Preparation Of Thin Sections Research Articles

Preparation of Thin Sections of Porous Materials for Polarizing Microscope Investigation in Archaeometry

Preparation of Thin Sections of Porous Materials for Polarizing Microscope Investigation in Archaeometry

Non-Destructive and Destructive Monitoring Methods of Fibre Concrete Homogeneity

Design, preparation and testing of fibre-cement composites are a task of wide range of research workplaces and universities in our country and abroad. However, a question on homogeneity of all cement matrix components and mainly optimal dispersion of fibre reinforcement in a mixture has not been yet solved sufficiently. Within testing of properties of such designed composites there is usually a realized fact, that variability of these properties is distinctive mainly for the reason of uneven dispersion of commonly used fibres in a whole matrix volume. Elimination of this phenomenon could be achieved by means of a design of the optimal homogenization process of dry mixture components with fibre reinforcement. The aim of research works was to find suitable homogenization techniques, design of mixing process and optimal dosing of individual components. By means of these actions it is possible to achieve the best dispersion of selected fibre types, both metal and non-metal, in fine-grained cementitious matrixes, which is subsequently verified in hardened composites at first by non-destructive and then by destructive methods. Four different fibre-cement mixtures were chosen as representatives for commonly used reinforcement in fibre-cement composites and test specimens with a thickness of 40 mm were prepared using processes suitable for the specific fibre reinforcement. At the first stage non-destructive testing by means of ultrasound waves was carried out at first on a compact test slab with dimensions 500 x 500 x 40 mm and subsequently on individual test specimens with dimensions 250 x 40 x 40 mm, cut from the test slab according to a designed pattern. At the second stage destructive testing of test specimens was performed, mainly evaluation of flexural strength with 4-point bending and subsequently preparation of thin sections from the failure area for observation by means of polarizing microscopy. A purpose of all these research works is finding of correlation between testing by means of destructive and non-destructive methods.

Risk and benefit of diffraction in Energy Dispersive X-ray fluorescence mapping

Energy dispersive X-ray fluorescence mapping (μ-EDXRF) is a fast and non-destructive method for chemical quantification and therefore used in many scientific fields. The combination of spatial and chemical information is highly valuable for understanding geological processes. Problems occur with crystalline samples due to diffraction, which appears according to Bragg's law, depending on the energy of the X-ray beam, the incident angle and the crystal parameters. In the spectra these peaks can overlap with element peaks suggesting higher element concentrations. The aim of this study is to investigate the effect of diffraction, the possibility of diffraction removal and potential geoscientific applications for X-ray mapping. In this work the μ-EDXRF M4 Tornado from Bruker was operated with a Rh-tube and polychromatic beam with two SDD detectors mounted each at ±90° to the tube. Due to the polychromatic beam the Bragg condition fits for several mineral lattice planes. Since diffraction depends on the angle, it is shown that a novel correction approach can be applied by measuring from two different angles and calculating the minimum spectrum of both detectors gaining a better limit of quantification for this method. Furthermore, it is possible to use the diffraction information for separation of differently oriented crystallites within a monomineralic aggregate and obtain parameters like particle size distribution for the sample, as it is done by thin section image analysis in cross-polarized light. Only with μ-EDXRF this can be made on larger samples without preparation of thin sections.

Microscopy Techniques for Viewing the Inner Structure of Shear Bands in Sensitive Clays

Abstract Sample preparation and imaging techniques were evaluated for the investigation of fabric and the structures of shear bands in sensitive clays. This included the preparation of polished thin sections, which were studied in a polarized light microscope and in an electron probe micro-analyzer (EPMA). In addition, a set of samples was investigated by X-ray micro-Computerized Tomography, micro-CT. The shear band was seen as a non-continuous displacement field with complex inner patterns of shear fractures, like Riedel shears. Light microscopy of the thin sections was found to be useful for studying the outline and distribution of Riedel shears in the millimeter-sized shear band, whereas EPMA allows for studying microstructures at the micrometer level. The micro-CT makes it possible to extend the 2D representation of the studied macro-features from EPMA and light microscopy into 3D space. The main challenge with sensitive clays is sample preparation; the material can take little or no handling in its wet state, and when dried, substantial shrinkage occurs. The micro-CT holds several strong advantages which overcome these issues and also adds 3D visualization. Despite challenges related to image processing and image resolution versus sample size, the CT-tool is preferred for future studies of shear features in sensitive clays.

