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Polymer informatics is an emerging discipline that has benefited from the strong development that data science has experienced over the last decade. Machine learning methods are useful to infer QSPR (Quantitative Structure-Property Relationships) models that allow predicting mechanical properties related to the industrial profile of polymeric materials based on their structural repeating units (SRUs). Nonetheless, the chemical structure of the SRU is only one of the many factors that affects the industrial usefulness of a polymer. Other equally relevant factors are polymer molecular weight, molecular weight distribution, and production method, which are related to the inherent polydispersity of this kind of material. For this reason, the computational characterization used for the building of QSPR models for predicting mechanical properties should consider these main factors. The aim of this paper is to highlight recent advances in data science to address the inclusion of polydispersity information of polymeric materials in QSPR modeling. We present two dimensions of discussion: data representation and algorithmic issues. In the first one, we examine how different strategies can be applied to include polydispersity data in the molecular descriptors that characterize the polymers. We explain two data representation approaches designed by our group, named as trivalued and multivalued molecular descriptors. In the second dimension, we discuss algorithms proposed to deal with these new molecular descriptor representations during the construction of the QSPR models. Thus, we present here a comprehensible and integral methodology to address the challenges that polydispersity generates in the QSPR modeling of mechanical properties of polymers.

Eudragit® polymers have proven their potential as a means to control the release of aqueous insoluble drugs in various delivery systems as polymer nanoparticles (PNPs). The size (S) and polydispersity index (PDI) of PNPs are crucial factors for their interaction with biological systems from a pharmaceutical standpoint. This study aimed to determine the impact of the volumes of the organic phase (OP) and aqueous phase (AP), as well as the polymer amount (PA), on the size and PDI of PNPs prepared using the nanoprecipitation method for encapsulating quercetin (Qr). The study also evaluated the toxic effects of PNPs on human erythrocytes. The PNPs were prepared using preformed polymers derived from methacrylic acid and polyvinyl alcohol (PVA) as a surfactant. The nanoprecipitation technique enabled the production of particles smaller than 200 nm with a PDI lower than 0.2, and the study established the significant impact (p < 0.05) of the three variables related to the polymers and solvents. The selected PNPs contained 5 mg of Qr and 50 mg of Eudragit polymers (1:10 w/w Eudragit® EPO, E100, L100, and Eudragit L100-55) and diverse concentrations of PVA. The study found that including PVA in the AP increased the Qr encapsulation by up to 98%. The hemolytic potential of Eudragit® PNPs and Qr was assessed in human erythrocytes, with no significant cytotoxic activity observed (p < 0.001) compared with the control. In conclusion, via the nanoprecipitation technique, preparing PNPs with defined and homogeneous S to entrap the flavonol Qr efficiently is possible.

Paraffin waxes are a promising material for heat storage with high energy density. Their low thermal conductivity, which limits the speed of charging and discharging in heat buffers, was previously shown to be improved by adding graphene nanofillers. In the present study, using molecular dynamics simulations, the segregation by molecular weight of polydisperse paraffin near graphene flakes is investigated. In liquid bidisperse paraffin composed of decane and triacontane, an aligned layer containing mainly triacontane was observed next to the graphene. Upon slow cooling, the wax crystallised into distinct layers parallel to the graphene sheet, with much stronger segregation by molecular weight than in the crystallised bidisperse wax without graphene. For polydisperse wax, the segregation effect was much less pronounced. The molten paraffin had a somewhat higher concentration of the longest chains in the first layers next to the graphene, but during crystallisation, the molecular weight segregation was only slightly increased. Measurements of crystallinity using an alternative version of the method developed by Yamamoto showed that the layers of wax were highly aligned parallel to the graphene, both in the solid state with all wax crystallised and in the liquid state with one layer of aligned wax above and below the graphene. Thermal conductivity was increased in planes parallel to the graphene flakes. The strong segregation of chain lengths in the bidisperse wax resulted in clear differences in thermal conductivity in the segregated regions. The less segregated polydisperse wax showed less variation in thermal conductivity.

Polyelectrolyte complexes (PECs) as drug delivery systems are widely explored since they are easily obtained by coacervation and biopolymers can be associated. However, particle distribution is a challenging critical parameter that has been infrequently focused. This work evaluated the effect of NaCl concentration on the physicochemical properties of PECs based on chitosan and hypromellose loaded with methotrexate. The particle size, zeta potential and polydispersity index (PdI) were determined by DLS, besides of drug entrapment efficiency (EE) and in vitro drug release profile determination. Particle size decreased while NaCl concentration rised, achieving a narrower size distribution of (345±79 nm) and PdI (0.285±0.067) with 200 mmol/L NaCl. The higher the NaCl concentration, the lower the zeta potential at acid pH. The EE was kept similar ((28.2±4.5) %) from 0 to 300 mmol/L NaCl, while 400 mmol/L NaCl impaired the drug entrapment. The addition of (200 and 300) mmol/L NaCl did not affect the drug release profile, but it was faster with (100 or 400) mmol/L. In conclusion, the addition of 200 mmol/L NaCl reduced particle size and PdI with no changes in the EE and drug release. Therefore, the ionic strength plays an important role on PECs development.

The influence of molecular weight, polydispersity, and degree of branching of four potato starches (Paselli MD10, Eliane MD6, Eliane MD2, and highly branched starch) on the adsorption rates on activated carbon (Norit CA1) was investigated. Changes in starch concentration and size distribution over time were analysed by Total Starch Assay and Size Exclusion Chromatography. Average molecular weight and degree of branching of a starch scaled negatively with average adsorption rate. Within a size-distribution, adsorption rates scaled negatively with increasing molecule size, resulting in an increased average molecular weight in solution of between 25 % and 213 % and a decreased polydispersity of between 13 % and 38 %. Simulation with dummy distributions estimated the ratio of adsorption rates for 20th percentile and 80th percentile molecules within a distribution to range between a factor 4 and 8 for the different starches. Competitive adsorption decreased the adsorption rate of molecules above the average size within a sample distribution.

Novel vaccine platforms for delivery of nucleic acids based on viral and non-viral vectors, such as recombinant adeno associated viruses (rAAV) and lipid-based nanoparticles (LNPs), hold great promise. However, they pose significant manufacturing and analytical challenges due to their intrinsic structural complexity. During product development and process control, their design, characterization, and quality control require the combination of fit-for-purpose complementary analytical tools. Moreover, an in-depth methodological expertise and holistic approach to data analysis are required for robust measurements and to enable an adequate interpretation of experimental findings. Here the combination of complementary label-free biophysical techniques, including dynamic light scattering (DLS), multiangle-DLS (MADLS), Electrophoretic Light Scattering (ELS), nanoparticle tracking analysis (NTA), multiple detection SEC and differential scanning calorimetry (DSC), have been successfully used for the characterization of physical and chemical attributes of rAAV and LNPs encapsulating mRNA. Methods’ performance, applicability, dynamic range of detection and method optimization are discussed for the measurements of multiple critical physical−chemical quality attributes, including particle size distribution, aggregation propensity, polydispersity, particle concentration, particle structural properties and nucleic acid payload.

