Particles In Solution Research Articles

Synthesis of a magneto-chromatic tunable Fe3O4-HPAM colloid

Colloids of soft magnetic (Fe3O4) submicrometer particles, formed by magnetic nanoparticle clusters, coated with a polyelectrolyte (hydrolyzed polyacrylamide; HPAM) were fabricated successfully in situ with a highly controllable chemical approach. The formation mechanism of submicron particles was analyzed under the amounts of HPAM, urea, citrate, and metallic precursors. This mechanism was followed by SEM. The results showed that the physicochemical properties of the HPAM favored physical interactions with the reactants, promoting the formation of dense-packed magnetic micrometer clusters in one-step synthesis. The results showed that the physicochemical properties of the HPAM favored physical interactions with the reactants, promoting the formation of dense-packed magnetic micrometer clusters in one-step synthesis. The different estimated radii of these particles in solution (hydrodynamic and gyration) and dried (internal radius) decrease when the HPAM amount increases. Moreover, the particles exhibited a superparamagnetic behavior with a magnetization of 48.2 emu/g, 50.3 emu/g, and 54.3 emu/g when the amounts were 0.5 g, 1 g, and 2g of HPAM, respectively. Consequently, the optical response of the colloids to the application of a rotating magnetic field (RMF) parallel to the horizontal plane where they were located exhibited a behavior similar to photonic structures since their reflection spectrum showed a periodic diffraction color that closely matches the frequency of the RMF.

Variability of travel time of solute particles in single fractures with spatially variable aperture

The arrival time of solutes from the source to a prescribed compliance boundary is a global transport quantity that is of practical interest in many applications, such as risk assessment for environmentally sensitive sites in regulatory analyses. Estimates of uncertainty are necessary and can play an important role in the decision-making process. The objective of this work is therefore to quantify the variability of solute travel time in individual fractures with spatially variable apertures. The variability of solute transport in fractures is largely determined by the heterogeneity of the apertures of naturally occurring rock fractures. To model solute transport, the fracture apertures and flow fields are considered as spatial random functions. Using the relationship between the two-dimensional depth-averaged solute conservation equation and the Fokker-Planck equation, it is possible to formulate the solute convection velocity in such a way that a general expression for the solute travel time variance can be developed by taking into account the effects of the variation in fracture aperture. A closed-form expression for the variance of travel time in the mean flow direction is derived for the case of advection-dominated solute transport. This derived expression allows the analysis of the effects of the variation of the fracture aperture on the variability of the solute travel time.

Competition between hydrogen bonding and electrostatic repulsion in pH-switchable emulsions

Electrostatic interactions and hydrogen bonding play important roles in the stabilization of self-assembled systems. However, the competition between hydrogen bonding and electrostatic repulsion in emulsions hasn’t been reported. Herein, we report on electrostatic repulsion overcoming hydrogen bonding in oil-in-water (O/W) emulsions prepared by the mixture of escin and hydrophilic silica nanoparticles triggered by pH, in which the location of the nanoparticles is reversibly transformed from being adsorbed at the oil–water interface to being dispersed in the continuous phase. Escin adsorbs on silica particles in alkaline solution by its hydroxyl groups to endow the particles with surface activity, yielding a stable Pickering emulsion. However, such adsorption via hydrogen bonding is reversed by electrostatic repulsion between carboxylate ions and negatively charged silica particles after escin was converted to sodium aescinate. Demulsification occurred after silica particles reverted to being hydrophilic, which could further co-stabilize the oil-in-dispersion (OID) emulsions with sodium aescinate through electrostatic repulsion after re-homogenization. Pickering or OID emulsions with high internal phase volume fraction could also be obtained. This strategy is universal for O/W emulsions stabilized by nanoparticles and similarly charged surfactants with a polar headgroup near the nonionic functional group, e.g. silica plus polyoxyethylene lauryl ether carboxylate. This work aids in understanding the role of electrostatic repulsion and hydrogen bonding in stabilizing emulsions and sheds light on the design of smart surfactants for practical applications.

