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

The electrocatalytic hydrodechlorination of 4-chlorobiphenyl on palladized nickel foam with high porous structure in an aqueous solution containing MeOH, bromide of hexadecyltrimethylammonium (CTAB), sodium acetate, and acetic acid were investigated in a membrane-separated flow-through cell. The Pd/Ni foam electrode was prepared by electroless deposition method, on which the Pd particles dispersed finely over Ni foam surface indicated by SEM-EDX analysis. The effects of current density, organic cosolvent, initial concentration, temperature, and flow rate on the hydrodechlorination of 4-chlorobiphenyl were examined. Methanol was among the best cosolvents and was used in preferential concentration of 50 vol%. Moderate current density (e.g., 2.23 mA cm(-2)), relatively high initial concentration, temperature, and flow rate were beneficial to improve the hydrodechlorination of 4-chlorobiphenyl. The current efficiencies for the conversion of 1mM 4-MCB decreased with increasing current density and range from 37.2% at 0.74 mA cm(-2) to 14.1% at 5.21 mA cm(-2) after 20 min electrolysis cut. Under the optimized conditions, 1mM of 4-MCB could be removed rapidly with the rate of 94.6% after 2h electrolysis, which gave current efficiencies and energy consumptions in range of 8.1-24.6% and 1.7-5.2 kW h kg(-1), respectively.
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PMID:Electrocatalytic hydrodechlorination of 4-chlorobiphenyl in aqueous solution using palladized nickel foam cathode. 1714 Dec 95

A novel composite able to remove hexavalent chromium Cr(VI) from aqueous solutions was obtained by adding the silica precursor tetraethoxysilane (TEOS) to the hexadecyltrimethylammonium bromide (CTAB) microemulsion-based gel. A physical characterization of the new matrix revealed high stability of the silica gelatin composite in water at high temperatures and at neutral pH. Good efficiency in removing chromate from neutral solutions was also demonstrated by the adsorption kinetics. In particular, the adsorption data of chromate obtained with the CTAB-silica gelatin composite at 25 degrees C and pH 7.5 are described by the Freundlich isotherm model. The specific role of CTAB in the silica gelatin composite was also evaluated by comparing the kinetics of the anionic AOT-silica gelatin composite to the CTAB one. The data collected clearly showed that the positively charged surfactant was necessary to efficiently adsorb Cr(VI) from aqueous solutions. SEM and pulsed gradient spin-echo NMR analysis of the composite demonstrated that the silicon is well assembled in the gelatin network, in which water molecules maintain a high mobility. The diffusion coefficient of water in this system was shown to remain close to the value of pure water. Finally, X-ray analyses of the elemental content in the CTAB-silica gelatin composite indicated no difference in terms of percentage of silica distributions in different areas of the matrix and suggested that chromium adsorption could take place in internal areas.
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PMID:Removal of chromate from water by a new CTAB-silica gelatin composite. 1734 33

Crystalline vanadium pentoxide with hierarchical mesopores was synthesized by using a CTAB/BMIC cotemplate (CTAB = cetyltrimethylammonium bromide, BMIC = 1-butyl-3-methylimidazolium chloride). The material was fully characterized by SEM, TEM, N2 adsorption-desorption, XRD, XPS, and CV methods. By elaborate adjustment of the template proportions, the distribution and size of the hierarchical pores were tuned successfully. CTAB cationic surfactant contributed more to the larger mesopores, whereas BMIC ionic liquid was beneficial in forming the smaller nanopores. The vanadium-containing anions combined with CTA+ micelles and BMI+ rings through electrostatic interactions. The CTA(+)-O(VO)O(-)-BMI(+) entities built up an orderly array, which finally formed the hierarchical mesoporous framework during thermal treatment. The mesoporous vanadium pentoxide directed by the cotemplate of CTAB/BMIC = 1:1 showed many orderly crystalline structures and demonstrated a large capacitance (225 F g(-1)); it is thus a promising material for electrochemical capacitors. Two alternative solutions to the disappearance of capacitance due to insertion of K+ are proposed in view of possible future applications.
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PMID:Crystalline vanadium pentoxide with hierarchical mesopores and its capacitive behavior. 1744 Nov 11

The corrosion resistance of AISI 304 stainless steel (AISI 304 SS) and manganese stainless steel (low-nickel SS) brackets in artificial saliva was investigated. The cytotoxic effects of their corrosion products on L929 cell culture were compared by two assays, crystal violet, to evaluate cell viability, and MTT (3-[4,5-dimethylthiazol-2-yl]2,5-diphenyltetrazolium bromide), for cell metabolism and proliferation. The atomic absorption spectroscopic analysis of the corrosion products demonstrated that nickel and manganese ion concentrations were higher for the AISI 304 SS-bracket immersion solution as compared with the low-nickel SS brackets. Scanning electron microscopy and energy-dispersive spectroscopy demonstrated less corrosion resistance for the AISI 304 SS brackets. Although none of the bracket extracts altered L929 cell viability or morphology, the AISI 304 SS-bracket extracts decreased cellular metabolism slightly. The results indicated that the low-nickel SS presents better in vitro biocompatibility than AISI 304 SS brackets. Abbreviations used: AISI, American Iron and Steel Institute; EDS, energy-dispersive spectroscopy; OD, optical density; ISO, International Organization for Standardization; MTT, (3-{4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; NiSO(4), nickel sulfate; SEM, standard error of the mean; WHO, World Health Organization; and TNF, tumor necrosis factor.
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PMID:In vitro evaluation of corrosion and cytotoxicity of orthodontic brackets. 1745 65

