Soft Condensed Matter

A simple device based on the principle of frustrated total internal reflection was used to image the regions of contact between rubber objects and a large area perspex waveguide. Measurements of the intensity of light scattered at the interface were found to depend upon the magnitude of the applied force, the mechanical properties of the contacting material and the roughness of the contacting objects. The intensity/force response was found to have the same functional dependence irrespective of the position on the waveguide surface, but to scale by an amount that was proportional to the local intensity of light incident on the perspex/object interface. Once this spatial variation in intensity had been calibrated, the waveguide could be used to perform optical measurements of the forces/pressures exerted on the surface of the waveguide and to generate spatial maps of the pressure at frame rates up to 200 Hz. The resulting optical force platform was used to measure the time dependent evolution of the pressure distribution beneath a foot and a sports shoe during a foot strike event. A simple theory was developed to describe the light scattering phenomenon and to explain the relationship between the scattered light intensity and the applied force.

Sucralose is a commonly employed artificial sweetener that appears to destabilize protein native structures. This is in direct contrast to the bio-preservative nature of its natural counterpart, sucrose, which enhances the stability of biomolecules against environmental stress. We have further explored the molecular interactions of sucralose as compared to sucrose to illuminate the origin of the differences in their bio-preservative efficacy. We show that the mode of interactions of sucralose and sucrose in bulk solution differ subtly through the use of hydration dynamics measurement and computational simulation. Sucralose does not appear to disturb the native state of proteins for moderate concentrations (<0.2 M) at room temperature. However, as the concentration increases, or in the thermally stressed state, sucralose appears to differ in its interactions with protein leading to the reduction of native state stability. This difference in interaction appears weak. We explored th...

We study geometrical confinement effects in Bi2Sr2CaCu2O 8+δ mesoscopic vortex-matter with edge-to-surface ratio of 7 − 12 %. Samples have in-plane square and circular edges, 30 µm widths, and ∼ 2 µm thickness. Direct vortex imaging reveals the compact planes of the structure align with the sample edge by introducing topological defects. The defects density is larger for circular than for square edges. Molecular dynamics simulations suggest this density is not an out-of-equilibrium property but rather determined by the geometrical confinement.

We investigate the ordered morphologies occurring in thin-films diblock copolymer. For temperatures above the order-disorder transition and for an arbitrary two-dimensional surface pattern, we use a Ginzburg-Landau expansion of the free energy to obtain a linear response description of the copolymer melt. The ordering in the directions perpendicular and parallel to the surface are coupled. Three dimensional structures existing when a melt is confined between two surfaces are examined. Below the order-disorder transition we find tilted lamellar phases in the presence of striped surface fields.

There has been a recent revolution in the ability to manipulate micrometer-sized objects on surfaces patterned by traps or obstacles of controllable configurations and shapes. One application of this technology is to separate particles driven across such a surface by an external force according to some particle characteristic such as size or index of refraction. The surface features cause the trajectories of particles driven across the surface to deviate from the direction of the force by an amount that depends on the particular characteristic, thus leading to sorting. While models of this behavior have provided a good understanding of these observations, the solutions have so far been primarily numerical. In this paper we provide analytic predictions for the dependence of the angle between the direction of motion and the external force on a number of model parameters for periodic as well as random surfaces. We test these predictions against exact numerical simulations.

In this work we investigate the dependence of characteristics of polarization recording and erasure in thin azopolymer films on the starting temperatures of the sample. Polarized light from DPSS laser with wavelength 444 nm is used for recording of photoinduced birefringence. For erasing the records, thermal method is applied. Birefringence is successfully recorded at different starting temperatures from 25 to 100°C. 3D graphics for visualization of the experimental data are presented. Photoinduced birefringence is calculated from real time monitored Stocks parameters during the entire experiment. This investigation allows us to determine the optimal conditions of recording at elevated temperatures in order to achieve shortest response time or maximal birefringence.

In this work we investigate the characteristics of reversible polarization recording in an azopolymer. Polarized light from DPSS laser with wavelength 444 nm is used for recording photoinduced birefringence. Afterwards, two methods for its erasure are used: heating the polymer to certain temperature or illumination with circularly polarized light. Multiple cycles of recording and erasure are successfully realized with both methods, which allows us to compare and outline the advantages of each of them. The photoinduced birefringence is calculated from the Stocks parameters, monitored in real time, during the entire experiment.

