Polydisperse Structure Research Articles

Quantitative ultrasound techniques for assessing thermal ablation: Measurement of the backscatter coefficient from ex vivo human liver.

Understanding the changes occurring in biological tissue during thermal ablation is at the heart of many current challenges in both therapy and medical imagingresearch. The objective of this work is to quantitatively interpret the scattering response of human liver samples, before and after thermal ablation. We report acoustic measurements performed involving n = 21 human liver samples. Thermal ablation is achieved at temperatures between 45 and 80°C and quantification of the irreversible changes in acoustic attenuation and Backscattering Coefficient (BSC) is reported, with a particular attention to thelatter. Both attenuation coefficient and BSCs were measured in the frequency range from 10 to 52 MHz. Scans were performed before heating and after cooling down. Attenuation coefficients were calculated using spectral difference method and BSC estimated using the reference phantommethod. Strong increases of attenuation coefficients and BSCs with heating temperature were observed. Quantitative ultrasonic parameters obtained with the polydisperse structure factor model (poly-SFM)are compared to histological observations and seen to be close to hepatocyte mean diameter (HMD). The results presented in this study provide a description of the impact of thermal ablation in human liver tissue on acoustic attenuation and the BSC. For the first time, quantitative agreement between the Effective Scatterer Diameter (ESD) estimated from BSC and HMD was shown, highlighting the important role of cellular network in the scattering response of the medium. This core result is an important step toward the determination of the nature of scattering sources in biologicaltissues.

Effect of the Structure Morphology on the Mechanical Properties of Crumpled Graphene Fiber

Crumpled graphene fiber is a promising structure to be a graphene precursor to enhance the production and mechanical properties of various carbon fibers. The primary goal of the present work is to study the crumpled graphene of different morphologies using molecular dynamics simulations to find the effect of the structural peculiarities on the mechanical properties, such as the tensile strength, elastic modulus, and deformation characteristics. Mono- and poly-disperse structures are considered under uniaxial tension along two different axes. As it is found, both structures are isotropic and stress–strain curves for tension along different directions are very similar. Young’s modulus of crumpled graphene is close, about 50 and 80 GPa; however, the strength of the polydisperse structure is bigger at the elastic regime. While a monodisperse structure can in-elastically deform until high tensile strength of 90 GPa, structure analysis showed that polydisperse crumpled graphene fiber pores appeared two times faster than the monodisperse ones.

Formulation of Clitoria ternatea Leaves-mediated Silver Nanoparticles to Control Aedes aegypti Larvae

Introduction: Global rise in the Aedes-borne diseases and harmful effects of synthetic insecticides has diverted research to explore secondary metabolites in plants as mosquito control agent in the form of nanoparticles. Current study investigated Clitoria ternatea-mediated nanoparticles against Aedes aegypti. Methods: The aqueous and hexane leaf extracts of C. ternatea were assayed against Ae. aegypti early fourth instars. The extract-mediated silver nanocomposites (AgNCs) were synthesized after optimizing the volume and concentration of silver nitrate solution. The synthesis was tracked by the colour change of reaction mixture from pale yellow to dark brown followed by monitoring with UV-Visible spectroscopy and Dynamic Light Scattering. Results: The biosynthesis of 3 mM, 4 mM and 5 mM AgNCs was traced at 438, 401 and 407 nm, respectively. The average particle size distribution ranged from 34.62 to 60.64 nm and polydispersity index was 0.6-0.7. The 24 h larval exposure with aqueous and hexane leaf extracts demonstrated respective LC50 values of 53.057 and 42.179 mg/L, which decreased significantly on larvicidal assay with NCs. The 5mM AgNCs showed the maximum efficiency with LC50 of 10.317 mg/L after 24 h. Scanning and transmission electron microscopy images demonstrated a spherical, poly-dispersed structure with diameter in the 1-27 nm range. The assays against non-targets; Moina and Cyclops ascertained the eco-safety of NCs. Conclusion: The study demonstrated the C. ternatea leaf extract as possible effective mosquito nano-larvicide, alternate to traditional insecticides. Field studies, which could not be held due to the current pandemic, would further ascertain the possible use of these NCs against Aedes larvae.

