Values Of Area Fraction Research Articles

Activity-induced diffusion recovery in crowded colloidal suspensions.

We show that the forces generated by active enzyme molecules are strong enough to influence the dynamics of their surroundings under artificial crowded environments. We measured the behavior of polymer microparticles in a quasi-two-dimensional system under aqueous environment, at various area fraction values of particles. In the presence of enzymatic activity, not only was the diffusion of the suspended particles enhanced at shorter time-scales, but the system also showed a transition from subdiffusive to diffusive dynamics at longer time-scale limits. Similar observations were also recorded with enzyme-functionalized microparticles. Brownian dynamics simulations have been performed to support the experimental observations.

Enhancement of Critical Current Density of Nb3Al Superconductors by B Doping

Boron (B)‐doped Nb3Al superconductors are prepared by mechanical alloying and subsequent sintering process in this work. Then, the critical current density (Jc) of Nb3Al with different amounts of B doping is studied. In the results, it is shown that Jc performance of Nb3Al is improved obviously after B doping. The best Jc value obtained in this work is 2.2 × 104 A cm−2 (4.2 K, 5 T) for Nb3(Al0.9B0.1) sample. Furthermore, the mechanism of enhanced Jc performance for Nb3(Al0.9B0.1) sample is comprehensively explored. It is found that B doping can significantly enhance the grain connectivity of Nb3Al superconductor, and the active cross‐sectional area fraction values increase from 0.11 for the undoped sample to 0.34 for Nb3(Al0.9B0.1) sample. In addition, the lattice distortion caused by the interstitially dissolved B may also serve as flux pinning centers, which strengthens the flux pinning force of Nb3(Al0.9B0.1).

Low-level laser efficiency in reparation of bone defects

Introduction/Objective. Bone resorption is a common problem in dentistry, and bone reparation cannot be easily achieved. Several techniques of bone grafting and the use of low-level laser treatment (LLLT) as a new therapeutic optional recommended for improving bone repair were applied. The aim of the study was to investigate the influence of LLLT in bone repair of artificially made bone defects in the rat mandible using histomorphometry. Methods. The research was carried out on 60 female rats. Bone defects were made in the mandible, and animals were divided into two groups, each containing 30 animals. In the study group, the implantation site was submitted to GaAlAs laser irradiation 670 nm, 5 mW, 4 minutes per day for 5 days. The control group had no postoperative treatment. The animals were sacrificed after two, six, and eight weeks post LLLT, and preparations were analysed by histomorphometry, determining bone area fraction, bone area, integral density, mean density, and density variation. Results. Histomorphometric analysis revealed statistically higher values of area fraction, area, and integral density in the study group after two and six weeks. However, no beneficial laser effect was noticed after eight weeks. Conclusion. Low-level lasers have a stimulating effect on reparatory mechanisms in the early regeneration stage of artificially made bone defects in the rat mandible and can be used as a useful helping method in bone treatment.

(-)-Epicatechin Ameliorates Cardiac Fibrosis in a Female Rat Model of Pre-Heart Failure with Preserved Ejection Fraction.

One of the most abundant flavonoids present in cacao is (-)-epicatechin (Epi) and this flavanol has been linked to the cardiovascular health promoting actions of cocoa products. We previously demonstrated that Epi reduces infarct size in rodent models of ischemia/reperfusion and permanent coronary occlusion. Reduced infarct size was associated with decreased left ventricular (LV) oxidative stress (OS) and indicators of inflammation factors, which foster myocardial fibrosis. In this study, we examine the antifibrotic actions of Epi in an aging female rat model of pre-heart failure with preserved ejection fraction (pre-HFpEF) as well as its potential to mitigate plasma levels of OS, proinflammatory/profibrotic cytokines, and improve passive and active LV function. Epi treatment [1 mg/(kg·d)] was provided daily by gavage from 21 to 22 months of age, whereas controls received water. A Millar catheter was used to assess hemodynamic function. Subsequently, hearts were arrested in diastole, a balloon inserted into the LV and passive pressure-volume curves generated. Fixed LV sections were processed for collagen area fraction quantification using Sirius Red staining. Treatment with Epi did not lead to detectable changes in LV contractile function. However, passive LV pressure volume curves were significantly right shifted with Epi. Collagen area fraction values indicated that Epi treatment significantly reduces LV fibrosis. Epi also significantly reduced plasma OS markers and levels of profibrotic and proinflammatory cytokines. In conclusion, Epi reduces cardiac fibrosis in an aged, female rat model of pre-HFpEF, which correlates with significant reductions in OS and cytokine levels in the absence of changes in LV contractile function.

