scholarly journals The Colors of the Circus Mosaic from Barcino (Roman Barcelona): Characterization, Provenance, and Technology Issues

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 746
Author(s):  
Lluís Casas ◽  
Roberta Di Febo ◽  
Carme Boix ◽  
Albert Egea ◽  
Oriol Vallcorba ◽  
...  
Keyword(s):  
Polarized Light ◽  
Early Eocene ◽  
White Marble ◽  
Thin Sections ◽  
Electron Microscopies ◽  
Concurrent Use ◽  
Production Technologies ◽  
Archaeological Knowledge ◽  
Apuan Alps ◽  
Ne Spain

Archaeometric studies on mosaics often concentrate only on glass tesserae, while comprehensive studies including both stone and glass tesserae are scarce; however, both types of tesserae can sometimes bring relevant data to elaborate archaeological knowledge on a studied mosaic. In this paper, a representative set of tesserae from a large polychrome Roman mosaic retrieved in Barcelona (NE Spain) is investigated using various methods. Most of the techniques were directly applied on samples prepared as petrographic thin sections (including polarized-light, cathodoluminescence and electron microscopies, and synchrotron through-the-substrate μX-ray diffraction). The results indicate that, from the ten sampled stone tesserae, there are (i) seven limestones, one of them identified as Alveolina limestone (early Eocene) from the southern Pyrenees (ii) two sandstones from Barcelona’s Montjuïc hill (Miocene) and, (iii) a Carrara white marble from the Apuan Alps (Italy). The profuse presence of tesserae of both local and imported materials with well-known uses in architecture, epigraphy, and sculpture could imply that tesserae were a by-product of their main use. Two different production technologies were identified for the three sampled glass tesserae. The concurrent use of antimony- and tin-based opacifiers is in agreement with the accepted archaeological chronology of the mosaic (4th century AD).

scholarly journals PHOTORECEPTOR STRUCTURES

1957 ◽  
Vol 3 (3) ◽  
pp. 441-448 ◽  
Author(s):  
J. J. Wolken ◽  
J. Capenos ◽  
A. Turano
Keyword(s):  
Electron Microscopy ◽  
Polarized Light ◽  
Plant Cells ◽  
House Fly ◽  
Structural Detail ◽  
Thin Sections ◽  
Retinal Rods ◽  
Single Structure ◽  
Vertebrate Eye ◽  
Insect Eye

The eyes of three eye mutants of Drosophila melanogaster were fixed and thin sections studied for its structural detail in the electron microscope. Each ommatidium was found to have seven retinula cells with an equal number of rhabdomeres (visual units). The rhabdomeres average 1.2 µ in diameter and 60 µ in length. Each rhabdomere consists of osmium-fixed dense bands averaging 120 A in thickness, and with less dense interspaces 200 to 400 A. There is an average of 23 dense bands or 46 interfaces per micron within the rhabdomere. The rhabdomere as we have presented it is a single structure of packed rods or tubes. The "fine structure" within the rhabdomere is similar to that observed by electron microscopy for the retinula of the house fly, and to the retinal rods of the vertebrate eye, and to the chloroplasts of plant cells in a variety of animal and plant photoreceptor structures. In addition, the radial arrangements within the ommatidium of radially unsymmetrical units, the rhabdomeres, is probably related to the analysis of polarized light in the insect eye.

scholarly journals Process Induced Skin-Core Morphology in Injection Molded Polyamide 66

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 894
Author(s):  
Yvonne Spoerer ◽  
René Androsch ◽  
Dieter Jehnichen ◽  
Ines Kuehnert
Keyword(s):  
Polarized Light ◽  
Skin Layer ◽  
Crystalline Morphology ◽  
Polyamide 66 ◽  
Thin Sections ◽  
X Ray ◽  
X Ray Scattering ◽  
Order Of Magnitude ◽  
Injection Molded ◽  
Ray Scattering

Polyamide 66 (PA 66) was injection-molded to obtain samples with a structure gradient between skin and core, as it was revealed by analysis of the semi-crystalline morphology using polarized-light optical microscopy (POM). Wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) were employed to characterize thin sections with a thickness in the order of magnitude of 50 µm, allowing detection of crystals of different perfection, as a function of the distance from the surface. It was found that the transparent and non-spherulitic skin layer contains rather imperfect α-crystals while the perfection of α-crystals continuously increases with extending distance from the surface. Since variation of the molding conditions allows tailoring the skin-core morphology, the present study was performed to suggest a reliable route to map the presence of specific semi-crystalline morphologies in such samples.