Cryoconcentrated soymilk and xanthan gum acted in stability of creamy sauce during storage

The formation of an emulsion with reduced lipid content can cause instability in the product during storage, requiring adaptations in the formulation. The objective of this work was to analyze the stability of the creamy sauce of cryoconcentrated soymilk stored for 60 days. The creamy sauce was prepared and packed in polyethylene bottles, sealed with aluminum seals and kept at room temperature. In physicochemical analyzes was noticed that the proteins and ashes were similar in all the samples and small differences in moisture and lipids contents, the pH remained below 4.0 and the beginning of the lipid oxidation was not verified in the follow-up period. The color of sauce showed slight differences during storage, but it remained a clear food, with yellow and green color. The microstructure of creamy sauce stored for two months was not altered, presenting polydisperse structures, packed and very close. Thus, the efficiency of the associated use of soy proteins and xanthan gum in the formation and stabilization of the emulsion for 60 days was proven. Therefore, this creamy sauce can be an alternative to increase the consumption of soy proteins, in food with half the lipid level when compared to the traditional ones.

Динамические характеристики скорости истечения жидкости из форсунок в струйных газопромывателях целлюлозного производства

It is shown that the modern development of pulp production technology is associated with the development of gas-liquid systems equipment. Such equipment provides the main technological processes of pulp cooking and regeneration of chemical reagents. Furthermore, this equipment, designed to recover chemical reagents and reduce their emissions into the environment, is part of the technological process. The use of scrubbers in pulp production has an advantage over many other industries, since it uses a closed liquor regeneration cycle. Currently, studies of the processes occurring in scrubbers of different types are becoming more numerous and fundamental. This paper is devoted to the development of jet scrubbers. These devices have a number of properties that do not have scrubbers of other types. They do not create resistance to the gas flow in the flue; they have a gravitational property due to ejection. Only jet scrubbers create the necessary conditions for the stability of the gas flow and have a jet effect that allows to significantly increase the efficiency of emissions cleaning. To implement the jet effect and intensify the technological equipment operation it is required to describe transfer processes in jet scrubbers with regard to polydisperse structure of drop flow and features of liquid splitting up into drops by centrifugal-jet nozzles. Scientific works devoted to the problem of realization of the jet effect showed the need to study the dynamics of liquid splitting in centrifugal-jet nozzles, which create a drop-filled jet with a large opening angle. The research purpose is to study the speed of the initial movement of drops in the area immediately after the splitting section of the continuous jet of liquid flowing from the nozzle. A photographic technique with two spark lamps was used for the experiment. At the same time, the distribution of irrigation density was controlled. The results of measuring the distributions of absolute speed of drops and irrigation density were compared with each other and the function of liquid speed distribution in the cross section of the gas-liquid jet of the jet scrubber was determined. Based on the obtained data, a theoretical model was developed to determine the initial speed of drops of centrifugal jet nozzles, an indicator required for the development of new jet scrubbers. The results can be applied to improve the technological processes of pulp production.

Numerical Simulation of Polydisperse Two-phase Unidirectional Fibrous Structures Electroelastic Deformation

In this work the problem formulation is stated, and a mathematical model is developed for calculating the electroelastic deformation of polydisperse two-phase unidirectional fibrous structures. The object of the research was a unidirectional transversely isotropic composite with a two-phase polydisperse structure - a piezo actuator cell and fragments of polydisperse fibrous structures. The constitutive relations at the composite macrolevel were obtained for longitudinal and transverse electromagnetic loading with allowance for the phase conductivity. The coefficients of the electromagnetic coupling of the composite were numerically determined depending on the volume fraction of the piezoelectric phase in the fibers and matrix form. The analysis of the obtained numerical solutions was carried out, the coincidence of the analytical solution with the solution of the asymptotic averaging method for an ideal periodic fibrous structure was obtained. Recommendations on the volumetric content of phases in a two-phase polydisperse composite are presented.

Contemporary macrocycles for discrete polymetallic complexes: precise control over structure and function.

