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Jamming is an athermal transition between flowing and rigid states in amorphous systems such as granular matter, colloidal suspensions, complex fluids and cells. The jamming transition seems to display mixed aspects of a first-order transition, evidenced by a discontinuity in the coordination number, and a second-order transition, indicated by power-law scalings and diverging lengths. Here we demonstrate that jamming is a first-order transition with quenched disorder in cyclically sheared systems with quasistatic deformations, in two and three dimensions. Based on scaling analyses, we show that fluctuations of the jamming density in finite-sized systems have important consequences on the finite-size effects of various quantities, resulting in a square relationship between disconnected and connected susceptibilities, a key signature of the first-order transition with quenched disorder. This study puts the jamming transition into the category of a broad class of transitions in disordered systems where sample-to-sample fluctuations dominate over thermal fluctuations, suggesting that the nature and behavior of the jamming transition might be better understood within the developed theoretical framework of the athermally driven random-field Ising model. Jamming in amorphous systems is an athermal transition characterized by mixed first-order and second-order aspects. Authors demonstrate that jamming is a first-order transition with quenched disorder, revealing significant finite-size effects and a square relationship between disconnected and connected susceptibilities in cyclically sheared systems. [ABSTRACT FROM AUTHOR]

The phase behavior of complex fluid mixtures is of continuing interest, but obtaining the phase diagram from computer simulations can be challenging. In the Gibbs ensemble method, for example, each of the coexisting phases is simulated in a different cell, and ensuring the equality of chemical potentials of all components requires the transfer of molecules from one cell to the other. For complex fluids such as polymers, successful insertions are rare. An alternative method is to simulate both coexisting phases in a single simulation cell, with an interface between them. The challenge here is that the interface position moves during the simulation, making it difficult to determine the concentration profile and coexisting concentrations. In this work, we propose a new method for single cell simulations that uses a spatial concentration autocorrelation function to (spatially) align instantaneous concentration profiles from different snapshots. This allows one to obtain average concentration profiles and hence the coexisting concentrations. We test the method by calculating the phase diagrams of two systems: the Widom-Rowlinson model and the symmetric blends of freely jointed polymer molecules for which phase diagrams from conventional methods are available. Excellent agreement is found, except in the neighborhood of the critical point where the interface is broad and finite size effects are important. The method is easy to implement and readily applied to any mixture of complex fluids. [ABSTRACT FROM AUTHOR]

NMR relaxation experiments have provided a wealth of information about molecular motions in macromolecules and ordered fluids. Even though a rigorous theory of spin relaxation is available, the complexity of the investigated systems often makes the interpretation of limited datasets challenging and ambiguous. To allow physically meaningful information to be extracted from the data without commitment to detailed dynamical models, several versions of a model-free (MF) approach to data analysis have been developed. During the past 2 decades, the MF approach has been used in the vast majority of all NMR relaxation studies of internal motions in proteins and other macromolecules, and it has also played an important role in studies of colloidal systems. Although the MF approach has been almost universally adopted, substantial disagreement remains about its physical foundations and range of validity. It is our aim here to clarify these issues. To this end, we first present rigorous derivations of the three well-known MF formulas for the time correlation function relevant for isotropic solutions. These derivations are more general than the original ones, thereby substantially extending the range of validity of the MF approach. We point out several common misconceptions and explain the physical significance of the approximations involved. In particular, we discuss symmetry requirements and the dynamical decoupling approximation that plays a key role in the MF approach. We also derive a new MF formula, applicable to anisotropic fluids and solids, including microcrystalline protein samples. The so-called slowly relaxing local structure (SRLS) model has been advanced as an alternative to the MF approach that does not require dynamical decoupling of internal and global motions. To resolve the existing controversy about the relative merits of the SRLS model and the MF approach, we formulate and solve a planar version of the SRLS model. The analytical solution of this model reveals the unphysical consequences of the symmetrical two-body Smoluchowski equation as applied to protein dynamics, thus refuting the widely held belief that the SRLS model is more accurate than the MF approach. The different results obtained by analyzing data with these two approaches therefore do not indicate the importance of dynamical coupling between internal and global motions. Finally, we explore the two principal mechanisms of dynamical coupling in proteins: torque-mediated and friction-mediated coupling. We argue by way of specific analytically solvable models that torque-mediated coupling (which the SRLS model attempts to capture) is unimportant because the relatively slow internal motions that might couple to the global motion tend to be intermittent (jumplike) in character, whereas friction-mediated coupling (which neither the SRLS model nor the MF approach incorporates) may be important for proteins with unstructured parts or flexibly connected domains. [ABSTRACT FROM AUTHOR]

