Natural vacuum distillation technique—Part II: Experimental investigation

This part of the study is concerned with the experimental investigation and uncertainty analysis of natural vacuum distillation process. Natural vacuum distillation (NVD) system is operated in the forms of free and forced mass convection. The experiments are conducted at temperatures of 20 and 40°C of network water as fluid in the system. During the experiments, total pressure losses are measured as 15.33kPa during free mass convection distillation while 14 kPa during forced mass convection distillation. Depending on time and temperature, the ratios of vapour/wastewater (v/ww)_free, distilled water/wastewater (dw/ww)_forced and total energy/distilled water (te/dw) are experimentally determined. Moreover, the ratios of mass and energy balances are experimentally obtained. Accordingly, it is found that the ratios of (dw)_forced/(dw)_free vary between 1.4 and 1.6 depending on the wastewater temperatures. In addition, 2.5 kWh kg^?1 distilled water is experimentally used in the NVD system with free mass convection while 2.6 kWh kg^?1 distilled water in the NVD system with forced mass convection. In case of reduction of heat and pressure losses in the systems, 0.7 kWh is needed for the former while 1.3 kWh of energy is required for the latter. Copyright © 2004 John Wiley & Sons, Ltd.     

Investigation of thermal performance of a ground coupled heat pump system with a cylindrical energy storage tank

An analytical and computational model for a solar assisted heat pump heating system with an underground seasonal cylindrical storage tank is developed. The heating system consists of flat plate solar collectors, an underground cylindrical storage tank, a heat pump and a house to be heated during winter season. Analytical solution of transient field problem outside the storage tank is obtained by the application of complex finite Fourier transform and finite integral transform techniques. Three expressions for the heat pump, space heat requirement during the winter season and available solar energy are coupled with the solution of the transient temperature field problem. The analytical solution presented can be utilized to determine the annual variation of water temperature in the cylindrical store, transient earth temperature field surrounding the store and annual periodic performance of the heating system. A computer simulation program is developed to evaluate the annual periodic water and earth temperatures and system performance parameters based on the analytical solution. Copyright © 2003 John Wiley & Sons, Ltd.     

The effect of drying method and storage on color characteristics of paprika

Discoloration and microbial proliferation are two major problems associated with production of paprika (Capsicum annuum L.) with traditional drying methods. In the present study, the Refractance Window™ drying (RWD) method was employed to dry paprika in comparison with freeze drying, hot-air oven drying, and natural convective drying methods. In order to evaluate the color quality of paprika, the reflected color parameters, extractable color, red/yellow pigment ratio, and browning index were measured immediately after drying and during three-month storage. The freeze-dried and RWD-dried paprika showed better reflected color characteristics. The highest extractable color and browning index values were recorded in naturally convective dried paprika. There was no significant difference in browning index between freeze-died and RWD-died samples. The reflected color degradation of the paprika was highly associated with brown reaction. A gradual discoloration was observed in all paprika samples during storage.     

The effect of altered selenium and vitamin E nutritional status on learning and memory of third-generation rats

It has been proposed that selenium (Se) and Vitamin E (Vit E) are involved synergistically in protection of cell membrane lipids from peroxidation. However, little is known about the effect of both deficiencies of Se and Vit E and toxic status of those antioxidants on the peroxidation potentiality of the brain. We aimed to study the effects of both Se and Vit E inadequate diet and Se rich diet on the learning and memory processes of third-generation young rats. Their ancestors were also fed by the same diets starting from their births. To test the learning and memory, the rats aged 60 days were trained by using automated two ways active avoidance shuttle box. The acquisition tests were terminated with training the rat from each group to be 25 trials per day during three days. Ten days after the last acquisition test, the retention test was performed and the acquisition of the conditioned avoidance responses (CAR) of the rats were evaluated. It is demonstrated that the CAR of all rats from three groups showed a significant increase in three consecutive days while the differences observed in CAR of same sessions was not significantly different among three groups. The memory process of these young rats also was not affected significantly by two types of diets. Under the light of our results one can suggest that, in the case of alterations in antioxidant defense status, the learning and the memory mechanisms seems to be not affected. Further researches are needed to be able to explain the possible role of oxidative stress on the mechanisms of learning and memory.     

Preparation and characterization of pH responsive poly(methacrylic acid‐acrylamide‐N‐hydroxyethyl acrylamide) hydrogels for drug delivery systems

In this study, pH responsive polymers composed of methacrylic acid, acrylamide, and N‐hydroxyethyl acrylamide were synthesized by free radical polymerization technique. The characterization was done with Fourier transform infrared spectroscopy and scanning electron microscopy. The swelling and drug release behavior of the hydrogels was determined as a function of time at 37°C in pH 2.1 and 7.4. The swelling and drug release studies showed that increased methacrylic acid amount caused a higher increase in swelling and drug release values at pH 7.4 than those at pH 2.1. In addition, the drug release data were applied to kinetic models such as zero order, first order, and Higuchi equations, and it fit well in the Higuchi model of the hydrogel. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43226.     

