Dispersion Type Research Articles

Bio-inspired intelligence for minimizing losses in substrate integrated waveguide

This paper presents a study of various types of losses in substrate-integrated waveguides (SIW) using a genetic algorithm. Three main types of losses are considered and examined separately: conductor loss, dielectric loss, and radiation loss. Furthermore, the current analysis allows for a physical understanding of the loss impacts as well as the creation of design guidelines to reduce losses at 10 GHz frequency while keeping the miniaturized size of the SIW. Validation results obtained using the software Ansys HFSS, verify that the attenuation constant of the SIW can be significantly reduced to 0.4 dB/m, the Insertion loss S21 to -0.2 dB and the return loss to -38 dB if the geometric parameters are chosen properly. This study enables us to identify the source of losses in a SIW and, as a result, eliminate any type of dispersion. That demonstrates the usability of SIW technologies in the design of microwave circuits used in Internet of things applications.

Preparation of Ca(OH)2 nanoparticles by impinging stream reaction precipitation method

AbstractIn this paper, Ca(OH)2 nanoparticles are prepared by impinging stream co‐precipitation method. The process of preparing nanoparticles by impinging stream is optimized. The influence of process variable, such as dispersant type, dispersant dosage, circulating flow rate, reactant concentration ratio of OH− and Ca2+, reaction temperature and circulation time, on the particle size of Ca(OH)2 nanoparticle are investigated. The results show that the concentration ratio of reactants has a significant effect on the size of Ca(OH)2 nanoparticles. The optimal process conditions are obtained by single factor experiment, PEG6000, 3.3% dispersant dosage, Q = 1000 L · h−1, C = 1.88, T = 46.68°C and t = 60 min. The average particle size of Ca(OH)2 nanoparticles prepared under these conditions is 107.67 nm. According to the microstructure analysis, the prepared Ca(OH)2 nanoparticles samples have high purity and a good crystal structure. The powder dispersed with a marked hexagonal crystal shape and good thermal decomposition.

Cerium-modified single perovskite CaMnO3: structural, dielectric, and transport properties

ABSTRACT In this communication, the synthesis (solid-state reaction) and characterization (structural, dielectric, and transport) of the CaMn0.9Ce0.1O3 ceramic (named, CMCO) are discussed. The CMCO has an orthorhombic crystal symmetry with an average crystallite size of 108.7 nm and lattice strain of 0.00375 respectively. The grains are distributed uniformly in a very compact manner so that highly dense material is formed and the ratio of average grain size to average crystallite size is about 21, which may be a possible reason for a better dielectric and conductivity mechanism. Raman's study confirms the presence of all constituent elements. The analysis of the dielectric properties suggests the presence of the Maxwell-Wagner type of dispersion. The study of impedance spectroscopy reveals how grains and grain boundaries play an important role to define conductivity mechanism and hence prove a non-Debye type of relaxation. The analysis of the resistance versus temperature plots supports NTC thermistor character.

A fast look-up method for Bayesian mean-parameterised Conway–Maxwell–Poisson regression models

Count data that are subject to both under and overdispersion at some hierarchical level cannot be readily accommodated by classic models such as Poisson or negative binomial regression models. The mean-parameterised Conway–Maxwell–Poisson distribution allows for both types of dispersion within the same model, but is doubly intractable with an embedded normalising constant. We propose a look-up method where pre-computing values of the rate parameter dramatically reduces computing times and renders the proposed model a practicable alternative when faced with such bidispersed data. The approach is demonstrated and verified using a simulation study and applied to three datasets: an underdispersed small dataset on takeover bids, a medium dataset on yellow cards issued by referees in the English Premier League prior to and during the Covid-19 pandemic, and a large Test match cricket bowling dataset, the latter two of which each exhibit over and underdispersion at the individual level.

