Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Results from experiments using an impregnation-reduction (I-R) Pt / Nafion membrane electrode assembly (MEA) in an air fuel cell cathode to remove contaminants (Cu(II), Ni(II), and Fe(III)) from spent chromium electroplating baths are presented in this study. A platinum-carbon (Pt-C) / Nafion MEA and a Pb planar cathode were also used for comparison. The average removal rates of Cu(II) and Ni(II) were almost the same (0.39 and 0.40 mM hr(-1) (or 0.117 and 0.12 mmol hr(-1)), respectively) but higher than that of Fe(III) (0.16 mM hr(-1), or 0.048 mmol hr(-1)) in accordance with the Nernst-Planck flux equation. The removal rates for the same cation were independent of the cathode used. The average removal rate of each impurity was approximately proportional to the product of its initial concentration and separator area/anolyte volume ratio using Pb cathodes. Under constant current conditions the system using the Pt-C / Nafion cathode needed the highest cell voltage, about 3 V more than needed for the system with the Pt / Nafion cathode. The cell voltage required using the Pt / Nafion cathode was similar to that using the conventional planar Pb cathode. Analyses of cathode deposits by SEM/EDS and XPS techniques indicated they were minimal on the Pb and Pt / Nafion cathode and more apparent on the Pt-C / Nafion cathode. The primary deposits on the Pb cathode were chromium oxides (e.g., Cr2O3) with minor amount of lead chromate (lead dichromate or lead trichromate) and other chromium solids (Cr black). As expected, the dominant deposit on the lead anode surface was PbO2.
 ...
PMID:The use of air fuel cell cathodes to remove contaminants from spent chromium plating solutions. 1502 48

The possibility of detection of lead-antimony-barium aggregates from non-firearm sources is confirmed according to the tests performed on brake pads, and firework and automobile workers. Moreover, information on particles taken from cartridge cases shows the relative feeble importance of the morphology in distinguishing gunshot residues (GSRs). Furthermore, also the presence in the spectrum of other elements (e.g., iron) is not so conclusive. In this panorama, the possibility of discriminating gunshot residue particles from other non-firearm lead-antimony-barium aggregates is investigated: the proposed method is based on X-ray mapping technique--currently applied used in Reparto Carabinieri Investigazioni Scientifiche in Rome, the forensic service of Italian Carabinieri--according to which the spatial distribution of the emission energy of each element of the sample is pictured. Gunshot residues present the same lead-antimony-barium distribution (or at least the same antimony-barium distribution with lead nodules), as some other environmental occupational aggregates do not (different plaques of lead, antimony, and barium). So, X-ray mapping technique can offer a new fundamental evaluation parameter in analysis of gunshot residues with scanning electron microscopy/energy-dispersive (SEM/EDS) spectrometry, and new standards could be considered.
 ...
PMID:X-ray mapping technique: a preliminary study in discriminating gunshot residue particles from aggregates of environmental occupational origin. 1517 26

The influence of sodium silicate on the ability of a diacetylene-containing phospholipid (23:2 diyne PC) to inhibit the oxidation of pyrite at pH 2 and pH 6 was investigated. The phospholipid used has previously been reported to show up to 80% suppression of pyrite oxidation and to show excellent stability down to at least pH 2. Pyrite was leached with a solution containing Fe3+ but no coating agent and three different solutions or treatments: a lipid treatment, a silicate treatment, and a lipid + silicate treatment. Pyrite oxidation was based on iron (Fe3+, Fe2+) leached out of a continuous-flow porous-bed reactor system. The results show that at pH 6 the silicate and lipid both bind strongly to the pyrite surfaces, providing a barrier that inhibits the production and subsequent release of oxidation products. The lipid is superior to the silicate in suppressing pyrite oxidation at both pH 2 and pH 6. Also, the presence of silicates decreased the ability for the lipid to suppress pyrite oxidation, both at pH 2 and pH 6. The reaction mechanism for pyrite oxidation at pH 2 is first order for pyrite leached by solutions containing only ferric, ferric together with silicate, and ferric combined with silicate and lipid. The only treatment that effectively prevented pyrite oxidation at pH 2 was the lipid treatment. The Fe speciation results are supported by both SEM images and EDS calculations.
 ...
PMID:Inhibition of pyrite oxidation by a phospholipid in the presence of silicate. 1526 Mar 45

