Lowest ΔE Values Research Articles

Influence of Different Drinks on the Colour Stability of Dental Resin Composites

The objective of this study was to evaluate the discolouration effects of artificial saliva, granule lemon juice, coffee (without sugar), coca cola, sour cherry juice, fresh carrot juice and red wine on resin-based composite materials that are commonly used in restorative dentistry. Colour of four brands of resin composites (Filtek Z 250 (3M Espe), Filtek Supreme (3M Espe), Quadrant (Cavex), Charisma (Heraeus-Kulzer)) of A2 shade was measured after one day of immersion in eight different solutions. Colour measurements were obtained by using a XL-20 Trismus Colourimeter and colour differences (DeltaE) were estimated. For statistical evaluation, analysis of variance (ANOVA), Dunnett and Tukey tests were used at a significance level of 0.05. For the four restorative materials tested, the lowest DeltaE values were observed in the artificial saliva, while DeltaE values were the highest in red wine group. When comparing the four different restorative materials, Filtek Supreme exhibited the least colour changes whereas Filtek Z250 was the least colour-stable. Dental resin composites and drinking solutions were significant factors that may affect the colour stability. After immersion for one day, all materials showed visible colour changes. The red wine solution exhibited more staining than others in three groups. Filtek Supreme showed significantly the least colour change due to its nano particle sizes.

Soybean variety and storage effects on soymilk flavour and quality

SummarySoymilk prepared from five soybean cultivars, grown in Ontario, were analysed for protein, oil, mineral composition, viscosity, colour, lipoxygenase (LOX) activities and flavour profile. Among the five soybean cultivars, the Vinton 81 variety contained the highest protein and the lowest fat. The yield of soymilk from all five cultivars was similar. Major differences were observed in viscosity and in the composition of both the soymilk and the okara. Higher protein and fat extractability was found in soymilk made from S08‐80 and Vinton 81 varieties. Their okara protein contents were also among the highest. Minimum extractability was observed with S03W4 cultivar. Soymilk made from S 03W4 and Vinton 81 cultivars had the whitest colour (lowest ΔE values). Viscosity values were the highest for S08‐80, FG1 and S20‐20 varieties. Headspace solid‐phase microextraction gas chromatography was used to analyse volatile compounds in soymilk. A total of fourteen volatiles were identified, among which aldehydes and their corresponding alcohols were the major compounds. Similar volatile compounds were identified in all the samples analysed but at different concentrations. The highest LOX activity was observed in the Vinton 81 and S20‐20 soybean cultivars, which had the highest total volatile and hexanal contents. A positive correlation (correlation coefficient = 0.82) between enzymatic activity and the total volatiles was observed. Vinton 81 cultivar was subjected to storage (at 18 °C and 50% relative humidity) for a period of 10 months. Soymilk was prepared at different times during storage. The results showed that the soymilk colour, LOX and total volatiles were significantly (P < 0.05) affected by the storage of the soybeans over time.

The effect of polishing techniques on the surface roughness and color change of composite resins

Surface characteristics may affect the color change and surface roughness of composite resins. This study evaluated the surface roughness and color change of a hybrid, a microhybrid, and a nanohybrid composite resin polished with the use of polishing discs, wheels, and a glaze material. Fifty discs (10 x 2 mm) were fabricated for each composite resin (nanohybrid, Grandio; microhybrid, Filtek Z250; hybrid, Quadrant Universal LC) for a total of 150 discs, prepared using polyester strips and divided into 5 groups of 10. One of the groups served as control (C) and had no surface treatment (n=10). The specimens of the experimental groups were ground with 1000-grit silicon carbide paper. In 4 experimental groups (n=10), specimen surfaces were polished with polishing discs (D) (Sof-Lex), with polishing wheels (W) (Astropol), with polishing discs preceding the glaze application (DG) (Biscover), or with polishing wheels preceding the glaze application (WG), respectively. Color was assessed using a small area colorimeter. The color differences (DeltaE) values between the specimens of Group C and the experimental groups were calculated, and the data were compared using 2-way analysis of variance (ANOVA) (alpha=.05). Subsequently, the surface roughness (Ra) of the specimens was evaluated using a profilometer, and the data were analyzed by 2-way ANOVA followed by a Tukey multiple comparisons test (alpha=.05). The polishing technique and type of composite resin significantly affected the Ra and DeltaE values of the composite resins (P<.001). While the use of polishing wheels produced the highest Ra values when compared to the other polishing techniques (P<.001), the nanohybrid composite resin showed the lowest Ra values compared to the other composite resins in the control groups (P<.001). All of the nanohybrid and microhybrid composite resin groups were found to be significantly different from each other in terms of color difference (P<.001). The highest Ra values were obtained with hybrid composite resins due to the size of the filler particles that were exposed after polishing. Although the smoothest surfaces were obtained with polyester strips, the use of glaze material after polishing discs or polishing wheels resulted in significantly lower Ra and DeltaE values than the use of the latter alone. The glaze appears to fill the structural microdefects and provide a more uniform, regular surface.

