Thin Section Samples Research Articles

A multiscale study of silty soil structure

SummaryDependency of soil properties on scale is a crucial issue in soil physics. In this paper, fractal approaches are used in two case studies in France and Australia, respectively, to study how measured physical soil properties change with the sample spacing and the scale of observation. At a scale of 10–1000 m (104 to 106 mm), fractals were applied to sample data from a linear transect, while at the 10−6 to 102 mm scale, fractals were applied in two dimensions to analyse both soil micro‐ and macrostructure, based on thin section samples. Porosity was characterized by short‐range spatial variations using sample spacings of 0.5 and 5 m (from the transect data), and a sample spacing of 1 cm (from the thin section analysis). The size of the representative elementary volume (REV) or representative elementary area (REA), required to represent statistically the elementary soil structure, was identified in three ways: (i) by the correlation length of a representative interconnected pore network, (ii) by the upper limit of the non‐linear increase with observation scale of mean porosity (upper limit of the solid mass fractal domain), and (iii) by the non‐linear decrease with observation scale of the coefficient of variation, CV, of mean porosity. Two embedded REAs were identified: the first (0.1–0.4 mm) related to the soil microstructure whereas a second (11–44 mm) related to the soil macrostructure. The solid mass fractal dimensions of the two embedded structural domains showed that hierarchical heterogeneity of soil structure was more pronounced for microstructures than for macrostructures. The mean area ratio of microstructural matrix/total surface and the CV of mean microporosity both scale similarly at observation scales smaller than the REA size. Their scaling exponents were both related to the fractal dimension of microstructural matrix. This preliminary study shows that the theory of fractals applied to soil structures at a specific scale range cannot be directly applied to predict soil physical properties at another scale range. This is because there are different interdependent structuring processes operating at different scales resulting in fractal dimensions being consistent only over particular domain limits.

Calcium–iron–phosphate features in archaeological sediments: characterization through microfocus synchrotron X-ray scattering analyses

The occurrence of amorphous calcium (Ca)–iron (Fe)–phosphate infilling features in thin-section samples from archaeological stratigraphies is increasingly being reported and used in the cultural interpretations of sites. In some contexts, these materials are the product of dissolution and recrystallization of bone material within pores of the soil or sediment matrix. This study uses transmitted microfocus X-ray scattering to characterize and measure features of known cod fish bone (Gadus morhua) materials, and compare them to archaeological samples of amorphous Ca-Fe-phosphate infilling material found in thin section from early fishing community sites. The analyses characterize the structure of these features for the first time, and allow discussion of the diagenetic processes that lead to their formation.

Permeability prediction from thin sections: 3D reconstruction and Lattice‐Boltzmann flow simulation

We present results and methodology for predicting permeability from thin sections. The method consists of two key components–reconstruction of 3D porous media from 2D thin sections, and 3D flow simulation using the Lattice‐Boltzmann (LB) technique. We construct 3D porous media using sequential indicator simulation (SIS), a geostatistical method, with conditional data and input statistical parameters from thin sections. Permeability is then estimated through flow simulation on the reconstructed porous media. The LB flow simulation successfully handles very complex reconstructed 3D pore geometries. Computed permeabilities from seven thin section samples show good agreement with laboratory measurements over a wide range of permeability. We compare our method to one that uses only thin sections without 3D reconstruction. The comparison shows that our method gives better prediction of permeability, and is less sensitive to statistical errors from discrepancy between thin sections and core samples.

Tillage system effects on near-surface soil morphology: observations from the landscape to micro-scale in silt loam soils of southwestern Ontario

Changing soil management practices can affect processes occurring at multiple scales. This paper assesses the influence of no-till (NT) soil management on conventionally tilled (CT) soils at scales from the soil landscape through to the micromorphological in southwestern Ontario, Canada. Soil profiles were sampled in fine increments at three slope positions in agricultural transects under CT and NT management. The NT soils had been under their present management system for 4, 6 and 11 years such that the changes in morphology over time could be assessed. 137 Cs and soil organic matter content were used as indicators of recent morphological change along the landscape and within the pedon. Thin section samples were taken to determine the changes in soil micromorphological properties. The NT soils had increases of soil organic matter in the top 3 cm relative to lower portions of the Ap horizon, while 137 Cs was diluted likely due to casting activity of earthworms. The accumulation of organic matter and the dilution of 137 Cs near the soil surface was proportional to the number of years the soil had been in NT. The CT soils had indications of aggregate instability, surface crust formation and lack of good pedality within soil thin sections. The top 3 cm of the soil surface in the NT soils had a structure indicative of annual additions of organic residue and L. terrestris l. earthworm activity. The near-surface soil layers in NT for 4 and 6 years had evidence of a platy structure which may have been due to compaction and/or freeze–thaw processes. However, the top 3–4 cm of the 11-year NT site had a fine granular structure which should favor crop emergence and growth. Results from image analysis of pore morphology indicated that it takes more than 4 years of NT to develop pores of equivalent diameter from 100 to 1000 μm that are comparable to the pores numbers of this size in the CT counterparts.

