Showing papers by "Kuvempu University published in 2018"

Characterization, antibacterial, antioxidant, antidiabetic, anti-inflammatory and antityrosinase activity of green synthesized silver nanoparticles using Calophyllum tomentosum leaves extract

Abstract: The current research study is to develop an easy and eco-friendly method for the synthesis of AgNPs using aqueous leaf extract of Calophyllum tomentosum (CtAgNPs) and evaluated the extract to know the effects of anti-bacterial, antioxidant, anti-diabetic, anti-inflammatory and anti-tyrosinase activity. Using UV–vis spectrophotometer, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) characterized the Calophyllum tomentosum mediated silver nanoparticles. The leaf extract of C. tomentosum yielded flavonoids, saponins, tannins, alkaloids, glycosides, phenols, terpenoids and coumarins. AgNPs formation was confirmed by UV–vis spectra at 438 nm. Crystalline structure with a face centered cubic (fcc) of AgNPs was observed in XRD. FTIR had shown that the phytochemicals were responsible for the reduction and capping material of silver nanoparticles. The size and shape of the AgNPs were determined using SEM. From EDX study analysed the strong absorption property of AgNPs. The CtAgNPs have showed significant antibacterial activity on multi drug resistance bacteria. The CtAgNPs had shown strong antioxidant (DPPH, H2O2 scavenging, nitric oxide scavenging power, reducing power) activities. The CtAgNPs had strongly inhibited the α-glucosidase and DPPIV compared to α-amylase. The CtAgNPs exhibited strong anti-inflammatory activity (albumin denaturation, membrane stabilization, heat haemolytic, protein inhibitory, lipoxygenase, xanthine oxidase) and tyrosinase inhibitory activity. To our best knowledge, this is the first attempt on the synthesis of silver nanoparticles using Calophyllum tomentosum leaves extract. Hence, to validate our results the in vivo studies at molecular level are needed to develop an antioxidant, anti-diabetic and anti-inflammatory agent.

Effect of aluminium doping on structural, optical, photocatalytic and antibacterial activity on nickel ferrite nanoparticles by sol–gel auto-combustion method

Abstract: The present work designates the preparation of nanocrystalline nickel ferrite and aluminium-doped nickel ferrite nanoparticles with general formula NiAlxFe2−xO4 (x = 0–0.7) prepared by the sol–gel auto-combustion method. The structural (XRD and FTIR), morphological (SEM with EDAX, HRTEM with SAED) and optical (UV–Visible DRS and Luminescence spectroscopy) properties of the products were characterized. XRD studies revealed the formation of the single phase with a cubic spinel structure with an average crystallite size varies between 19 and 38 nm. The increase in aluminium content caused the variation in the lattice parameter (8.2782–8.3366 A). SEM images shows the morphology have nanocrystalline behavior with a spherical structure. FTIR represents the characteristic peaks of M–O vibrations in tetrahedral (~ 591 cm−1) and octahedral (~ 398 cm−1) sites. From the UV–Vis DRS spectra, the band gap is decreasing with increasing doping, estimated to be 2.03–1.90 eV. The luminescence spectrum displays violet, blue, green, and orange emission. The aluminium-doped nickel ferrite nanoparticles act as an exceptional photocatalyst for the degradation of rose bengal dye (99.8% in 150 min) with respect to bulk material (63% in 150 min) under visible light (300 W tungsten lamp) irradiation. Furthermore, these nanoparticles were acted against gram-negative bacteria stain (Salmonella typhi, Pseudomonas aeruginosa, and Escherichia coli).

Facile microwave-assisted green synthesis of NiO nanoparticles from Andrographis paniculata leaf extract and evaluation of their photocatalytic and anticancer activities

Abstract: In the present work, NiO nanoparticles based on Andrographis paniculata (leaf extract) were prepared through the microwave-assisted method. The obtained nanoparticles were analyzed using XRD, FTIR,...

