Point-counting Method Research Articles

Quantitative Analysis of Thin Section using Frequency Measurement (Point Counting), a Case Study on Limestone of The Rajamandala Formation, Cikamuning, West Java, Indonesia

The description of thin sections observations has traditionally relied on the visual comparison method, often using a visual comparison chart. However, this method has interpretative limitations, as readings can vary between individuals, and the values produced tend to be rounded. The point counting method for determining frequency is one of the statistical approaches that quantitatively counts the presence of mineral grains or particles. The limestone samples were collected from the Rajamandala Formation in the Cikamuning area of West Java, Indonesia. The methodology involved petrographic observations using the point counting method, which entailed creating a grid on the thin sections with a total of 312 points and calculating the percentage of occurrence of the constituent rock compositions. The analysis results showed constituent composition percentages of 33.65% for corals, 52.24% for matrix, 4.81% for cement, 2.56% for calcite, 3.85% for replacement, and 2.88% for porosity, categorizing the rock as coral wackstone. The facies is determined based on the presence of biota, while diagenesis is determined by the presence of cement types, secondary porosity, and grain contacts. In the research area, the identified facies is open marine (FZ 7), and the diagenesis includes marine phreatic, meteoric phreatic, and burial diagenesis.

Thymus morphological characteristics in acute and chronic colitis in animals with different hypoxia tolerance

Hypoxia is connected with inflammation, and the severity of inflammatory diseases predominantly depends on individual tolerance to oxygen deficiency. Hypoxia-inducible factor, HIF-1, regulates the thymus functional state, and its activity varies in organisms with different hypoxia tolerance. It is likely that differences in individual hypoxia tolerance and the associated HIF-1 functional activity may influence the inflammatory diseases severity, such as acute and chronic ulcerative colitis. The study aim is to characterize the thymus morphological changes during acute and chronic colitis in animals with different hypoxia tolerance. The hypoxia tolerance of male C57Bl/6 mice was determined by “gasping time” at an “altitude” of 10,000 m in a decompression chamber. A month after determining hypoxia tolerance, the animals were modeled as acute colitis by replacing drinking water with a 1.5% dextran sulfate sodium for 5 days; the animals were removed from the experiment on the 7th day. Chronic colitis was modeled by animals consuming a 1% dextran sulfate sodium on days 1-4, 12-14 and 22-26; animals were removed from the experiment on the 60th day. The volume fraction of thymus structural and functional zones was assessed using the point counting method. The relative number of different thymic bodies types was assessed: consisting of 3-5 cells, 5 or more epithelial cells, with keratohyalin deposits and thymic bodies in the form of cyst-like cavities. During acute colitis, in the thymus only in susceptible mice, there was a significant cortex narrowing and an increase in the number of thymic bodies consisting of 5 or more cells. In chronic colitis, only in susceptible animals in comparison with the control group, the cortex volume fraction and the cortex to the medulla ratio increased significantly. In susceptible mice, the number of bodies with keratohyalin increased. In tolerant animals, the indicators did not change. Thus, differences in the thymus response to acute and chronic ulcerative colitis were identified between tolerant and susceptible to hypoxia animals. Only in susceptible mice, in acute colitis, was observed cortex narrowing, but in chronic colitis, cortex hyperplasia. The data obtained must be taken into account when conducting experimental studies of the thymus.

Distribution and Density of Common Woodpigeon (Columba palumbus) in Central Northern Bulgaria

The breeding density of the Woodpigeon was determined in square LH75 in the period from March to May 2023. For this purpose, a point counting method was used, and in addition, some characteristics of the habitats were taken into account. The breeding density of Woodpigeon in the present study was 16.42, 12.75 and 14.44 pairs/100ha, in March, April and May 2023 year, respectively. Breeding density decreases from March to May. Anova analysis showed statistically significant differences in the mean number of song pigeons by habitat and cropland types (F=8.11, p=0.005). The number of song Woodpigeons was significantly greater in open habitats with single large trees or small groups of large trees among grassland and meadows than in other breeding habitat types. Their number is relatively high in Silver lime forests, coniferous plantations, and in the fringe strip of all forest habitats. The number of song pigeons is also relatively high in cases where we have a lack of arable land in the fixed radius or in the presence of wheat. Their number in the fixed radius increased with increasing average tree height. The number of singing pigeons is positively correlated with tree height (R=0.49, F=2.132, p<0.0001). The latest data on the breeding density of the Woodpigeon are from the end of the last century in Bulgaria. This study presents first results on the breeding distribution and density of the species in an information-poor area.