Tetragonal Nanosized Zirconia: Hydrothermal Synthesis and Its Performance as a Promising Ceramic Reinforcement

In this study, we produced zirconia nanoparticles with a pure tetragonal phase, good dispersion, and an average particle size of approximately 7.3 nm using the modified hydrothermal method. Zirconium oxychloride (ZrOCl2-8H2O) was used as zirconium source, while propanetriol was used as an additive. The influence of propanetriol content, sonication time, hydrothermal temperature, and type of dispersant on the physical phase and dispersibility of zirconia nanoparticles was investigated. Monoclinic zirconia was found to completely transform into a tetragonal structure when the mass fraction of glycerol was increased to 5 wt%. With the increase in the mechanical stirring time under ultrasonic conditions, the size distribution range of the prepared particles became narrower and then wider, and the particle size became first smaller and then larger. Ultrasonic and mechanical stirring for 5 min had the best effect. When comparing the effects of different dispersants (PEG8000, PVP, and CTAB), it was found that the average particle size of zirconia nanoparticles prepared with 0.5 wt% PVP was the smallest. Furthermore, by adding different concentrations of pure tetragonal phase nanozirconia to 3Y-ZrO2 as reinforcement additives, the bending strength of the prepared ceramics increased first and then decreased with increasing addition amounts. When the amount of addition was 1 wt% and the ceramic was calcined at 1600 °C, the flexural strength of the ceramic increased significantly, which was about 1.6 times that of the unadded ceramic. The results are expected to provide a reference for the reinforcement of high-purity zirconia ceramics.

Expanding undistorted transmission bandwidth for HF communications by leveraging the physical effect of intramode dispersion type transition

Expanding undistorted transmission bandwidth for HF communications by leveraging the physical effect of intramode dispersion type transition

Factors affecting cement leakage in percutaneous vertebroplasty: a retrospective cohort study of 309 patients.

Percutaneous vertebroplasty has been widely applied as a treatment for osteoporotic vertebral compression fracture. However, the incidence of cement leakage is high. The purpose of study is to identify the independent risk factors for cement leakage. A total of 309 patients who suffered from osteoporotic vertebral compression fracture (OVCF) and underwent percutaneous vertebroplasty (PVP) were enrolled in this respective cohort study from January 2014 to January 2020. Clinical and radiological characteristics were assessed to identify independent predictors for each type of cement leakage, including age, gender, course of disease, fracture level, morphology of vertebral fracture, fracture severity, cortical disruption in vertebral wall or endplate, fracture line connected with basivertebral foramen, type of cement dispersion, and intravertebral cement volume. In leakage of B-type, fracture line connected with basivertebral foramen was identified as an independent risk factor [Adjusted OR: 2.837, 95% CI: (1.295, 6.211), p = 0.009]. For leakage of C-type, acute course of the disease, more severity of the fractured body, wall disruption and intravertebral cement volume (IVCV) were identified as independent risk factors [Adjusted OR: 0.409, 95% CI: (0.257, 0.650), p = 0.000]; [Adjusted OR: 3.128, 95% CI: (2.202, 4.442), p = 0.000]; [Adjusted OR: 6.387, 95% CI: (3.077, 13.258), p = 0.000]; [Adjusted OR: 1.619, 95% CI: (1.308, 2.005), p = 0.000]. Regarding leakage of D-type, biconcave fracture and endplate disruption were identified as independent risk factors [Adjusted OR: 6.499, 95% CI: (2.752, 15.348), p = 0.000]; [Adjusted OR: 3.037, 95% CI: (1.421, 6.492), p = 0.004]. For S-type, fracture in thoracic level and less severity of the fractured body were identified as independent risk factors [Adjusted OR: 0.105, 95% CI: (0.059, 0.188), p = 0.000]; [Adjusted OR: 0.580, 95% CI: (0.436, 0.773), p = 0.000]. Cement leakage was very common with PVP. Each cement leakage had its own influence factors. Preoperative identification of above influence factors for cement leakage could avoid the occurrence of severe sequelae.

Modified wave operators for the Wave-Klein-Gordon system

We consider a coupled Wave-Klein-Gordon system in 3D, which is a simplified model for the global nonlinear stability of the Minkowski space-time for self-gravitating massive fields. In this paper we study the large-time asymptotic behavior of solutions to such systems, and prove modified wave operators for small and smooth data with mild decay at infinity. The key novelty comes from a crucial observation that the asymptotic dynamics are dictated by the resonant interactions. As a consequence, our main results include the derivation of a resonant system with good error bounds, and a detailed description of the asymptotic dynamics of such quasilinear evolution system of hyperbolic and dispersive type.

