New Answers on the Interaction Between Polymers and Vortices in Turbulent Flows

Numerical data of polymer drag reduced flows is interpreted in terms of modification of near-wall coherent structures. The originality of the method is based on numerical experiments in which boundary conditions or the governing equations are modified in a controlled manner to isolate certain features of the interaction between polymers and turbulence. As a result, polymers are shown to reduce drag by damping near-wall vortices and sustain turbulence by injecting energy onto the streamwise velocity component in the very near-wall region.     

Emergy-based exergoeconomic and exergoenvironmental evaluation of a combined power and cooling system based on ORC-VCR

Journal of Thermal Analysis and Calorimetry - Ensuring efficient operation of energy conversion systems in terms of economics and ecology is a prime objective that should be addressed within the...     

Detection of Aeromonas hydrophila DNA oligonucleotide sequence using a biosensor design based on Ceria nanoparticles decorated reduced graphene oxide and Fast Fourier transform square wave voltammetry

A new strategy was introduced for ssDNA immobilization on a modified glassy carbon electrode. The electrode surface was modified using polyaniline and chemically reduced graphene oxide decorated cerium oxide nanoparticles (CeO₂NPs-RGO). A single-stranded DNA (ssDNA) probe was immobilized on the modified electrode surface. Fast Fourier transform square wave voltammetry (FFT-SWV) was applied as detection technique and [Ru(bpy)₃]^2+/3+ redox signal was used as electrochemical marker. The hybridization of ssDNA with its complementary target caused a dramatic decrease in [Ru(bpy)₃]^2+/3+ FFT-SW signal. The proposed electrochemical biosensor was able to detect Aeromonas hydrophila DNA oligonucleotide sequence encoding aerolysin protein. Under optimal conditions, the biosensor showed excellent selectivity toward complementary sequence in comparison with noncomplementary and two-base mismatch sequences. The dynamic linear range of this electrochemical DNA biosensor for detecting 20-mer oligonucleotide sequence of A. hydrophila was from 1 × 10⁻¹⁵ to 1 × 10⁻⁸ mol L⁻¹. The proposed biosensor was successfully applied for the detection of DNA extracted from A. hydrophila in fish pond water up to 0.01 μg mL⁻¹ with RSD of 5%. Besides, molecular docking was applied to consider the [Ru(bpy)₃]^2+/3+ interaction with ssDNA before and after hybridization.     

Development of dispersive liquid-liquid microextraction combined with gas chromatography-mass spectrometry as a simple, rapid and highly sensitive method for the determination of phthalate esters in water samples

A simple, rapid and efficient method, the dispersive liquid-liquid microextraction (DLLME) in conjunction with gas chromatography-mass spectrometry (GC-MS), has been developed for the extraction and determination of phthalate esters (dimethyl phthalate, diallyl phthalate, di-n-butyl phthalate, benzyl butyl phthalate, dicyclohexyl phthalate and di-2-ethylhexyl phthalate) in water samples. Factors relevant to the microextraction efficiency, such as the kind of extraction, the disperser solvent and their volume, the salt effect and the extraction time were investigated and optimized. Under the optimized extraction conditions (extraction solvent: chlorobenzene, volume, 9.5microL; disperser solvent: acetone, volume, 0.50mL, without salt addition and extraction time below 5s), the figures of merit of the proposed method were evaluated. The values of the detection limit of the method were in the range of 0.002-0.008microgL(-1), while the RSD% value for the analysis of 1microgL(-1) of the analytes was below 6.8% (n=4). A good linearity (0.9962>/=r(2)>/=0.9901) and a broad linear range (0.02-100microgL(-1)) were obtained. The method exhibited enrichment factors and recoveries, ranging from 681 to 889 and 68.1 to 88.9%, respectively, at room temperature (25+/-1 degrees C). Finally, the proposed method was successfully utilized for the preconcentration and determination of the phthalate esters in different real water samples and satisfactory results were obtained.     

Inexpensive vibrational anharmonicities from estimated derivatives: Diatomic molecules

Four alternatives are compared for estimating vibrational anharmonicity constants without explicitly calculating the expensive fourth derivatives of the potential curves. In the first, semiempirical approach, fourth derivatives for 53 diatomic molecules are estimated from ab initio second and third derivatives by using the Morse model potential. Vibrational anharmonicities ω_ex_e are then computed from the third and fourth derivatives. The second approach invokes a purely empirical linear correlation between ω_ex_e and the harmonic frequencies ω_e. The third and fourth empirical approaches suppose that the effective harmonic and anharmonic force constants are proportional (with an additive constant in the fourth approach). Experimental values for ω_ex_e are compared with empirical predictions and with semiempirical estimates based upon Hartree–Fock (HF), Møller–Plesset (MP2), and local, nonlocal, and hybrid density-functional theories (DFT), using the small 6-31G* basis set. Ab initio values of ω_e and bond lengths r_e are also compared against experiment. The (U)MP2 results are the worst and include several anomalies. The other semiempirical methods yield results of comparable accuracy for ω_ex_e of hydrides, although the DFT methods are markedly better for ω_e and r_e and for ω_ex_e of nonhydrides. The empirical estimates are nearly as good as the semiempirical ones. We conclude that: (1) both empirical and semiempirical approximations are useful for predicting stretching anharmonicity constants ω_ex_e to precisions of σ≈5 cm⁻¹ for hydrides and σ≈1.5 cm⁻¹ for nonhydrides; and (2) MP2 theory is relatively unreliable for such calculations. In addition, we find the following tests to be useful when evaluating the reliability of vibrational constants calculated at the UMP2 level: (a) the calculated values of ω_e and ω_ex_e should not deviate substantially from the empirical relations; (b) harmonic frequencies and intensities calculated at the MP2 level should be smaller than those calculated at the corresponding HF level; (c) a large distance-dependence of the spin contamination, d〈S²〉/dR≳0.05 Å⁻¹, suggests that calculated constants are too large. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1315–1324, 1998     

