Distribution Of Cell Areas Research Articles

Bread from composite cassava–wheat flour. II: Effect of cassava genotype and nitrogen fertilizer on bread quality

There is an increasing interest in the use of cassava roots for food and industrial purposes especially in the baking industry in Nigeria. Development of some cassava mosaic disease (CMD) resistant clones and application of inorganic fertilizers are principal strategies targeted in the country to boost and sustain cassava root production and utilization. A study was conducted to determine the effect of cassava genotype and field application of nitrogen fertilizer on some physical properties of bread from composite cassava–wheat (CCW) flour. Five CMD cassava clones were planted in a randomized complete block design with two level of fertilizer treatments (0 and 160 kg nitrogen/ha) with two replications while harvesting was done 12 months after planting. Composite flour was produced at a ratio of 10/90 (cassava/wheat flour, w/w). The oven spring, specific volume, crumb texture (softness) and crumb moisture of loaves ranged from −0.57 to 0.63 cm, 4.37 to 6.85 cm3/g, 18.4 to 29.4 mm and 31.40% to 34.70%, respectively. The crust’s tristimulus color parameters L∗, a∗, b∗ and brownness index also ranged from 54 to 67, 9 to 15, 22 to 29, and 57 to 83, respectively. These values differed significantly from each other at p < 0.01. Out of all these loaf properties, crumb texture was the most affected by the main and interactive effects of cassava genotype and fertilizer application (p < 0.001) while loaf weight was only affected by their interactive effects (p < 0.05). Digital image analysis of the bread crumb showed that the total number of cells, number of small cells and total cell area of the bread crumb ranged from about 22 to 27 cm−3, 20 to 25 cm−3 and 12% to 29%, respectively. The distribution of large cells and total cell area occupied in the crumb were principally determined by the genotypic difference (p < 0.05) in the cassava roots. The main effect of fertilizer application significantly affected the distribution of small cells, total number of cell and the cell area (p < 0.05). However, the interactive effects of genotype and fertilizer application was more significant (p < 0.01) on the crumb cell characteristics. The study indicated that optimal quality of CCW bread loaf could be attained by appropriate selection of cassava genotype and fertilizer application.

Morphological Analysis of Polyethylene Foams with Post-use Material Incorporated

This study investigated the morphology of low-density polyethylene (LDPE) foams with post-use polyethylene (p-PE) incorporated. Samples manufactured using compression molding were analyzed through scanning electron microscopy. Micrographs were treated using the software Image Tool for Windows, version 3.00. This allowed the determination of cell size (0–2500 μm) and cell area (0–1500 .103 μm2) distributions. The research found that all compositions with p-PE material incorporated (15, 30, 40, 50 and 70% w/w) had similar morphologies, except the composition with 70% of p-PE, which gave a more significant increase in the amount of smaller cells. In comparison to samples with virgin LDPE only, all samples with p-PE showed an increase in cells with smaller areas (< 60 μm) and smaller diameters (< 850 μm2), especially those with 70% p-PE. This finding may be explained by the smaller melt flow index of the p-PE (0.60 g.min-1) in relation to LDPE (l.74 g.min-1), which hinders cell growth. The addition up to 70%, of p-PE in formulations which contain 5% of azodicarbonamide leads to PE foams with ideal density ranges for use as packaging (30 to 70 kg.m3).

Rho Kinase Differentially Regulates Phosphorylation of Nonmuscle Myosin II Isoforms A and B during Cell Rounding and Migration

The actin-myosin cytoskeleton is generally accepted to produce the contractile forces necessary for cellular processes such as cell rounding and migration. All vertebrates examined to date are known to express at least two isoforms of non-muscle myosin II, referred to as myosin IIA and myosin IIB. Studies of myosin IIA and IIB in cultured cells and null mice suggest that these isoforms perform distinct functions. However, how each myosin II isoform contributes individually to all the cellular functions attributed to "myosin II" has yet to be fully characterized. Using isoform-specific small-interfering RNAs, we found that depletion of either isoform resulted in opposing migration phenotypes, with myosin IIA- and IIB-depleted cells exhibiting higher and lower wound healing migration rates, respectively. In addition, myosin IIA-depleted cells demonstrated impaired thrombin-induced cell rounding and undertook a more motile morphology, exhibiting decreased amounts of stress fibers and focal adhesions, with concomitant increases in cellular protrusions. Cells depleted of myosin IIB, however, were efficient in thrombin-induced cell rounding, displayed a more retractile phenotype, and maintained focal adhesions but only in the periphery. Last, we present evidence that Rho kinase preferentially regulates phosphorylation of the regulatory light chain associated with myosin IIA. Our data suggest that the myosin IIA and IIB isoforms are regulated by different signaling pathways to perform distinct cellular activities and that myosin IIA is preferentially required for Rho-mediated contractile functions.