Fetal Vertebral Chondrostasis—Significance of Excessive Cartilage in Vertebral Bodies of Newborns

Introduction: We describe an abnormality in fetal and neonatal vertebral bodies whose most conspicuous characteristic is an increase in cartilaginous matrix within cancellous osseous trabeculae. We have termed this finding fetal chondrostasis (FC). Methods: We initiated a retrospective review of autopsy reports in which this condition had been prospectively diagnosed during a 36-year period. The Chalkley point counting method was applied to histologic sections of vertebral bodies to assess the relative components of cartilage, bone, and bone marrow. The results were compared to those of three control groups whose causes of death were prematurity, birth trauma, and infection. Results: We found that on average, the cartilaginous content in the FC group was considerably greater in both preterm and term infants when compared to controls. FC seemed to evolve from diminished activity in the cartilaginous growth zone resulting in formation of excessively broad cartilaginous columns. These subsequently suffered from delayed resorption following their incorporation within cancellous bony trabeculae. Conclusion: Excess cartilage within cancellous bone of vertebral centra in newborns is merely one aspect of disturbed intrauterine osseous development but is seemingly more readily discernible than other features at this site. The most common clinical correlates for FC were multiple congenital anomalies, congenital heart disease, intrauterine growth retardation, prematurity, and certain maternal factors.

Design and characterization of novel Ti-8Mo-xFe-yCu alloys as implant materials: Evaluation of biocompatibility, mechanical properties, and antibacterial potential

Titanium and its alloys are highly desirable materials for biomedical metallic implants due to their superior specific strength, excellent corrosion resistance, and exceptional biocompatibility. Among these alloys, Ti6Al4V is widely used in practical biomedical applications because it offers an excellent combination of strength, fracture toughness, and corrosion resistance. However, recent research has revealed limitations in its biocompatibility attributed to the presence of toxic elements such as Al and V. In addition, it has been reported that Ti6Al4V is costly due to the addition of Vanadium and has the potential for post-implant inflammation. As a result, researchers have been investigating new biomedical beta-Ti alloys using biocompatible, affordable, and easily accessible beta-stabilizers like Mo, Fe, and Cu, to achieve similar performance as Ti6Al4V alloys. The present study aims to develop a novel biomedical alloy through the arc melting method, to obtain an implant material possessing low elastic moduli, biocompatibility, and antibacterial properties to mitigate the risk of post-implant inflammation. Microstructural analysis was conducted using microscopy and x-ray diffraction, while the mechanical properties were evaluated through micro vickers hardness testing machine and elastic moduli measurement utilizing the impulse excitation technique. Cytotoxicity assessment was performed using the (Cell Counting Kit-8) CCK-8 method, followed by an examination of the alloy's antibacterial properties using the point counting method. β-Ti single phase was obtained in this study with the addition of ≥1% Fe and ≥1% Cu. The Ti-8Mo-2Fe-2Cu alloy was found to have the lowest elastic moduli of 95 GPa. Electrochemical measurements show that the Ti-8Mo- xFe- yCu alloys have a lower corrosion current density of around 0.319–2.317 µA/cm2 compared to Ti6Al4V of 16.543 µA/cm2. The Ti-8Mo-1Fe-3Cu, Ti-8Mo-3Fe-1Cu, and Ti-8Mo-3Fe-3Cu alloys have comparable biocompatibility with Ti6Al4V with the viability of mesenchymal stem cells (MSCs) above 75% and have a positive antibacterial response. Ti-8Mo-3Fe-3Cu alloy demonstrates the most favorable blend of microstructure, mechanical attributes, corrosion resistance, cell viability, and antibacterial properties as an alternate biomaterial for implant applications.