A Double Perovskite BiFeMoO6: Microstructural, Optical, Dielectric and Transport Properties

In this communication, the synthesis (solid-state sintering) and characterization of a double perovskite BiFeMoO6 are reported. Analysis of X-ray diffraction (XRD) data provides monoclinic crystal symmetry with an average crystallite size of 85.6[Formula: see text]nm and lattice strain of 0.00078, respectively. The microstructural analysis of the sample was done using a scanning electron microscope (SEM) and the results show that grains are well-grown and distributed uniformly throughout the sample surface. The grains are visible clearly due to well-defined grain boundaries, and the effect on the mechanism of electrical ac conductivity was studied. The compositional purity of the sample was checked by energy dispersive X-ray (EDX) analysis spectrum which supports the presence of all constituent elements (Bi, Fe, Mo and O) in both weight and atomic percentages. The study of the Ultraviolet–Visible spectrum provides a bandgap energy of 1.8[Formula: see text]eV, suitable for photovoltaic applications. The measurements of the dielectric were used to confirm the existence of the Maxwell–Wagner type of dispersion. The study of impedance spectroscopy helps to understand the negative temperature coefficient of resistance (NTCR) character while the electrical modulus measurements claimed a non-Debye relaxation mechanism in the sample. The study of ac conductivity reveals the fact of thermally activated conduction mechanism in the sample. The presence of the semiconducting nature of the sample was checked from both Nyquist plots and Cole–Cole plots. The study of the resistance versus temperature reveals the fact of negative temperature coefficient (NTC) thermistor character and is suitable for some temperature sensor devices.

Dispersive liquid-liquid microextraction/HPLC techniques for determination of oxytetracycline and doxycycline residues in beef samples: method developments and statistical analysis

A rapid, cost-effective and environment-friendly sample pre-treatment method involving dispersive liquid-liquid microextraction (DLLME) and high-performance liquid chromatography (HPLC) was developed and applied for the extraction of oxytetracycline and doxycycline residues in beef samples (liver, kidney and muscle). Several influencing factors associated with the extraction and separation of these antibiotics residues, such as sample size, type and volume of disperser and extraction solvents, centrifugation speed and time, were optimized using Plackett-Burman design and central composite design, while insignificant factors were fixed at values determined using univariate analysis. Figures of merit of the analytical methodology including the limit of detection (LOD), the limit of quantification (LOQ), accuracy (in terms of average recoveries), precision and calibration functions were established according to the European Union commission decision 2002/657/EC. Linearity, in the range of 5–500 µg/kg, was obtained with regression coefficients ranging from 0.9983 – 0.9999. Inter-day repeatability, intra-day precision, LODs and LOQs obtained were 3.81 – 14.90%, 3.80 – 8.70%, 4.21 – 4.69 µg/kg and 14.02 – 15.65 µg/kg respectively. Samples with detectable drug residues have oxytetracycline being the most commonly detected. The developed method was successfully established and the concentration levels of drug residues detected were lower than the European Union set maximum residue level (MRL).

Extinction time in growth models subject to geometric catastrophes

Recently, different dispersion strategies in population models subject to geometric catastrophes have been considered as strategies to improve the chance of population’s survival. Such dispersion strategies have been contrasted with the strategy where there is no dispersion, comparing the probabilities of survival. In this article, we contrast survival strategies when extinction occurs almost surely, evaluating which strategy prolongs population’s life span. Our results allow one to analyze what is the best strategy based on parameters as the probability that each individual exposed to catastrophe survives, the growth rate of the colony, the type of dispersion and the spatial restrictions.

A fungal mycelium containing abundant endoconidia from the Lower Devonian Rhynie cherts of Scotland

The Lower Devonian Rhynie cherts yield fossils of multiple types of fungal spores, but the systems that produced these spores are rarely preserved. Rhyniomycelium endoconidiarum gen. et sp. nov., a mycelium of uncertain affinity recently discovered in a degraded land plant axis from the Rhynie cherts, is characterized by endoconidia in virtually all hyphae, septa which typically occur in pairs and give off intrahyphal hyphae, and narrow hyphae ending in prominent, usually spheroidal heads that also contain, or consist of, conidia. The fossil hyphae closely resemble hyphae containing endoconidia of the extant ascomycete anamorph Geotrichum candidum (Saccharomycetales). Moreover, the fossil endoconidia appear to have originated from intrahyphal hyphae, precisely as in G. candidum. Conidiogenesis was probably thallic-arthric or thallic alternate-arthric. Rhyniomycelium endoconidiarum provides the oldest fossil evidence of endoconidia in fungi. Moreover, it links a dispersed spore type regularly encountered in the Rhynie cherts with a system in which spores of this type were produced. Documentation of such fossils contributes to our understanding of the evolution of reproductive processes in fungi.