Magnetohydrodynamic three-dimensional flow of nanofluids with slip and thermal radiation over a nonlinear stretching sheet: a numerical study

Abstract: A numerical simulation for mixed convective three-dimensional slip flow of water-based nanofluids with temperature jump boundary condition is presented. The flow is caused by nonlinear stretching surface. Conservation of energy equation involves the radiation heat flux term. Applied transverse magnetic effect of variable kind is also incorporated. Suitable nonlinear similarity transformations are used to reduce the governing equations into a set of self-similar equations. The subsequent equations are solved numerically by using shooting method. The solutions for the velocity and temperature distributions are computed for several values of flow pertinent parameters. Further, the numerical values for skin-friction coefficients and Nusselt number in respect of different nanoparticles are tabulated. A comparison between our numerical and already existing results has also been made. It is found that the velocity and thermal slip boundary condition showed a significant effect on momentum and thermal boundary layer thickness at the wall. The presence of nanoparticles stabilizes the thermal boundary layer growth.

Nonlinear radiated MHD flow of nanoliquids due to a rotating disk with irregular heat source and heat flux condition

Abstract: This research is made to visualize the nonlinear radiated flow of hydromagnetic nano-fluid induced due to rotation of the disk. The considered nano-fluid is a mixture of water and Ti6Al4V or AA7072 nano-particles. The various shapes of nanoparticles like lamina, column, sphere, tetrahedron and hexahedron are chosen in the analysis. The irregular heat source and nonlinear radiative terms are accounted in the law of energy. We used the heat flux condition instead of constant surface temperature condition. Heat flux condition is more relativistic and according to physical nature of the problem. The problem is made dimensionless with the help of suitable similarity constraints. The Runge-Kutta-Fehlberg scheme is adopted to find the numerical solutions of governing nonlinear ordinary differential systems. The solutions are plotted by considering the various values of emerging physical constraints. The effects of various shapes of nanoparticles are drawn and discussed.

Nonlinear convective heat and mass transfer of Oldroyd-B nanofluid over a stretching sheet in the presence of uniform heat source/sink

Abstract: The present study addresses the three-dimensional flow and nonlinear radiative heat transfer of an Oldroyd-B nanofluid flow over a stretching surface with the addition effects of uniform heat source/sink and convective boundary conditions. Suitable similarity transformations are employed to reduce the governing partial differential equations into coupled nonlinear ordinary differential equations. These nonlinear ordinary differential equations are then solved numerically by RKF-45 method. The effects of physical parameters on velocity, temperature and concentration profiles are investigated and discussed. The result reveals that the nonlinear radiation is more effective than that of linear radiation.

Screening and production of lipase from fungal organisms

Abstract: Lipases (triacylglycerol acylhydrolases, (E.C. 3.1.1.3)) are a class of enzymes endowed with an ability to catalyze the hydrolysis of triglycerides to glycerol and free fatty acids. These are industrially significant, particularly microbial lipases. Among several diverse sources, lipases from fungal origin are much embraced owing to their high stability. These lipases are directly screened majorly by the plate assay technique involving various preferred and specific substrates and indirectly by appropriately growing the strains in liquid medium followed by analysing the activity of the filtrates. Production of fungal lipase is majorly by using solid state and submerged fermentation processes with considerable variation in their operational conditions, that are influenced by physico-chemical factors and which plays a major role in the optimum lipase production. Further, the immobilized fungal cells have also been employed for lipase production using various support materials. Keeping in view of all these aspects, this review focuses on the screening, production and utility of lipases obtained from prominent fungal organisms.