The growth of multimetallic clusters and complexes can proceed in the presence of suitable ligands, but often leads to polydisperse structures with poor solubility. As an alternative approach, macrocyclic molecules can anchor the multimetallic complex, directing its formation and stabilizing the resulting product. This approach can provide excellent control over the growth of clusters, and offers a handle to control solubility and other properties of the resulting complexes. In this Tutorial Review, we discuss recent activity (primarily the last two decades) directed at the controlled and reproducible synthesis of multimetallic complexes using macrocyclic ligands. Throughout the review, we focus on the unusual structures that are only accessible by using macrocycles as ligands, and their unique properties.

Quantifying scattering from dense media using two-dimensional impedance maps.

A better understanding of ultrasound scattering in a three-dimensional (3D) medium can provide more accurate methods for ultrasound tissue characterization. The possibility of using two-dimensional impedance maps (2DZMs) based on correlation coefficients has shown promise in the case of isotropic and sparse medium [Luchies and Oelze, J. Acoust. Soc. Am. 139, 1557-1564 (2016)]. The present study investigates the use of 2DZMs in order to quantify 3D scatterer properties of dense media from two-dimensional (2D) histological slices. Two 2DZM approaches were studied: one based on the correlation coefficient and the other based on the 2D Fourier transform of 2DZMs. Both 2DZM approaches consist in estimating the backscatter coefficient (BSC) from several 2DZMs, and then the resulting BSC was fit to the theoretical polydisperse structure factor model to yield 3D scatterer properties. Simulation studies were performed to evaluate the ability of both 2DZM approaches to quantify scattering of a 3D medium containing randomly distributed polydisperse spheres or monodisperse ellipsoids. Experimental studies were also performed using the histology photomicrographs obtained from HT29 cell pellet phantoms. Results demonstrate that the 2DZM Fourier transform-based approach was more suitable than the correlation coefficient-based approach for estimating scatterer properties when using a small number of 2DZMs.

Preparation and characterization of liposomes loaded with silver nanoparticles obtained by green synthesis

The objective of this work was to develop and characterize liposomes loaded with silver nanoparticles (LAgNPs) to show improvement in stability characteristics. AgNPs were prepared by the green synthesis method with Aloe vera gel extract and exposure to sunlight. Liposomes were prepared by the modified reverse phase method. Particle size, polydispersity index, zeta potential, as well as the scanning electron microscopy (SEM) morphological aspects of AgNPs and LAgNPs were evaluated. In addition, was used flame atomic absorption spectroscopy to determine the amount of AgNP that was encapsulated in liposomes. The AgNPs presented as amorphous and polydisperse structures, with a mean diameter of 278.46 nm and zeta potential of -18.3 mV. LAgNPs had a mean diameter between 321 and 373 nm, the polydispersity index close to 0.2 and a zeta potential around -40 mV, which indicates greater stability to the AgNPs. The images obtained by SEM show semicircular structures for AgNPs and well-defined spherical shape for LAgNPs. The percentage of encapsulation was between 51.81 to 58.83%. These results showed that LAgNPs were obtained with adequate physicochemical characteristics as a release system.

One-pot synthesis of silver nanocomposites from Achyranthes aspera: An eco-friendly larvicide against Aedes aegypti L.

