolations at onset of flocculation. • Studies of flocculation kinetics can be performed over long periods of time. • The dependence on relevant parameters is discussed. The model based on logistic growth theory, that was introduced in Chassagne, Claire, and Zeinab Safar. "Modelling flocculation: Towards an integration in large-scale sediment transport models." Marine Geology 430 (2020): 106361 , can be used to model the time evolution of either the particle (floc) size or the concentration of particles of a given size. In the present article, we show how this model can easily be linked to the many studies performed over the years about the flocculation kinetics at the onset of flocculation experiments. Flocculation experiments done on kaolinite suspensions destabilized by addition of salt are used as examples. Both perikinetic and orthokinetic flocculation are considered. By fitting the experimental data over the whole experiment period, it is shown that the floc size L (t) time evolution follows the relation dL / dt = L / t b − L 2/(L eq t b) where t b is a characteristic time and L eq a characteristic size, which are obtained from the fits. [ABSTRACT FROM AUTHOR]

In a colloidal suspension, one can generate sound waves by the application of an alternating electric field (Electrokinetic Sonic Amplitude, i.e., ESA). Another phenomenon is electrophoresis (Electrophoretic Mobility, i.e., EM) where a colloidal particle moves relative to the solvent in an electric field. Vice versa one can generate electric fields or electric currents by sound waves (Colloid Vibration Potential/Current, i.e., CVP/CVI). In 1988 and 1990, O'Brien [J. FluidMech. 190, 71-86 (1988) and J. Fluid Mech. 212, 81-93 (1990)] derived a reciprocal relation between the proportionality coefficients of the EM and CVI phenomena. In this paper, we will generalize his proof by constructing the relevant entropy production from which the linear force-flux relations follow. General relations are derived for electrolyte solutions, of which colloidal suspensions are a particular case. The relations between CVI, CVP, EM, and ESA are discussed. O'Brien's reciprocal relation then follows as an Onsager relation. The relation is valid for any applied electric field frequency, particle surface charge and particle concentration (even in the presence of particle-particle interactions) provided the system is isotropic. [ABSTRACT FROM AUTHOR]

We previously proposed (Gourdin-Bertin, S. and Chassagne, C. J. Chem. Phys. 2016, 144 (24)) a simple theoretical model to account for the evolution of conductivity with dielectric permittivity in nonpolar media. In this article, we validate the theory experimentally for the case of an ionogenic species kept at a constant chemical potential (i.e., in equilibrium with a nondissolved salt, in contrast to previously published conductivity measurements carried out as a function of various fully dissolved salt concentrations). To our knowledge, it is the first time that this type of experiment has been performed explicitly. [ABSTRACT FROM AUTHOR]

The low-frequency dielectric spectroscopy of granular material, where the porosity is representative for sands and sandstones, is until now always modeled using theories based on the work of Schwartz (1962). The theory for the low-frequency dielectric spectroscopy of suspensions, on the other hand, has been developed much further over the last decades both numerically and analytically. In this article new analytical expressions for the complex conductivity of granular material, such as sands and sandstones in an electrolyte solution, are presented. These expressions have been derived using the theories developed for suspensions. We show that the new expressions enable to predict the measured complex conductivity of various granular material, such as packed glass beads, sands and sandstones. Because of the typical grain size of sand and sandstone particles, for any ionic strength the double layer is much thinner that the particle size. Contrary to existing theories for granular materials, the expressions we derived are valid for any ionic strength and no adjustable parameters are required. The grains are represented by monodispersed charged spheres. We also discuss how the expressions can be adapted in the case the particles are not spherical and the grains are polydisperse. [ABSTRACT FROM AUTHOR]

In the present article two flocculation models, given in [5] (LG model) and [36] (S model) are compared. Both models give the time evolution d L / d t where L is the size of a particle undergoing flocculation, and t is the time. The LG model is based on logistic growth theory, whereas the S model is based on the theory originally derived by Smoluchowski. Both models have the advantage of easy implementation in, for instance, large-scale sediment transport numerical models. However, it is found that they do not obey the same kinetics. A series of laboratory experiments is presented where the flocculation of a mineral clay by polyelectrolyte is studied as a function of clay concentration and shear rate. From modelling these experiments, it is found that the LG model reproduces the time dependence of the floc sizes found experimentally, whereas the S model does not. It is shown that the LG model can be used to model the data over the whole range of clay concentration and shear investigated. Based on the study presented in this article, it was found that the average floc growth in time for the clay type and conditions applied in the experiments could be modelled by: d L / d t = 40 × 1 0 − 4 G 0. 75 × [ e x p (− 2 × 1 0 − 4 G 0. 75 t) ] / [ 1 + 20 e x p (− 2 × 1 0 − 4 G 0. 75 t) ] L. • Logistic growth theory is compared with Smoluchowski-based theory. • The models do not have the same kinetics. • Only logistic growth theory agrees with experiments. • Logistic growth theory models data for all clay concentrations. • Logistic growth theory models data for all shears investigated. [ABSTRACT FROM AUTHOR]

