Digital Image Analysis for Chemical Phase Identification and Particle Size Determination

A methodology employing digital image analysis for chemical phase identification and particle size determination is presented. The phase of unknown iron-oxide based particulate sample was identified by analyzing its transmission electron microscope diffraction patterns and diffraction contrast images using ImageJ pattern recognition software. A standard diffraction pattern with known crystallographic spacing and a standard diffraction contrast image with known fringe spacing were used to calibrate the sample’s diffraction patterns and diffraction contrast images, respectively. The phase of unknown sample was identified as iron (III) oxide with an average particle size of 8.9 nm computed from digitized binary images through thresholding process. The particles size distribution closely resembled Poisson cumulative distribution function with 61% of the particles having diameters between 1-10 nm. Keywords: Phase identification, ImageJ, Diffraction pattern, Digital image, Particle size determination

Application of Advanced Techniques for Metals Identification and Characterisation

The appraisal of metallic materials requires application of advanced characterisation techniques. In this paper, the use has been made of Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray diffraction (XRD) and Energy Dispersive X-ray Spectroscopy techniques to characterise morphological, structural and chemical composition of 316-stainless steel and unknown brass sample. The determined lattice parameter of unknown brass sample was 3.6812A and consisted of 63% Cu and 37% Zn by weight. The XRD analysis indicated a faced-centred-cubic crystal structure and the sample concluded to be an alpha brass. The measured dislocation density in 316-stainless steel increased with increasing plastic strain and the dislocation structures varied from relatively uniform distribution at low strains to cell-like structures at high strains. The spread of X-ray diffraction peak related linearly with the dislocation content of 316-stainless steel. Keywords: Characterisation, Crystal Structure Dislocation Structure, Diffraction Peak, Stainless Steel

Industrial Waste-water Characterisation and Image-Based Assessment of its Color Load

The characteristics of waste-water discharged from a reactive dyeing machine are examined and a simple method of quantifying its color load proposed. The discharged waste-water is typified by a pH value of 10.2, a turbidity value of 230 NTU, a color load of 290 mg/L and total suspended solids of about 970 mg/L. Application of digital image correlation to assess the color load in waste-water is explored through the use of Image Correlator plugin installed in the ImageJ software. The pixel scatter plot from the image correlation exhibit a characteristic spread with increasing concentration of dye solution thus demonstrating its applicability for waste-water color load assessment. The correlation coefficient derived from the image measurement, correlates almost linearly with the dye concentration in water and can thus be used for assessing the efficacy of color removal from the waste-water. With proper calibration, the resultant correlation curve can be applied in the quantification of the colour load in waste-water. Keywords: Digital Image Correlation, Waste-water, ImageJ, Color Load, Image Correlator, pixel scatter plo

Characterization of Clay Bricks Surface Deformation Behavior through Digital Image Analysis

Handmade compacted clay bricks are an important integral building material especially for the low cost durable and affordable housing segment. Characterisation of physical, mechanical and deformation behavior of handmade clay bricks is essential to ensure material integrity and durability. In this paper, physical and mechanical properties are determined and the Particle Image Velocimetry (PIV) method is used to assess deformation behavior of bricks under uniaxial compressive loading. The bricks exhibit brittle failure with high strain localized along the cracks. The initiation and development of cracks on loading redistribute compressive strain within the brick with some regions experiencing minimum strain at failure. The relatively large displacements between cracks account for relatively large failure strain for the brittle bricks. A good concurrence is established between the strain assessment based on uniaxial compressive test and on image correlation using the PIV method. The average vector magnitude derived from PIV measurements, correlate well with the engineering strain and can thus be used for strain estimation in handmade clay bricks. Keywords: clay brick, Digital Image Correlation, deformation, particle image velocimetry, characterisation

Fabrication, Characterization and Deformation Behavior of a New Acrylate Copolymer-based Nonwoven Structure

A method of fabricating nonwoven structure from dry-laid cotton fibers and atomized acrylate copolymer is presented. The method based on a consolidation pressure of about 2kPa and room temperature curing, is used to produce structures with fiber mass to binder volume ratio (FBR) of 0.7, 0.5, 1, 1.5, 2 and 3. Structurally stable structures are produced and characterized in terms of their bursting strength, areal density, water absorption, and monotonic deformation behavior. At constant FBR, the bursting strength and areal density of the structures increases with the fiber mass. The structures’ water absorption capacity reduces with the increase in the volume of binder applied. At FBR of 1 and area density of 295 grams per square meter, the structure’s load-strain curve is characterized by a linear and non-linear behavior corresponding to elastic and inelastic strain, respectively. At peak loads, the structure’s deformation is relatively uniform but becomes localized as the failure point is approached. A good correspondence is established between the strain assessment based on uniaxial tensile test and on image correlation using Particle Image Velocimetry (PIV) method. The average vector magnitude derived from PIV measurement, correlate well with the engineering strain and can thus be used for strain estimation. Keywords: Nonwoven, Dry-laid, Deformation, Particle Image Velocimetry, acrylate copolyme