Objective: To formulate silver nanocomposites from Achyranthes aspera leaf extracts and evaluate its larvicidal activity against Aedes aegypti. Methods: The silver nanocomposites were synthesized from Achyranthes aspera leaf extracts. The process was optimized and traced through UV-visible and photon correlation spectroscopy. The larvicidal potential of silver nanocomposites of Achyranthes aspera leaf extracts was assessed against the early fourth instars of Aedes aegypti and three non-target organisms. Furthermore, the most effective and eco-safe nanocomposite was characterized by different biophysical techniques including scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform-infrared spectroscopy (FT-IR). Results: The formulated silver nanocomposites exhibited efficient larvicidal efficacy against Aedes aegypti. Bioassay with silver nanocomposites formulated using different AgNO 3 concentrations (3, 4, and 5 mM) revealed respective LC50 values of 37.570, 6.262 and 1.041 μg/mL; 5.819, 1.412 and 0.489 μg/mL; and 5.519, 1.302 and 0.267 μg/mL after 24, 48 and 72 h. The silver nanocomposites with 4 mM AgNO3 were selected for characterization. SEM and TEM analysis revealed spherical, poly-dispersed structure with varied diameters of 1-25 nm. The XRD analysis established the crystalline and face-centred-cubic structure of silver nanocomposites with the maximum peak at a 2θ value of 37.42°. The EDX pattern showed the presence of Ag, O and C in the nanocomposites in their order of weight%. The FT-IR displayed visibly distinct peaks in different ranges demonstrating the intricacy of silver nanocomposites. In addition, the lethal concentrations of silver nanocomposites of Achyranthes aspera leaf extracts against Aedes aegypti larvae were non-toxic to non-target organisms including Gambusia affinis, Daphnia magna and Moina macrocopa. Conclusions: Silver nanocomposites synthesized with leaf extract of Achyranthes aspera provide a cost-effective and eco-safe alternative to conventional insecticides, and can be utilized as a potent mosquito nano-larvicide.

ТЕОРЕТИЧНІ ПЕРЕДУМОВИ ЕКСПЛУАТАЦІЇ КОНСТРУКЦІЙ З МЕТАЛ-СКЛЯНИМИ ЗАХИСНИМИ ПОКРИТТЯМИ В УМОВАХ СУДНОВИХ ВІБРАЦІЙ

The article is devoted to looking for a solution for the scientific and technical issue of reducing vibrations on vessels. It is considered to be achieved with the application of the vibration-absorbing composite coatings. The purpose of the work is to theoretically substantiate the possibility of operation of structures with metal-glass coatings taking into consideration the vibration environment of a vessel. The formulation of the research includes the discovery of the solution for the micromechanics issue set up on the model of a two-layer plate St3 ‒ metal-glass coatings, taking into account their structural features, and experimental tensile tests. The influence of the polydisperse structure of coatings on the mechanisms of absorption of elastic-plastic waves of dynamic oscillations has been analyzed with the help of the analytical description of microdisplacement deformations. The influence of morphology and volume content of glass fillers, specifically hollow glass microspheres, powders of sodium silicate and lead-containing glass on the vibration coefficient, strength limit and yield strength has been investigated. Calculations have shown the feasibility of using metal-glass coatings in conditions of vessel vibration, which is due to the absorption of energy by glass inclusions of spherical and angular shape. It has been experimentally proven that coated plates are slightly inferior in tensile strength to samples with St3; the destruction of coatings occurs between glass inclusions. The obtained results have scientific and practical significance for the design of ship structures using composite materials and coatings.

Quantification of grain breakage during creep based on X-ray microtomography

Delayed compression is among the leading causes of long-term deterioration in granular systems, especially when it is mediated by the action of pore fluids. This time-dependent process is often classified as ‘creep’, a term conveying time-dependence without specifying the causes of deformation. This paper presents a methodology based on X-ray synchrotron microtomography to track delayed microstructural changes in compacted sand. Experiments on materials characterized by different grain size and shape have been designed to measure macroscopic variables such as strain rate, as well as to visualize the topological and morphological alterations of the constituting particles. The results reveal that non-negligible inelastic processes such as grain breakage manifest during the first stages of loading, as well as during the ensuing constant-stress delayed compaction. A substantial role of the grain morphology was detected in both stages. Specifically, while samples made of angular grains displayed early breakage due to the exacerbated fragility of the particles, specimens made of rounded grains did not develop a markedly polydisperse structure prior to creep, which led to comparably more intense delayed fracturing. Furthermore, samples consisting of round grains were also found to exhibit more intense shape alterations, with morphological indicators that tended to converge over time towards those of initially angular grains. These results suggest that characterization and simulation of creep in granular media need to encompass a variety of microscopic processes controlled by grain-scale properties, thus requiring multi-scale testing and modelling techniques.

