Microstructural and phase transformations during sintering of a phillipsite rich zeolitic tuff

Microstructural and phase transformations during sintering of a Phillipsite rich zeolitic tuff, from Tenerife, Canary Islands, was investigated in order to their utilization in ceramic manufacturing industries. Green samples were obtained from powders and pressed at 150 MPa and heat-treated for 1 hour in the temperature range between 900-1080 °C. The zeolitic tuffs show endothermic peaks at about 100 °C and 200 °C, corresponding to dehydration of zeolitic water observed in the thermo- gravimetric curves and at ∼700 °C a small endothermic peak was identified corresponding to the structural breakdown of Phillipsite. According to the dilatometric traces, at about 870 °C, sintering of solid particles starts and a linear shrinkage of about 6% is reached at about 1050 °C. The maximum absolute and apparent densities were obtained after sintering at 1040 °C (absolute density = 2.59 g/cm³; apparent density = 2.33 g/cm³). Over this temperature, the sample heat-treated at 1060 °C, density results show a decreasing trend. The chemical composition of studied zeolitic tuffs make possible the liquid phase formation during heat-treatment, through the supplement of alkaline oxides. SEM image of the sample obtained at 1040 °C shows a zone with micro-crystallinity around the boundary of Sanidine grain highlighting the beginning of the phase transition from Sanidine, to Microcline. Heat-treatment effect of zeolitic tuff leads to the decomposition of Phillipsite and Sanidine and the formation of a new crystal phase of Hematite.     

Characterization of Terebinth Fruit Oil and Optimization of Acidolysis Reaction with Caprylic and Stearic Acids

Characterization of the fatty acid and triacylglycerol composition of terebinth fruit oil and the synthesis of structured lipids (SL) were performed in this study. Interesterification reaction of terebinth fruits oil (Pistacia terebinthus L.) with caprylic acid (CA) and stearic acid (SA) to produce a SL was performed in n-hexane using immobilized sn-1,3 specific lipase from Mucor miehei. The effect of reaction conditions and relationship among them were analyzed by response surface methodology (RSM) with a four-factors five-level central composite rotatable experimental design. The four major factors chosen were enzyme load (10–30 wt% based on substrates), reaction time (7–18 h), reaction temperature (40–60 °C) and substrate mole ratio (terebinth oil:SA:CA 1:1:1–1:1:3). The best fitting quadratic model was determined by regression and backward elimination. Based on the fitted model, the optimal reaction conditions for the incorporation of CA and SA were found to be temperature 50 °C; time 18 h; enzyme load 30 wt%; substrate ratio 1:1:3. Under these optimum conditions, the incorporation of SA and CA could be obtained as 19 and 14%, respectively.     

Influence of fortification with sodium–calcium caseinate and whey protein concentrate on microbiological,textural and sensory properties of set‐type yoghurt

The effect of fortification of yoghurt with sodium–calcium caseinate (SCC) and whey protein concentrate (WPC) on some properties of set‐type yoghurt were investigated. The addition of WPC enhanced the viability of Lactobacillus delbrueckii subsp. bulgaricus more than SCC. The highest firmness values were obtained from SCC‐fortified yoghurts, whereas yoghurts fortified with WPC had the highest water‐holding capacity during storage. The yoghurts fortified with 4% w/w SCC or 4% w/w WPC had the highest viscosity. Yoghurts fortified with 2% w/w SMP, SCC or WPC showed similar taste and overall acceptability scores; however, samples containing 4% w/w SCC or 4% w/w WPC had the lowest scores.     

HPLC-DAD Analysis to Identify the Phenolic Profile of Rhododendron Honeys Collected from Different Regions in Turkey

In this study, phenolic compounds of Rhododendron honey (also known as mad honey) samples collected from the Black Sea Region were identified using high performance liquid chromatography-diode array detector system. The major phenolic substances in Rhododendron honeys were found to be chlorogenic and coumaric acids with the amounts of 0.11–191.54 mg/kg and 0–82.83 mg/kg, respectively. Gallic and ferulic acids were detected in the most honey samples. Additionally, significant correlations were determined between the phenolic substances. The present study showed that Rhododendron honeys contained higher quantities of phenolic acids than flavonoids. Chlorogenic and coumaric acids were the dominant phenolic substances detected in honey samples.     

Electrochemical impedance spectroscopy and morphological analyses of pyrrole, phenylpyrrole and methoxyphenylpyrrole on carbon fiber microelectrodes

In this study, N-pyrrole (Py), N-phenylpyrrole (PhPy), and 1[4-methoxyphenyl]-1H-pyrrole (MPhPy) homopolymers were synthesized electrochemically onto carbon fiber microelectrodes (CFMEs). The influences of the substituent effect on electrochemical impedance spectroscopy (EIS) were studied comparatively. All the monomers were electrodeposited in 0.05 M tetraethyl ammonium perchlorate (TEAP)/dichloromethane (CH₂Cl₂) solution and characterized by cyclic voltammetry (CV), Fourier transform infrared reflectance spectrophotometry (FTIR-ATR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The morphological study reveals that the polymers were deposited as a continuous and well adhered film to surface of the CFME. An equivalent electrical circuit for three different monomers on CFMEs was proposed and experimental data were simulated to obtain the numerical values of circuit components. All results support the high quality film deposition that resulted in desired electronic properties due to the electron donating behaviors of substituent group of phenyl and methoxy.     