The critical behavior of osmotic susceptibility is investigated in the re-entrant complex mixture 1-propanol (P)+water (W)+potassium chloride (KCl) through light-scattering measurements. The measurements are performed on approaching a special critical point [i.e., the double critical point (DCP)] in this mixture, along the line of upper critical solution temperatures (TU’s), by varying t from the high temperature one-phase region. The light-scattering data analysis emphasizes the need for corrections to the asymptotic Ising behavior and yields very large magnitudes for the correction-to-scaling amplitudes A1 and A2, with the first-correction amplitude A1 being negative, signifying a nonmonotonic crossover behavior of the susceptibility exponent in this mixture. For the TU closest to the DCP, the effective susceptibility exponent γeff displays a nonmonotonic crossover from its nearly doubled three dimensional (3D)-Ising value toward its nearly double mean-field value with an increase in t. While for that far away from the DCP, it displays a nonmonotonic crossover from its single-limit Ising value toward a value slightly lower than its mean-field value of 1 with an increase in t. This feature of the effective susceptibility exponent is interpreted in terms of the possibility of a nonmonotonic crossover to the mean-field value from lower values in the nonasymptotic high t region. The renormalized Ising regime extends over a larger t range for the sample (or TU) closest to the DCP when compared to that far away from it. The in-between TU’s display a trend toward shrinkage in the renormalized Ising regime as TU shifts away from the DCP. Nevertheless, the crossover to the mean-field behavior is completed only beyond t>10-2 for the TU’s studied. The observed crossover behavior is attributed to the presence of strong ion-induced clustering in this mixture, as revealed by various structure probing techniques, while the observed unique trend in the crossover behavior is discussed in terms of the varying influence of the DCP on the critical behavior along the TU line. The crossover behavior for the TU’s is pronounced and more sharp compared to the TL’s (lower critical solution temperatures) [U. K. Pradeep, J. Chem. Phys. 129, 134506 (2008)] in this mixture, although there exists no difference in the growth of the mesoscale clusters in the lower and upper one-phase regions in this mixture. Our observations suggest the need to look at the crossover behavior probably from two perspectives, namely, the dielectric effect and the clustering effect. The effective susceptibility exponent as a function of the field variable tUL, instead of the conventional variable t, displays a sharp nonmonotonic crossover from its asymptotic 3D-Ising value (∼1.24) toward a value slightly lower than its nonasymptotic mean-field value of 1, as that observed in the t analysis for the TU far away from the influence of the DCP. [ABSTRACT FROM AUTHOR]

Cluster formation and disintegration greatly complicate the description of relaxation processes in complex fluids. We systematically contrast the viscoelastic and dielectric properties for models of equilibrium polymers whose thermodynamic properties have previously been established. In particular, the monomer-mediated model allows chain growth to proceed only by monomer addition, while the scission-recombination model enables all particles to associate democratically, so that chain scission and fusion occur at the interior segments as well as at chain ends. The minimal models neglect hydrodynamic and entanglement interactions and are designed to explore systematically the competition between chemical reaction and internal chain relaxation and how this coupling modifies the dynamics from that of a polydisperse solution of Rouse chains with fixed lengths (i.e., “frozen” chains). As expected, the stress relaxation is nearly single exponential when the assembly-disassembly reaction is fast on the time scale of structural chain rearrangements, while multiexponential or nearly stretched exponential relaxation is obtained when this reaction rate is slow compared to the broad relaxation spectrum of almost unperturbed, nearly “dead” chains of intrinsically polydisperse equilibrium polymer solutions. More generally, a complicated intermediate behavior emerges from the interplay between the chemical kinetic events and internal chain motions. [ABSTRACT FROM AUTHOR]

Gibbs-Duhem Monte Carlo simulations are reported for the vapor-liquid phase coexistence of binary argon+krypton mixtures at different temperatures. The calculations employ accurate two-body potentials in addition to contributions from three-body dispersion interactions resulting from third-order triple-dipole interactions. A comparison is made with experiment that illustrates the role of three-body interactions on the phase envelope. In all cases the simulations represent genuine predictions with input parameters obtained independently from sources other than phase equilibria data. Two-body interactions alone are insufficient to adequately describe vapor-liquid coexistence. In contrast, the addition of three-body interactions results in very good agreement with experiment. In addition to the exact calculation of three-body interactions, calculations are reported with an approximate formula for three-body interactions, which also yields good results. [ABSTRACT FROM AUTHOR]

