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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bioactive glass fibers are attractive materials for use as tissue-engineering scaffolds and as the reinforcing phase for resorbable bioactive composites. The bioactivity of S520 glass fibers (52.0 mol % SiO(2), 20.9 Na(2)O, 7.1 K(2)O, 18.0 CaO, and 2.0 P(2)O(5)) was evaluated in two media, simulated body fluid (SBF) and Dulbecco's modified Eagle's medium (DMEM), for up to 20 days at 37 degrees C. Hydroxyapatite formation was observed on S520 fiber surfaces after 5 h in SBF. After a 20-day immersion, a continuous hydroxyapatite layer was present on the surface of samples immersed in SBF as well as on those samples immersed in DMEM [fiber surface area to solution volume ratio (SA:V) of 0.10 cm(2)/mL]. Backscattered electron imaging and EDS analysis revealed that the hydroxyapatite layer formation was more extensive for samples immersed in SBF. Decreasing the SA:V ratio to 0.05 cm(2)/mL decreased the time required to form a continuous hydroxyapatite surface layer. ICP was used to reveal Si, Ca, and P release profiles in DMEM after the 1st h (15.1, 83.8, and 29.7 ppm, respectively) were similar to those concentrations previously determined to stimulate gene expression in osteoblasts in vitro (16.5, 83.3, and 30.4 ppm, respectively). The tensile strength of the 20-microm diameter fibers was 925 +/- 424 MPa. Primary human osteoblast attachment to the fiber surface was studied by using SEM, and mineralization was studied by using alizarin red staining. Osteoblast dorsal ruffles, cell projections, and lamellipodia were observed, and by 7 days, cells had proliferated to form monolayer areas as shown by SEM. At 14 days, nodule formation was observed, and these nodules stained positive for alizarin red, demonstrating Ca deposition and, therefore mineralization.
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PMID:In vitro bioactivity of S520 glass fibers and initial assessment of osteoblast attachment. 1451 88

Complementary studies on the inorganic chemical composition of Nerium oleander leaves collected in the town of Messina (Sicily, Italy) and seven grain-size fractions of local roadway dust have been carried out. Data and maps are presented to show that the particulate matter present in the air of Messina contains trace elements significantly in excess with respect to the average continental earth crust. The anomalies follow the outline of the urban area, the highest concentrations of trace elements being observed where traffic density is highest. Chemical and isotopic analyses of both road dust and Nerium oleander leaves indicate that Pb contamination still characterizes roads with heavy traffic. In addition to Pb, other metals such as Pt, Pd, Sb, Au, Br, Zn, Cu, Mo, and Cd are significantly enriched in roadway dust, indicating their common anthropogenic origin, especially from traffic. SEM/EDS study of some roadway dust particles has shown the presence of gypsum probably of secondary origin, mixed particles formed by coagulation or gas-to-particle conversion, and porous spherical particles apparently emanating from combustion processes.
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PMID:The effects of anthropogenic particulate emissions on roadway dust and Nerium oleander leaves in Messina (Sicily, Italy). 1458 47

A mercury plating technique was used to determine the phases forming on experimental Ag-Sn-Cu alloy powders (with and without Pd) exposed to electrolytically deposited mercury. Four series of alloy powders were made: a) 1.5% Pd with 10-14% Cu (CU series); b) 1.0% Pd with 10-14% Cu (1PD series); c) 1.5% Pd with different ratios of Ag3Sn (gamma) to Ag4Sn (beta) with 12% Cu (AGSN series); and d) 9-13% Cu with no Pd (NOPD series). Each powder was pressed on a freshly prepared amalgam specimen made from the same powder and metallographically polished until cross sections appeared; mercury was electroplated on the alloy particles. Alloy powders, amalgams and electroplated specimens were examined using XRD and SEM/EDS. XRD confirmed the presence of gamma2 in amalgams made from alloys with Cu < 13% or with Ag3Sn/Ag4Sn > 0.8. Specimens with moderately plated Hg showed gamma1 (Ag2Hg3) polyhedra and eta' Cu6Sn5, but not gamma2. This method effectively identifies alloys prone to forming gamma2.
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PMID:Evaluation of the amalgamation reaction of experimental Ag-Sn-Cu alloys containing Pd using a mercury plating technique. 1462 23