Structural, optical and electrical properties of zinc incorporated copper oxide nanoparticles: doping effect of Zn

Abstract: The present paper demonstrates the effect of Zn ion doping on structural, electrical and optical properties of monoclinic CuO nanoparticles prepared via microwave combustion method. The crystal structure, optical and electrical properties of synthesized CuO and Zn-doped CuO samples were characterized by X-ray diffraction study, field emission scanning electron microscopy, energy-dispersive X-ray diffraction study, UV–Visible spectroscopy, transmission electron microscopy and photoconductivity technique. The XRD values show that the crystalline size of Zn-doped CuO nanoparticles was varied with Zn concentration and also it depends on the micro-strain and dislocation density of CuO lattice. FE-SEM and TEM images indicated that the synthesized samples are of the cube and rod-like structures in nature. The band gap of CuO nanoparticles has been calculated using Tauc’s plot and the result showed that the incorporation of Zn has decreased the bandgap of CuO. The I–V characterization study was performed to determine the electrical property of CuO and Zn-doped CuO films. From the results, it is observed that the photocurrent of CuO and Zn-doped CuO films is found to be greater in UV-light as compared to dark.

Cattaneo–Christov heat flux and non-uniform heat-source/sink impacts on radiative Oldroyd-B two-phase flow across a cone/wedge

Abstract: Impact of Cattaneo–Christov heat flux on radiative Oldroyd-B two-phase flow across a cone/wedge is addressed. RKF-45 method with shooting technique is used to obtain solution of the problem. The obtained results are presented through graphs and tables. We examined the results under non-linear variation of thermal radiation. Our simulations established that influence of physical parameter highly effective for cone when compare to wedge.

Epidemiology, drug resistance, and pathophysiology of Plasmodium vivax malaria.

Abstract: Malaria, caused by the protozoan parasites of the genus Plasmodium, is a major health problem in many countries of the world. Five parasite species namely, Plasmodium falciparum, P. vivax, P. malariae, P. ovale, and P. knowlesi, cause malaria in humans. Of these, P. falciparum and P. vivax are the most prevalent and account for the majority of the global malaria cases. In most areas of Africa, P. vivax infection is essentially absent because of the inherited lack of Duffy antigen receptor for chemokines on the surface of red blood cells that is involved in the parasite invasion of erythrocytes. Therefore, in Africa, most malaria infections are by P. falciparum and the highest burden of P. vivax infection is in Southeast Asia and South America. Plasmodium falciparum is the most virulent and as such, it is responsible for the majority of malarial mortality, particularly in Africa. Although, P. vivax infection has long been considered to be benign, recent studies have reported life-threatening consequences, including acute respiratory distress syndrome, cerebral malaria, multi-organ failure, dyserythropoiesis and anaemia. Despite exhibiting low parasite biomass in infected people due to parasite's specificity to infect only reticulocytes, P. vivax infection triggers higher inflammatory responses and exacerbated clinical symptoms than P. falciparum, such as fever and chills. Another characteristic feature of P. vivax infection, compared to P. falciparum infection, is persistence of the parasite as dormant liver-stage hypnozoites, causing recurrent episodes of malaria. This review article summarizes the published information on P. vivax epidemiology, drug resistance and pathophysiology.

Thermal Marangoni convection in two-phase flow of dusty Casson fluid

Abstract: This paper deals with the thermal Marangoni convection effects in magneto-Casson liquid flow through suspension of dust particles. The transpiration cooling aspect is accounted. The surface tension is assumed to be fluctuating linearly with temperature. The fluid and dust particle’s temperature of the interface is chosen as a quadratic function of interface arc length. The governing problem is modelled by conservation laws of mass, momentum and energy for fluid and dust particle phase. Stretching transformation technique is utilized to form ordinary differential equations from the partial differential equations. Later, the numerical solutions based on Runge-Kutta-Fehlberg method are established. The momentum and heat transport distributions are focused on the outcome of distinct governing parameters. The results of Nusselt number is also presented and discussed. It is established that the heat transfer rate is higher in the case of dusty non-Newtonian fluid than dusty Newtonian fluid. The rate of heat transfer can be enhanced by suspending dust particles in a base liquid.

