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Copper corrosion in the presence of orthophosphate and chlorine has indicated the formation of a protective scale containing either CuO or Cu2O depending on the pH. Furthermore, the scale forms relatively quickly, after 15 days of immersion EIS showed very little change. The scale is initially porous, but after prolonged immersion, the porous structure disappears, as evidenced by SEM. The equivalent circuit that is used to model the EIS spectra fits the data well and yields useful information on values, such as Rct, which varies from 2 to 10 kohms and Rfilm, which varies from 15 to 80 kohms when the immersion time is extended from 2 to 30 days.
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PMID:Copper corrosion kinetics and mechanisms in the presence of chlorine and orthophosphate. 1498 66

Composites based on phenolic matrices and unmodified and chemically modified sugar cane bagasse and curaua fibers were prepared. The fibers were oxidized by chlorine dioxide, mainly phenolic syringyl and guaiacyl units of the lignin polymer, followed by grafting furfuryl alcohol (FA), which is a chemical obtained from a renewable source. The fibers were widely characterized by chemical composition analysis, crystallinity, UV-vis diffuse reflectance spectroscopy, SEM, DSC, TG, tensile strength, and 13C CP-MAS NMR. The composites were analyzed by SEM, impact strength, and DMA. The SEM images and DMA results showed that the oxidation of sugar cane bagasse fibers followed by reaction with FA favored the fiber/matrix interaction at the interface. The same chemical modification was less effective for curaua fibers, probably due to its lower lignin content, since the reaction considered touches mainly the lignin moiety. The tensile strength results obtained showed that the fibers were partially degraded by the chemical treatment, decreasing then the impact strength of the composites reinforced with them. In the continuity of the present project, efforts has been addressed to the optimization of fiber surface modification, looking for reagents preferably obtained from renewable resources and for chemical modifications that intensify the fiber/matrix interaction without loss of mechanical properties.
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PMID:Thermoset phenolic matrices reinforced with unmodified and surface-grafted furfuryl alcohol sugar cane bagasse and curaua fibers: properties of fibers and composites. 1615 84

The aim of this study was to assess interactions of EDTA and citric acid (CA) with sodium hypochlorite (NaOCl), the indispensable endodontic irrigant. Other chelators were simultaneously evaluated as possible alternatives: sodium triphosphate (STP), amino tris methylenephosphonic acid (ATMA), and 1- hydroxyethylidene-1, 1-bisphosphonate (HEBP). Available chlorine was titrated in chelator-NaOCl solutions. All chelators other than HEBP and STP caused an almost complete, immediate loss of available chlorine in solution. Atomic absorbtion spectrometry and SEM evaluation of root canal walls of instrumented teeth indicated that NaOCl had no negative effect on calcium-complexing ability of chelators. STP was too weak a complexing agent to warrant further studies. Finally, CA-, EDTA-, and HEBP-NaOCl mixtures were evaluated for their antimicrobial capacity. Again, EDTA and CA negatively interfered with NaOCl, while HEBP did not.
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PMID:Chelation in root canal therapy reconsidered. 1624 26

Formation and aggregation of photolytic gold nanoparticles at the surface of chitosan (CTO) films have been investigated. When thin films of chloroauric acid salt of CTO were irradiated with UV light in wet air at room temperature for 10 min, gold nanoparticles of approximately 10 nm size are formed at the film surface. Detailed X-ray photoelectron spectroscopy (XPS) study and field emission type scanning electron microscopy (FE-SEM) observation have been carried out to characterize gold nanoparticles at the film surface. The shift of Au(4f) peak to the higher energy side and broadening of full width at half-maximum in the XPS spectrum are the direct evidence of the existence of gold atoms and small clusters in the early stage of photolysis. According to FE-SEM observation, growth in the particle diameter and aggregation of nanoparticles were observed after prolonged irradiation, and, finally, the film surface was densely covered with gold particles of 20-100-nm size. Gold atoms and clusters could move in the film and precipitate to the irradiated surface. Chemical composition analysis further suggests that gold particles at the surface are covered with an ultrathin CTO layer, which is partly oxidized by oxygen and chlorinated by chlorine during photochemical reactions.
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PMID:Aggregation of photolytic gold nanoparticles at the surface of chitosan films. 1645 10

In the present study, water was circulated in a simulated dental unit water line with electrifying a small current. The morphology of the biofilm developed on inner surface of the water line and the number of heterotrophic bacteria were investigated to elucidate the effect of a low level electric current on the biofilms formation associated with bacteria reproduction. Destruction and malconformation of biofilms by electrification was observed using SEM, in addition to deformation and hypertrophy of the bacteria. By naked eye observation, small pieces, which were possibly exfoliated biofilms, were detected in electrified water. While an adherent, yellow gel was demonstrated on the inner surface of the water line without electrification. With electrification, the number of bacteria decreased during the first week, however the bacteria increased gradually after that. The number of bacteria without electrification was consistently greater than that with electrification and the difference was statistically significant (P<0.05). The predominant bacteria were identified as Sphingomonas paucimobilis. The excess chlorine levels decreased to a minimum value within one week. The small current appeared to have effects on biofilm formation of heterotrophic bacteria that resulted in enhanced chlorine sterilization of dental unit water. Thus, electrification has considerable potential for the extermination of bacterial biofilms in dental unit water lines.
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PMID:Effects of a small electric current on sterilization of a dental unit water line. 1691 72