To evaluate the deterioration in the superelasticity of Ti-coated NiTi orthodontic wires, titanium was coated onto wires to form a 1-microm thick film using radio frequency magnetron sputtering. In superelasticity cycle tests, the sigma5.0 value (the stress at 5.0% strain) of a Ti-coated wire was lower than that of a non-coated wire by 6.2% after one cycle, and by 10.4% after 20 cycles. In a three point bend tests, the L2.0 value (the load at 2.0 mm deflection) of a Ti-coated wire was 2.55 N, and this was reduced by 39.0% of the L2.0 value of a non-coated wire (4.18 N). After the non-coated and the Ti-coated wires had been immersed in physiological saline for periods of four and eight weeks, the concentration of Ni ions released into each solution was detected using MIP-Mass, and Ni peak intensity of the wires was measured using XPS. After eight weeks, the concentration of Ni ions released from the non-coated and the Ti-coated wires was 657 and 135 ppb, respectively. In a clinical test, no inflammation was observed during the entire attached period of four weeks in both the non-coated and the Ti-coated wire. In the Ti-coated wire, little exfoliation of the Ti-coating was observed using SEM and EDS. It was concluded that Ti-coated NiTi orthodontic wire has much potential for its application, with a low probability of causing any Ni allergy.
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PMID:Deterioration in the superelasticity of Ti sputter coated on NiTi orthodontic wire. 1464 50

Hydroxyapatite (HA) was coated onto titanium substrates using radio frequency sputtering, and the coated HA films were crystallized in an autoclave at 110 degrees C using a low temperature hydrothermal method. The crystallite size, the Ca/P ratio, and the surface of the films were observed using XRD, EDS, and SEM, respectively. An immersion test was carried out in physiological saline solution, and the film-to-substrate adhesion strength was measured using a pull-out test. From the XRD patterns, a sputtered film subjected to the hydrothermal treatment had crystallized after 24 h, and the crystallite size increased from 38.0+/-8.7 to 81.4+/-19.1 nm. In immersion tests, an as-sputtered film completely dissolved after 1 d, whereas a sputtered film subjected to the hydrothermal treatment survived to 18.7+/-5.8% of the initial film thickness after four weeks. In pull-out tests, the adhesion strength of the sputtered film to the substrate increased from 1.9+/-0.2 to 5.3+/-1.6 MPa after the hydrothermal treatment. A sputtered film subjected to the hydrothermal treatment and a plasma-sprayed coating on titanium columns were implanted in the diaphysis of the femora of six adult dogs, and a pull-out test was carried out after two, four, and 12 weeks. The sputtered film showed higher bone bonding strength than the plasma-sprayed coating at any period.
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PMID:Bone bonding strength of sputtered hydroxyapatite films subjected to a low temperature hydrothermal treatment. 1464 59

An alkaline extraction method has been developed for the determination of total sulfate in mine tailings containing secondary sulfate minerals formed by the oxidation of primary sulfides. Oxidized tailings were extracted with a 0.3 M NaOH solution at a liquid/solid ratio of 30 at room temperature for 16 h. The sulfate concentration in the extracts was determined by ion chromatography (IC). The coefficient of variation for sulfate determinations ranged from 1.9 to 3.2% for five tailings samples collected at two tailings impoundments. Mineralogical analysis of the tailings by scanning electron microscopy/X-ray energy dispersive spectrometry (SEM/EDS) demonstrated that the extraction of sulfate was complete, with the exception of extremely insoluble barite. The proposed method is simple, yields an accurate yet rapid measurement of sulfate, and involves a safer laboratory operation than conventional methods that make use of strong HCl acid solutions. Moreover, this method allows the specific measurement of sulfate in the extract, whereas conventional methods are generally limited to the measurement of total S by inductively coupled plasma atomic emission spectrometry (ICP-AES) due to the interference of chloride with sulfate in IC.
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PMID:Use of alkaline extraction to quantify sulfate concentration in oxidized mine tailings. 1467 67

The adhesion between titanium and dental porcelain is related to the diffusion of oxygen to the reaction layer formed on cast-titanium surfaces during porcelain firing. The diffusion of oxygen could be suppressed by coating the titanium surface with a thin gold layer. This study characterized the effects of gold coating on titanium-ceramic adhesion. ASTM grade II CP titanium was cast into a MgO-based investment (Selevest CB, Selec). The specimen surfaces were air abraded with 110-microm Al(2)O(3) particles. Gold coating was applied on titanium surfaces by three methods: gold-paste (Deck Gold NF, Degussa-Ney) coating and firing at 800 degrees C for three times, single gold-paste coating and firing followed by sputter coating (40 mA, 500 s), and sputter coating (40 mA, 1000 s). Surfaces only air abraded with Al(2)O(3) particles were used as controls. An ultra-low-fusing dental porcelain (Vita Titankeramik, Vident) was fused on titanium surfaces. Specimen surfaces were characterized by SEM/EDS and XRD. The titanium-ceramic adhesion was evaluated by a biaxial flexure test (N = 8), and area fraction of adherent porcelain (AFAP) was determined by EDS. Numerical results were statistically analyzed by one-way ANOVA and the Student-Newman-Keuls test at alpha = 0.05. SEM fractography showed a substantial amount of porcelains remaining on the gold-sputter-coated titanium surfaces. A new Au(2)Ti phase was found on gold-coated titanium surface after the firing. Significantly higher (p <.05) AFAP values were determined for the gold-sputter-coated specimens compared to the others. No significant differences were found among the other groups and the control. Results suggested that gold coatings used in this study are not effective barriers to completely protect titanium from oxidation during the porcelain firing, and porcelain adherence to cast titanium can be improved by gold-sputter coating used in the present study.
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PMID:SEM/EDS evaluation of porcelain adherence to gold-coated cast titanium. 1473 64