Vesicularity, Density, and Crystal Size Distribution of Pumice-Scoria at South-Southeast Flank of Merapi Volcano: A Window Into Explosive Volcanic Eruption

Abstract Merapi, one of the most active volcanoes in Java Island of Sunda Arc, is a constant threat to the ten million people who live within its 10-km radius of the summit. In 2010, it experienced an explosive eruptive event, sending pumice-laden pyroclastic density currents (PDC) that extended as far as 15 km down its southeastern flank. We report field observations of PDC deposits on the south-southeast flank of the volcano and calculate the vesicularity, density and crystal size distribution of pumice–scoria fragments. The density of the pumice–scoria is measured by archimedes’ principle by weighting the sample in water. The vesicularity is determined from petrography using the point counting method. Crystal Size distribution (CSD) is determined by images from thin sections using plagioclase crystals to calculate the magma residence time. Based on their physical appearance, the pumice–scoria fragments from this area are grouped into: (1) white pumice, (2) grey pumice, and (3) dark scoria. The density of white pumice is overlapping with the grey pumice group (1.5-2 g/ml); while the dark scoria is the densest among others (>2 g/ml). The vesicularity of pumice–scoria ranges from 7-30%. CSD analysis is done in two most vesicular samples from each group. The CSD result gives both shallow and steep slopes which reflect the crystal size and population density. The slope suggests that magma residence times are (a) 11.49–249.68 years for grey pumice, (b) 5.03–194.54 years for white pumice, and (c) 3.83–273.36 years for dark scoria. This research suggests that the three types of pumice–scoria from the study area generally have similar crystallization path and time. Our CSD data shows that these pumice-scoria samples tend to have steeper slopes than lava samples, indicating a more uneven crystal-growth condition.

Assessment of meta-schist as a novel sustainable resource for Portland cement manufacturing

In this study, the use of meta-schist as an alternative to sand–clay in preparing cement raw mixtures was investigated for the first time. To produce the highest quality Portland cement clinker by examining the mineral and chemical properties of meta-schists, two different raw meal samples were prepared, utilising conventional cement clay as a baseline sample ((PC)Ref) and the other with meta-schist ((PC)MSC). The effects of both raw mixtures on burnability tests and reactivity were evaluated based on the unreacted lime content in samples after they had been sintered at 1200, 1300, 1350, 1400 and 1450°C. The porosity amount, distribution, grain structure of silicate phase crystals, and equivalent crystal diameters and amounts of meta-schist clinker phases (C3S, C2S, C3A and C4AF) examined by polarising optical microscope showed that they are suitable for the production of PC. The hydration products of the cement mortars were determined by scanning electron microscopy and energy-dispersive X-ray analysis at 2, 7 and 28 days. In addition, the compressive strength test results of (PC)MSC and (PC)Ref mortars after 28 days of curing ranged between 57 and 55.5 MPa, and the cement produced was classified as CEM I 42.5R.

Ornithofauna of Bartın Sökü Wildlife Development Area

Birds, which are important elements of biodiversity, are also an indicator of an ecosystem. However, this is only possible by knowing the bird species living in each region and their population densities. For this purpose, this study that we did, have based on two years of field observations. As a result of the observations and field studies carried out by point counting and line counting methods on nine different test routes, the species identified were identified, and their densities and their and status in the area were determined. Guidebooks were used to determine the species obtained of from the observations. As a result of the study, 53 different bird species belonging to 11 orders and 23 families were identified in the study area. Among the bird species identified, the Passeriformes order is the most common order in the area, with 34 different species, followed by the Falconiformes order, with five different species. They were identified species from Muscicapidae 8, Fringillidae 5, Paridae 4, Turdidae 4, Corvidae 3, Motacillidae 2, Sylvidae 2 and other families 1 in the Passeriformes order. In addition, 34 species identified in the area were native, 13 were summer migrants, 3 were winter migrants, and the remaining 3 were transit birds. Although it is a protected area, the intensive use of this area for wood production and the high hunter pressure in the area has been identified as the most important problems affecting the populations of bird species in the region. Determining the bird species of the Sökü Wildlife Development Area, where large mammal wild animals were previously identified, will contribute to other biodiversity studies to be carried out in the region.

