Numerical simulation of compressible multiphase flows

The present work is motivated by the pervasive nature of compressible multiphase flow in practical applications. These flows often feature particles (i.e. solid particles, droplets or bubbles) and develop rich dynamics as particles interact with different flow features such as shock waves. These interactions present unique challenges for numerical methods. The underlying primary motivation is to judiciously exploit shock-particle interaction in different flow topology, e.g. in gas-solid and gas-liquid systems, with proper and efficient methods. In the first part, the interaction of shock wave with a particle cloud in dense gas-solid regime is investigated through a particle resolved direct numerical simulation to quantify the unsteadiness and velocity fluctuations, arising from this interaction, in the particle cloud and the wake behind that. This investigation is performed using a Particle-Resolved Direct Numerical Simulation (PR-DNS) by solving the compressible Navier-Stokes equations coupled with a compressible Immersed Boundary Method (IBM), to account for the particles, in the Parallel Adaptive Wavelet-Collocation Method (PAWCM) framework. The PAWCM is a finite difference framework that uses wavelets to dynamically adapt the grid used to represent the solution, which minimizes the overall computational cost and allows larger simulations to be performed. The quantification is performed in three steps. First the simulation of simplified case of the shock interaction with a transverse array of particles is performed to reveal the source of unsteadiness under the wave-wave and wave wake interaction of the neighboring particles and introduce the dilatation effect arise over the particle wake. Then the interaction of the shock wave with the particle cloud is investigated to replicate the experimental canonical multiphase shock tube problem of Wagner et al. (2011). The budget of the vorticity equation explains the sources of strong unsteadiness in the particle cloud that previously was observed by Regele et. al (2014). In the third step the particle cloud is exposed to a compression wave that gradually introduce the flow. A detailed analysis of the velocity fluctuation and kinetic energy in the fluctuating motion is performed for both cases to ascertain the importance of the velocity fluctuations that arise from the strong unsteadiness in the shock induced case. In the second part, a finite difference solver is developed for Parallel adaptive Wavelet Collocation method framework to investigate high-speed compressible gas-liquid flows with surface tension effects. This study is motivated by gaining deeper insight into the process of fuel atomization in a supersonic cross flow of supersonic combustors under the startup conditions. The solver is developed based on the five equation interface capturing scheme by solving compressible multiphase/multicomponent Navier-Stokes equations along with an advection equation for the material interface. An interface capturing scheme is applied to counter the numerical diffusion induced by shock capturing scheme and maintain the immiscibility condition at the material interface. The capillary force is modeled using a continuous surface approach. The gas phase is modeled as an ideal gas and the liquid phase is modeled using a stiffened-gas equation of state. Capability of the model is demonstrated by several one and two dimensional benchmark problem. In the third part a finite volume shock/interface capturing scheme is developed for two phase flows based on the extension of single phase all-speed simple low-dissipation AUSM (SLAU) scheme. SLAU is the latest version of the AUSM-family schemes with a new numerical flux function which features low dissipation without any tunable parameters in low Mach number regimes while maintaining the robustness of AUSM-family fluxes at high Mach numbers with a very simple formulation. To demonstrate the accuracy of the method, it has been tested on the well known two-fluid air/water flow benchmark problems and the results were compared with the two-phase AUSM+ and AUSM+-up schemes. Finally the scheme was applied for the problem of shock particle cloud interaction to solve the phasic averaged governing equations along with the k-ϵ model to attempt modeling the unclosed terms

Systematic Modeling of Drug P-Glycoprotein Interactions via Combined Docking/QM Approach

Introduction: The overexpression of P-gp in cancer tumor cells results in increased efflux of chemotherapeutic compounds. This phenomenon leads to the wide-spectrum resistance of cancer cells to variant drugs or multi drug resistance (MDR). Regarding the important biological role of P-gp with regard to cancer therapy, in silico analysis of binding affinity/mode of diverse anticancer drugs toward P-gp may be an active area of research since it provides more insight into the binding interactions and key amino acid residues that were involved. Methods and Results: Ligand-flexible docking studies were performed using the molecular docking software, AutoDock 4.2. To elucidate the interactions of selected anticancer drugs, all the related structures were docked into the active site of validated P-gp target (4XWK). Quantum mechanical calculations were applied to intermolecular binding energy analysis in terms of drug-residue binding interactions via functional B3LYP in association with split valence basis set using polarization functions (Def2-SVP). Mitomycin was found to be the weakest binder with -7.29 kcal/mol energy. Bisantrene was the top-ranked binder (-10.59 kcal/mol) with H-bond and lipophilic interaction patterns. To explain more, Asn838 participated in bidentate H-bonding with nitrogen atom of imidazole ring. Another H-bond interaction was detected in the case of Ser725 within the same ring but different nitrogen atom of the drug molecule. Besides hydrogen bonding, it was revealed that 12 hydrophobic residues interacted with Bisantrene. Within the evaluated drugs, unlike Epothilone E and F, no H-bonds could be detected for Epothilone A, B, C & D. Such observation was pertained to the presence of hydroxymethyl moiety on the thiazole ring of Epothilone E and F which provided well-oriented H-bonds with Ala307. Despite observed interactive residues, lower binding affinity of Epothilone F persuaded us to run QM job in terms of drug-residue binding interactions. It was interestingly concluded that a few residues made repulsive forces with the drug, a result that might explain lower affinity of this molecule toward P-gp. Conclusions: Collective in silico exploration of a few anticancer drugs provided some insights into the binding mode toward P-gp as an interfering target in chemotherapeutic strategies. On the basis of obtained results, structure binding relationship pattern for studied anticancer drugs were developed