Impact of Low-Reactivity Calcined Clay on the Performance of Fly Ash-Based Geopolymer Mortar

Availability of aluminosiliceous materials is essential for the production and promotion of geopolymer concrete. Unlike fly ash, which can only be found in industrial regions, clays are available almost everywhere but have not received sufficient attention to their potential use as a precursor for geopolymer synthesis. This study investigates the effectiveness of calcined clay as a sole and binary precursor (with fly ash) for the preparation of geopolymer mortar. Fly ash-based geopolymer containing between 0 and 100% low-grade calcined clay was prepared to investigate the effect of calcined clay replacement on the geopolymerization process and resultant mortar, using a constant liquid/solid ratio. Reagent-grade sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) were mixed and used for the alkali solution preparation. Six different mortar mixes were formulated using sand and the geopolymer binder, comprising varying fly ash-to-calcined clay ratios. The combined effect of the two source materials on compressive strength, setting time, autogenous shrinkage, and porosity was studied. The source materials were characterized using XRD, SEM, FTIR, and XRF techniques. Isothermal calorimetry was used to characterize the effect of low-grade calcined clay on the geopolymerization process. The addition of calcined clay reduced the surface interaction between the dissolved particles in the alkali solution, leading to slow initial reactivity. Geopolymer mortar containing 20% calcined clay outperformed the reference geopolymer mortar by 5.6%, 17%, and 18.5% at 7, 28, and 91 days, respectively. The MIP analysis revealed that refinement of the pore structure of geopolymer specimens containing calcined clay resulted in the release of tensional forces within the pore fluid. Optimum replacement was found to be 20%. From this study, the mutual reliance on the physical and inherent properties of the two precursors to produce geopolymer mortar with desirable properties has been shown. The findings strongly suggest that clay containing low content of kaolinite can be calcined and added to fly ash, together with appropriate alkali activators, to produce a suitable geopolymer binder for construction applications.

Interpretable machine learning-based analysis of mechanical properties of extruded Mg-Al-Zn-Mn-Ca-Y alloys

In this study, the mechanical properties of as-extruded Mg-Al-Zn-Mn-Ca-Y alloys were quantitatively investigated with respect to alloying elements, extrusion temperature, microstructure and texture through interpretable machine learning (IML). To overcome the lack of data, two methods were devised to augment the existing dataset by 39 times using the mean and standard deviation of the measured data. Artificial neural networks predicted room-temperature tensile properties with an accuracy ranging from 0.842 to 0.997 based on R2 using 12 predictors for a total of 1179 data points. Shapley additive explanation identified that Al and Mn are the key determinants for strength and elongation, respectively. Partial dependence plots investigated the interaction of all features to understand the quantitative correlation between features. This IML approach revealed that texture, solid solution and secondary particles are related to the main strengthening mechanism of as-extruded Mg alloys. These results can provide insights into the utilization of IML approach to predict material properties and describe key variables for designing lightweight structural metals.

ANTIMICROBIAL AND HISTOLOGICAL EFFECTS OF NANO-NEOMYCIN SOLUTION AGAINST DIFFERENT MICROBIAL POPULATION

In the present study, pomegranate nanoparticles solution was synthesized by Sol gel method. Which show hexagonal morphology with size average (50±10) nm scanned by (SEM) and (TEM). The synergestic solution of (Neomycin and Nano-Pomegranate extract) scanned by Atomic Force Microscopy (AFM) analysis provided the information about the distribution of particles in new solution. Beside the phenolic compounds, flavonoids and tannin played crucial role in the significant antibacterial activity and the synergestic solution observed in F1 and F2 at range (9.5-12.5) mm against Staphylococcus aurous, E. coli between (5-11.5) mm, Bacillus sp. (3.9-5.5); Proteus vulgaris (4.1-5.1) mm; Salmonella typhimurium at ranges (5.8-6.5) mm, klebsiella pneumonia (3.8-4.8) mm and listeria monocytogenes (3.9-5.6) mm. the Synergistic effect of the solution increased the efficacy of their work compared to used them individually, this was shown through increasing the inhibition zone. These results were demonstrated through histopathological examination to organs examined, that identical to normal when given different concentrations of these solutions, and proof of their non-toxicity. Overall, the results elucidated a rapid, costeffective, environmentally friendly and convenient method for synthesis, which could be used as a potential antimicrobial agent against multidrug-resistant bacteria.

