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Background: The aim of the present study was to investigate qualitatively and quantitatively the elution of substances from polyester-urethane (Invisalign™) aligners and resin composite attachments (Tetric EvoFlow) in vivo. Methods: Patients (n= 11) treated with the aligners and attachments (16 per patient, without other composite restorations) for an average of 20 months, who were planned for attachment removed were enrolled in the study. Patients were instructed to rinse with 50 mL of distilled water upon entry and the rinsing solution was collected (before removal). Then, the attachments were removed with low-speed tungsten carbide burs for adhesive residue removal, a thorough water rinsing was performed immediately after the grinding process to discard grinding particle residues, and subsequently, after a second water-rinsing the solution was collected for analysis (after removal). The rinsing solutions were analyzed for targeted (LC-MS/MS: Bis-GMA, DCDMA, UDMA, BPA) and untargeted (LC-HRMS: screening of leached species and their degradation products) compounds. Results: Targeted analysis revealed a significant reduction in BPA after attachment removal (4 times lower). Bis-GMA, DCDMA, UDMA were below the detection limit before removal but were all detectable after removal with Bis-GMA and UDMA at quantifiable levels. Untargeted analysis reviled the presence of mono-methacrylate transformation products of Bis-GMA (Bis-GMA-M1) and UDMA (UDMA-M1), UDMA without methacrylate moieties (UDMA-M2), and 4-(dimethylamino) benzoic acid (DMAB), the degradation product of the photo-initiator ethyl-4-(dimethylamino) benzoate (EDMAB), all after attachment removal. Several amino acids and endogenous metabolites were also found both before and after removal. Conclusions: Elevated levels of BPA were traced instantaneously in patients treated with Invisalign™ and flowable resin composite attachments for the testing period. BPA was reduced after attachment removal, but residual monomers and resin degradation products were found after removal. Alternative resin formulations and attachment materials may be utilized to reduce eluents.

To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L−1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a(Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl athan Boreal lakes, where the temperature anomaly from the long‐term average, during a summer heatwave was the highest (+4°C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient‐rich lakes than nutrient concentrations and surface temperature.

In this paper, the design and fabrication of a liquid conductivity sensor based on AgPd paste will be described. The device was designed in a four-electrode configuration on a 10 x 25 mm2 96% Al2O3 substrate. The distance between the two driving electrodes was 4 mm, whereas the distance between the two measuring electrodes was 2 mm.The device was also integrated with a Ruthenium based temperature sensor printed on the backside of the substrate. Initial characterisation showed that the conductivity sensor has a measured sensitivity and cell constant of 1.67 cm and 0.51 cm-1, respectively, when a frequency of 1 kHz square wave input was appliedto the driving electrodes. Sensor’s respond variation against temperature was measured around 27.89 μS/°C, corresponding to 2.22 temperature compensation value for salt solution. The results showed a stable response over 5 days measurement cycle, indicating the sensor’s potential for field water quality monitoring application.

Gas sensor performance is strongly influenced by the crystal structure, composition and morphology of the material used. In this paper, structural and morphological analysis of nanocomposite SnO2-Graphene synthesized by Sol-Gel method with the composition of 1:1, 1:2, 1:3 will be described. Analysis of the morphology and structure of nanocomposite SnO2-Graphene is investigated using XRD, SEM and TEM with the purpose of obtaining the crystal structure, morphology, composition and size of the resulting particles. The XRD results showed that the formation of the crystalline phase can be recorded at 2θ = 26.64; 34.2; 51.92, where the results of SEM show that the nanomaterial SnO2 has tetragonal structure while the graphene has hexagonal structure. The nanocomposite SnO2-Graphene has nanorod pattern. Furthermore, the surface analysis using TEM of nanocomposite SnO2-Graphene shows that the surface has the rod diameter in the range of 5-8 nm. The unique nanopattern of SnO2-Graphene will have potential applicability as the sensing material for CO gas sensor.

