Elemental analyses and determination of lead content in kohl (stone) by laser-induced breakdown spectroscopy

Elemental analyses of kohl (stone) samples collected from three different parts of the world were performed using laser-induced breakdown spectroscopy (LIBS). The analyses indicated that lead (Pb), copper (Cu), silver (Ag), iron (Fe), calcium (Ca), aluminum (Al), silicon (Si), and sodium (Na) were present in all the kohl samples. In addition to these elements, the sample from Madina, Kingdom of Saudi Arabia (KSA), contained the elements tin (Sn), zirconium (Zr), and antimony (Sb). The sample from Mount Toor, Egypt, also contained Sn. Also, quantitative analysis for lead was carried out by the standard addition method using the LIBS technique. The result showed the presence of 14.12 ± 0.28% by weight of Pb in the sample from Madina, which compares well with the measurement done using atomic absorption spectroscopy (AAS) (13.31 ± 0.46%). The standard addition method used three calibration curves drawn for three emission lines of the LIBS spectra of Pb. The limits of detection (LoD) for these calibration curves varied from 0.27% to 1.16% by weight. The lead contents of the samples from Mount Toor and the local market of Bangladesh were also measured by the AAS technique, and the results were 14.61 ± 0.48% and 8.98 ± 0.35% by weight, respectively. The reason for determining only the lead content in kohl, which may be used as an eye cosmetic, is the adverse effect that lead has on health.     

Thermal performance of a novel rooftop solar micro-concentrating collector

Concentrating solar thermal systems offer a promising method for large scale solar energy collection. Although concentrating collectors are generally thought of as large-scale stand-alone systems, there is a huge opportunity to use novel concentrating solar thermal systems for rooftop applications such as domestic hot water, industrial process heat and solar air conditioning for commercial, industrial and institutional buildings. This paper describes the thermal performance of a new low-cost solar thermal micro-concentrating collector (MCT), which uses linear Fresnel reflectors, and is designed to operate at temperatures up to 220 °C. The modules of this collector system are approximately 3 m long by 1 m wide and 0.3 m high. The objective of the study is to optimise the design to maximise the overall thermal efficiency. The absorber is contained in a sealed enclosure to minimise convective losses. The main heat losses are due to natural convection inside the enclosure and radiation heat transfer from the absorber tube. In this paper we present the results of a computational and experimental investigation of radiation and convection heat transfer in order to understand the heat loss mechanisms. A computational model for the prototype collector has been developed using ANSYS–CFX, a commercial computational fluid dynamics software package. The numerical results are compared to experimental measurements of the heat loss from the absorber, and flow visualisation within the cavity. This paper also presents new correlations for the Nusselt number as a function of Rayleigh number.     

Oscillator strengths and transition probabilities of O II

The abundance of singly ionized oxygen, O II, in planetary nebulae provides crucial diagnostic tests for the physical conditions present in these astrophysical environments. The abundance can be determined from the absorption lines formed by the radiative processes, such as the photo-excitations reported here. Radiative transitions are obtained from a total of 708 fine structure levels of O II with , and 1/2?J?17/2. For spectral analysis oscillator strengths, line strengths, and transition probabilities (A) are presented for 51,733 electric dipole fine structure radiative transitions. The calculations were carried out in the relativistic Breit-Pauli R-matrix approximation. The transitions have been identified spectroscopically using quantum defect analysis and other criteria. The calculated energies agree with the observed energies within 5% for most of the levels. However, some relatively large differences are noted, the largest difference being 13% for the level 2s²2p²(¹D)4p(²F^o)_7/2. Most of the A values and lifetimes agree with the existing measured and calculated values. The transitions should be applicable for diagnostics as well as spectral modeling in the ultraviolet and optical regions of astrophysical and laboratory plasmas.     

Numerical techniques for solving solidification and melting phase change problems

This article reviews several mathematical formulations including the corresponding boundary conditions for numerical predictions of solidification and melting. Emphasis is on techniques that are used in solving solid–liquid interface phenomena. The fixed grid enthalpy method is reviewed based on the solution techniques of conduction and convection related phase change problems. Variable grid methods are categorized and then analyzed based on their accuracy, computational efforts and convergence characteristics. The article concludes with some guidance for selecting the accurate solution techniques for solving solidification and melting problems.     

Sargassum swartzii extracts ameliorate memory functions by neurochemical modulation in a rat model

Food Science and Biotechnology - Recently, considerable attention has been paid to drug exploration from natural sources for treating memory loss, a major manifestation of various neurodegenerative...     