Reliably distinguishing between cells based on minute differences in receptor density is crucial for cell-cell or virus-cell recognition, the initiation of signal transduction and selective targeting in directed drug delivery. Such sharp differentiation between different surfaces based on their receptor density can only be achieved by multivalent interactions. Several theoretical and experimental works have contributed to our understanding of this "superselectivity", however a versatile, controlled experimental model system that allows quantitative measurements on the ligand-receptor level is still missing. Here, we present a multivalent model system based on colloidal particles equipped with surface-mobile DNA linkers that can superselectively target a surface functionalized with the complementary mobile DNA-linkers. Using a combined approach of light microscopy and Foerster Resonance Energy Transfer (FRET), we can directly observe the binding and recruitment of the ligand-receptor pairs in the contact area. We find a non-linear transition in colloid-surface binding probability with increasing ligand or receptor concentration. In addition, we observe an increased sensitivity with weaker ligand-receptor interactions and we confirm that the timescale of binding reversibility of individual linkers has a strong influence on superselectivity. These unprecedented insights on the ligand-receptor level provide new, dynamic information into the multivalent interaction between two fluidic membranes mediated by both mobile receptors and ligands and will enable future work on the role of spatial-temporal ligand-receptor dynamics on colloid-surface binding.

There has been a recent revolution in the ability to manipulate micrometer-sized objects on surfaces patterned by traps or obstacles of controllable configurations and shapes. One application of this technology is to separate particles driven across such a surface by an external force according to some particle characteristic such as size or index of refraction. The surface features cause the trajectories of particles driven across the surface to deviate from the direction of the force by an amount that depends on the particular characteristic, thus leading to sorting. While models of this behavior have provided a good understanding of these observations, the solutions have so far been primarily numerical. In this paper we provide analytic predictions for the dependence of the angle between the direction of motion and the external force on a number of model parameters for periodic as well as random surfaces. We test these predictions against exact numerical simulations.

Pressure experiments provide a unique opportunity to unravel new insights into glass-forming liquids by exploring its effect on the dynamics of viscous liquids and on the evolution of the glass transition temperature. Here we compare the pressure dependence of the onset of devitrification, Ton, between two molecular glasses prepared from the same material but with extremely different ambient-pressure kinetic and thermodynamic stabilities. Our data clearly reveal that, while both glasses exhibit different dTon/dP values at low pressures, they evolve towards closer calorimetric devitrification temperature and pressure dependence as pressure increases. We tentatively interpret these results from the different densities of the starting materials at room temperature and pressure. Our data shows that at the probed pressures, the relaxation time of the glass into the supercooled liquid is determined by temperature and pressure similarly to the behaviour of liquids, but using stability-depe...

Utilizing sequential layer-by-layer (LBL) coating and subsequent photopolymerization, we developed circularpolarizing and free-standing mirrors with a broad reflection bandwidth. Photopolymerizable cholesteric liquid crystal (CLC) paints were first prepared by considering the intrinsic chirality and the coating viscoelasticity. The polymerstabilized nanostructures had finely tuned helical pitches that selectively reflected light over the entire visible wavelength range. The CLC films exhibited excellent thermomechanical properties and chemical stabilities, which enabled the preparation of patterned optical objects at macroscopic dimensions. The LBL coating and photopolymerization of the CLC paints demonstrated here can provide a simple solution for manufacturing flexible photonic devices with large areas at low cost.

Star block-copolymers (SBCs) have been demonstrated to constitute self-assembling building blocks with specific softness, functionalization, shape, and flexibility. We study the behavior of star-block-copolymers (SBCs) suspensions under shear flow by means of particle-based multi-scale simulations. We analyze the conformational properties of low-functionality stars as well as the formation of attractive patches on their corona as a function of the shear rate for a wide range of parameters, including functionality, amphiphilicity, monomer packing fraction and solvent quality. For dense systems, we also analyze the dynamical behavior of the network structures formed at equilibrium as a consequence of the patch reorganization induced by the shear flow. The obtained results have interesting implications on the system's rheological properties and viscoelastic response in dilute and semidilute bulk phases. In the final part of this work, we propose two generalizations of the Multi-Par...

