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PubMed1998

Adhesive bonding to dentin with iron (II) perchlorate primers and a tri-n-butylborane-initiated luting agent.

OBJECTIVES: This study was conducted to measure the tensile bond strength of a resin to dentin when the dentin was primed with iron (II) perchlorate modified aqueous 2-hydroxyethyl methacrylate (HEMA) or an iron (II) perchlorate modified commercial self-etching primer (ED primer, Kuraray Co.). METHODS: Bovine dentin surfaces were ground flat and each specimen underwent one of the following two treatments: (1) priming with 2.0 x 10(-6) to 5.0 x 10(-4) mol/g iron (II) perchlorate in aqueous HEMA solutions after etching with 10 wt% phosphoric acid; (2) priming with self-etching primers containing 4.0 x 10(-7) to 2.0 x 10(-4) mol/g iron (II) perchlorate. Each specimen was then bonded to a stainless-steel rod with a luting agent (MMA-TBB resin) consisting of methyl methacrylate (MMA), poly(methyl methacrylate) (PMMA), and tri-n-butylborane (TBB) initiator. Tensile strengths of the bonded tooth specimens were then determined after 1 day immersion in water. Results were analyzed using ANOVA and Duncan's new multiple range test (p < 0.05). RESULTS: Tensile testing revealed the maximum mean bond strengths (22.5 MPa) when the dentin was primed with 2.0 x 10(-4) mol/g iron (II) perchlorate after etching with 10 wt% phosphoric acid aqueous solution. The highest level of bond strength with self-etching primer (19.6 MPa) was achieved using 1.0 x 10(-4) mol/g iron (II) perchlorate. SIGNIFICANCE: These bonding techniques, combining the use of iron (II) perchlorate modified HEMA primers with MMA-TBB resin, are potentially applicable for seating resin-bonded restorations.

Adhesiveness↗
PubMedDate not supplied

Optimization of polymerization conditions of furan with aniline for variable conducting polymers.

A high-throughput multiparameter optimization of chemical oxidative polymerization conditions has been developed for a facile synthesis of furan homopolymers and furan/aniline copolymers using a combinatorial method. The polymerization yield, molecular structure, and properties of the polymers would be optimized against typical polymerization parameters, including oxidant species, medium species, temperature, oxidant/monomer ratio, monomer concentration, dopant concentration, and furan/aniline comonomer ratio. The electrical conductivity, lead ion adsorptivity, chemical resistance, and thermal behavior of the polymers were also elaborated. It is found that only a combination of FeCl(3) and nitromethane as oxidant and medium, respectively, is appropriate for the furan homopolymerization. The homopolymerization yield increases consistently with an increase in the monomer concentration from 0.05 to 0.2 M and the FeCl(3)/furan molar ratio from 0.25 to 1.25. Although the as-prepared polyfuran exhibits very low conductivity, down to 10(-11) S cm(-1), the HCl- and HClO(4)-doped polyfurans possess much higher conductivities of 9.2 x 10(-8) and 2.38 x 10(-5) S cm(-1), respectively. In addition, the conductivity of the furan/aniline copolymer rises steadily with increasing aniline content, although the copolymerization yield shows a minimum at the furan/aniline molar ratio of 60/40, which is evidence of the occurrence of a real copolymerization between the furan and aniline monomers. The difficulty of synthesizing conducting polyfuran could be overcome to some extent by the polymerization in an appropriate condition optimized in this study. Particularly, the difficulty of synthesizing poly(furan-co-aniline) having much higher conductivity than the polyfuran would be largely conquered by chemical oxidative copolymerization of furan with aniline.

Aniline Compounds↗
PubMed2006

Spin-crossover in an iron(III)-bispidine-alkylperoxide system.

The iron(II) complex of a tetradentate bispidine ligand with two tertiary amines and two pyridine groups (L = dimethyl [3,7-dimethyl-9,9'-dihydroxy-2,4-di-(2-pyridyl)-3,7-diazabicyclo nonan-1,5-dicaboxylate]) is oxidized with tert-butyl hydroperoxide to the corresponding end-on tert-butylperoxo complex [Fe(III)(L)(OOtBu)(X)]n+ (X = solvent, anion). UV-vis, resonance Raman, and EPR spectroscopy, as a function of the solvent, show that this is a spin-crossover compound. The experimentally observed Raman vibrations for both low-spin and high-spin isomers are in good agreement with those computed by DFT.

Bridged Bicyclo Compounds, Heterocyclic↗
PubMed1975

Mucoid strains of Pseudomonas aeruginosa: the influence of culture medium on the stability of mucus production.

Mucoid strains of Pseudomonas aeruginosa isolated from the respiratory tract of patients with cystic fibrosis (CF), those obtained from non-CF patients, and those obtained in vitro by the action of phage, were found to be stable in their mucoid colonial form when serially subcultured on deoxycholate-citrate agar. The ability of anionic, cationic and neutral surfactants to stabilise mucus production is described. The possible importance of dipalmitoyl lecithin as a stabilising agent for mucus production in vivo is considered, with particular reference to the role of mucoid P. aeruginosa in CF disease.