This study mainly deals with cell transfection and cytotoxicity for PEI(10kD)-PBLG, a novel cationic copolymer, to observe its potential as a gene carrier. Size measurement and SEM were used to show the modality of the PEI-PBLG/pDNA complexes. Cytotoxicity of PEI (10kD)-PBLG was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay and compared with PEI(25kD)-PBLG, PEI(10kD), and PEI(25kD). Furthermore, pEGFP that can express the enhanced green fluorescent protein was chosen as a reporter to observe the transfection efficiency directly. Then, PEI (10kD)-PBLG/pEGFP complexes were transfected into several cell lines, such as Hela, COS-7, Vero-E6, and ECV-304, and effects of the transfection conditions were evaluated. The efficiencies were measured by FACS. Size measurement of complex particles indicated that PEI-PBLG/pDNA tended to form smaller nanoparticles compared with PEI/pDNA. The representative size of the PEI(10kD)-PBLG/pDNA complex was approximately 100 - 200 nm. SEM images showed that the particles were condense and compact. This can be suitable for their entry into cells. Cytotoxicity studies suggested that PEI (10kD)-PBLG had considerably lower toxicity than the other three materials. In the transfection tests, PEI (10kD)-PBLG/pDNA complexes could be transfected into all the cell lines that were tested. These provided the highest level of EGFP expression (45.02%) in Hela cells, which was considerably higher than that of PEI(10kD)/pEGFP (29.16%). Being less affected by the serum during transfection, PEI-PBLG/pDNA complexes offered greater biocompatibility than PEI. PEI-PBLG copolymer reduces the cytotoxicity of PEI, improves the transfection efficiency, and offers greater biocompatibility than PEI. It shows considerable potential as an efficient nonviral carrier for gene delivery.
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PMID:[Transfection with a novel cationic gene carrier: PEI-PBLG]. 1746 Aug 93

A probe array with nano-scale tips, integrated into a micro-fluidic channel was developed for the capture and lysing of small number of vaccinia virus particles using dielectrophoresis. The nano-scale probe array was fabricated in Silicon on Insulator (SOI) wafers, and sharpened with repeated oxidation steps. The gap between each probe ranged from 100 nm to 1.5 microm depending on fabrication parameters. The probe array was used to capture vaccinia virus using positive dielectrophoresis (DEP) from a flow within the microfluidic channel, and then the same probe array was used to apply high electric field to lyse the virus particles. It was shown that under electric field strengths of about 10(7)V/m, the permeability of ethidium bromide into the vaccinia virus particles was increased. Upon SEM analysis, the particles were found to be damaged and exhibited tubules networks, indicating disintegration of the virus outer layer. In addition, elongated strands of DNA were clearly observed on the chip surface after the application of the high electric field, demonstrating the possibility of electrical lysis of virus particles.
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PMID:Electrical capture and lysis of vaccinia virus particles using silicon nano-scale probe array. 1761 69

Quaternized chitosan/layered silicate nanocomposite was prepared by simple solution-mixing in aqueous media. Montmorillonite (MMT) modified with cetyltrimethyl ammonium bromide was used as an organically modified layered silicate. XRD and TEM analyses respectively confirmed that silicate layers of MMT were intercalated and nicely distributed in quaternized chitosan matrix in despite of the high content of MMT (25-50 wt %). The interactions between the quaternized chitosan macromolecules and MMT in aqueous media were analyzed using FTIR, XRD, and zeta-potential measurements. Antimicrobial studies showed that the nanocomposites could strongly inhibit the growth of a wide variety of microorganisms, including Gram-positive bacteria, Gram-negative bacteria, and fungi; more importantly, they exhibited good antimicrobial capacity in whichever medium, in weak acid, water, or weak base. As the amount of MMT increased, the nanocomposites had better inhibitory effect on microorganisms, especially Gram-positive bacteria. The lowest minimum inhibition concentration (MIC) value of the nanocomposites against Staphylococcus aureus and Bacillus subtilis were less than 0.00313% (w/v) under all the conditions. The adsorption action of MMT on bacteria was simply discussed via SEM images. The results revealed that the strong antimicrobial of the nanocomposites may be attributed to the fine dispersion and the interaction between quaternized chitosan and MMT.
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PMID:Preparation, characterization, and antimicrobial activity of quaternized chitosan/organic montmorillonite nanocomposites. 1761 81