Ultrasensitive flow-injection electrochemical method for detection of anticancer drug tamoxifen

This paper presents the optimization of instrumental and solution parameters for determination of tamoxifen in urine and plasma and formulation by fast Fourier transform square wave voltammetry (SWV) using a gold microelectrode in flow-injection system. The samples are subjected by the same buffer solution and are injected in the flow-injection apparatus. By applying a novel square wave voltammetry method to perform as a sensitive method the voltamograms are recorded. The method used for determination of tamoxifen by measuring the changes in admittance voltammogram of a gold ultramicroelectrode (in 0.05 mol L^?1 H₃PO₄ solution) caused by adsorption of the tamoxifen on the electrode surface. The best sensitivity was achieved using a frequency of 600 Hz and a medium composed of 0.05 mol L^?1 phosphate buffers at pH 2.0. The best performance was obtained with the pH value of 2, pulse amplitude 25 mV, frequency 600 Hz, accumulation potential of ?100 mV and accumulation time of 0.5 s. Furthermore, signal-to-noise ratio has significantly increased by application of discrete fast Fourier transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. Calibration plots are given for solutions containing 1.0 × 10^?11 to 3.0 × 10^?6 mol L^?1 of tamoxifen. The detection limit is calculated to be 3.0 × 10^?12 mol L^?1 (～2 pg mL^?1). The relative standard deviation at concentration 2.0 × 10^?8 M is 6.1% for five reported measurements.     

A Ru-Complex Tethered to a N-Rich Covalent Triazine Framework for Tandem Aerobic Oxidation-Knoevenagel Condensation Reactions

Herein, a highly N-rich covalent triazine framework (CTF) is applied as support for a Ru^III complex. The bipyridine sites within the CTF provide excellent anchoring points for the [Ru(acac)₂(CH₃CN)₂]PF₆ complex. The obtained robust Ru^III@bipy-CTF material was applied for the selective tandem aerobic oxidation-Knoevenagel condensation reaction. The presented system shows a high catalytic performance (>80% conversion of alcohols to α, β-unsaturated nitriles) without the use of expensive noble metals. The bipy-CTF not only acts as the catalyst support but also provides the active sites for both aerobic oxidation and Knoevenagel condensation reactions. This work highlights a new perspective for the development of highly efficient and robust heterogeneous catalysts applying CTFs for cascade catalysis.     

Experimental study of a large plastic scintillator response with different reflective coverings based on digital pulse processing method

Journal of Radioanalytical and Nuclear Chemistry - Digital pulse processing methods have various applications in radiation spectroscopy due to their unique properties. Here, the effect of light...     

Universally Catenarian Integral Domains,Strong S-Domains and Semistar Operations

Let D be an integral domain and a semistar operation stable and of finite type on it. In this article, we are concerned with the study of the semistar (Krull) dimension theory of polynomial rings over D. We introduce and investigate the notions of -universally catenarian and -stably strong S-domains and prove that, every -locally finite dimensional Prüfer -multiplication domain is -universally catenarian, and this implies -stably strong S-domain. We also give new characterizations of -quasi-Prüfer domains introduced recently by Chang and Fontana, in terms of these notions.     

Rapid and Direct Spectrofluorometric and Chemometrics Methods for the Simultaneous Determination of Two Dansyl Derivatives

ABSTRACT

In this study the simultaneous molecular spectrofluorometric determination of ultratrace amounts of two dansyl chloride derivatives, DMNPS (5-(dimethylamino)naphthalene-1-sulfonyl 4-phenylsemicarbazide) and DMNPH (2-(5-(dimethylamino)naphthalen-1-ylsulfonyl)-N-phenylhydrazinecarbothioamide), was accomplished using a genetic algorithm joint partial least squares (GA-PLS) technique that leads to very low detection limits (lower than 10^?6 mol/L) The linear dynamic ranges of the compounds were 1–6 µ mol L^?1 and 1–7 µ mol L^?1 for DMNPS and DMNPH, respectively. Quantification was performed using the emission wavelength range from 360 to 600 nm with an optimum calibration sample number of 25 and prediction sample number of 7. The technique was proved to be beneficial.