Increased conversion efficiency in cadmium telluride photovoltaics by luminescent downshifting with quantum dot/poly(methyl methacrylate) films

Commercially available quantum dots have been encapsulated in a poly(methyl methacrylate) film and used as a luminescent downshifting layer on cadmium sulfide/cadmium telluride photovoltaic devices. Application of these films has resulted in a relative improvement to the short‐circuit current of over 4% by I–V measurement, with a significant increase in the contribution of short‐wavelength light resulting in 25% of the current available in this part of the spectrum being captured. The films have been shown to be highly scattering and the associated difficulties this provides to external quantum efficiency measurements have been discussed. A range of optical characterisation techniques, particularly laser beam induced current, have been used to probe the effect the films have on a cadmium sulfide/cadmium telluride device. An alternate methodology for performing external quantum efficiency measurements with the quantum dot films has been proposed. Copyright © 2013 John Wiley & Sons, Ltd.     

Microleakage in class V cavities prepared using conventional method versus Er:YAG laser restored with glass ionomer cement or resin composite

This study evaluated the effect of tooth preparation method (diamond bur vs. Er:YAG laser) on the microleakage levels of glass ionomers and resin composite. Human permanent premolars (N = 80) were randomly divided into two groups (n = 40). Cavities on half of the teeth were prepared using diamond bur for enamel and carbide bur for dentin and the other half using Er:YAG laser. The teeth were randomly divided into four groups according to the restoration materials, namely (a) ChemFil Rock (CFR), (b) IonoluxAC (IAC), (c) EQUIA system (EQA) and one resin composite (d) AeliteLS (ALS) (n = 10 per group). Microleakage (μm) was assessed at the occlusal and gingival margins after dye penetration (0.5% basic fuchsine for 24 h). On the occlusal aspect, while the cavity preparation types significantly affected the microleakage for CFR (p = 0.015), IAC (p = 0.001) glass ionomer restorations, it did not show significant effect for glass ionomer EQA (p = 0.09) and resin composite ALS (p = 0.2). Er:YAG laser presented less microleakage compared to bur preparation in all groups except for EQA. On the gingival aspect, microleakage decreased significantly for CFR (p = 0.02), IAC (p = 0.001), except for EQA where significant increase was observed (p = 0.001) with the use of Er:YAG laser. Microleakage decrease was not significant at the gingival region between diamond bur and Er:YAG laser for ALS (p = 0.663). At the occlusal and gingival sites in all groups within each preparation method, microleakage level was not significant.     

Photoelectrocatalytic determination of NADH in a flow injection system with electropolymerized methylene blue

It was firstly described that a glassy carbon electrode electropolymerized with methylene blue shows an efficient photoelectrocatalytic activity towards NADH oxidation in a phosphate buffer solution (pH 7.0). In order to perform the photoelectrocatalytic determination of NADH in a flow injection analysis (FIA) system, a home-made flow electrochemical cell with a suitable transparent window for the irradiation of the electrode surface was constructed. The currents obtained from the photoamperometric measurements in the FIA system at optimum conditions (flow rate of carrier solution, 1.3 mL min⁻¹; transmission tubing length, 10 cm; injection volume, 100 μL; and constant applied potential, +150 mV vs. Ag/AgCl) were linearly dependent on the NADH concentration and linear calibration curves were obtained in the range of 1.0 × 10⁻⁷–2.0 × 10⁻⁴ M. The detection limit was found to be 4.0 × 10⁻⁸ M for photoamperometric determination of NADH.     

The influence of process parameters on desulfurization of two Turkish lignites by selective oxidation

The chemical desulfurization of two high-sulfur Turkish lignites was investigated using a mixture of hydrogen peroxide in acetic acid. Sulfur removal was measured with respect to particle size, reaction time, reaction temperature and ultrasonic irradiation. In general, all inorganic sulfur and some organic sulfur were removed from these coals under mild conditions. Cayirhan lignite seemed more reactive towards peroxyacedic acid at slightly higher temperatures and longer reaction times, but under these conditions, solubility was high and yields of solid products declined. Reaction time and reaction temperature slightly changed the level of sulfur removal from Gediz lignite. The level of desulfurization was largely independent of the particle size for Gediz lignite, while sulfur removal from Cayirhan lignite seemed dependent of the particle size reaction temperature and reaction time.     

Synthesis and application of phenylcarbamodithioate compound for steel protection

Phenyldithiocarbamate compound has been synthesized and studied as corrosion inhibitor for steel. Dithiocarbamate (DTC) compounds with linear alkyl groups are good inhibitors, but their stability is quite low in acidic solutions. It should be noted that long-term stability is important for practical applications, in order to avoid excess use of chemicals. So, we have synthesized phenyl substituted DTC which offers strong inhibition efficiency and extra stability. This new inhibitor is chemically adsorbed on steel through its DTC group, while the aromatic ring provides extra stability and long-term efficiency. For the assessment of corrosion kinetics, we have utilized potentiodynamic and ac impedance studies; also solution assay analysis was realized with atomic absorption spectroscopy. It was revealed that inhibitor exhibits remarkably high efficiency, even under elevated temperature conditions. At 55 °C temperature conditions, i_corr value decreased from 5050 to 154 μA cm^?2, with the addition of 500 ppm inhibitor. The long-term stability of inhibitor was also tested and 85.93% efficiency was obtained after three days of exposure period for 500 ppm concentration.     

