Impact erosion prediction using the finite volume particle method with improved constitutive models

Erosion damage in hydraulic turbines is a common problem caused by the high- velocity impact of small particles entrained in the fluid. In this investigation, the Finite Volume Particle Method is used to simulate the three-dimensional impact of rigid spherical particles on a metallic surface. Three different constitutive models are compared: the linear strain- hardening (L-H), Cowper-Symonds (C-S) and Johnson-Cook (J-C) models. They are assessed in terms of the predicted erosion rate and its dependence on impact angle and velocity, as compared to experimental data. It has been shown that a model accounting for strain rate is necessary, since the response of the material is significantly tougher at the very high strain rate regime caused by impacts. High sensitivity to the friction coefficient, which models the cutting wear mechanism, has been noticed. The J-C damage model also shows a high sensitivity to the parameter related to triaxiality, whose calibration appears to be scale-dependent, not exclusively material-determined. After calibration, the J-C model is capable of capturing the material’s erosion response to both impact velocity and angle, whereas both C-S and L-H fail

Finite Volume Particle Method for Fluid-Structure Interaction

We have recently developed a conservative finite volume particle method (FVPM) that can efficiently model 2-D and 3-D fluid flow with free-surfaces and complex geometries. Tn this paper we present an extension of the method to fluid-structure interaction. A new boundary condition enforcement is presented in which the hydrodynamic forces required in solid equations are computed directly. For validation, we study the 2-D motion of fluid through an elastic gate and compare the displacement of the gate with experimental and numerical data. We observe a very good agreement between FVPM and other numerical and experimental data

Scolicidal effects of black cumin seed (Nigella sativa) essential oil on hydatid cysts

Abstract: Surgery remains the preferred treatment for hydatid cyst (cystic echinococcosis, CE). Various scolicidal agents have been used for inactivation of protoscolices during surgery, but most of them are associated with adverse side effects. The present study aimed to evaluate the in vitro scolicidal effect of Nigella sativa (Ranunculaceae) essential oil and also its active principle, thymoquinone, against protoscolices of hydatid cysts. Protoscolices were aseptically aspirated from sheep livers having hydatid cysts. Various concentrations of the essential oil (0.01-10 mg/ml) and thymoquinone (0.125-1.0 mg/ml) were used for 5 to 60 min. Viability of protoscolices was confirmed by 0.1% eosin staining. Furthermore, the components of the N. sativa essential oil were identified by gas chromatography/mass spectroscopy (GC/MS). Our study revealed that the essential oil of N. sativa at the concentration of 10 mg/ml and its main component, thymoquinone, at the concentration of 1 mg/ml had potent scolicidal activities against protoscolices of Echinococcus granulosus after 10 min exposure. Moreover, thymoquinone (42.4%), p-cymene (14.1%), carvacrol (10.3%), and longifolene (6.1%) were found to be the major components of N. sativa essential oil by GC/MS analysis. The results of this study indicated the potential of N. sativa as a natural source for production of a new scolicidal agent for use in hydatid cyst surgery. However, further studies will be needed to confirm these results by checking the essential oil and its active component in in vivo models

In vitro lethal effects of various extracts of Nigella sativa seed on hydatid cyst protoscoleces

Objective(s): There are several scolicidal agents for inactivation of hydatid cyst protoscolices during surgery, but most of them are associated with adverse side effects such as sclerosing cholangitis and liver necrosis. The present study was aimed to evaluate scolicidal effects of various extracts of Nigella sativa seeds against protoscoleces of hydatid cyst in an in vitro model. Materials and Methods: Protoscoleces were aseptically aspirated from naturally infected livers of sheep and goats. Various concentrations of the different extracts of N. sativa (5 to 50 mg/ml) were used for 5 to 60 min. Viability of protoscoleces was confirmed by 0.1% eosin staining. Results: The findings exhibited that methanolic extract at the concentration of 50 mg/ml after 10 min of incubation, and aqueous extract at the concentration of 50 mg/ml after 30 min of incubation can kill 100% of protoscoleces. In addition, all of experiments revealed dose-dependent and also time-dependent scolicidal effect of various extracts of N. sativa on the protoscoleces of hydatid cyst. Conclusion: The results of the present study demonstrated that N. sativa may be a natural source for the production of new scolicidal agent for use in hydatid cyst surgery. However, further studies will be required to evaluate scolicidal effects of N. sativa in the in vivo model

Chemical composition and scolicidal activity of Zataria multiflora Boiss essential oil