The sorption mechanism of Ru3+ ions on hydroxy (HAp), carbonate (CO3HAp), and fluor apatites (FAp) has been studied in detail. Ru apatites were obtained by reaction of the apatites with RuCl3 in aqueous solution. The structure and composition of the ruthenium-modified apatites were studied by several techniques: elemental analysis, XRD, EXAFS, IR, NMR, SEM-EDS, TEM, and thermal analysis. The amount of Ru in the modified apatite varies from 7.8 to 10.5 wt% and is not related to the initial composition or the specific surface area of the apatite. The different characterization techniques show that in the Ru-modified apatites Ru is surrounded by six oxygen atoms and do not contain any chlorine. For Ru-HAp and Ru-CO3HAp the new phase is amorphous whereas it is crystalline for FAp. The catalytic oxidation ability is higher for Ru-HAp and Ru-CO3HAp compared to Ru-FAp apatite in the oxidation of benzylic alcohol.
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PMID:A new glance at ruthenium sorption mechanism on hydroxy, carbonate, and fluor apatites: Analytical and structural studies. 1702 13

In this study, 2-amino-4-chloro-6-hydroxy-s-triazine (ACHT) was synthesized through controlled hydrolysis of 2-amino-4,6-dichloro-s-triazine (ADCT). A simple pad-dry-cure approach was employed to immobilize ACHT onto cellulosic fibrous materials. After treatment with diluted chlorine bleach, the covalently bound ACHT moieties were transformed into chloromelamines. The structures of the samples were fully characterized with NMR, UV/VIS, DSC, TG, iodometric titration and elemental analyses. The chloromelamine-based fibrous materials provided potent, durable, and rechargeable biocidal functions against bacteria (including multi-drug resistant species), yeasts, viruses, and bacterial spores. SEM studies demonstrated that the new fibrous materials could effectively prevent the formation of biofilms, and controlled release investigations in vitro suggested that the biocidal activities were bioresponsive. Biocidal mechanisms of the chloromelamine-based fibrous materials were further discussed.
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PMID:Biocidal efficacy, biofilm-controlling function, and controlled release effect of chloromelamine-based bioresponsive fibrous materials. 1718 37

Upon chlorine bleach treatment, amino groups in chitosan were transformed into N-halamine structures. The transformation was confirmed by UV/VIS, XPS, DSC, and TGA evaluation and iodimetric titration. The N-halalmine-based chitosan provided total kill of 10(8)-10(9) colony forming units (CFU/mL) of E. coli (gram-negative bacteria) and S. aureus (gram-positive bacteria) in 10 and 60 min, respectively. SEM observations demonstrated that the chlorinated chitosan effectively prevented the formation of bacterial biofilms. The antimicrobial activity and bio film controlling function were stable for longer than 1 month; when the functions were lost due to extensive use and/or prolonged storage, they could be readily recharged by another bleach treatment. The antimicrobial mechanism was also discussed.
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PMID:N-halamine-based chitosan: preparation, characterization, and antimicrobial function. 1768 58

Reactions of representative lead (II) solid phases (hydrocerussite, cerussite) with chlorine were examined in this study. Chlorine consumption profiles for these solids exhibited a lag phase, during which little consumption of chlorine occurred, and an ensuing rapid reaction phase. The durations of these phases were affected by the pH, carbonate, and chlorine concentrations. SEM and XRD data showed that hydrocerussite started to be transformed into cerussite during the lag phase. Kinetic analysis indicated that only the protonated form of HClO drives the autocatalytic oxidation step, which is mediated by dispersed PbO2 crystals. The rate of the noncatalytic oxidation decreased with the increase of carbonate due to the formation of unreactive surface carbonate Pb(II) complexes.
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PMID:Investigation of the kinetics and mechanisms of the oxidation of cerussite and hydrocerussite by chlorine. 1852

This study presents the results from investigation of ash deposition characteristics of a high ash and sulfur content lignite co-fired with three types of biomass (olive residue, 49 wt%; hazelnut shell, 42 wt%; and cotton residue, 41 wt%) in 0.3 MW(t) Middle East Technical University (METU) Atmospheric Bubbling Fluidized Bed Combustion (ABFBC) Test Rig. Deposit samples were collected on an air-cooled probe at a temperature of 500 degrees C. Samples were analyzed by SEM/EDX and XRD methods. The results reveal that co-firing lignite with olive residue, hazelnut shell and cotton residue show low deposition rates. High concentrations of silicon, calcium, sulfur, iron, and aluminum were found in deposit samples. No chlorine was detected in deposits. Calcium sulfate and potassium sulfate were detected as major and minor components of the deposits, respectively. High sulfur and alumina-silicate content of lignite resulted in formation of alkali sulfates instead of alkali chlorides. Therefore, fuel blends under consideration can be denoted to have low-fouling propensity.
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PMID:Investigation of ash deposition in a pilot-scale fluidized bed combustor co-firing biomass with lignite. 1876 13


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