Stochastic Dynamics of Two‐Dimensional Particle Motion in Darcy‐Scale Heterogeneous Porous Media

AbstractWe study the upscaling and prediction of ensemble dispersion in two‐dimensional heterogeneous porous media with focus on transverse dispersion. To this end, we study the stochastic dynamics of the motion of advective particles that move along the streamlines of the heterogeneous flow field. While longitudinal dispersion may evolve super‐linearly with time, transverse dispersion is characterized by ultraslow diffusion, that is, the transverse displacement variance grows asymptotically with the logarithm of time. This remarkable behavior is linked to the solenoidal character of the flow field, which needs to be accounted for in stochastic models for the two‐dimensional particle motion. Here, we derive an upscaled model based on the statistical characterization of the motion of solute particles. To this end, we analyze particle velocities and orientations through equidistant sampling along the particle trajectories obtained from direct numerical simulations. This sampling strategy respects the flow structure, which is organized on a characteristic length scale. Perturbation theory shows that the longitudinal particle motion is determined by the variability of travel times, while the transverse motion is governed by the fluctuations of the space increments. The latter turns out to be strongly anticorrelated with a correlation structure that leads to ultraslow diffusion. Based on this analysis, we derive a stochastic model that combines a correlated Gaussian noise for the transverse motion with a spatial Markov model for the particle speeds. The model results are contrasted with detailed numerical simulations in two‐dimensional heterogeneous porous media of different heterogeneity variances.

Transient dynamic electrophoresis of a spherical colloidal particle.

A general theory is presented for the transient dynamic electrophoresis of a spherical colloidal particle in an electrolyte solution under a suddenly applied oscillating electric field. An approximate analytic expression is derived for the transient dynamic electrophoretic mobility, which is applicable for low particle zeta potentials and arbitrary Debye length. It is found that the electrophoretic mobility shows a damped oscillation, approaching its final value, unlike the case where a step electric field is applied.

MISPSO-Attack: An efficient adversarial watermarking attack based on multiple initial solution particle swarm optimization

The vulnerability of deep learning models to adversarial attacks is a growing concern, as the emergence of adversarial samples exposes almost all models to the risk of such attacks. This paper proposes a new method for adversarial attacks through watermarking. Our goal is to leverage the properties of adversarial samples to prevent people’s images from being maliciously collected and compared, thereby avoiding the leakage of private information. Our method, which improves on the multi-swarm particle swarm optimization (MPSO) algorithm, outperforms existing similar methods on two popular computer vision datasets. We conducted attack experiments on the widely used Imagenet dataset and achieve the highest attack success rate of 89.50%. The experimental results demonstrate the superiority of our method over existing similar methods. We simulate the attacks on the online social environment using two face photographs datasets and face recognition models. Our method reaches the best deception performance compared to similar methods, with the highest success rate of 97.03%, demonstrating our approach’s ability to protect individuals’ privacy. Furthermore, we investigate the natural causes of adversarial samples and demonstrate their inevitability, providing valuable insights for developing more robust deep models. The source code of the proposed method is available online at: https://github.com/grandwang/main_attack.

