Studies on mechanical behavior of glass epoxy composites with induced defects and correlations with NDT characterization parameters

Degradation in mechanical properties (compression, flexural and ILS) of glass epoxy composite laminates with induced defects (simulating delaminations) was studied. The defects were characterized by using the A-scan ultrasonic pulse-echo technique. The two A-scan parameters, viz. the back wall echo amplitude and time of flight, were followed respectively, as functions of the defect size (diameter) and its location in the laminate thickness. The mechanical properties of laminates were evaluated destructively for different defect sizes and locations. An attempt has been made to express the mechanical properties in terms of the two NDT scan parameters characterizing the defects and empirical equations presente

Awareness On Light Pollution Among Teacher Educators

This article is intended to assess the awareness of light pollution among teacher educators.  The data were collected from Teacher educators who are working in teacher education institutions under Tamil Nadu Teacher Education University (TNTEU). The self-made multiple-choice Questionnaire was used to collect the data. Both inferential and descriptive statistics were used to analyse the data.  There are many interesting findings were derived. The present study created an insight and enlightened about the light pollution among teacher educator

Effect of temperature-dependent viscosity on entropy generation in transient viscoelastic polymeric fluid flow from an isothermal vertical plate

A numerical investigation of the viscosity variation effect upon entropy generation in time-dependent viscoelastic polymeric fluid flow and natural convection from a semi-infinite vertical plate is described. The Reiner-Rivlin second order differential model is utilized which can predict normal stress differences in dilute polymers. The conservation equations for heat, momentum and mass are normalized with appropriate transformations and the resulting unsteady nonlinear coupled partial differential equations are elucidated with the well-organized unconditionally stable implicit Crank-Nicolson finite difference method subject to suitable initial and boundary conditions. Average values of wall shear stress and Nusselt number, second-grade fluid flow variables conferred for distinct values of physical parameters. Numerical solutions are presented to examine the entropy generation and Bejan number along with their contours. The outcomes show that entropy generation parameter and Bejan number both increase with increasing values of group parameter and Grashof number. The present study finds applications in geothermal engineering, petroleum recovery, oil extraction and thermal insulation, etc

Toksikološka svojstva citrinina

Citrinin (CTN) is a nephrotoxic mycotoxin produced by several fungal strains belonging to the genera Penicillium, Aspergillus, and Monascus. It contaminates various commodities of plant origin, cereals in particular, and is usually found together with another nephrotoxic mycotoxin, ochratoxin A (OTA). These two mycotoxins are believed to be involved in the aetiology of endemic nephropathy. In addition to nephrotoxicity, CTN is also embryocidal and fetotoxic. The genotoxic properties of CTN have been demonstrated with the micronuleus test (MN), but not with single-cell gel electrophoresis. The mechanism of CTN toxicity is not fully understood, especially not whether CTN toxicity and genotoxicity are the consequence of oxidative stress or of increased permeability of mitochondrial membranes. CTN requires complex cellular biotransformation to exert mutagenicity. Compared with other mycotoxins, CTN contamination of food and feed is rather scarce. However, it is reasonable to believe that humans are much more frequently exposed to CTN than generally accepted, because it is produced by the same moulds as OTA, which is a common contaminant of human food all over the world. At present, there are no specifi c regulations either in Croatia or in the European Union concerning CTN in any kind of commodity.Citrinin (CTN) nefrotoksičan je mikotoksin koji proizvode različiti sojevi plijesni iz rodova Penicillium, Aspergillus i Monascus. CTN se može naći u različitim namirnicama biljnog podrijetla, osobito u žitaricama i obično se nalazi zajedno s drugim nefrotoksičnim mikotoksinom, okratoksinom A (OTA). Pretpostavlja se da je izloženost ovim mikotoksinima povezana s nastankom endemske nefropatije. Osim što je nefrotoksičan, CTN je još i embricidan i fetotoksičan. Na genotoksičnost citrinina upućuje pozitivan mikronukleusni test na različitim vrstama staničnih kultura, iako je kometski test negativan. Mutagenost CTN-a očituje se na različitim vrstama stanica samo ako se pridodaju stanični aktivatori kao npr. S9-mix. Mehanizam toksičnosti CTN-a nije potpuno razjašnjen pa još uvijek traje znanstvena rasprava je li njegova toksičnost i genotoksičnost posljedica oksidacijskog stresa ili povećane permeabilnosti mitohondrijskih membrana. U dostupnoj literaturi podaci o kontaminiranosti hrane i krmiva ovim mikotoksinom mnogo su rjeđi od onih za druge mikotoksine. Može se pretpostaviti da su ljudi često izloženi ovom mikotoksinu zato što ga proizvode iste plijesni koje proizvode i OTA, a one kontaminiraju hranu po cijelom svijetu. U Hrvatskoj i u zemljama Europske Unije ne postoje zakonske odredbe o dopuštenim granicama CTN-a u bilo kojoj vrsti hrane