Characterisation of normal corn starch using asymmetrical flow field‐flow fractionation

The apparent average molar masses (M_w,app), apparent average radii of gyration (R_g,app), diffusion co‐efficients (D_T), and hydrodynamic radii (R_h) of normal corn (maize) starch and fractions were determined using asymmetrical flow field‐flow fractionation coupled with multi‐angle light scattering and refractive index detectors (AF4/MALS/RI). AM‐type (Fraction A) and AP‐type (Fraction B) were chemically separated from normal corn starch. Normal corn starch and Fractions (A–B) were dissolved in 1 M KSCN using a high pressure microwave vessel. The effect of varying cross flow rates at a fixed channel flow rate upon the M_w,app and R_g,app distributions of normal corn starch and Fractions (A–B) were investigated. The average M_w,app of normal corn starch, Fractions (A) and Fraction (B) were 41 × 10⁶, 1.4 × 10⁶ and 39 × 10⁶ g/mol, respectively, with R_g,app values of 129, 60 and 129 nm, respectively.     

Simulations of microfluidic droplet formation using the two-phase level set method

Microdroplet formation is an emerging area of research due to its wide-ranging applications within microfluidic based lab-on-a-chip devices. Our goal is to understand the dynamics of droplet formation in a microfluidic T-junction in order to optimize the operation of the microfluidic device. Understanding of this process forms the basis of many potential applications: synthesis of new materials, formulation of products in pharmaceutical, cosmetics and food industries. The two-phase level set method, which is ideally suited for tracking the interfaces between two immiscible fluids, has been used to perform numerical simulations of droplet formation in a T-junction. Numerical predictions compare well with experimental observations. The influence of parameters such as flow rate ratio, capillary number, viscosity ratio and the interfacial tension between the two immiscible fluids is known to affect the physical processes of droplet generation. In this study the effects of surface wettability, which can be controlled by altering the contact angle, are investigated systematically. As competitive wetting between liquids in a two-phase flow can give rise to erratic flow patterns, it is often desirable to minimize this phenomenon as it can lead to a disruption of the regular production of uniform droplets. The numerical simulations predicted that wettability effects on droplet length are more prominent when the viscosity ratio λ (the quotient of the viscosity of the dispersed phase with the viscosity of the continuous phase) is O(1), compared to the situation when λ is O(0.1). The droplet size becomes independent of contact angle in the superhydrophobic regime for all capillary numbers. At a given value of interfacial tension, the droplet length is greater when λ is O(1) compared to the case when λ is O(0.1). The increase in droplet length with interfacial tension, σ, is a function of with the coefficients of the regression curves depending on the viscosity ratio.     

Formulation development and optimization of alpha ketoglutarate nanoparticles for cyanide poisoning

The purpose of this research work was to formulate and evaluate alpha ketoglutarate nanoparticles as dry powder inhaler for treatment of cyanide poisoning. Non-polymeric particles were prepared by nano-precipitation technique using various stabilizers. Selection of co-solvent and stabilizer was a key to produce stabilized particles. A combination of lutrol F68 and PVA as a crystal growth inhibitor seems to be best in achieving minimum particle size of 110.2 nm. On the basis of preliminary trials a Box-Behnken statistical design was employed to study the effect of independent variables, drug concentration (X₁), stirring speed (X₂), stirring time (X₃), PVA concentration (X₄), poloxomer concentration (X₅) and volume of co-solvent (X₆) on average particle size. Particle size varied from 110 to 875 nm depending upon the significant terms. Optimized formulation was predicted at drug concentration (50 μg/ml), stirring speed (640 rpm), stirring time (1 min), PVA concentration (1%), poloxomer concentration (1.69%) and volume of co-solvent (30 ml) with 104.6% experimental validity. The nanosized particles were further characterized by X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared Spectroscopy (FT-IR) analysis. The results of particle characterization indicate that there was no physical disparity when compared with the commercial α-KG sample.     

Children's enjoyment and perception of computer use in the home and the school

This paper seeks to examine the nature and experiences of children's computer use in the home and school. Past research suggests a growing gap between computer use in the home and the school. This study was conducted to find out how children perceive and enjoy computer use in these two environments. Using a sample of year 3 and 5 pupils in three primary schools, qualitative and quantitative data were gathered. The results suggest that children make more use of the computer at home than at school. The most popular activity on the home computer which all children enjoyed was playing games. The most frequent activity at the school computer was word processing which pupils considered boring. Interesting gender differences showed that boys spent more time playing computer games whereas girls spent more time on the Internet emailing friends. The study concludes that schools should learn from what works at home and enable children to work on activities they find valuable, motivational and worthwhile.