Understanding the rheological behavior of complex fluids, and in particular its relation to the dynamics of the elementary microscopic constituents, is one of the open challenges in soft matter science. In this contribution, we give a brief introduction to linear shear rheology and passive microrheology of soft amorphous materials, and we then focus on the transition to non-linearity during oscillatory rheology tests performed on soft glassy materials. These materials exhibit solid-like properties at rest, but they display characteristics of fluids when a sufficiently large shear is applied. Significant progress in understanding such 'fluidization' has been recently achieved by combining rheometry with techniques capable to capture the microscopic dynamics induced by shear, and in particular by oscillatory shear. We here summarize some of these achievements, as an introduction to the field for a non-expert reader. • Materials under mechanical stress may fail dramatically and unpredictably. • Connecting macroscopic failure to the microscopic rearrangements is essential. • Yielding of soft glassy materials can be investigated with moderate forces and light. • Rheo-optical investigation allows a connection between micro- and macro. • Oscillatory tests are particularly convenient and effective. [ABSTRACT FROM AUTHOR]

Bubble rafts consisting of a single layer of bubbles floating on the surface of water have proven to be an important model system for studying materials ranging from crystalline systems to amorphous solids to complex fluids. An interesting question in foams and complex fluids is how the detailed nature of the bubble–bubble interactions determines the resulting stable states of the system, especially in the context of different approaches to generating the foam or complex fluid. In this paper, we report on the generation of bubble rafts using an imposed flow. The flow breaks the symmetry of the system and allows for the generation of stable bubble ribbons of many different widths. We report on the transition between ribbons of different widths and the ultimate separation of the system into multiple small ribbons. An interesting feature of the system is the stability of very narrow ribbons against self-folding. In principle, folding of the ribbons would produce states with lower global energy. Therefore, understanding the energy barriers and dynamics involved in the prevention of this transition will play a role in deepening our understanding of these systems. [ABSTRACT FROM AUTHOR]

Gelled complex fluids are soft materials in which the microstructure of the complex fluid is combined with the mechanical stability of a gel. To obtain a gelled complex fluid one either adds a gelator to a complex fluid or replaces the solvent in a gel by a complex fluid. The most prominent example of a 'natural' gelled complex fluid is the cell. There are various strategies by which one can form a gelled complex fluid; one such strategy is orthogonal self-assembly, that is, the independent but simultaneous formation of two coexisting self-assembled structures within one system. The aim of this Review is to describe the structure and potential applications of various man-made gelled complex fluids and to clarify whether or not the respective system is formed by orthogonal self-assembly. [ABSTRACT FROM AUTHOR]

The effects of varying the alkaline earth oxide content of three series of soda–lime–silica glasses with the general formulae 13.5Na 2 O· x MgO·10CaO·1.5Al 2 O 3 ·(75 − x )SiO 2 (mol.%) where x = 0, 1, 2, 3, 4, 5, 6, and 7; 13.5Na 2 O·3MgO·(7 + y )CaO·1.5Al 2 O 3 ·(75 − y )SiO 2 (mol.%) where y = 0, 1, 2, 3, 4, 5, 6, and 7 and 13.5Na 2 O· z MgO·(13 − z )CaO·1.5Al 2 O 3 ·72SiO 2 (mol.%) where z = 1, 3, 5, 7, 9, and 11 have been examined. Raman spectroscopy and nuclear magnetic resonance (NMR) spectroscopy have been used to assess network connectivity. In the first two glass series network connectivity decreases with increasing alkaline earth addition whereas in the third series connectivity tends to be greater for the more magnesia rich glasses suggesting that magnesia does have a different effect to lime on network connectivity, but only when magnesia is the dominant alkaline earth species. Fracture toughness has been measured using bend testing, which avoids many of the questions raised by the widely used indentation technique. Moduli have been assessed using acoustic means. It was found that the mechanical properties tend to decrease with increasing network connectivity for all three glass series. For the MgO–SiO 2 series and CaO–SiO 2 glasses increasing the alkaline earth content at the expense of the silica content resulted in increased network depolymerization, whereas for the MgO–CaO series when MgO became the dominant alkaline earth species, network depolymerization was reduced. Thus whilst MgO and CaO both act as network modifiers when more CaO than MgO is present in soda–lime–silica glasses, a difference in behaviour is seen with magnesia rich soda–magnesia–silica glasses. In contradiction to previous data no significant advantage of replacing CaO by MgO is observed. In addition it appears that the glasses with the lowest fracture toughness values may be more resilient to contact damage than those with the higher fracture toughness values. [ABSTRACT FROM AUTHOR]