Ce-containing MCM-41 materials were prepared via a direct, nonhydrothermal method at room temperature from tetra-ethoxysilane, n-hexadecyl trimethyl ammonium bromide, ammonia solution, and cerium(IV) ammonium nitrate precursors. Composite materials containing the nominated ratios of 5 and 10% (w/w) CeO2/MCM-41 were targeted. The obtained materials were investigated by TGA, DSC, FTIR, diffuse reflectance UV-vis, XRD, N2 adsorption/desorption isotherms, and SEM. Results indicated the insertion of cerium ions in tetrahedral environment in the framework of MCM-41. BET surface area amounting to 824 and 726 m2/g; total pore volume amounting to 0.427 and 0.515 cm3/g; and narrow pore size distribution maximizing at 22.5 and 23.7 A, respectively were obtained for the 5 and 10% CeO2/MCM-41 calcined composites. SEM showed a spherical type morphology for the composites which is rather similar to their blank MCM-41, and no clear ceria aggregates were observed on the external surfaces of composites spherical particles. Thus, the adopted method allows the persistence of MCM-41 texture with cerium inserts in the framework of MCM-41 and/or forms finely divided ceria nanoparticles on the wall of MCM-41 materials. Moreover, stabilization of any formed ceria nanoparticles was attributed to the short nonintersecting porous nature of MCM-41 matrix, which hinders their aggregation upon calcinations.
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PMID:Cerium modified MCM-41 nanocomposite materials via a nonhydrothermal direct method at room temperature. 1771 29

BF2 complexes of aryl-substituted dipyrrolyldiketones (3a-c, 5a-d) have been synthesized by the condensation of arylpyrroles obtained by Suzuki cross-coupling reactions with malonyl chloride, followed by treatment with BF3.OEt2. The binding constants (Ka11) of the BF2 complexes (3a-c) for various anions (Cl-, Br-, CH3CO2-, H2PO4-, and HSO4-) in CH2Cl2 decrease in the order Ph (3a) > o-tolyl (3b) > 2,6-Me2Ph (3c), possibly because of differences in the planarity and the number of interacting o-CH units at the binding sites. Aryl-substituted receptors exhibit a [1+1] binding mode with Cl- as well as a [2+1] binding mode under conditions of high concentration and low temperature, as suggested by 1H NMR studies in CD2Cl2. These receptors, especially phenyl-substituted (3a) and o-tolyl (3b), exhibit drastic colorimetric and fluorescent changes in the presence of F- due to extended pi-conjugation, as compared to 2,6-dimethylphenyl (3c) and the previously reported derivatives (1a-c). Aryl-substitution at the alpha-positions of pyrrole is an excellent means for the introduction of various substituents at the periphery of the anion receptors. For example, derivatives with long alkoxy chains at 3,4,5-positions of the substituent aryl rings (5b-d) afford emissive gel structures in hydrocarbon solvents, such as octane, based on the stacking of slipped H- and J-aggregates at the core pi-plane. The structural organization of the supramolecular gels was investigated by AFM, SEM, and XRD measurements as well as by considering the solid-state packing of crystalline derivatives. The slow transformation of the gel to the solution phase by the addition of various anions, possibly except for F-, is correlated with the unique properties of these acyclic receptors where inversions of pyrrole rings are required for anion binding. Boron complexes of 1,3-dipyrrolyl-1,3-propanediones with aryl-substituents, as a new class of acyclic anion receptors, have shown efficient binding due to the interacting o-CH units and, in the case of the derivative with long aliphatic chains, afforded the emissive supramolecular organogels using stacking of core pi-planes controlled by external chemical stimuli.
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PMID:Aryl-substituted C3-bridged oligopyrroles as anion receptors for formation of supramolecular organogels. 1792 82

Al-MCM-41 mesoporous sieves were synthesized at the ambient temperature by using TEOS as silica source, Al(NO)3 x 9H2O as Al source, and cetyl trimethylammonium bromide as templating agent. The framework and surface structures of the synthesized samples were characterized by XRD, N2-adsorption/desorption isotherms, FTIR and SEM etc. The results showed that the samples were the typical Al-MCM-41 mesoporous sieves with the higher ordered-degree and specific surface area (up to 816 m2 x g(-1)) and the narrower pore diameter distribution. Controlling the highest value of Al/Si with the range of 0.06-0.13, and taking temperature programmed calcination would be beneficial to the formation of the highly ordered Al-MCM-41 mesoporous sieves. The evaluating results showed that the synthesized Al-MCM-41 molecular sieves have a higher catalytic activity for isomerization of endo-tetrahydrodicyclo-pentadiene (endo-TCD) into exo-tetrahydrodicyclo-pentadiene (exo-TCD) and adamantane.
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PMID:[Synthesis and catalytic-isomerization performance of Al-MCM-41 mesoporous sieves]. 1794 16


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