The hydrodynamic size and electrophoretic mobility of sulfate latex nanospheres are given as a function of ionic strength for KCl and MgCl2 and at different volume fractions. The results were obtained from Doppler velocimetry and Dynamic Light Scattering using a Malvern ZetaSizer Nano (ZetaNano) at 173° scattering angle and a Malvern ZetaSizer 3000HSA (Zeta3000) at 90° scattering angle. Although the instrumentation is similar, we observed differences in the hydrodynamic radii. The reason for these discrepancies are most probably due to the conversion of the detected light intensity into particle radius since the particles have a diameter of about 530nm (measured by TEM) quite close to the lasers’ wavelength (633nm). From the study, we found in particular that the hydrodynamic radius decreases upon addition of monovalent or divalent salt. This behavior is generally attributed to the presence of a hairy layer on the particle's surface. We also found that the electrophoretic mobility decreases logarithmically with increasing particle concentration, as predicted for nearly salt-free conditions. The change in viscosity at higher ionic strength and the shift in the shear plane position are shown to play a role in the aggregation behavior. [ABSTRACT FROM AUTHOR]

Highlights: [•] The dipole coefficients of kaolinite and montmorillonite are reported. [•] They are independent on volume fraction in the range [0–20]% and [0–0.5]%, respectively. [•] The theory for non-spherical particles fits the data. [•] The relaxation frequency is determined by the relaxation of the double layer. [ABSTRACT FROM AUTHOR]

Highlights: [•] We report the electrokinetic response of montmorillonite particles. [•] The relaxation frequencies shifted to lower frequencies with decreasing ionic strength. [•] This shift is in qualitative agreement with the model’s prediction. [•] We need a Stern layer conductance to fit the amplitude of the dipole coefficients. [•] The quantitative deviations are due to the limitation of the theory. [ABSTRACT FROM AUTHOR]

We derived the so-called standard set of electrokinetic equations in prolate spheroidal coordinates for all ionic strengths, zeta potentials, and applied electric field frequencies, with the assumption, however, that the particle's electrophoretic mobility is small. We subsequently solved these equations using finite differences methods. We show that the dipolar coefficient of a prolate spheroid reduces to that of a sphere in the corresponding limit, but deviates strongly from it when the eccentricity of the spheroid is large, for the same particle volume. We also verified that a previously published analytical theory (Chassagne and Bedeaux, J. Colloid Interface Sci., 326:240, ) is in good agreement with the numerical results for a large range of zeta potentials, ionic strengths, and frequencies. [ABSTRACT FROM AUTHOR]

Abstract: In this article a new formula for the electrophoretic mobility of a spheroidal colloid is given. This formula and the formula presented in Chassagne and Bedeaux [C. Chassagne, D. Bedeaux, J. Colloid Interface Sci. 326 (2008) 240–253] for the dipolar coefficient of a spheroidal colloid are intertwined. The combination of electrophoresis and complex conductivity measurements (from which the dipolar coefficient can be derived) allows to assess both the zeta potential and the Stern layer conductance. We will in particular show that the values found for the zeta potential from both techniques are similar in the case of the kaolinite suspension studied. Electrophoretic mobility data are also presented and discussed for a wide range of ionic strengths, different types of salt and various pH. This data has been used in flocculation studies on the same kaolinite samples [F. Mietta, C. Chassagne, J.C. Winterwerp, J. Colloid Interface Sci., accepted for publication, doi:10.1016/j.jcis.2009.03.044]. [Copyright &y& Elsevier]