Quantitative morphology analysis of polymers foamed with supercritical carbon dioxide using Voronoi diagrams

Porous polymeric materials have a good impact strength, light weight and high porosity. Therefore, these foams are used in a wide range of applications, including insulation, separation processes and packaging. Since it is important to have an objective comparison of polymeric foams, this paper discusses a quantitative method using Voronoi diagrams, which has been developed to analyze and compare different morphologies of polymers foamed with supercritical carbon dioxide, based on the average cell area, cell area distribution and homogeneity. In contrast to SEM analysis only, different foam morphologies can be compared with this technique in an objective manner. The analysis is based on the centers of the cells and is therefore to a large extent independent of the sample preparation. Using the Voronoi-approach, it is possible to extrapolate the 2D view of the SEM picture to a 3D representation of the foam with the thickness of one cell layer.

Study on the effect of flow maldistribution on the performance of the hollow fiber modules used in membrane distillation

This paper investigates the effects of flow maldistribution on the performance of hollow fiber module used in membrane distillation (MD). As a base of this work, the mathematical model for ideal hollow fiber module was established. To get the flow maldistribution mathematically, sub-division of the module was employed to divide the fiber bundle into a number of sub-regions with different characteristics. The regional behavior was obtained from the analysis of ideal module, and the overall performance of a practical module was obtained by the combination of its sub-regions. At lumen side, the flow maldistribution is caused by the polydispersity of fiber inner diameter, and a Gauss distribution was introduced to divide the fiber bundle. At the shell side, the flow maldistribution is caused by the non-uniformity of fiber packing, and the Voronoi tessellation technique was adopted to determine the distribution of polygonal cell area. The effects of flow maldistribution at the two sides of the membrane were assessed individually. The result shows that the polydispersity of fiber inner diameter has some negative effect on the module permeate flux at the conditions considered, and the negative influence of the non-uniformity of fiber packing on the module performance seemed to be more important. More studies were focused on the shell side, the module flux was found increasing with the increase of packing fraction and flowrates at the two sides of the membrane.

Nucleation, adatom capture, and island size distributions: Unified scaling analysis for submonolayer deposition

We consider the irreversible nucleation and growth of two-dimensional islands during submonolayer deposition in the regime of large island sizes. A quasihydrodynamic analysis of rate equations for island densities yields an ordinary differential equation (ODE) for the scaling function describing the island size distribution. This ODE involves the scaling function for the dependence on island size of {open_quotes}capture numbers{close_quotes} describing the aggregation of diffusing adatoms. The latter is determined via a quasihydrodynamic analysis of rate equations for the areas of {open_quotes}capture zones{close_quotes} surrounding islands. Alternatively, a more complicated analysis yields a partial differential equation (PDE) for the scaling function describing the joint probability distribution for island sizes and capture zone areas. Then, applying a moment analysis to this PDE, we obtain refined versions of the above ODE{close_quote}s, together with a third equation for the variance of the cell area distribution (for islands of a given size). The key nontrivial input to the above equations is a detailed characterization of nucleation. We analyze these equations for a general formulation of nucleation, as well as for an idealized picture considered previously, wherein nucleated islands have capture zones lying completely within those of existing islands.

Elliptic adaptive grid generation and area equidistribution

The derivation of elliptic adaptive grid control functions which satisfy the area equidistribution concept is presented. The resulting expressions are derived without approximation and are shown to provide explicit control over cell area distributions. A modification to the equidistribution concept which yields control functions that enable additional control of the near-boundary grid resolution is also proposed. A computer code which incorporates these control functions has been developed and is applied to a series of complex fluid flows to demonstrate the validity and utility of the derived expressions. Copyright © 1999 John Wiley & Sons, Ltd.

