Determination of optimum Pd:Ni ratio for PdxNi100‐x/CNTs formic acid electrooxidation catalysts synthesized via sodium borohydride reduction method

The main purpose of this study is to investigate the optimum Pd:Ni molar ratio for carbon nanotube–supported PdNi (Pd_xNi_100‐x/CNT) alloy catalysts toward formic acid electrooxidation (FAE). NaBH₄ reduction method was employed for the synthesis of Pd₉₀Ni₁₀/CNT, Pd₇₀Ni₃₀/CNT, Pd₅₀Ni₅₀/CNT, and Pd₄₀Ni₆₀/CNT. Synthesized catalysts were characterized by employing advanced surface analytical techniques, namely, X‐ray diffraction (XRD), transmission electron microscopy (TEM), N₂ adsorption‐desorption, and inductively coupled plasma–mass spectrometry (ICP‐MS). The characterization results showed that all catalysts were successfully synthesized at desired molar composition. Pd₉₀Ni₁₀/CNT displayed the highest specific and mass activities with 2.32 mA/cm² and 613.9 mA/mg Pd, respectively. Specific activity of the Pd₉₀Ni₁₀/CNT was found approximately 3.6, 2.3, 11.1, and 3.4 times higher than those of Pd₇₀Ni₃₀/CNT, Pd₅₀Ni₅₀/CNT, Pd₄₀Ni₆₀/CNT, and Pd/CNT, respectively. The synergistic effect between Pd and Ni at optimized metal ratio was utilized to obtain an improvement in specific activity. Furthermore, Pd₉₀Ni₁₀/CNT showed the lowest charge transfer resistance (R_ct) and a long‐term stability. To our knowledge, this is the first study reporting the optimization of atomic molar composition for Pd_xNi_100‐x/CNT catalysts toward FAE.     

Caffeic Acid Detection Using an Inhibition-Based Lipoxygenase Sensor

An inhibition based biosensing system was developed for the caffeic acid as lipoxygenase (LOX) inhibitor. LOX was immobilized in carbon paste electrode and the amperometric detection of hydroperoxy linoleic acid due to the enzymatic reaction using linoleic acid as a substrate was monitored at +0.9 V versus Ag/AgCl. The decrease in biosensor response in the presence of caffeic acid was found to be correlated with the inhibitor concentration. Diode array detector and LOX biosensor was used as an electrochemical detector for the analysis of this compound. All data were given as a comparison of two systems.     

Investigations into the mechanisms controlling parturition in cattle

A pronounced increase in fetal cortisol concentrations stimulating an increase in estrogen production at the expense of progesterone precursors in the placenta, luteolysis, and progesterone withdrawal is considered as a key event during the complex signal cascade leading to the initiation of parturition in cattle. However, there are many questions concerning the exact functional and/or temporal relationships between these individual processes which finally result in the expulsion of the calf and the timely release of the placenta. Thus, parturition was induced in 270-day pregnant cows using the progesterone receptor blocker aglepristone (group AG, n=3), the prostaglandin F(2α) analog cloprostenol (group PG, n=4), and the glucocorticoid dexamethasone (group GC, n=4) to characterize the effect on maternal steroid and prostaglandin levels and to identify immediate subsequent changes in placental morphology and gene expression as compared with untreated controls sampled on day 272 (group D272, n=3) and cows during normal parturition (group NT, n=4). All calves of the treatment groups were born on days 271-272, whereas gestational length in NT cows was 280.5±1.3 days. However, none of the treatments significantly induced the prepartal remodeling of placentomes characterized by a decline in trophoblast giant cells and reduction of the caruncular epithelium. Data on placental CYP17 and COX2 expression confirm that these key enzymes are upregulated by GC, whereas placental aromatase expression was not affected by any treatment. Maternal progesterone and prostaglandin profiles suggest differential effects of the treatments on luteal function and placental or uterine prostaglandin production. The results provide new information on the initiation of parturition in cattle but raise many new questions.     