Dynamics of polydisperse multiple emulsions in microfluidic channels.

Multiple emulsions are a class of soft fluid in which small drops are immersed within a larger one and stabilized over long periods of time by a surfactant. We recently showed that, if a monodisperse multiple emulsion is subject to a pressure-driven flow, a wide variety of nonequilibrium steady states emerges at late times, whose dynamics relies on a complex interplay between hydrodynamic interactions and multibody collisions among internal drops. In this work, we use lattice Boltzmann simulations to study the dynamics of polydisperse double emulsions driven by a Poiseuille flow within a microfluidic channel. Our results show that their behavior is critically affected by multiple factors, such as initial position, polydispersity index, and area fraction occupied within the emulsion. While at low area fraction inner drops may exhibit either a periodic rotational motion (at low polydispersity) or arrange into nonmotile configurations (at high polydispersity) located far from each other, at larger values of area fraction they remain in tight contact and move unidirectionally. This decisively conditions their close-range dynamics, quantitatively assessed through a time-efficiency-like factor. Simulations also unveil the key role played by the capsule, whose shape changes can favor the formation of a selected number of nonequilibrium states in which both motile and nonmotile configurations are found.

Micro-computed tomography analysis of the lumbar pedicle wall.

BackgroundAlthough the pedicle is routinely used as a surgical fixation site, the pedicle wall bone area fraction (bone area per unit area) and its distribution at the isthmus of the pedicle remain unknown. The bone area fraction at the pedicle isthmus is an important factor contributing to the strength of pedicle screw constructs. This study investigates the lumbar pedicle wall microstructure based on micro-computed tomography.MethodsSix fresh-frozen cadaveric lumbar spines were analyzed. Left and right pedicles of each vertebra from L1 to L5 were resected for micro-computed tomography scanning. Data was analyzed with custom-written software to determine regional variation in pedicle wall bone area fraction. The pedicular cross-section was divided into four regions: lateral, medial, cranial, and caudal. The mean bone area fraction values for each region were calculated for all lumbar spine levels.ResultsThe lateral region showed lower bone area fraction than the medial region at all spinal levels. Bone area fraction in the medial region was the highest at all levels except for L4, and the median values were 99.8% (95.9–100%). There were significant differences between the lateral region and the caudal region at L1, L2 and L3, but none at L4 and L5. The bone area fraction in the lateral region was less than 64% at all spinal levels and that in the caudal region was less than 67% at the L4 and L5 levels.ConclusionsThis study provides initial detailed data on the lumbar pedicle wall microstructure based on micro-computed tomography. These findings may explain why there is a higher incidence of pedicle screw breach in the pedicle lateral and caudal walls.

Monte Carlo simulations of magnetic particle suspensions with a simple assessment method for the particle overlap between magnetic spheroids