We report the formation of thin anisotropic phase gratings in a nematic liquid-crystalline film by use of lateral (fringing) electric fields induced by transparent interdigitated electrodes. These gratings yield high diffraction efficiency (>30%) with a strong dependence on the readout beam incidence angle. In addition, the formation of a defect wall is observed that has a significant effect on the diffraction properties of the phase grating.

The nature of the glass transition, the transformation of a liquid into a disordered solid, still remains one of the most intriguing unsolved problems in materials science. Recent models rationalize crucial features of vitrification with the presence of medium-range ordered regions coexisting with the isotropic liquid. Here, in line with this prediction, we report an extraordinary enhancement in bond orientational order in ultrathin films of supercooled polyols, grown by physical vapour deposition. By varying the deposition conditions and the molecular size, we could tune the kinetic stability of the liquid phase enriched in bond orientational order towards conversion into the ordinary liquid phase. We observed a strong increase in the dielectric strength with respect to the ordinary supercooled liquid and slower structural dynamics, suggesting the existence of a metastable liquid phase with improved orientational correlations.

Sucralose is a commonly employed artificial sweetener that appears to destabilize protein native structures. This is in direct contrast to the bio-preservative nature of its natural counterpart, sucrose, which enhances the stability of biomolecules against environmental stress. We have further explored the molecular interactions of sucralose as compared to sucrose to illuminate the origin of the differences in their bio-preservative efficacy. We show that the mode of interactions of sucralose and sucrose in bulk solution differ subtly through the use of hydration dynamics measurement and computational simulation. Sucralose does not appear to disturb the native state of proteins for moderate concentrations (<0.2 M) at room temperature. However, as the concentration increases, or in the thermally stressed state, sucralose appears to differ in its interactions with protein leading to the reduction of native state stability. This difference in interaction appears weak. We explored th...

In this work we investigate the dependence of characteristics of polarization recording and erasure in thin azopolymer films on the starting temperatures of the sample. Polarized light from DPSS laser with wavelength 444 nm is used for recording of photoinduced birefringence. For erasing the records, thermal method is applied. Birefringence is successfully recorded at different starting temperatures from 25 to 100°C. 3D graphics for visualization of the experimental data are presented. Photoinduced birefringence is calculated from real time monitored Stocks parameters during the entire experiment. This investigation allows us to determine the optimal conditions of recording at elevated temperatures in order to achieve shortest response time or maximal birefringence.

In this work we investigate the characteristics of reversible polarization recording in an azopolymer. Polarized light from DPSS laser with wavelength 444 nm is used for recording photoinduced birefringence. Afterwards, two methods for its erasure are used: heating the polymer to certain temperature or illumination with circularly polarized light. Multiple cycles of recording and erasure are successfully realized with both methods, which allows us to compare and outline the advantages of each of them. The photoinduced birefringence is calculated from the Stocks parameters, monitored in real time, during the entire experiment.

We characterize the self-assembly of colloidal particles with surface mobile DNA linkers under kinetically limited valence conditions. For this, we put forward a computer simulation model that captures quantitatively the interplay between the main dynamic processes governing these systems and allows the simulation of the long time scales reached in experiments. The model is validated by direct comparison with available experimental results, showing an overall good agreement that includes measurements of the average effective valence and its probability distribution as a function of the density of DNA linkers on the particles surface. Finally, simulation results are used to evidence the opposite impact of particle density and characteristic DNA hybridization time on the effective valence.

We present the phase diagram of a colloid-polymer mixture in which the radius a of the colloidal spheres is approximately the same as the radius R of a polymer coil (q = R/a ≈ 1). A three-phase coexistence region is experimentally observed, previously only reported for colloidpolymer mixtures with smaller polymer chains (q 0.6). A recently developed generalized freevolume theory (GFVT) for mixtures of hard spheres and non-adsorbing excluded-volume polymer chains gives a quantitative description of the phase diagram. Monte Carlo simulations also agree well with experiment.