Synthesis and NMR studies of the polymer membranes based on poly(4-vinylbenzylboronic acid) and phosphoric acid

Proton conduction in novel anhydrous membranes based on host polymer, poly(4-vinylbenzylboronic acid), (P4VBBA) and phosphoric acid, (H₃PO₄) as proton solvent was studied. The materials were prepared by the insertion of the proton solvent into P4VBBA at different stoichiometric ratios to get P4VBBA·xH₃PO₄ composite electrolytes. Homopolymer and the composite materials were characterized by FT-IR, ¹¹B MAS NMR and ³¹P MAS NMR. ¹¹B MAS NMR results suggested that acid doping favors or leads to a four-coordinated boron arrangement. ³¹P MAS NMR results illustrated the immobilization of phosphoric acid to the polymer through condensation with boron functional groups (B-O-P and/or B-O-P-O-B). Thermogravimetric analysis (TGA) showed that the condensation of composite materials starts approximately at 140 °C. An exponential weight loss above this temperature was attributed to intermolecular condensation of acidic units forming cross-linked polymer. The insertion of phosphoric acid into the matrix softened the materials shifting T_g to lower temperatures. The temperature dependence of the proton conductivity was modeled with Arrhenius relation. P4VBBA·2H₃PO₄ has a maximum proton conductivity of 0.0013 S/cm at RT and 0.005 S/cm at 80 °C.     

A lumped-circuit model for the radiation impedance of a circular piston in a rigid baffle

The radiation impedance of a piston transducer mounted in a rigid baffle has been widely addressed in the literature. The real and imaginary parts of the impedance are described by the first order Bessel and Struve functions, respectively. Although there are power series expansions for both functions, the analytic formulation of a lumped circuit is not trivial. In this paper, we present an empirical approach to the derivation of a lumped-circuit model for the radiation impedance expression, based on observations on the near-field behavior of stored kinetic and elastic energy. The field analysis is carried out using a finite element method model of the piston and surrounding fluid medium. We show that fluctuations in the real and imaginary components of the impedance can be modeled by series and shunt tank circuits, each of which shape a certain section of the impedance curve. Because the model is composed of lumped-circuit elements, it can be used in circuit simulators. Consequently, the proposed model is useful for the analysis of transducer front-end circuits.     

The adherence of <Emphasis Type="Italic">Candida albicans</Emphasis> to acrylic resin reinforced with different fibers

One important aethiological factor in the pathogenesis of chronic atrophic candidosis is the presence of Candida albicans on the fitting surface of the dentures. Fibers may come into contact with oral mucosa during the finishing procedures of acrylic resins. The exposed fibers may provide mechanical retention for yeast cells at the interface of the components. The effect of two different glass fibers and two different environments were evaluated in respect of Candida albicans adhesion to the acrylic surface. Half of the acrylic samples reinforced with two different fibers (Sticknet and Eversticknet) were pretreated with phosphate-buffered saline (PBS) and the rest with unstimulated saliva. The test specimens were placed in yeast suspension. The adhered cells were examined with a scanning electron microscope. The amount of adhered cells in PBS was lower for Eversticknet but the difference was not significant (p > 0.05). The number of yeast cells decreased in saliva for both groups and the difference was statistically significant for the samples reinforced with Eversticknet (p < 0.01). The use of Sticknet or Eversticknet as reinforcing material for poly(methylmethacrylate) had no effect on surface topography due to the same adhesion state of Candida albicans. The presence of a salivary pellicle derived from unstimulated saliva reduced adhesion of Candida albicans.     

Synthesis of undecanoic acid phenylamides as corrosion inhibitors

Non‐substituted or mono‐substituted 11‐cyano or 11‐thiocyanato undecanoic acid phenylamide derivatives were synthesized and characterized with their FT‐IR and ¹H‐NMR spectra. Thereafter, their corrosion prevention efficiencies were investigated. All compounds were tested with steel coupons in acidic medium by a gravimetric method. Acidic tests were done with a medium concentration of 2 M HCl for 5 h at variable temperatures and inhibitor concentrations. The corrosion prevention efficiencies of the inhibitors were compared according to their chemical structures and the corrosion inhibition mechanism was also discussed. The synthesized compounds showed promising corrosion inhibition efficiencies under the outlined test conditions. Best inhibitions were obtained at 27°C and 100 ppm concentration of corrosion inhibitors.     

GA-TVRC-Het: genetic algorithm enhanced time varying relational classifier for evolving heterogeneous networks

Evolving heterogeneous networks, which contain different types of nodes and links that change over time, appear in many domains including protein–protein interactions, scientific collaborations, telecommunications. In this paper, we aim to discover temporal information from a heterogenous evolving network in order to improve node classification. We propose a framework, Genetic Algorithm enhanced Time Varying Relational Classifier for evolving Heterogeneous Networks (GA-TVRC-Het), to extract the effects of different relationship types in different time periods in the past. These effects are discovered adaptively by utilizing genetic algorithms. A relational classifier is extended as the classification method in order to be able to work with different types of nodes. The proposed framework is tested on two real world data sets. It is shown that using the optimal time effect improves the classification performance to a large extent. It is observed that the optimal time effect does not necessarily follow a certain functional trend, for example linear or exponential decay in time. Another observation is that the optimal time effect may be different for each type of interaction. Both observations reveal the reason why GA-TVRC-Het outperforms methods that rely on a predefined form of time effect or the same time effect for each link type.