Pressure Scanning Research Articles

Strain rate effect on dynamic mechanical properties and microstructure of cemented tailings composites

The dynamic mechanical properties of the cemented tailings composites (CTC) is one of the major technical challenges in the mining engineering field. In this paper, the Split Hopkinson Pressure Bar (SHPB) impact loading and scanning electron microscopy (SEM) system were conducted to investigate the average strain rate (ASR) rate on the dynamic compressive strength (DCS), microstructure fractal dimension and failure pattern of the CTC specimens. The result shows that the DCS of the CTC increased exponentially with the increase of ASR value when the ASR was in the range of 10–100 s−1. The main hydrate productions of CTC are C-S-H and AFt. The pore size of CTC increased with increased ASR. The fractal dimension of the pore area increased linearly with increased ASR. According to the above results, it provides a reference for engineers of mine sites to reduce the blasting impact load utilizing discontinuous charging and differential detonation, thus achieving the goal of reducing the dilution rate of underground mining.

Copper and Melanin Play a Role in Myxococcus xanthus Predation on Sinorhizobium meliloti.

Myxococcus xanthus is a soil myxobacterium that exhibits a complex lifecycle with two multicellular stages: cooperative predation and development. During predation, myxobacterial cells produce a wide variety of secondary metabolites and hydrolytic enzymes to kill and consume the prey. It is known that eukaryotic predators, such as ameba and macrophages, introduce copper and other metals into the phagosomes to kill their prey by oxidative stress. However, the role of metals in bacterial predation has not yet been established. In this work, we have addressed the role of copper during predation of M. xanthus on Sinorhizobium meliloti. The use of biosensors, variable pressure scanning electron microscopy, high-resolution scanning transmission electron microscopy, and energy dispersive X ray analysis has revealed that copper accumulates in the region where predator and prey collide. This accumulation of metal up-regulates the expression of several mechanisms involved in copper detoxification in the predator (the P1B-ATPase CopA, the multicopper oxidase CuoA and the tripartite pump Cus2), and the production by the prey of copper-inducible melanin, which is a polymer with the ability to protect cells from oxidative stress. We have identified two genes in S. meliloti (encoding a tyrosinase and a multicopper oxidase) that participate in the biosynthesis of melanin. Analysis of prey survivability in the co-culture of M. xanthus and a mutant of S. meliloti in which the two genes involved in melanin biosynthesis have been deleted has revealed that this mutant is more sensitive to predation than the wild-type strain. These results indicate that copper plays a role in bacterial predation and that melanin is used by the prey to defend itself from the predator. Taking into consideration that S. meliloti is a nitrogen-fixing bacterium in symbiosis with legumes that coexists in soils with M. xanthus and that copper is a common metal found in this habitat as a consequence of several human activities, these results provide clear evidence that the accumulation of this metal in the soil may influence the microbial ecosystems by affecting bacterial predatory activities.

Pedogenic information from fine sand: A study in Mediterranean soils

AbstractThe fine sand fraction (50–250 μm) of Mediterranean soils from southern Spain provides valuable information on soil genesis and the origin of their parent materials. This study considers the whole fine sand and heavy fine sand (ρ > 2.82 g cm−3) of Luvisols, Calcisols and Fluvisols, which form a chronosequence (ages from 600 to 0.3 ka) of the River Guadalquivir terrace system. Advanced techniques (X‐ray diffraction, inductively coupled plasma mass spectrometry, inductively coupled plasma atomic emission spectroscopy, variable pressure scanning electron microscope with an energy dispersive X‐ray spectroscopy system and Raman analysis) were employed. Inheritance is the principal pedogenic process. The whole fine sand consisted of carbonates (calcite and dolomite), tectosilicates (quartz, K‐feldspar and plagioclases), phyllosilicates (illite/moscovite, biotite, Na‐mica, chlorite, kaolinite, interstratified vermiculite‐chlorite, vermiculite‐illite and smectite‐illite) and iron oxides (goethite and haematite). The minor minerals (rutile, anatase, ilmenite, zircon, staurolite, monazite, barite, apatite, andalusite, garnet and titanite) are concentrated, also through inheritance, in the heavy fine sand. However, there is also substantiated evidence for neoformation of rutile in these soils, never reported previously. In addition, we report that (a) the geochemical indices calculated in fine sand (SiO2/CaO, Chemical Index of Weathering (CIW), Weathering Index of Parker (WIP), Weathering Index (WI), Base Depletion Index (BDI), Weathering Ratio (WR) and Sr/Zr) are closely related to soil age, allowing chronofunctions to be established, and (b) geochemical indices provide information on the origin of soils and permit the establishment of a “critical point” corresponding to “time zero;” that is, the start of pedogenic alteration of the parent material.Highlights Mineralogy and geochemistry inform on the provenance of the fine sand Rutile is neoformed in the fine sand and co‐exists with the polymorph anatase The properties of the fine sand including geochemical indexes fit chronofunctions Geochemical indices determine a “critical point” related to the start of weathering