Solute transport in highly heterogeneous media: The asymptotic signature of connectivity

The connectivity of the more conductive hydrofacies strongly determines flow and transport in heterogeneous media. Here we study solute transport in 3D binary isotropic samples with a proportion p of a high hydraulic conductivity facies (k+), and (1−p) of a low (k−) one. The k+ facies is characterized by two connectivity parameters: a connectivity structure type (no, low, intermediate and high), that controls how well the k+ facies is connected, and an integral scale Ib, that controls the heterogeneity characteristic lengthscale. Under ergodic conditions, and in the asymptotic Fickian regime that arises only very far from the injection plane, we analyze two transport quantities: the normalized mean solute arrival time 〈ta∗〉, and the longitudinal dispersivity αL. As p reaches the percolation threshold pc (pc depends on the connectivity parameters), k+ channels spanning the sample along the mean flow direction appear, giving rise to fast flow pathways . A sharp decrease of 〈ta∗〉, and a sharp increase of αL, occur when p→pc. As p exceeds pc, a subsequent minimum of 〈ta∗〉 and a maximum of αL are observed. This result is in contrast with previous ones by other authors that found a maximum of αL at p=pc. On the other hand, p kept fixed, αL decreases as the connectivity of the k+ facies increases. We conclude that the connectivity features sampled by the solute particles during their trajectories are retained in the transport quantities even after the asymptotic regime is attained. Also, that connectivity mainly affects αL through a shift or displacement of pc. Finally, the existence of a spatial connectivity structure may imply early, but also late, arrival times, compared with the absence of structure.

Particle Network Self-Assembly of Similar Size Sub-Micron Calcium Alginate and Polystyrene Particles Atop Glass.

Particle-mediated self-assembly, such as nanocomposites, microstructure formation in materials, and core-shell coating of biological particles, offers precise control over the properties of biological materials for applications in drug delivery, tissue engineering, and biosensing. The assembly of similar-sized calcium alginate (CAG) and polystyrene sub-micron particles is studied in an aqueous sodium nitrate solution as a model for particle-mediated self-assembly of biological and synthetic mixed particle species. The objective is to reinforce biological matrices by incorporating synthetic particles to form hybrid particulate networks with tailored properties. By varying the ionic strength of the suspension, the authorsalter the energy barriers for particle attachment to each other and to a glass substrate that result from colloidal surface forces. The particles do not show monotonic adsorption trend to glass with ionic strength. Hence, apart from DLVO theory-van der Waals and electrostatic interactions-the authors further consider solvation and bridging interactions in the analysis of the particulate adsorption-coagulation system. CAG particles, which support lower energy barriers to attachment relative to their counterpart polystyrene particles, accumulate as dense aggregates on the glass substrate. Polystyrene particles adsorb simultaneously as detached particles. At high electrolyte concentrations, where electrostatic repulsion is largely screened, the mixture of particles covers most of the glass substrate; the CAG particles form a continuous network throughout the glass substrate with pockets of polystyrene particles. The particulate structure is correlated with the adjustable energy barriers for particle attachment in thesuspension.

Influence of Current Density upon Hydrogenation on the Shape Memory Effect of Binary TiNi Alloy Single Crystals

Some results concerning the hydrogen effect at electrolytic saturation at a current density of j = 1500 and 3500 A/m2 for 3 h at room temperature on the temperature dependence of the yield stress σ0.1(T) and the shape memory effect (SME) under tension of the [011]-oriented Ti-50.55%Ni (at.%) alloy single crystals are presented. It was shown that hydrogen is in a solid solution and forms particles of titanium hydride TiH2 after hydrogenation at j = 1500 and 3500 A/m2, respectively. Both hydrogen in the solid solution and TiH2 particles led to a decrease in the Ms temperature of the onset of the forward martensitic transformation (MT) upon cooling and the Md temperature (Md is the temperature at which the stresses for the onset of the stress-induced MT are equal to the stresses for the onset of plastic flow of the high-temperature B2 phase), and increased the yield stress σ0.1 of the B2 phase at the Md temperature compared to hydrogen-free crystals. It was found that the SME under stress depends on the tensile stress level and current density. The maximum SME εSME = 10 ± 0.2% at σex = 200 MPa and εSME = 10.5 ± 0.2% at σex = 300 MPa was observed in the hydrogen-free crystals and after hydrogenation at j = 1500 A/m2, respectively, which exceeded the theoretical value of lattice deformation ε0 = 8.95% for the B2-B19′ MT in [011] orientation under tension. At j = 1500 A/m2, the physical reason for the excess of the SME of the theoretical ε0 value was due to the increase in the plasticity of B19′ martensite upon hydrogenation. At j = 3500 A/m2, εSME = 8.0 ± 0.2%, and it was less than ε0 = 8.95% for B2-B19′ MT in [011] orientation under tension. The decrease in SME after hydrogenation at j = 3500 A/m2 was associated with the interaction of two types of B19′-martensite: oriented under stress and non-oriented, formed near TiH2 particles. It was shown that the redistribution of hydrogen in the bulk of the crystals during long-term holding for 168 h at 263 K after hydrogenation at j = 1500 A/m2 increases the SME relative to crystals without long-term holding: 3.5 times at 50 MPa and 1.8 times at 100–150 MPa. After long-term holding, εSME = 9.5 ± 0.2% at 150 MPa, which exceeds the theoretical value ε0 = 8.95% for B2-B19′ MT in [011] orientation under tension.