Microcystins are cyclic heptapeptide toxins produced by a number of genera of cyanobacteria. They are ubiquitous in bodies of water worldwide and pose significant hazard to human, plant, and animal health. Microcystins are primarily hepatotoxins known to inhibit serine-threonine phosphatases leading to the disruption of cascade of events important in the regulation and control of cellular processes. Covalent binding of microcystins with phosphatases is thought to be responsible for the cytotoxic and genotoxic effects of microcystins. In addition, microcystins can trigger oxidative stress in cells resulting in necrosis or apoptosis. Their cyclic structure and novel amino acids enhance their stability and persistence in the environment. Humans are primarily exposed to microcystins via drinking water consumption and accidental ingestion of recreational water. Recreational exposure by skin contact or inhalation to microcystins is now recognized to cause a wide range of acute illnesses which can be life-threatening. Microcystins are primarily degraded by microorganisms in the environment, while sunlight can cause the isomerization of the double bonds and hydroxylation in the presence of pigments. Attempts to utilize these organisms in sand and membrane filters to treat water contaminated with microcystins showed complete removal and detoxification. Conventional water treatment processes may not fully eliminate microcystins when there are high levels of organic compounds especially during harmful bloom events. Combination of conventional and advanced oxidation technologies can potentially remove 100 of microcystins in water even in turbid conditions. This review covers selected treatment technologies to degrade microcystins in water.

Uniform silver nanoparticles were obtained upon the reduction of silver ions by reduced polyoxometalates POMs by simple mixing at room temperature. Control of the size and the dispersity of silver nanoparticles was achieved by rate control. Faster reduction of Ag+led to smaller and more uniform silver nanoparticles, suggesting that the rate of Ag+reduction strongly affects the initial nucleation of silver particles. A faster rate is achieved by either i increasing the concentration of the reducing reagent reduced POM or, more interestingly ii selecting POMs having appropriate more negative redox potentials: different POMs with increasing negative reduction potential or the same POM with more electrons accumulated on it. The rates of Ag+reduction parallel the more negative reduction potential for POMs according to the series H2W12O407–> SiW12O405–> P2W18O628–> P2W18O627–> P2Mo18O6210–> P2Mo18O628–= 0. This precise redoxcontrol is summarized in a log kE0 electrochemicallike behavior, in alliance to a “soluble cathode” behavior of POMs, which leads to more uniform particles than those obtained with conventional electrochemistry. Alternatively, the concentration of silver ions influences the size of the particles obtained: increasing the amount of Ag+leads to larger nanoparticles.© WileyVCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008

Τhe polyoxometalate anions (POM) PW12O403-and SiW12O404-are proposed as efficient photocatalysts for the reductive degradation of the azo dyes Acid Orange 7 (AO), Naphthol Blue Black (NB) and Disperse Blue 79 in aqueous or ethanol solutions. The process involves absorption of light by polyoxometalates, oxidation of an organic sacrificial electron donor, for instance propan-2-ol or ethanol, and the subsequent reductive destruction of the azo dye by reduced POM with the concomitant recycling of the POM catalyst to the oxidized form. Preliminary results show that the dyes are reduced to aromatic amine derivatives. Increase of catalyst and/or propan-2-ol concentration accelerates the photodegradation of the dyes until a saturation value, while an optimum concentration of the added dye is usually required, due to an inner filter effect. The kind of POM catalyst dictates the efficiency of dye decoloration, following the order PW12O403-> SiW12O404-in one-pot photolysis experiments ((dye/propan-2-ol or ethanol/POM). The POM that is more efficient in photooxidizing the organic electron donor is also more efficient in reducing the azo dye due to the greater amounts of reduced catalyst that are formed. The presence of electron scavengers suppresses the degradation rate of dyes according to the trend Cu2+> O2> Ni2+.