Nanoparticle aggregation has been found to be crucial for the thermal properties of nanofluids and their performance as heating or cooling agents. Most relevant studies in the literature consider particles of uniform size with point contact only. A number of forces and mechanisms are expected to lead to deviation from this ideal description. In fact, size uniformity is difficult to achieve in practice; also, overlapping of particles within aggregates may occur. In the present study, the effects of polydispersity and sintering on the effective thermal conductivity of particle aggregates are investigated. A simulation method has been developed that is capable of producing aggregates made up of polydispersed particles with tailored morphological properties. Modelling of the sintering process is implemented in a fashion that is dictated by mass conservation and the desired degree of overlapping. A noticeable decrease in the thermal conductivity is observed for elevated polydispersity levels compared to that of aggregates of monodisperse particles with the same morphological properties. Sintered nanoaggregates offer wider conduction paths through the coalescence of neighbouring particles. It was found that there exists a certain sintering degree of monomers that offers the largest improvement in heat performance.

Microalgae are described as a new source of a wide range of bioactive compounds with health-promoting properties, such as omega-3 lipids. This biomass product is gaining attention mainly due to its potential to accumulate different compounds depending on the species and environment, and it has been commonly recognized as a valuable nutraceutical alternative to fish and krill oils. In this work, we obtained the extract of the microalga Nannochloropsis gaditana, selected on the basis of its content of eicosapentaenoic acid (EPA) and glycolipids, which were determined using GC-MS and high-performance liquid chromatography (HPLC), respectively. To develop an oral formulation for the delivery of the extract, we used a 23 factorial design approach to obtain an optimal lipid nanoparticle formulation. The surfactant and solid lipid content were set as the independent variables, while the particle size, polydispersity index, and zeta potential were taken as the dependent variables of the design. To ensure the potential use of the optimum LN formulation to protect and modify the release of the loaded microalga extract, rheological and differential scanning calorimetry analyses were carried out. The developed formulations were found to be stable over 30 days, with an encapsulation efficiency over 60%., This work was funded by Scholarships Santander Research/Convocatòria d’estades 2022 per a doctorands de la UB granted to R. Galindo and by UAM/Santander program for the mobility of young researchers granted to C. Blanco.

Acoustic droplet vaporization is the ultrasound-mediated phase change of liquid droplets into gas microbubbles. Following the phase change, oxygen diffuses from the surrounding fluid into the microbubble. An in vitro model was used to study the effects of droplet diameter, the presence of an ultrasound contrast agent, ultrasound duty cycle, and droplet concentration on the magnitude of oxygen scavenging in oxygenated deionized water. Perfluoropentane droplets were manufactured through a microfluidic approach at nominal diameters of 1, 3, 5, 7, 9, and 12 µm and studied at concentrations varying from 5.1 × 10−5 to 6.3 × 10−3 mL/mL. Droplets were exposed to an ultrasound transduced by an EkoSonicTM catheter (2.35 MHz, 47 W, and duty cycles of 1.70%, 2.34%, or 3.79%). Oxygen scavenging and the total volume of perfluoropentane that phase-transitioned increased with droplet concentration. The ADV transition efficiency decreased with increasing droplet concentration. The increasing duty cycle resulted in statistically significant increases in oxygen scavenging for 1, 3, 5, and 7 µm droplets, although the increase was smaller than when the droplet diameter or concentration were increased. Under the ultrasound conditions tested, droplet diameter and concentration had the greatest impact on the amount of ADV and subsequent oxygen scavenging occurred, which should be considered when using ADV-mediated oxygen scavenging in therapeutic ultrasounds.

Paraffin waxes are promising phase change materials, abundantly available at very low cost. Having large latent heat, these materials can be used for thermal energy storage. However, when used in heat batteries, paraffin's low thermal conductivity prevents fast charging and discharging. This calls for the design of tailored hybrid materials with improved properties, the present study concentrates on properties of pure paraffin wax. Using fully atomistic molecular-dynamics (MD) simulations, we study the effects of polydispersity and branching on the thermal conductivity of paraffin waxes, in molten (450 K) and solid (250 K) state. Both branching and polydispersity affect the density and especially the crystallinity of the solid. Branching has a pronounced effect on crystallisation caused by inhibited alignment of the polymer backbones while the effect of polydispersity is less pronounced. The thermal conductivity (TC) has been simulated using the reverse non-equilibrium molecular-dynamics method, as well as the equilibrium Green-Kubo approach. Increased branching, added to backbones comprised of twenty monomers, results in decreasing TC of up to 30%, polydispersity only has an effect in the semi-crystalline state. Comparison to available experiments shows good agreement which validates the model details, applied force field and the calculation methods. We show that at comparable computational costs, the reverse non-equilibrium MD approach produces more reliable results for TC, as compared to the equilibrium Green-Kubo method. The major contribution to TC by acoustic phonon transport along the backbone was shown by analysing extreme cases. The phonon density of states (PDOS) of samples with high branching or with small chain length displayed diminished peaks in the acoustic range as compared to the PDOS of samples with low branching or larger chain length, respectively. The suggested MD approach can definitely be used to investigate specific material modifications aimed at increasing the overall TC.

The ability to separate enzymes, or cells or viruses, from a mixture is important and can be realized by the incorporation of the mixture into a macromolecular solution. This incorporation may lead to a spontaneous phase separation, with one phase containing the majority of one of the species of interest. Inspired by this phenomenon, we studied the theoretical phase behavior of a model system composed of an asymmetric binary mixture of hard spheres, of which the smaller component was monodisperse and the larger component was polydisperse. The interactions were modeled in terms of the second virial coefficient and could be additive hard sphere (HS) or nonadditive hard sphere (NAHS) interactions. The polydisperse component was subdivided into two subcomponents and had an average size ten or three times the size of the monodisperse component. We gave the set of equations that defined the phase diagram for mixtures with more than two components in a solvent. We calculated the theoretical liquid–liquid phase separation boundary for the two-phase separation (the binodal) and three-phase separation, the plait point, and the spinodal. We varied the distribution of the polydisperse component in skewness and polydispersity, and we varied the nonadditivity between the subcomponents as well as between the main components. We compared the phase behavior of the polydisperse mixtures with binary monodisperse mixtures for the same average size and binary monodisperse mixtures for the same effective interaction. We found that when the compatibility between the polydisperse subcomponents decreased, the three-phase separation became possible. The shape and position of the phase boundary was dependent on the nonadditivity between the subcomponents as well as their size distribution. We conclude that it is the phase enriched in the polydisperse component that demixes into an additional phase when the incompatibility between the subcomponents increases.