Synthesis of in situ N‐, S‐, and B‐doped few‐layer graphene by chemical vapor deposition technique and their superior glucose electrooxidation activity

At present, N‐, S‐, and B‐doped grapheme‐modified indium tin oxide (ITO) electrodes are produced and doping method effect on the glucose electrooxidation is investigated. Firstly, few‐layer graphene is produced by chemical vapor deposition (CVD) method. Then, N, S, and B doping is carried out after graphene produced by CVD to prepare N‐doped, B‐doped, and S‐doped few‐layer graphene. N, S, and B doping is carried out by two different ways as (a) doping after synthesis of few‐layer graphene and (b) in situ doping during few‐layer graphene production. These materials are characterized by X‐ray diffraction, scanning electron microscopy‐energy (SEM), Raman spectroscopy, and X‐ray photoelectron spectroscopy (XPS). One could note that graphene and nitrogen networks are clearly visible from SEM images. Raman spectra show that B, N, and S are doped on few‐layer graphene/ITO successfully. XPS results of graphene, N‐doped graphene, and in situ N‐doped graphene reveal that graphene and nitrogen atoms used in the preparation of the electrodes obtain mainly in their elemental state. Then, these N‐, S‐, B‐doped and in situ N‐, S‐, B‐doped few‐layer graphene materials are coated onto indium tin oxide (ITO) to obtain N‐, S‐, B‐doped and in situ N‐, S‐, B‐doped ITO electrodes for glucose (C₆H₁₂O₆) electrooxidation. C₆H₁₂O₆ electrooxidation measurements are investigated with cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy measurements. As a result, in situ N‐doped few‐layer graphene/ITO electrode displays the best C₆H₁₂O₆ electrooxidation activity with 9.12 mA.cm^?2 current density compared with other N‐, S‐, B‐doped graphene and in situ doped S and B grapheme‐modified ITO electrodes. Furthermore, this current density value for in situ N‐doped few‐layer graphene/ITO is highly above the values reported in the literature. In situ N‐doped few‐layer graphene/ITO electrode is a promising electrode for C₆H₁₂O₆ electrooxidation because it exhibits the best electrocatalytic activity, stability, and resistance compared with other electrodes.     

Electrochemical glucose biosensing by pyranose oxidase immobilized in gold nanoparticle-polyaniline/AgCl/gelatin nanocomposite matrix

A novel pyranose oxidase (PyOx) biosensor based on gold nanoparticles (AuNPs)–polyaniline(PANI)/AgCl/gelatin nanocomposite has been developed for the glucose detection. PyOx was immobilized on the surface of glassy carbon electrode (GCE) via the nanocomposite matrix. The electrode surface was imaged by scanning electron microscopy (SEM). Amperometric detection of the consumed oxygen during the enzymatic reaction was monitored at −0.7 V. After optimization studies, analytical characterization of the biosensor was carried out. The linear response of the AuNPs–AgCl/PANI/gelatin modified PyOx biosensor is found to be from 0.05 to 0.75 mM glucose with the equation of y = 2.043x + 0.253; R² = 0.993. Finally, proposed biosensor was used to analyze glucose content in real samples. Obtained data from the biosensing system was compared with a commercial enzyme assay kit based on spectrophotometric Trinder reaction as a reference method.     

Transmission losses based MW contingency ranking

Contingency ranking and selection is an indispensable tool for static security analysis. Several performance indices suffer either from misranking or computational inefficiencies. This paper presents a new performance index for MW line flow contingency selection and ranking. The proposed index is derived from real power transmission losses. It is a quadratic function of bus voltage angles and can easily be calculated from real power flows or DC load flow. It improves both the selectivity and the ranking of second order performance index without excessive computational effort. The proposed method is tested on IEEE 24-bus reliability test system and IEEE 30-bus test system. The results are compared with those of the conventional second order performance index and of the tenth order reference performance index from the point of ranking and selectivity.     