CONCRETE COMPOSITES USING GRAND-SANDY MIXTURES OF DEPOSITS OF THE CHECHEN REPUBLIC

Objectives Development of optimal recipes of concrete mixtures using local natural raw materials in the form of gravel-sand mixtures from deposits of the Chechen Republic.Method The research methods adopted in the work are based on the theoretical principles and laws of designing and optimizing polydisperse multicomponent systems, the phase and structure formation of clinker minerals, the logic of mathematical calculations, the technological features of the structure formation of composite masses, the theoretical principles of controlling the rheological processes of mixes. All experimental data presented in the work were obtained according to the methods of current regulatory documents (GOST, recommendations, etc.).Result The paper presents the results of a study of the composition and properties of sand and gravel mixtures of deposits of the Chechen Republic and concretes based on them. In particular, the granulometric and chemical compositions and the physicomechanical properties of sand and gravel mixtures have been studied. An analysis of the scientific literature and experience in the use of sand and gravel in construction. The leading scientific schools of the country and abroad in the field of concrete science are presented. The rheological indices of concrete mixes were studied and the dynamics of the curing of concrete of different classes were obtained on the basis of unfortified sand and gravel mixtures in the presence of a chemical additive, the superplasticizer Polyplast SP-1.Conclusion It is proposed to use sand-gravel in its natural form in concrete for non-critical structures in its natural form without additional costs for enriching its composition. The feasibility of obtaining low-grade concrete with the use of sand and gravel mixtures without its enrichment and fractionation is established.

Probing the Cellular Size Distribution in Cell Samples Undergoing Cell Death

A polydisperse scattering model adapted for concentrated medium, namely the polydisperse structure factor model, was examined 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 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 (r2 = 0.79 and r2 = 0.72, respectively). This study contributes to the understanding of ultrasonic scattering from cells undergoing cell death toward the monitoring of cancer therapy.

An Artificial Neural Network (ANN) approach to extract micro-architectural properties of cortical bone using ultrasound attenuation: A numerical study

The goal of this study is to estimate the porosity parameters including pore diameter, pore density, and porosity of cortical bone from ultrasound attenuation measurements using an artificial neural network (ANN). Two-dimensional (2D) finite-difference time-domain simulations are conducted to calculate the frequency-dependent attenuation in the range of 1–8 MHz in mono-disperse structures (constant pore size) with a pore diameter and density ranging from 20 to 120 µm and 3–16 pore/mm2, respectively. Furthermore, poly-disperse structures (non-uniform pore distribution) are obtained from high resolution CT scans of human cortical bone and 2D numerical simulations are carried out in the same frequency range as for the mono-disperse cases. Then, a regression problem is formulated with the ultrasonic attenuation at different frequencies acting as the feature vectors and the output being set as the porosity parameters. Our dataset consists of 330 structures for the mono-disperse model and 668 structures for the poly-disperse model. ANN-based (3 hidden layers with 806 trainable weights) parameter prediction method achieves accuracies as high as 96% for pore size, 97% for porosity, and 78% for pore density for the poly-disperse model. This work demonstrates the potential of combining ultrasound methods to deep neural networks to quantify cortical bone parameters with high accuracies.

Role of Particle-Particle Interaction Towards Effective Interpretation of Z-Average and Particle Size Distributions from Dynamic Light Scattering (DLS) Analysis.

Despite the widespread utilization of Dynamic Light Scattering (DLS) as an analytical tool for particle sizing, one of the critical questions raised among the users is on how to do proper analysis and interpretation of the data obtained. In view of this, the present work was done to reveal the role of particle-particle interaction towards the interpretation of Z-average and the three types of particle size distributions (intensity-weighted, volume-weighted, and number-weighted) obtained from DLS analysis. Experimental results showed that Z-average for the weakly-interacting (highly stable) SiO2 particles obtained from DLS was almost identical to that gained from TEM analysis. Meanwhile, for the strongly-interacting (non-stable, aggregating) bare Fe3O4 particles, the Z-average obtained from DLS was ∼10 times larger than TEM result. In term of particle size distributions, it was found that all the three types of size distributions were closely collapsed into a single bell curve for the unimodal and monodisperse SiO2 particles; while for bare Fe3O4 particles which had been aggregated into polydisperse structures, the three size distributions exhibited large variation from each other. This observation implies that choosing the right size distribution become challenging in the latter case. Additionally, it was found that the Z-average of bare Fe3O4 particles varied significantly with the particle concentration used for DLS measurement. Concerning with particle aggregation kinetic, results from three independent case studies showed that the intensity-weighted distribution provides more logical and consistent right shifting as compared to both volume-weighted and number-weighted distributions.