A Rapid On‐Site Method for Micromorphological Block Impregnation and Thin Section Preparation

This article presents a new method for on‐site preparation of large‐size micromorphological thin sections. This method is applicable for a broad range of disciplines, including but not unique to sedimentology, soil science, geology, and archaeology. We focus on testing a rapid on‐site impregnation using low‐viscosity Epoxy resin, a method that cuts short the time that elapses between field sampling, oven drying, and vacuum impregnation in the laboratory. Sediment samples from different sites in the southern Levant were impregnated, and results show that this on‐site impregnation method produces high‐quality results in terms of stratigraphic intactness, and ability to identify a variety of archaeological materials. The quality of impregnation was better in silty and sandy sediments rather than in clayey sediments. The on‐site impregnation method saves weeks to months of laboratory procedures and seems to be useful in Mediterranean and arid environments. We also present one example of grinding and polishing until a rudimentary thin section was produced on‐site in a matter of 3 days from sampling to finished thin section. The ability to produce thin micromorpholgical sections in a few days will influence excavation strategies and help answer geoarchaeological questions during the excavation season.

Spontaneous self-combustion of organic-rich lateglacial lake sediments after freeze-drying

We report and investigate for the first time spontaneous self-combustion of freeze-dried lacustrine sediments immediately after ventilation of the vacuum freeze dryer chamber. The smouldering and flameless combustion lasted for approximately 10–20 min and reached temperatures of 357 °C. Self-combustion mainly occurred in aluminium boxes containing sediment bars taken for thin section preparation. About 40 % of these samples were affected, most of them originated from the basal approximately 3-m-thick finely laminated lateglacial sediment interval. The combustion process caused disintegration of siderite to iron oxides (hematite and magnetite) and burning of organic matter to pyrogenic carbon leading to a lowering of total inorganic and organic carbon contents to 1 %. The total sulphur content of one combusted bulk sample did not change, but the alteration of sulphur contents in different sediment components suggests a redistribution of sulphur within the sediment. We assume that the self-combustion process was initiated by exothermic oxidation reactions, which were favoured by a combination of factors including the presence of abundant fine-grained iron sulphides in the organic-rich sediments. Self-combustion could be prevented by ventilating the vacuum chamber after freeze-drying with N2.

Preparation of Optical Thin Section of Bentonite

Preparation of Optical Thin Section of Bentonite

Applications of Blue Light-curing Acrylic Resin to Forensic Sample Preparation and Microtomy.

This study discusses the results of an evaluation of a one-part blue light-curing acrylic resin for embedding trace evidence prior to the preparation of thin sections with a microtome. Through a comparison to several epoxy resins, the physical properties relevant to both trace evidence examination and analytical microscopy in general, including as viscosity, clarity, color, hardness, and cure speed, were explored. Finally, thin sections from paint samples embedded in this acrylic resin were evaluated to determine if, through smearing or impregnation, the resin contributed to the infrared spectra. The results of this study show that blue light-curing acrylic resins provide the desired properties of an embedding medium, generate high-quality thin sections, and can significantly simplify the preparation of paint chips, fibers and a multitude of other types of microscopic samples in the forensic trace evidence laboratory.

Influence of Geology and Groundwater Fluctuation on the Instability of Road Pavement between Shango and Paiko along Minna – Lambata Road, Central Nigeria

The geology and groundwater condition of the area was studied with the aim of understanding their impact on the instability of the road in the study area. These include the petrology, geophysics and groundwater fluctuation (percentage in water table fluctuation). The methodology included geological field mapping, thin section preparation, resistivity and water table monitoring in dry and wet seasons. The study reveals that the road is underlain by schist, amphibolites and poorly fractured granite with quartz, biotite, hornblende and muscovite as the constituent minerals. The rocks have been altered through weathering to clayey minerals with resistivity values as low as 14 Ohm with the depth of weathering as high as 20 meter especially in the schist. The percentage of groundwater variation ranges between 154% and 2400% indicating medium to very high percentage of variation of groundwater fluctuation. These clay minerals absorb water and swell during the raining season and dry during the dry season. The result is the instability of the road pavement especially within the schist and where the elevation is lower. Proper design of the road and the provision of good drainage that will reduce the ingress of water are advised.