Effect of processing parameters on forming defects during selective laser melting of AlSi10Mg powder

PurposeTo fabricate a selective laser melting (SLM)-processed AlSi10Mg part with almost full density and free of any apparent pores, this study aims to investigate the effect of ambient argon pressure and laser scanning speed on the particles splash during the AlSi10Mg powder bed laser melting.Design/methodology/approachBased on the discrete element method (DEM), a 3D model of random distribution of powder particles was established, and the 3D free surface of SLM forming process was dynamically tracked by the volume of fluid, where a Gaussian laser beam acts as the energy source melting the powder bed. Through the numerical simulation and process experimental research, the effect of the applied laser power and scanning speed on the operating laser melting temperature was studied.FindingsThe process stability has a fundamental role in the porosity formation, which is process-dependent. The effect of the processing conditions on the process stability and the resultant forming defects were clarified.Research limitations/implicationsThe results shows that the pores were the main defects present in the SLM-processed AlSi10Mg sample, which decreases the densification level of the sample.Practical implicationsThe optimal processing parameters (argon pressure of 1,000 Pa, laser power of 180 W, scan speed of 1,000 mm/s, powder layer thickness of 35 µm and hatch spacing of 50 µm ) applied during laser melting can improve the quality of selective laser melting of AlSi10Mg,Social implicationsIt can provide a technological support for 3D printing.Originality/valueBased on the analysis of the pore and balling formation mechanisms, the optimal processing parameters have been obtained, which were argon pressure of 1,000 Pa, laser power of 180 W, scan speed of 1,000 mm/s, powder layer thickness of 35 µm and hatch spacing of 50 µm. Then, a near-fully dense sample free of any apparent pores on the cross-sectional microstructure was produced by SLM, wherein the relative density of the as-built samples is larger than 97.5%.

Wettability and pre-osteoblastic behavior evaluations of a dense bovine hydroxyapatite ceramics.

In this study, the wettability, cell viability, and roughness of an experimental dense bovine hydroxyapatite [Ca10(PO4)6(OH)2] ceramic block were evaluated so that, in the future, it could be used as a base material for dental implants. The results to commercial zirconia and a commercially pure titanium (Ti) alloy were compared. The surface roughness and contact angles were measured. An in vitro evaluation was conducted by means of tests in which pre-osteoblastic MC3T3-E1 cells were placed in indirect and direct contact with these materials. For cell viability, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and crystal violet test were conducted. A qualitative analysis was conducted using variable pressure scanning electron microscopy (SEM). No statistically significant differences were observed in wettability and roughness tests among the groups. In both the MTT assay and crystal violet test, all groups demonstrated satisfactory results without cytotoxicity. SEM showed cell adhesion and cell proliferation results on the material surfaces after 24 h and 48 h. In conclusion, this dense Ca10 (PO4)6(OH)2 ceramic can be considered as a potential biocompatible material.