Radon concentration in houses over a closed Hungarian uranium mine

High radon concentration (average 410 kBq m-3) has been measured in a tunnel of a uranium mine, located 15-55 m below the village of Kovágószolos, Hungary. The mine was closed in 1997; the artificial ventilation of the tunnel was then terminated and recultivation works begun. In this paper, a study has been made as to whether the tunnel has an influence on the radon concentration of surface dwellings over the mining tunnel. At different distances from the surface projection of the mining tunnel, radon concentration, the gamma dose, radon exhalation and radon concentration of soil gas were measured. The average radon concentration in the dwellings was 483 Bq m-3. Significantly higher radon concentrations (average 667 Bq m-3) were measured in houses within +/-150 m from the surface projection of the mining tunnel +50 m, compared with the houses further than the 300-m belt (average 291 Bq m-3). The average radon concentration of the soil gas was 88.8 kBq m-3, the average radon exhalation was 71.4 Bq m-2 s-1 and higher values were measured over the passage as well. Frequent fissures crossing the passage and running up to the surface and the high radon concentration generated in the passage (average 410 kBq m-3) may influence the radon concentration of the houses over the mining tunnel.     

Thermodynamic Models and Central Composite Design for Calcium Sulfate Dihydrate Solubility

The solubility of calcium sulfate dihydrate (gypsum) was measured in HCl solutions in the presence of Cr³⁺ and Fe³⁺ ions at various temperatures. The results indicate that the solubility of gypsum is fairly dependent on the concentrations of HCl and impurities, i.e., Cr³⁺ and Fe³⁺ ions. The experimental data were analyzed by applying the Buchowski-Kiazczak (λh) model and the modified Apelblat model. Some thermodynamic parameters, such as the standard molar dissolution enthalpy, the standard molar Gibbs energy, and the entropy of solutions, were calculated by Van't Hoff analysis and Gibbs equation. The influences of the concentrations of both HCl and impurities, i.e., Cr³⁺ and Fe³⁺ ions, and temperature on the gypsum solubility were examined by applying the central composite design.     

Design and realization of an ultra‐low power sensing RF energy harvesting module with its RF and DC sub‐components

Herein, design, development, and analysis of ultra‐low power sensing energy harvesting modules and their subcomponents for ISM band applications have been studied with a holistic approach in an effort to achieve a feasible and high efficient RF energy harvesting performance. The complete harvester system designed and developed here consists of a zero‐bias RF energy rectifying antenna (rectenna), DC boost converters and energy storage super‐capacitors. Compared with the counterpart energy sources, the surrounding or transmitted wireless energy has low intensity which requires designs with high efficiency. To achieve a successful harvester performance, rectifier circuits with high sensitivity Schottky diodes and proper impedance matching circuits are designed. Dedicated RF signals at various levels from nanowatts to miliwatts are applied at the input of the rectenna and the measured input power versus the scavenged DC output voltage are tabulated. Furthermore, by connecting the rectifier to a high gain antenna and using a RF signal transmitter, the wireless RF power harvesting performance at 2.4 GHz was tested up to 5 m. The performance of the rectenna is analyzed for both low‐power detection and efficiencies. Impedance matching network is implemented to reduce the reflected input RF power, DC to DC converters are evaluated for their compatibility to the rectifiers, and super‐capacitor behaviors are investigated for their charging and storage capabilities. The measured results indicate that a wide operating power range with an ultra‐low power sensing and conversion performance have been achieved by optimizing the efficiency of the Schottky rectifier as low as ?50 dBm. The system can be used for battery free applications or expanding battery life for ultra‐low power electronics, such as; RFID, LoRa, Bluetooth, ZigBee, and low power remote sensor systems.     

Removal of basic dyes from aqueous solutions using starch‐graft‐acrylic acid copolymers

Graft copolymerization of acrylic acid (AA) onto starch was carried out with ceric ammonium nitrate as initiator under nitrogen atmosphere. The grafting percentages (GP%) of starch‐graft‐AA (St‐gr‐AA) copolymers were determined. When the AA molar concentrations were 0.3 and 0.5 mol/L, GP% of St‐gr‐AA copolymers were 10.5% (St‐gr‐AA‐1) and 14% (St‐gr‐AA‐2), respectively. St‐gr‐AA copolymers have been used for the adsorption of basic dye (Safranine T) from aqueous solutions. Effects of various parameters such as treatment time, initial pH of the solution (pH = 2–6), initial dye concentration (50– 500 mg/L), and GP% of starch graft copolymers were investigated.Basic dye removal capacities of the copolymers increase along with the augment of initial concentration of the adsorbate, GP% of the copolymers, and pH. The adsorption capacities for St‐gr‐AA‐1 and St‐gr‐AA‐2 reach 116.5 and 204 mg/g, respectively. Equilibrium adsorption data were obtained and fitted very well to Freundlich model. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007