Characterization and quantification of engineered nanoparticles in food by epithermal instrumental neutron activation analysis and electron microscopy

Engineered nanoparticles (NPs) have increasingly been used in various areas including agriculture and food packaging, which may potentially cause contamination in food products. In this study, a combination of analytical techniques was used to detect, characterize, and quantify engineered NPs (cerium (IV) oxide (CeO₂), silica (SiO₂) NPs, and their mixture) in food matrices. A series of concentrations of CeO₂, SiO₂, and their mixtures from 0 to 0.75 wt% were mixed in soybean powders. The presence of engineered NPs was investigated using transmission electron microscopy and scanning electron microscopy coupled with energy dispersive spectroscopy. The average size of CeO₂ and SiO₂ was 28.5 and 30.5 nm in diameter, respectively. CeO₂ NPs were irregular octahedral and cubic in shape, while SiO₂ NPs were spherical. The concentration of NPs in soybean powders was analyzed by epithermal instrumental neutron activation analysis (EINAA). Calibration curves were plotted for quantification of NPs in soybean powders (R ² = 0.996 and 0.994 for CeO₂, SiO₂ NPs in soybean powders, respectively; R ² = 0.995 and 0.997 for CeO₂ and SiO₂ NP in a mixture in soybean powders, respectively). The study of the detection limit (DL) demonstrates that at 99 % confidence interval, EINAA can detect both NPs at 0.1 wt% in soybean powders. Satisfactory recoveries were obtained for samples with a concentration at and higher than the DL (86.2–104.7 % for CeO₂ NPs and 85.7–95.2 % for SiO₂ NPs; 87.5–101.3 and 85.6–93.5 % for CeO₂ and SiO₂ NPs in a mixture in soybean powders, respectively).     

Nutritional constituents,phytochemical profiles, <Emphasis Type="Italic">in vitro</Emphasis> antioxidant and antimicrobial properties,and gas chromatography–mass spectrometry analysis of various solvent extracts from grape seeds (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L.)

The present study revealed that the nutritive value of grape seeds (Vitis vinifera L.) was 383.55±0.13 Kcal/100 g, with magnesium as the most abundant mineral element (70.44±0.88 mg/L). The maximum phenolic (392.58±1.70mg of GAE/g), flavonoid (256.16±1.60 mg of QE/g), and tannin (30.95±0.17mg of CE/g) contents were also found in the ethanol, dichloromethane, and hexane extracts, respectively. The major phytochemical compounds in the ethyl acetate extract were identified via gas chromatography–mass spectrometry (GC–MS) analysis. The ethanol extract has the highest antioxidant activity (IC₅₀=140±1.20 μg/mL for DPPH, 145.28±0.45mg α-tocopherol/g for total antioxidant capacity, and EC₅₀=80±1.41 μg/mL for ferric-reducing power assays). For β-carotene test, the highest antioxidant activity was obtained in the hexane extract. A satisfactory antimicrobial activity was found against a panel of microorganisms with the ethyl acetate extract as the best antimicrobial agent. Additionally, it was found that the bactericidal concentration required for the grape seed extract to kill Listeria monocytogenes should be less than 12.50 mg/mL (minimum inhibitory concentration=4).     

Iron(III) Chelates of substituted 8-hydroxy quinoline-7-sulfonic acids some physico chemical properties and analytical applications

Iron(III) forms in acidic aqueous medium green coloured complexes with 8-hydroxy quinoline-7-sulfonic acid (RI), 5-chloro-8-hydroxy quinoline-7-sulfonic acid (RII), 5-bromo-8-hydroxy quinoline-7-sulfonic acid (RIII) and 5-iodo-8-hydroxy quinoline-7-sulfonic acid (RIV). The composition of the complexes was studied by three different methods spectrophotometrically and the complexes were found to have the general formulae Fe(III)- R (where R stands for the ligand). The stability constants of the complexes, the free energy of formation, entropy and enthalpy changes and some analytical applications have been reported.     

Uranium(VI)-Methylthymol Blue (penta sodium salt) chelate – A spectrophotometric study

Spectrophotometric study has been made with a view to investigate the composition and stability of the chelate formed between uranium(VI) and penta sodium salt of Methylthymol Blue (MTB). The composition of the red coloured chelate (λ_max510 nm) as established by two different methods, comes out to 1:1 (metal:chelating agent). The chelate is stable between pH 6.2 and 6.9. The average value of log K at 30° (pH 6.7 ± 0.1; μ = 0.1 M) is 5.6 ± 0.2 and ΔG° at the same temperature is −7.7 ± 0.2 kcal/mole.     

Dual-threshold sequential detection code synchronization for anoptical CDMA network in the presence of multi-user interference

The paper examines the acquisition performance of a synchronization system for an optical fiber-based code-division multiple-access (CDMA) network that employs a dual-threshold sequential detector. The noncoherent optical CDMA network operates asynchronously and optical orthogonal codes (OOCs) are used for the spreading sequences. The performance measure of the synchronizer, the mean acquisition time, is derived via the Markov flow-graph method and Monte Carlo simulations are used to obtain the statistical parameters of the synchronizer when used within the system. The model takes into account the number of active users, the multi-user interference (MUI), the receiver noise and the coupler losses within the network. The results show that by adjusting both the acceptance and rejection thresholds of the sequential detector, the mean acquisition time ran be optimized. The degradation in the synchronizer performance, when the number of active users is changed from the number the synchronizer is designed for, is also assessed     

Experimental evaluation of the wind convection heat transfer on the glass cover of the single-slope solar still

Accurate evaluation of the wind convection heat transfer coefficient (h_w) for solar-based systems is essential, especially for solar desalination systems. Thermal behavior and productivity of solar stills are highly affected by the external heat loss through the glass cover. This paper describes a new experimental approach to estimate the h_w on the glass cover of the conventional single-slope solar distiller (CSS). Indoor experiments have been conducted under steady-state conditions for a wind speed between 0 and 3 m/s. The h_w has been evaluated through an energy balance performed on the distiller's glass cover. The results showed that increasing the wind speed increases the hw (from 5.64 to 31.57 W/m² K) and enhances the distillation rate (from 5.28 to 7.61 mL/min). A new relationship for the h_w was proposed for the CSS and compared with the experimental data available in the literature. The comparison shows that the obtained results are close to the data from solar systems, with a deviation ranging from 27.4% to 37%. However, a significant deviation was obtained with earlier models derived from flat plates (from 29.5% to 59%).     