Automated segmentation and quantification of retained austenite in AISI 4140 using image processing techniques

The mechanical properties of a material directly influenced by its microstructural phases and chemical composition. This study aimed to identify and quantify the retained austenite in AISI 4140 steel, a microstructural phase that can impact component durability and dimensional stability. A special etchant with sodium metabisulfite was used successfully to reveal retained austenite in microscopic images, as revealing it using typical etchants almost impossible. Image processing techniques, including the KNN supervised machine learning algorithm and segmentation MATLAB function, were employed to quantify retained austenite, with results compared to manual point counting method and XRD tests. A sequence of metallurgical and heat treatment processes was conducted to create the microstructural image dataset. Results showed that the specimens with no retained austenite in XRD tests did not reveal any in the microscopic images also, with only four cases out of sixteen showed retained austenite presence. The comparison showed reasonable and relatively close percentages to those calculated from XRD tests, with a maximum 2.37% difference with the MATLAB function, 4.91% with the KNN algorithm, and 2.76% with the manual method. The results suggest the potential for using this approach to confirm retained austenite presence and estimate its fraction without the need for XRD testing.

Detection of fine asbestos fibers using fluorescently labeled asbestos-binding proteins in talc

Asbestos contamination in common materials, including powdered talc used in manufacturing cosmetics, pharmaceuticals, and baby powder, is of great public concern. The use of polarized light microscopy (PLM) for asbestos detection is limited because it cannot detect fibers with diameters in the nano range. Furthermore, the use of electron microscopy (EM), the preferred method for determining asbestos contamination in talc, is hindered by a rather complicated and laborious process. Fluorescence microscopy (FM) is a simple analytical tool in modern life sciences, especially given its superior sensitivity and selectivity; however, it is rarely used for inorganic materials. Previously, we demonstrated that airborne asbestos fibers were fluorescently visualized under FM using fluorescently labeled asbestos-binding proteins. Here, we evaluated the FM method's feasibility in detecting fine asbestos fibers in powdered talc. The limit of detection of the fiber diameter of asbestos was approximately 0.06 µm using FM. The FM method's sensitivity surpassed that of PLM and approached that of EM, and thus, it can detect nano-scale fibers. Notably, the FM method enabled the selective visualization of asbestos fibers, including those hidden beneath numerous talc particles. A point counting method using FM images enabled a semi-quantitative analysis of 0.01–1.0% (w/w) asbestos contamination in talc.

Provenance and Paleoclimate Analysis of Sandstone from Meluhu Formation in Kendari, Southeast Sulawesi.

The Meluhu Formation consists of quartz sandstone, red shale, siltstone, and mudstone at the bottom part, and alternating black shale, sandstone, and thin limestone in the upper part. Petrographic components composition can reveal the litho-tectonic setting of a region. The composition of sandstone can be done by determining and counting the proportion of a quartz minerals, feldspar, and rock fragment from thin sections using petrographic analysis. This result can guide to depositional setting and paleoclimates of a region. The Provenance and paleoclimates studies of Meluhu Sandstone are still relatively new. The purpose of this study was to find out the provenance and paleoclimate of sandstone of Meluhu Formation which is exposed in 14 sites along Kendari and adjacent area. The method used to make petrographic observations followed by data processing using the point counting method. The sandstone in this study area was classified into sublitharenite, lithic arenite, arkose, subarkose, and greywacke. The origin of rock was interpreted as located in the recycled orogenic province, interior craton, and undissected arc. The paleoclimate that occurred in the formation of these siliciclastic rocks was arid to humid. Keywords: Meluhu Formation, provenance, paleoclimate, sandstone.

Brain Structural Changes in Schizophrenia Patients Compared to the Control: An MRI-based Cavalieri’s Method