Dispensing characteristics of rheologically complex fluids are investigated experimentally at the dripping regime. Two mixtures of ethylene glycol and glycerin (50:50 and 31:69) were used as base Newtonian fluids. As the polymer solution, 1000 ppm of polyacrylamide of 5–6M g/mol was added to the 50:50 base Newtonian fluid. 2.5, 5 or 7.5 vol% of polystyrene particles of 2 μm in diameter were added to the liquids to prepare particle suspensions. The liquids were dispensed to the air by using a nozzle with the inner and outer diameters of 0.61 and 0.91 mm, respectively. It was found that the drop size is primarily determined by the balance of drop weight and surface tension force holding the drop, and hence drop size does not depend on volume flow rate. The drop diameter is approximately 10% smaller for elastic liquids due to the severe extension of the filament before the detachment from the nozzle. The result also shows that the dripping characteristics of the fluids without the polymer are mainly determined by the balance of the gravity force, surface tension force holding the liquid volume and pressure force. The addition of less than approximately 10% of 2 μm spherical particles hardly changes the dispensing characteristics of Newtonian fluids except at the final stage of detachment. For polymeric liquids, the transient extensional property drastically changes the dripping dynamics. The force balance shows that the strain hardening of the polyacrylamide solution under the extensional flow causes severe retardation of the filament breakup. The filament breakup of the polymeric suspension is further decelerated by the increase in zero shear viscosity as a result of the particle addition. [ABSTRACT FROM AUTHOR]

Knowledge of the supramolecular structure of the organic phase containing amphiphilic ligand molecules is mandatory for full comprehension of ionic separation during solvent extraction. Existing structural models are based on simple geometric aggregates, but no consensus exists on the interaction potentials. Herein, we show that molecular dynamics crossed with scattering techniques offers key insight into the complex fluid involving weak interactions without any long-range ordering. Two systems containing mono- or diamide extractants in heptane and contacted with an aqueous phase were selected as examples to demonstrate the advantages of coupling the two approaches for furthering fundamental studies on solvent extraction. [ABSTRACT FROM AUTHOR]

Abstract: A temperature rise on the order of tenths of a degree is observed as one fluid spreads over a hygroscopic fluid. While this behavior is only exhibited with hygroscopic fluids, it is independent of the properties of the spreading fluid. The spreading induces a ‘rolling’ motion in the subphase which brings ‘fresh’ fluid to the surface, exposing it to the water vapor in the air. As water is absorbed into the hygroscopic liquid, heat is released. The same behavior is observed whether the spreading fluid has a spreading monolayer that drives a convection front or is a spreading lens with a moving three-phase contact line. [Copyright &y& Elsevier]

Transition rates in continuously driven steady states (relevant to sheared complex fluids) were derived in Evans (2004, 2005) by demanding that no information other than the microscopic laws of motion and the macroscopic observables of the system be used to describe it. This implies that the (nonequilibrium) reservoir, to which the system is weakly coupled, is fully characterized by its mean energy and mean flux. While we expect the resulting prescription for the rates in continuous- and discretized-time models to be equivalent, it is not trivial to see this from the expression for the rates derived in Evans (2005). We demonstrate this equivalence for a model of activated processes solved previously for continuous time (Evans 2005), thus demonstrating consistency of the theory. [ABSTRACT FROM PUBLISHER]

The article examines the importance of studying the behavior of complex fluids and its confining boundaries. It mentions the consequences towards the motion of the fluids due to its confining length, its classifications by dimensionality and colloidal mixtures. An illustration of the double emulsions from jetting high flow rates to dripping low flow rates is also presented.

This paper reports the phase transition and optical properties of the (Sb2Se3)100-xSnx (x=0, 5) films. The resistance-temperature measurements show an increase in the phase transformation temperature and no new phase has been crystallized with the addition of Sn in the parent alloy. The optical gap decreases while an increase in tailing parameter have been found with the addition of Sn. The crystallization of the films at the transformation temperature results in the decrease of the optical gap with anomalous change in the tailing parameter. A large change in the optical contrast with the maxima at the 430nm is important to tailor the new materials for the information storage applications. [ABSTRACT FROM AUTHOR]

The article focuses on an enhanced method for measuring distillation curves. The improved method is called the composition explicit or advanced distillation curve (ADC) which features a composition-explicit data channel, temperature measurements, and corrosivity assessment. It mentions that the improved method found out that physicochemical properties of complex fluids such as fuels.

We study the convergence rate of the solutions of the incompressible Euler- α, an inviscid second-grade complex fluid, equations to the corresponding solutions of the Euler equations, as the regularization parameter α approaches zero. First we show the convergence in H s , s> n/2+1, in the whole space, and that the smooth Euler- α solutions exist at least as long as the corresponding solution of the Euler equations. Next we estimate the convergence rate for two-dimensional vortex patch with smooth boundaries. [ABSTRACT FROM AUTHOR]