Currently, phenol-formaldehyde oligomers cross-composite with various thermoplastic oligomers and monomers are well used in many fields, including: as binders in obtaining composite materials, as coating formers, in the production of plastic products and in other fields. is bearing fruit. In this case, the best way to confirm that the obtained oligomers are sooligomers is to study them by nephelometric titration., "Science and innovation" international scientific journal. ISSN: 2181-3337

We introduce a model for a fluid of polydisperse rounded hard rectangles where the length and width of the rectangular core are fixed, while the roundness is taken into account by the convex envelope of a disk displaced along the perimeter of the core. The diameter of the disk has a continuous polydispersity described by a Schultz distribution function. We implemented the scaled particle theory for this model with the aim to studying: (i) the effect of roundness on the phase behavior of the one-component hard-rectangle fluid, and (ii) how polydispersity affects phase transitions between isotropic, nematic and tetratic phases. We found that roundness greatly affects the tetratic phase, whose region of stability in the phase diagram strongly decreases as the roundness parameter is increased. Also the interval of aspect ratios where the tetratic-nematic and isotropic-nematic phase transitions are of first order considerably reduces with roundness, both transitions becoming weaker. Polydispersity induces strong fractionation between the coexisting phases, with the nematic phase enriched in particles of lower roundness. Finally, for high enough polydispersity and certain mean aspect ratios, the isotropic-to-nematic transition can change from second (for the one-component fluid) to first order. We also found a packing-fraction inversion phenomenon for large polydispersities: the coexisting isotropic phase has a higher packing fraction than the nematic., Comment: 16 pages, 13 figures

Nutraceuticals have gained increasing attention over the last years due to their potential value as therapeutic compounds formulated from natural sources. For instance, there is a wide range of literature about the cardioprotective properties of omega-3 lipids and the antioxidant value of some phenolic compounds, which are related to antitumoral activity. However, the value of nutraceuticals can be limited by their instability under gastric pH and intestinal fluids, their low solubility and absorption. That is why encapsulation is a crucial step in nutraceutical design. In fact, pharmaceutical nanotechnology improves nutraceutical stability and bioavailability through the design and production of efficient nanoparticles (NPs). Lipid nanoparticles protect the bioactive compounds from light and external damage, including the gastric and intestinal conditions, providing a retarded delivery in the target area and guaranteeing the expected therapeutic effect of the nutraceutical. This review will focus on the key aspects of the encapsulation of bioactive compounds into lipid nanoparticles, exploring the pharmaceutical production methods available for the synthesis of NPs containing nutraceuticals. Moreover, the most common nutraceuticals will be discussed, considering the bioactive compounds, their natural source and the described biological properties, This work received the funding support from Santander/Autonoma University of Madrid, granted to the first author

We probe the influence of particle size polydispersity on field-induced structures and structural transitions in magnetic fluids (ferrofluids) using phase contrast optical microscopy, light scattering and Brownian dynamics simulations. Three different ferrofluids containing superparamagnetic nanoparticles of different polydispersity indices (PDIs) are used. In a ferrofluid with a high PDI (∼0.79), thin chains, thick chains, and sheets are formed on increasing the in-plane magnetic field, whereas isotropic bubbles, and hexagonal and lamellar/stripe structures are formed on increasing the out-of-plane magnetic field over the same range. In contrast, no field-induced aggregates are seen in the sample with low polydispersity under the above conditions. In a polydisperse sample, bubbles are formed at a very low magnetic field strength of 30 G. Insights into the structural evolution with increasing magnetic field strength are obtained by carrying out Brownian dynamics simulations. The crossovers from isotropic, through hexagonal columnar, to lamellar/stripe structures observed with increasing field strength in the high-polydispersity sample indicate the prominent roles of large, more strongly interacting particles in structural transitions in ferrofluids. Based on the observed microstructures, a phase diagram is constructed. Our work opens up new opportunities to develop optical devices and access diverse structures by tuning size polydispersity. © The Royal Society of Chemistry 2021.

Humic substances are polydisperse mixtures of structurally complex matters with different molecular weights. The complexity of molecular composition of humic substances is reflected through their physical and chemical properties and results in diverse interactions both with inorganic components and living organisms. The correlation of the molecular composition of humic and fulvic acids and their molecular weight distribution were analyzed by means of CP/MAS 13C NMR spectroscopy and size exclusion chromatography. Humic acids are a dynamic system containing macromolecular, oligomeric and low-molecular components. Fulvic acids are a monodisperse mixture of relatively low-molecular (up to 2 kDa) organic compounds. A significant correlation between the content of high and medium weight molecular fractions with labile fragments and low molecular weight fractions with hydrophobous fragments of humic acids has been revealed.

Indexación Scopus Anesthetic failure is common in dental inflammation processes, even when modern agents, such as articaine, are used. Nanostructured lipid carriers (NLC) are systems with the potential to improve anesthetic efficacy, in which active excipients can provide desirable properties, such as anti-inflammatory. Coupling factorial design (FD) for in vitro formulation development with in vivo zebrafish tests, six different NLC formulations, composed of synthetic (cetyl palmitate/triglycerides) or natural (avocado butter/olive oil/copaiba oil) lipids were evaluated for loading articaine. The formulations selected by FD were physicochemically characterized, tested for shelf stability and in vitro release kinetics and had their in vivo effect (anti-inflammatory and anesthetic effect) screened in zebrafish. The optimized NLC formulation composed of avocado butter, copaiba oil, Tween 80 and 2% articaine showed adequate physicochemical properties (size = 217.7 ± 0.8 nm, PDI = 0.174 ± 0.004, zeta potential = − 40.2 ± 1.1 mV, %EE = 70.6 ± 1.8) and exhibited anti-inflammatory activity. The anesthetic effect on touch reaction and heart rate of zebrafish was improved to 100 and 60%, respectively, in comparison to free articaine. The combined FD/zebrafish approach was very effective to reveal the best articaine-in-NLC formulation, aiming the control of pain at inflamed tissues. © 2020, The Author(s). https://www-nature-com.recursosbiblioteca.unab.cl/articles/s41598-020-76751-6

International audience; In this article Part II, we consider the application of ienaic modeling for solvent extraction of rare earths in the case of the mixed DMDOHEMA/HDEHP extractant system. The system exhibits a synergistic extraction effect depending on the acid concentration and the extractant mole fraction, as demonstrated in the experimental article Part I. In this work, we directly compare experimental findings with theoretical predictions of the droplet model. The model considers the effective free energy of transfer as a combination of competing molecular forces, but contrary to previous micelle models that focus only on the dominant stoichiometry, it allows calculations of free energies of every possible spherical aggregate. The resulting image of the extraction process is that different behaviors can be obtained depending on the acidity and mole fraction of extractants, which are associated with different aggregation regimes in a complex free energy landscape of the system. Nevertheless, self-assembly is tuned by the extraction of all solutes, and not only the target metal cations.

Adsorption of natural organic matter (NOM) to mineral surfaces is an important process determining the environmental fate and biogeochemical cycling of many elements. Natural organic matter consists of a heterogeneous mixture of soft and flexible organic molecules. Upon adsorption, size fractionation may occur, as well as changes in molecular conformation. Although very important, these phenomena have been omitted in existing adsorption models. Filling this gap, a novel framework for NOM adsorption to metal (hydr)oxides is presented. Humic acid (HA) was used as an analog for studying experimentally the NOM adsorption to goethite and its size fractionation as a function of pH, ionic strength, and surface loading. Size fractionation was evaluated for adsorption isotherms collected at pH 4 and 6, showing HA molecules of low molar mass were preferentially adsorbed. This phenomenon was incorporated into the new model. Consistent description of the HA adsorption data over the entire range of pH (3–11), ionic strength (2–100 mM), and surface loading (0.1–3 mg m−2) indicated that the spatial distribution of HA molecules adsorbed in the interface is a trade-off between maximizing the interaction of the HA ligands with the oxide surface and minimizing the electrostatic repulsion between HA particles as a result of interfacial crowding. Our advanced consistent framework is able to quantify changes in molar mass and molecular conformation, thereby significantly contributing to an improved understanding of the competitive power of HA for interacting on oxides with other adsorbed small organic acids as well as environmentally important oxyanions, such as phosphate, arsenate, and others.