We have developed a simple assessment method for the overlap between spheroidal particles, which neither requires the complex manipulation of vectors and matrices that is indispensable in the ordinary methods, nor is based on a model potential. Moreover, we have developed an evaluation method for the interaction energy arising from the overlap of the steric layer coating spheroidal particles. This is based on a sphere-connected particle model, but some modifications are introduced in order to express an appropriate repulsive interaction energy at the deepest overlapping position. We have investigated the phase change in a magnetic spheroidal particle suspension for a two-dimensional system by means of Monte Carlo simulations. In the case of no external magnetic field, if the magnetic particle-particle interaction is sufficiently strong to favour cluster formation, long raft-like clusters tend to be formed in a dilute situation. With decreasing values of area fraction, a chain-like structure in a dense situation transforms into a raft-like structure within a narrow range of the particle area fraction. Similarly, the raft-like clusters are preferred in a weak applied magnetic field, but an increase in the field strength induces a phase change from a raft-like into a chain-like structure.Highlights of the present paper:A simple assessment method has been proposed for the overlap between two spheroidal particles.The particle overlap assessment is free from a complex mathematical manipulation regarding vectors and matrices.A modified sphere-connected model has been proposed in order to more accurately evaluate a repulsive interaction due to the overlap of the steric layers coating spheroidal particles.2D Monte Carlo simulations have been performed to elucidate the phenomenon of a phase change by magnetic spheroidal particles on a material plane surface.A phase change between a raft-like and a chain-like aggregate structure is able to be controlled by the area fraction of particles and an external magnetic field.

Influence of working environment and built orientation on the tensile properties of selective laser melted AlSi10Mg alloy

AlSi10Mg alloy was fabricated by Selective Laser Melting (SLM) using two different atmospheres, argon and nitrogen, both in vertical and horizontal built directions. The influence of work environment and anisotropy are studied in this work by keeping all other process parameters including shielding gas pressure constant. The meso-structural features revealed scan tracks and melt pool layers while the microstructural features have showed cellular structure with α-Al matrix and its boundary made up of the eutectic mixture of Al and Si. These cells were approximately of 500 nm size as revealed by TEM analysis. The grain morphology and texture were studied using EBSD analysis. The XRD analysis revealed similarity in the phases formed in samples built under argon and nitrogen environment. Both the horizontal as well as vertical built samples contain elongated grains with 〈100〉 direction oriented along the built direction and 〈100〉 fibre texture in the XY plane. Tensile test results showed the maximum strength of 385 ± 5 MPa was exhibited by vertically built sample under nitrogen environment while the lowest strength of 338 ± 2 MPa was exhibited by horizontally built sample under argon environment. Surface roughness and porosity measured in all the conditions exhibited minor variation in the average surface roughness and porosity area fraction values. Among the samples tested under same built orientation, the variation in strength is approximately 5% higher in nitrogen environment while among the samples tested under same working environment, the variation in strength is approximately 7.5% higher in vertically built samples. This states that the influence of working environment on strength is lesser than that of the built orientation. The materials exhibited brittle failure with inclined fracture profile, fracture morphology with pores, river patterns and inter-cellular fracture plus approximately 4.5% elongation in all the tested samples, implied isotropic elongation behaviour. The samples built under both the work environments exhibited the similarity in defect structure, microstructure and nearly isotropic behaviour in mechanical properties. It inferred that nitrogen could be preferred over argon as shielding gas in SLM for its cost effectiveness.

A study of intracortical porosity's area fractions and aspect ratios using computer vision and pulse-coupled neural networks.

Employing computer vision (CV) and optimized pulse-coupled neural networks (PCNN), this work automatically quantifies the geometrical attributes of intracortical bone porosity (namely lacunae and canaliculi (L-C), Haversian canals, and resorption cavities). Fifty pathological slides of cortical bone (× 20 magnification) were prepared from middiaphysis of bovine forelegs collected fresh from butcher. Biopsies were subdivided into sectors encircling arcs (θ of 10°) and radial distances (R) originating from the bone's geometric center toward posterior regions and spanning 3.3mm. Microscopically, each pore is classified according to whether it belonged to primary or secondary osteon. Globally, each pore is assigned as being located in anterior or posterior regions. For each pore, area and major/minor axes lengths were determined as raw measures from which derived geometric measures, namely, area fraction (AF) and aspect ratio (AR), were derived. Said measures were plotted versus R (for different angles). Plots of AF and AR trends were found to vary linearly along the radial distance. Area fractions (%) significantly decreased linearly with R (p < 0.01) in the anterior region. In the posterior region, area fraction values are flat versus R. These findings are indicative of maturing osteons at the outer cortex with predominately near circular-shaped pores. Graphical abstract (Left) Grids of slides (magnified at 20X) of intra-cortical bone showing Lacunar-canalicular porosity (LCP). Areas marked with the dotted square represent a group of 25 images. The dashed line is a hand-drawn line that demarcates the anterior and posterior regions and the solid line is the best-fit arc radii (R =16.4 mm) of the dashed demarcation line. (Right) Images rotated in the polar coordinate system with their respective angles and radii shown.