Abstract: The relation between the electrokinetic charge of kaolinite particles and their flocculation behavior has been investigated over a wide range of pH and added salt (for and NaCl salts). All flocculation experiments have been done with a mixing jar (sediment volume concentration ). The electrokinetic charge of particles in different suspensions has been assessed by electrophoresis while laser diffraction has been used to measure the floc size distribution. Mixing jar experiments can be successfully used to investigate the flocculation behavior of kaolinite at shear rates higher than or equal to , which is the shear rate used in the experiments. At lower shear rates, the floc size distribution is affected by particle settling. The electrophoretic mobility of kaolinite decreases in absolute value when the pH of the suspension decreases. This is reflected in an increase of both floc size and flocculation rate: the floc size at pH 4 is three times larger than at pH 7 and the flocculation time is one order of magnitude smaller (from 1000 to 100min). When the ionic strength of the suspension is increased, the electrophoretic mobility and the mean floc size display the same variations. On addition of NaCl (pH 9) both the electrophoretic mobility and the floc size display an optimum around 1mM of added salt, a feature that has been observed by other authors as well. The equilibrium floc size for a suspension (A) at 1M of added NaCl and pH 9 is the same as for a suspension (B) at pH 2 with no added salt. However, the time needed to reach the equilibrium for suspension (A) is one order of magnitude larger than for suspension (B). This is due to edge-face Coulombic attraction in suspension (B). The equilibrium floc size obtained by addition of or sea salt at pH 9 is similar to the size obtained by addition of NaCl. The flocculation rate for a suspension with added is higher than for suspensions with other added salts. [Copyright &y& Elsevier]

Abstract: In this article, we present a theory for the dielectric behavior of a colloidal spheroid, based on an improved version of a previously published analytical theory [C. Chassagne, D. Bedeaux, G.J.M. Koper, Physica A 317 (2003) 321–344]. The theory gives the dipolar coefficient of a dielectric spheroid in an electrolyte solution subjected to an oscillating electric field. In the special case of the sphere, this theory is shown to agree rather satisfactorily with the numerical solutions obtained by a code based on DeLacey and White''s [E.H.B. DeLacey, L.R. White, J. Chem. Soc. Faraday Trans. 2 77 (1981) 2007] for all zeta potentials, frequencies and where κ is the inverse of the Debye length and a is the radius of the sphere. Using the form of the analytical solution for a sphere we were able to derive a formula for the dipolar coefficient of a spheroid for all zeta potentials, frequencies and . The expression we find is simpler and has a more general validity than the analytical expression proposed by O''Brien and Ward [R.W. O''Brien, D.N. Ward, J. Colloid Interface Sci. 121 (1988) 402] which is valid for and zero frequency. [Copyright &y& Elsevier]

Abstract: Electrically induced birefringence experiments were performed on dispersions consisting of sulfate latex nanospheres of two different sizes and charges dispersed in an electrolyte solution, at various ionic strengths. The induced birefringence was found to have an important contribution increasing as a quadratic power law of the volume fraction of the spheres. This shows that interparticle interactions play a role in the observed birefringence. The data were analyzed, using a theory from Hafkenscheid and Vlieger [Physica 75 (1974) 57], in terms of the changes of the interparticle separations in the directions parallel and perpendicular to the applied electric field. [Copyright &y& Elsevier]

We consider an asymmetric electrolyte between two cylindrical concentric electrodes that are uncharged in the absence of an applied voltage difference. We calculate the dielectric response of this capacitor to an alternating voltage difference. The problem is solved using both classical boundary conditions and the new boundary conditions using excess densities to describe the charge build-up near the condensator plates as given in a previous article (C. Chassagne, D. Bedeaux and G.J.M. Koper, Colloid Surf. A 210 (2002) 137.). We verify that both boundary conditions give the same results. The advantage of the new boundary conditions lies in the possibility to extend in the future the analysis to real electrodes including reactions and specific ion adsorption. A comparison of the model predictions, involving no adjustable parameters with experimental dielectric spectroscopy data, is performed and excellent agreement is found. [Copyright &y& Elsevier]

In a previous article (C. Chassagne, D. Bedeaux, G.J.M. Koper, Physica A, to be published) an analytical expression for the dipolar coefficient of a charged sphere in an electrolyte was derived as a function of the frequency which is valid for all double layer thicknesses both for low and for high zeta potentials. In order to access the whole range of zeta potentials an interpolation formula is derived and tested. It is concluded that for the systems for which experimental information is available the expression for high zeta-potentials is sufficient. [Copyright &y& Elsevier]

Using a method introduced by Albano et al. (Physica A 99 (1979) 293 and Physica A 102 (1980) 105) based on the concept of excess densities in the sense of Gibbs, and excess fluxes, an analytical expression for the frequency-dependent dipolar coefficient of a charged sphere in a electrolyte valid for all double layer thicknesses for low and high zeta potentials is derived. The found expression is compared to the analytical formulae of Fixman, Hinch et al. and O''Brien in their range of validity and to the numerical simulation of Mangelsdorf and White. [Copyright &y& Elsevier]