Size and zeta potential are critical physicochemical properties of nanoparticles (NPs), influencing their biological activity and safety profile. These are essential for further industrial upscale and clinical success. However, the characterization of polydisperse, non-spherical NPs is a challenge for traditional characterization techniques (ex., dynamic light scattering (DLS)). In this paper, superparamagnetic iron oxide nanoparticles (SPIONs) were coated with polyvinyl alcohol (PVAL) exhibiting different terminal groups at their surface, either hydroxyl (OH), carboxyl (COOH) or amino (NH2) end groups. Size, zeta potential and concentration were characterized by orthogonal methods, namely, batch DLS, nanoparticle tracking analysis (NTA), tunable resistive pulse sensing (TRPS), transmission electron microscopy (TEM), asymmetric flow field flow fractionation (AF4) coupled to multi-angle light scattering (MALS), UV–Visible and online DLS. Finally, coated SPIONs were incubated with albumin, and size changes were monitored by AF4-MALS-UV-DLS. NTA showed the biggest mean sizes, even though DLS PVAL-COOH SPION graphs presented aggregates in the micrometer range. TRPS detected more NPs in suspension than NTA. Finally, AF4-MALS-UV-DLS could successfully resolve the different sizes of the coated SPION suspensions. The results highlight the importance of combining techniques with different principles for NPs characterization. The advantages and limitations of each method are discussed here.

This study analyses the impact of particle polydispersity using the Eulerian-Eulerian (EE) and Lagrangian-Eulerian (LE) modelling approaches in the context of wellbore cleaning operations in the drilling industry. Spherical particles of sizes 0.5 mm, 0.75 mm and 1 mm are considered, whereas a Power Law rheological model is used for the fluid phase description. The EE approach implemented herein applies the Kinetic Theory of Granular Flow (KTGF) in ANSYS Fluent® and accounts for the particle size differences by representing them as different phases within the computational domain. With the LE approach, we employ the Dense Discrete Phase Model (DDPM) and capture this difference with the aid of a size distribution model (the Rosin-Rammler model). The findings of our computational experiments show considerable differences in key variables (the pressure drop, and particle deposition tendencies) between monodispersed and polydispersed transport scenarios.

The equilibrium concentration distribution of magnetic nanoparticles in a nonuniform magnetic field is studied theoretically. A linear current-carrying wire is used as a source of a nonuniform field. An exact solution for the concentration profile of a dilute monodisperse suspension is obtained within the framework of the continuous mass transfer theory. The applicability of this solution in a broad range of amperage values is tested using Langevin dynamics simulations. Obtained solution is also generalized for polydisperse suspensions. It is demonstrated that the particle size distribution in a polydisperse system strongly depends on the distance from the wire and in general does not coincide with the original distribution of a uniform suspension.

International audience; The dynamics of two model glass-formers (3D oligomer melt and 2D polydisperse colloidal system) are analyzed using MD simulations. It is found that the standard deviation of the shear modulus shows a striking peak near the glass transition T g , which is explained with a quantitative theory. The simulation data well below T g suggest that static multi-point correlations of local stress are long-range. The obtained correlation functions of time-dependent and wavevector-resolved stress for the 2D system are in excellent agreement with the developed theory indicating that the frozen-in stress inhomogeneities in the glassy state are correlated according to a power law.

Determination of particle size is one of the major needs in the industry and biotechnology. Dynamic light scattering (DLS) is a widely used technique for determining size distribution of spherical particle in nanometer and submicron size range. In this method, there are different algorithms for determining the size and size distribution of particles, which are selected according to the required accuracy as well as the sample. In this paper, a review of the theory of DLS and commonly used algorithms to determine particle size, have been carried out. The accuracy and performance range of the two common Cumulant analysis and Contin algorithm have been experimentally investigated, by using the wide range of sizes (20-900 nanometer) of standard spherical polystyrene particles. It is shown that both algorithms results are quite consistent with the manufacturer’s values for diameter of particles. Since most of the samples in the more common situation are not uniform particles with a narrow size distribution, mixtures of two standard particles of different sizes were studied by both algorithms to test the performance of DLS in non-standard samples. Method of Cumulant reports one size that is not consistent with the size of any particles in the sample. However, the polidispersity index (PDI) indicates that the sample size distribution is very wide. Method of Contin reports only one size that is not also consistent with the size of any particles, but, it is closer to the larger one. The results of both algorithms indicate that the DLS fails to determine size distribution in the mixed samples.

We present here a perspective detailing the current state-of-the-art technologies for the characterisation of nanoparticles (NPs) in liquid suspension. We detail the technologies involved and assess their applications in the determination of NP size and concentration. We also investigate the parameters that can influence the results and put forward a cause and effect analysis of the principle factors influencing the measurement of NP size and concentration by NP tracking analysis and dynamic light scattering, to identify areas where uncertainties in the measurement can arise. Also included are technologies capable of characterising NPs in solution, whose measurements are not based on light scattering. It is hoped that the manuscript, with its detailed description of the methodologies involved, will assist scientists in selecting the appropriate technology for characterising their materials and enabling them to comply with regulatory agencies’ demands for accurate and reliable NP size and concentration data., Graphical Abstract

Phosphate ore slurry is a suspension of insoluble particles of phosphate rock, the primary raw material for fertilizer and phosphoric acid, in a continuous phase of water. This suspension has a non-Newtonian flow behavior and exhibits yield stress as the shear rate tends toward zero. The suspended particles in the present study were assumed to be noncolloidal. Various grades and phosphate ore concentrations were chosen for this rheological investigation. We created some experimental protocols to determine the main characteristics of these complex fluids and established relevant rheological models with a view to simulate the numerical flow in a cylindrical pipeline. Rheograms of these slurries were obtained using a rotational rheometer and were accurately modeled with commonly used yield-pseudoplastic models. The results show that the concentration of solids in a solid–liquid mixture could be increased while maintaining a desired apparent viscosity. Finally, the design equations for the laminar pipe flow of yield pseudoplastics were investigated to highlight the role of rheological studies in this context.