In Ukrainian

Aromatic organic acids are among the common environmental pollutants that enter the water with washouts from agricultural lands, wastewater from chemical and pharmaceutical industries. Taking into account the high toxicity of aromatic substances, the important task of water purification is the removal of their trace amounts. This problem can be solved by using chemically modified inorganic materials, such as silicas, which have high mechanical, chemical, hydrolytic, and radiation stability. Therefore, they do not lose their sorption capacity during long-term use and do not pollute water with sorbent degradation products. The purpose of this work is the synthesis of a sorption-active material for removal of toxic aromatic acids by chemical immobilization of β-cyclodextrin functional groups on an aerosilogel (highly dispersed type of amorphous silica). A β-cyclodextrin-containing aerosilogel was synthesized by two-stage liquid-phase chemical modification of hydroxylated silica surface. Using the methods of IR spectroscopy, spectrophotometry, thermogravimetry, pH metry, low-temperature adsorption-desorption of nitrogen, chemical and elemental analysis of the surface, the surface structure and its quantitative chemical composition, and also parameters of porous structure of initial and chemically modified aerosilogels were determined. Sorption of benzoic, salicylic and β-resorcylic acids on aerosilogels from aqueous buffer solutions with pH=1 was studied. The insignificant contribution of silanol and aminopropyl groups and complete participation of chemically fixed β-cyclodextrin in the sorption of aromatic acids were proved. The results obtained are analyzed using kinetic models for pseudo-first and pseudo-second order processes, as well as Langmuir and Freundlich models for equilibrium adsorption on homogeneous and heterogeneous surfaces. It has been found that the sorption kinetic processes are well described by a pseudo-first order equation (in the presence of one type of functional groups on the surface) and a pseudo-second order equation for bi- and trifunctional aerosilogels. Experimental results on the equilibrium sorption of aromatic acids on β-cyclodextrin-containing aerosilogel are in good agreement with the Langmuir adsorption equation. This is evidence of decisive contribution of grafted oligosaccharide groups to the sorption of organic acids. The proposed chemical approach to increasing the sorption activity of aerosilogel can be used to obtain specific chromatographic carriers, as well as inorganic sorbents for the effective removal of small amounts of highly toxic organic substances from water and aqueous solutions.

Identification through machine learning of potential immune- related gene biomarkers associated with immune cell infiltration in myocardial infarction

BackgroundTo investigate the potential role of immune-related genes (IRGs) and immune cells in myocardial infarction (MI) and establish a nomogram model for diagnosing myocardial infarction.MethodsRaw and processed gene expression profiling datasets were archived from the Gene Expression Omnibus (GEO) database. Differentially expressed immune-related genes (DIRGs), which were screened out by four machine learning algorithms-partial least squares (PLS), random forest model (RF), k-nearest neighbor (KNN), and support vector machine model (SVM) were used in the diagnosis of MI.ResultsThe six key DIRGs (PTGER2, LGR6, IL17B, IL13RA1, CCL4, and ADM) were identified by the intersection of the minimal root mean square error (RMSE) of four machine learning algorithms, which were screened out to establish the nomogram model to predict the incidence of MI by using the rms package. The nomogram model exhibited the highest predictive accuracy and better potential clinical utility. The relative distribution of 22 types of immune cells was evaluated using cell type identification, which was done by estimating relative subsets of RNA transcripts (CIBERSORT) algorithm. The distribution of four types of immune cells, such as plasma cells, T cells follicular helper, Mast cells resting, and neutrophils, was significantly upregulated in MI, while five types of immune cell dispersion, T cells CD4 naive, macrophages M1, macrophages M2, dendritic cells resting, and mast cells activated in MI patients, were significantly downregulated in MI.ConclusionThis study demonstrated that IRGs were correlated with MI, suggesting that immune cells may be potential therapeutic targets of immunotherapy in MI.