An extension of the model for electrode polarization of Cirkel et al. [Physica A 235 (1997) 269] is given. The problem is solved using both classical boundary conditions and the new boundary conditions using excess densities presented in a previous paper [J. Phys. Chem. B 105 (2001) 11743]. In the present paper, the electrodes are supposed to be ideal, meaning that charge transfer or adsorption are not considered. The advantage of the new boundary conditions lies in the possibility to extend to more complicated situations including for instance specific ion adsorption. We prove that the new boundary conditions and classical ones give the same results. A comparison of the model predictions, involving no adjustable parameters, experimental dielectric spectroscopy data is performed and fairly good agreement is found. [Copyright &y& Elsevier]

Experimental data on the dielectric response of silica and hematite sols from the literature are interpreted using an analytical theory developed previously (Chassagne, C., Bedeaux, D., and Koper, G. J. M., J. Phys. Chem B105, 11,743 (2001), and Physica A, to be published). The theory is found to correctly predict both the relaxation frequency and the dielectric permittivity enhancement at low frequencies with only one free parameter. This parameter can be the zeta potential or the Stern layer conductance, in the case that the zeta potential is fixed to agree with the electrophoretic mobility measurements. [Copyright &y& Elsevier]

Despite recent advancement in the field of sediment transport, the integration of cohesive sediment properties in large-scale transport models remain a challenging task. In order to model adequately the change in particle size that occurs in different environmental conditions, flocculation models based on the so-called Population Balance Equations (PBE) are often used. These models have to be efficient enough to be implemented in numerical transport models, and as full PBE's are time-expensive to run and depend on a huge amount of a-priori unknown parameters, simplifications have to be made. These simplifications comes unavoidably at the cost of properly accounting for the complex particle-particle and particle-fluid interactions. In order to stay as close as possible to the physical processes, we propose a different approach based on a logistic growth model that mimics the Particle Size Distribution (PSD) measured over time for all size classes. The parameters of the model can easily be found from laboratory measurements. In contrast to most models, the particle classes we propose are not defined by particle size, but in terms of mineral sediment composition. One class is composed of (unflocculated) mineral sediment particles, another of flocculated sediment particles and a third one of organic particles. The mass balance between classes and the way to obtain their corresponding average settling velocity are given. Mass balance and settling velocities are the required input parameters for all sediment transport models. The simplicity of the derived expressions, and their link with measurable variables, makes them good candidates for future implementation in such models. • Population Balance Equations are not suitable for implementation in transport model. • Logistic growth models can be an alternative to Population Balance Equations. • Logistic growth models can be parametrized thanks to laboratory experiments. • Logistic growth models can be implemented in transport models. [ABSTRACT FROM AUTHOR]

In the mining industry, tailings are conventionally stored in artificial ponds that are susceptible to ruptures, as occurred in Southeast Brazil in November 2015. The Fundão failure dumped approximately 40 million m3 of very fine iron-rich tailing material into the Doce River watershed, where part reached the adjacent continental shelf. Part of the spilled material remained suspended in the water column after reaching the ocean. Zeta potential measurements (pH and salt dependence) were conducted to verify the flocculation tendency of suspensions. Surface sediment samples were collected in areas representative of key stages of tailings transport through the river and subsequent deposit on the continental shelf. A surface sediment sample from the continental shelf prior to the failure was used as a control. Previously published data suggested an influence from goethite on the flocculation of samples containing iron ore tailing sludge. Here we show that although a flocculation tendency was observed under influence of salts, the presence and quantity of iron oxyhydroxide were determinant in the flocculation pattern of contaminated sedimentary samples. Only sediment from the continental shelf before the mining dam breach exhibited classical zeta potential behavior dependence on pH and salinity expected in natural sediments containing clay minerals. Sediments contaminated with the iron ore tailing sludge displayed a clear influence of goethite on their zeta potential. Image 1 • Material from an iron ore mining dam breach has been exported by the Doce River onto the continental shelf. • Surface charge of suspended particles in aqueous solution was determined to understand flocculation tendencies. • Contaminated sediment showed zeta potential behavior similar to goethite. • When in marine waters pH, zeta potential had sudden jump in the negative values and left the flocculation tendency zone. • The amount of tailings in the sediment had a different influence on the behavior of the zeta potential. [ABSTRACT FROM AUTHOR]