The Distribution of Cell Sizes of the Solar Chromospheric Network

This paper studies the cellular pattern of the supergranular network. We present an algorithm to draw a surface-filling cell pattern on an uninterrupted two-day sequence of Ca II K filtergrams with a 1 nm bandpass. The 60° × 40° field of view contains both quiet and enhanced network and plages. The algorithm uses a threshold-independent method of steepest descent on spatially smoothed and time-averaged images. We determine the distribution function of cell areas and find a broad, asymmetric spectrum of areas. The distribution is found to be invariant for different spatial smoothings if the cell areas are normalized to a unit mean. It is this invariance that leads us to believe we have determined the intrinsic distribution of cell areas. Extrapolation of the average cell size to zero spatial smoothing yields a characteristic cell diameter of L = 13-18 Mm. This is roughly half the generally quoted supergranular length scale L ≈ 32 Mm as determined with autocorrelation methods. The difference in characteristic cell size reflects the application of a different measurement method: the autocorrelation method as used by Simon & Leighton and others is preferentially weighted towards relatively large cells. We find no significant dependence of cell size on local magnetic flux density.

Lymphatic stomata in the murine diaphragmatic peritoneum: The timing of their appearance and a map of their distribution

Fluid and free cells in the peritoneal cavity enter the lymphatics through the lymphatic stomata which are channels connecting the lymphatics in the peritoneal side of the diaphragm with the peritoneal cavity. While the stomata thus play a very important in the physiology of the peritoneal cavity, it is unclear when they appear or how they are distributed on the diaphragm. We therefore conducted an embryological study of the process and timing of mouse lymphatic stomata development in the peritoneal surface of the diaphragm. The mouse diaphragm, at stage ranging from embryonic day 18 (ED18) to postnatal week 10 (PW10), was observed by scanning electron microscopy, and the number of lymphatic stomata was counted on each observation day. A map of the data was constructed to illustrate the process of appearance of lymphatic stomata. Lymphatic stomata were not found on ED18. They were first found on PD0 and their number increased exponentially until PW10. Lymphatic stomata were usually located in cuboidal cell areas but not in the areas lined with flattened cells. The cuboidal cell area with several lymphatic stomata was first found in the retroparasternal region on PD0, followed by in the muscular portion, as "ridges" on PD4 and "bands" on PD6 or up to a few days later. The long axis of the ridges and bands was oriented from the center to periphery of the diaphragm. Subsequently, cuboidal cell areas with lymphatic stomata formed along the border between the central tendon and the muscular portion, most frequently on PD10. Another cuboidal cell area with lymphatic stomata appeared rather suddenly ventral to the inferior vena cava on PD10. This was the full complement of cuboidal cell areas seen in the adult of PW10. These results verified that the course of the change of the shape and distribution of cuboidal cell areas parallels that of the underlying lymphatic lacunae, suggesting the delivery of some stimuli from the lymphatic lacunae to the overlying mesothelial cells that results in alternation of their cell shape.

A method for measuring two-dimensional dispersed state of particles

The Voronoi polygonal analysis has been available for evaluating the dispersed state of particles, where the coordinates of particle positions are measured and the Voronoi tessellation is conducted to obtain the distribution of cell areas. Although the method can provide precise data concerning particle dispersion, it has the demerit of being time consuming. Hence a simple method is proposed in this paper to obtain the distribution of Voronoi cell areas from the measurement of variation in local particle concentrations by a probe of adjustable size. Evaluation of the state of particle dispersion therefore becomes faster for TV monitoring systems.

Voronoi statistics of hard-core systems

Monte Carlo simulation studies of hard-core disks are used to generate Voronoi edge-length and cell-area statistics of non-Poisson point tesselations. The well-established empirical relationship, which seems to hold for most networks, that the average number of sides of neighbors of n-sided cells m n = 6 − a + (6 a + c)/ n is verified for hard-disk systems with packing fractions ranging from 0.49 to 0.82. The results presented here are consistent with c = μ 2 but not with a = 6 α. The cell-area distributions for these systems, and in particular the γ-quantiles A 5 and A 95, are compared with recently published data for hard-core systems with packing fractions up to 0.22.

