Determination of gamma-emitting radionuclides in the inter-tidal sediments off Balochistan (Pakistan) Coast, Arabian Sea

Natural radionuclide contents of 226Ra, 228Ra and (40)K were studied for inter-tidal sediments collected from selected locations off the745 km long Balochistan Coast using HPGe detector based gamma-spectrometry system. The sampling zone extends from the beaches of Sonmiani (near Karachi metropolis) through Jiwani (close to the border of Iran). The natural radioactivity levels detected in various sediment samples range from 14.4 +/- 2.5 to 36.6 +/- 3.8 Bq kg(-1) for 226Ra, 9.8 +/- 1.2 to 35.2 +/- 2.0 Bq kg(-1) for (228)Ra and 144.6 +/- 9.4 to 610.5 +/- 23.9 Bq kg(-1) for (40)K. No artificial radionuclide was detected in any of the marine coastal sediment samples. 137Cs, (60)Co, 106Ru and 144Ce contents in sediment samples were below the limit of detection. The measured radioactivity levels are compared with those reported in the literature for coastal sediments in other parts of the world. The information presented in this paper will serve as the first ever local radioactivity database for the Balochistan/Makran Coastal belt of Pakistan. The presented data will also contribute to the IAEA's, Asia-Pacific Marine Radioactivity Database (ASPAMARD) and the Global Marine Radioactivity Database (GLOMARD).     

Structural, optical and photocatalytic properties of sol-gel synthesized mesoporous TiO2 film

TiO2 surfactant-templated nanostructured film was fabricated by supramolecular templating technique using TiCl4 and P-123 as raw material and surfactant, respectively. The film was produced by sol-gel dip coating procedure. Characterization of the product was carried out by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface areas, thermogravimetry (TG), and UV-vis absorption spectroscopy. Detailed characterization reveals that film is transparent and has a wormlike mesostructured with high surface area. It is about 2 microm thick and is composed of closely packed anatase particles. The estimated band gap value of TiO2 thin film in the present work is 3.69 eV which is about 0.3 eV larger than value reported in literature for anatase thin film. It could be due to quantum size effect arising from the small size of TiO2 nanocrystallite in this thin film. The photocatalytic activity of the prepared TiO2 film was evaluated by Crystalviolet dye degradation. The film has excellent photocatalytic efficiencies and more than 70% of dye was decolorized in 60 minutes.     

Corrosion of nickel-chromium alloys, stainless steel and niobium at supercritical water oxidation conditions

Results of immersion tests of UNS N06625 (alloy 625), UNS S31609 (alloy 316 L), Ni-20Cr alloy and Nb coupons exposed to oxygenated ammoniacal sulphate solution at supercritical water oxidation (SCWO) conditions are presented. The corrosion behavior of the alloy 316 L (UNS S31603) SCWO reactor tubing is also presented under the same conditions. Immersion coupons corroded at a rate not exceeding 40 mm yr⁻¹ while the reactor tube itself corroded at a rate of between 160-1500 mm yr⁻¹, depending on which length of the reactor is considered to have corroded. Morphological and chemical analysis of the oxides present on the coupon samples suggest that iron oxides, which had initially precipitated on the corroding alloy 316 tube surface, were removed by heat flux-driven fluid mechanical action and transported through the reactor where they deposited on the coupons. Niobium was resistant to corrosion at the tested conditions.     

Speckle reduction using orthogonal arrays in laser projectors

We propose using a two-level (-1 and +1 as variables) orthogonal array (OA) to generate a binary phase diffuser for speckle reduction in laser projection displays. Compared with the Hadamard matrix, the diffuser generated from OA is more flexible. The speckle contrast ratio (CR) when introducing the binary phase diffuser at an intermediate image plane within the projector is calculated, and the minimum speckle CR can be achieved by finite step change of the diffuser patterns. With Kronecker algebra, the two-dimensional diffuser can also be replaced by two one-dimensional diffusers with the same function, and it can be implemented into the laser projector electronically and easily.     

