Effect of thermal cycling on micro-tensile bond strength of composite restorations bonded with multimode adhesive

Objective: The purpose of this in vitro study was to evaluate the effect of thermal cycling on the micro-tensile bond strength (Mtbs) of multimode adhesive agents. Materials and methods: Eight freshly extracted caries-free human third molars were used. The flat dentin surfaces were prepared and polished with 600-grit SiC abrasive paper for standard smear layer formation. The teeth were restored using Single Bond Universal Adhesive [(total etch (G1, G2)/self etch (G3, G4)]?+?Filtek Z550 and All-Bond Universal Adhesive [(total etch (G5, G6)/self etch (G7, G8)]?+?Aelite all-purpose. The specimens in groups G1, G3, G5, and G7 were subjected to thermal cycling (1000 cycles at 5–55 °C, for a 30?s dwell time), while the specimens in other groups were not exposed to an aging procedure. The Mtbs test was determined in all procedures. Data were submitted to three-way ANOVA and post hoc tests. The significance level was set at?=?0.05. Results: Group five was highly affected by the thermal cycling following the total etch procedure, while group one was not significantly affected. Group seven was highly affected by thermal cycling, while group three was not significantly affected after the self etch procedure. Group eight exhibited a higher mean Mtbs value after the thermal cycling procedure. Conclusion: The bond strength of multimode (universal) adhesives was found to be material dependent. The total etch procedure showed a higher Mtbs value than the self etch procedure.     

Combination of Ozonation and Hydrogen Peroxide Bleaching for Linen Fabrics: Optimization of the Process Using Experimental Design Technique

It is well known that ozone can be used as a bleaching agent for cellulosic textile materials. In the context of this study, investigations were undertaken to optimize bleaching of linen fabrics using Box-Behnken Experimental Design. The bleaching process involved two distinct steps where linen fabrics were ozonated under different treatment times then the latter in a subsequent step were subjected to hydrogen peroxide bleaching under a variety of conditions. As a result of study, three optimum recipes were achieved and pretreatment with ozone for 15 min before peroxide bleaching supplies time and chemical savings.     

In situ modification of cyclohexanone formaldehyde resin with boric acid for high‐performance applications

A boron‐containing cyclohexanone formaldehyde resin (BCFR) was synthesized from cyclohexanone, formaldehyde, and boric acid. The effects of the boric acid concentration, solubility, molecular weight, and thermal properties on the product were investigated. Characterization of the BCFRs was done by NMR spectroscopy, gel permeation chromatography, and Fourier transform infrared–attenuated total reflectance spectroscopy. The thermal properties of the samples were determined with differential scanning calorimetry and thermogravimetric analysis. The study results demonstrate that the resin had higher heat‐resistance properties than the commonly modified cyclohexanone formaldehyde resin. The obtained samples were also characterized morphologically by scanning electron microscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

PHOTOINDUCED WETTABILITY OF TITANIUM OXIDE THIN FILMS

We present here the results of a systematic investigation of the influence of the main deposition parameters (substrate temperature, deposition time, reactive gas composition, etc.) on the hydrophilic properties of DC sputtered titania films, grown on heated glass substrates (463?573 K), using water vapors as the reactive gas. Reference samples prepared in standard oxygen-based deposition conditions were used to compare the results. All the investigated samples were polycrystalline, with either pure anatase or mixed anatase-rutile nano-phase mixtures, depending on substrate temperature and film thickness. The surface wettability, evaluated from contact angle data during UV irradiation and in the back-reaction conditions, is discussed in terms of the synergic effects of materials structure, surface morphology, elemental composition, and electronic properties.     

Combining protein micro-phase separation and protein–polysaccharide segregative phase separation to produce gel structures

The ability of protein micro-phase separation and protein–polysaccharide segregative phase separation to generate a range of gel structures and textures was evaluated. Whey protein isolate/κ-carrageenan mixed gels were prepared with 13% (w/v) whey protein isolate, 0–0.6% (w/w) κ-carrageenan and 50, 100 or 250 mM NaCl. The microstructure of gels, determined by confocal laser scanning microscopy, varied from homogenous to protein continuous, bicontinuous, coarse stranded or κ-carrageenan continuous, depending on the κ-carrageenan concentration. Microstructure also varied from stranded to particulate (micro-phase separated) depending on the salt concentration. The rheological behavior of mixed gels corresponded to the shift in the continuous phase from protein to κ-carrageenan. At small concentrations of κ-carrageenan, where carrageenan-rich droplets were dispersed in a continuous protein-rich matrix, gel strength (fracture stress) and firmness (G′) increased due to increased local concentration of proteins caused by phase separation. At higher κ-carrageenan concentrations, gels were substantially less firm, weaker and less deformable (fracture strain). The change in the continuous phase from protein continuous to carrageenan continuous explained the major change in mechanical properties and water-holding properties. The shift in microstructure occurred at lower concentrations of κ-carrageenan when whey proteins were under micro-phase separation conditions. The results demonstrated how the combined mechanisms of ion-induced micro-phase separation of proteins and protein–polysaccharide phase separation and inversion can be used to alter gel structure and texture.     