Stereological bias for spherical particles with various particle compositions

Two-dimensional (2D) measurements of the cross-sections of polished mineral samples suffer from an overestimation of the degree of liberation known as stereological bias. Stereological bias is believed to be affected by the particle texture, i.e., the stereological bias of a simple locking particle is high, while the bias of a particle with a complex texture is negligible. However, scant work has been performed on the development of a quantitative and versatile modeling of stereological bias. We performed a series of numerical simulations: modeling particle assembly using the discrete element method; modeling the binary texture of particles by imposing phase patterns to the particles; systematical generation of 8608 types of phase patterns; liberation assessments in 2D and in three-dimension (3D) based on the error-free geometrical calculation; and stereological bias assessment by a comparison between liberations in 2D and 3D. Through these simulations, the correlation between the stereological biases of the phases and particle texture was investigated. Finally, the particle texture complexity was assessed using the fractal dimension of image intensity, and stereological bias for the matrix phase was successfully correlated with the fractal dimension and area fraction of the core phase. Fractal dimension and area fraction values are easily obtained by 2D measurements and subsequent image analysis. These results may lead to the establishment of a versatile stereological correction model that depends only on measurable 2D parameters.

Avaliação do desempenho de classificadores em metalografia quantitativa

As técnicas convencionais para aplicação da metalografia quantitativa têm sido cada vez mais substituídas por processos digitais devido à crescente necessidade de ganho de velocidade nas análises industriais e o processamento de imagens tem então ocupado um lugar importante nesse campo da metalurgia. Este trabalho teve como objetivo a implementação e avaliação de técnicas de inteligência e visão computacional na resolução de problemas de determinação de área de fases em aços AISI 1020. Para a comparação, três técnicas de decisão automática foram avaliadas: k-vizinhos mais próximos (KNN), que classifica os pontos da imagem através de correlação com a sua vizinhança e duas técnicas de classificação por aprendizado supervisionado: Redes Neurais Artificiais (RNA) e Máquinas de Vetores Suporte (SVM). Índices de indicação de qualidade de classificação também foram avaliados. Os resultados mostraram superioridade geral na técnica SVM no que tange, principalmente, o tempo de classificação e acurácia relativa, porém em todos os casos houve concordância com os valores de fração de área esperados para esse tipo de material, segundo análises metalúrgicas teóricas.

Constructal Design of Y-Shaped Conductive Pathways for Cooling a Heat-Generating Body

This paper applies constructal design to obtain numerically the configuration that facilitates the access of the heat that flows through Y-shaped pathways of a high-conductivity material embedded within a square-shaped heat-generating medium of low-conductivity to cooling this finite-size volume. The objective is to minimize the maximal excess of temperature of the whole system, i.e., the hot spots, independent of where they are located. The total volume and the volume of the material of high thermal conductivity are fixed. Results show that there is no universal optimal geometry for the Y-shaped pathways for every value of high conductivity investigated here. For small values of high thermal conductivity material the best shape presented a well defined format of Y. However, for larger values of high thermal conductivity the best geometry tends to a V-shaped (i.e., the length of stem is suppressed and the bifurcated branches penetrates deeply the heat-generating body towards the superior corners). A comparison between the Y-shaped pathway configuration with a simpler I-shaped blade and with X-shaped configuration was also performed. For constant values of area fraction occupied with a high-conductivity material and the ratio between the high thermal conductivity material and low conductivity of the heat-generating body (φ = 0.1 and = 100) the Y-shaped pathways performed 46% and 13% better when compared to I-shaped and X-shaped pathway configuration, respectively. The best thermal performance is obtained when the highest temperatures (hot spots) are better distributed in the temperature field, i.e., according to the constructal principle of optimal distribution of imperfections.