Interconnected macropores cryogel with nano-thin crosslinked network regenerated cellulose

Dissolved oil palm empty fruit bunch cellulose (EFBC) and sodium carboxymethylcellulose (NaCMC) were chemically crosslinked with epichlorohydrin (ECH) to generate designated hydrogel. After swelling process in distilled water, the swollen hydrogel was frozen and freeze-dried to form cryogel. The swelling phenomenon of hydrogel during the absorption process gave substantial effects on thinning of crosslinked network wall, pore size and volume, steadiness of cryogel skeletal structure, and re-swelling of cryogel. The swelling effects on hydrogel were confirmed via microscopic study using variable pressure scanning electron microscope (VPSEM). From the retrieved VPSEM images, nano-thin crosslinked network wall of 24.31 ± 1.97 nm and interconnected pores were observed. As a result, the amount of water, the swelling degree, and the freeze-drying process indirectly affected the VPSEM images that indicated pore size and volume, formation of interconnected pores, and re-swelling of cryogel. This study determined the intertwined factors that affected both hydrogel and cryogel properties by investigating the swelling phenomenon and its ensuing effects.

Determining the provenance of the European glass beads of Lumbu (Mbanza Kongo, Angola)

A collection of glass beads found in Lumbu (Mbanza Kongo, Angola) were analyzed by means of a multi-analytical minimally invasive methodology, which included handheld X-ray fluorescence (hXRF), variable pressure scanning electron microscope coupled with energy dispersive X-ray spectrometry (VP-SEM-EDS), micro-Raman spectroscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).Trace element analysis, and rare earth element pattern analysis in particular, was found to be essential to establish the provenance of the European trade beads in this study. The glass beads from types 30, 31, 32, 36, 38, 39, 40, 41, 42, 43 and 45 were found to have been produced in Venice, and the glass beads from types 26 and 28 have been assigned to the Bohemian glass industry.While determining the provenance of each glass artefact was a major goal of this study, the process of glass coloring and opacification was also studied in an attempt to establish the technology employed in the production of these artefacts. Chemical data indicate that cobalt and copper were used to produce blue hues, while a combination of copper and iron ions was used to produce green glass. Black colored glass was obtained by the combined use of iron and manganese ions, whereas the iron-sulfur chromophore was used to impart a distinct amber hue to the glass. Red was produced using trace amounts of metallic gold particles (ruby red glass) and metallic copper nano-particles or cuprous oxide (brownish-red glass). Lead arsenates, calcium phosphate, and cassiterite were used as opacifying agents.The use of both morphological and chemical analysis enabled the identification of distinct European production centers, allowing a glimpse into the consumption patterns and economic interactions in place between Europe and West-Central Africa throughout the 17th-19th centuries.

Environmental gas impact on the emission volume of X-rays near the interface in the variable pressure scanning electron microscopy

In this paper, our previously developed model to account for the secondary X-ray fluorescence and absorption effects near the interface of two adjacent materials in a high-vacuum scanning electron microscope (Zoukel & Khouchaf, 2014) is adapted and extended to experimental conditions of low-vacuum mode (in the presence of a gaseous environment in the SEM analysis chamber). The position shifting effect of the two Gaussian peaks issued from the first derivative equation that can fit the experimental low-vacuum EDS profiles is investigated. The impact of the medium gas on the emission volume of secondary X-rays near the interface is qualitatively discussed. Water vapour and helium are successively used as gas environment, in order to link the resolution of microanalysis profiles with the effects of the X-ray fluorescence and absorption phenomenon. A close agreement between Monte Carlo simulation and experimental results is found.

Ultrastructural Assessment of the Anterolateral Ligament.