Characteristics of Cell-Area Distributions of Planar Voronoi Mosaics

Characteristics of Cell-Area Distributions of Planar Voronoi Mosaics

Cell-area distributions of planar sections of spatial voronoi mosaics

Planar sections of spatial Voronoi mosaics with respect to Poisson, hard-core, and cluster point processes are considered. The cell-area distribution is determined by the type and the model parameters of the corresponding spatial point process. Monte Carlo methods are used to describe these relations quantitatively. The results are summarized in parameter diagrams. With their help it is possible to characterize a given empirical spatial mosaic by means of planar sections.

On the distribution of cell areas in a Voronoi network

Abstract The distribution of cell areas for a Voronoi network is examined by computer simulation, and a rough argument is presented as to how this form of distribution may be derived analytically. The resulting form is a gamma function as was previously used by Kiang (1966) to fit numerical data of cell areas. Computer-generated distributions for large samples of cells are here used to test this suggested function more stringently than in Kiang's work.

Quantitative Analysis of Wide-Field Endothelial Specular Photomicrographs

Samples from the center of a wide-field specular micrograph adequately assessed cell density and frequency distribution of cell areas. A preliminary analysis of the spread of values indicated whether an increased sample size was required. An algorithm determined how large a sample taken from the central photograph (three, five, or nine rectangles) was necessary to permit detection of a 10% change in cell area. This analysis of sample size also indicated that sampling by small-field specular microscopy was not representative of the surrounding square millimeter of corneal endothelium.

Automated Analysis of Wide-Field Specular Photomicrographs

This report describes computerized image enhancement and analysis from the digitized image of a wide-field specular micrograph to produce an output of frequency distribution of cell areas. The steps involved including image smoothing and averaging, followed by automated scanning to detect individual cell boundaries, and cell area calculation. The limitations of this method include the requirement for expensive interactive display hardware and a 10% misinterpretation of cell boundaries by the algorithm.

Sample Size for Estimating the Quantiles of Endothelial Cell-Area Distribution

The estimation of corneal endothelium mean cell area (and, hence, mean cell density) is an important problem in clinical ophthalmology. Mitotic division of these cells is not known to occur, and cell deaths are followed by the enlargement of adjacent cells. As a consequence, cell-area distributions change drastically as functions of age and disease. Changes in cell-area distributions, in particular multimodality and skewness due to aging, are observed, and give rise to some difficult sampling problems. In this paper, sample quantiles are investigated as an alternative to the use of the sample mean. Asymptotic approximations are provided for the sample sizes required to estimate population quantiles with a desired precision. Asymptotic sample sizes are then compared with those obtained from tolerance limits. Empirical sample quantiles that can be used as benchmarks to compare corneas of normal individuals against corneas with unknown cell-area distributions are also presented. Aspects that merit further investigation are noted.

Distribution of cell areas in normal and transplanted corneas

Endothelial cell areas in normal corneas and in transplanted corneas were examined with the clinical specular microscope. For each eye, the area of each of six cells on each of three slides was measured by planimetry. In a separate study on the same slides, the area of each of ten cells was measured with the MOP-III computer. In both normal and transplanted corneas, cell areas seem to follow the log-normal frequency distribution. Thus, the logarithm of the cell area is the appropriate measure of cell size and the mean log-area should be used to describe such a cell population. When log-area is examined and normal controls are compared to transplanted corneas, we find that the variability in mean log-area is much greater among transplanted corneas than among normals, that cell areas vary from one region of the central endothelium to another for transplants though not for normals, and that the variability of log-cell area on a single slide is the same for normals and for transplants. These findings have implications for the design and analysis of clinical studies and for the physiological processes that occur when endothelial cell loss is compensated by the growth of remaining cells. Based on these observations, we find that the common practice of describing endothelial cell populations by cell density is inappropriate. Rather, the mean log-area (or the geometric mean) should be so used.

Changes in the corneal endothelium as a function of age

In vivo photomicrography has been used to examine the corneal endothelium of humans as a function of age. Sixty-one normal volunteers of both sexes ranging in age from 20 to 89 years of age were photographed. The endothelial photographs were analyzed to determine mean endothelial cell area for the central cornea and the frequency distribution of cell areas for each subject. The mean endothelial cell area was found approximately to double from age 20 to age 80. The increase in mean endothelial cell area with age was found to be statistically significant to better than the 0·1% level. The frequency distribution of cell area and cellular pleomorphism were also found to change with age. There was a statistically significant variability in the values of the difference in mean endothelial cell area between the two eyes of the population studied with age.