Speciation of selenium in vitamin tablets using spectrofluorometry following cloud point extraction

Selenium is one of the trace and essential elements for good health but required only in a very narrow range. Hence, determination of selenium in trace level is important. In this work, cloud point extraction (CPE) with non-ionic surfactant Triton X-114 and the fluorometric ligand, 2,3-diaminonaphtalene (DAN) were used for extraction of trace amounts of organic and inorganic selenium species prior to their determination by spectrofluorometry. CPE parameters affecting complexation and phase separation were optimised. The limit of detection calculated by using nine replicate measurements of 0.020 mg/L Se solution after complexing with DAN and 10-fold CPE preconcentration was 2.1 μg/L. Accuracy of the method was checked using EnviroMat Waste Water, EU-L-2 as CRM and result was found to be in good agreement with the certified value. The suggested method can be used for selenium species of selenite, selenate, and total organic selenium at μg/L level.     

Determination of HMF in roasted flour/oil mixtures and effect of solvent used in the extraction procedure

Roasting of flour in oil or fat to form a roux is a common application in the preparation of many foods. In this study the development of 5-(hydroxymethyl)furfural (5-HMF) during roasting of white flour and oil mixtures prepared at 1:1, 1:2 and 1:3 ratios at 120, 160 and 200 °C was investigated. Extraction of 5-HMF from the solids phase, liquid (oil) phase and mixed phase of the samples was performed using three different solvents (water, ether and CCl₄) to evaluate the suitability of these solvents for improvement of the extraction procedure employed in the analysis method. The 5-HMF concentration was determined by using a reversed-phase HPLC system with a C₁₈ column and a photodiode array detector.     

Classification of three Turkish olive cultivars from Aegean region based on their fatty acid composition

In this study, fatty acid compositions of three olive cultivars oils (Ayvalik, Memecik, and Erkence) grown in Aegean region, the major olive production zone of Turkey, were classified by chemometric methods: principal component analysis and discriminant analysis (DA). A total of 187 oil samples were examined over the course of two harvest years (2001–2002 and 2002–2003). The samples were divided into three subgroups according to olive-growing zones: North Aegean (Ayvalik cultivar), South Aegean (Memecik), and İzmir Peninsula (Erkence cultivar). Consistent with discriminant analysis, the predicted groupings in terms of the two harvest years were correctly separated as 98.50 and 96.60%, respectively. In addition to oleic, linoleic, linolenic, margoleic, palmitic/linoleic and linoleic/linolenic were determined to be the best describing components for the oil samples.     

The effects of surface states and series resistance on the performance of Au/SnO2/n-Si and Al/SnO2/p-Si (MIS) Schottky barrier diodes

We have fabricated two types of Schottky barrier(SBDs),Au/SnO₂/n-Si (MIS1) and Al/SnO₂/p-Si (MIS2), to investigate the surface (N_ss) and series resistance (R_s) effect on main electrical parameters such as zero-bias barrier height (Φ_Bo) and ideality factor (n) for these SBDs. The forward and reverse bias current–voltage (I–V) characteristics of them were measured at 200 and 295 K, and experimental results were compared with each other. At temperatures of 200 and 295 K, Φ_Bo, n, N_ss and R_s for MIS1 Schottky diodes (SDs) ranged from 0.393 to 0.585 eV, 5.70 to 4.75, 5.42×10¹³ to 4.27×10¹³ eV^?1 cm^?2 and 514 to 388 Ω, respectively, whereas for MIS2 they ranged from 0.377 to 0.556 eV, 3.58 to 2.1, 1.25×10¹⁴ to 3.30×10¹⁴ eV^?1 cm^?2 and 312 to 290 Ω, respectively. The values of n for two types of SBDs are rather than unity and this behavior has been attributed to the particular distribution of N_ss and interfacial insulator layer at the metal/semiconductor interface. In addition, the temperature dependence energy density distribution profiles of N_ss for both MIS1 and MIS2 SBDs were obtained from the forward bias I–V characteristics by taking into account the bias dependence of effective barrier height (Φ_e) and R_s. Experimental results show that both N_ss and R_s values should be taken into account in the forward bias I–V characteristics. It has been concluded that the p-type SBD (MIS2) shows a lower barrier height (BH), lower R_s, n and N_ss compared to n-type SBD (MIS1), which results in higher current at both 200 and 295 K.     

Characterization of Turkish-Style Boiled Coffee Aroma by Gas Chromatography and Mass Spectrometry and Descriptive Analysis Techniques

The characteristic volatiles of light, medium, and dark roasted Turkish-style boiled coffee brews were studied by headspace solid-phase micro extraction/gas chromatography-mass spectrometry and sensory flavor profile analysis. Sixty-five volatile compounds, including furans, pyrazines, pyrroles, phenols, pyridines, ketones, oximes, alcohols, aldehydes, thiophenes, benzenes, and terpenes, were isolated from Turkish-style boiled coffee samples. The flavor profile analysis showed Turkish coffee brews as roasted/burnt, spicy, bitter, acidic, sweet, salty, astringent (dry), woody, fermented, earthy, and tobacco-like flavor characteristics. It was concluded that Turkish coffee was rich in furans, pyrazines, pyrroles, and phenols giving its roasted/burnt, spicy, woody, and fermented flavor characteristics.