Background:The anterolateral ligament (ALL) has been identified as a structure on the lateral side of the knee, but debate exists regarding whether it is a capsular thickening or a ligament.Hypothesis:A detailed ultrastructural characterization of the ALL and its ultrastructure collagen arrangement will reveal it more closely resembles ligamentous tissue than joint capsule.Study Design:Descriptive laboratory study.Methods:Eight paired knee samples from 4 fresh-frozen male cadavers were used for this study. Samples were harvested from the ALL, the joint capsule, and the medial collateral ligament (MCL). All samples were evaluated with light microscopy (LM), transmission electron microscopy (TEM), and variable pressure scanning electron microscopy (VP-SEM). With LM, the 3 tissues were analyzed and their morphology described. With TEM, the ultrastructure and collagen characteristics were quantified and compared among specimens. Then, the 3-dimensional characteristics were compared with VP-SEM.Results:Ultrastructure analysis demonstrated similar morphology between the ALL and MCL, with significant differences in these 2 structures as compared with the joint capsule. On LM, the ALL and MCL were characterized by the presence of a dense collagen fiber oriented in the longitudinal and transversal directions of the fiber bundles, while the joint capsule was found to have a more disorganized architecture. On TEM, the collagen fibers of the ALL and MCL demonstrated similar ultrastructural morphology, with both having collagen fibers in parallel, longitudinal alignment. A quantitative analysis was also performed, with the mean (± SD) diameter of fibrils in the ALL and MCL being 80 ± 2.66 nm and 150 ± 3.35 nm, respectively (all P < .001). The VP-SEM highlighted that ALL and MCL morphology demonstrated arrangements of fiber bundles that are densely packed and organized, in contrast to the disorganized fibers of the joint capsule.Conclusion:The ALL and MCL have comparable ultrastructures that are distinctly different from the joint capsule, as visualized on LM, TEM, and VP-SEM.Clinical Relevance:The ALL should be considered a distinctive structure of the knee, although strictly connected to the surrounding capsule.

Skeleton bones in museum indoor environments offer niches for fungi and are affected by weathering and deposition of secondary minerals.

Large skeleton specimens are often featured as iconic open displays in Natural History Museums, for example, the blue whale 'Hope' at the Natural History Museum, London. A study on Hope's bone surface was performed to assess the biodeterioration potential of fungi. Fungi were isolated, and a fungal internal transcribed spacer (ITS) clone library survey was performed on dust and bone material. Mineral particles derived from bone and dust were analysed using energy dispersive X-ray spectroscopy, variable pressure scanning electron microscopy (SEM) and high vacuum SEM. Results showed that bone material, although mainly mineral in nature, and therefore less susceptible than organic materials to biodeterioration phenomena in the indoor environments, offers niches for specialized fungi and is affected by unusual and yet not so well-documented mechanisms of alteration. Areas of bone surface were covered with a dense biofilm mostly composed of fungal hyphae, which produced tunnelling and extensive deposition of calcium and iron-containing secondary minerals. Airborne halophilic and xerophilic fungi including taxa grouping into Ascomycota and Basidiomycota, capable of displacing salts and overcome little water availability, were found to dominate the microbiome of the bone surface.

Effect of water cooling on microscopic damage and dynamic properties of high-temperature granite

The microscopic damage and dynamic mechanical properties of high-temperature granite after water cooling were studied through wave velocity test, nuclear magnetic resonance (NMR) test, split Hopkinson pressure bar (SHPB) impact test and scanning electron microscope（SEM）test. The variation of porosity and dynamic mechanical parameters of granite were analyzed. The results show that the wave velocity of high-temperature granite decreases nonlinearly after water cooling and the components of porosity with large pore increase with the increase of temperature. Moreover, water cooling leads to the more cracks and greater crack sizes than that of natural cooling. The dynamic parameters of high-temperature granite after water cooling show that the increase in temperature results in a decrease in the peak stress, an increase in the peak strain, and an increase at first then decrease in the elastic modulus. Additional thermal stress, resulted from sharply decrease in surface temperature of the high-temperature granite, leads to increased internal damage and decreased wave velocity and peak stress. Compared with natural cooling, the plasticity of high-temperature granite is reduced, because the cold hardening effect improves the hardness of surface granite. After water cooling, the granite specimens exhibit the brittle failure characteristics and their peak strain decreases but their elastic modulus increases. Cooling way has a minor effect on the cracks induced by shock before 400 ℃. As the temperature up to 800 ℃, the impact fracture surface of granite after natural cooling is characterized by honeycomb and irregular shape, in contrast, the impact fracture surface of granite after the water cooling is relatively flat.