Marangoni convection in Casson liquid flow due to an infinite disk with exponential space dependent heat source and cross-diffusion effects

Abstract: Present work aims to investigate the features of the exponential space dependent heat source (ESHS) and cross-diffusion effects in Marangoni convective heat mass transfer flow due to an infinite disk. Flow analysis is comprised with magnetohydrodynamics (MHD). The effects of Joule heating, viscous dissipation and solar radiation are also utilized. The thermal and solute field on the disk surface varies in a quadratic manner. The ordinary differential equations have been obtained by utilizing Von Karman transformations. The resulting problem under consideration is solved numerically via Runge-Kutta-Fehlberg based shooting scheme. The effects of involved pertinent flow parameters are explored by graphical illustrations. Results point out that the ESHS effect dominates thermal dependent heat source effect on thermal boundary layer growth. The concentration and temperature distributions and their associated layer thicknesses are enhanced by Marangoni effect.

Flow and heat transfer of dusty hyperbolic tangent fluid over a stretching sheet in the presence of thermal radiation and magnetic field

Abstract: This paper explores the impact of thermal radiation on boundary layer flow of dusty hyperbolic tangent fluid over a stretching sheet in the presence of magnetic field. The flow is generated by the action of two equal and opposite. A uniform magnetic field is imposed along the y-axis and the sheet being stretched with the velocity along the x-axis. The number density is assumed to be constant and volume fraction of dust particles is neglected. The fluid and dust particles motions are coupled only through drag and heat transfer between them. The method of solution involves similarity transformation which reduces the partial differential equations into a non-linear ordinary differential equation. These non-linear ordinary differential equations have been solved by applying Runge-Kutta-Fehlberg forth-fifth order method (RKF45 Method) with help of shooting technique. The velocity and temperature profile for each fluid and dust phase are aforethought to research the influence of assorted flow dominant parameters. The numerical values for skin friction coefficient and Nusselt number are maintained in Tables 3 and 4. The numerical results of a present investigation are compared with previous published results and located to be sensible agreement as shown in Tables 1 and 2. It is scrutinized that, the temperature profile and corresponding boundary layer thickness was depressed by uplifting the Prandtl number. Further, an increase in the thermal boundary layer thickness and decrease in momentum boundary layer thickness was observed for the increasing values of the magnetic parameter.

Scrutinization of thermal radiation, viscous dissipation and Joule heating effects on Marangoni convective two-phase flow of Casson fluid with fluid-particle suspension

Abstract: The impact of Marangoni convection on dusty Casson fluid boundary layer flow with Joule heating and viscous dissipation aspects is addressed. The surface tension is assumed to vary linearly with temperature. Physical aspects of magnetohydrodynamics and thermal radiation are also accounted. The governing problem is modelled under boundary layer approximations for fluid phase and dust particle phase and then Runge-Kutta-Fehlberg method based numeric solutions are established. The momentum and heat transport mechanisms are focused on the result of distinct governing parameters. The Nusselt number is also calculated. It is established that the rate of heat transfer can be enhanced by suspending dust particles in the base fluid. The temperature field of fluid phase and temperature of dust phase are quite reverse for thermal dust parameter. The radiative heat, viscous dissipation and Joule heating aspects are constructive for thermal fields of fluid and dust phases. The velocity of dusty Casson fluid dominates the velocity of dusty fluid while this trend is opposite in the case of temperature. Moreover qualitative behaviour of fluid phase and dust phase temperature/velocity are similar.

Enhancement of radiation on hydromagnetic Casson fluid flow towards a stretched cylinder with suspension of liquid-particles

Abstract: The presence of dust particles is involved in many engineering and industrial processes like transport of petroleum, emission of smoke from vehicles, piping of power plants, treatment of waste-water and corrosive particles in mining. Due to such importance of this phenomenon, we considered the Casson liquid flow past a stretching hollow cylinder with fluid-particle suspension and convective boundary condition aspects. Numerical solution is obtained via shooting techniques after the applying of similarity variables to the governing partial equations. Key parameters of problem are discussed through graphs. It is noticed that the clean fluid temperature is always higher values as compared to dust fluid and also presence of radiation enhanced the temperature at the surface.

