Explicit algebraic Reynolds stress model (EARSM) for compressible shear flows

We develop an explicit algebraic Reynolds stress model (EARSM) for high-speed compressible shear flows and validate the model with direct numerical simulation (DNS) data of homogeneous shear flow and experimental data of high-speed mixing-layers. Starting from a pressure–strain correlation model that incorporates compressibility effects, the weak-equilibrium assumption is invoked to derive the EARSM closure expression. The resulting closure is fully explicit and physically realizable and is a function of mean flow strain rate, rotation rate, turbulent kinetic energy, dissipation rate, and gradient Mach number. Homogeneous shear flow calculations show that the model captures the asymptotic behavior of DNS quite well. Linear EARSM calculations of a plane supersonic mixing-layer are performed, and comparison with experimental data shows good agreement. Salient results are agreement of streamwise velocity similarity profiles, mixing-layer spreading rates, and capturing the Langley curve trend.     

Cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction and HPLC–DAD analysis of ezetimibe and simvastatin in human plasma and urine

A new cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction (CA–HF–SLPME) followed by high‐performance liquid chromatography–diode array detection (HPLC–DAD) method was developed for simultaneous determination of ezetimibe and simvastatin in human plasma and urine samples. To prepare the CA–HF–SLPME device, the cetyl‐alcohol was immobilized into the pores of a 2.5 cm hollow fiber micro‐tube and the lumen of the micro‐tube was filled with 1‐octanol with the two ends sealed. Afterwards, the prepared device was introduced into 10 mL of the sample solution containing the analytes with agitation. Under optimized conditions, calibration curves plotted in spiked plasma and urine samples were linear in the ranges of 0.363–25/0.49–25 μg L^?1 for ezetimibe/simvastatin and 0.193–25/0.312–25 μg L^?1 for ezetimibe/simvastatin in plasma and urine samples, respectively. The limit of detection was 0.109/0.174 μg L^?1 for ezetimibe/simvastatin in plasma and 0.058/0.093 μg L^?1 for ezetimibe/simvastatin in urine. As a potential application, the proposed method was applied to determine the concentration of selected analytes in patient plasma and urine samples after medication and satisfactory results were achieved. In comparison with reference methods, the CA–HF–SLPME–HPLC–DAD method demonstrates considerable potential in the biopharmaceutical analysis of selected drugs.     

Experimental Investigation of the Mechanical Behavior and Permeability of 3D Printed Sandstone Analogues Under Triaxial Conditions

Transport in Porous Media - Consolidated drained triaxial tests arise as one of the most exhaustive methods to quantify the strength, volumetric behavior and failure process of rocks. Understanding...     

High resolution spectroscopy of (lambda)(12)B by electroproduction

An experiment measuring electroproduction of hypernuclei has been performed in hall A at Jefferson Lab on a 12C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a ring imaging Cherenkov detector were added to the hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed (Lambda)(12)B spectrum shows for the first time identifiable strength in the core-excited region between the ground-state s-wave Lambda peak and the 11 MeV p-wave Lambda peak.     

Prandtl number effects in decaying homogeneous isotropic turbulence with a mean scalar gradient

Decaying homogeneous isotropic turbulence with an imposed mean scalar gradient is investigated numerically, thanks to a specific eddy-damped quasi-normal Markovian closure developed recently for passive scalar mixing in homogeneous anisotropic turbulence (BGC). The present modelling is compared successfully with recent direct numerical simulations and other models, for both very large and small Prandtl numbers. First, scalings for the cospectrum and scalar variance spectrum in the inertial range are recovered analytically and numerically. Then, at large Reynolds numbers, the decay and growth laws for the scalar variance and mixed velocity–scalar correlations, respectively, derived in BGC, are shown numerically to remain valid when the Prandtl number strongly departs from unity. Afterwards, the normalised correlation ρ_wθ is found to decrease in magnitude at a fixed Reynolds number when Pr either increases or decreases, in agreement with earlier predictions. Finally, the small scales return to isotropy of the scalar second-order moments is found to depend not only on the Reynolds number, but also on the Prandtl number.     

Chitosan loaded with silver nanoparticles,CS‐AgNPs,using thymus syriacus,wild mint,and rosemary essential oil extracts as reducing and capping agents

The present study describes the green method for the preparation of chitosan loaded with silver nanoparticles (CS‐AgNPs) in the presence of 3 different extracted essential oils. The essential oils play dual roles as reductant and capping agents. The reducing power and DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) assay for the 3 essential oils—Thymus syriacus (T), wild mint (M), and rosemary (R)—have been reported. The preparation of CS‐AgNPs was performed by 2 steps. The 3 previously extracted essential oils have been used as reducing and capping agent in the first step, while in the second step, silver nanoparticles were integrated in chitosan. The integration of AgNPs in the structure of chitosan was confirmed by ultraviolet‐visible, Fourier transform infrared spectroscopy, scanning electron microscopy techniques, and energy dispersive X‐ray. Surface plasmon resonance confirmed the formation of CS‐AgNPs with maximum absorbance at λ_max between 405 ‐ 410 and 410 ‐ 430 nm for colloidal and films of CS‐AgNPs, respectively. The intensity of bands at 3408 cm^?1 in the fourier transform infrared spectroscopy measurements was decreased substantially and shifted slightly to lower frequency (?υ = 43 cm^?1). Scanning electron microscopy shows a spherical morphology of AgNPs with size of 62 nm for both colloidal and film samples, and energy dispersive X‐ray analysis shows peaks confirming AgNPs formation.     

Girard-P derivative of 2-pyridinecarboxaldehyde as analytical reagent. Spectrophotometric determination of copper

The synthesis, characteristics, properties, and reactions with metallic ions of pycolinaldehyde derivatives of Girard-P reagent have been studied. The reagents form complexes with Cu(II), Ni(II), Co(II), Hg(II) and (I), Zn(II), Cd(II), and Fe(III), and (II), which exhibit a good sensibility but whose spectra have the absorption maxima located in the ultraviolet zone. The spectrum of copper complex in the presence of ascorbic acid shows another absorption band at the visible region and this makes the spectrophotometric determination of copper very selective. The influence of the different experimental parameters on the formation of copper complex without ascorbic acid and with this compound was studied, and the optimum conditions for the determination of copper were established. The precision of the procedure, expressed in terms of relative standard deviation, was 1.1%. The method has been tested on “white metal E-8” samples.