Induced Nucleation of Biomimetic Nanoapatites on Exfoliated Graphene Biomolecule Flakes by Vapor Diffusion in Microdroplets

The nucleation of apatite nanoparticles on exfoliated graphene nanoflakes has been successfully carried out by the sitting drop vapor diffusion method, with the aim of producing cytocompatible hybrid nanocomposites of both components. The graphene flakes were prepared by the sonication-assisted, liquid-phase exfoliation technique, using the following biomolecules as dispersing surfactants: lysozyme, L-tryptophan, N-acetyl-D-glucosamine, and chitosan. Results from mineralogical, spectroscopic, and microscopic characterization (X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman, Variable pressure scanning electron microscopy (VPSEM), and transmission electron microscopy (TEM)) indicate that flakes were stacked in multilayers (&gt; 5 layers) and most likely intercalated and functionalized with the biomolecules, while the apatite nanoparticles were found forming a coating on the graphene surfaces. It is worthwhile to mention that when using chitosan-exfoliated graphene, the composites were more homogeneous than when using the other biomolecule graphene flakes, suggesting that this polysaccharide, extremely rich in –OH groups, must be arranged on the graphene surface with the –OH groups pointing toward the solution, forming a more regular pattern for apatite nucleation. The findings by XRD and morphological analysis point to the role of “functionalized graphene” as a template, which induces heterogeneous nucleation and favors the growth of apatite on the flakes’ surfaces. The cytocompatibility tests of the resulting composites, evaluated by the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay in a dose–dependent manner on GTL-16 cells, a human gastric carcinoma cell line, and on m17.ASC cells, a murine mesenchymal stem cell line with osteogenic potential, reveal that in all cases, full cytocompatibility was found.

Multi-analytical approach to the study of the European glass beads found in the tombs of Kulumbimbi (Mbanza Kongo, Angola)

The glass bead assemblages recovered during the 2014 excavations of the ruins of Kulumbimbi located in Mbanza Kongo (Angola) were analyzed by means of a multi-analytical minimally invasive methodology, which includes handheld X-ray fluorescence (hXRF), variable pressure scanning electron microscope coupled with energy dispersive X-ray spectrometry (VP-SEM-EDS), micro-Raman spectroscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Chemical data indicate that cobalt, copper, iron and manganese ions were used to produce the blue, green, reddish-brown and black hues, respectively. Lead arsenates, calcium phosphate, calcium antimonate, lead stannate, cassiterite and Pb-Sb-Sn oxide were used as opacifying agents. Chondrite-normalized trace element distribution and chondrite-normalized rare earth element patterns were used to determine the sand source used in the production of the different glass bead types. These distributions were also used to identify the manufacture location of the glass beads with previously unknown origin and production date. Based on the data collected, the glass beads from types 16, 20, 22, 24, 25, 46 and 47 have been assigned as Venetian.

Characterization of Corrosion Behavior of Archaeological Iron Spear from Sanur (300 BC – 50 AD) – A Megalithic Site in Southern India

Abstract This investigation deals with the chemical composition and microstructural analysis of the iron object, a spear excavated from Sanur, Tamil Nadu- a megalithic site dated 300 B.C. to 50 A.D. Phase analysis and microstructural examination were carried using XRD, optical and variable pressure scanning electron microscope (VP-SEM). Optical micrograph shows the equiaxed grain structure along with the Newman bands. Formation of Newman bands suggests that the original artifact was forged at high temperature followed by cooling, although not so rapid to produce the marked hardening. The absence of carbides at the grain boundary, within the grains and lower value of micro-hardness indicates that the iron spear was not subjected to the carburizing treatment. Results of corrosion characterization revealed that deterioration of excavated iron artifact is associated with the presence of chlorine in corrosion products. However, compact nature of the outer rust (goethite) was helpful in protecting the object. The formation of goethite [ ∝-FeOOH] layer may prevent the iron matrix suffering from attacks by other environmental factors due to its good continuity. In addition, less aerated environment of storage and no history of any cleaning of object were also helpful in preventing the iron spear from further deterioration.