Bronze Age vitreous materials from Punta di Zambrone (southern Italy)

This study presents the results of an archaeometrical investigation of Bronze Age vitreous materials from the archaeological site of Punta di Zambrone (Calabria, southern Italy). The analyses of a set of samples (9 faience beads, 1 glassy bead) from approximately 1200 BCE (Recent Bronze Age) were carried out with an environmental scanning electron microscope (ESEM) and LA-ICPMS (for the glassy bead) following a non-destructive protocol. Only very small chips of faience were sampled for X-ray powder diffraction (XRPD) and preparation of thin sections for ESEM analysis. The glassy bead is an opaque light-blue silica-soda-lime type with an uncommon chemical composition, comparable to some coeval Italian and Mycenaean glassy faience artefacts. These are called LMLK (low magnesium low potassium) glassy faience, but the flux used for their production has not yet been identified. The trace-element analysis allows exclusion of a Mesopotamian or Egyptian provenance for this sample, suggesting it was produced with rather impure raw materials. The nine faience beads have suffered from extensive weathering. The microstructural examinations carried out with the ESEM enabled definition of three different groups: (1) light beads consisting almost entirely of quartz crystals without any original interparticle glass, which could be due to the heavy weathering; (2) dark beads with a high content of manganese and iron oxide and scarce presence of interparticle glass in the body, suggesting the original presence of Mn/Fe-rich interparticle glass; this presence indicates that a glazing mixture containing alkalis and colorants was mixed with quartz, therefore the efflorescence method could have been used for glazing, in combination with either cementation or application glazing (hybrid glazing methods); and (3) one green sample exhibiting an heterogeneous body rich in Mg, K, Ti, and Fe but not containing Mn. The XRPD analysis of a faience bead of group 1 confirmed the exclusive presence of quartz, whereas for group 2, an additional small peak compatible with Mn oxide (poosibly hausmannite) was observed. Considering the colorant used for the dark beads, the Zambrone faience beads can be compared to Mesopotamian and Minoan faience beads. They belong to a type widespread in north-central Italy between the Middle and Late Bronze Age, and in southern Italy between the Early and Late Bronze Age. The same type of faience is found in the Aegean from the middle of the 3rd millennium BCE to the 12th century BCE.

Mineralogy and Micromorphology Characteristic of Vertisol Lying on Limestone Parent Rocks at Jeneponto District of South Sulawesi Province, Indonesia

The objective of this is paper is to determine the mineralogy and micromorphology characteristics of vertisol in the limestone parent rock at Jeneponto district of South Sulawesi Province, Indonesia. The pedons represent deposits of volcanoes basalt. The study consisted of field and laboratory research. Field research comprises of soil profile descriptions and soil sampling, while laboratory analysis consists of clay minerals analysis using X-rays, as well as sand and rock mineral. Micromorphology analysis undisturbed soil samples were taken from identifiable horizon for thin section preparation. X-ray analysis revealed that clay minerals of the vertisol mainly consists of montmorillonite group. While the mineral composition of parent rock (limestone) generally consists of foraminifera fossil, calcite, dolomite, clay minerals, orthoclase, opaque minerals and quartz. The mineralogy of sand fraction generally consists of easily weathered minerals like pyroxene, feldspar, hornblende, plagioclase, biotite and hard weathered mineral (quartz and opaque). Soil micromorphology analysis revealed that raw material, in general is dominated by coarse material which is consist of quartz mineral mixed with other minerals such as pyroxene and plagioclase. On the other hand, organic coarse-sized components are not found and the microstructure of the soil is generally in the loose form (massive), and the type of soil pore vary from vugh to channels pore.

Improving FTIR imaging speciation of organic compound residues or their degradation products in wall painting samples, by introducing a new thin section preparation strategy based on cyclododecane pre-treatment.

