Importance of biodiesel as transportation fuel

The scarcity of known petroleum reserves will make renewable energy resources more attractive. The most feasible way to meet this growing demand is by utilizing alternative fuels. Biodiesel is defined as the monoalkyl esters of vegetable oils or animal fats. Biodiesel is the best candidate for diesel fuels in diesel engines. The biggest advantage that biodiesel has over gasoline and petroleum diesel is its environmental friendliness. Biodiesel burns similar to petroleum diesel as it concerns regulated pollutants. On the other hand, biodiesel probably has better efficiency than gasoline. One such fuel for compression-ignition engines that exhibit great potential is biodiesel. Diesel fuel can also be replaced by biodiesel made from vegetable oils. Biodiesel is now mainly being produced from soybean, rapeseed and palm oils. The higher heating values (HHVs) of biodiesels are relatively high. The HHVs of biodiesels (39–41 MJ/kg) are slightly lower than that of gasoline (46 MJ/kg), petrodiesel (43 MJ/kg) or petroleum (42 MJ/kg), but higher than coal (32–37 MJ/kg). Biodiesel has over double the price of petrodiesel. The major economic factor to consider for input costs of biodiesel production is the feedstock, which is about 80% of the total operating cost. The high price of biodiesel is in large part due to the high price of the feedstock. Economic benefits of a biodiesel industry would include value added to the feedstock, an increased number of rural manufacturing jobs, an increased income taxes and investments in plant and equipment. The production and utilization of biodiesel is facilitated firstly through the agricultural policy of subsidizing the cultivation of non-food crops. Secondly, biodiesel is exempt from the oil tax. The European Union accounted for nearly 89% of all biodiesel production worldwide in 2005. By 2010, the United States is expected to become the world's largest single biodiesel market, accounting for roughly 18% of world biodiesel consumption, followed by Germany.     

Determination of Phthalate Residues in Different Types of Yogurt by Gas Chromatography-Mass Spectrometry and Estimation of Yogurt-Related Intake of Phthalates

Phthalates are potential endocrine-disrupting chemicals, found widely in the environment, and commonly used to make plastics softer and more flexible. Little information is available about the presence of phthalates in yogurt products sold on the world market. This study aimed to develop a sensitive GC-MS method for the determination of selected phthalates in yogurt and residue levels in fruit yogurts together with the packaging materials and to estimate a yogurt-related exposure to phthalates in the Turkish population. Acetonitrile extraction followed by cleanup procedures using different adsorbents yielded relatively clean extracts. The presence as the percent of selected phthalates tested—dibutyl phthalate (DBP), diethylhexyl phthalate (DEHP), dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-octyl phthalate (DNOP), and benzyl butyl phthalate (BBP)—were determined as 76, 70, 70, 54, 20, and 8% of the samples, respectively, for the phthalates, ranging from <LOQ to 1640 μg/kg. The highest concentrations were found in cherry yogurt among the fruit yogurts, while banana and pineapple yogurts contained the least. The results indicate that the estimated daily intakes for phthalates were below tolerable daily intakes.     

β-Glucan and mineral nutrient contents of cereals grown in Turkey

Mixed-linked (1 → 3), ( 1→  4)-β-D-glucan contents of 14 selected cereal grains grown in Turkey, such as barley (Hordeum vulgaria), beans, canary seed (Tropaeolum peregrinum), corn/maize (Zea mays), flax, lentil (Lens culinaris), millet (Panicum miliaceum), oat (Avena sativa), peas, rice, rye (Secale cereale), spelt (Triticum spelta), spring wheat and winter wheat, were determined quantitatively using enzymatic methods. By using pure β-D-glucanase and β-D-glucosidase in the experiments, (1 → 3), ( 1→  4)-glycosidic bonds of linear polysaccharides found in cell-wall endosperm of plant seeds were hydrolyzed and the resulting β-D-glucans were determined by using glucose oxidase/peroxidase solution and measuring the absorbances at 510 nm in a UV-spectrophotometer. The nutrient mineral contents of the 14 selected cereal grains were studied. Some macronutrients such as K, Ca, Mg, N, P and S, and some micronutrients, such as Zn, Cu, Fe, Mn, Mo, and B, were analyzed by using atomic absorption spectrometric (AAS) methods. A flame photometer was used for determination of potassium. After oven drying of the samples, P was determined by a colorimetric method.     