Analytical Dependence of the Probability of Masking Objects on the Density and Dispersion of the Aerosol

With the existing method for evaluating the effectiveness of masking objects with aerosols, two parameters are used: the length and width of an invisible smoke screen with a probability of at least 50 %. Both parameters were obtained during the practical tests of aerosol masking means. However, they are insufficient for assessing the masking ability of an aerosol cloud as a spatial formation. The purpose of this work is to reveal the analytical dependence of the probability of objects masking on the density and dispersion of the aerosol. Мaterials and methods. An extended approach was used to estimate the probability of masking at any theoretical value of the flux density (integral concentration, g/m2) of aerosol along the line of sight, taking into account its dispersion, by calculating the formation of a probability field from 5 to 95 % over the entire spatial structure of the aerosol cloud. The method used is the simulation on a PC of the dependence of the share of space occlusion for the observer (the eyepiece of an optical device) by aerosol particles of a given dispersion and flux density, which we took as the probability of masking. Discussion. It is shown in the article, that the resulting analytical expression as a result of processing the accumulated simulation results on a PC fully corresponds to the Bouguer-Lambert-Beer law, which is a generalization of many years of practical field and laboratory experiments with aerosols in the air and dispersed particles in solutions. The obtained probability values allow us to obtain a generalized efficiency criterion in the form of a new concept - the reduced masking zone. This term is mathematically analogous to the reduced impact zone, which is used to assess damage caused by munitions. Conclusion. For a full assessment of the effectiveness of aerosol countermeasures, the reduced masking zone must be calculated for all possible lines of sight (observation of an object): horizontally, vertically, and along inclined paths. This condition reflects the method of using modern weapons such as Javelin anti-tank systems, which are aimed at the target mainly horizontally, and the final trajectory before the impact is a «hill». The theoretical difference between the values of vertical and horizontal masking screens, obtained by the authors using a new method for calculating the parameters of an aerosol cloud, is presented in the illustrations to the article.

Electrochemical co-deposition of carbon nanotube/Ni composite layer

The type and content of particles in the plating solution greatly affect the electrodeposition process, making it important to study the effect of carbon nanotubes (CNTs) on the electrodeposition of nickel during the preparation of CNTs/Ni composites. In this paper, cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometric analysis (CA), and electrochemical impedance spectroscopy (EIS) were adopted to study the nucleation mechanism in the early stage of electrocrystallization. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) were used to reveal the electrocrystallization properties. The results showed that Ni was electrodeposited by 3D nucleation/growth and was controlled by diffusion and electrochemical kinetics. Increasing the CNTs concentration shortened the time required for 3D growth. Additionally, the polarizability of the electrodeposited nickel increased upon increasing the CNTs content, which helped increase the electro-crystallization probability of Ni. As the concentration of CNTs increased, the charge transfer resistance decreased, the Ni nucleation activation energy decreased, and the Ni nucleation became easier. The introduction of CNTs changed the preferred growth orientation of pure nickel, and the surface growth morphology was mainly a spiral in a stepwise pyramid.