Introduction: Schizophrenia is a severe psychotic brain disorder. One of the potential mechanisms underlying this disease may be volumetric changes in some brain regions. The present study aimed to employ magnetic resonance imaging (MRI) to estimate and quantitatively analyze the brain of patients with schizophrenia compared to the controls. Methods: This case-control study was conducted on MRI scans of 20 patients with schizophrenia and 20 healthy controls in Zahedan City, Southeastern Iran. MRIs with 4 mm slice thickness and 5 mm intervals in coronal and sagittal planes were captured. Then, quantitative parameters, including volume and volume density of various brain regions, were estimated in both groups using Cavalieri’s point counting method. Data analyses were performed using the Mann-Whitney U test. Results: The findings of this investigation revealed that volumes of gray matter, hippocampus, and gray/white matter in patients with schizophrenia were significantly lower than the controls (P˂0.05). The volumes of lateral ventricles in patients with schizophrenia (36.60±4.32 mm3) were significantly higher than the healthy individuals (30.10±7.98 mm3). However, there were no statistically significant differences between the two groups regarding the changes in the brain’s total volume, cerebral hemispheres, white matter, brain stem, cerebellum, and corpus callosum (P˃0.05). Conclusion: Volumetric estimations on brain MRI-based stereological technique can be helpful for elucidation of structural changes, following up the treatment trends, and evaluating the therapeutic situations in schizophrenia patients. Volumetric alternations in specific brain areas might be linked to cognitive impairments and the severity of symptoms in patients with schizophrenia. Further research is needed in this regard.

Comparison of In-Person Versus Teledermatology Consultation in the Development of a New Score: Analysis of Tinea Corporis Score from Baseline up to Two Follow-Up Visits

Background: Conventionally, dermatophytoses demand at least 6 weeks of treatment. However, frequent follow-up can be a burden for elderly, working population, and COVID-19 pandemic. Teledermatology consultation may reduce follow-up visits. Objective: To propose a new score that provides a periodic clinical audit and minimizes in-person follow-up visits for patient convenience. Materials and Methods: A comparative study between teledermatology and in-person (face-to-face) consultation was conducted in the outpatient department of dermatology JSS Hospital, Mysuru, India from December 2018 to July 2019. The tinea corporis (TC) score constitutes three components: (a) area involvement, (b) erythema intensity, and (c) border visibility. Area involvement by teledermatology consultation was calculated by point counting method of Bahmer. TC score is calculated as the product of area involved and the sum of the erythema intensity and border visibility. These patients were followed up on a weekly basis for a month and values of the proposed score derived from the two methods of consultation were compared. Statistical data collected were tabulated and assessed by the SPSS software version 20 (IBM Corporation, Chicago, USA). Results: There were 150 TC cases. Analysis of 77 patients who completed the first follow-up visit by in-person and teledermatology consultation showed that the tinea corporis score (TCS) decreased from 171.25, 157.94 from baseline to 97.4, 98.61, respectively (P = 0.001). Analysis of 30 patients who completed the second follow-up visits showed a reduction in TCS from 138.2, 152.7 to 68.2, 71.7, respectively (P = 0.001). The Pearson score obtained by the two methods in each visit (0.990, 0.969, and 0.971) resulted in a positive correlation. Conclusion: TC score may be recommended for both in-person and teledermatology consultation. The ease of calculation, objective assessment, and application of TC score in teledermatology consultation are the advantages.

Stereological Estimation of Bone Cyst Volume Using Computed Tomography Images: A Comparison with the Planimetry Technique

Objective: The exact volume of the bone cyst is fundamental for evaluation, treatment, and surgical management of the pathology related to any bone. The aim of this study was to introduce the stereological point-counting technique in bone cyst volume measurements on computed tomography images and to compare it with the planimetry technique. Methods: A total of 30 bone cyst volumes were estimated on CT images using stereological point-counting and the planimetry technique, which is based on the Cavalieri principle. The planimetric measurements were regarded as reference values. The stereological and planimetric volume estimations were performed by two independent observers twice. The estimation results of the two volumetric techniques were compared with the Wilcoxon signed-rank test. Intra-observer and inter-observer reliability of each volumetric technique was assessed. Results: For each bone cyst, 7-11 systematically sampled CT slices enabled reliable cyst volume estimations with a low coefficient of error (0.39%-3.12%). There was no significant difference between point counting and planimetry methods regarding volume measurements in both sessions (p>0.05), and these methods correlated well with each other. There was a significant inter-and intra-observer agreement for each volumetric method (ICC=0.9984 to 0.9988). The stereological approach was observed to take less time than the planimetric approach (mean 01:43±0.44 vs. 03.33±1:47 minutes) Conclusion: The stereological point-counting method can be well pertained to CT images for the reliable and reproducible assessment of bone cyst volume. Application of the point-counting method for volume estimation of bone cysts with different morphological features provides a great advantage in terms of both time-saving, applicability, and practicality in comparison with the planimetry technique.