Development and optimization of the new ultrasonic-infrared-vacuum dryer in drying Kelussia odoratissima and its comparison with conventional methods

Among the post-harvest processing of medicinal plants, drying is an important and influential process. Given the numerous applications of medicinal plants, especially Kelussia odoratissima, in the food and pharmaceutical industries, the aim of this study was to compare the effects of the ultrasound-infrared radiation-vacuum method with conventional drying methods on the drying time, the total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity of K. odoratissima. ANOVA result showed that the effects of drying methods, drying temperature and their interaction effect on phenolic, flavonoid and antioxidant content were significant at 1% probability level. In the ultrasound-IR-vacuum method, by increasing temperature from 40 °C to 80 °C, the TFC increased by 35%. The highest antioxidant capacity was obtained for dry shade treatment, followed by dry sun treatment and three temperatures, i.e., 40 °C, 60 °C and 80 °C, in the combined method. The proposed optimal temperatures for the hot air, IR, and ultrasonic drying, were 63 °C, 66 °C and 71 °C, respectivel

The effect of L-carnitine on Oocyte Mitochondrial Activity after Cryopreservation

Background: Mitochondria are cellular organelles required for energy production, vital to reproduction, especially oocyte maturation and fertilization. It has been seen that oocyte cryopreservation (OC) can cause mitochondria damage, aggregation of lipid droplets near mitochondria and endoplasmic reticulum, and cryoinjury. In recent studies use of antioxidants such as L- carnitine can increase the number of active mitochondria and decrease intracellular ROS levels. The present study aimed to determine the beneficial effect of L –carnitine on oocyte mitochondrial activity after vitrification. Materials and Methods: In the present experimental study, 6-8 weeks of female NMRI mice were taken from the Royan Institute of Iran and stimulated with 7.5 IU Pregnant Mare Serum Gonadotrophin (PMSG) and 10 IU of human chorionic gonadotropin (HCG) after 48 hours was injected. After stimulation, oocytes were collected, and MII oocytes were selected. A two-step vitrification procedure was done, and 0.6mg/ml of L –carnitine was added to both ES and VS mediums. After two weeks, oocyte thawing was performed, intracellular GSH level was also measured mitochondrial membrane potential was measured. Captured images were analyzed by J software (Version 1.40; and obtained data were analyzed using SPSS Ver.20. Results: Average difference in intracytoplasmic GSH level in the study group was significantly higher than the control group (P<0.001). So, L –carnitine could successfully increase the oocyte intracytoplasmic GSH level. Also, it has been seen that the LC supplement could successfully grow oocyte mitochondrial function and subsequent mitochondrial membrane potentials(P<0.001). Conclusion: Adding LC to the cryopreservation media could increase mitochondrial activity, GSH level, and mitochondrial membrane potentials. Adding LC to the cryopreservation could enjoy the beneficial effect of L –carnitine on oocyte mitochondrial activity after vitrification and minimize mitochondrial damage and boost oocyte quality which can lead to successful fertilization and embryo growth

The effect of atmospheric pressure cold plasma on the inactivation of Escherichia coli in sour cherry juice and its qualitative properties

One of the nonthermal methods is the atmospheric pressure cold plasma (APCP). In this study, the effect of cold plasma on the reduction of Escherichia coli bacteria and qualitative properties of sour cherry juice, including total phenolic content (TPC), total anthocyanin content (TAC), and vitamin C, were investigated. Independent variables included plasma exposure time (1, 5, and 9 min), applied field intensity (25, 37.5, and 50 kV/cm), feeding gas oxygen content (0%, 0.5%, and 1%), and sample depth (0.5, 1, and 1.5 cm). The results show that increased oxygen content in argon has the greatest effect on the reduction of bacteria, and plasma exposure decreased 6 logarithmic periods of E. coli bacteria in sour cherry juice. Optimization results showed when all bacteria were eliminated by plasma, TPC remained unchanged, and TAC and vitamin C decreased by 4% and 21%, respectively, while thermal methods increased TPC by 23% and decreased TAC and vitamin C by 26% and 77%, respectively. These results indicate that, compared with conventional thermal methods, sour cherry juice pasteurization using APCP has little effect on the juice qualitative properties, and this method can serve as a suitable alternative to conventional thermal methods. Keywords:cold plasma; Escherichia coli; nonthermal method; response surface method; sour cherry juic