Fourier transform infrared (FTIR) imaging in transmission mode, employing a bidimensional focal plane array (FPA) detector, was applied for the detection and spatially resolved chemical characterisation of organic compounds or their degradation products within the stratigraphy of a critical group of fragments, originating from prehistoric and roman wall paintings, containing a very low concentration of subsisted organic matter or its alteration products. Past analyses using attenuated total reflection (ATR) or reflection FTIR on polished cross sections failed to provide any evidence of any organic material assignable as binding medium of the original painting. In order to improve the method's performance, in the present study, a new method of sample preparation in thin section was developed. The procedure is based on the use of cyclododecane C12H24 as embedding material and a subsequent double-side polishing of the specimen. Such procedure provides samples to be studied in FTIR transmission mode without losing the information on the spatial distribution of the detected materials in the paint stratigraphy. For comparison purposes, the same samples were also studied after opening their stratigraphy with a diamond anvil cell. Both preparation techniques offered high-quality chemical imaging of the decay products of an organic substance, giving clues to the painting technique. In addition, the thin sections resulting from the cyclododecane pre-treatment offered more layer-specific data, as the layer thickness and order remained unaffected, whereas the samples resulting from compression within the diamond cell were slightly deformed; however, since thinner and more homogenous, they provided higher spectral quality in terms of S/N ratio. In summary, the present study illustrates the appropriateness of FTIR imaging in transmission mode associated with a new thin section preparation strategy to detect and localise very low-concentrated organic matter subjected to deterioration processes, when the application of FTIR in reflection mode or FTIR-ATR fails to give any relevant information.

Sorption and distribution of Zn in a sludge-amended soil: influence of the soil clay mineralogy

PurposeConventional pedological survey generally assesses soil metal pollution by comparing total metal concentrations in soil to geochemical baselines in parent rock. This global approach overlooks the sorption capacities of the clay minerals which form at micrometric scale in weathering microsystems and are essential for the behaviour of metals in soil. Therefore, our aim was to investigate the impact of these weathering microsystems and their clay mineralogy upon Zn sorption and distribution throughout a sludge-contaminated soil.Materials and methodsTwo soil profiles with the same diorite parent rock were sampled: (i) an amended soil profile (AS) that received for 10 years wet sewage sludges heavily loaded with Zn and (ii) a control soil profile (CS) free of sludge spreading. Soil samples were carefully collected as undisturbed blocks using plastic core samplers to prevent sample metal contamination. Each sample was further divided into two subsamples: the first was devoted to bulk chemical analyses, mineral grains separation and X-ray diffraction (XRD) analyses, whereas the second part was used for thin-section preparation and electron probe microanalyses (EPMA).Results and discussionZn in the control soil is inherited from the weathering parent rock, whereas it is supplied at the surface of the amended soil by sludges spreading. Each rock-forming mineral weathers into specific clay minerals: amphibole into saponite and montmorillonite and plagioclase into montmorillonite and kaolinite. Each clay mineral, with its specific sorption capacity, controls the Zn distribution within the soil: the smectites produced by the amphiboles have high sorption capacity and favour Zn retention in the upper horizons of the soil; the kaolinites produced by the plagioclases have lower sorption capacity, do not retain Zn in the surface horizons and allow it to migrate to deeper horizons where it is sorbed onto the montmorillonites.ConclusionsThe clay minerals appear to be important soil components controlling the mobility of Zn in the contaminated soils. The micrometric mineralogical approach proves to be relevant to describe the importance of the clay mineral species in the Zn fixation at the solid/solution interface. When applied to a wider range of heavy metals and clay minerals, it could be a useful improvement in the surface complexation modelling used to explain metal cation sorption in soils.