Regio‐Selective Chemical‐Enzymatic Synthesis of Pyrimidine Nucleotides Facilitates RNA Structure and Dynamics Studies

Isotope labeling has revolutionized NMR studies of small nucleic acids, but to extend this technology to larger RNAs, site‐specific labeling tools to expedite NMR structural and dynamics studies are required. Using enzymes from the pentose phosphate pathway, we coupled chemically synthesized uracil nucleobase with specifically ¹³C‐labeled ribose to synthesize both UTP and CTP in nearly quantitative yields. This chemoenzymatic method affords a cost‐effective preparation of labels that are unattainable by current methods. The methodology generates versatile ¹³C and ¹⁵N labeling patterns which, when employed with relaxation‐optimized NMR spectroscopy, effectively mitigate problems of rapid relaxation that result in low resolution and sensitivity. The methodology is demonstrated with RNAs of various sizes, complexity, and function: the exon splicing silencer 3 (27 nt), iron responsive element (29 nt), Pro‐tRNA (76 nt), and HIV‐1 core encapsidation signal (155 nt).     

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.     

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 new flavone from antioxidant extracts of Pistacia terebinthus

Acetone and methanol extracts of the fruits of Pistacia terebinthus L. subsp. terebinthus L. were studied for their antioxidant activity by investigating their total phenolic and flavonoid contents, β-carotene bleaching potential, DPPH radical scavenging effect, scavenging activity on superoxide anion radical, reducing power, and metal chelating effect on ferrous ion. Both extracts showed very similar chemical profile by checking on TLC plates, and exhibited high scavenging activity on superoxide anion radical and DPPH radical. Due to these similarities they were combined and fractionated on a silica gel column for their constituents, and the most active three fractions in DPPH assay were purified to afford a new flavone 6′-hydroxyhypolaetin 3′-methyl ether (1) besides a group of known flavonoids apigenin, luteolin, luteolin 7-O-glucoside, quercetin, quercetagetin 3-methyl ether 7-O-glucoside, isoscutellarein 8-O-glucoside. Their structures were established by UV, UV shift reagents, and ¹H NMR spectroscopic techniques. Antioxidant activity of the new flavone was investigated by β-carotene bleaching and DPPH radical scavenging activity methods, and it showed a high activity in the first system, but not so good in the latter.     

Equilibrium studies for trimethoprim adsorption on montmorillonite KSF

In this study, the adsorption of trimethoprim (TMP) on montmorillonite KSF was studied under different conditions (pH, ionic strength, temperature). The results indicate that a pH value of 5.04 is optimum value for the adsorption of TMP on KSF. The adsorption kinetics was interpreted using pseudo-first-order kinetic model, pseudo-second-order kinetic model and intraparticle diffusion model. The pseudo-second-order model provides the best correlation with the experimental data of KSF adsorption. The adsorption data could be fitted with Freundlich, Langmuir and Dubinin-Radushkevich equation to find the characteristic parameters of each model. It was found that linear form of Langmuir isotherm seems to produce a better model than linear form of Freundlich equation. From the Langmuir and Freundlich equation, the adsorption capacity values raised as the solution temperature decreased. From DR isotherm, it was also determined that the type of adsorption can be considered as ion-exchange mechanism. Determination of the thermodynamic parameters DeltaH(0), DeltaS(0) and DeltaG(0) showed that adsorption was spontaneous and exothermic in nature. It was also added that adsorption of TMP by KSF may involve physical adsorption.