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This paper discusses the development of mixtures with silica fume as a stabilization/solidification agent and binder for industrial wastewater residue containing organic and heavy metal contaminants. The UCS (Unconfined Compressive Strength) gradually increased to 66.7% as the silica fume content increased to 15%. The leaching of TOC and chromium decreased as more OPC was substituted with silica fume. When the mix had 5% silica fume, it retained about 85% TOC, and chromium leached out 0.76 mg-Cr/g-Cr in acidic solution. Also, microstructural studies on the solidified wastes through the scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and X-ray diffraction analysis showed that the silica fume caused an inhibition to the ettringite formation which did not contribute to setting, but coated the cement particles and retarded the setting reactions. The results indicated that the incorporation of silica fume into the cement matrix minimized the detrimental effects of organic materials on the cement hydration reaction and contaminant leachability.
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PMID:Chemical characteristics and leachability of organically contaminated heavy metal sludge solidified by silica fume and cement. 1154 12

Tape casting procedures were used to form thin polymeric sheets (100 microm thickness) loaded with bioactive glass particulate. Blanks were punched from the sheets, stacked, laminated, and heated in air to 500 degrees C to remove the organic phase. The resulting bioactive glass discs were sintered at 800 degrees C, 900 degrees C, or 1000 degrees C. Because the material is built up in layers and can be machined in the green state, such a processing technique can be used to form complex-shaped materials. The in vitro bioactivity of the tape cast sintered (TCS) bioactive glass-ceramic discs was then assessed in Tris buffer. The sample surface area to volume buffer (SA/V) ratio was approximately 0.1 cm(2)/mL. Tape cast bioactive glass-ceramic sintered at 900 degrees C and 1000 degrees C formed crystalline hydroxyapatite layers after 24 h in Tris buffer as indicated by FTIR, SEM, and EDS analysis. Decreasing the SA/V ratio to 0.013 cm(2)/mL allowed for the formation of crystalline hydroxyapatite layers on the surface of 800C TCS bioactive glass-ceramic. Given the dependence of the bioactive response as a function of the processing schedule and SA/V ratio, it may be possible to tailor the response to that desired in vivo or in vitro for tissue engineering studies. Biaxial flexural strength of TCS bioactive glass-ceramic increased with increasing sintering temperature. Strength of samples sintered at 1000 degrees C for 3 h increased from 87 to 120 MPa after 2 weeks' immersion in Tris buffer.
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PMID:Sintering temperature effects on the in vitro bioactive response of tape cast and sintered bioactive glass-ceramic in Tris buffer. 1155 83

Contact of a fired bullet with an intermediate target of sufficient resistance commonly causes the bullet to ricochet, fragment or perforate together with a deviation in trajectory. The transfer of intermediate target material to bullets and subsequent detection on the bullet surface after recovery from a bullet collector, were examined using a scanning electron microscope and an energy-dispersive X-ray spectrometer (SEM/EDS). A total of 76 gunshots (9 mm Luger FMJ RN bullets) were fired at various intermediate targets and at combinations of intermediate targets and tissue located in line. Elements already present on unfired bullets and elements from the bullet collector, the jacket, the charge and primer could be consistently detected as a "background". Abundant deposits of "fragile" (brittle) materials such as concrete, flat glass, asphalt and gypsum board could be visualised on every bullet by SEM. The transfer dynamics involved a direct imprint of target material on the bullet surface and thus preferential locations at the tip but also indirect deposition over the entire surface ("powder effect"). X-ray microanalysis demonstrated matching spectra of the elemental composition of these deposits and of the targets contacted. After perforation of "ductile" (flexible) materials such as wood and car body parts, the deposits on the bullets did not show characteristic spectra. If multi-layered car metal targets were hit, few and uncharacteristic fragments were scattered over the bullet surface and titanium indicative of paint-work could be determined on only a minority of bullets. The elemental composition of wood itself was heterogeneous but the fibrous morphology of the deposits was typical. The SEM/EDS findings in gunshots including subsequent perforation of tissue were similar. In particular, the trace evidence primarily transferred to the bullets was not eliminated by secondary contact and the determination of the fragile target materials was not affected. So when a person is killed or injured by a gunshot, the presence of a ricochet and the target material can be determined. This possibility needs to be considered before an evidential bullet is cleaned or contaminated.
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PMID:Trajectory reconstruction from trace evidence on spent bullets. I. Deposits from intermediate targets. 1159 64