The swelling of Na-montmorillonite due to water absorption

Soil Research ◽  
1963 ◽  
Vol 1 (2) ◽  
pp. 129 ◽  
Author(s):  
WW Emerson
Keyword(s):  
Sodium Hydroxide ◽  
Lithium Chloride ◽  
Lithium Treatment ◽  
Polarized Light ◽  
Specific Effect ◽  
Sodium Pyrophosphate ◽  
Thin Sections ◽  
Saturated Water ◽  
The Stability ◽  
Neutral Sodium

Orientated flakes of dry Na-montmorillonite were brought into equilibrium successively with relative vapour pressures of 0.92 and 0.985 and the moisture contents, (001) spacings, and swelling measured, the latter with a travelling microscope. Over saturated water vapour the clay continued to swell with time, in contrast to Ca-montmorillonite. Hysteresis in swelling was only observed at values of p/po > 0.985. The further expansion of flakes when immersed in solutions, N in Na+, of sodium chloride with dilute buffer added (from pH 4.4 to 10) or sodium hydroxide or chloride plus neutral sodium pyrophosphate was determined. The Na+ concentration was then reduced and the corresponding swelling measured, until the flake dispersed. Similar experiments were made on orientated flakes prepared from Na-montmorillonite to which 1.5% cetyltrimethylarnmonium bromide (CTAB) had been added, as well as from Na-montmorillonite which had been washed with lithium chloride and heated before reconversion to the Na form. The expansion of Li-vermiculite crystals in lithium chloride solutions was also determined. In solutions N in Na+ the swelling of Na-montmorillonite flakes was independent of pH, but for Na+ < N/2 the swelling increased sharply above pH 8.0. The swelling of Na-clay + CTAB was much less than untreated clay and was independent of pH. Na-montmorillonite which had been lithium-treated at 95�C gave a swelling pattern at pH 4.4 similar to that of Na-clay + CTAB, whereas in sodium hydroxide the pattern was similar to that of untreated clay. The specific effect of the pyrophosphate anion on the swelling of the CTAB-treated clay was slight. There was marked hysteresis in the swelling of Na-montmorillonite with respect to salt concentration, whereas the swelling of Li-vermiculite was almost reversible. Adding CTAB inhibited the intercrystalline swelling of Na-montmorillonite, the CTA+ ions forming Stern layers on the external surfaces of the crystals. A similar effect was apparently produced in the acetate buffer by aluminium ions released during the lithium treatment. The increase in the swelling of the untreated clay with pH is consistent with the removal of aluminium ions from the external surfaces of the crystals. There must be residual attractive forces between the crystal at high pH to account for the stability of the clay in dilute salt solutions. The edge to face forces linking the silicate sheets together appear to be constant above pH 4.0. Neutral sodium pyrophosphate disperses the clay at Na+ concentrations of < N Na+ by removing aluminium ions and neutralizing positive edge charges. The montmorillonite crystals are considered to be linked mainly edge to edge in a tactoid. The bands observed in thin sections of expanded gels, using polarized light, may be due to a periodicity in the stacking of the silicate sheets forming the crystals.

