Presence Of Polydispersity Research Articles

Ultrasound assisted green synthesis of silver nanoparticles stabilized by chitosan polymers: Investigation of its therapeutic application in diarrhea

The current investigation aims to study the bio route preparation of chitosan capped-silver nanoparticles using aqueous flower extract of the Achillea ptarmica plant. The biosynthesized silver nanoparticles/chitosan (Ag NPs@CHI) were characterized by various spectroscopic techniques. The creation of Ag nanoparticles over the chitosan was initially determined by the presence of a single broad peak at 545 nm that was recorded by the UV–Vis spectrum. The presence of poly-dispersity, spherical shape and nanosizes in the Ag NPs@CHI were verified by the TEM and SEM pictures. The purity and crystalline nature of the prepared Ag NPs@CHI were confirmed by XRD analysis. In vivo, Ag NPs@CHI decreased the inflammatory cells presence in the colon and ileum, lowered the levels of IL-17A, IL-1β, IL-6, and TNF-α, raised the levels of IL-10 and IL-4 in colon tissues, enhanced acetate and propionate production. The findings revealed that Ag NPs@CHI have the potential to boost intestinal structure restoration, decrease levels of inflammatory cytokines and enhance short-chain fatty acid (SCFA) levels. Our research demonstrated that Ag NPs@CHI can safeguard the intestinal barrier by upregulating the expression of Claudin-1 and Occludin. Furthermore, silver nanoparticles suppressed the MAPK signaling pathway to ameliorate the inflammatory condition. Following the completion of clinical trials, these novel nanoparticles could serve as a promising new treatment for diarrhea in humans.

A computational geometry approach to pore network construction for granular packings

Pore network construction provides the ability to characterize and study the pore space of inhomogeneous and geometrically complex granular media in a range of scientific and engineering applications. Various approaches to the construction have been proposed, however subtle implementational details are frequently omitted, open access to source code is limited, and few studies compare multiple algorithms in the context of a specific application. This study presents, in detail, a new pore network construction algorithm, and provides a comprehensive comparison with two other, well-established Delaunay triangulation-based pore network construction methods. Source code is provided to encourage further development. The proposed algorithm avoids the expensive non-linear optimization procedure in existing Delaunay approaches, and is robust in the presence of polydispersity. Algorithms are compared in terms of structural, geometrical and advanced connectivity parameters, focusing on the application of fluid flow characteristics. Sensitivity of the various networks to permeability is assessed through network (Stokes) simulations and finite-element (Navier-Stokes) simulations. Results highlight strong dependencies of pore volume, pore connectivity, throat geometry and fluid conductance on the degree of tetrahedra merging and the specific characteristics of the throats targeted by the merging algorithm. The paper concludes with practical recommendations on the applicability of the three investigated algorithms.

Cavity averages for hard spheres in the presence of polydispersity and incomplete data.

We develop a cavity-based method which allows to extract thermodynamic properties from position information in hard-sphere/disk systems. So far, there are available-volume and free-volume methods. We add a third one, which we call available volume after take-out, and which is shown to be mathematically equivalent to the others. In applications, where data sets are finite, all three methods show limitations, and they do this in different parameter ranges. We illustrate the principal equivalence and the limitations on data from molecular dynamics: In particular, we test robustness against missing data. We have in mind experimental limitations where there is a small polydispersity, say 4% in the particle radii, but individual radii cannot be determined. We observe that, depending on the used method, the errors in such a situation are easily 100% for the pressure and 10kT for the chemical potentials. Our work is meant as guideline to the experimentalists for choosing the right one of the three methods, in order to keep the outcome of experimental data analysis meaningful.

Shape determination of polydisperse and polymorphic nanoobjects from small-angle X-ray scattering data (Computer simulation)

The most complete information about the structure of scattering objects from small-angle X-ray scattering (SAXS) data can be obtained basically for monodisperse systems of noninteracting particles. However, often in practice samples contain also a certain amount of aggregates and clusters that cannot be removed by conventional methods of purification, being the essential properties of the investigated objects. Moreover, the flexibility and intrinsic disordering of some samples also leads to difficulties of SAXS data interpretation and structural analysis. The most important questions that arise in these cases are the possibility of the structural reconstruction in general and the final reliability of the obtained models. In the current work we analyze the results of the shape determination of different geometrical bodies in the presence of polydispersity and in the presence of various amounts of aggregates, the shape determination of structurally polymorphic particles, and the shape reconstruction of geometrical bodies which are parts of their associates. The results of a series of numerical experiments allows us to describe the conditions and limits of such restorations, as well as to show some key approaches which may increase the stability of the shape reconstruction and reveal typical artifacts in the models.