This article discusses whether or to what extent flocculation plays a role in the saline deep-sea environment and whether sediment plumes generated by deep-sea mining activities are affected by the process of flocculation. The results of our laboratory study demonstrate that deep sea mineral clay with a median floc size of 20 μ m can flocculate quickly within 2.5 min of mixing to form flocs with a median floc size of about 50– 150 μ m and outliers as large as 500 μ m in size due to the presence of natural organic matter. At high shear (turbulent mixing), a threshold of about 125 s−1 was found above which, organic matter can successfully bind to clay. Above 125 s−1, the steady-state floc size is also found to increase linearly with shear. In low energetic conditions (when flocs experience mainly differential settling), the median floc sizes are found to be 2 or 3 times larger than at turbulent mixing. As expected, the rate of flocculation is greater at higher clay concentrations. At long mixing times, the median floc size is found to decrease due to the breaking/reconformation of flocs. Experiments performed to study the ageing of flocs at rest demonstrated that a dynamic process was ongoing between the organic matter and the clay. It is hypothesized that the organic matter present has amphiphilic properties. Over time, the organic matter would rearrange itself such as to maximize its contact area with the mineral clay, resulting in two effects, depending on the structure of the flocs. In the case of flocs formed at high shear, it led to a rupture of flocs. A slow agitation of settled flocs, having previously experienced low shear conditions, on the other hand, led to aggregation. Overall, the results found in the present article show that flocculation likely plays a significant role in deep-sea areas. [ABSTRACT FROM AUTHOR]

In this work a high-magnification digital video camera in combination with a settling column is used to study in a first part the influence of the amount of flocs transferred into the settling column on their settling velocity. In a second part, the setup was used to study the properties of flocs prepared at different clay concentrations but at same flocculant to clay ratio (2.5 mg g − 1). Illite clay was used and flocculated in a 1 L jar with an anionic polyacrylamide (flocculant). Results show that the average settling velocity of flocs is a function of the amount of transferred flocs. It was also found that floc size and settling velocity depend on clay concentration. This is attributed to the fast aggregation happening in the jar when flocculant and clay are mixed: at higher clay concentrations, larger flocs are created in the first minutes of the experiment, with low densities that prevent them from settling to the bottom of the jar. [ABSTRACT FROM AUTHOR]

Microspheres with high specific activities of radionuclides are very interesting for internal radiotherapy treatments. This work focuses on the formulation and characterization of inorganic microspheres with a high content of holmium and therefore a high specific radioactivity of holmium-166. Two novel formulations of inorganic microspheres were obtained by dispersing solid holmium acetylacetonate microspheres (Ho 2 (AcAc) 3 -ms) in NaH 2 PO 4 or NaOH solutions followed by 2 h incubation at room temperature. By exchange of acetylacetonate with phosphate or hydroxyl ions, holmium phosphate microspheres (HoPO 4 -ms) and holmium hydroxide microspheres (Ho(OH) 3 -ms) were formed respectively. The inorganic microspheres had a significantly smaller diameter (28.5 ± 4.4 μm (HoPO 4 -ms) and 25.1 ± 3.5 μm (Ho(OH) 3 -ms)) than those of Ho 2 (AcAc) 3 -ms (32.6 ± 5.2 μm). The weight percentage of holmium-165 in the microspheres increased significantly from 47% (Ho 2 (AcAc) 3 -ms) to 55% (HoPO 4 -ms) and 73% (Ho(OH) 3 -ms). After preparation of both HoPO 4 -ms and Ho(OH) 3 -ms, the stable holmium-165 isotope was partly converted by neutron activation into radioactive holmium-166 to yield radioactive microspheres. High specific activities were achieved ranging from 21.7 to 59.9 MBq/mg (166HoPO 4 -ms) and from 28.8 to 79.9 MBq/mg (166Ho(OH) 3 -ms) depending on the neutron activation time. The structure of both microspheres was preserved up to neutron activations of 6 h in a thermal neutron flux of 4.72 × 1016 n m−2 s−1. After activation, both microspheres revealed excellent stability in administration fluids (saline and phosphate buffer) having less than 0.05% of holmium released after 72 h incubation. Finally, the hemocompatibility of these inorganic microspheres was evaluated and it was shown that the microspheres did cause neither hemolysis nor depletion or inhibition of the coagulation factors of the intrinsic blood coagulation pathway meaning that the microspheres have a good hemocompatibility. Overall, this work shows that radioactive inorganic microspheres with high specific activities of holmium-166 can be prepared which potentially can be used for internal radionuclide therapy. Image 1 • Two inorganic microspheres (Ho-phosphate, Ho-hydroxide) are developed which are suitable for internal radionuclide therapy. • The holmium content obtained in the novel microspheres is ~55 wt% (Ho-phosphate) and ~73 wt% (Ho-hydroxide). • The higher specific activity allows to increase patient absorbed dose and makes the logistics more flexible. • The new microspheres are stable in administration fluids after neutron activation and show a good hemocompatibility. [ABSTRACT FROM AUTHOR]