Concrete Capillary Porosity as It Relates to Durability of Pavements Built with Alkali-Silica-Reactive Aggregates

Several concrete pavements have been constructed in southwestern Minnesota using aggregates that recently have tested as being potentially deleteriously alkali-silica reactive. Standard ASTM test procedures were used. Most of these pavements fail to meet their design life. However, the rate of deterioration varies. Six pavement sites varying in age and performance were selected for comparison. Alkali-silica gel is present in all six pavements, even in the 36-year-old pavement still in good condition. Similar aggregate types were used for all six pavements. The coarse aggregate was a low-grade metamorphic quartzite, and the fine aggregate was a glacial sand obtained from various local sources. The relative capillary porosity of the concrete paste was examined using fluorescent dye epoxy impregnated with thin-section samples from each pavement site. Preliminary results suggest that the capillary porosity is linked to the durability of the concrete pavement. The best-performing concretes had a homogeneous capillary porosity that was moderate to low, and the poorer-performing concretes had paste with a capillary porosity that varied from high to low.

Upper Jurassic Reef Play, East Texas Basin: An Updated Overview: Part 1-Background and Outboard Trend

This paper is the first part of a two-part update on geologic and geophysical characterization of gas-productive Upper Jurassic carbonate buildups in the Cotton Valley limestone of the East Texas basin. Continued exploration in this play has yielded important new information on the nature, timing, and genesis of the relevant buildup features. This information is crucial to an understanding of existing and future productive trends in the play. Recent drilling and discovery have resulted in the identification of two major fairways: (1) an older, outboard (or downdip) trend existing along the distally steepened portions of the ramp, at present-day depths of 16,000-17,000 ft (4880-5185 m), and (2) a younger, inboard (or updip) trend located along the salt-deformed portion of the Late Jurassic ramp system and lying at depths of 14,100-15,300 ft (4300-4666 m). This paper focuses on the outboard trend, with discussion of the inboard trend reserved for part 2. Both articles present core, thin section, and other sample data, as well as seismic information, that together offer the most comprehensive overview of these buildups yet available.

Infrared Microspectroscopy Mapping Techniques for The Analysis of Cross Sections and As Anon-Destructive Analysis Method for Paint on A Manuscript

Infrared microspectroscopy is useful for characterizing media in very small cross sectionsamples using both transmission and reflection modes of analysis. In a direct comparison of the two methods, reflection techniques produce poorer quality spectra than the transmission methods. However, many of the problems of reflection spectra can be mitigated by looking at the variations that occur between spectra obtained under similar conditions. An excellent venue for such a study is the use of infrared mapping. Mapping studies compare the intensities of absorption bands versus their location in the sample to generate an image of compositional differences in a region. Several examples are shown in this paper for the application of infrared mapping to the determination of components in thin section and cross section samples. The technique for infrared mapping was also used as a direct, nondestructive method for the characterization of colorants and binders on a small painted manuscript leaf. Compared to the paint cross sections, four relatively large areas (1 cm 2 ) were mapped with the infrared microscope then joined together using a mosaic technique.

A Micromorphological Study of Four Neolithic Sites in the Dutch Coastal Provinces

Micromorphological investigations were carried out on four neolithic sites in the Dutch coastal provinces. In 48 thin section samples, 52 individual layers of archaeological sediments were found. Micromorphology enables us to distinguish nine different types of archaeological layers on such sites, on the basis of contents, sedimentary characteristics and texture. The specific characteristics of each of these types of layers can be transformed into interpretation criteria. This allows a better and more detailed interpretation of such layers than can possibly be reached by conventional means.