Measurements of dc electrical conductivity and optical properties have been made on InSbTe3 thin films prepared by thermal evaporation having different thickness (25-150) nm range. The structure of InSbTe3 in its powder and thin film forms were investigated by X-ray diffraction (XRD). The electrical conductivity was measured in the temperature (303-392) K range. The obtained values of dc electrical conduction activation energy ΔEσ were found to be nearly independent on the film thickness and have the mean value of 0.173 eV in the range considered. The refractive index n and the absorption index k were determined in the spectral range 400-2500 nm. It is observed that n decreases with increasing film thickness at any wave length, while k is practically independent on film thickness in the range 25-150 nm. For films with thicknesses in the range 170-304 nm, the spectral distribution of transmittance T and reflectance R showed that T+R<1 in the whole spectrum which due to light scattering by surface roughness whose existence is confirmed by electron microscopy. Analysis of k indicated that the absorption mechanism refers to the existence of indirect transitions with an optical energy gap of 0.52 eV. [ABSTRACT FROM AUTHOR]

It was of interest to investigate the solid-state acidity using indicator probe molecules and sucrose degradation. Amorphous samples containing lactose, sucrose, buffers (citrate, malate, tartarate, or phosphate) with different pH values, and sodium chloride (to adjust the ionic strength) were prepared by freeze-drying. The lyophiles were characterized using powder X-ray diffraction, differential scanning calorimetry, and Karl Fischer titrimetry. The solid-state acidity of all lyophiles was measured using diffuse reflectance spectroscopy and suitable indicators (thymol blue or bromophenol blue). Selected lyophiles were subjected to a temperature of 60°C and were analyzed for sucrose degradation using the Trinder kit. The results obtained from this study have shown that good correlation can be obtained between the solid-state acidity and the molar ratio of the salt and the acid in solution. The degradation of sucrose in the lyophiles is extremely sensitive to the solid-state acidity and might be able to provide a better estimate for the acidity than the indicator probe molecules. The Hammett acidity-rate profile for sucrose degradation in the lyophiles (using four different buffers) was also obtained. The profile showed similarity to the pH-rate profile in solution, and no buffer catalysis for sucrose degradation was detected in this study. [ABSTRACT FROM AUTHOR]

As an experimental project proposed to students in fourth year of university, a viscometer was developed, consisting of a small magnet levitating in a viscous fluid. The viscous force acting on the magnet is directly measured: viscosities in the range 10-106 mPa s are obtained. This experiment is used as an introduction to complex fluids and soft matter physics. [ABSTRACT FROM AUTHOR]

We reexamine the interpretation of the normal force measured with a cone-and-plate rheometer for nematic liquid crystals. We point out the fact that the quite widespread belief that the normal force is directly related to the well-known rheological function N1 (i.e., the first normal stress difference) fails for these complex fluids. After a brief presentation of the theoretical bases leading to the general expression of the normal force, this new approach is applied to nematic liquid crystals within the framework of Leslie-Ericksen theory. In order to avoid heavy numerical computations the full Leslie-Ericksen equations describing the three-dimensional flow within the cone-and-plate cell are reduced, thanks to reasonable approximations, to an effective one-dimensional problem (i.e., a system of partial differential equations with spatial derivatives with respect to one single coordinate). Results for low molecular weight liquid crystals are presented and discussed. The main feature evidenced in this work is the notable difference between the normal force calculated in this way and the N1 function, in particular the normal force function becomes negative for high shear rate while N1 stays positive. [ABSTRACT FROM AUTHOR]

We investigate analytically the interaction between circular inclusions in smectic-C films with planar anchoring. We present a rigorous solution for an isolated circular colloid with planar anchoring and use it to calculate the interacion between two circular colloids, approximately. At large separations the interaction is quadrupolar and we show that at short range two different regimes may be observed. For weak anchoring, the interaction is always attractive in some directions, which may lead to particle contact or coalescence. However, for strong anchoring, the interaction exhibits a well defined minimum, for colloids at a particular separation and given relative orientation. The equilibrium configuration was found to depend on the anchoring strength. [ABSTRACT FROM AUTHOR]

Discrete simulation methods are efficient tools to investigate the behaviors of complex fluids such as dry granular materials or dilute suspensions of hard particles. By contrast, materials made of soft and/or concentrated units (emulsions, foams, vesicles, dense suspensions) can exhibit both significant elastic particle deflections (Hertz-like response) and strong viscous forces (squeezed liquid). We point out that the gap between two particles is then not determined solely by the positions of their centers, but rather exhibits its own dynamics. We provide the first ingredients of a new discrete numerical method, named Soft Dynamics, to simulate the combined dynamics of particles and contacts. As an illustration, we present the results for the approach of two particles. We recover the scaling behaviors expected in three limits: the Stokes limit for very large gaps, the Poiseuille-lubricated limit for small gaps and even smaller surface deflections, and the Hertz limit for significant surface deflections. We find that for each gap value, an optimal force achieves the fastest approach velocity. The principle of larger-scale simulations with this new method is provided. They will consitute a promising tool for investigating the collective behaviors of many complex materials. [ABSTRACT FROM AUTHOR]