Although in academic and industrial practice polymers are typically described by their average molecular parameters, most often they display a polydispersity both in size and in properties. In this paper, we focus on the influence of polydispersity on the adsorption of polycarboxylate ester on cement grains and on its influence on the definition of a so-called affinity of the polymer to the surface. We first show that a constant fraction of a polydisperse polycarboxylate ester always adsorbs no matter the availability of adsorption sites. We moreover suggest from our measurements and from scaling laws from literature that the degree of polydispersity in the structure of polycarboxylate ester should affect adsorption at both low and intermediate dosages and hydrodynamic radii in solution. However, it shall not have a major influence on polymer layer thickness or saturation dosage. ISSN:0008-8846

Magnetic inductive heating (MIH) has been a topic of great interest because of its potential applications, especially in biomedicine. In this paper, the parameters characteristic for magnetic inductive heating power including maximum specific loss power (SLPmax), optimal nanoparticle diameter (Dc) and its width (ΔDc) are considered as being dependent on magnetic nanoparticle anisotropy (K). The calculated results suggest 3 different Néel-domination (N), overlapped Néel/Brownian (NB), and Brownian-domination (B) regions. The transition from NB- to B-region changes abruptly around critical anisotropy Kc. For magnetic nanoparticles with low K (K &lt, Kc), the feature of SLP peaks is determined by a high value of Dc and small ΔDc while those of the high K (K &gt, Kc) are opposite. The decreases of the SLPmax when increasing polydispersity and viscosity are characterized by different rates of d(SLPmax)/dσ and d(SLPmax)/dη depending on each domination region. The critical anisotropy Kc varies with the frequency of an alternating magnetic field. A possibility to improve heating power via increasing anisotropy is analyzed and deduced for Fe3O4 magnetic nanoparticles. For MIH application, the monodispersity requirement for magnetic nanoparticles in the B-region is less stringent, while materials in the N- and/or NB-regions are much more favorable in high viscous media. Experimental results on viscosity dependence of SLP for CoFe2O4 and MnFe2O4 ferrofluids are in good agreement with the calculations. These results indicated that magnetic nanoparticles in the N- and/or NB-regions are in general better for application in elevated viscosity media.

The ability to separate enzymes, nucleic acids, cells, and viruses is an important asset in life sciences. This can be realised by using their spontaneous asymmetric partitioning over two macromolecular aqueous phases in equilibrium with one another. Such phases can already form while mixing two different types of macromolecules in water. We investigate the effect of polydispersity of the macromolecules on the two-phase formation. We study theoretically the phase behavior of a model polydisperse system: an asymmetric binary mixture of hard spheres, of which the smaller component is monodisperse and the larger component is polydisperse. The interactions are modelled in terms of the second virial coefficient and are assumed to be additive hard sphere interactions. The polydisperse component is subdivided into sub-components and has an average size ten times the size of the monodisperse component. We calculate the theoretical liquid–liquid phase separation boundary (the binodal), the critical point, and the spinodal. We vary the distribution of the polydisperse component in terms of skewness, modality, polydispersity, and number of sub-components. We compare the phase behavior of the polydisperse mixtures with their concomittant monodisperse mixtures. We find that the largest species in the larger (polydisperse) component causes the largest shift in the position of the phase boundary, critical point, and spinodal compared to the binary monodisperse binary mixtures. The polydisperse component also shows fractionation. The smaller species of the polydisperse component favor the phase enriched in the smaller component. This phase also has a higher-volume fraction compared to the monodisperse mixture.

This study presents experimental measurements and computational modelling of particle-laden jets for a wide range of Stokes numbers to analyse the effect of polydispersity on particle volume fraction and velocity. The polydisperse two-phase turbulent jet issues from a pipe into a low velocity coflow, resulting in inlet Stokes numbers, St in , ranging from 0.003 to 25. The particle velocity and volume fraction are experimentally measured using digital particle image velocimetry and planar nephelometry simultaneously. The simulations are conducted using a newly developed model based on the probability density function of the population balance equation (PDF-PBE) in a large eddy simulation framework. A stochastic Monte Carlo method is adopted to solve the PDF-PBE on an ensemble of notional Lagrangian particles, while the method of Stokes binning is employed to explicitly treat inertial effects in a computationally efficient way. There is a satisfactory agreement between the measurements and simulations. A series of monodisperse simulations were also conducted to compare with the polydisperse flows in a two-way coupled flow. The results confirm that in the monodisperse jet, small particles (with St in ≤ 0.3 ) closely follow the carrier phase velocity whereas in the polydisperse jet they are affected by the presence of larger particles to reduce their axial velocity decay rate. The opposite trend is observed for large particles ( St in ≥ 5.5 ), confirming that in the polydisperse jet, the presence of small particles increases the large particles’ radial dispersion that lowers their volume fraction along the centreline compared to the monodisperse jet.

The equilibrium concentration distribution of magnetic nanoparticles in a nonuniform magnetic field is studied theoretically. A linear current-carrying wire is used as a source of a nonuniform field. An exact solution for the concentration profile of a dilute monodisperse suspension is obtained within the framework of the continuous mass transfer theory. The applicability of this solution in a broad range of amperage values is tested using Langevin dynamics simulations. Obtained solution is also generalized for polydisperse suspensions. It is demonstrated that the particle size distribution in a polydisperse system strongly depends on the distance from the wire and in general does not coincide with the original distribution of a uniform suspension. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Funding: This research was funded by Russian Foundation for Basic Research grant number 19-31-60036.

Producción Científica, Hemicelluloses and pectins are good candidates as biopolymers for the formation of products such as packaging films. Purified freeze-dried fractions of hemicelluloses and pectins, of different molecular weights, were obtained by treating hydrothermal extracts (140, 160, and 180 °C) of discarded carrots with ultrafiltration membranes (30, 10, 5, and 1 kDa). After each ultrafiltration, several cycles of diafiltration with partial water reuse were applied, obtaining a better separation and purification. A cascade configuration (30-10-5-1 kDa) was used in the 140 and 160 °C extracts, and a mixed configuration (5-10-1 kDa) in the 180 °C extract. High molecular weight hemicelluloses increased in concentration by a factor of 5 in the cascade configuration and by a factor of 16.67 in the mixed configuration. A high removal of free sugars (98.9–99.5 wt%) and by-products (94.4–99.2 wt%) through 1 kDa permeate and diafiltration waters was obtained. The system allowed moving from feeds with molecular weight, polydispersity, and purity in the ranges 9.02–18.83 kDa, 16.2–31.6, and 30.12–33.51 wt% to fractions with values in the ranges 2.59–102.75 kDa, 1.2–4.0, and 73.1–100 wt%., Junta de Castilla y León - Fondo Europeo de Desarrollo Regional (project CLU-2019-04), Ministerio de Ciencia, Innovación y Universidades - Fondo Europeo de Desarrollo Regional (project PID2019-105975GB-I00), Ministerio de Educación, Cultura y Deporte (contract FPU15/06366)

Deep Eutectic Solvents (DESs) are emerging as a promising medium for many chemical processes. They can be used to observe specific properties required for nanomaterials' applications. Controlled CO2 adsorption requires disaggregation of carbon nanotubes into smaller bundles which can be accomplished by dispersing them in aqueous DES system. In this study, response surface methodology (RSM) was adopted to examine the impacts of three important factors on the dispersion of single walled carbon nanotubes (SWNTs) in Choline Chloride-Glycerol (ChCl-Gly) DES; (i) ChCl-Gly (mass% in water), (ii) sonication energy input (J/mL), and (iii) SWNTs' concentration (mg/L). The net negative surface charge of ChCl-Gly, a “green solvent,” provided superior dispersion of inherently negatively charged SWNTs in water via electrostatic repulsion. The impacts of the dispersion factors were quantified by the average aggregate diameter (nm) and polydispersity (polydispersity index, PDI) of SWNTs in aqueous-DES systems. Models were developed, experimentally verified, and statistically validated to map the impacts of these factors and to obtain optimized dispersions. The optimized dispersions, characterized by the small (

In this paper, we study the vaporization process of a polydisperse ensemble of liquid drops on the basis of a nonlinear set of balance and kinetics equations for the particle-radius distribution function and temperature in the gaseous phase. We found an exact parametric solution to this problem using a modified time variable and the Laplace integral transform method. The distribution function of vaporizing drops as well as its moments, the temperature dynamics in gas, and the unvaporized mass of drops are found. The initial particle-radius distribution shifts to smaller particle radii with increasing the vaporization time. As this takes place, the temperature difference between the drops and gas decreases with time. It is shown that the heat of vaporization and initial total number of particles in the system substantially influence the dynamics of a polydisperse ensemble of liquid drops. © 2020 John Wiley & Sons, Ltd. This work was supported by the Russian Foundation for Basic Research (project no. 20‐08‐00199).