Profile of (n‐9) and (n‐7) Isomers of Monounsaturated Fatty Acids of Radish (Raphanus sativus L.) seeds

The present study was undertaken to determine the profile of the (n‐9) and (n‐7) isomers for C18:1, C20:1 and C22:1 fatty acids in radish seeds as well as their isomers. Radish (Raphanus sativus L. cvs. ‘Antep, Beyaz, Cherry Belle and Iri K?rm?z?’) seeds were produced in 2003–2005 from different sowing dates (SD). The n‐7 isomers of C18:1, C20:1 and C22:1 ranged from 0.7 to 1.3, 0.1 to 0.3 and 0.4 to 1.1 %, respectively. The average values of C18:1(n‐7) was highest (1 %) amongst the three acids. The ratios of (n‐7)/(n‐9) ranged from 4.5 % (‘Cherry Belle’, SD‐I) to 8.3 % (‘Antep’, SD‐III), 0.8 % (‘Iri K?rm?z?’, SD‐II) to 3 % (‘Iri K?rm?z?’, SD‐I) and 1.6 % (‘Cherry Belle’, SD‐I) to 3.7 % (‘Iri K?rm?z?’, SD‐I) for C18:1, C20:1 and C22:1. Erucic acid was the principal fatty acid with concentrations of nearly 34–39 % in ‘Antep’, 32–34 % in ‘Cherry Belle’, 30–33 % in ‘Beyaz’ and 21–22 % in ‘Ir? K?rm?z?’. The oleic acid content was higher in SD‐I and SD‐II than SD‐III in all cultivars. Correlation studies revealed that palmitoleic acid (C16:1) had a significant relationship between most of the fatty acids of the (n‐7)/(n‐9) family. The results indicated that palmitoleic acid is important in the synthesis of long‐chain fatty acids and that the data for the (n‐7)/(n‐9) ratios for C22:1 could be used as biochemical markers to determine the similarities or differences between radish cultivars.     

Surface properties of tannin-impregnated and varnished beech wood after exposure to accelerated weathering

The aim of this study was to determine selected surface properties of varnished beech wood impregnated with natural extracts after exposure to accelerated weathering. Beech wood samples were impregnated with aqueous solutions of 5 and 10% mimosa (Acacia mollissima) and quebracho (Shinopsis lorentzii) tannins. After weathering, colour changes (ΔL*, Δa*, Δb*, and ΔE*) in addition to scratch resistance and surface hardness values were calculated and evaluated. As a result of the weathering process, greater colour changes (ΔE*) were detected in the beech wood samples impregnated with tannins compared with the unimpregnated control samples. The least colour change occurred in the Tanalith-E-impregnated samples. Total colour change was adversely affected with tannin impregnation after the weathering processes. In terms of surface hardness and scratch resistance, the highest values were observed in the mimosa-solution-impregnated and control samples. Furthermore, it was found that scratch resistance and hardness values tended to increase during the first period of weathering and decreased thereafter. Regarding surface properties, the best results were obtained when polyurethane varnish was employed compared with the other varnish types.     

The Use of Digital Image Processing Method to Estimate the Foam Characteristics of Polyurethane

Four air-bubbled polyurethane (PU) foams with different polyol:PMDI wt.% are produced, respectively. The chemical reaction mechanisms of polyurethane and bubble formation are proposed by performing standard Gibbs free energy calculations using the DFT M06-2X/6-31+G(d,p) method. The local minima, transition states, and intermediates in reaction mechanisms are detected. It is concluded that both reactions are exothermic. Then, raw images of the produced PU foams are taken with a 13 MP mobile phone camera, which can be considered inexpensive, and the mean radii of the pores are calculated by an image processing based method (IPBM) on a standard desktop computer with an i5 processor. It is determined that there is a close relationship between the calculated mean radius and instrumentally measured thermal conductivity coefficient of the foams. However, the thermal conductivity coefficients are independent of the calculated number and percentage of the pores. The mean radii of the samples calculated by the proposed IPBM are close to that of the SEM, with acceptable relative errors of less than 10%. Finally, it is concluded that IPBM, which is a more cost-effective, cleaner, and faster method than SEM, might replace SEM in the air bubble analysis of PU foams.