Acetylcysteine↗
PubMed1991

Aluminum salts stimulate luminol-enhanced chemiluminescence production by human neutrophils.

Aluminum intoxication is currently thought to play a major role in the development of Alzheimer's disease and in certain pathologic manifestations seen during long-term hemodialysis and aging. The hypothesis that aluminum toxicity is mediated via an increased free radical production was tested by studying the effects of two aluminum and five other metallic compounds on the production of luminol-enhanced chemiluminescence (LECL) by human neutrophils. AlCl3, Al2(SO4)3 and FeCl3 were found to stimulate LECL production by human neutrophils whereas FeCl2, CuCl, CuCl2, AuCl3 were inactive. Metal chelators such as Desferal, EDTA and DETAPA suppressed aluminum-induced stimulation and depressed cell-dependent LECL below basal levels. Sodium azide and Cytochalasin B greatly depressed both basal and aluminum-induced stimulation of LECL production, suggesting that, in this system, most of this stimulation was due to myeloperoxidase. These results suggest that high tissue aluminum concentrations may induce cell-tissue lesions by stimulating local production or release of mediators of tissue damage.

Alum Compounds↗
PubMed2004

Abiotic degradation of pentachloronitrobenzene by Fe(III): reactions on goethite and iron oxide nanoparticles.

Pentachloronitrobenzene is a fungicide that is degraded in anoxic soils and sediments through unknown processes that are often thought to be biologically mediated. The present research describes the kinetics for the abiotic reduction of this compound in aqueous Fe(II)/goethite systems at near-neutral pH values. The results provide evidence for a rate-affecting surface-association process rather than a direct (i.e., kinetically second-order) reaction with an adsorbed Fe(II) species. It is therefore likely that the iron oxide surface participates directly in the reaction. Furthermore, reduction is observed in the apparent presence of trace amounts of suspended iron oxide nanoparticles, formed in situ by the oxidation of Fe(II). Given that Fe(III) colloids and other nanoscale phases may occur in natural sediments, such abiotic reactions could significantly influence the environmental fate of nitroaromatic compounds.

Ferric Compounds↗
PubMed2000

Effect of aluminum on the production of siderophore by Rhizobium sp. (Cicer arietinum).

Rhizobium sp. strain BICC 651 in the presence of 100 microM Al3+ produced a threefold higher level of siderophore than in the control culture under iron limitation during the stationary phase. Al3+ in increasing concentrations resulted in decreased growth, and the effect was alleviated by the addition of iron. Siderophore production decreased gradually in Al3+-treated culture as well as in the control with the addition of increasing concentrations of Fe3+, and at 50 microM Fe3+ the level of siderophore was practically undetectable. The siderophore binds Fe3+ and also Al3+. The outer membrane protein profiles of the bacteria grown in the presence or absence of Al3+ were indistinguishable.

Aluminum Compounds↗
PubMed1994

Probucol scavenged 1,1-diphenyl-2-picrylhydrazyl radicals and inhibited formation of thiobarbituric acid reactive substances.

Probucol is suggested to have antioxidant properties. The direct scavenging action of probucol on hydroxyl radicals, superoxide and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals were examined using electron spin resonance (ESR) spectrometry. Probucol scavenged DPPH radicals dose dependently but showed no effect on hydroxyl radicals and superoxide generated by Fenton reaction and by hypoxanthine-xanthine oxidase system, respectively. It inhibited the formation of thiobarbituric acid reactive substances (TBARS) in rat cortex homogenate induced by ascorbic acid and FeCl2 at low dose, but it increased TBARS formation at high doses. Probucol showed no effect on the carbon centered radicals. Iron injection into the rat cortex, which is an experimental model for traumatic epilepsy, increased TBARS level in the cortex, hippocampus, striatum and cerebellum, but pretreatment with probucol inhibited the increase in these brain parts except for the hippocampus. These results suggest that the antioxidant property of probucol is partly due to its free radical scavenging effect.

Animals↗
PubMed2004

Decolorization of orange II by catalytic oxidation using iron (III) phthalocyanine-tetrasulfonic acid.

Orange II, C.I. Acid Orange 7 (AO7), is oxidatively decolorized via catalytic oxidation by iron(III) phthalocyanine-tetrasulfonic acid (Fe(III)-PcTS) as a biomimetic catalyst and KHSO(5) as an oxygen donor. The nature of the decolorization of AO7 was investigated in the catalyst concentration range of 10-50 microM, in which the initial concentration of AO7 was 417 mg l(-1). A 99.6% decolorization was observed at [KHSO(5)] = 2.5 mM and [Fe(III)-PcTS] = 20 microM after a 3-h reaction period. However, the fact that only 4.9% of the TOC was removed indicated that the conversion to CO(2) was incomplete. The results of a total organic nitrogen analysis of the reaction mixture showed that the nitrogen in the azo chain was mainly converted to N(2) gas. In addition, 38.6% of the AO7 was converted to 1,2-dihydroxynaphthalene, and 21.4% to p-phenolsulfonic acid. These results indicate that the degradation via this catalytic system involves the conversion of AO7 to phenolic compounds, followed by N(2) production. In addition, a Microtox test showed that toxicity of the solution increased as a result of AO7 oxidation using this catalytic system.