Microanalysis of oxygen isotopes in insulators by secondary ion mass spectrometry

Microanalyses for oxygen isotopes of insulating samples in polished thin sections have been achieved using a commercially available secondary ion mass spectrometer equipped with an auxiliary high voltage electron flood gun and modified to allow the detection of secondary ions sputtered with initial kinetic energies up to 4500eV. A Cs + primary ion beam enhanced the negative secondary ion signal. Sample charging was controlled by use of the electron gun (impact energy ≈ 3.4 keV). Secondary ions with > 300 eV initial energy sputtered from a range of silicate minerals do not show detectable variations in instrumental fractionation over a range of tens of electronvolts, providing immunity to variations in sample charging. In addition, the interference of 16OH − on 17O − is effectively eliminated from the mass spectrum at these energies, allowing the measurement of all three oxygen isotopes at low mass resolution. Analytical precision is limited by counting statistics and the depth of the sputtered crater to ≈ ±1% (1σ) for 18/16 ratios. If 17/16 ratios are also desired, it is possible to select count times to achieve ≈ ±2% precision for both.

In Situ Analysis in Geological Thin-Sections by Laser Raman Microprobe Spectroscopy: A Cautionary Note

The advent of laser Raman microprobe (LRM) instruments has permitted researchers to analyze minute (≥ 1 μm) phases in situ in their rock matrix. Geologists prefer to study such samples in polished thin-sections (in which a rock wafer is fixed with a mounting medium onto a glass slide and thinned to 30 μm thickness) or in doubly polished unmounted rock wafers (≥30 μm) like those used for microthermometry. There obviously are many advantages to doing in situ LRM analysis: direct observation of the sample grain in its textural and mineralogical context, preservation of the grain for analysis by additional techniques, and lack of physical disruption and possible modification of the grain caused by physical removal from its matrix. However, there are some problems inherent in this application of the LRM technique. This brief communication is a cautionary note about three possible artifacts that may arise during in situ LRM analysis of graphitic material and hydrocarbon fluids in polished rock sections.

Degradation and stabilisation of blue water pipe

Degradation caused by natural and artificial exposure of blue polyethylene water pipe compounds has been studied using thermal, spectroscopic and mechanical testing techniques. The results indicate that whilst thermal properties can be used as an effective quality control tool, deterioration of mechanical properties corresponds rather more with carbonyl index measurements. Samples in thin and thick sections have been studied and differences in behaviour are noted, with thick section samples retaining mechanical (impact) properties even after substantial degradation has occurred. Limitations in the use of artificial exposure to monitor changes that occur during natural weathering are discussed. It is concluded that, in thick section, the surface nature of ultraviolet degradation in the extreme conditions of artificial exposure affects mechanical properties in a different manner than longer-term periods of natural exposure.

Endosymbiosis in the lucinid clams Lucinoma aequizonata, Lucinoma annulata and Lucina floridana: a reexamination of the functional morphology of the gills as bacteria-bearing organs

A three-dimensional representation of the structure of the endosymbiont-containing gills of Lucinoma aequizonata, L. annulata and Lucina floridana was constructed using light and electron microscopy of fresh and plastic-embedded thin-sectioned samples. The gills of these lucinids are identical in overall structure, each being composed of three structurally and functionally distinct regions here called the ctenidial filament zone (CFZ), the transition zone (TZ), and the bacteriocyte zone (BZ). Rather than a simple medial extension of the filament tissue, the bacteriocyte tissue is organized as an array of cylindrical tubes, the walls of which are composed primarily of bacteriocyte cells covered by a thin microvillar epithelium. The physical relationship between the symbionts, the host tissues and the external environment are examined, and structural constraints on the potential functions of bacteria in this host-symbiont system are discussed.

Antibody Probes in the Study of Gap Junctional Communication

Gap junctions are thought to contain intercellular channels, insulated from the extracellular space, that permit direct cell-cell communication via the passage of small molecules. Until recently, the study of gap junctional communication has been based on the detection of gap junctions by electron microscopic analysis of thin section and freeze-fracture samples and on the physiological measurement of radio labeled metabolite transfer (metabolic coupling), fluores­ cent dye transfer (dye coupling), and ion movement (electrical coupling) between adjacent cells. Although several effectors that regulate gap junctional conductance have been identified with this approach (3, 12, 47, 51, 55,57, 63), it is not known whether they influence the gap junction polypeptide(s). In the absence of specific probes for these polypeptides, it has proven difficult to examine these mechanisms, gap junction biogenesis, and the various roles that have been suggested for gap junctional communication in normal and patholog­ ical tissues (for reviews see 6, 31, 37, 38, 48). The focus of this review is to describe the recent progress made in using immunological probes to analyze gap junction-mediated cell-cell communica­ tion in vivo and in vitro.