Image Analysis of Gluten-free Breads Prepared with Chestnut and Rice Flour and Baked in Different Ovens

In this study, the effects of chestnut flour and xanthan–guar gum blend–emulsifier DATEM mixture addition on macro- and microstructure of rice breads baked in conventional and infrared–microwave combination ovens were investigated by using the images obtained by a scanner and scanning electron microscopy (SEM). Pore area fraction, pore size distribution, and roundness values of pores were determined. The highest pore area fraction values were obtained in breads prepared by replacement of 46 % of rice flour with chestnut flour containing xanthan–guar gum blend–DATEM mixture and baked in an infrared–microwave combination oven. On the other hand, rice breads containing no additives or chestnut flour had the lowest pore area fraction values. Infrared–microwave combination baking increased both pore area fraction values and total number of pores. Infrared–microwave combination baking caused approximately 23–28 % increase in number of the small pores (0–5 mm2) in rice breads and 71 % increase in number of the large pores (>10 mm2) in chestnut–rice breads. The fiber content and larger starch granules of chestnut flour contributed towards the stabilization of gas bubbles resulting in better crumb structure. More homogenous pore distributions were observed when additives and an infrared–microwave combination oven were used. When microstructure of gluten-free breads was investigated, it was seen that starch granules in chestnut–rice breads baked in an infrared–microwave combination oven did not disintegrate completely.

Anatomical variations of trabecular bone structure in intraoral radiographs using fractal and particles count analyses

PurposeThis study was performed to evaluate possible variations in maxillary and mandibular bone texture of normal population using the fractal analysis, particles count, and area fraction in intraoral radiographs.Materials and MethodsPeriapical radiographs of patients who had full mouth intraoral radiographs were collected. Regions of interest (100×100 pixels) were located between the teeth of the maxillary anterior, premolar, and molar area, as well as the mandibular anterior, premolar, and molar areas. The fractal dimension (FD) was calculated by using the box counting method. The particle count (PC) and area fraction (AF) analyses were also performed.ResultsThere was no significant difference in the FD values among the different groups of age, gender, upper, and lower jaws. The mean FD value was 1.49±0.01. The mean PC ranged from 44 to 54, and the mean AF ranged from 10.92 to 11.85. The values of FD, PC, and AF were significantly correlated with each other except for the upper molar area.ConclusionAccording to the results, patients with normal trabecular pattern showed a FD of approximately 1.5. Based on these results, further investigation would be recommended if the FD value of patient significantly differenct from this number, since the alteration of this value indicates microstructural modification of trabecular pattern of the jaws. Additionally, with periapical radiographs, simple and cost-effective, PC and AF could be used to assess the deviation from the normal.

Measurements of the Effectiveness of Concave Spherical Dimples for Enhancement Heat Transfer

Measurements of the heat transfer enhancement effects of concave spherical dimples have been performed under hydrogen–oxygen hot-fire conditions in a subscale combustion chamber. Seven configurations were tested with a range of area densities from 15–70% and depth-to-diameter ratios of 0.111 to 0.333. Enhancements of 15–82% relative to a smooth surface weremeasured. TheReynolds number was varied by a factor of 5 andwas found to have an insignificant effect on the enhancement factor.Results correlatedwellwith previous studies conductedunder coldflow conditions with similar values of area fraction, depth-to-diameter ratio, and channel height-to-dimple diameter. These results are suitable for use by analysts and designers considering the use of heat transfer enhancement features on hot-gas walls for example in the design of high-performing expander cycle engines. Concave spherical dimples may have advantages over other approaches for enhancing heat transfer, such as protruding ribs with respect to the integrity of the chamberwall and the efficiency of the heat transfer enhancement relative to the associated increase in skin friction.

