Wake of a cylinder: a paradigm for energy harvesting with piezoelectric materials

Short-length piezoelectric beams were placed in the wake of a circular cylinder at high Reynolds numbers to evaluate their performance as energy generators. The coherent vortical structures present in this flow generate a periodic forcing on the beam which when tuned to its resonant frequency produces maximum output voltage. There are two mechanisms that contribute to the driving forcing of the beam. The first mechanism is the impingement of induced flow by the passing vortices on one side of the beam, and the second is the low pressure core region of the vortices which is present at the opposite side of the beam. The sequence of these two mechanisms combined with the resonating conditions of the beam generated maximum energy output which was also found to vary with the location in the wake. The maximum power output was measured when the tip of the beam is about two diameters downstream of the cylinder. This power drops off the center line of the wake and decays with downstream distance as (x/D)^−3/2.     

Impedimetric Aptasensor Based on Disposable Graphite Electrodes Developed for Thrombin Detection

The impedimetric aptasensor for Thrombin (THR) was developed for the first time herein by measuring changes at the charge‐transfer resistance, R_ct upon to protein? aptamer complex formation. After covalent activation of pencil graphite electrode (PGE) surface using covalent agents, amino linked aptamer (APT) was immobilized onto activated PGE surface. Then APT‐THR interaction was explored by electrochemical impedance spectroscopy (EIS). After the optimization of experimental conditions (e.g., APT and THR concentration, immobilization and interaction times), the selectivity of impedimetric aptasensor was tested in the presence of other biomolecules: factor Va and bovine serum albumine (BSA) both in buffer media, or in diluted fetal bovine serum (FBS).     

The application of tunable tridendate P‐based ligands for the Ru(II)‐catalysed transfer hydrogenation of various ketones

Two novel versatile tridendate aminophosphine–phosphinite and phosphinite ligands were prepared and their trinuclear neutral ruthenium(II) dichloro complexes were found to be effective catalysts for the transfer hydrogenation of various ketones in excellent conversions up to 99% in the presence of 2‐propanol/NaOH in 0.1 M isopropanol solution. Particularly, [Ru₃(PPh₂OC₂H₄)₂ N–PPh₂(η⁶‐p‐cymene)₃Cl₆] acts as an excellent catalyst giving the corresponding alcohols in excellent conversion up to 99% (turnover frequency ≤ 1176 h^?1). A comparison of the catalytic properties of the complexes is also discussed briefly. Furthermore, the structures of these ligands and their corresponding complexes have also been clarified using a combination of multinuclear NMR spectroscopy, infrared spectroscopy and elemental analysis. ¹H–¹³C HETCOR or ¹H–¹H COSY correlation experiments were used to confirm the spectral assignments. Copyright © 2014 John Wiley & Sons, Ltd.     

Two Dimensional Materials Beyond MoS2: Noble‐Transition‐Metal Dichalcogenides

The structure and electronic structure of layered noble‐transition‐metal dichalcogenides MX₂ (M=Pt and Pd, and chalcogenides X=S, Se, and Te) have been investigated by periodic density functional theory (DFT) calculations. The MS₂ monolayers are indirect band‐gap semiconductors whereas the MSe₂ and MTe₂ analogues show significantly smaller band gap and can even become semimetallic or metallic materials. Under mechanical strain these MX₂ materials become quasi‐direct band‐gap semiconductors. The mechanical‐deformation and electron‐transport properties of these materials indicate their potential application in flexible nanoelectronics.     

Fast determination of octinoxate and oxybenzone uv filters in swimming pool waters by gas chromatography/mass spectrometry after solid‐phase microextraction

A fast gas chromatography/mass spectrometry method was developed and validated for the analysis of the potential endocrine disrupters octinoxate and oxybenzone in swimming pool water samples based on the solvent‐free solid‐phase microextraction technique. The low‐pressure gas chromatography/mass spectrometry method used for the fast identification of UV filter substances was compared to a conventional method in terms of sensitivity and speed. The fast method proposed resulted in 2 min runs, leading to an eightfold decrease in the total analysis time and a sevenfold improvement in detection limits. The main parameters affecting the solid‐phase microextraction process were also studied in detail and the optimized conditions were as follows: fiber coating, polyacrylate; extraction mode, direct immersion; extraction temperature, 25°C; sample volume, 5 mL; extraction time 45 min; pH 6.5. Under the optimized conditions, a linear response was obtained in the concentration range of 0.5–25 μg/L with correlation coefficients in the range 0.990–0.999. The limits of detection were 0.17–0.29 μg/L, and the recoveries were 80–83%. Combined method uncertainty was assessed and found to be less than 7% for both analytes for concentrations equal to or higher than 5 μg/L. Pool water samples were analyzed to demonstrate the applicability of the proposed method. Neither octinoxate nor oxybenzone were detected in the swimming pool water samples at concentrations above the respective limits of detection.     