Variations in the composition and dielectric properties of barrier anodic coatings observed in conjunction with variations in cell voltage and field conditions

We have observed the dielectric, morphological and compositional properties of barrier anodic coatings which form on an aluminum alloy. Anodization cell potentials from 80 to 950 V and two different current density schedules were studied. Our results indicate that substantial amounts of electrolyte byproducts become incorporated in the coatings. The ratio of the concentration of these byproducts to that of aluminum oxide increases with cell voltage. Higher concentrations of these byproducts are found near the exterior surfaces of the coatings than are found in regions near the coating-substrate interface. Coatings grown following a sequence of conditions of fixed current density and cell voltage contain higher concentrations of electrolyte byproducts than coatings grown under fixed current density conditions only. Thin section samples heated in situ in a transmission electron microscope exhibit a slower rate of crystallization in regions containing higher concentrations of electrolyte byproducts. It is generally believed that there is an inverse correlation between the ease with which a barrier anodic coating crystallizes and its dielectric merit. The properties displayed by our coatings tend to support this hypothesis.

TEM Cross Section Sample Preparation Technique for III–V Compound Semiconductor Device Materials by Chemical Thinning

A cross section sample preparation technique is described for the TEM studies of III–V compound semiconductor device materials. In this technique, a grid‐masking method is introduced for selective‐area perforation using chemical etching. By epoxy bonding a TEM specimen grid onto the surface of a face‐to‐face or face‐to‐back epoxy‐bonded thin cross section sample stack, perforations by chemical etching are confined to the regions inside the meshes. Selective‐area perforation can easily be achieved by accurately positioning the masking grid and monitoring the perforation under a microscope. Since many perforations can be made in the selected area, the chance of obtaining a cross section sample containing the device structure is greatly increased. Furthermore, the masking grid mechanically reinforces the perforated sample and hence eliminates problems associated with sample handling. Examples of the use of this technique for single‐layer and , multilayer laser device structures, grown by vapor‐phase epitaxy, are demonstrated. The technique is also applicable to multilayer structures, and, in addition, greatly facilitates the selective‐area perforation of plan‐view TEM samples.

The macromolecular states of solvent-swollen and dry coal

Improved understanding of the physical state of coal is needed to better characterize, modify and utilize this abundant source of energy. In spite of extensive research in this area for well over half a century, the level of understanding has been poor. Here, new substantive evidence clarifying the macromolecular states of coal is presented. The approach involved studying changes in the optical anisotropy of raw and solvent-swollen thin section samples of a bituminous coal. It was found that the natural optical anisotropy was completely relaxed on immersion of the coal in pyridine. From changes in the optical anisotropy induced by pressure, the solvent-swollen coal was determined to be a cross-linked rubber and its macromolecular chain segments were found to have substantial mobility. It appears that pyridine and some other good swelling agents relax essentially all of the secondary bonding in the coal. On the other hand, raw coal and coal immersed in water, various hydrocarbon solvents and other poor swelling agents were determined to be macromolecular plastics.

Thylakoid degradation during photooxidative bleaching of the cyanobacteriumAnacystis nidulans

Photooxidative bleaching of the CyanobacteriumAnacystis nidulans was studied by electron microscopic investigation of both freezefractured and thin-sectioned samples. During bleaching four consecutive phases in degradation of photosynthetic membranes (thylakoids) could be characterized: 1. No ultrastructural changes until photosystem II activity is lost. 2. Derangement of characteristic arrangement of thylakoids. 3. Thylakoids visible only in thin-sectioned but not in freeze-fractured samples. 4. Completely bleached cells, only traces in place of former thylakoids visible in thinsectioned samples. Bleaching did not cause lysis of the cells showing that the cytoplasmic membrane was not damaged. Polyhedral bodies also were still detectable in bleached cells.

Structure and composition of resistant layers in bacterial spore coats.

SUMMARY: Treatment with mercaptoethanol caused spores of various bacteria to become sensitive to lysis by lysozyme, a spore enzyme and hydrogen peroxide; further treatment with alkali caused greater sensitization to these lytic agents. Alkali removed a protein from the outer coats of mercaptoethanol-treated spores. The protein from Bacillus cereus, B. coagulans and Clostridium sporogenes contained high levels of acidic and basic amino acids; that from B. coagulans contained a high proportion (over 7% of its residues) of tyrosine. Electron microscopy of thin section and freeze-etch samples showed that the alkali-soluble protein contributed to a striking banding pattern containing 57 Å spaced fibres on the outer surface of B. coagulans spores. This layer may function as a protection against the enzymes of potential predators.