Zataria multiflora Boiss (Lamiaceae) commonly grows in Iran is a popular medicinal plant with various pharmacological activities mentioned in traditional Iranian medicine and modern phytotherapy. This study was designed to evaluate the chemical composition and scolicidal effects of Z. multiflora essential oil on the protoscoleces of hydatid cysts on an in vitro model. The components of the Z. multiflora essential oil were identified by GC/MS analysis. Protoscoleces were aseptically aspirated from the livers of naturally infected sheep. Various concentrations of essential oil, thymol and carvacrol were used for 5–30 minutes. Eosin exclusion test was used to determine the viability of protoscoleces. The main components were thymol (41.8%), carvacrol (28.8%), and p-cymene (8.4%). Findings showed that essential oil at the concentrations of 12.5 and 6.25 μL/mL killed 100% protoscoleces after 5 and 20 minutes of exposure, respectively. In addition, thymol and carvacrol at the concentrations of 100 μg/mL and 100 μL/mL killed 100% protoscoleces after 10 minutes incubation, respectively. Obtained results in this investigation for the first time demonstrated that Z. multiflora essential oil and its main components might be a natural source for the production of new scolicidal agent

Evaluation of antileishmanial activity and cytotoxicity of the extracts of Berberis vulgaris and Nigella sativa against Leishmania tropica

Background & objectives: Leishmaniasis is a major public health problem, and the alarming spread of parasite resistance underlines the importance of discovering new therapeutic products. The present study aims to investigate the in vitro antileishmanial activity and cytotoxicity of the ethanolic extract of Berberis vulgaris fruits and chloroform extract of Nigella sativa seeds against Leishmania tropica. Methods: In this study, antileishmanial activity of B. vulgaris and N. sativa extracts on promastigote and amastigote stages of L. tropica in comparison to meglumine antimoniate (MA) was evaluated, using MTT assay and macrophage model, respectively. MTT test was also used to assess the cytotoxicity of extracts on murine macrophages. The significance of differences was determined by analysis of variances (ANOVA) and student’s t-test using SPSS software. Results: The results showed that ethanolic extract of B. vulgaris (IC50 4.83 μg/ml) and chloroform extract of N. sativa (IC50 7.83 μg/ml) significantly reduced the viability of promastigotes of L. tropica in comparison to MA (IC50 11.26 μg/ml). Furthermore, extracts of B. vulgaris (IC50 24.03 μg/ml) and N. sativa (IC50 30.21 μg/ml) significantly decreased the growth rate of amastigotes in each macrophage as compared with positive control (p <0.05). Our findings also revealed that extracts of B. vulgaris and N. sativa had no significant cytotoxicity against murine macrophages. Conclusion: The B. vulgaris and N. sativa extracts exhibited an effective leishmanicidal activity against L. tropica on in vitro model. Further, works are required to evaluate the exact effect of these extracts on Leishmania species using a clinical setting

Evaluation of antileishmanial activity and cytotoxicity of the extracts of Berberis vulgaris and Nigella sativa against Leishmania tropica

Background & objectives: Leishmaniasis is a major public health problem, and the alarming spread of parasite resistance underlines the importance of discovering new therapeutic products. The present study aims to investigate the in vitro antileishmanial activity and cytotoxicity of the ethanolic extract of Berberis vulgaris fruits and chloroform extract of Nigella sativa seeds against Leishmania tropica. Methods: In this study, antileishmanial activity of B. vulgaris and N. sativa extracts on promastigote and amastigote stages of L. tropica in comparison to meglumine antimoniate (MA) was evaluated, using MTT assay and macrophage model, respectively. MTT test was also used to assess the cytotoxicity of extracts on murine macrophages. The significance of differences was determined by analysis of variances (ANOVA) and student’s t-test using SPSS software. Results: The results showed that ethanolic extract of B. vulgaris (IC50 4.83 μg/ml) and chloroform extract of N. sativa (IC50 7.83 μg/ml) significantly reduced the viability of promastigotes of L. tropica in comparison to MA (IC50 11.26 μg/ml). Furthermore, extracts of B. vulgaris (IC50 24.03 μg/ml) and N. sativa (IC50 30.21 μg/ml) significantly decreased the growth rate of amastigotes in each macrophage as compared with positive control (p <0.05). Our findings also revealed that extracts of B. vulgaris and N. sativa had no significant cytotoxicity against murine macrophages. Conclusion: The B. vulgaris and N. sativa extracts exhibited an effective leishmanicidal activity against L. tropica on in vitro model. Further, works are required to evaluate the exact effect of these extracts on Leishmania species using a clinical setting