Purpose: The purpose of this study was to estimate the degree of cure and monomer leaching of a light-cured and a chemically cured (no-mix) adhesive and to assess their biologic properties. Material: The degree of cure of adhesive specimens prepared with a procedure identical to the clinical bonding process was assessed by infrared spectroscopy. The adhesives were then immersed in normal saline solution for 2 months, and the residual monomer leached from the adhesives was quantitatively and qualitatively analyzed by liquid chromatography. The effect of the immersion media on human gingival fibroblasts' viability and proliferation was also evaluated with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and deoxyribonucleic acid (DNA) synthesis assays, respectively. The results were analyzed by analysis of variance and Tukey test (@a = .05). Results: No difference was found between the 2 adhesives with respect to their degree of cure and the amount of triethylene glycol dimethacrylate released; no diglycidyl dimethacrylate monomer was detected in the eluent. However, significant qualitative changes in the composition of the substances eluted from the 2 adhesives were observed. Conclusions: Whereas no cytotoxic effect was shown for either immersion media, a moderate reduction in the DNA synthesis was obtained by both adhesives, implying a minor cytostatic effect. Further research is required to assess the long-term biologic properties of adhesives, including potential estrogenic action.

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We demonstrate that two large categories of compounds, namely, polyoxometallates (produced by acid condensation of mainly tungstates and/or molybdates) and aggregates of various metal oxides (formed by stirring, sonication etc) have similar properties. Emphasis is given to the photocatalytic properties of the two systems. The various steps in the photocatalytic cycles are described and several examples, from both systems, have been used to demonstrate that their photocatalytic performance is similar in terms of the overall mechanism of photodecomposition of organic compounds, the intermediate species involved and the final photodegradation products (i.e., CO₂, H₂O and inorganic anions).

The excited state of polyoxometalates, (POM) arising from absorption of light at the O→M charge transfer (CT) band (near-VIS and UV light), is a powerful oxidizing reagent. The oxidizing ability is manifested, mainly, through formation of OH radicals arising from the reaction of the excited POM with adsorbed water. The currently accepted mechanism of H-abstraction as the initial reaction of excited POM with organic substrates (mainly alcohols) is modified by addition of one more step that involves the formation of OH radicals which, as is well known, react with organic substrates, mainly alcohols, by H-abstraction. In view of the formation of OH radicals, and the high oxidizing ability of the excited POM, the photochemical selective oxidation of organic substrates, reported so far, in aqueous solutions, should be considered with reservation. Propan-2-ol is, indeed, selectively oxidized to propanone in the presence of PW12O403-. The selectivity is, however, a kinetic phenomenon rather than a thermodynamic one. Both photoreactions, as is the case with numerous other organic compounds, give, as final products, CO2 and H2O.

Opaque nanostructured glass-supported TiO2films were prepared from a commercial and a laboratory synthesised precursor, respectively. Qualitative film analysis was performed with atomic force microscopy (AFM), and surface parameters such as average grain diameter, roughness exponent and fractal dimension were determined. The TiO2surfaces present important roughness due to the large aggregates formed by the interconnected TiO2particles. Fractal dimension was found to range between 2.100 and 2.450, depending on the scanned range and the preparation method. The photocatalytic activity of the films towards the degradation of 2,4-dichlorophenol in acidic aqueous solutions has been investigated. The organic pollutant undergoes effective photodegradation upon photolysis with UV/near visible light. The film morphology, surface characteristics and efficiency remained intact after use. Comparison of the film activities showed that the films prepared from a commercial colloid possess a better photocatalytic performance than the sol-gel films and this can be understood in terms of their smaller particle size, higher roughness and specific surface area.