The aim of this work was to study the influence of the phosphorus on the crystallization and bioactivity of glass-ceramics obtained from sol-gel glasses. For this purpose two sol-gel glasses with a similar composition but one of them containing P2O5 (70% SiO2; 30% CaO and 70% SiO2; 26% CaO; 4% P2O5, mol%) were prepared. Pieces of these glasses were treated at temperatures ranging between 700 degrees C and 1400 degrees C for 3 h. The obtained materials were characterized by XRD, FTIR, SEM-EDS and the biaxial flexural strength was determined in samples heated at 1100 degrees C. In addition, an in vitro bioactivity study in simulated body fluid (SBF) was carried out. The results showed that phosphorus plays an important role in the crystallization of the glasses: it induced the crystallization of calcium phosphate phases, the stabilization of the wollastonite phase at high temperature as well as the crystallization of SiO2 phases at low temperatures. Moreover, the presence of phosphorus produced a heterogeneous distribution of defects in the pieces and, therefore, the flexural strength of samples containing this element decreased. Finally, glass-ceramics obtained from glasses containing phosphorus showed the fastest formation rate of the apatite layer when soaked in SBF.
 ...
PMID:The influence of the phosphorus content on the bioactivity of sol-gel glass ceramics. 1527 55

Hydroxyapatite (HAp) coatings were deposited onto substrates of metal biomaterials (Ti, Ti6Al4V, and 316L stainless steel) by electrophoretic deposition (EPD). Only ultra-high surface area HAp powder, prepared by the metathesis method 10Ca(NO3)2 + 6(NH4)2HPO4 + 8NH4OH), could produce dense coatings when sintered at 875-1000degreesC. Single EPD coatings cracked during sintering owing to the 15-18% sintering shrinkage, but the HAp did not decompose. The use of dual coatings (coat, sinter, coat, sinter) resolved the cracking problem. Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) inspection revealed that the second coating filled in the "valleys" in the cracks of the first coating. The interfacial shear strength of the dual coatings was found, by ASTM F1044-87, to be approximately 12 MPa on a titanium substrate and approximately 22 MPa on 316L stainless steel, comparing quite favorably with the 34 MPa benchmark (the shear strength of bovine cortical bone was found to be 34 MPa). Stainless steel gave the better result since -316L (20.5 microm mK(-1)) > alpha-HAp (approximately 14 microm mK(-1)), resulting in residual compressive stresses in the coating, whereas alpha-titanium (approximately 10.3 microm mK(-1)) < alpha-HAp, resulting in residual tensile stresses in the coating.
 ...
PMID:Interfacial bond strength of electrophoretically deposited hydroxyapatite coatings on metals. 1534 25

The aim of this research is to develop a new methodology to obtain bioactive coatings on bioinert and biodegradable polymers that are not intrinsically bioactive. In this study three types of materials were used as substrates: (i) high molecular weight polyethylene (HMWPE) and two different types of starch based blends (ii) starch/ethylene vinyl alcohol blends, SEVA-C and (iii) starch/cellulose acetate blends, SCA. Two types of baths were originally proposed and studied to produce novel auto-catalytic calcium-phosphate (Ca-P) coatings. Then, the coated surfaces were analyzed by scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), as produced, and after different immersion periods in SBF. The evolution of Ca and P concentrations was determined by induced-coupled plasma emission (ICP) spectroscopy. The crystalline phases present on the films formed on the different material surfaces, after a certain soaking time, were identified by thin-film X-ray diffraction (TF-XRD). The obtained results indicated that it was possible to coat the materials surfaces with a Ca-P layer with only 60 min of immersion in both types of auto-catalytic solutions. Furthermore, it was possible to observe the clear bioactive nature of the Ca-P coatings after different immersion periods in a simulated body fluid (SBF). The results from TF-XRD confirmed the presence of partially amorphous Ca-P films with clearly noticeable hydroxylapatite peaks. These new methodologies allow for the production of an adherent bioactive film on the polymeric surfaces prior to implantation, which may allow for the development of bone-bonding, bioabsorbable implants and fixation devices.
 ...
PMID:An innovative auto-catalytic deposition route to produce calcium-phosphate coatings on polymeric biomaterials. 1534 47