TEOS-based PECVD of silicon dioxide for VLSI applications

Silicon dioxide films deposited from tetraethylorthosilicate (TEOS) using plasma-enhanced chemical vapour deposition (PECVD) are reviewed. The effect of the presence of oxygen on the film deposition rate and mechanism and the physical properties of the films, particularly the step coverage properties (conformality), are discussed in detail. Structural characterisation of the films has been carried out via etch rate measurements, infrared transmission spectroscopy, X-ray photoelectron spectroscopy (XPS) and Auger and secondary ion mass spectroscopy (SIMS) analysis. Electrical properties, i.e. resistivity, breakdown strength, fixed oxide charge density, interface state density and trapping behaviour, have been evaluated using metal-oxide-semiconductor (MOS) structures fabricated using the deposited oxides. Films deposited by microwave plasma-enhanced decomposition of TEOS in the presence of oxygen have been found to be comparable with standard silane-based low-pressure chemical vapour deposition (LPCVD) and PECVD oxides. It has been shown that films deposited on thin native oxides grown by either in situ plasma oxidation or low-temperature thermal oxidation exhibit excellent electrical properties.     

Bit error rate for rectangular QAM with arbitrary constellation mapping in Nakagami‐m channels

We present closed‐form expressions for the bit error rate (BER) of rectangular quadrature amplitude modulation (QAM) in Nakagami‐m fading channels. The presented formulas, which are valid for arbitrary bits‐to‐symbols mapping, thus may be used when non‐Gray mapping is employed, are particularly useful in the low signal‐to‐noise ratio (SNR) range and/or for small values of the parameter m. The advantage of the proposed expressions over the known bounding techniques is illustrated through numerical simulations. Copyright © 2006 John Wiley & Sons, Ltd.     

Current status of renewable energy in Nepal: Opportunities and challenges

Energy is indispensible in modern society and is one of the most important components of socio-economic development. Nepal is one of the least developed countries with more than 80% of its population residing in rural communities. Per capita energy usage – often viewed as a key index of the development – in the country is far less than the global average per capita energy usage. The energy sector is dominated by the traditional energy sources such as fuel woods, crop residues and animal dung mainly for domestic usage contributing to about 86% of the national energy consumption. Currently 40% of the population has access to electricity, and the rural electrification accounts for only 29%. The majority of rural populations are meeting their energy needs by burning biomass in traditional stoves which has several environmental and public health issues. Nearly all fossil-derived fuels consumed in the country are imported in a refined form, and the perpetual increase in petroleum imports has adversely impacted the existing fragile economy of the country. Despite a huge potential in harnessing various renewable energy resources such as hydropower, solar power, wind energy and biofuels/bioenergy, these resources have not been sustainably captured due to geographical, technical, political and economical reasons. This paper presents a brief account of Nepal's renewable energy resources and the current status of various renewable energy technologies (RETs) such as micro-hydro, solar power, wind energy, biofuel/bioenergy, improved cook stoves, and improved water mill. It also highlights the opportunities and barriers for the development of RETs. Finally this paper presents some recommendations for the promotion, development and implementation of RETs in the country.     

Influence of functionalized reduced graphene oxide and compatibilizer on mechanical,thermal and morphological properties of polypropylene/polybutene-1 (PP/PB-1) blends

Polypropylene/Polybutene-1 (PP/PB-1) blends and nanocomposites containing pristine partially reduced graphene oxide (rGO) and chemically functionalized rGO (FrGO) with silane, and silane grafted with 1,12-dodecanediamine and 1,12-dodecanediol were studied. The effects of the chemical treatments on structure and thermal stability of rGO were first thoroughly investigated. Attenuated total reflectance Fourier infrared (ATR-FTIR) spectroscopy analyses of FrGO evidenced the existence of functional groups on rGO after each chemical treatment, while X-ray diffraction (XRD) results confirmed the effectiveness of the interlayer grafting process through shifting of the basal spacings as witnessed by increased d₀₀₂ values. Furthermore, thermogravimetric analysis (TGA) revealed that the functionalization of rGO resulted in improved thermal stability of rGO demonstrated by its increased thermal degradation temperature. The PP/PB-1 blends and their rGO and FrGO based nanocomposites were prepared by melt blending masterbatch process in the presence of an acrylic acid modified polypropylene compatibilizer (PP-g-AA). Mechanical testing showed that Young’s modulus and tensile strength of the PP/PB-1 blends significantly improved after co-addition of FrGO and PP-g-AA to form the nanocomposites, but it also endowed a drastic decrease in their elongation at break and especially in their impact strength. XRD analyses attested the successful formation of intercalated nanocomposites, and scanning electron microscopy (SEM) examinations disclosed a two-phase morphology consisting of PB-1 dispersed droplets in the PP matrix. SEM also indicated that the incorporation of PP-g-AA into the blends and the nanocomposites contributed to enhanced adhesion and dispersion of PB-1 phase and FrGO nanoparticles within the polymer matrix.