A general formulation of boundary conditions for semiconductor-metal contacts follows from a phenomenological procedure sketched here. The resulting boundary conditions, which incorporate only physically well-defined parameters, are used to study the classical unipolar drift-diffusion model for the Gunn effect. The analysis of its stationary solutions reveals the presence of bistability and hysteresis for a certain range of contact parameters. Several types of Gunn effect are predicted to occur in the model, when no stable stationary solution exists, depending on the value of the parameters of the injecting contact appearing in the boundary condition. In this way, the critical role played by contacts in the Gunn effect is clearly established. ͓S1063-651X͑97͒04608-4͔

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A general formulation of boundary conditions for semiconductor-metal contacts follows from a phenomenological procedure sketched here. The resulting boundary conditions, which incorporate only physically well-defined parameters, are used to study the classical unipolar drift-diffusion model for the Gunn effect. The analysis of its stationary solutions reveals the presence of bistability and hysteresis for a certain range of contact parameters. Several types of Gunn effect are predicted to occur in the model, when no stable stationary solution exists, depending on the value of the parameters of the injecting contact appearing in the boundary condition. In this way, the critical role played by contacts in the Gunn effect is clearly established. ͓S1063-651X͑97͒04608-4͔

We report the thermodynamic measurement of the enthalpy released during the aging of supported films of a molecular glass former, toluene, at temperatures well below the glass transition temperature. By using microfabricated devices with very short equilibration times (below 1 s), we evidence a remarkable variation of the relaxation rate on decreasing film thickness from 100 nm down to a 7 nm thick film. Our results demonstrate that surface atoms are more efficient than bulk atoms in attaining low energy configurations within the potential energy landscape.

While lots of measurements describe the relaxation dynamics of the liquid state, experimental data of the glass dynamics at high temperatures are much scarcer. We use ultrafast scanning calorimetry to expand the timescales of the glass to much shorter values than previously achieved. Our data show that the relaxation time of glasses follows a super-Arrhenius behaviour in the high-temperature regime above the conventional devitrification temperature heating at 10 K/min. The liquid and glass states can be described by a common VFT-like expression that solely depends on temperature and limiting fictive temperature. We apply this common description to nearly-isotropic glasses of indomethacin, toluene and to recent data on metallic glasses. We also show that the dynamics of indomethacin glasses obey density scaling laws originally derived for the liquid. This work provides a strong connection between the dynamics of the equilibrium supercooled liquid and non-equilibrium glassy states.

While processing at elevated temperatures, starchy food products undergo gelatinization, which leads to softening related changes in textural characteristics. Study of role of gelatinization in texture development is limited; specifically, ignoring gelatinization physics can lead to erroneous prediction of Youngs modulus. In a recent work, we demonstrated a texture model that predicts local and effective Youngs moduli as functions of moisture content. While this model tracks experiments closely for drying, it deviates significantly from experiments for frying. In this paper, three different techniques for incorporating starch gelatinization are used to enhance the texture model, and the suitability of each technique is discussed. These improved models can capture the initial gelatinization induced softening and are in much better agreement with experiments. We expect that this work could contribute to better understanding and predictive capabilities of texture development.

We present a general theory for predicting the interaction potentials between DNA-coated colloids, and more broadly, any particles that interact via valence-limited ligand-receptor binding. Our theory correctly incorporates the configurational and combinatorial entropic factors that play a key role in valence-limited interactions. By rigorously enforcing self-consistency, it achieves near-quantitative accuracy with respect to detailed Monte Carlo calculations. With suitable approximations and in particular geometries, our theory reduces to previous successful treatments, which are now united in a common and extensible framework. We expect our tools to be useful to other researchers investigating ligand-mediated interactions.

The static yield stress of dielectric electrorheological(DER) fluids of infinite column state and chain state are calculated from the first principle method. The results indicate that the column surface contributions to ER effects is very small and both states will give correct results to the real DER fluids.

A correct description of phase behaviour in polymer solutions requires a coupling between configurational statistics and thermodynamics. The effect of flow-induced chain deformation on the polymer-solvent interaction energy depends on the concentration and on the polymer architecture. It will be demonstrated, using thermodynamic arguments, that for linear polymers this may give rise to a large flow-induced demixing. For more complex architectures such as ring polymers and branched polymers, a maximum in the critical temperature vs. flow rate is predicted.