Biostratigraphical and palaeobiogeographical implications of Lower Silurian Radiolaria from black cherts of the Armorican Massif (France)

Abstract. A moderately well-preserved radiolarian assemblage was recovered from organic-rich black chert in a Llandovery (Lower Silurian) sequence that crops out in southern Brittany (Chalonnes-sur-Loire section, Armorican Massif, France). The assemblage is composed of two families (Rotasphaeridae and Haplotaeniatidae), four genera (?Diparvapila, Secuicollacta, Orbiculopylorum, Haplotaeniatum) and 13 species. Some were identified from whole specimens preserved in silica and extracted following dilute hydrofluoric acid processing, while others were recognized in thin-section preparations, as they are beautifully preserved as ‘carbonized’ microfossils. The age range suggested by conodonts and chitinozoans yielded after HF processing from one of the 27 studied samples is in good agreement with the previously published age based on graptolites. The recovered radiolarians are discussed, documented and compared with known Rhuddanian, Aeronian and lower Telychian assemblages in the literature. The stratigraphic ranges are extended for the species Secuicollacta bipola, S. hexactinia, S. parvitesta, Orbiculopylorum granti and O. splendens based on our new data. A significant number of radiolarians found in our samples occur in Llandovery sections from Alaska, Nevada, Arctic Canada and Sweden. These similarities are used to discuss the palaeodistribution of Lower Silurian Radiolaria and our observations support the hypothesis of a wide geographical distribution for these Palaeozoic species.

Synchrotron-based FTIR microspectroscopy for the mapping of photo-oxidation and additives in acrylonitrile–butadiene–styrene model samples and historical objects

Synchrotron-based Fourier transform infrared micro-spectroscopy (SR-μFTIR) was used to map photo-oxidative degradation of acrylonitrile–butadiene–styrene (ABS) and to investigate the presence and the migration of additives in historical samples from important Italian design objects. High resolution (3×3μm2) molecular maps were obtained by FTIR microspectroscopy in transmission mode, using a new method for the preparation of polymer thin sections. The depth of photo-oxidation in samples was evaluated and accompanied by the formation of ketones, aldehydes, esters, and unsaturated carbonyl compounds. This study demonstrates selective surface oxidation and a probable passivation of material against further degradation. In polymer fragments from design objects made of ABS from the 1960s, UV-stabilizers were detected and mapped, and microscopic inclusions of proteinaceous material were identified and mapped for the first time.

Newly defined aberrant crypt foci as a marker for dysplasia in the rat colon.

Dysplasia represents a preneoplastic status in multistep colon carcinogenesis. Whereas laborious preparation of thin sections is required for its diagnosis, we here show that newly defined aberrant crypt foci (ACF) simply mark the majority of the dysplasia on the whole colon. Specifically, decoloring of the azoxymethane-treated rat colon after scoring classical ACF (cACF) resulted in visualization of a subset of aberrant crypts that remained densely stained. They were morphologically classified into three subtypes, of which two with compressed luminal openings proved highly correlated with dysplasia. Accordingly, we designated those foci harboring either of the two crypt subtypes as dysplasia-associated ACF (dACF). By serially applying different detection methods for known preneoplastic lesions to the same colon, we showed that most dACF had already been identified as cACF, and a few newly identified dACF contained an entire population of more advanced lesions, such as flat ACF and mucin-depleted foci. Consequently, integrative scoring of cACF and dACF enabled capture of all early lesions of the colon. Furthermore, 94% of the dACF showed dysplasia and 90% of the dysplastic lesions proved to be dACF. Thus, dACF is a promising marker for dysplasia, likely facilitating precise identification of the early stages of colon carcinogenesis.

Preparation of thin-sections of painting fragments: Classical and innovative strategies

For more than a century, the analyses of painting fragments have been carried out mainly through the preparation of thick resin-embedded cross-sections. Taking into account the development of innovative micro-analytical imaging techniques, alternatives to this standard preparation method are considered. Consequently, dedicated efforts are required to develop preparation protocols limiting the risks of chemical interferences (solubilisation, reduction/oxidation or other reactions) which modify the sample during its preparation, as well as the risks of analytical interferences (overlap of detected signals coming from the sample and from materials used in the preparation). This study focuses particularly on the preparation of thin-sections (1–20μm) for single or combined fourier transform infrared (FTIR) spectroscopy and X-ray 2D micro-analysis. A few strategies specially developed for the μFTIR analysis of painting cross-sections have already been reported and their potential extrapolation to the preparation of thin-sections is discussed. In addition, we propose two new specific methods: (i) the first is based on a free-embedding approach, ensuring a complete chemical and analytical neutrality. It is illustrated through application on polymeric design objects corpus; (ii) the second is based on a barrier coating approach which strengthens the sample and avoids the penetration of the resin into the sample. The barrier coating investigated is a silver chloride salt, an infrared transparent material, which remains malleable and soft after pellet compression, enabling microtoming. This last method was successfully applied to the preparation of a fragment from a gilded Chinese sculpture (15th C.) and was used to unravel a unique complex stratigraphy when combining μFTIR and μXRF.