Using computational modeling, we simulate the 3D movement of actuated cilia in a fluid-filled microchannel. The cilia are modeled as deformable, elastic filaments, and the simulations capture the complex fluid−structure interactions among these filaments, the channel walls, and the surrounding solution. The cilia are tilted with respect to the surface and are actuated by a sinusoidal force that is applied at the free ends. We find that these cilia give rise to a unidirectional flow in the system and by simply altering the frequency of the applied force we can controllably switch the direction of the net flow. The findings indicate that beating, synthetic cilia could be harnessed to regulate the fluid streams in microfluidic devices. [ABSTRACT FROM AUTHOR]

Abstract: Adding product into the mixer exerts a strong and rapid impact during concrete mixing. Experimental data obtained from a planetary mixer in a full-scale concrete plant under laboratory conditions show that the state of mixture progress with mixing time is well described by the mixing power evolution. More specifically, a reliable method for detecting the time corresponding to the transformation of a mixture from a cohesive granular material into a granular paste (i.e. the so-called “transition time”), through use of a mixing power measurement, will be presented herein. Moreover, once this transition has been achieved, mixing power consumption will be related to mixture rheology and then to mixer geometry by means of a simplified hypothesis. This equation can also be obtained via a dimensionless analysis. Lastly, it will be shown that mixture behavior beyond the transition point is well fitted by a hyperbolic equation. The corresponding mixing power evolution can then be predicted by the level of power at this transition time. These results are suitable for application to online process monitoring. [Copyright &y& Elsevier]

This article discusses recent attempts to provide a deeper understanding of the thermoreversible “gel” state of colloidal matter and to unravel the analogies between gels at the colloidal level and gels at the molecular level, commonly known as network-forming strong liquids. The connection between gel-forming patchy colloids and strong liquids is provided by the limited valence of the inter-particle interactions, i.e. by the presence of a limit in the number of bonded nearest neighbors. [ABSTRACT FROM AUTHOR]

Rifampicin, one of the main first line anti-TB drugs, shows variable bioavailability in different marketed preparations and reasons cited include physiological, degradation, manufacturing/ processing, solid state, and bioavailability assessment procedure. Although the amorphous form of a drug is expected to exhibit higher solubility, the amorphous rifampicin has been reported to have a solubility disadvantage as compared to crystalline form II, which is used in marketed preparations. Amorphous form was generated and characterized by solid-state characterization techniques. Physical powder mixtures of form II with varying amounts of amorphous form were prepared, which were then subjected to solid-state characterization techniques and further evaluated for their dissolution behavior. Differential scanning calorimetry (DSC) scans show that area enclosed by integral of melting endotherm can be used for quantification of crystalline component, which can then be used to estimate amorphous content. No definite trend was evident in powder dissolution of mixtures that could implicate solubility difference of amorphous form. Intrinsic dissolution rate (IDR) results indicate that amorphous content has no effect on dissolution profiles of crystalline rifampicin. [ABSTRACT FROM AUTHOR]

Abstract: The stability of the sodium and calcium forms of montmorillonite was studied at different NaCl and CaCl2 concentrations. The aggregation kinetics was determined from the decrease in particle concentration with time at different electrolyte concentrations. The DLVO theory defines the critical coagulation concentration (CCC) value as the electrolyte concentration that balances the attractive and repulsive potential energies between the particles, making aggregation diffusion-controlled. Therefore CCC values were obtained by extrapolation of the aggregation rate constants measured as a function of ionic strength to conditions where the rate constant value is determined by diffusion only. When the electrolyte was CaCl2, the CCC value was found to be approximately two orders of magnitude lower than the CCC values obtained using NaCl as electrolyte. [Copyright &y& Elsevier]

This paper explores the ability of molecular evolution to take control of collective physical phases, making the first decisive step from independent replicators towards cell-like collective structures. We develop a physical model of replicating combinatorial molecules in a ternary fluid of hydrocarbons, amphiphiles and water. Such systems are being studied experimentally in various laboratories to approach the synthesis of artificial cells, and are also relevant to the origin of cellular life. The model represents amphiphiles by spins on a lattice (with Ising coupling in the simplest case), coupled to replicating molecules that may diffuse on the lattice and react with each other. The presence of the replicating molecules locally modulates the phases of the complex fluid, and the physical replication process and/or mobility of the replicating molecules is influenced by the local amphiphilic configuration through an energetic coupling. Consequently, the replicators can potentially modify their environment to enhance their own replication. Through this coupling, the system can associate hereditary properties, and the potential for autonomous evolution, to self-assembling mesoscale structures in the complex fluid. This opens a route to analyse the evolution of artificial cells. The models are studied using Monte Carlo simulation, and demonstrate the evolution of phase control. We achieve a unified combinatorial framework for the description of isotropic families of spin-lattice models of complex phases, opening up the physical study of their evolution. [ABSTRACT FROM AUTHOR]