Numerical modeling of magnetic field impact on the thermal behavior of a microchannel heat sink

The current appraisal evaluates the heat transfer phenomena of the nanofluid stream through the microchannel heat sink, considering the existence of a magnetic field. Moreover, Aluminum oxide (Al2o3)-water nanofluid is elected and implemented as a cooling fluid in this study. Also, the Koo–Kleinstreuer model (KKL correlation) is provided for the computation of the viscosity and effectual thermal conductivity of the nanofluid. Improved Darcy relationship is used for modeling the porous medium, and the two-equation approach's dispersion type is utilized for poking the heat transfer phenomenon among the solid and fluid zones. Due to the nonlinearity of the linked heat transfer relationships in mentioned phases, the well-known analytical Collocation method (CM) model decodes the issue. The influence of the void fraction and the diameter of the nanoparticles, temperature distribution, Hartmann number, fluid velocity, and channel geometry are discussed comprehensively. The obtained outcomes indicate that implementing the magnetic field has a direct connection with the Nusselt number. It was also found that heat transfer increases with the increase in nanofluid concentration. So, for the concentration of 0.04, there is the highest amount of heat transfer.

Characterization of the wild plants in Wadi Degla Protectorate, North Eastern Desert, Egypt.

The present study aimed to evaluate the floristic characteristics of the wild plants in Wadi Degla Protectorate, including taxonomic diversity, life and sex forms, dispersal types, economic potential, threats, and national and global floristic distributions. Field visits were conducted during January and April (2021), and the study area was divided to 185 locations to comprise all the Wadi. From each location, plant and seed specimens were collected. In the present study, 161 plants belonged to 128 genera, and 43 families were recorded. They inhabited three habitats (upstream, midstream, and downstream). Therophytes were the most represented life form. Bisexuals were the most represented sex form. Sarcochores were the most represented dispersal type, followed by desmochores. For small geographic range - national habitat - non-abundant plants were the most represented rarity form. For national scales, the Mediterranean and Sinai regions were the richest wild plants. For global scales, the Saharo-Sindian and Mediterranean regions were the most represented elements. Medicinal plants were the most represented good, while solid wastes were the most represented threat.

Lyophilization for Formulation Optimization of Drug-Loaded Thermoresponsive Polyelectrolyte Complex Nanogels from Functionalized Hyaluronic Acid

The lyophilization of nanogels is practical not only for their long-term conservation but also for adjusting their concentration and dispersant type during reconstitution for different applications. However, lyophilization strategies must be adapted to each kind of nanoformulation in order to minimize aggregation after reconstitution. In this work, the effects of formulation aspects (i.e., charge ratio, polymer concentration, thermoresponsive grafts, polycation type, cryoprotectant type, and concentration) on particle integrity after lyophilization and reconstitution for different types of polyelectrolyte complex nanogels (PEC-NGs) from hyaluronic acid (HA) were investigated. The main objective was to find the best approach for freeze-drying thermoresponsive PEC-NGs from Jeffamine-M-2005-functionalized HA, which has recently been developed as a potential platform for drug delivery. It was found that freeze-drying PEC-NG suspensions prepared at a relatively low polymer concentration of 0.2 g.L-1 with 0.2% (m/v) trehalose as a cryoprotectant allow the homogeneous redispersion of PEC-NGs when concentrated at 1 g.L-1 upon reconstitution in PBS without important aggregation (i.e., average particle size remaining under 350 nm), which could be applied to concentrate curcumin (CUR)-loaded PEC-NGs for optimizing CUR content. The thermoresponsive release of CUR from such concentrated PEC-NGs was also reverified, which showed a minor effect of freeze-drying on the drug release profile.