Thin Sections of Technovit 7100 Resin of Rice Endosperm and Staining

[Abstract] Starch is a biologically and commercially important carbohydrate that is accumulated in plant storage organs, such as seed endosperm. Starch is water-insoluble and forms transparent grains, referred to as starch grains (SGs). SGs are easily stained by iodine solution and can be observed under a normal microscope. Technovit 7100 resin is suitable for preparation of thin sections from endosperm. The thin sections and iodine staining can visualize SGs clearly inside the endosperm cell. This protocol provides the procedures to prepare thin sections of Technovit 7100 resin from rice endosperm. It can also be applicable to the seeds of other plant species.

Plastination and its importance in teaching anatomy. Critical points for long-term preservation of human tissue.

Most medical curricula rely on human bodies for teaching macroscopic anatomy. Over the past 20 years, plastination has become an important means of preservation of organs, for well dissected specimens or for body slices. Here, several critical points regarding body donation with legal and ethical considerations for long-term preservation, the use of cadavers in teaching and the preparation of plastinates as an additional teaching tool will be discussed. Silicone S10 is the gold standard in the preparation of plastinates. An important point to respect is the preparation of specimens, since only very well dissected body parts or excellent tissue sections should be plastinated to show the extraordinary aspects of the human anatomy. The preparation of thin and transparent sections and preservation with P40 polyester provides an additional technique to prepare resistant body slices. A selection of samples prepared by S10 and P40 are shown and compared. In addition, Prussian or Berlin blue staining of brain slices is shown to discriminate better between gray and white matter and demonstrate neuroanatomical structures. These plastinates have been used for many years in teaching first- and second-year medical students and have not lost their appeal. Students and staff appreciate the use of such plastinates. One of the advantages is that their use is not restricted to the dissection hall; slices and body parts can be used in any lecture room or in small group teaching. Therefore, ethical and legal questions need to be addressed regarding their specific use. Plastinates do not replace the traditional dissection courses, since students learn best the anatomical features of a given region by hands-on dissection and by exploratory anatomy. Furthermore, plastinates are more rigid and do not allow demonstration of hidden structures; they also become more cumbersome for endoscopy or are too rigid for demonstrating mechanical features of joints. However, although not a replacement for traditional dissections, plastination provides an additional tool for long-term preservation and for teaching human anatomy.

Development of a thin section device for space exploration: Overview and system performance estimates

In this paper we present a conceptual design of a spaceborne instrument for the in situ production of rock thin sections on planetary surfaces. The in situ Automated Rock Thin Section Instrument (IS-ARTS) conceptual design demonstrates that the in situ production of thin sections on a planetary body is a plausible new instrument capability for future planetary exploration. Thin section analysis would reduce much ambiguity in the geological history of a sampled site that is present with instruments currently flown. The technical challenge of producing a thin section device compatible with the spacecraft environment is formidable and has been thought too technically difficult to be practical. Terrestrial thin section preparation requires a skilled petrographist, several preparation instruments that individually exceed typical spacecraft mass and power limits, and consumable materials that are not easily compatible with spaceflight. In two companion papers we present research and development work used to constrain the capabilities of IS-ARTS in the technical space compatible with the spacecraft environment. For the design configuration shown we conclude that a device can be constructed that is capable of 50 sample preparations over a 2year lifespan with mass, power, and volume constraints compatible with current landed Mars mission configurations. The technical requirements of IS-ARTS (mass, power and number of samples produced) depend strongly on the sample mechanical properties, sample processing rate, the sample size and number of samples to be produced.