Abstract: Most of the metallic glasses which have been identified to date require rapid solidification processing (RSP) in order to obtain the high cooling rates required to avoid the thermally activated decomposition reactions that result in the formation of crystalline phases. While the free-jet melt spinning technique is commonly used for the investigation of amorphous alloy formation, many of the key process parameters remain poorly understood. In the work presented here, we utilize high speed digital imaging to investigate various melt-pool characteristics and their influence on the melt-spun ribbon. With detailed measurements of melt-pool geometry and surface temperature, we show that the length of this molten zone establishes a critical length scale which characterizes the ribbon thickness and cooling rate. Within certain limits, the ribbon thickness is shown to correlate with a simple 2D laminar flow boundary layer formed at the base of the melt-pool. Estimates of initial quench rate, based on surface temperature measurements, clearly reveal the importance of two distinct cooling periods. The first is the wheel-contact period, where the ribbon remains in intimate contact with the quench wheel and cooling is primarily governed by the heat conduction across the ribbon-wheel boundary. The second is the free-flight period, where the ribbon separates from the wheel, and cooling is governed by radiation and convection into the chamber. [Copyright &y& Elsevier]

Abstract: The dynamic structure factors, S(Q, E), for Ni42Nb58 metallic glass have been measured using neutron inelastic scattering on the IN4 spectrometer (ILL, Grenoble, France), over a range of momentum transfer, 0.7< ℏQ/Å−1 <8, and energy transfer, 2< E/meV<50. Three samples with the same chemical composition and different Ni isotope content were investigated. The constant-E and constant-Q cuts through the S(Q, E) functions have been obtained. They reveal the E-and Q-dependencies due to the existence of the collective vibrational excitations in Ni42Nb58 glass. At the same time the difference of Ni and Nb atoms dynamics was observed by isotope contrast in the scattered spectra. [Copyright &y& Elsevier]

Abstract: Hydrogenated amorphous carbon (a-C:H) films have been grown from argon/methane gas mixtures by electron cyclotron resonance chemical vapour deposition (ECR-CVD) on silicon substrates. The effects of the application of a DC substrate bias on the structural, morphological and mechanical properties of the films have been explored by multiple analysis techniques such as infrared and micro-Raman spectroscopy, atomic force microscopy, nanoindentation and pin-on-disk wear testing. In general, within the range of applied substrate bias (i.e. from −300 up to +100V) we have observed a strong correlation between all measured properties of the a-C:H films and the ion energy. This work shows that the properties can differ greatly and indicates a threshold energy in the order of 90eV. For the production of hard, low-friction coatings energies above this value are required. [Copyright &y& Elsevier]

Flagella beating in complex fluids are significantly influenced by viscoelastic stresses. Relevant examples include the ciliary transport of respiratory airway mucus and the motion of spermatozoa in the mucus-filled female reproductive tract. We consider the simplest model of such propulsion and transport in a complex fluid, a waving sheet of small amplitude free to move in a polymeric fluid with a single relaxation time. We show that, compared to self-propulsion in a Newtonian fluid occurring at a velocity UN, the sheet swims (or transports fluid) with velocity U/UN=(1+De2ηs/η)/(1+De2), where ηs is the viscosity of the Newtonian solvent, η is the zero-shear-rate viscosity of the polymeric fluid, and De is the Deborah number for the wave motion, product of the wave frequency by the fluid relaxation time. Similar expressions are derived for the rate of work of the sheet and the mechanical efficiency of the motion. These results are shown to be independent of the particular nonlinear constitutive equations chosen for the fluid, and are valid for both waves of tangential and normal motion. The generalization to more than one relaxation time is also provided. In stark contrast with the Newtonian case, these calculations suggest that transport and locomotion in a non-Newtonian fluid can be conveniently tuned without having to modify the waving gait of the sheet but instead by passively modulating the material properties of the liquid. [ABSTRACT FROM AUTHOR]

By applying a methodology useful for analysis of complex fuids based on a synergistic combination of experiments, computer simulations, and theoretical investigation, a model was built to investigate the fluid dynamics of granular flows in an intermediate regime, where both collisional and frictional interactions may affect the flow behavior. In Part 1, experiments were described using a modified Newton's Cradle device to obtain values for the viscous damping coefficient, which were scarce in the literature. This paper discusses detailed simulations of frictional interactions between the grains during a binary collision by employing a numerical model based on finite element methods. Numerical results are presented of slipping, and sticking motions of a first grain over the second one. The key was to utilize the results of the aforementioned comprehensive model in order to provide a simplified model for accurate and efficient granular-flow simulations with which the qualitative trends observed in the experiments can be captured. To validate the model, large scale simulations were performed for the specific case of granular flow in a rapidly spinning bucket. The model was able to reproduce experimentally observed flow phenomena, such as the formation of a depression in the center of the bucket spinning at high frequency of 100 rad/s. This agreement suggests that the model may be a useful tool for the prediction of dense granular flows in industrial applications, but highlights the need for further experimental investigation of granular flows in order to refine the model. [ABSTRACT FROM AUTHOR]