Scientists have discovered an unprecedented phase transition during which crystals achieve amorphous characteristics while retaining their crystalline properties. [21] Cheng Chin, professor in the Department of Physics, and his team looked at an experimental setup of tens of thousands of atoms cooled down to near absolute zero. As the system crossed a quantum phase transition, they measured its behavior with an extremely sensitive imaging system. [20] Scientists from three UK universities are to test one of the fundamental laws of physics as part of a major Europe-wide project awarded more than £3m in funding. ]19] A team of researchers has devised a simple way to tune a hallmark quantum effect in graphene-the material formed from a single layer of carbon atoms-by bathing it in light. [18] Researchers from the University of Cambridge have taken a peek into the secretive domain of quantum mechanics.

La deposicion de capas a partir de la fase vapor se ha convertido recientemente en una herramienta muy potente de cara a la fabricacion de vidrios de una estabilidad sin precedentes. Los vidrios depositados a partir de la fase vapor pueden tener propiedades seleccionadas a medida, simplemente ajustando las condiciones de deposicion. En particular, los vidrios de maxima estabilidad se obtienen cuando la temperatura del substrato se encuentra alrededor de 0.85Tg. Por otra parte, la nanocalorimetria a altas velocidades de escaneo ha demostrado ser una herramienta muy util para la caracterizacion termica de la transicion vitrea, a temperaturas muy superiores a las exploradas habitualmente. Es esta tesis presentamos un estudio detallado de diferentes aspectos de la transicion vitrea en vidrios organicos de Indometacina y Celecoxib depositados a partir de la fase vapor. El estudio se ha realizado mediante el uso de diferentes tecnicas calorimetricas, desde calorimetria convencional, a nan...

Thin film stable glasses transform into a liquid by a moving front that propagates from surfaces or interfaces with higher mobility. We use calorimetric data of vapor-deposited glasses of different thicknesses and stabilities to identify the role of glassy and liquid dynamics on the transformation process. By invoking the existence of an ultrathin intermediate layer whose transformation strongly depends on the properties of both the liquid and the glass, we show that the recovery to equilibrium is driven by the mismatch in the dynamics between glass and liquid. The lifetime of this intermediate layer associated with the moving front is the geometric mean between the bulk transformation time and the alpha relaxation time. Within this view, we explain the observed dependencies of the growth front velocity and the crossover length with both stability and temperature. Extrapolation of these results points towards ordinary thin film glasses transforming via a frontlike transformation mechanism if heated sufficiently fast, establishing a close connection between vapor-deposited and liquid-cooled glasses.

The object of the present article is a 1d lattice-gas system comprised of soft-particles, wherein particles interact only if they occupy the same or a neighboring site, as a simple representation of penetrable particles of soft condensed matter. To represent different scenarios, two different realizations of the lattice model are considered, a one-component and a two-component system, where in the two-component case particles of the same species repel and those of opposite species attract each other. The systems are analyzed entirely within the transfer matrix framework. Special attention is paid to the criterion devised in Ref. [Phys. Rev. E 63, 031206 (2001)], which serves to separate two classes of behavior encountered in a one-component penetrable particle systems. In addition to confirm the existence of a similar criterion for the one-component lattice-gas model, we find that the same criterion can be applied to the two-component system to provide conditions for thermodynamic catastrophe.

In this letter we present the results of a study on fluid-fluid phase separation in binary mixtures. We have investigated two systems: a mixture interacting through the full a-exp-6 potential and a mixture interacting through the repulsive part of the a-exp-6 potential. Monte Carlo simulations were performed at 300 kelvin and the interaction parameter values used for the full potential correspond to the mixture helium-hydrogen. The results of the repulsive a-exp-6 potential demonstrate clearly that attraction is not necessary for fluid-fluid demixing; its only influence appears to be a shift of the critical pressure. The full a-exp-6 results are in good agreement with the experimental data.