Solute segregation and nanoparticle dispersion induced super high stability in a bulk nanocrystalline W-based alloy

Improvement of the stability of nanocrystalline (NC) materials is always a challenge. In this paper, the high thermal stability is achieved in a representative NC W alloy by combining nano-segregation of Ti solute to W grain boundary (GBs), and in-situ formation of nano Ti–Zr–O particles, which provide both thermodynamic and kinetic stabilization effects through solute dragging and particle pinning. The recrystallization temperature of this bulk NC W alloy reaches up to 1600 °C, and these nanometric microstructures maintain stable under a long-time and high-temperature ordeal up to 1200 °C for 120 h. And its microhardness and micro-compressive yield strength are ∼17.0 and 5.14 GPa, respectively. In addition, this bulk NC W alloy has high irradiation stability due to the high densities of stabled GBs and phase boundaries. This work demonstrates the possibility of attaining high-stability bulk NC materials in terms of segregation of solutes at GBs and in-situ formation of ultrafine nanoparticles with a coherent interface with the W matrix.

An investigation of the transient electrophoresis of conducting colloidal particles in porous media using a cell model

A comprehensive analytical study of the electrophoresis of a suspension of charged spherical particles in an arbitrary electrolyte solution through a porous medium is analyzed using a unit cell model. The unsteady Brinkman equation with the term of the electric force governing the fluid velocity fields is solved by means of the Laplace transform. The porous medium is uniformly charged by fixed charge density Q, and the embedded spherical particle is conductive and charged with constant zeta potential. Two different accurate concepts of the boundary conditions at the outer virtual surface, are presented to solve the governing equations for the flow field. Steady-state electrophoretic velocity is obtained analytically and displayed graphically for different physical parameters. Also, a closed form of the transient electrophoretic velocity versus the dimensionless elapsed time is plotted and discussed for different values of the Debye length parameter, particle volume fraction, density ratio, permeability of the porous medium, and for highly- and non-conducting particles. The steady/ transient electrophoretic velocity is a monotonic decreasing function of the permeability parameter, the particle-to-fluid density ratio, and the particle volume fraction, but it increases with an increase in the Debye length parameter with constant zeta potential. In general, the Kuwabara cell model predicts a smaller value for the electrophoresis velocity than the Happel model, but the difference is not significant. On the other hand, when the transient velocity is normalized by its steady state, the Happel model has smaller values than the Kuwabara model. The effects of the relevant parameters on the transient starting electrokinetic flow in the porous medium are interesting and significant. The results are found to be in excellent agreement with the exact numerical results obtained by Lai and Keh.

Size-Dependent Diffusion and Dispersion of Particles in Mucin.

Mucus, composed significantly of glycosylated mucins, is a soft and rheologically complex material that lines respiratory, reproductive, and gastrointestinal tracts in mammals. Mucus may present as a gel, as a highly viscous fluid, or as a viscoelastic fluid. Mucus acts as a barrier to the transport of harmful microbes and inhaled atmospheric pollutants to underlying cellular tissue. Studies on mucin gels have provided critical insights into the chemistry of the gels, their swelling kinetics, and the diffusion and permeability of molecular constituents such as water. The transport and dispersion of micron and sub-micron particles in mucin gels and solutions, however, differs from the motion of small molecules since the much larger tracers may interact with microstructure of the mucin network. Here, using brightfield and fluorescence microscopy, high-speed particle tracking, and passive microrheology, we study the thermally driven stochastic movement of 0.5-5.0 μm tracer particles in 10% mucin solutions at neutral pH, and in 10% mucin mixed with industrially relevant dust; specifically, unmodified limestone rock dust, modified limestone, and crystalline silica. Particle trajectories are used to calculate mean square displacements and the displacement probability distributions; these are then used to assess tracer diffusion and transport. Complex moduli are concomitantly extracted using established microrheology techniques. We find that under the conditions analyzed, the reconstituted mucin behaves as a weak viscoelastic fluid rather than as a viscoelastic gel. For small- to moderately sized tracers with a diameter of lessthan 2 μm, we find that effective diffusion coefficients follow the classical Stokes-Einstein relationship. Tracer diffusivity in dust-laden mucin is surprisingly larger than in bare mucin. Probability distributions of mean squared displacements suggest that heterogeneity, transient trapping, and electrostatic interactions impact dispersion and overall transport, especially for larger tracers. Our results motivate further exploration of physiochemical and rheological mechanisms mediating particle transport in mucin solutions and gels.