Formation of wide-blocky calcite veins by extreme growth competition

2020 ◽  
pp. jgs2020-104
Author(s):  
Liene Spruženiece ◽  
Michael Späth ◽  
Janos L. Urai ◽  
Estibalitz Ukar ◽  
Michael Selzer ◽  
...  
Keyword(s):  
High Resolution ◽  
Growth Rates ◽  
Polarized Light ◽  
Wall Rock ◽  
Scattered Electron ◽  
Thin Sections ◽  
Content Type ◽  
Calcite Veins ◽  
Supplementary Material ◽  
Electron Back Scattered Diffraction

Liassic limestones on the coast of Somerset in the UK contain dense arrays of calcite microveins with a common, but poorly understood microstructure, characterized by laterally wide crystals that form bridges across the vein. We investigated the mechanisms of formation and evolution of these ‘wide-blocky’ vein microstructures using a combination of high-resolution analytical methods, including virtual petrography, optical cathodoluminescence and scanning electron microscopy techniques (e.g. energy-dispersive X-ray spectrometry, back-scattered electron imaging, cathodoluminescence and electron back-scattered diffraction), laboratory experiments and multiphase field modelling. Our results indicate that the studied veins formed in open, fluid-filled fractures, each in a single opening and sealing episode. As shown by the optical and electron back-scattered diffraction images, the vein crystals grew epitaxially on grains of the wall rock and we hypothesize that their growth rates differed depending on whether the crystals were on a wall rock grain substrate that fractured intergranularly (slow growth rates) or transgranularly (rapid growth rates). Our multiphase field models support this hypothesis, showing that wide, blocky crystals only form where there are significant differences in the growth rate and are dependent on the type of seed grain. These results provide strong evidence for extreme growth competition, a process that we propose controls vein-filling in many micritic carbonate reservoirs, as well as demonstrate that the characteristics of the fracture wall can affect the filling processes in syntaxial veins.Supplementary material: The description and images of the studied thin sections are available at https://doi.org/10.6084/m9.figshare.c.5172371. High-resolution optical microscopy mosaics (under plane-polarized- and crossed polarized light) of the thin section collection in PetroScan file format are available on request from the authors.

Integration of geophysical methods and fractures study for the Vallès geothermal system characterization (NE Spain)

2020 ◽  
Author(s):  
Gemma Mitjanas ◽  
Juanjo Ledo ◽  
Pilar Queralt ◽  
Gemma Alías ◽  
Perla Piña ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Geophysical Methods ◽  
Normal Fault ◽  
Hot Water ◽  
Fault System ◽  
Geothermal System ◽  
Thin Sections ◽  
Main Structure ◽  
Geological Map ◽  
Ne Spain

&lt;p&gt;The Vall&amp;#232;s geothermal system is located in the Catalan Coastal Ranges (CCR) (NE Spain). The CCR are formed by horst and graben structures limited by NE-SW and ENE-WSW striking normal faults, developed during the opening of the Valencia Trough (northwestern Mediterranean) (Gaspar-Escribano et al., 2004). In the Vall&amp;#232;s Basin area, the thermal anomaly is located in the northeastern horst-graben limit, where a highly fractured Hercynian granodiorite is in contact with Miocene rocks by a major normal fault. This main structure seems to control the heat and the hot-water flow, nevertheless, the geological structure of this area, as well as the role of the Vall&amp;#232;s normal fault, is poorly understood.&lt;/p&gt;&lt;p&gt;Magnetotellurics and gravity methods together with a detailed geological map have been applied in this area to understand the main structure. Although the geophysical part makes up most of the study, we are also elaborating a detailed geological map of the area, making a fractures study at different scales. We are working with DEM alignments analysis, and fractures study from outcrops and thin sections.&lt;/p&gt;&lt;p&gt;Our preliminary results in gravity show a strong gravity gradient in the NE-SW Vall&amp;#232;s half-graben system and the recent MT profiles image the main fault of that system (Vall&amp;#232;s normal fault). These results show a basin geometry with the major thickness of the basin towards the depocenter, disagreeing with the roll-over geometry assumed in previous works.&lt;/p&gt;&lt;p&gt;Interpretations of the fractures study, together with geophysical data and models, have allowed a preliminary characterization of damage zones associated with the fault system, which are directly related to the fluid flow and the hot springs. The nature of this damage zones could be related to relay ramps, commonly regarded as efficient conduits for fluid flow (Fossen and Rotevatn, 2016).&lt;/p&gt;

scholarly journals Diagenetic evolution of fault zones in Urgonian microporous carbonates, impact on reservoir properties (Provence – southeast France)