Natural and bioprosthetic heart valves suffer from calcification, despite their differences in etiology and tissue material. The mechanism of developing calcific deposits in valve tissue is still not elucidated. The calcific deposits developed on human natural and bioprosthetic heart valves have been investigated and compared by physicochemical studies and microscopy investigations and the results were correlated with possible mechanisms of mineral crystal growth. Deposits from 16 surgically excised calcified valves (seven natural aortic and nine bioprosthetic porcine aortic valves) were examined by chemical analysis, FTIR, XRD, and SEM-EDS. The Ca/P molar ratio of the deposits from bioprosthetic valves (1.52+/-0.06) was significantly lower compared to that of the natural valves (1.83+/-0.03) (p=0.05, 1-way ANOVA). SEM-EDS examination of the two types of valve deposits revealed the coexistence of large (>20 microm) and medium (5-20 microm) plate-like crystals as well as microcrystalline (<5 microm) calcium phosphate mineral formations. The results confirmed the hypothesis that the mineral salt of calcified valves is a mixture of calcium phosphate phases such as dicalcium phosphate dihydrate (DCPD), octacalcium phosphate (OCP) and hydroxyapatite (HAP). DCPD and OCP are suggested to be precursor phases transformed to HAP by hydrolysis. The lower value of the Ca/P molar ratio found in the bioprostheses, in comparison with that corresponding in natural valves, was ascribed to the higher content in these deposits in precursor phases DCPD and OCP which were subsequently transformed into HAP. On the basis of chemical composition of the deposits and their morphology it is suggested that crystal growth proceeds in both types of valves by the same mechanism (hydrolysis of precursor phases to HAP) in spite of their differences in etiology, material, and possible initiation pathways.
 ...
PMID:Physicochemical and microscopical study of calcific deposits from natural and bioprosthetic heart valves. Comparison and implications for mineralization mechanism. 1534 54

The biomimetic method was used in order to deposit, on titanium substrates, an hydroxyapatite (HA) coating. The bioactive HA layer was obtained by using, in the first stage of the process, a glass having the composition 2.5CaO.2SiO(2) different from the one proposed for the application of the biomimetic method. This glass can be obtained via sol-gel, a method that allows one to obtain, easily, very pure products. The growth of HA crystals was confirmed by Fourier transform infrared, SEM, EDS and X-ray photoelectron spectroscopy (XPS) results. The experimental results suggest that, as reported in the literature for other supports, the silicate ions released from the glass in the first stage bind themselves to the titanium support. In particular, from XPS analysis it is evident that the titanium substrate is well covered by a calcium phosphate layer of the type of HA.
 ...
PMID:Hydroxyapatite coating of titanium by biomimetic method. 1534 55

Ti-based biocompatible alloys are especially used for replacing failed hard tissue. Some of the most actively investigated materials for medical implants are the beta-Ti alloys, as they have a low elastic modulus (to inhibit bone resorption). They are alloyed with elements such as Nb, Ta, Zr, Mo, and Fe. We have prepared a new beta-Ti alloy that combines Ti with the non-toxic elements Ta and Mo using a vacuum arc-melting furnace and then annealed at 950 degrees C for one hour. The alloy was finally quenched in water at room temperature. The Ti-12Mo-5Ta alloy was characterised by X-ray diffraction, optical microscopy, SEM and EDS and found to have a body-centred-cubic structure (beta-type). It had a lower Young's modulus (about 74 GPa) than the classical alpha/beta Ti-6Al-4V alloy (120 GPa), while its Vickers hardness remained very high (about 303 HV). This makes it a good compromise for a use as a bone substitute. The cytocompatibility of samples of Ti-12Mo-5Ta and Ti-6Al-4V titanium alloys with various surface roughnesses was assessed in vitro using organotypic cultures of bone tissue and quantitative analyses of cell migration, proliferation and adhesion. Mechanically polished surfaces were prepared to produce unorientated residual polished grooves and cells grew to a particularly high density on the smoother Ti-12Mo-5Ta surface tested.
 ...
PMID:Development of a beta-type Ti-12Mo-5Ta alloy for biomedical applications: cytocompatibility and metallurgical aspects. 1547 40

Sol-gel processing was used to coat titanium substrates with hydroxyapatite (HA), TiO2, and poly(DL-lactic-glycolic acid). Coating surface characteristics were analyzed with XRD, EDS, AFM, SEM, and water contact angle measurements which indicated that the coatings had a high degree of crystallinity and good resistance to cracking. Coatings were also evaluated by cytocompatibility testing with osteoblast-like cells (or bone-forming cells). The cytocompatibility of the HA composite coatings prepared in the present in vitro study was compared to that of a traditional plasma-sprayed HA coating. Results showed that osteoblast-like cell adhesion was promoted on the novel HA sol-gel coating compared to the traditional plasma-sprayed HA coating. In addition, hydrothermal treatment of the sol-gel coating improved osteoblast-like cell adhesion. Since osteoblast adhesion is a necessary prerequisite for subsequent formation of bone, these results provided evidence that hydrothermally sol-gel processed HA may improve bonding of titanium implants to juxtaposed bone and, thus, warrants further investigation.
 ...
PMID:Enhanced osteoblast adhesion on hydrothermally treated hydroxyapatite/titania/poly(lactide-co-glycolide) sol-gel titanium coatings. 1548 22


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>