抗菌成分としての銀錯体Ｒｐ［Ａｇｑ（Ｓ２Ｏ３）ｒ］（Ｒ＝Ｎａ，Ｋ）の熱安定性

Anti-microbial materials were synthesized with silver thiosulf ato complex Rp[Agq(S2O3)r](R=Na, K) on silica gel. Thermal stability of the materials was better with a potassium salt than a sodium salt. It was suggested that the change of cation “R” of the complexes from Sodium to Potassium resulted in thermal stability against oxidation after decomposition of the complexes. Among several cations for the complex, potassium was the most suitable. Potassium salts of the complex Kp[Agq(S2O3)r] were synthesized with various ratios of r/q from 1 to 8. With various ratios of r/q, each sodium or potassium salt of the complex was kneaded with resin, and the color difference value ΔE of the surface against natural resin was measured. TG-DTA measurements showed minimum thermal stability at r/q=4 and maximum at 6. Color measurements showed lower ΔE values with K salts than Na salts. The ΔE values of both salts showed peaked at r/q=4 and decreased at 6. Results of thermal stability TG-DTA measurements showed an agreement with the result of color measurements. It was thus suggested that the complex of potassium salt with an S2O3/Ag ratio of “6” had superior properties among the complexes for thermal stability against kneading treatment with resin. The chemical composition of the complex was K11[Ag(S2O3)6].

Thermal and temperature dependence of electrical conductivity studies on Zn, Cd and Hg hydrazone complexes

The complexes of Zn, Cd and Hg of isatin isonicotinoyl hydrazone were prepared at two differentpHs. Their thermal studies (TG, DTG and DTA) have been made and the DC electrical conductivity of compressed powder samples as a function of temperature was investigated. The activation energies (ΔE) were calculated for the ligand and the complexes which showed that the ligand has a lower value of ΔE than the complexes. The magnitude of ΔE was found to be affected by the nature of the metal and thepH of preparation.

Physical Properties of Novel Fluorinated Ethers and Ether Mixtures for Actively-Addressed, Twisted Nematic Liquid Crystal Displays

Abstract Several new classes of low polar, low viscous and optically weak anisotropic two- and three-ring fluorinated liquid crystals (LCs) with ether terminal groups are presented. Their material properties are investigated and compared with those of fluorinated LCs with alkenyl terminal groups. The 4-fluoro-phenylbicyclohexane ethers were found to exhibit dielectric anisotropies Δewhich are similar to those of the corresponding alkenyls with 1-propenyl and 3-pentenyl group, whereas the alkenyls with 4-pentenyl group exhibit considerably lower Δe-values. The optical and dielectric anisotropies of difluoro-ethers with odd numbers n of the methylene groups separating the ether oxygen from the rigid cores of the molecules are comparable, whereas compounds with odd n′s were found to exhibit lower vis-coelastic ratios γ/K and therefore shorter response times in twisted nematic liquid crystal displays (TN-LCDs) than their even counterparts. In mixtures designed for thin film transistor (TFT)-addressed TN-LCDs ...

Mössbauer study of iron vandium oxide bronze [formula omitted

The 57Fe Mössbauer spectra of the vanadium oxide bronze θ-Fe 0.35V 2O 5 recorded between 4 and 524 K reveal below 17 K the ordered magnetic phase of the spin-glass type and the paramagnetic one at higher temperatures. The two observed quadrupole doublets with nearly the same isomer shift but different ΔE Q values are due to the Fe 3+ ions occuring in two inequivalent surroundings. Calculations of the electric field gradient (EFG) show that the lower value of ΔE Q may be ascribed to the distorted octahedral coordination of the Fe atom whereas the higher value of ΔE Q is due to the Fe atom in the adjacent site which may be randomly occupied.

The Electronic Structures of Bis(cis-1,2-dicyano-1,2-ethenedithiolato)nickel Complexes

Abstract The core binding energies of N1s and S2s in cis-1,2-dicyano-1,2-ethanedithiolate (maleonitriledithiolate, mnt) complexes were measured by means of X-ray photoelectron spectroscopy (XPS), and the energy differences between N1s and S2s, ΔE, were found to be 171.7–172.6 eV throughout the complexes studied. The lowest ΔE value, 171.7 eV, was shown by [Ni(mnt)2]−. The electronic structures of [Ni(mnt)2]− and [Ni(mnt)2]2− were calculated by the discrete variational Xα method. The XPS measurements and the molecular orbital (MO) calculations provide consistent results that the oxidation state of the nickel atom is +2 for both nickel mnt complexes and that the highest occupied MO is 5b3g, which is mainly localized on ligands and which holds an unpaired electron in [Ni(mnt)2]−.