Modelado de la biodegradación en biorreactores de lodos de hidrocarburos totales del petróleo intemperizados en suelos y sedimentos (Biodegradation modeling of sludge bioreactors of total petroleum hydrocarbons weathering in soil and sediments)

A general formulation of boundary conditions for semiconductor-metal contacts follows from a phenomenological procedure sketched here. The resulting boundary conditions, which incorporate only physically well-defined parameters, are used to study the classical unipolar drift-diffusion model for the Gunn effect. The analysis of its stationary solutions reveals the presence of bistability and hysteresis for a certain range of contact parameters. Several types of Gunn effect are predicted to occur in the model, when no stable stationary solution exists, depending on the value of the parameters of the injecting contact appearing in the boundary condition. In this way, the critical role played by contacts in the Gunn effect is clearly established. ͓S1063-651X͑97͒04608-4͔

We theoretically explain the complete sequence of shapes of deflated spherical shells. Decreasing the volume, the shell remains spherical initially, then undergoes the classical buckling instability, where an axisymmetric dimple appears, and, finally, loses its axisymmetry by wrinkles developing in the vicinity of the dimple edge in a secondary buckling transition. We describe the first axisymmetric buckling transition by numerical integration of the complete set of shape equations and an approximate analytic model due to Pogorelov. In the buckled shape, both approaches exhibit a locally compressive hoop stress in a region where experiments and simulations show the development of polygonal wrinkles, along the dimple edge. In a simplified model based on the stability equations of shallow shells, a critical value for the compressive hoop stress is derived, for which the compressed circumferential fibres will buckle out of their circular shape in order to release the compression. By ap...

We investigate wrinkling of two-dimensional random and triangular semiflexible polymer networks under shear. Both types of semiflexible networks exhibit wrinkling above a small critical shear angle, which scales with an exponent of the bending modulus between 1.9 and 2.0. Random networks exhibit hysteresis at the wrinkling threshold. Wrinkling lowers the total elastic energy by up to 20% and strongly affects the elastic properties of all semiflexible networks such as the crossover between bending and stretching dominated behavior. In random networks, we also find evidence for metastable wrinkled configurations. While the disordered microstructure of random networks affects the scaling behavior of wrinkle amplitudes, it has little effect on wrinkle wavelength. Therefore, wrinkles represent a robust, microstructure-independent assay of shear strain or elastic properties.

Elastic capsules, prepared from droplets or bubbles attached to a capillary (as in a pendant drop tensiometer), can be deflated by suction through the capillary. We study this deflation and show that a combined analysis of the shape and wrinkling characteristics enables us to determine the elastic properties in situ. Shape contours are analyzed and fitted using shape equations derived from nonlinear membrane-shell theory to give the elastic modulus, Poisson ratio and stress distribution of the membrane. We include wrinkles, which generically form upon deflation, within the shape analysis. Measuring the wavelength of wrinkles and using the calculated stress distribution gives the bending stiffness of the membrane. We compare this method with previous approaches using the Laplace-Young equation and illustrate the method on two very different capsule materials: polymerized octadecyltrichlorosilane (OTS) capsules and hydrophobin (HFBII) coated bubbles. Our results are in agreement with the available rheological data. For hydrophobin coated bubbles the method reveals an interesting nonlinear behavior consistent with the hydrophobin molecules having a rigid core surrounded by a softer shell.

When a spherical elastic capsule is deflated, it first buckles axisymmetrically and subsequently loses its axisymmetry in a secondary instability, where the dimple acquires a polygonal shape. We explain this secondary polygonal buckling in terms of wrinkles developing at the inner side of the dimple edge in response to compressive hoop stress. Analyzing the axisymmetric buckled shape, we find a compressive hoop stress with parabolic stress profile at the dimple edge. We further show that there exists a critical value for this hoop stress, where it becomes favorable for the membrane to buckle out of its axisymmetric shape, thus releasing the compression. The instability mechanism is analogous to the formation of wrinkles under compressive stress. A simplified stability analysis allows us to quantify the critical stress for secondary buckling. Applying this secondary buckling criterion to the axisymmetric shapes, we can determine the critical volume for secondary buckling. Our analytical result is in close agreement with existing numerical data.