Immobilization of a model liquid organic pollutant, i.e. the 2-chloroaniline (2-CA), into a cement matrix using organoclays as pre-sorbent agents was investigated. Five cement-clay pastes were prepared with different nominal water-to-cement ratios (w/c=0.40, 0.25 and 0.15 wt/wt) and various amounts of waste (waste-to-cement o/c=0.20, 0.60 and 1.00 wt/wt); for comparison, a neat cement paste was also prepared. Dynamic leach tests were performed on solidified monoliths in order to assess the successful immobilization of the 2-CA. In monoliths at constant w/c ratio (0.40) the total amount of pollutant released increases with its initial content, and ranges from 15 to 35% with respect to it. By lowering w/c from 0.40 to 0.15 at constant o/c, the performances improved (<25% released). The microstructure of the hardened cement-clay pastes was characterized by quantitative X-ray diffraction (QXRD) and electronic microscopy (SEM-EDS) techniques; hydration degree was estimated by means of thermogravimetric analysis (TGA) in addition to QXRD. No evidence of any chemical reaction between 2-CA and cement phases was found. Moreover, it was shown that the most important factors affecting the cement hydration process were the total water content, i.e. the one taking also into account the water contained in the wet polluted clay, and the amount of 2-CA not firmly sorbed by the organoclay, and then freely dispersed in the paste.
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PMID:Cement-clay pastes for stabilization/solidification of 2-chloroaniline. 1476 60

Wollastonite/tricalcium phosphate composites were prepared and immersed in SBF for various periods to investigate the apatite-formation mechanism on their surfaces. Surface morphologies and composition before and after immersion were analyzed by SEM and EDS technologies. The concentration changes of calcium, silicon, and phosphorus in SBF due to the immersion of the samples were measured with inductively coupled plasma atomic emission spectroscopy, and the corresponding pH values in SBF were recorded. XRD and IR were used to examine the changes in crystalline phases and functional groups. It was found that, after immersion for 1 day, the samples were covered by pom-pom-like apatite granules, resulting from the dissolution of wollastonite and the simultaneous transformation of TCP. This quickly led to the subsequent precipitation of another apatite layer, which covered the earlier-formed surface completely. These results indicate that the wollastonite/tricalcium phosphate composite is a potential biomaterial candidate because of its high bioactivity and in situ porous structure.
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PMID:Apatite formation on the surface of wollastonite/tricalcium phosphate composite immersed in simulated body fluid. 1501 12

In the present article, the treatment of groundwater containing Mn(II) and Fe(II) has been investigated. The biological oxidation of Mn(II) and Fe(II) in upflow filtration units comprised the applied experimental technique. The oxidation processes were mediated by specific bacteria, namely the Leptothrix ochracea and Gallionella ferruginea, which belong to the general category of manganese and iron oxidizing bacteria. This work was focused on the characterization of the products of biological oxidation and to the examination of the kinetics of Mn(II) removal as compared with Fe(II) removal from groundwaters. The products of biological oxidation were characterized using the spectroscopic techniques XRD, XPS and SEM-EDS and comprised a mixture of biogenic hydrous manganese and iron oxides. The oxidation state of manganese in the precipitates was found to be between 3 and 4. Iron oxides were mainly in the form of amorphous ferrihydrite. The kinetic results indicated that the rates of manganese and iron oxidation were several orders of magnitude greater than the respective for abiotic oxidation. The bacterially mediated oxidation of iron was faster than manganese oxidation, presenting half-lives of reaction 0.9 and 3.98 min, respectively.
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PMID:Biological treatment of Mn(II) and Fe(II) containing groundwater: kinetic considerations and product characterization. 1502 47


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