Computational modeling of unsteady third-grade fluid flow over a vertical cylinder: A study of heat transfer visualization

The present paper aims to investigate the effect of Prandtl number for unsteady third-grade fluid flow over a uniformly heated vertical cylinder using Bejan’s heat function concept. The mathematical model of this problem is given by highly time-dependent non-linear coupled equations and are resolved by an efficient unconditionally stable implicit scheme. The time histories of average values of momentum and heat transport coefficients as well as the steady-state flow variables are displayed graphically for distinct values of non-dimensional control parameters arising in the system. As the non-dimensional parameter value gets amplified, the time taken for the fluid flow variables to attain the time-independent state is decreasing. The dimensionless heat function values are closely associated with an overall rate of heat transfer. Thermal energy transfer visualization implies that the heat function contours are compact in the neighborhood of the leading edge of the hot cylindrical wall. It is noticed that the deviations of flow-field variables from the hot wall for a non-Newtonian third-grade fluid flow are significant compared to the usual Newtonian fluid flow. Keywords: Third-grade fluid, Heat function, Boussinesq’s approximation, Vertical cylinder, Implicit method, Prandtl numbe

Numerical study of transient convective turbulent boundary layer flow along a vertical plate: analysis of kinetic energy and its dissipation rate

The present article numerically investigates the turbulent buoyancy-driven (natural convection) flow along a vertical plate with a low Reynolds turbulence two-equation k-ε model. The deployed turbulence model is appropriate for low Reynolds number (LRN) turbulent flow adjacent to a solid boundary, and the turbulence kinetic energy (TKE) and dissipation rate of TKE are estimated using the momentum equations and are solved simultaneously with the mean flow conservation equations. Two-dimensional time-dependent viscous incompressible turbulent flow is simulated. This flow domain is governed by a highly non-linear group of partial differential equations, namely the time-averaged continuity, momentum, and energy, and also the flow property í µí¼ í µí±¡ is determined through TKE, and dissipation rate of TKE equations. Since these equations are not solvable using analytical methods, an implicit second order finite difference method is employed to solve the governing turbulent flow equations numerically. The simulated time-averaged velocity, temperature, TKE, and dissipation rate of TKE profiles along with friction factor and heat transfer rate are computed for different values of turbulent Reynolds (í µí±í µí±) and Prandtl (í µí±í µí±) numbers. Average velocity, temperature, turbulence energy, and dissipation rate under both transient and steady state conditions are decreased with increment in í µí±í µí±. There is a decrement in average transient velocity an

Green approach for the conversion of olefins into vic-halohydrins using N-halosuccinimides in ionic liquids

Alkenes undergo smooth bromo- and iodohydroxylation with N-bromo- and N-iodosuccinimides/water, respectively, using the air and moisture stable ionic liquid [bmim]BF4 as a novel recyclable reaction medium in high to quantitative yields. N-Halosuccinimides show enhanced reactivity in ionic liquids thereby reducing the reaction times and improving the yields considerably

Facile One-Step Route for the Development of in Situ Cocatalyst-Modified Ti³⁺ Self-Doped TiO₂ for Improved Visible-Light Photocatalytic Activity

Development of visible-light-driven photocatalysts by employing a relatively simple, efficient, and cost-effective one-step process is essential for commercial applications. Herein, we report for the first time the synthesis of in situ Cu-ion modified Ti³⁺ self-doped rutile TiO₂ by such a facile one-step solution precursor plasma spray (SPPS) process using a water-soluble titanium precursor. In the SPPS process, Ti³⁺ self-doping on Ti⁴⁺ of rutile TiO₂ is found to take place because of electron transfer from the created oxygen vacancies to Ti⁴⁺-ions. In situ Cu modification of the above Ti³⁺ self-doped rutile TiO₂ by additionally introducing a Cu solution into plasma plume is also demonstrated. While the Ti³⁺ self-doping induces broad absorption in the visible-light region, the addition of Cu ion leads to even broader absorption in the visible region owing to resulting synergistic properties. The above materials were evaluated for various self-cleaning photocatalytic applications under visible-light illumination. Cu-ion modified Ti³⁺ self-doped rutile TiO₂ is noted to exhibit a remarkably enhanced visible-light activity in comparison with Ti³⁺ self-doped rutile TiO₂, with the latter itself outperforming commercial TiO₂ photocatalysts, thereby suggesting the suitability of the material for indoor applications. The broad visible-light absorption by Ti³⁺ self-doping, the holes with strong oxidation power generated in the valence band, and electrons in Ti³⁺ isolated states that are effectively separated into the high reductive sites of Cu ions upon visible-light irradiation, accounts for improved photocatalytic activity. Moreover, the synthesis process (SPPS) provides a valuable alternative to orthodox multistep processes for the preparation of such visible-light-driven photocatalysts