Characterization of Surface Deformation Behavior, Mechanical and Physical Properties of Modified-clay Bricks

The demand for building material is ever increasing owing to population growth. Compacted clay bricks are an important integral building material especially for low cost durable and affordable housing segment. This is a valued building material since its properties can be modified to suit various loading conditions.  In this paper, the mechanical and physical properties of clay bricks modified with varying proportions of sawdust and polystyrene are determined. Increment of non-clay material proportion in the modified-clay bricks increases their porosity and water absorbency while their bulk densities, compressive and flexural strengths decreases. The use is made of Particle Image Velocimetry (PIV) method to assess the surface deformation behavior of the modified-clay bricks under uniaxial compressive loading. The distribution of surface deformation as assessed through PIV method is relatively uniform in pure-clay bricks while modified-clay bricks indicates a non-uniform deformation localized near the loading point at low strains. The strain distribution progressively spread out in the modified-clay brick as the failure point is approached. Keywords: Modified-clay brick, Digital Image Correlation, deformation, Particle Image Velocimetry, Characterisation

Global disparities in SARS-CoV-2 genomic surveillance

Genomic sequencing is essential to track the evolution and spread of SARS-CoV-2, optimize molecular tests, treatments, vaccines, and guide public health responses. To investigate the global SARS-CoV-2 genomic surveillance, we used sequences shared via GISAID to estimate the impact of sequencing intensity and turnaround times on variant detection in 189 countries. In the first two years of the pandemic, 78% of high-income countries sequenced >0.5% of their COVID-19 cases, while 42% of low- and middle-income countries reached that mark. Around 25% of the genomes from high income countries were submitted within 21 days, a pattern observed in 5% of the genomes from low- and middle-income countries. We found that sequencing around 0.5% of the cases, with a turnaround time <21 days, could provide a benchmark for SARS-CoV-2 genomic surveillance. Socioeconomic inequalities undermine the global pandemic preparedness, and efforts must be made to support low- and middle-income countries improve their local sequencing capacity

An EBSD study of the deformation of service-aged 316 austenitic steel

Electron backscatter diffraction (EBSD) has been used to examine the plastic deformation of an ex-service 316 austenitic stainless steel at 297K and 823K (24 °C and 550 °C)at strain rates 3.5x10-3 to 4 x 10-7 s-1. The distribution of local misorientations was found to depend on the imposed plastic strain following a lognormal distribution at true strains 0.1. At 823 K (550 °C), the distribution of misorientations depended on the applied strain rate. The evolution of lattice misorientations with increasing plastic strain up to 0.23 was quantified using the metrics kernel average misorientation, average intragrain misorientation, and low angle misorientation fraction. For strain rate down to 10-5 s-1 all metrics were insensitive to deformation temperature, mode (tension vs. compression) and orientation of the measurement plane. The strain sensitivity of the different metrics was found to depend on the misorientation ranges considered in their calculation. A simple new metric, proportion of undeformed grains, is proposed for assessing strain in both aged and unaged material. Lattice misorientations build up with strain faster in aged steel than in un-aged material and most of the metrics were sensitive to the effects of thermal aging. Ignoring aging effects leads to significant overestimation of the strains around welds. The EBSD results were compared with nanohardness measurements and good agreement established between the two techniques of assessing plastic strain in aged 316 steel

Genome sequence of the tsetse fly (Glossina morsitans):Vector of African trypanosomiasis

Tsetse flies are the sole vectors of human African trypanosomiasis throughout sub-Saharan Africa. Both sexes of adult tsetse feed exclusively on blood and contribute to disease transmission. Notable differences between tsetse and other disease vectors include obligate microbial symbioses, viviparous reproduction, and lactation. Here, we describe the sequence and annotation of the 366-megabase Glossina morsitans morsitans genome. Analysis of the genome and the 12,308 predicted protein-encoding genes led to multiple discoveries, including chromosomal integrations of bacterial (Wolbachia) genome sequences, a family of lactation-specific proteins, reduced complement of host pathogen recognition proteins, and reduced olfaction/chemosensory associated genes. These genome data provide a foundation for research into trypanosomiasis prevention and yield important insights with broad implications for multiple aspects of tsetse biology.IS