Evaluation of needling/microneedling as an adjunct to phototherapy in the treatment of stable acral vitiligo: a comparative clinical and immunohistochemical study

Objectives To evaluate the efficacy and tolerability of needling/microneedling as an adjunct to NB-UVB phototherapy in the treatment of stable refractory patches of acral vitiligo, based upon clinical and immunohistochemical assessment of melanocyte count and distribution in response to needling/microneedling. Materials and methods Twenty patients with stable acral vitiligo (≥2 patches) were enrolled. One of the two index patches was randomized to receive needling or microneedling in conjunction with NB-UVB. Patients received phototherapy sessions 3 times weekly, while needling was carried out on biweekly basis for 6 months. Assessment was done clinically using point counting method, VESTA, and global patients’ satisfaction, and immunohistochemically by quantitative assessment of melanocyte count by Melan-A. Results No statistically significant difference was observed between NB-UVB monotherapy and either of the combined therapy regimens as regards the mean percentage change in vitiligo surface area (p = .451), mean change in absolute melanocyte count from baseline (p = .589), and mean VESTA (p = .916). Patches subjected to adjuvant microneedling/needling were afflicted by koebnerization in 50% and 20% of cases, respectively. Conclusion Neither microneedling nor needling appear to confer an added therapeutic value to NB-UVB phototherapy in the treatment of stable acral vitiligo. Moreover, both carry the risk of koebnerization.

The Status and Threats of Birds: A Case Study of Birds in Nayapul to Ghandruk Area, Kaski, Nepal

The purpose of this study is to quantify species diversity of birds in the study area and to explore the biotic and abiotic factors affecting the bird population. This study was carried out by using the fixed point counting method. The study area was situated in Annapurna Rural Municipality of Kaski district. A total of 147 bird species belonging to 46 families and 14 orders were identified in the study area. It was found that Muscicapidae was the largest family and Passeriformes the largest order. Among the reported species, 50% were residents, 31% were full-migrants, 18% were altitudinal migrants and the remaining were 1% nomadic. Habitats of birds included the forest 68%, the scrubland 17 %, the grassland 7% and the wetland 6 % of the study area. Similarly, the rocky area and artificial area covered 1% of the total species. The results showed that most of the bird species i.e. 136 were least concerned, 4 of them were nearly threatened, 3 of them were endangered, 3 were critically endangered and only one species was vulnerable. The most important threats included hunting and trapping, killing for fun, shift in crop production, use of insecticides and pesticides, improved storage devices, habitat destruction, developmental activities, tourism, buried carcasses and predatory.

Identification of maceral groups in Chinese bituminous coals based on semantic segmentation models

Automatic identification of coal macerals has been a long-term pursuit for coal petrologists. As the rapid developments of computational processing capacities and algorithms in recent years, deep learning has been experiencing a considerable progress and successfully applied to image analysis. Semantic segmentation algorithms based on deep learning were introduced to make a pixel-level classification of maceral groups in Chinese bituminous coals. A high quality dataset with 739 representative petrographic images was established based on the characteristics of coal macerals in Chinese bituminous coal. The petrographic images were annotated into six classes, i.e., vitrinite, inertinite, liptinite, dark minerals (clay minerals), bright minerals (pyrite), and epoxy (background). The unbalanced proportions of annotated classes were calibrated by mathematical methods. Three classic semantic segmentation models, U-Net, SegNet, and DeepLab V3+, were used to make a pixel-level identification of the coal macerals. Pixel Accuracy (PA), Intersection over Union (IOU) and BFScore were introduced to evaluate the performances of the segmentation. The results have shown that the loss curves and accuracy curves of the three models in the training process rapidly converged after iterations. The training time of U-net, SegNet, and DeepLab V3 + was 172 min, 637 min, and 135 min respectively. The average pixel accuracy of the three models was 73%, 73%, and 92% respectively. The IoU and BFScore of DeepLab V3 + were also higher than those of U-Net and SegNet. The DeepLab V3 + was the preferred method for maceral group identification considering the training efficiency and segmentation accuracy. The maceral group compositions determined by DeepLab V3 + model achieved similar results as the manual point-counting method. The semantic segmentation method based on deep learning meet the accuracy requirements of quantitative analysis of coal maceral groups.