Development of a molecularly imprinted solid‐phase extraction sorbent for the selective extraction of telmisartan from human urine

A novel molecularly imprinted solid‐phase extraction with spectrofluorimetry method has been developed for the selective extraction of telmisartan from human urine. Molecularly imprinted polymers were prepared by a noncovalent imprinting approach through UV‐radical polymerization using telmisartan as a template molecule, 2‐dimethylamino ethyl methacrylate as a functional monomer, ethylene glycol dimethacrylate as a cross‐linker, N,N‐azobisisobutyronitrile as an initiator, chloroform as a porogen. Molecularly imprinted polymers and nonimprinted control polymer sorbents were dry‐packed into solid‐phase extraction cartridges, and eluates from cartridges were analyzed using a spectrofluorimeter. Limit of detection and limit of quantitation values were 11.0 and 36.0 ng/mL, respectively. A very high imprinting factor (16.1) was achieved and recovery values for the telmisartan spiked in human urine were in the range of 76.1–79.1%. In addition, relatively low within‐day (0.14–1.6%) and between‐day (0.11–1.31%) precision values were obtained. Valsartan was used to evaluate the selectivity of sorbent as well. As a result, a sensitive, selective, and simple molecularly imprinted solid‐phase extraction with spectrofluorimetry method has been developed and successfully applied to the direct determination telmisartan in human urine.     

Biodegradable and stimuli sensitive amphiphilic graft copolymers and their sol–gel phase transition behavior

pH and temperature‐sensitive biodegradable poly(β‐aminoester)‐graft‐poly(ε‐caprolactone)‐block‐methoxy poly(ethylene glycol) (PBAE‐g‐PCL‐b‐mPEG) amphiphilic graft copolymers with different molecular weights were synthesized. The structure of these copolymers was adjusted by varying the feed ratios of ε‐caprolactone to methoxy poly(ethylene glycol)s (mPEG), amine and diacrylate monomer amounts and the molecular weight of mPEG. Aqueous solutions of these copolymers formed micelles at lower concentrations; however, the concentrated solutions showed a reversible sol–gel transition property depending on both pH and temperature changes under representative physiological conditions (pH 7.4, 37°C). The effects of the molecular weight of pH‐sensitive poly(β‐aminoester) block and mPEG group, the hydrophobic to hydrophilic block ratio (PCL/mPEG) and the concentration of the copolymer on the sol–gel transition were investigated. Proton nuclear magnetic resonance (¹H NMR) and gel permeation chromatography measurements were used to characterize the structure of the synthesized copolymers. The self‐assemble behavior and critical micelle concentration of the amphiphilic copolymers were estimated in phosphate buffer solution using fluorescence spectroscopy. The gelling behavior was measured by using tube inversion method. At pH 7.4, all copolymer solutions prepared 20 wt% concentration indicated sol–gel transition with increasing temperature. In vitro degradation experiments displayed that the synthesized graft copolymers mostly degraded hydrolytically within 20 days under physiological conditions. In order to investigate the potential application of synthesized hydrogels in drug delivery, Methylene Blue was used and approximately 70% of the loaded amount was released in 120 hr. The findings indicate that obtained graft copolymers can be used as injectable biodegradable carriers for pharmaceutical drugs. Copyright © 2015 John Wiley & Sons, Ltd.     

An ITO Based Disposable Biosensor for Ultrasensitive Analysis of Retinol Binding Protein

A highly sensitive electrochemical biosensor based on anti‐RBP biorecognition capable to analyze concentrations of retinol binding protein (RBP) was developed. The construction of the biosensor interfaces was carefully characterized by techniques such as electrochemistry, EIS, and scanning electron microscopy. In order to characterize impedance data, Kramers‐Kronig Transform was performed on the experimental impedance data. Besides, for an immunosensor system the Single Frequency Impedance technique was firstly used for the characterization of the interaction between RBP and anti‐RBP. Finally, artificial serum samples spiked with RBP were analyzed by the proposed ITO based immunosensor to investigate the usefulness of the biosensor for early biomarker diagnosis.     

Synthesis of Dihydropyrans and Dihydrofurans via Radical Cyclization of Unsaturated Alcohols and 1,3‐Dicarbonyl Compounds

The oxidative cyclization reactions of 1,3‐dicarbonyl compounds 1a – 1c and α,β‐unsaturated alcohols 2a – 2f with Mn(OAc)₃ were performed, leading to dihydrofurans. Treatment of 1a and 1b with 2‐methylbut‐3‐en‐2‐ol ( 2a ) gave dihydrofurans 3aa and 3ba , and dihydropyrans 4aa and 4ba , as unexpected products. While the reaction of 2‐methylbut‐3‐yn‐2‐ol ( 2b ) with acetylacetone ( 1b ) yielded a bifuran, ethyl acetoacetate ( 1a ) led to a mixture of furan, bifuran, and salicylate derivatives. Besides, surprisingly, styryl‐substituted dihydrofurans were obtained from the reactions of 1,3‐dicarbonyl compounds and (3E)‐2,4‐diphenylbut‐3‐en‐2‐ol. The reaction mechanisms were proposed for the formation of the different products, considering intermediates in these reaction mixtures.     

Synthesis and Structural Characterization of Pyrrole Heterocyclic Systems Bearing Amino Acid Units: Novel Pyrrol‐3‐ones,Pyrrolo[1,2‐a][3,1]benzoxazines,and Pyrrolo[2,1‐b][1,3]oxazoles

Furan‐3‐one derivatives 1 were converted into 2‐hydroxy‐pyrrole‐3‐ones 4 by reacting with various α‐ and β‐amino acids. In contrast, the reaction of furan‐3‐ones and 1‐aminocyclobutanecarboxylic acid afforded spiro‐pyrrolo[2,1‐b][1,3]oxazoles 5 via the pyrrole‐3‐one intermediate under the same reaction conditions. Some of 2‐hydroxy‐pyrrole‐3‐ones 3 derived from anthranilic acids were transformed to pyrrolo[1,2‐a][3,1]benzoxazines via intramolecular esterification.