In-situ pore-scale imaging and image-based modelling of capillary trapping for geological storage of CO2

We describe an imaging and pore-scale modelling study of capillary trapping in the Paaratte Sandstone formation in the Otway Basin, Australia. Three-dimensional X-ray computed tomography (micro-CT) was used to characterize the pore structure of the reservoir core. We obtain in-situ pore-scale images of the distribution of CO2:brine analogue fluid pairs (octane:brine) within reservoir samples during low capillary number drainage and imbibition flooding experiments. The images were recorded using time-lapse X-ray micro-tomography at elevated pressure. The observed two-phase fluid distributions are consistent with a water wet system. The micro-CT images are used directly as input to a geometrically accurate quasi-static pore-scale simulation model. The validity of the quasi-static assumption is investigated by comparing on a pore-by-pore basis the simulated and imaged fluid distributions. The pore filling states are in good agreement both for drainage and imbibition displacements and the computed capillary trapping curve agrees with experimental data. This indicate that quasi-static pore-scale physics can be used to obtain averaged or continuum flow properties for low capillary number displacements. We perform a sensitivity study of the impact of the advancing contact angle on capillary trapping. The magnitude of residual trapping increases with decreasing contact angle. Land's trapping coefficient increases with increasing contact angle. We compute capillary pressure and relative permeability scanning curves. Simulated relative permeability hysteresis is compared with that predicted by the industry-standard Carlson's and Killough's models. Killough's model reproduces the simulated data more accurately.

Effective biodiesel synthesis from palm fatty acid distillate (PFAD) using carbon-based solid acid catalyst derived glycerol

Cost efficient and environmental friendly carbon derived glycerol (CG) was prepared by insitu carbonication and sulfonation process. The synthesized CG was sulfonated with H2SO4 for 10 h denoted as SCG-(10) catalyst. The physico-chemical properties of the prepared catalyst were characterized by using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), temperature programmed desorption-ammonia (TPD-NH3), Brunauer–Emmett–Teller (BET) surface area, variable pressure scanning electron microscope (VPSEM), high resolution transmission electron microscopy (HR-TEM) and CHNSO elemental analysis. The specific surface area and total acidity were increased significantly after being sulfonated at different time of reflux; whereas, the SCG-(10) catalyst showed the highest total amount of acidity (35117.14 μmol/g). Esterification of palm fatty acid distillate (PFAD) was successfully obtained high fatty acid methyl esters (FAME) with yield 97.8% at optimum parameter of 18:1 methanol to PFAD molar ratio, 5 wt% catalyst loading and 90 °C reaction temperature within 1 h. The catalyst was successfully reused for 7 cycles and it was found that the catalytic activity maintained with >96% of FAME yield for the first three run. The regenerated SCG-(10) catalyst has been used for another four consecutive of reusability run indicates the viability of utilizing carbon catalyst derived glycerol for biodiesel production.

Effect of Pretreatment Process on Scale Formation in the Re-Boiler Section of Monoethylene Glycol Regeneration Plant

Monoethylene glycol (MEG) regeneration plants often use pretreatment vessels to precipitate divalent cations, such as Fe2+, Ca2+, and Mg2+, in order to avoid or reduce fouling in downstream reboilers and heat exchangers. This pretreatment process operates under alkaline conditions and moderate temperatures (~ 80 °C) to accelerate the formation of low-solubility divalent salts. The objective of the present research was to determine whether the pretreatment process could be minimized, without negatively impacts on the MEG regeneration process from to the formation of scale on the heater bundle in the presence of low concentrations of divalent cations in the rich MEG stream. Scale formation was analyzed under MEG regeneration process conditions using a dynamic scale loop (DSL) test and verification experiments were performed in a MEG regeneration and reclamation pilot plant, both with and without pretreatment conditions. The scaling tendencies of several rich MEG–brine mixtures were evaluated at different pH pretreatment levels and dissolved CO2 concentrations. An evaluation temperature of 180 °C was chosen to match the skin temperature of the reboiler heater bundle during the MEG regeneration process. The experiments of pH 7.24 showed high amounts of precipitation scale within the reboiler due to high remaining concentrations of mineral ions. In addition, small concentrations of calcium and magnesium ions led to the precipitation of calcite, dolomite, and magnesium hydroxide on the reboiler bundle and within associated filtered outputs even when a pretreatment vessel was present. These results were confirmed by the differential pressure build-up and Scanning Electron Microscopy analyses for each experimental condition. Another interesting finding is that pH increased within the reboiler due to CO2 gas boiling off at high operating temperatures, thus contributing to increased alkalinity levels, which in turn promoted scale formation. These results indicate that pretreatment should not be reduced, even with divalent ion concentrations as low as ~ 5 ppm TDS, due to the harsh conditions within the reboiler heater bundle.