Solid Earth ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 1163-1186
Author(s):  
Irène Aubert ◽  
Philippe Léonide ◽  
Juliette Lamarche ◽  
Roland Salardon
Keyword(s):  
Polarized Light ◽  
Fault Zones ◽  
Reservoir Properties ◽  
Thin Sections ◽  
Stable Isotopic ◽  
Calcite Cementation ◽  
Diagenetic Evolution ◽  
The Impact ◽  
Isotopic Measurements ◽  
Δ13c And Δ18o

Abstract. Microporous carbonate rocks form important reservoirs with permeability variability depending on sedimentary, structural, and diagenetic factors. Carbonates are very sensitive to fluid–rock interactions that lead to secondary diagenetic processes like cementation and dissolution capable of modifying the reservoir properties. Focusing on fault-related diagenesis, the aim of this study is to identify the impact of the fault zone on reservoir quality. This contribution focuses on two fault zones east of La Fare anticline (SE France) crosscutting Urgonian microporous carbonates. Overall, 122 collected samples along four transects orthogonal to fault strike were analyzed. Porosity values have been measured on 92 dry plugs. Diagenetic elements were determined through the observation of 92 thin sections using polarized light microscopy, cathodoluminescence, carbonate staining, SEM, and stable isotopic measurements (δ13C and δ18O). Eight different calcite cementation stages and two micrite micro-fabrics were identified. As a main result, this study highlights that the two fault zones acted as drains canalizing low-temperature fluids at their onset and induced calcite cementation, which strongly altered and modified the local reservoir properties.

scholarly journals Application of Image Analysis for the Identification of Prehistoric Ceramic Production Technologies in the North Caucasus (Russia, Bronze/Iron Age)

Heritage ◽  
2019 ◽  
Vol 2 (3) ◽  
pp. 2327-2342 ◽  
Author(s):  
Ki Suk Park ◽  
Ralf Milke ◽  
Erik Rybacki ◽  
Sabine Reinhold
Keyword(s):  
Image Analysis ◽  
Bronze Age ◽  
Iron Age ◽  
Polarized Light ◽  
Data Availability ◽  
Ceramic Production ◽  
North Caucasus ◽  
Archaeological Ceramics ◽  
The North ◽  
Production Technologies

The recent advances in microscopy and scanning techniques enabled the image analysis of archaeological objects in a high resolution. From the direct measurements in images, shapes and related parameters of the structural elements of interest can be derived. In this study, image analysis in 2D/3D is applied to archaeological ceramics, in order to obtain clues about the ceramic pastes, firing and shaping techniques. Images were acquired by the polarized light microscope, scanning electron microscopy (SEM) and 3D micro X-ray computed tomography (µ-CT) and segmented using Matlab. 70 ceramic sherds excavated at Ransyrt 1 (Middle-Late Bronze Age) and Kabardinka 2 (late Bronze–early Iron Age), located in in the North Caucasian mountains, Russia, were investigated. The size distribution, circularity and sphericity of sand grains in the ceramics show site specific difference as well as variations within a site. The sphericity, surface area, volume and Euler characteristic of pores show the existence of various pyrometamorphic states between the ceramics and within a ceramic. Using alignments of pores and grains, similar pottery shaping techniques are identified for both sites. These results show that the image analysis of archaeological ceramics can provide detailed information about the prehistoric ceramic production technologies with fast data availability.