The ability of cells to respond to stress is central to health. Stress can damage folded proteins, which are vulnerable to even minor changes in cellular conditions. To maintain proteostasis, cells have developed an intricate network in which molecular chaperones are key players. The small heat-shock proteins (sHSPs) are a widespread family of molecular chaperones, and some sHSPs are prominent in muscle, where cells and proteins must withstand high levels of applied force. sHSPs have long been thought to act as general interceptors of protein aggregation. However, evidence is accumulating that points to a more specific role for sHSPs in protecting proteins from mechanical stress. Here, we briefly introduce the sHSPs and outline the evidence for their role in responses to mechanical stress. We suggest that sHSPs interact with mechanosensitive proteins to regulate physiological extension and contraction cycles. It is likely that further study of these interactions – enabled by the development of experimental methodologies that allow protein contacts to be studied under the application of mechanical force – will expand our understanding of the activity and functions of sHSPs, and of the roles played by chaperones in general.

In chapter 2 we presented results obtained through experiments on a vibrated monolayer of granular metallic rods, focusing on the effects that introducing a circular obstacle to the centre of the cavity (thus creating an annulus) would have on the steady states of the system. Although topological arguments suggested that defects found on systems with no obstacle would not appear, we observed a separation of the system into regions consisting of smectic and tetratic ordering, the latter containing completely unordered point-like defects. We argue that the topological approach based on a continuum argument is rendered invalid by the size of the elements involved, in particular the ratio of the central obstacle size to particle lengths. The tetratic structures can be viewed as domain walls separating the smectic regions, which were invariably equal to four in our experiments. In chapter 3 we used the SPT to study two different systems of two-dimensional particles. In the first one, composed of particles shaped like hard isosceles triangles, we found, for the one component fluid, 1st and 2nd order Isotropic-Nematic transitions and for symmetric binary mixtures a 1st order Nematic-Nematic transition ending in a critical point and a Landau point where two first-order Nematic-Triatic transitions and a Nematic-Nematic demixing transition coalesce. We also found that for these particular mixtures a Triatic phase can be stabilized even though both species involved do no exhibit a stable Triatic phase on the one-component limit. To the best of our knowledge this is the first example of a Nematic-Nematic transition on one-component hard particle systems. For the second system, of hard rectangular particles, we found that polydispersity has an important effect on the phase diagram, strengthening the 1st order Isotropic-Nematic transition and decreasing the stability of the Tetratic phase. Also we found that polydispersity induces strong fractionation between the coexisting phases. Finally in chapter 4 we studied the effects of nano-confinement on a system of hardboard like particles. Following the restricted orientation (Zwanzig) approach we obtained a DF using the FMT to approximate the excess part of the free-energy of the system by means of numerical minimization. We considered a particular set of particle aspect ratios as well as slightly biaxial particles. We hoped to determine whether homeotropic configurations could be stabilized by the presence of two hard walls. We obtained that, for particular particle aspect ratios, homeotropic phases do stabilize and also that allowing for particle biaxiality greatly enriches the phase diagram. The results obtained can be explained by considering how entropy is maximized as the system approaches close packing. Programa de Doctorado en Ingeniería Matemática por la Universidad Carlos III de Madrid Presidente: Luis Mederos Martín.- Secretario: Daniel de las Heras Díaz-Plaza.- Vocal: Giorgo Cinacchi

The copolymerization of styrene (St) with a bioderived monomer, pentadecylphenyl methacrylate (PDPMA), via atom transfer radical polymerization (ATRP) was studied in this work. The copolymerization reactivity ratio was calculated using the composition data obtained from 1H NMR spectroscopy, applying Kelen-Tudos and Finemann-Ross methods. The reactivity ratio of styrene (r1 = 0.93) and PDPMA (r2 = 0.05) suggested random copolymerization of the two monomers with alternation. The copolymerization conversion increased with increasing PDPMA concentration of the feed, upto 70 wt % PDPMA, but decreased thereafter. The molecular weight determined by gel permeation chromatography was lower than the theoretical values and the polydispersity increased from 1.32 to 2.19, with increasing PDPMA content in the feed. The influence of styrene content on the glass transition and thermal decomposition behavior of the copolymers was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis, respectively. Morphological characterization by transmission electron microscopy (TEM) revealed a phase separated soft core-hard shell type structure. The complex viscosity and adhesion properties like peel strength and lap shear strength of the copolymer on different substrates increased with increasing styrene content.

Even in absence of cross-linking, at large enough concentration, long polymer strands have a strong influence on the rheology of aqueous systems. In this work, we show that solutions of medium molecular weight (120,000 – 190,000 g/mol) alginate polymer retained a liquid-like behaviour even for concentrations as large as 20 % w/v. On the contrary, solutions of alginate polymer of larger (and also polydisperse) molecular weight (up to 600,000 g/mol) presented a gel-like behaviour already at concentrations of 7 % w/v. We dispersed micron-sized iron particles at a concentration of 5 % v/v in these solutions, which resulted either in stable magnetic fluids or gels, depending on the type of alginate polymer employed (medium or large molecular weight, respectively). These magneto-polymer composites presented a shear-thinning behaviour that allowed injection through a syringe and recovery of the original properties afterwards. More interestingly, application of a magnetic field resulted in the formation of particle clusters elongated along the field direction. The presence of these clusters intensely affected the rheology of the systems, allowing a reversible control of their stiffness. We finally developed theoretical modelling for the prediction of the magnetic-sensitive rheological properties of these magneto-polymer colloids., Ministerio de Economía, Industria y Competitividad, MINECO, and Agencia Estatal de Investigación, AEI, Spain, cofounded by Fondo Europeo de Desarrollo Regional, FEDER, European Union, project FIS2017-85954-R. Ministry of Education and Science of the Russian Federation, projects 02.A03.21.0006; 3.1438.2017/4.6; 3.5214.2017/6.7 as well as to the Russian Fund of Basic Researches, project 19-52-12028

Risk mitigation in production facilities has been an issue of great interest for decades, especially in activities which represent a serious hazard to human health, environment and industrial plants. Dust explosions are a major hazard in many industrial processes: only in the first part of 2019 (January–June) 34 dust explosions, mainly due to organic powders, occurred worldwide. An explosion may take place whenever there is the presence of combustible dusts, which are frequently generated by activities such as grinding, crushing, conveying and storage. Currently, a relatively expensive experimental test, carried out into a 20-L Siwek apparatus, is used to address the order of magnitude (class) of explosive dust: this piece of information is referred to as the deflagration index, Kst. At the current state, only a few pioneering models have been developed in order to predict the value of the Kst as a function of some relevant properties of the dust: e.g. particle size distribution (PSD), humidity, thermal conductivity, etc‥ Most of these models condense the information about the PSD of a given dust into an average value, referred to as D50. In this work, a kinetic free mathematical model aimed at predicting the deflagration index for organic dusts is presented. This model, unlike the older ones, considers the whole particle size distribution for the computation of the deflagration index. In order to be implemented, only a single experimental Kst value (which works as a reference) and a particle size analysis on the dust are required. The model was validated using the whole granulometric distribution of three different organic powders (fosfomycin, sugar and niacin). In addition, the same estimations were done by considering only the D50 data. It was noticed that, for highly polydispersed dusts, results were less accurate with respect to those obtained using the complete PSD, highlighting the importance of considering a complete granulometric distribution for process safety purposes.