Unveiling the ambrotype: characterization of two 19th century photographs-ERRATUM.

This work used a multi-analytical approach to characterize two 19th century ambrotypes and was motivated by the lack of insight on these historical objects. Photographic imaging and optical microscopy (OM) were used to identify abrasions, cracks related to reticulation, tarnishing, and other aspects associated to production and degradation processes. With variable pressure scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (EDS) these processes were seen with great detail and further characterized. Elemental point analysis and elemental mapping showed that the photosensitive material used was silver iodide. Degradation compounds were found as silver and chlorine-containing compounds. In one of the items, the tarnishing area also contained redeposited silver in a ring-shape surrounding a nucleus rich in silver, copper, and sulfur, in addition to copper-based salts. EDS analyses also identified that the supports were common soda–lime–silica glasses, refined with arsenic; and showed that a pigment rich in iron was used in both items to hand color the cheeks, extended with aluminum silicates alone or mixed with barium sulfate. The μ-Raman study pointed out that a synthetic Mars pigment was employed. μ-Fourier-transform infrared spectroscopy analyses identified collodion as the binder. Shellac was used as a protective varnish in one of the items and a gum was possibly employed on the other. Bitumen was used for the background in one ambrotype.

Asbestos fiber identification in liver from cholangiocarcinoma patients living in an asbestos polluted area: a preliminary study.

To assess whether asbestos fibers may be observed in liver tissue of patients with cholangiocarcinoma (CC) with environmental or working asbestos exposure. Detection of fibers was performed directly on histologic sections of liver from 7 patients with CC using optical microscope and variable pressure scanning electron microscopy equipped with energy-dispersive spectroscopy (VP-SEM/EDS). All patients were from Casale Monferrato, Italy, a highly asbestos-polluted town. Due to ethical constraints, observers were blinded to patients' clinical features. Fibers/bundles of fibers of chrysotile were detected in 5 out of 7 patients (71%). The boundary between healthy and neoplastic tissue or the fibrocollagen tissue produced by the neoplasia were identified as areas of fiber incorporation. This study is the first report about the detection of chrysotile asbestos fibers in the liver of patients with CC. Further studies on larger cohorts are needed to corroborate our preliminary findings.

Coherent structures and wind force generation of square-section building model

Typical flow topology of Karman type and arch type vortex shedding from two square-section building models with aspect ratios 2 and 6 is revealed by space-time analysis of fluctuating velocity fields and surface pressure signals obtained by synchronized time-resolved particle-image velocimetry (PIV) and multi-port pressure scanning. Proper orthogonal decomposition (POD) is applied to the PIV data with a pretreatment step to extract the two types of vortex patterns based on their inherent antisymmetry and symmetry features on the horizontal plane about the wake centerline. The antisymmetric POD modes have the general mode shapes of a row of single vortices of alternating rotation senses along the wake centerline, while the mode shapes of the symmetric POD modes show successive pairs of counter-rotating vortices along the wake centerline. When combined with the time-averaged base flow of the wake featuring two stationary recirculating bubbles, the two types of POD modes exhibit the respective vortex patterns of Karman and arch type. The roles of these coherent structures on the generation of fluctuating across-wind force, especially during occurrence of peak force magnitudes, are explored with reconstruction of peak flow events from the lower-order POD modes. The study provides a new insight into the evident connection between the quasi-cycles of antisymmetric POD modes and the generation of quasi-periodic across-wind force.