Selective Iodination of Alcohols with NaI/Amberlyst 15 in Acetonitrile

Abstract: A simple and effective procedure for conversion of primary, secondary, allylic and benzylic alcohols into the corresponding iodides is described using NaI/Amberlyst 15 in acetonitrile at room temperature. Selective conversion of benzylic alcohols in the presence of saturated alcohols into the corresponding benzylic iodides is achieved under these conditions

Analysis of the combinative effect of ultrasound and microwave power on Saccharomyces cerevisiae in orange juice processing

High temperature in conventional method for juice pasteurization causes adverse effects on nutrients and nutritional value of food. The objective of this study was to examine the effect of microwave output power, temperature, ultrasound power, and ultrasonic exposure time on Saccharomyces cerevisiae in orange juice. Based on our findings, microwave output power, ultrasound power, ultrasonic exposure time orange juice temperature were the most effective factors to reduce S. cerevisiae. The results showed that the quadratic model included was the best model for account. The model showed that regarding decrease of S. cerevisiae account microwave-induced temperature was more effective than microwave output power. Also, compared to microwave power, the ultrasound power was more effective on S. cerevisiae reduction. The optimum processing condition was 350 W microwave power, 35 °C temperature, 778.2 W ultrasonic power, and 11 min of exposure. Based on our result, the consumption energy was 142.77 J/mL with no remaining of S. cerevisiae. The results showed that the given scores by panelists to the combinative and conventional methods for color and flavor indices were significant (P b 0.05). Industrial Relevance: In order to reduce the adverse effects (loss of vitamins, flavor, and non-enzymatic browning) of the thermal pasteurization method, other methods capable of inactivation of microorganisms can be applied. In doing so, non-thermal methods are of interest, including pasteurization using high hydrostatic pressure processing (HPP), electric fields, and ultrasound waves. The ultrasound technology has been the main focus of studies in recent years. However, the main challenge facing the non-thermal technologies in food processing is the inactivation of pathogenic microorganisms and food spoilage agents, which can be achieved by various methods. The aim of present research was examined simultaneous effect of ultrasonic and microwave to remove microorganism. This research introduces new, innovative, and combined method for fruit juice pasteurization, and this method can benefit the food industry

A glance at black cumin(Nigella sativa) and its active constituent, thymoquinone, in ischemia: a review

Objective(s): Black cumin (Nigella sativa) belonging to Ranunculaceae family has a long history of medicinal use in various folk and traditional systems of medicine, including Iranian traditional medicine (ITM). These valuable medicinal seeds have been used traditionally against a variety of diseases such as dyspepsia, diabetes, headache, influenza and asthma. In addition, several scientific investigations have reported the therapeutic properties of N. sativa and thymoquinone (TQ), one of the most important constituent of black cumin, for treatment of a large number of diseases, including ischemia. As there is no comprehensive review study about the anti-ischemic activity of black cumin and its mechanism of action, in the current study, we aimed to review the anti-ischemic activities of N. sativa and TQ in different organ-related disorders. Materials and Methods: We searched the words N. sativa or black cumin and ischemia in the combination of related organs through available databases including Scopus, Web of science, and Google scholar. Results: Several studies were found reporting the anti-ischemic activity of black cumin and its active constituent on different organs including brain, kidneys, heart, and liver. Black cumin exert its beneficial effects as an antioxidant, anti-inflammatory, anti-apoptosis, and anti-necrosis agent though inhibition of growth factors, biochemical and oxidative stress markers and regulating gene expression. Conclusion: Thus, N. sativa could be a potential candidate for treatment of ischemia related disorders in key organs such as brain, liver, digestive system, kidney, and heart. To figure out the exact mechanism of action, further investigations are proposed in this regard

Sensitivity and specificity of chest computed tomography scan based on RT-PCR in COVID-19 diagnosis

Purpose: COVID-19 is a novel, severely contagious and progressive infection occurring worldwide. The diagnosis of the disease is based on real-time polymerase chain reaction (RT-PCR) and computed tomography (CT) scan, even though they are still controversial methods. Material and methods: We studied 54 patients with suspected COVID-19 and the two mentioned methods were compared with each other. Results: Sensitivity and specificity of the abnormal chest CT scan, ground-glass opacity (GGO), consolidation opacity, and both of GGO and consolidation were also surveyed based on RT-PCR. The results showed that RT-PCR assay was negative in 23 (42.6%) patients and positive in 31 (57.4%) cases. Also, the patients with an abnormal chest CT scan comprised 37 (68.5%). The sensitivity and specificity of abnormal CT scan were 78.6% and 42.3%, respectively, based on the RT-PCR method. Conclusions: Other techniques alongside CT scan and RT-PCR are advocated for accuracy of the COVID-19 diagnosis