Optimal parameters for a hierarchical grid data structure for contact detection in arbitrarily polydisperse particle systems

The objective of this paper is to find the optimum number of hierarchy levels and their cell sizes for contact detection algorithms based on a versatile hierarchical grid data structure, for polydisperse particle systems with arbitrary distribution of particle radii. These algorithms perform as fast as $$O(N)$$ for $$N$$ particles, but the prefactor can be as large as $$N$$ for a given system, depending on the algorithm parameters chosen, making a recipe for choosing these parameters necessary. We estimate theoretically the calculation time of two distinct algorithms for particle systems with various packing fractions, where the sizes of the particles are modelled by an arbitrary probability density function. We suggest several methods for choosing the number of hierarchy levels and the respective cell sizes, based on truncated power-law radii distributions with different exponents and widths. The theoretical estimations are then compared with simulation results for particle systems with up to one million particles. The proposed recipe for selecting the optimal hierarchical grid parameters allows to find contacts in arbitrarily polydisperse particle systems as fast as the commonly-used linked-cell method in purely monodisperse particle systems, i.e., extra work is avoided in presence of polydispersity. Furthermore, the contact detection time per particle even decreases slightly with increasing polydispersity or decreasing particle packing fraction.

Homogeneous and inhomogeneous hard-sphere mixtures: manifestations of structural crossover

Various manifestations of structural crossover in the properties of a binary mixture of hard-spheres are studied. For homogeneous mixtures that are sufficiently asymmetric, there is a crossover line in the phase diagram such that for thermodynamic states that lie on one side, the decay of the three bulk pair correlation functions is oscillatory with a common wavelength approximately equal to the diameter of the smaller spheres, and for states on the other side, the common wavelength is approximately the diameter of the bigger spheres. Using density functional theory it is shown that structural crossover manifests itself in the intermediate range decay of (i) the one-body density profiles of a hard-sphere mixture adsorbed at planar walls, (ii) the effective (depletion) potential between two big hard-spheres immersed in the same binary mixture, and (iii) the solvation force, or excess pressure, of the same mixture confined between two planar hard walls. The structural crossover line is determined exactly for a one-dimensional binary mixture of hard-rods and evidence is presented, based on density functional theory calculations and Monte-Carlo simulations, for structural crossover in homogeneous binary mixtures of hard-disks in two dimensions. By considering a multicomponent mixture of hard-spheres, with an appropriate bimodal distribution of diameters, it is argued that structural crossover should still occur in the presence of polydispersity and that these results could be relevant to colloidal mixtures where correlation functions can be measured using real-space techniques.

Translational Diffusion in Polydisperse Polymer Samples Studied by Dynamic Imaging of Diffusion ESR

A new methodology utilizing the DID-ESR (dynamic imaging of diffusion by ESR) technique has been developed for its application to polydisperse polymer samples. Due to polydispersity the spin-labeled polymer molecules have a wide range of molecular weight, and this is also true for the matrix polymer molecules. This generally leads to a wide distribution in diffusion coefficients of the spin-labeled molecules. The work presented here includes a theoretical derivation of the new DID-ESR method in the presence of polydispersity, plus its first application for measuring translational diffusion coefficients of liquid crystalline (LC) polymer melts. This includes a detailed analysis of the reliability of the method, the proper interpretation of average diffusion coefficients, and how the molecular weight dependence of the diffusion coefficient may be obtained from even a single experiment on a sample with wide polydispersity. The results obtained by this method are compared with those from the FRES (forward rec...

Thermodynamic aging of immiscible polymer blends

It is found by calculations that the presence of polydispersity in one of both constituents of a polymer blend results in a significant mutual solubility under conditions where a comparable strictly-binary blend would not show any detectable miscibility

Effects of polydispersity on fluorescence quenching in micelles

The effects of polydispersity on fluorescence quenching in micelle systems are discussed theoretically. Predictions are tested on computer generated fluorescence decay data for quenching in polydisperse micelle systems. It is shown that the estimated parameters, i.e, aggregation numbers and rate constants, are highly dependent on the micelle size distribution, and on the dynamic properties of the solubilizate–micelle system. Two extreme cases are considered: a static one, where no size changes of the micelles occur during the residence time, and a dynamic one where very large size variations take place. In the static case, the estimated aggregation number will decrease with quencher concentration from the weight average aggregation number in the limit of zero quencher concentration. In the dynamic case, the number average aggregation number is obtained, independent of quencher concentration. The initial decay constant contains information about the aggregation numbers, and in the generated data, this could be used to indicate the presence of polydispersity. Data from a number of experiments with the single photon counting technique are presented and analyzed according to the presented theory.