Microchemistry evolution during industrial DC casting and subsequent homogenization of aluminum alloy AlMn0.5Mg0.5 (AA 3105)

The properties of non-heat treatable Al wrought alloys are influenced by the materials microchemistry in terms of the portion of alloying elements either in solid solution or in precipitated form. In the present study we analyze the phase selection during solidification as well as the changes in solute level and particle state during subsequent homogenization of the Al-Mn alloy AA 3105 (ISO AlMn0.5Mg0.5). Characterization of the microchemistry reactions is performed by a combination of optical and scanning electron microscopy with differential scanning calorimetry and measurements of thermoelectric power as well as specific electrical resistivity. The results are underpinned by CALPHAD simulations of the second-phase particles in the as-cast state, while the changes in solute level as well as volume, size and type of second-phase particles during homogenization are tracked with a statistical microchemistry simulation tool named ClaNG. Owing to the high Si content of the present alloy the as-cast state is dominated by α-Al(Fe,Mn)Si phase constituent particles together with a few Al6(Mn,Fe) and Mg2Si phases. Homogenization is characterized by the formation and redissolution of Mg2Si and, at higher temperatures, dispersoids of the α-Al(Fe,Mn)Si phase.

Influence of various colloidal surfactants on the stability of MS2 bacteriophage suspension. The charge distribution on the PCV2 virus surface

To understand virus stability in aqueous solutions, the colloidal nanostructure and properties of a model virus, the MS2 bacteriophage, have been investigated by studying the effect of the addition of electrolytes and various colloidal surfactants to its water solution at physiological conditions. The charge of the virus particles influences their colloidal properties. It was found that the ζ-potential value is reduced from –35 mV to –10 mV in 0.01 M CaCl2 and 0.1 M NaCl solutions as well as at higher electrolytes concentrations, while the size of the MS2 aggregates was about 600 ÷ 900 nm with individual particles of size around 30 nm also recorded. The 2 :1 electrolyte causes destabilization of MS2 bacteriophage particles in an aqueous solution at a lower concentration. The addition of cationic, anionic, and non-ionic colloidal surfactants below and above critical micelle concentration to MS2 bacteriophage suspension caused the destabilization of MS2 particles. We also investigated the capsid’s surface of another virus, PCV2, using dynamic light scattering and laser Doppler electrophoresis. The hydrodynamic diameter and the ζ-potential of PCV2 empty capsid were found to be equal to 22 ± 1 nm and −41 ± 4 mV (using Ohshima approximations). The electrostatic potential of the surface was measured using acid-base probes and found to be equal to −91 ± 3 and +14 ± 2 mV for positively and negatively charged probes respectively, which indicate the ‘mosaic’ way of the charge distribution on the surface, similar to MS2′s surface studied previously. Our data provide new information about the virus surface, the complex process of virus aggregation-disaggregation and virus capsid disassembly.

Anharmonicity and the emergence of diffusive behavior in a lattice-solute model solid-state electrolyte

We have investigated atomic transport properties in a simple two-component solid-state material using molecular dynamics simulations. This model system is composed of a lattice element and a solute. The former is modeled after carbon, which forms a covalent diamond lattice that provides the supporting structure for the solute, which interacts with carbon and with itself via Lennard-Jones potentials. The size of the solute species is systematically varied while maintaining a constant system volume. The change in solute particle size is quantified using an atomic packing fraction, which is used as a mediator variable to find relationships between the internal pressure of the system, its vibrational properties, and the change in diffusivity of the mobile species. The data imply a causal relationship between structural instabilities, reflected in the internal pressure and compressibility curves, the vibrational spectra, and the onset of a diffusive regime manifest in an increase in atomic mobility by orders of magnitude.