Azo Compounds↗
PubMed2005

Sequential polymer dosing for effective dewatering of ATAD sludges.

Dewatering problems associated with the sludge from autothermal thermophilic aerobic digestion (ATAD) of sludge, result in large chemical conditioning costs for effective dewatering. A variety of chemical conditioners were used to improve dewatering, but none of them were able to dewater the sludge as desired at acceptable conditioning doses. It was found that during the digestion process, chemical precipitation of divalent cations occurred. Some of the ATAD sludge colloids were found to have a positive zeta potential and these were thought to be the precipitated divalent cations. Sequential polymer dosing using either iron or cationic polymer, followed by anionic polymer, was found to improve dewatering. The use of anionic polymer is essential and allows the use of smaller amounts of iron or cationic polymer for effective dewatering. The use of the less expensive anionic polymer along with cationic polymers has the potential to make the use of the ATAD process more economical.

Alum Compounds↗
PubMed2000

Antioxidant properties of water extracts from Cassia tora L. in relation to the degree of roasting.

The antioxidant properties of water extracts from Cassia tora L. (WECT) prepared under different degrees of roasting were investigated. The water extracts of unroasted C. tora L. (WEUCT) showed 94% inhibition of peroxidation of linoleic acid at a dose of 0.2 mg/mL, which was higher than that of alpha-tocopherol (82%). Water extracts prepared from C. tora L. roasted at 175 degrees C for 5 min and at 200 degrees C for 5 min exhibited 83% and 82%, respectively, inhibition of linoleic acid peroxidation. This result indicated that the antioxidant activities of WECT decreased with longer roasting time or higher roasting temperature. The IC(50) of WEUCT in liposome oxidation induced by the Fenton reaction was 0.41 mg/mL, which was higher than that of alpha-tocopherol (IC(50) = 0.55 mg/mL). WEUCT also exhibited good antioxidant activity in enzymatic and nonenzymatic microsome oxidative systems. The water extracts of roasted C. tora L. increased in the degree of browning and produced chemiluminescence when compared with the unroasted sample. However, the total polyphenolic compounds of WECT decreased after the roasting process finished. In conclusion, the decrease in the antioxidant activity of water extracts from roasted C. tora L. might have been due to the degradation of Maillard reaction products and the decrease of polyphenolic compounds.

Antioxidants↗
PubMed1992

Subsurface demineralization in dental enamel and other permeable solids during acid dissolution.

Subsurface demineralization of dental enamel during acid dissolution has been reported many times, but its cause remains obscure. At first, the phenomenon was thought to result from the physical structure of enamel. More recent studies have shown that subsurface demineralization occurs in other permeable solids, indicating that there must be more fundamental factors involved in this curious effect. In order for this phenomenon to be investigated, dissolution experiments were carried out by means of real-time scanning microradiography in various systems, including enamel, or aggregates of hydroxyapatite (calcium, strontium, or barium), or hydroxides (calcium or magnesium). These were chosen to discriminate between effects of structure and composition. It was found that it was not possible for the demineralization observed in these systems to be attributed to a common feature. From this, it is concluded that subsurface demineralization in enamel and other mineralized tissues should not be ascribed to a single cause.

Acetates↗
PubMedDate not supplied

Surface geometry of three packable and one hybrid composite after polishing.

This study evaluated the surface quality of four composite materials after polishing with six different polishing techniques. Eighty specimens were made using three packable composites (Definite/Degussa, SureFil/ Dentsply and Solitaire/Heraeus-Kulzer) and one hybrid composite (Herculite XRV/Kerr). Five specimens of each material were polished using flexible Sof-Lex discs. The remaining 75 specimens of each composite were prepared using three finishing protocols: a single 30 microm diamond (n = 25), two finishing diamonds (30/20 microm; n = 25) and a 30 microm diamond followed by a tungsten carbide finishing bur (n = 25). Final polishing of each of the three finishing groups was accomplished with SuperBuff, Diafix-oral, OneGloss, Astropol and HaWe Composite Polishers (n = 5, each). Surface roughness was evaluated quantitatively by laser-stylus profilometry. Average roughness (R(a)) was calculated; statistical analysis of the data was performed with two-way ANOVA and Scheffé post-hoc tests. The polished surfaces were examined qualitatively by SEM. The results showed significant effects on surface roughness from the different composites (p = 0.011) and polishing systems (p < 0.001). After polishing, the Solitaire surfaces (R(a) = 0.72 microm) were smoother than Definite (R(a) = 0.87 microm) and SureFil (R(a) = 0.89 microm) and significantly smoother than Herculite (R(a) = 0.92 microm; p = 0.011). Three of the polishing methods (SuperBuff, Diafix-oral and Astropol) achieved lower R(a)-values than Sof-Lex discs. The polishing quality of the one-step systems SuperBuff and Diafix-oral was strongly affected by the initial finishing protocol.

Aluminum Oxide↗