Dicalcium silicate coatings on titanium alloys substrates were prepared by plasma spraying and immersed in simulated body fluids for a period of time to investigate the nucleation and growth of apatite on the surface of the coatings. Surface structural changes of the specimens were analyzed by XRD and IR technologies. SEM and EDS were used to observe surface morphologies and determine the composition of dicalcium silicate coatings before and after immersion in simulated body fluid. The plasma sprayed dicalcium silicate coating was bonding tightly to the substrate. The coating was mainly composed of beta-Ca2SiO4 and glassy phase. A dense carbonate-containing hydroxyapatite (CHA) layer was formed on the surface of the plasma sprayed dicalcium silicate coating soaked in SBF solution for 2 days. In addition, a silica-rich layer was also observed between CHA layer and coatings. With an increase in the immersion time, the CHA layer gradually became thicker. The results obtained indicated that the plasma sprayed dicalcium silicate coating possesses excellent bioactivity.
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PMID:Bioactivity of plasma sprayed dicalcium silicate coatings. 1177 15

Spherulitic crystallisation is a mode of growth of crystals from the melt. Considerable attention has been given to spheroidal graphite formation, providing detailed information about the internal microstructure of the spherulites in spheroidal (SG irons) and compacted graphite irons (CG irons) (Stefanescu, D., 1990. Cast Irons. ASM Handbook, 10th ed., vol. 1). Nevertheless, the mechanisms responsible for this mode of crystallisation are not fully understood. This study deals with the inoculation mechanisms, with particular emphasis on the study of the inclusions for the heterogeneous nucleation of graphite. It is shown that the graphite nuclei are sulfide products of the nodularizing treatment. It has been observed that when rare-earth treatment is applied, the central nucleus consists of a core and an envelope from which the graphite grows. Confocal Scanning Laser Microscopy (CSLM), in reflection mode, was used to study the internal features of the spheroidal graphite growth. Confocal reflection imaging, which has a capacity for optical sectioning of the sample, provides high-resolution images of surface and subsurface regions of interest contained within a semi-transparent sample. Furthermore, three-dimensional reconstruction of these optical sections can provide insight into the mechanism of graphite growth mechanism interpretation. With CSLM the radial growth of graphite was seen. Other techniques, such as TEM, SEM-EDS, WDS, AES and SAM were also used to corroborate the results.
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PMID:Internal features of graphite in cast irons. Confocal microscopy: useful tool for graphite growth imaging. 1181 75

The speciation of U(VI) sorbed to synthetic hydroxyapatite was investigated using a combination of U LIII-edge XAS, synchrotron XRD, batch uptake measurements, and SEM-EDS. The mechanisms of U(VI) removal by apatite were determined in order to evaluate the feasibility of apatite-based in-situ permeable reactive barriers (PRBs). In batch U(VI) uptake experiments with synthetic hydroxyapatite (HA), near complete removal of dissolved uranium (>99.5%) to <0.05 microM was observed over a range of total U(VI) concentrations up to equimolar of the total P in the suspension. XRD and XAS analyses of U(VI)-reacted HA at sorbed concentrations < or = 4,700 ppm U(VI) suggested that uranium(VI) phosphate, hydroxide, and carbonate solids were not present at these concentrations. Fits to EXAFS spectra indicate the presence of Ca neighbors at 3.81 A. U-Ca separation, suggesting that U(VI) adsorbs to the HA surfaces as an inner-sphere complex. Uranium(VI) phosphate solid phases were not detected in HA with 4700 ppm sorbed U(VI) by backscatter SEM or EDS, in agreement with the surface complexation process. In contrast, U(VI) speciation in samples that exceeded 7000 ppm sorbed U(VI) included a crystalline uranium(VI) phosphate solid phase, identified as chernikovite by XRD. At these higher concentrations, a secondary, uranium(VI) phosphate solid was detected by SEM-EDS, consistent with chernikovite precipitation. Autunite formation occurred at total U:P molar ratios > or = 0.2. Our findings provide a basis for evaluating U(VI) sorption mechanisms by commercially available natural apatites for use in development of PRBs for groundwater U(VI) remediation.
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PMID:Mechanisms of uranium interactions with hydroxyapatite: implications for groundwater remediation. 1182 49