Preparation of compatible blends of poly(methyl methacrylate) used in dentistry with a reactive terpolymer containing maleic anhydride and their thermomechanical characterization

This study focuses on the preparation of compatible blends with the poly(methyl methacrylate) (PMMA) using a reactive terpolymer maleic anhydride–styrene–vinyl acetate (MA–St–VA). In the first series of experiments, binary blends of the PMMA and the MA–St–VA terpolymer have been prepared in tetrahydrofurane. The PMMA and the MA–St–VA terpolymer formed the compatible blends. The effects on thermomechanical properties of MA–St–VA terpolymer ratio in the blends were studied. The glass transition temperatures (T_g), thermal expansion coefficient (α), and other thermomechanical parameters for the blends have been established by TMA method and the compatibility of two polymers has been evaluated by these TMA parameters. The addition of MA–St–VA terpolymer to PMMA made a plasticizing effect on PMMA. This effect regularly changed with the increasing of the terpolymer in the blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 363–367, 2006     

Accelerated transformation of brushite to octacalcium phosphate in new biomineralization media between 36.5 °C and 80 °C

This study investigated the hydrothermal transformation of brushite (dicalcium phosphate dihydrate, DCPD, CaHPO₄·2H₂O) into octacalcium phosphate (OCP, Ca₈(HPO₄)₂(PO₄)₄·5H₂O) in seven different newly developed biomineralization media, all inspired from the commercial DMEM solutions, over the temperature range of 36.5 °C to 90 °C with aging times varying between 1 h and 6 days. DCPD powders used in this study were synthesized in our laboratory by using a wet-chemical technique. DCPD was found to transform into OCP in the Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^?, Cl^? and H₂PO₄^? containing aqueous biomineralization media in less than 72 h at 36.5 °C, without stirring. The same medium was able to convert DCPD into OCP in about 2 h at 75–80 °C, again without a need for stirring. Samples were characterized by using powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM).     

The evaluation of some flexural properties of a denture base resin reinforced with various aesthetic fibers

This study was performed to determine whether some flexural properties of a denture base resin material could be improved through reinforcement with five types of aesthetic fibers at 3% concentration by weight and in 2, 4, and 6 mm length. Five specimens of similar dimensions were prepared for each of the test groups; base resin and the same resin with glass, rayon, polyester, nylon 6 and nylon 6,6 fibers in three different lengths. Flexural properties were evaluated by using a 3-point bending test. A visual examination was also made to determine mode of fracture of the specimens. The incorporation of different fibers in varying lengths had no significant effect on flexural strength of the resin. The specimens reinforced with nylon 6,6 fibers of 6 mm length showed the highest flexural strength. Young’s modulus and maximum load suggests that such reinforcement makes resin resistant to fracture.     

Motor coactivation revealed by response force in divided and focused attention.

Four experiments examined effects of bimodal stimulation on response force (RF) in addition to reaction time (RT). In a divided-attention task (Exps 1–3), Ss were asked for a speeded response to either a visual or an auditory signal. In unimodal signal trials, either a visual or auditory signal was presented alone, and in redundant-signals trials, both signals were presented simultaneously. The same stimulus arrangement was used in a focused-attention task (Exp 4), but Ss had to withhold their response when an auditory signal was presented alone. In all experiments, the fastest RTs were attained in redundant-signals trials. In addition, RF was largest in redundant-signals trials, especially in the divided-attention task, suggesting a motor coactivation hypothesis. The results indicate that the type of stimulation influences not only when a response is initiated but also how the response is executed. This finding challenges the view, commonly held in mental chronometry, that late motoric processes remain untouched by experimental manipulations. A detailed analysis of the relationship between RT and RF revealed that these variables are not inherently redundant measures, and therefore, RF recording may supplement the traditional RT measurement in mental chronometry. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On evaluating Weibull fits to mechanical testing data

The use of coefficient of determination, R², and the Anderson–Darling (A²) hypothesis test to evaluate the goodness-of-fit to the two-parameter Weibull distribution was investigated. Results of Monte Carlo simulations for sample sizes between 5 and 100 indicated that guidelines provided previously in the literature are too conservative for sample sizes up to 80. New guidelines for the use of R² and A² for sample sizes between 5 and 100 have been developed. The two measures of goodness-of-fit were found to agree more than 95% of the time, regardless of sample size. The use of the new guidelines has been demonstrated on two datasets from the casting literature.