Dispersion and morphology analysis of PMMA/organoclay nanocomposites using the Ripley functions and determination of effective elastic properties

This paper deals with the microstructure of PMMA/organoclay nanocomposites and their effective elastic properties by the means of micro-mechanical modeling and numerical homogenization. PMMA matrix was reinforced by two types of organoclay (Cloisite 20A and Cloisite 30B) at both weight fraction from 1wt% to 5wt%. The microstructure characterization was based on the TEM images from which, Ripley functions K(r) and ImageJ software were used for organoclays dispersion and morphology analyses, respectively. Microstructures parameters such as elastic properties, volume fraction, random dispersion, platelet and prism inclusion types and aspect ratios were considered to 3D RVEs generation using Digimat-FE software. From the 3D RVEs, the numerical models were obtained and the effective elastic properties were determined by using Digimat-FE Solver. Thus, the variation of the computed properties has been investigated and illustrated. The Young’s moduli (E) of each aspect ratio were compared to experimental data. From the results, the nanocomposite rigidity depends not only on the organoclays volume fraction in PMMA matrix but also on the dispersion state and the considered aspect ratio. The inclusion type would therefore not have an important impact on the effective elastic properties. Considering the same volume fraction and dispersion state of the organoclays, the best elastic effective properties were obtained for the smallest aspect ratio.

Multivariate generalized linear mixed models for underdispersed count data

Researchers are often interested in understanding the relationship between a set of covariates and a set of response variables. To achieve this goal, the use of regression analysis, either linear or generalized linear models, is largely applied. However, such models only allow users to model one response variable at a time. Moreover, it is not possible to directly calculate from the regression model a correlation measure between the response variables. In this article, we employed the Multivariate Generalized Linear Mixed Models framework, which allows the specification of a set of response variables and calculates the correlation between them through a random effect structure that follows a multivariate normal distribution. We used the maximum likelihood estimation framework to estimate all model parameters using Laplace approximation to integrate out the random effects. The derivatives are provided by automatic differentiation. The outer maximization was made using a general-purpose algorithm such as PORT and Broyden–Fletcher–Goldfarb–Shanno algorithm (BFGS). We delimited this problem by studying count response variables with the following distributions: Poisson, negative binomial, Conway-Maxwell-Poisson (COM-Poisson), and double Poisson. While the first distribution can model only equidispersed data, the second models equi and overdispersed, and the third and fourth models all types of dispersion (i.e. including underdispersion). The models were implemented on software R with package TMB, based on C++ templates. Besides the full specification, models with simpler structures in the covariance matrix were considered (fixed and common variance, and ρ set to 0) and fixed dispersion. These models were applied to a dataset from the National Health and Nutrition Examination Survey, where two response variables are underdispersed and one can be considered equidispersed that were measured at 1281 subjects. The double Poisson full model specification overcame the other three competitors considering three goodness-of-fit measures: Akaike Information Criteria (AIC), Bayesian Information Criteria (BIC), and maximized log-likelihood. Consequently, it estimated parameters with smaller standard error and a greater number of significant correlation coefficients. Therefore, the proposed model can deal with multivariate count responses and measures the correlation between them taking into account the effects of the covariates.

Influence of different dispersants on the quality and stability of aqueous quinacridone magenta pigment dispersion for ink‐jet applications

AbstractThe stability of water‐based pigment dispersions is a key factor in determining their utility in ink‐jet applications, and the appropriate choice of dispersant plays a special role. Among the pigment formulations tested to date, literature data on magenta pigments are very limited. Thus, the goal of this work was to study the influence of the type and loading of dispersants on the quality and stability of quinacridone magenta pigment dispersions. Three different commercially available dispersants were tested: (1) a cationic styrene‐maleic anhydride copolymer, (2) an anionic polyacrylate, and (3) a nonionic alkyl ethoxylate. Pigment and dispersing agents were analysed using the Fourier Transform–infrared method. The stability of pigment dispersions was determined by comparative studies of changes in the pigment particle size, viscosity, pH, filtration time, optical density and gloss during the accelerated ageing test. Moreover, Turbiscan AGS and LUMiFuge analysers were used for evaluations of the instability of the dispersions. The properties of each dispersing agent affected the performances of the different dispersants. The highest stability for the pigment formulations was provided using the nonionic dispersant (small particle size, < 60 nm; the lowest viscosity < 60 mPa·s at the optimal dispersant content; favourable results of the filtration test; the highest pigment dispersability, proven by optical density and gloss). The Turbiscan AGS and LUMiFuge results indicated that the stability of all tested quinacridone magenta pigment dispersions was excellent (Turbiscan Stability Index values below three, and no significant differences in transmission profiles, respectively). However, it was found that the measurement results were influenced by the viscosity of the formulations.