Theoretical Investigation for Exploring the Antioxidant Potential of Chlorogenic Acid: A Density Functional Theory Study

The main objective of this research was to conduct a theoretical investigation into the antioxidant properties of chlorogenic acid. Calculations based on the density functional theory were performed using the B3LYP exchange-correlation functional and the 6-311G standard basis set to determine the theoretical parameters, such as bond dissociation enthalpy and spin density. H atom abstraction from ?OH groups was the most representative reaction pathway chosen for this study. From these calculations, it was estimated that bond dissociation enthalpies of hydroxyl groups were in the order of 3’-OH > 4’-OH > 2-OH > 1-OH. Spin densities of O-atoms of free radicals formed (after the removal of H atoms) from the hydroxyl groups of aromatic rings were lower than that of hydroxyl groups of alicyclic rings. On the basis of the calculated results, H atom abstraction from ?OH groups of aromatic ring should be the main mechanism for the antioxidant potential of chlorogenic acid. Moreover, a comparison of bond dissociation enthalpy values for different phenolic acid antioxidants showed that the chlorogenic acid is a potent antioxidant. This theoretical investigation might be helpful for the future applications of chlorogenic acid in the field of the pharmacy and food industries.     

Synthesis,characterization and corrosion protective properties of boron-modified polyurethane from natural polyol

A novel attempt has been made to incorporate boron in the backbone of castor oil to develop boron-modified polyester (BCPE) and polyurethane (BPU). The overall reaction strategy involved “single pot multiple reactions” in minimum solvent achieving about 50% reduction in the use of volatile organic compounds (VOCs) during the synthetic procedure. Spectral (I.R., ¹H NMR and ¹³C NMR), physicochemical and thermal (TGA and DSC) analyses of BCPE and BPU were carried out by standard methods. The physico-mechanical and corrosion/chemical resistance performances (in various corrosive media) tests of BPU coatings were also conducted to evaluate their coating properties. These studies revealed that (i) the incorporation of boron has a significant influence on structural and physico-chemical aspects, thermal stability as well as on coating properties of BPUs, (ii) interestingly, BPUs showed very good performance in alkaline media (unaffected in 5 wt% NaOH for 50 h) as compared to their other previously reported oil-based counterparts, (iii) boron, here, acts both as a modifier and crosslinker and (iv) BPUs serve as novel and promising candidates for use as corrosion protective coating material, which can be safely employed up to 220 °C.     

Rapid synthesis of thermally stable hydroxyapaptite

We have optimized the wet precipitation synthesis of hydroxyapaptite to obtain thermally stable powder in the short time span of 3 min. Exposure of the reaction mixture to 1000 W microwave for 3 min furnished hydroxyapatite, which was thermally stable at temperatures up to 1200 °C. Powders were analyzed for phase purity using X-ray crystallography; chemical composition was studied using Fourier transform infrared spectroscopy while particle morphology was analyzed using scanning electron microscopy.     

Identification of a gamma-irradiated ingredient (garlic powder) in Korean barbeque sauce by thermoluminescence analysis

Thermoluminescence (TL) analysis was applied to identify gamma-irradiated garlic powder in Korean barbeque sauce before and after pasteurization (85 °C, 30 min), when blended in different ratios (1%, 3%, and 5%). The sauce sample with nonirradiated garlic powder gave a background glow curve. However, the sample blended with irradiated ingredient (1 and 10 kGy) showed typical TL glow curves at temperatures of 150 to 200 °C. The identification properties of sauce samples were more influenced by blending ratios than by irradiation doses, showing that 3% and 5% added samples produced glow curves at 150 to 250 °C. After pasteurization of the samples containing the irradiated ingredient, TL glow intensity decreased but did not change its shape or temperature range. As a result, the pasteurization of Barbeque sauces containing irradiated ingredients had reduced TL glow intensity, but the shape and temperature range of glow curve were still able to provide information required for confirming irradiation treatment. PRACTICAL APPLICATION: To monitor the irradiated food in international market, thermoluminescence (TL) analysis is considered most promising identification technique because of its sensitivity and long-term stability. In this study the applicability of TL analysis to detect an irradiated ingredient (garlic powder) added in low quantity to a food matrix (sauce) was investigated. The effect of processing (pasteurization) on TL results was also evaluated.