Investigating the internal lithological structure and rock magnetic signature of Heinrich Event layers at SE Grand Banks Slope, Newfoundland

2021 ◽  
Author(s):  
Shettima Bukar ◽  
Tilo von Dobeneck ◽  
Frank Lisker
Keyword(s):  
North Atlantic Ocean ◽  
Ice Sheet ◽  
Polarized Light ◽  
Laurentide Ice Sheet ◽  
Magnetic Minerals ◽  
Thin Sections ◽  
Grand Banks ◽  
Rock Types ◽  
Heinrich Event ◽  
Event Layers

&lt;p&gt;Periodic mass discharges of icebergs from the Laurentide ice-sheet into the North Atlantic Ocean during the last glacial period deposited abundant ice-rafted detritus (IRD) accumulated in sequences of typically six major Heinrich Event layers, each with some tens of cm thickness, at all eastern slopes of the Grand Banks submarine platform of Newfoundland. Compositionally, it is well established that these IRD layers consist of varied rock contents emanating from distinct, but not yet clearly defined bedrock provinces of the Canadian Shield. The, most prominently reported constituent is detrital dolomite, but the entire lithological range of the IRD is much broader. Rock magnetic records, e.g. magnetic susceptibility logs of SE Grand Banks cores, therefore depict complex and partly repeating internal substructures across the Heinrich Event layers owing to distinct successions in IRD lithology over the course of every mass calving event.&lt;/p&gt;&lt;p&gt;We investigated IRD sieve fractions (1mm &amp;#8211; 4cm) of the entire glacial section (550&amp;#8211;1054 cm) of SE Grand Banks slope gravity core GeoB&amp;#160;18530-1, sampled in 2.3&amp;#160;cm steps. Therefrom, we identified and classified distinct IRD rock types as well as monocrystalline rock-forming mineral particles, for which we established so far 24 well-defined lithological categories of sedimentary, igneous and metamorphic origin. This initial identification of IRD lithology was performed based on all available visual criteria including texture (crystallinity, grain-size), color and translucency (mineralogy), hardness and surface structures (e.g., cleavage) using a binocular microscope. This rock type classification is now being substantiated by polarized light microscopy of exemplary thin sections created from larger IRD clasts.&lt;/p&gt;&lt;p&gt;To established cumulative rock magnetic fingerprints of all IRD magnetic mineral assemblages, isothermal remanent magnetization acquisition curves of all sieve fractions as well as individual specimens of all the classified rock types have been measured. These records systematically revealed higher concentrations of magnetic minerals at the tops and bottoms of most Heinrich Event layers and also clear variations in coercivity spectra. This finding is mirrored by the IRD rock count records, where magmatic rock types predominate mostly at Heinrich Event layer boundaries. Preferred deposition of these IRD rock types during the initiation and ending of events and their variation from older to younger events,- highlight repetitive patterns in the cyclic Laurentide ice-sheet collapses to be further explored.&lt;/p&gt;

scholarly journals In situ ATR-IR spectroscopic and electron microscopic analyses of settlement secretions of Undaria pinnatifida kelp spores

2010 ◽  
Vol 8 (56) ◽  
pp. 410-422 ◽  
Author(s):  
L. Petrone ◽  
R. Easingwood ◽  
M. F. Barker ◽  
A. J. McQuillan
Keyword(s):  
Ir Spectroscopy ◽  
Sea Water ◽  
Undaria Pinnatifida ◽  
Bulk Material ◽  
Attenuated Total Reflection ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Electron Microscopies ◽  
Anionic Polysaccharides

Knowledge about the settlement of marine organisms on substrates is important for the development of environmentally benign new methods for control of marine biofouling. The adhesion to substrates by spores of Undaria pinnatifida , a kelp species that is invasive to several countries, was studied by scanning electron and transmission electron microscopies (SEM/TEM) as well as by in situ attenuated total reflection infrared (ATR-IR) spectroscopy. The IR spectra showed that adhesive secretion began approximately 15 min after initial settlement and that the adhesive bulk material contained protein and anionic polysaccharides. Energy dispersive X-ray microanalysis of the adhesive identified sulphur and phosphorus as well as calcium and magnesium ions, which facilitate the gelation of the anionic polysaccharides in the sea water. The adhesive may be secreted from Golgi bodies in the spore, which were imaged by TEM of spore thin sections. Additionally, an in situ settlement study on TiO 2 particle film by ATR-IR spectroscopy revealed the presence of phosphorylated moieties directly binding the substrate. The presence of anionic groups dominating the adhesive suggests that inhibition of spore adhesion will be favoured by negatively charged surfaces.

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