The walls of the Oratorio of San Giovanni Battista in Urbino are decorated with outstanding mural paintings dating back to the 15th century. Due to degradation processes that have occurred in the past years, such paintings require a conservative restoration project. In order to evaluate reasons of the decay, some scientific studies have been performed. They consist of macroscopic observations and chemical (EDS), morphological (SEM) and mineralogical (XRD) analyses of samples both from the original preparatory layers under the painted layers and from the restored plasters at the surbase of the wall. In addition, environmental studies have been performed to verify microclimatic conditions of the church in which the mural paintings are located. Finally, a conservative restoration project was proposed.
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PMID:The wall paintings in the Oratorio of San Giovanni Battista in Urbino: a study finalized to a correct conservation project. 1183 55

Germanium nanowires, ranging from 10 to 150 nm in diameter, were grown several micrometers in length in cyclohexane heated and pressurized above its critical point. Alkanethiol-protected gold nanocrystals, either 2.5 or 6.5 nm in diameter, were used to seed wire formation. Growth proceeded through a solution-liquid-solid mechanism at growth temperatures ranging from 300 to 450 degrees C. At temperatures exceeding 500 degrees C, large Ge particulates formed due to unfavorable growth kinetics. Temperature, the nature of the precursor, precursor concentration, and the Au:Ge ratio were determining factors in nanowire morphology. The Ge nanowires were characterized using a range of techniques, including XPS, XRD, high-resolution TEM and SEM, nanometer-scale EDS mapping, and DTA.
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PMID:Nucleation and growth of germanium nanowires seeded by organic monolayer-coated gold nanocrystals. 1184 11

The role of arbuscular mycorrhiza in reducing Cd stress was investigated in three genotypes of Pisum sativum L. (cv. Frisson, VIR4788, VIR7128), grown in soil/sand pot cultures in the presence and absence of 2-3 mg kg(-1) bioavailable Cd, and inoculated or not with the arbuscular mycorrhizal fungus Glomus intraradices. Shoot, root and pod biomass were decreased by Cd in non-mycorrhizal plants. The presence of mycorrhiza attenuated the negative effect of Cd so that shoot biomass and activity of photosystem II, based on chlorophyll a fluorescence, were not significantly different between mycorrhizal plants growing in the presence or absence of the heavy metal (HM). Total P concentrations were not significantly different between mycorrhizal and non-mycorrhizal plants treated with Cd. From 20-50-fold more Cd accumulated in roots than in shoots of Cd-treated plants, and overall levels were comparable to other metal-accumulating plants. Genetic variability in Cd accumulation existed between the pea genotypes. Concentration of the HM was lowest in roots of VIR4788 and in pods of VIR4788 and VIR7128. G. intraradices inoculation decreased Cd accumulation in roots and pods of cv. Frisson, whilst high concentrations were maintained in roots and pods of mycorrhizal VIR7128. Shoot concentrations of Cd increased in mycorrhizal cv. Frisson and VIR4788. Sequestration of Cd in root cell walls and/or cytoplasm, measured by EDS/SEM, was comparable between non-mycorrhizal pea genotypes but considerably decreased in mycorrhizal cv. Frisson and VIR7128. Possible mechanisms for mycorrhiza buffering of Cd-induced stress in the pea genotypes are discussed.
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PMID:Cadmium accumulation and buffering of cadmium-induced stress by arbuscular mycorrhiza in three Pisum sativum L. genotypes. 1197 28

With increasing frequency, relatively small, fragmentary evidence thought to be osseous or dental tissue of human origin is submitted to the forensic laboratory for DNA analysis with the request for positive identification. Prior to performing DNA analysis, however, it is prudent to first perform a presumptive test or "screen" to determine whether the questioned material may be eliminated from further consideration. When material is shown not to be consistent with bone/teeth, DNA testing is not performed. When such determinations cannot be made from gross morphological features, elemental analysis can be indicative. This presumptive test is made possible by applying scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) in conjunction with an X-ray spectral database recently developed by the FBI laboratory. This database includes spectra for many different materials including known examples of bone and tooth from many different contexts and representing the full range of taphonomic conditions. Results of SEM/EDS analysis of evidence can be compared to these standards to determine if they are consistent with bone and/or tooth and, if not, then what the material might represent. Analysis suggests that although the proportions and amounts of calcium and phosphorus are particularly important in differentiating bone and tooth from other materials, other minor differences in spectral profile can also provide significant discrimination. Analysis enables bone and tooth to be successfully distinguished from other materials in most cases. Exceptions appear to be ivory, mineral apatite, and perhaps some types of corals.
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PMID:The use of SEM/EDS analysis to distinguish dental and osseus tissue from other materials. 1235 78


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