Formation of Axially Aligned Polydisperse Nanocarbon Structures via Chemical Vapor Deposition from Cyclohexane with Ferrocene

Axial polydisperse carbon microstructures composed of vertically aligned arrays of multiwalled carbon nanotubes (MWCNTs) are synthesized via chemical vapor deposition (CVD) of cyclohexane with ferrocene onto a single-crystal silicon substrate. Their structural peculiarities are examined via scanning electron microscopy on a Tescan Lyra3 FEG system, atomic force microscopy on an Ntegra Spectra NT-MDT probe microscopy, by Raman spectroscopy. The abilities to purify synthesized carbon structures from amorphous carbon through oxidation with atomic oxygen and ozone are studied in order to achieve significant enlargement of specific surface area of nanotubes. The routes of application of polydisperse structures as catalyst supports, solid electrolytes, and chemical sensor supports, as well as absorption techniques of gas and liquid storage, are proposed.

Estimation of polydispersity in aggregating red blood cells by quantitative ultrasound backscatter analysis

Quantitative ultrasound techniques based on the backscatter coefficient (BSC) have been commonly used to characterize red blood cell (RBC) aggregation. Specifically, a scattering model is fitted to measured BSC and estimated parameters can provide a meaningful description of the RBC aggregates' structure (i.e., aggregate size and compactness). In most cases, scattering models assumed monodisperse RBC aggregates. This study proposes the Effective Medium Theory combined with the polydisperse Structure Factor Model (EMTSFM) to incorporate the polydispersity of aggregate size. From the measured BSC, this model allows estimating three structural parameters: the mean radius of the aggregate size distribution, the width of the distribution, and the compactness of the aggregates. Two successive experiments were conducted: a first experiment on blood sheared in a Couette flow device coupled with an ultrasonic probe, and a second experiment, on the same blood sample, sheared in a plane-plane rheometer coupled to a light microscope. Results demonstrated that the polydisperse EMTSFM provided the best fit to the BSC data when compared to the classical monodisperse models for the higher levels of aggregation at hematocrits between 10% and 40%. Fitting the polydisperse model yielded aggregate size distributions that were consistent with direct light microscope observations at low hematocrits.

The mathematical model of dynamics of dust plasma considering polydisperse structure of the condensed phase

Work is devoted to studying of non-stationary processes in the complex plasma representing a suspension of solid particles in the uncharged gas. This model constitutes the closed system of the multiphase mediums dynamics equations in two-dimensional statement which involves the bearing medium and the condensed phase movement equations.

Pyro- and electromagnetic effects in ferrite/barium titanate composite

New solutions for tensors of effective pyroelectromagnetic properties of piezoactive composites on the basis of boundary value problem solution for electromagnetic elasticity have been obtained. For the solution of the boundary value problem, new solutions for singular components of the second derivative Green functions for displacements, electric and magnetic potentials in homogeneous transversal isotropic piezoelectromagnetic medium with ellipsoidal grain of heterogeneity have been used. Calculation results on the concentration dependences for effective coefficients of pyromagnetic and electromagnetic coherence of ferrite/barium titanate composite with ellipsoidal, spherical and fibrous inclusions for various polydisperse structures and those of a layered structure composite have been presented. Considerable influence of the shape of the inclusions, features of relative positioning and inversion of the properties of phases on the effective coefficients of pyromagnetic and electromagnetic coherence of the composite material have been revealed. The conclusion is drawn on the preferable use of the pyroelectric phase as spherical inclusions, and ferrite as the composite matrix. This allows for more than a fivefold increase in the effective constant of pyromagnetic coherence of the composite material in comparison with its value for the same structure but with inversion of properties of phases for constant volume fractions of the ferrite and pyroelectric phases.