Abstract: An efficient reconstruction procedure for evaluating the constitutive properties of a complex fluid from general or specialized thermodynamic databases is presented. Properties and their pertinent derivatives are evaluated by means of an adaptive Cartesian mesh in the thermodynamic plane that provides user-specified accuracy over any selected domain. The Cartesian grid produces a binary tree data structure whose search efficiency is competitive with that for an equally spaced table or with simple equations of state such as a perfect gas. Reconstruction is accomplished on a triangular subdivision of the 2D Cartesian mesh that ensures function continuity across cell boundaries in equally and unequally spaced portions of the table to C 0, C 1 or C 2 levels. The C 0 and C 1 reconstructions fit the equation of state and enthalpy relations separately, while the C 2 reconstruction fits the Helmholtz or Gibbs function enabling EOS/enthalpy consistency also. All three reconstruction levels appear effective for CFD solutions obtained to date. The efficiency of the method is demonstrated through storage and data retrieval examples for air, water and carbon dioxide. The time required for property evaluations is approximately two orders of magnitude faster with the reconstruction procedure than with the complete thermodynamic equations resulting in estimated 3D CFD savings of from 30 to 60. Storage requirements are modest for today’s computers, with the C 1 method requiring slightly less storage than those for the C 0 and C 2 reconstructions when the same accuracy is specified. Sample fluid dynamic calculations based upon the procedure show that the C 1 and C 2 methods are approximately a factor of two slower than the C 0 method but that the reconstruction procedure enables arbitrary fluid CFD calculations that are as efficient as those for a perfect gas or an incompressible fluid for all three accuracy levels. [Copyright &y& Elsevier]

Abstract: Changes in size distribution and elemental composition of 0.5–50nm fresh water colloids during estuarine mixing have been studied by in-laboratory mixing of natural creek water and synthetic seawater, followed by size fractionation with Asymmetrical Flow Field-Flow Fractionation, and online elemental quantification by High-Resolution ICPMS. At least two types of colloids were present in the studied size region; 0.5–3nm fluorescent dissolved organic matter (FDOM), and >3nm colloids that were rich in Fe and colored dissolved organic matter (CDOM). Most trace elements were associated in different proportions to these two populations of colloids. Following mixing with synthetic seawater, the >3nm Fe-rich colloids and CDOM were extensively removed from the studied size region by salt induced aggregation. The degree of removal with increasing salinity was greatest below 2.5‰ salinity, continued to a lesser degree between 2.5‰ and 15‰ salinity, above which only very small additional removal could be distinguished. At 25‰ salinity, the Fe concentration in the 0.5–50 size region had been reduced down to 15% of its original value in freshwater, while the amount of CDOM had been reduced to 55%. On the contrary, the concentration of the 0.5–3nm FDOM was unchanged by the increased concentration of sea salt. Therefore, colloidally associated Al, P, Co, Cu, Zn, Ce, Lu and Pb were removed from the 0.5–50nm size region according to their relative distributions between the FDOM and the Fe-rich colloids. Consequently, at 25‰ salinity, the 0.5–50nm concentrations of Al, Mn, P and Pb, (mainly associated with the Fe-rich colloids) had been reduced down to 13–26 % of their values in freshwater, while the concentrations of Co and Cu (with higher preferences for FDOM) were less reduced, down to 46% and 57%, respectively. Changes in the elemental composition of the remaining colloidal matter were observed, the most pronounced were increased contents of P, Al and Pb in Fe-rich colloidal matter of medium size (∼3–15nm) and increased Pb content in Fe-rich colloidal matter of larger size (∼5–50nm). [Copyright &y& Elsevier]

The melt's solidification behaviour of elemental sulfur was investigated by a series of experiments including natural cooling at ambient pressure, thermal quenching under high pressure of 1?GPa, slow compressing to 2?GPa for 10?min and rapid compressing to 2?GPa within 20?ms. Based on the XRD and DSC results of the recovered samples, it is clearly shown that rapid compression is an effective process in the solidification of an amorphous phase from the melt in sulfur. We have successfully recovered large bulk amorphous sulfur with a diameter of 20?mm and a thickness of 3?mm by the rapid compression method. [ABSTRACT FROM AUTHOR]