High-order ghost-point immersed boundary method for viscous compressible flows based on summation-by-parts operators

A high-order immersed boundary method is devised for the compressible Navier-Stokes equations by employing high-order summation-by-parts difference operators. The immersed boundaries are treated as sharp interfaces by enforcing the solid wall boundary conditions via flow variables at ghost points. Two different interpolation schemes are tested to compute values at the ghost points and a hybrid treatment is used. The first method provides the bilinearly interpolated flow variables at the image points of the corresponding ghost points and the second method applies the boundary condition at the immersed boundary by using the weighted least squares method with high-order polynomials. The approach is verified and validated for compressible flow past a circular cylinder at moderate Reynolds numbers. The tonal sound generated by vortex shedding from a circular cylinder is also investigated. In order to demonstrate the capability of the solver to handle complex geometries in practical cases, flow in a cross-section of a human upper airway is simulated.     

Synthesis,Characterization, and Catalytic Activity of Heteroleptic Rhodium Complex for C–N Couplings

Russian Journal of Coordination Chemistry - We have reported synthesis of complex [Rh(COD)(L{Me})Cl] (III), where L{Me} (II) is N-(1-methylpyridin-4(1H)-ylidene)benzamide and COD is...     

Ethylene to Propylene over Zeolite ZSM-5: Improved Catalyst Performance by Treatment with CuO

Russian Journal of Applied Chemistry - In this paper, the ZSM-5 zeolite base is used to produce light olefins in the process of converting ethylene to propylene, as well as copper oxide to improve...     

A simplified solution for piled-raft foundation analysis by using the two-phase approach

In common practice, the pile–soil–raft interaction still remains a challenging problem in the analysis of piled-raft foundations. In the present study, a simplified analytical approach is introduced to analyze a vertically-loaded piled-raft foundation by using a developed homogenization technique called the two-phase approach. In spite of classical and simplified methods in the literature, the proposed method considers the pile–soil interaction. The other major advantage is the ability to predict the axial pile load along the pile length. The problem is solved in the domain of elasticity and simple closed-form solutions are presented for the prediction of the settlement and the pile load sharing of a piled raft as well as the pile's axial force distribution along its length. The applicability of the proposed method is validated by considering case studies and field measurements. A comparison of the results indicates that the method can be utilized safely in a proper, quick, and effective manner with the least computational effort in comparison with sophisticated numerical approaches. The raft settlement can be accurately predicted while the pile load sharing might be over/under estimated. A parametric study is also carried out to investigate the response of piled-raft foundations including the influence of the parameters of the soil and the geometric characteristics of the piles.     

Stability study of the gastric floating dosage form of capecitabine

Since administration of capecitabine tablets leading to dose limiting makes the unfavorable toxicity, preparation of sustained-release tablets will overcome most of these side effects. The aim of this study was to prepare and study the stability of capecitabine sustained-release tablets. Sustained-release tablets of capecitabine were characterized by differential scanning calorimetry, X-ray diffraction, and infrared and ultraviolet spectroscopy techniques to determine the stability of the tablets. All tests carried out for tablets upon preparation as well as 6 and 12 months after preparation. The gradual decomposition of capecitabine sustained-release tablets stored at accelerated conditions (40 °C in 75 % of relative humidity) was indicated by decreasing values of peak purity and melting temperature, calculated from the Van’t Hoff equation. Except for the occurrence of one sharp peak for long-term stability and some sharp peaks in the accelerated condition, all peaks showed a crystallized nature. But the FTIR and UV results showed that there were no changes between the initial sustained-release tablets and stored tablets. Although the XRD results showed more peaks in the accelerated condition tablets, the crystalline form of capecitabine was maintained. These findings demonstrate that the capecitabine sustained-release tablet has excellent stability in normal and long-term storage conditions, with slight changes in the accelerated condition.     

Quantum dissipative Higgs model

By using a continuum of oscillators as a reservoir, we present a classical and a quantum-mechanical treatment for the Higgs model in the presence of dissipation. In this base, a fully canonical approach is used to quantize the damped particle on a spherical surface under the action of a conservative central force, the conjugate momentum is defined and the Hamiltonian is derived. The equations of motion for the canonical variables and in turn the Langevin equation are obtained. It is shown that the dynamics of the dissipative Higgs model is not only determined by a projected susceptibility tensor that obeys the Kramers–Kronig relations and a noise operator but also the curvature of the spherical space. Due to the gnomonic projection from the spherical space to the tangent plane, the projected susceptibility displays anisotropic character in the tangent plane. To illuminate the effect of dissipation on the Higgs model, the transition rate between energy levels of the particle on the sphere is calculated. It is seen that appreciable probabilities for transition are possible only if the transition and reservoir’s oscillators frequencies to be nearly on resonance.     

Determination of Methadone in Biological Samples Using Liquid Phase Microextraction with Back Extraction Combined with LC

Liquid phase microextraction with back extraction (LPME-BE) combined with liquid chromatography-ultra violet (LC-UV) was applied for the extraction and determination of methadone in biological fluids. At the optimized conditions, an enrichment factor of 386 and detection limit (LOD) of 0.2 μg L^?1 were obtained. The calibration curve was linear (r ² = 0.989) in the concentration range of 0.6–1,000 μg L^?1. Within-day relative standard deviation RSD (S/N = 3) and between-day RSD were 2.7 and 5.9%, respectively. The feasibility of the proposed method was evaluated by extraction and determination of methadone in plasma and urine samples and satisfactory results were obtained.     

Synthesis of 7-hydroxy-6H-benzo[c]chromen-6-ones based on a ‘[3+3] cyclization/domino retro-Michael-aldol-lactonization’ strategy

The TiCl₄-mediated [3+3] cyclization of 2,4-bis(trimethylsilyloxy)penta-1,3-diene with 3-silyloxyalk-2-en-1-ones afforded 2-acetylphenols, which were transformed into functionalized chromones. The Me₃SiOTf-mediated condensation of the latter with 1,3-bis(silyl enol ethers) and subsequent domino ‘retro-Michael-aldol-lactonization’ reaction afforded 7-hydroxy-6H-benzo[c]chromen-6-ones.