Color Light Metallography Versus Electron Microscopy for Detecting and Estimating Various Phases in a High-Strength Multiphase Steel

In this study, fresh attempts have been made to identify and estimate the phase constituents of a high-silicon, medium carbon multiphase steel (DIN 1.5025 grade) subjected to austenitization at 900 °C for 5 min, followed by quenching and low-temperature bainitizing (Q&B) at 350 °C for 200 s. Several techniques were employed using different chemical etching reagents either individually (single-step) or in combination of two or more etchants in succession (multiple-step) for conducting color metallography. The results showed that the complex multiphase microstructures comprising a fine mixture of bainite, martensite and retained austenite phase constituents were selectivity stained/tinted with good contrasting resolution, as observed via conventional light optical microscopy observations. While the carbon-enriched martensite-retained austenite (M/RA) islands were revealed as cream-colored areas by using a double-step etching technique comprising etching with 10% ammonium persulfate followed by etching with Marble’s reagent, the dark gray-colored bainite packets were easily distinguishable from the brown-colored martensite regions. However, the high-carbon martensite and retained austenite in M/RA islands could be differentiated only after resorting to a triple-step etching technique comprising etching in succession with 2% nital, 10% ammonium persulfate solution and then warm Marble’s reagent at 30 °C. This revealed orange-colored martensite in contrast to cream-colored retained austenite in M/RA constituents, besides the presence of brown-colored martensite laths in the dark gray-colored bainitic matrix. A quadruple-step technique involving successive etching with 2% nital, 10% ammonium persulfate solution, Marble’s reagent and finally Klemm’s Ι reagent at 40 °C revealed even better contrast in comparison to the triple-step etching technique, particularly in distinguishing the RA from martensite. Observations using advanced techniques like field emission scanning electron microscopy (FE-SEM) and electron back scatter diffraction (EBSD) failed to differentiate untempered, high-carbon martensite from retained austenite in the M/RA islands and martensite laths from bainitic matrix, respectively. Transmission electron microscopy (TEM) studies successfully distinguished the RA from high-carbon martensite, as noticed in M/RA islands. The volume fraction of retained austenite estimated by EBSD, XRD and a point counting method on color micrographs of quadruple-step etched samples showed good agreement.

Modal Analysis of Rock Forming Minerals: Contribution of XRD/Rietveld Analysis Compared to the Classic Point Counting Method

The determination of the mineral composition of aggregates which constitute an important component of concrete is essential to understand and estimate the durability of structures. The modal (quantitative mineralogical) analysis of rocks is generally determined by point-counting method on thin sections or slabs. However, there is a difficulty of mineral identification depending not only on the experience and capability of the operator but also on the size of observable grains. In this study, XRD (X-Ray Diffraction)/Rietveld analysis is proposed as an alternative and a comparison study is performed for eight different rocks. The results show equivalent proportions to those of the point counting method for the major phases (minerals), although discrepancies are observed for the minor minerals. Complementary tests as XRF (X-Ray Fluorescence) and density measurements are also performed to pre-characterize and confirm the obtained modal analysis. For instance, the density calculations based on XRD/Rietveld analysis provide close values to the measured densities. Overall, this method can be an excellent alternative to the point counting method especially in the context of construction materials laboratory.

Influencing Factors on Petrography Interpretations in Provenance Research—A Case-Study Review

The use of framework petrography is a common initial step in provenance research of sand and sandstone. The data tend to be interpreted based on the three main components quartz, feldspar, and lithic fragments. Surprisingly often, this is done without taking other influencing factors than the tectonic setting of the catchment and/or the surroundings of the depositional basin into account. Based on a database of 14 studies with approximately 900 petrographic data points from sand and sandstone, this study demonstrates quantitative effects on the apparent composition resulting from both geological and non-geological biases. The study illustrates sandstone-classification differences based on different specifications of the three end-members quartz, feldspar, and lithic or rock fragments, how the point-counting method can affect the apparent petrographic composition of sandstone, how sorting and facies bias may be differentiated from a climate or provenance signal, and how bias due to diagenetic effects can be minimised. In conclusion, both geological and non-geological biases should be considered for provenance studies that include petrographic data.