Nonlinear Gravitational and Radiation Aspects in Nanoliquid with Exponential Space Dependent Heat Source and Variable Viscosity

Abstract: The nonlinear convective flow of kerosene-Alumina nanoliquid subjected to an exponential space dependent heat source and temperature dependent viscosity is investigated here. This study is focuses on augmentation of heat transport rate in liquid propellant rocket engine. The kerosene-Alumina nanoliquid is considered as the regenerative coolant. Aspects of radiation and viscous dissipation are also covered. Relevant nonlinear system is solved numerically via RK based shooting scheme. Diverse flow fields are computed and examined for distinct governing variables. We figured out that the nanoliquid’s temperature increased due to space dependent heat source and radiation aspects. The heat transfer rate is higher in case of changeable viscosity than constant viscosity.

Cross diffusion effect on MHD mixed convection flow of nonlinear radiative heat and mass transfer of Casson fluid over a vertical plate

Abstract: A study on magnetohydrodynamic mixed convection flow of Casson fluid over a vertical plate has been modelled in the presence of Cross diffusion effect and nonlinear thermal radiation. The governing partial differential equations are remodelled into ordinary differential equations by using similarity transformation. The accompanied differential equations are resolved numerically by using Runge–Kutta–Fehlberg forth-fifth order along with shooting method (RKF45 Method). The results of various physical parameters on velocity and temperature profiles are given diagrammatically. The numerical values of the local skin friction coefficient, local Nusselt number and local Sherwood number also are shown in a tabular form. It is found that, effect of Dufour and Soret parameter increases the temperature and concentration component correspondingly.

MHD Nanofluid Flow Past a Rotating Disk with Thermal Radiation in the Presence of Aluminum and Titanium Alloy Nanoparticles

Abstract: The effects of thermal and exponential space dependent heat sources (THS and ESHS) on magneto-nanoliquid flow across a rotating disk with uniform stretching rate along radial direction are scrutinized in this communication. H2O based nanoliquids containing aluminium (AA 7075) and titanium (Ti6Al4V) alloy nanoparticles are considered. The AA7075 is made up of 90% Al, 5-6% Zn, 2-3% Mg, 1-2% Cu with additives such as Fe, Mn and Si etc. The flow is driven due to rotating disk with uniform stretching of the disk. Impacts of Joule and viscous heating are also deployed. The multidegree ordinary differential equations are formed via Von Karman transformations. The obtained non-linear BVP is solved by Runge-Kutta-Fehlberg based shooting approach (RKFS). Graphical illustrations depict the impacts of influential parameters on flow fields. The skin friction and Nusselt number are also calculated. Results pointed out that the thermal boundary layer growth stabilizes due to the influence of ESHS aspect. Velocities of nanofluid are superior than that of nanoliquid. Furthermore, the thermal performance of base liquid is outstanding when we added titanium alloy nanoparticles in comparison with aluminium alloy nanoparticles.

Quadratic convective flow of radiated nano-Jeffrey liquid subject to multiple convective conditions and Cattaneo-Christov double diffusion

Abstract: A nonlinear flow of Jeffrey liquid with Cattaneo-Christov heat flux is investigated in the presence of nanoparticles. The features of thermophoretic and Brownian movement are retained. The effects of nonlinear radiation, magnetohydrodynamic (MHD), and convective conditions are accounted. The conversion of governing equations into ordinary differential equations is prepared via stretching transformations. The consequent equations are solved using the Runge-Kutta-Fehlberg (RKF) method. Impacts of physical constraints on the liquid velocity, the temperature, and the nanoparticle volume fraction are analyzed through graphical illustrations. It is established that the velocity of the liquid and its associated boundary layer width increase with the mixed convection parameter and the Deborah number.