Heterogeneity in small heat shock proteins (sHsps) spans multiple spatiotemporal regimes—from fast fluctuations of part of the protein, to conformational variability of tertiary structure, plasticity of the interfaces, and polydispersity of the inter-converting, and co-assembling oligomers. This heterogeneity and dynamic nature of sHsps has significantly hindered their structural characterization. Atomic coordinates are particularly lacking for vertebrate sHsps, where most available structures are of extensively truncated homomers. sHsps play important roles in maintaining protein levels in the cell and therefore in organismal health and disease. HspB2 and HspB3 are vertebrate sHsps that are found co-assembled in neuromuscular cells, and variants thereof are associated with disease. Here, we present the structure of human HspB2/B3, which crystallized as a hetero-tetramer in a 3:1 ratio. In the HspB2/B3 tetramer, the four α-crystallin domains (ACDs) assemble into a flattened tetrahedron which is pierced by two non-intersecting approximate dyads. Assembly is mediated by flexible “nuts and bolts” involving IXI/V motifs from terminal regions filling ACD pockets. Parts of the N-terminal region bind in an unfolded conformation into the anti-parallel shared ACD dimer grooves. Tracts of the terminal regions are not resolved, most likely due to their disorder in the crystal lattice. This first structure of a full-length human sHsp heteromer reveals the heterogeneous interactions of the terminal regions and suggests a plasticity that is important for the cytoprotective functions of sHsps., Graphical abstract Unlabelled Image, Highlights • Dynamic behavior of heteromeric sHsps hinders structural biology of cytoprotection. • Full-length human HspB2/B3 in 3:1 ratio was crystallized and solved at 3.9-Å resolution. • Assembly is by flexible “nuts and bolts” from terminal regions filling domain pockets. • N-terminal regions bind in an unfolded conformation into shared dimer grooves. • IXI/V motifs from unstructured proteins may be sequestered by sHsps during disease.

International audience; This paper reports a study of thermal oxidation induced embrittlement in several polyethylene grades differing mainly by the broadness of the molar mass distribution (ranging for lower than 3 to more than 30). Thermal oxidation was monitored at macromolecular scale (Gel Permeation Chromatography, Differential Scanning Calorimetry) and macroscopic scale (tensile tests). As expected, the samples undergo predominant chain scission and plastic deformation is suppressed below a critical molar mass value (M’C). Even though this latter was previously reported to be independent of the initial weight average molar mass, it is shown here that it depends on initial polydispersity index. Samples were also shown to undergo chemicrystallization, i.e. that segments released by chain scissions migrate into the crystalline phase with a yield increasing with initial polydispersity index. Finally, the main novelty of this work is to evidence that the previously proposed end-of-life criteria at macromolecular level linked to loss of ductility (critical molar mass, crystallization yield) depend on the initial polydispersity index.

In this paper, an analytical solution to the model of the evolution of ellipsoidal crystals with fluctuating growth rates at the intermediate step of bulk phase transition is presented. A complete system of integrodifferential equations describing the problem was derived and analytically solved using the Laplace integral method. The kinetics of supercooling removal in melts has been found. The particle-volume distribution function represents a pike-shaped curve decreasing its maximum with time. It is demonstrated the differences in the distribution function for ellipsoidal and spherical crystals. © 2021 Institute of Physics Publishing. All rights reserved. This work was supported by the Russian Science Foundation (grant no. 18-19-00008).

Using computer simulations and a mean-field theoretical approach, we study how the growth in dipolar interparticle correlations manifests itself in the frequency-dependent initial magnetic susceptibility of a ferrofluid. Our recently developed theory gives the correct single-particle Debye-theory results in the low-concentration, non-interacting regime; and it yields the exact leading-order contributions from interparticle correlations. The susceptibility spectra are analysed in terms of the low-frequency behaviours of the real and imaginary parts, and the position of the peak in the imaginary part. By comparing the theoretical predictions to the results from Brownian dynamics simulations, it is possible to identify the conditions where correlations are important, but where self-assembly has not developed. We also provide a qualitative explanation for the behaviour of spectra beyond the mean-field limit. © 2016 Elsevier B.V.

Particle positions for the Isotropic compression of frictionless polydisperse systems, as a function of the size ratio and the shape of grain size distribution

We study the propagation of acoustic waves in a porous medium obeying the Biot theory and containing a random distribution of cylindrical cavities and that of an acoustic wave in a fluid containing a random polydisperse distribution of porous spheres. In the first case we use the generalization by Conoir-Norris of the Linton-Martin formula. It allows to take into account the phenomenon of the conversion between the three waves (two longitudinal and one transverse) naturally propagating in a porous Biot medium containing a random distribution of cavities. Analytical expressions are found for the effective wavenumbers of coherent waves in the Rayleigh limit (low frequency regime). The approximations of the densities and heterogeneous media modules are presented up to the order of c2 in concentration. The limiting case of random fluid cavities in an elastic matrix is also discussed. In the second case the effective wavenumbers, moduli and density are determined for polydisperse distributions of poroelastic spheres. To achieve this, the recent formulas of the effective wave number given by Linton and Martin in the dilute monodisperse case have been modified. Given the uncertainty for predicting the distribution in size of obstacles, three different probability densities are studied and compared: uniform, Schulz and lognormal. More precisely, the Rayleigh limit is taken into account when the wave lengths can be assumed to be very large compared to the size of the obstacles. Within this limit, simplified formulas for concentrations are provided depending on the parameter characterizing the size dispersion.; On étudie la propagation d’ondes acoustiques dans un milieu poreux obéissant à la théorie de Biotet contenant une distribution aléatoire de cavités cylindriques et celle d’une onde acoustique dans un fluide contenant une distribution polydisperse aléatoire de sphères poreuses. Dans le premier cas on utilise la généralisation de Conoir-Norris de la formule de Linton-Martin. En effet, elle permet de prendre en compte le phénomène de la conversion entre les trois ondes (deux longitudinales et une transversale) se propageant naturellement dans un milieu poreux de Biot contenant une distribution aléatoire de cavités. Des expressions analytiques sont trouvées pour les nombres d’onde effectifs des ondes cohérentes dans la limite de Rayleigh (régime basse fréquence). Les approximations des masses volumiques et modules des milieux hétérogènes sont fournies jusqu’à l’ordre de c2 en concentration. Le cas limite des cavités fluides aléatoires dans une matrice élastique est également discuté. Dans le deuxième cas on détermine les nombres d’ondes, modules et masses volumiques effectifs pour des distributions polydisperses de sphères poroélastiques. Pour y parvenir, les formules récentes du nombre d’onde effectif données par Linton et Martin dans le cas dilué monodisperse ont été modifiées. Compte tenu de l’incertitude entourant la prédiction de la distribution en taille des obstacles, trois densités de probabilité différentes sont étudiées et comparées : uniforme, Schulz et log-normal. Plus précisément, la limite de Rayleigh (régime de basse fréquence) est prise en compte lorsque les longueurs d’onde peuvent être supposées très grandes par rapport à la taille des obstacles. Dans cette limite, des formules simplifiées des concentrations sont fournies en fonction du paramètre caractérisant la dispersion en taille.