Photolysis of polyoxometalates at the oxygen to metal charge transfer bands, at the near visible and UV areas, in the presence of a great variety of organic compounds, results in multielectron reduction of polyoxometalates and concomitant oxidation of organic compounds. In the absence of dioxygen, photolysis accumulates electrons on polyoxometalates, moving the redox potential to more negative values, until the reduced catalyst is able to deliver its electrons to H+. At this point, a steady state is produced at which the rate of photoreduction of polyoxometalate is matched by its rate of reoxidation by H+ (H2-evolution). The presence of dioxygen has the following results: (a) It reoxidizes very fast and effectively and photoreduced polyoxometalate, accelerating the photocatalytic cycle by an order of magnitude, and (b) its activation by the reduced catalyst provides, usually, an extra step in which further oxidations of a variety of organic compounds have been obtained.

Photolysis of lindane in aqueous solution, using near-visible and UV light (λ >320 nm) and in the presence of the polyoxometallate PW12O40^3-, results in its conversion to CO2 and HCl. Initial photodecomposition takes place within a few minutes both in the presence and absence of dioxygen. The effective mineralization in the absence of dioxygen suggests that OH radicals act as the primary oxidant in this case.

Polyoxometallates act as electon relays in a photocatalytic process that involves POM/S/Mn+ (POM=polyoxometallates PW₁₂O₄₀^3-, SiW₁₂O₄₀^4- and P₂Mo₁₈O₆₂^6-; S=organic substrate and Mn+=metal ions Ag⁺, Cu²⁺, Pd²⁺ and Ni²⁺). By a suitable choice of POM and, to a lesser extent, organic substrate, selective photocatalytic reduction of metal ions in aqueous solutions can be achieved.

In this study, a new clean up method was developed for the routine multiresidue determination of organochlorine pesticide residues in honey. The analytical procedure requires sample extraction with methanol, followed by a clean up step through a C18 Sep-Pak cartridge. Finally, pesticides are eluted with hexane. The determination of organochlorine pesticide residues was performed by capillary gas chromatography with electron capture detection. The mean recoveries of 18 organochlorine pesticides were estimated at various concentrations and found very efficient in most cases. The detection limits were found to be between 0.05 and 0.20 µg kg–1.

Polyoxometallates (POM), i.e., metal oxide clusters of mainly tungsten are effective homogeneous photocatalysts for the mineralization of organic pollutants. POM are, at least, as effective as the well studied TiO2. OH⋅radicals formed by the reaction of the photo-excited polyoxometallates with H2O, appear to play a key role in the process. In this study, the photocatalytic activity of POM have been tested on some diversified pesticides of interest such as lindane, bentazone and fenitrothion to determine the feasibility of decontamination of aqueous solutions from these pollutants. The results show that aqueous solutions containing the above pesticides, upon photolysis in the presence of polyoxotungstates undergo effective degradation to CO2, H2O and the corresponding inorganic anions. The intermediates identified give rise to complicated degradation mechanisms prior to mineralization. The characteristic reactions that take place consist of hydroxylation, H-abstraction, dehalogenation, denitration, desulfurization, breaking of the C-C bond etc.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Polyoxometalate anions (POM), resulting from the condensation of tungstate anions in strongly acidified solutions, can absorb efficiently light in the UV-near Vis region.The produced excited state is a very powerful oxidative reagent which can, mainly via OH radical attack, oxidize and mineralize a great variety of organic pollutants in aqueous solutions, while the photocatalytic circle is closed by reoxidation of the reduced POM, mainly, by O2. Metal ions can also serve as oxidants and close the photocatalytic cycle. In the process metal ions are reduced, precipitated and removed from the solution. Thus photocatalytic treatment for decontamination of waste waters from both organic and inorganic pollutants (metal ions) can be, in principle, achieved. POM+S→hνPOMred+SoxPOMred+Mn+→POM+Mred Atrazine, a widely used herbicide with s-triazine structure, is photodecomposed to cyanuric acid in presence of SiW12O404- in aqueous solutions. However, no precipitation of metal ions is obtained when atrazine is the sole organic substrate in aqueous solutions. The low solubility of atrazine produces insufficient concentration of reduced POM to cause precipitation.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.