Interindividual and interspecies variations of the extrastriate visual cortex

Functional homology between human and macaque visual cortices has provided an important cue to functional subdivisions of the human visual cortex, but it is unclear beyond V1. We estimated the sizes and the visual field eccentricity functions of the extrastriate visual areas of human brains using MRI and fMRI measurements to analyze the interindividual and interspecies variations. We found distinctive features of the area fraction values relative to V1 and the visual field eccentricity functions beyond V2 between the human and the macaque visual cortices. This suggests that selection on color-form and stereoscopic vision, associated with processing and manipulating socio-visual stimuli, may generate variations of the architecture of the extrastriate visual cortex beyond V2.

Computational Simulations for the Assessment of the Mechanical Properties of Glass with Controlled Porosity.

Porous glass with closed controlled porosity is used as a model system in order to numerically assess the effect of pores on the macroscopic mechanical and fracture behavior of brittle solids. A computational code called OOF, which converts digitalized two-dimensional (2-D) images of materials microstructures into finite element meshes, is adopted, so that the effect of 2-D microstructural features (e.g. pore size and shape) on the global mechanical response of the material can be determined. Firstly, microstructures of porous glass bodies containing isolated pores were considered. These specimens were numerically investigated in terms of fracture initiation and propagation: the numerical model predicted that larger pores initiate fracture, in agreement with experimental results. Then, the effect of porosity on the elastic and fracture properties was thoroughly investigated by means of model two-dimensional microstructures consisting of selected area fractions of pores (equivalent to pore volume fractions in three dimensions) and with prescribed pore shape, orientation and dimensions. In particular, the effect of pore dimension and shape was studied, finding that the critical stress for crack initiation scales with pore dimension and aspect ratio, i.e. oblate and larger pores oriented perpendicularly to the stress direction cause a higher reduction of strength of the specimen. Finally, several 2-D microstructures characterized by different values of area fraction of pores of the same shape were investigated, in order to determine the variation of elastic properties and the fracture response of porous glasses with pore content. The study confirms the suitability of the 2-D OOF code to investigate the mechanical and fracture behavior of porous materials. Issues regarding the limitation of the model due to its 2-D character are also discussed where appropriate.

Intramural Distribution of Elastic Moduli in Thoracic Aortas and Its Relationship to Histology. Comparison between Porcine and Bovine Thoracic Aortas.

Local elastic moduli in the wall of porcine thoracic aortas were measured in the axial, circumferential, and radial directions by the pipette aspiration method. The local elastic moduli in the three directions were found to be independent of wall position. Then, histological analysis using color classification based on Mahalanobis' generalized distance was performed to quantitatively assess the correlation between elastic moduli and histology. Porcine thoracic aortas had a typical layered structure. The area fraction values, i.e., the percentage area of three structural components, elastin, collagen fibers and smooth muscle cells, were almost uniform in the wall. On the other hand, the moduli in bovine aortas reported previously decreased significantly from the inner to the outer sides of the wall. The histological structure was not homogeneous, that is, large clusters of smooth muscle cells existed in the outer side. These results suggest that the intramural distributions of elastic moduli are closely correlated with the histological structure.

半自動的色調判別に基づく生体組織標本の汎用画像解析法

It has been suggested that local elastic moduli of soft biological tissues relate closely with their histology. An image analysis method is proposed in which structural components in histological images are classified based on their color tones to obtain area fraction values and the position of the center of gravity of each component. similarity between colors was determined with Mahalanobis'generalized distance in (R, G, B)color space from predetermined color tones. In the present analysis, several characteristic color tones representing various colors in the input histological image(24-bit color)were specified first by an operator. Then, in the region of interest the pixel which represented the smallest distance from a color tone was classified into this color tone. The difference between areas, extracted manually and automatically was less than 6.6%and on comparison these regions were found to be practically equal. Thus the accuracy of this method was deemed sufficient for further analysis.