Most undergraduate students who have followed a thermodynamics course would have been asked to evaluate the volume occupied by one mole of air under standard conditions of pressure and temperature. However, what is this task exactly referring to? If air is to be regarded as a mixture, under what circumstances can this mixture be considered as comprising only one component called &ldquo, air&rdquo, in classical statistical mechanics? Furthermore, following the paradigmatic Gibbs&rsquo, mixing thought experiment, if one mixes air from a container with air from another container, all other things being equal, should there be a change in entropy? The present paper addresses these questions by developing a prior-based statistical mechanics framework to characterise binary mixtures&rsquo, composition realisations and their effect on thermodynamic free energies and entropies. It is found that (a) there exist circumstances for which an ideal binary mixture is thermodynamically equivalent to a single component ideal gas and (b) even when mixing two substances identical in their underlying composition, entropy increase does occur for finite size systems. The nature of the contributions to this increase is then discussed.

International audience; A polydisperse scattering model adapted for concentrated medium, namely the polydisperse structure factor model, was examined in order to explain the backscatter coefficients (BSCs) measured from packed cell samples undergoing cell death. Cell samples were scanned using high-frequency ultrasound in the 10-42 MHz bandwidth. A parameter estimation procedure was proposed in order to estimate the volume fraction and the relative impedance contrast that could explain the changes in BSC pattern by considering the actual change in cellular size distribution. Quantitative ultrasound parameters were estimated and related to the percentage of dead cells determined by flow cytometry. The standard deviation of scatterer size distribution extracted from the polydisperse structure factor model and the spectral intercept were found to be strongly correlated to the percentage of dead cells (r^2 =0.79 and r^2 =0.72, respectively). The current study contributes to the understanding of ultrasonic scatteringfrom cells undergoing cell death toward the monitoring of cancer therapy.

We study the propagation of acoustic waves in a porous medium obeying the Biot theory and containing a random distribution of cylindrical cavities and that of an acoustic wave in a fluid containing a random polydisperse distribution of porous spheres. In the first case we use the generalization by Conoir-Norris of the Linton-Martin formula. It allows to take into account the phenomenon of the conversion between the three waves (two longitudinal and one transverse) naturally propagating in a porous Biot medium containing a random distribution of cavities. Analytical expressions are found for the effective wavenumbers of coherent waves in the Rayleigh limit (low frequency regime). The approximations of the densities and heterogeneous media modules are presented up to the order of c2 in concentration. The limiting case of random fluid cavities in an elastic matrix is also discussed. In the second case the effective wavenumbers, moduli and density are determined for polydisperse distributions of poroelastic spheres. To achieve this, the recent formulas of the effective wave number given by Linton and Martin in the dilute monodisperse case have been modified. Given the uncertainty for predicting the distribution in size of obstacles, three different probability densities are studied and compared: uniform, Schulz and lognormal. More precisely, the Rayleigh limit is taken into account when the wave lengths can be assumed to be very large compared to the size of the obstacles. Within this limit, simplified formulas for concentrations are provided depending on the parameter characterizing the size dispersion., On étudie la propagation d’ondes acoustiques dans un milieu poreux obéissant à la théorie de Biotet contenant une distribution aléatoire de cavités cylindriques et celle d’une onde acoustique dans un fluide contenant une distribution polydisperse aléatoire de sphères poreuses. Dans le premier cas on utilise la généralisation de Conoir-Norris de la formule de Linton-Martin. En effet, elle permet de prendre en compte le phénomène de la conversion entre les trois ondes (deux longitudinales et une transversale) se propageant naturellement dans un milieu poreux de Biot contenant une distribution aléatoire de cavités. Des expressions analytiques sont trouvées pour les nombres d’onde effectifs des ondes cohérentes dans la limite de Rayleigh (régime basse fréquence). Les approximations des masses volumiques et modules des milieux hétérogènes sont fournies jusqu’à l’ordre de c2 en concentration. Le cas limite des cavités fluides aléatoires dans une matrice élastique est également discuté. Dans le deuxième cas on détermine les nombres d’ondes, modules et masses volumiques effectifs pour des distributions polydisperses de sphères poroélastiques. Pour y parvenir, les formules récentes du nombre d’onde effectif données par Linton et Martin dans le cas dilué monodisperse ont été modifiées. Compte tenu de l’incertitude entourant la prédiction de la distribution en taille des obstacles, trois densités de probabilité différentes sont étudiées et comparées : uniforme, Schulz et log-normal. Plus précisément, la limite de Rayleigh (régime de basse fréquence) est prise en compte lorsque les longueurs d’onde peuvent être supposées très grandes par rapport à la taille des obstacles. Dans cette limite, des formules simplifiées des concentrations sont fournies en fonction du paramètre caractérisant la dispersion en taille.

International audience; The effective wavenumber model of Linton and Martin [1] for the dilute monodisperse case (obstacles of identical sizes) is used to calculate the effective modulus and mass density of a polydisperse assembly of poroelastic spheres. We focus on the Rayleigh limit (low frequency regime) where the wavelengths can be considered very large compared to the size of the obstacles. In order to show the influence of the distribution in size of the obstacles, the special case of Schulz probability density function is considered.

European polymer journal 120, 109211 (2019). doi:10.1016/j.eurpolymj.2019.08.038, It is well known that amyloid beta-lactoglobulin (BLG) fibril solutions contain a heterogeneous mixture of amyloid aggregates and non-amyloid material. However, few information are available on how strongly separated fractions of different morphologies (straight fibrils at pH 2 and worm-like aggregates at pH 3.5) vary with respect to physicochemical properties and building blocks as most analyses are conducted with unfractionized solutions where superposition effects occur.The pH-value shift resulted in an altered degree of acid hydrolysis which led to dissimilar building blocks of the aggregates (peptides at pH 2, non-hydrolyzed protein at pH 3.5). The respective separated amyloid and non-amyloid fractions showed significantly different size (SAXS, SEC, AUC) and charge properties (Zeta potential) than the whole samples. Strong superposition effects were evident with common analyses such as FTIR, TRP fluorescence and Thioflavin-T. At the same time, structural differences of pH 2 and pH 3.5 aggregates could be presented more clearly., Published by Elsevier, New York, NY [u.a.]