Reconfigurable optical materials are critical to realizing light control in eyewear or architectural windows. Here, we report on the electrical reconfiguration of the selective reflection of cholesteric liquid crystals (LCs). The distinctive responses detailed here are enabled by the preparation of a structurally chiral polymer stabilizing network that enforces anchoring of a lowmolar-mass liquid crystalline media with positive dielectric anisotropy. The pitch of the reflective optical elements is directly regulated by a dc field, resulting in red or blue reflection wavelength tuning or broadening. The use of the positive dielectric LC host in concert with optimization of the material preparation conditions allows for reorientation of the LC molecules to achieve an optically clear state (homeotropic orientation) by the application of an ac field. In this way, the selective reflection of the optical elements can be moved, widened, and turned on and off. The electro-optic characteristics of these materials are another step forward to enabling the use of these materials in optics and photonics.

Bulk phase separation is responsible for the occurrence of stacks of different layers in sedimentation of colloidal mixtures. A recently proposed theory (de las Heras and Schmidt 2013 Soft Matter 9 8636) establishes a unique connection between the bulk phase behaviour and sedimentationdiffusion-equilibrium. The theory constructs a stacking diagram of all possible sequences of stacks under gravity in the limit of very high (infinite) sample heights. Here, we study the stacking diagrams of colloidal mixtures at finite sample height, h. We demonstrate that h plays a vital role in sedimentation-diffusion-equilibrium of colloidal mixtures. The region of the stacking diagram occupied by a given sequence of stacks depends on h. Hence, two samples with different heights but identical colloidal concentrations can develop different stacking sequences. In addition, the stacking diagrams for different heights can be qualitatively different since some stacking sequences occur only in a given interval of sample heights. We use the theory to investigate the stacking diagrams of both model bulk systems and mixtures of patchy particles that differ either by the number or by the types of patches.

We report on the buckling and subsequent collapse of orthotropic elastic spherical shells under volume and pressure control. Going far beyond what is known for isotropic shells, a rich morphological phase space with three distinct regimes emerges upon variation of shell slenderness and degree of orthotropy. Our extensive numerical simulations are in agreement with experiments using fabricated polymer shells. The shell buckling pathways and corresponding strain energy evolution are shown to depend strongly on material orthotropy. We find surprisingly robust orthotropic structures with strong similarities to stomatocytes and tricolpate pollen grains, suggesting that the shape of several of Nature's collapsed shells could be understood from the viewpoint of material orthotropy. FABRICATION OF ORTHOTROPIC SPHERICAL SHELLS FIG. S1. (a) Hemispherical cap with four layers on a sphere of radius 110 mm. (b) Complete spherical shell after curing.

Phase transitions in one-dimensional classical fluids are usually ruled out by making appeal to van Hove's theorem. A way to circumvent the conclusions of the theorem is to consider an interparticle potential that is everywhere bounded. Such is the case of, e.g., the generalized exponential model of index 4 (GEM-4 potential), which in three dimensions gives a reasonable description of the effective repulsion between flexible dendrimers in a solution. An extensive Monte Carlo simulation of the one-dimensional GEM-4 model [S. Prestipino, Phys. Rev. E 90, 042306 (2014)] has recently provided evidence of an infinite sequence of low-temperature cluster phases, however also suggesting that upon pushing the simulation forward what seemed a true transition may eventually prove to be only a sharp crossover. We hereby investigate this problem theoretically, by three different and increasingly sophisticated approaches ( i.e., a mean-field theory, the transfer matrix of a lattice model of c...

Sucralose is a commonly employed artificial sweetener that appears to destabilize protein native structures. This is in direct contrast to the bio-preservative nature of its natural counterpart, sucrose, which enhances the stability of biomolecules against environmental stress. We have further explored the molecular interactions of sucralose as compared to sucrose to illuminate the origin of the differences in their bio-preservative efficacy. We show that the mode of interactions of sucralose and sucrose in bulk solution differ subtly through the use of hydration dynamics measurement and computational simulation. Sucralose does not appear to disturb the native state of proteins for moderate concentrations (<0.2 M) at room temperature. However, as the concentration increases, or in the thermally stressed state, sucralose appears to differ in its interactions with protein leading to the reduction of native state stability. This difference in interaction appears weak. We explored th...