Genetic risks to man from exposure to long-lived radionuclides

Ionizing radiation, irrespective of whether it is received from external sources or from internally-deposited radionuclides, is capable of causing genetic damage that will be transmitted from one generation to the next. Since strictly relevant human data is limited at present, there is no alternative to the use of data collected in experimental mammals for estimating genetic risks associated with the exposure of human populations to ionizing radiation.Animal studies reveal that plutonium reaching the testes and concentrates in the interstitial tissue but is later aggregated by macrophages, apparently leading to a reduction in effectiveness. For protracted alpha irradiation from testicular plutonium in the mouse, the RBE (relative biological effectiveness) for genetic effects of concern may be in a range of between 10 and 20, relative to chronic gamma irradiation. In female mice, plutonium appears to be much less effective although the data is very limited.Studies with beta emitters provide reasonable grounds for believing that in the case of chronic exposures to tritium, the RBE value may be about 2, whereas for others such as carbon-14, it may not be significantly different from unity.These and other results support the view that for plutonium alpha rays, the genetic risks following exposure of human males may be 10–20 times that estimated for chronic, low level, low LET irradiation, per unit absorbed testicular dose; for tritium exposures, the risks may be higher by a factor of 2, (again, relative to chronic gamma ray exposures) while for carbon-14, the risks are the same as that for chronic gamma irradiation. For estimating genetic risks following exposure of human females to radionuclides, in the absence of adequate data, it would be prudent to assume that the risks will be similar to those for irradiation of males.     

Enhanced ethanol sensing properties of WO3 modified TiO2 nanorods

Pristine and WO₃ decorated TiO₂ nanorods (NRs) were synthesised to investigate n-n-type heterojunction gas sensing properties. TiO₂ NRs were fabricated via hydrothermal method on fluorine-doped tin oxide coated glass (FTO) substrates. Then, tungsten was sputtered on the TiO₂ NRs and thermally oxidised to obtain WO₃ nanoparticles. The heterostructure was characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. Fabricated sensor devices were exposed to VOCs such as toluene, xylene, acetone and ethanol, and humidity at different operation temperatures. Experimental results demonstrated that the heterostructure has better sensor response toward ethanol at 200 °C. Enhanced sensing properties are attributed to the heterojunction formation by decorating TiO₂ NRs with WO₃.     

Flowerlike hybrid horseradish peroxidase nanobiocatalyst for the polymerization of guaiacol

In this study, the catalytic activity and stability of flowerlike hybrid horseradish peroxidase (HRP) nanobiocatalyst (HRP-Cu ²⁺ ) obtained from Cu ²⁺ ions and HRP enzyme in the polymerization reaction of guaiacol were analyzed. We demonstrated that HRP-Cu ²⁺ and hydrogen peroxide (H ₂ O ₂ ) initiator showed significantly increased catalytic activity and stability on the polymerization of guaiacol compared to that of free HRP enzyme. Poly(guaiacol) was observed with quite high yields (88%) and molecular weights (38,000 g/mol) under pH 7.4 phosphate-buffered saline (PBS) conditions at 60 °C with 5 weight% of HRP-Cu ²⁺ loading. HRP-Cu ²⁺ also shows very high thermal stability and works even at 70 °C reaction temperature; free HRP enzyme denatures at that temperature. Furthermore, HRP-Cu ²⁺ provided considerable repeated use and showed some degree of catalytic activity, even after the fourth recycle, in the polymerization of guaiacol.     

Chemical composition,antimicrobial, and lipase enzyme activity of essential oil and solvent extracts from Serapias orientalis subsp. orientalis

The volatile components of essential oil (EO), SPME, and SPME of solvent extracts ( n -hexane, methanol, and water) obtained from fresh Serapias orientalis subsp. orientalis ( Soo ) were analyzed by GC-FID/MS. EO of Soo gave 11 compounds in the percentage of 99.97%; capronaldehyde (37.01%), 2-( E )-hexenal (23.19%), and n -nonanal (19.05%) were found to be major constituents. SPME GC-FID/MS analyses of fresh plant and solvent extracts of Soo revealed 7, 12, 7, and 4 compounds within the range of 99.7% to 99.9%. Limonene (76.5%, 41.7%, and 61.3%) was the major compound in SPMEs of the n -hexane and methanol extracts. α -Methoxy- p -cresol (52.9%) was the main component in its water extract. The antimicrobial activity of EO and the solvent extracts of Soo were screened against 9microorganisms. EO showed the best activity against Mycobacterium smegmatis , with 79.5 µg/mL MIC value. The n -hexane, methanol, and water extracts were the most active against the Staphylococcus aureus within the range of 81.25–125.0 µg/mL (MIC). IC ₅₀ values for the lipase enzyme inhibitory activity of EO and solvent extracts ( n -hexane, methanol, and water) were determined to be 59.87 µg/mL, 64.03 µg/mL, 101.91 µg/mL, and 121.24 µg/mL, respectively.     

Thermal cycling,DLTS, and PEC studies on LEC gallium arsenide

This paper discusses the growth of gallium arsenide single crystals using the LEC technique. The Semi-insulating gallium arsenide was studied. The defect investigations were made by DLTS and etching studies. The variation of deep level concentration along the wafer was estimated using DLTS. The fabrication and efficiency of the PEC Solar cells are also reported.     

Enhancement of thermopower in the highT c superconductor YBa2Cu3O7 and related compounds

The absolute thermopower of single phase YBa₂Cu₃O₇ and Y_0.8Er_0.2Ba₂Cu₃O₇ has been measured in the range 250 K to the superconducting transition temperature. It is found that these compounds show a large enhancement of thermopower in the range 150 K down toT _c. This enhancement shows a steep exponential drop as the temperature increases from the transition temperature. The temperature variation of the enhancement is too steep to be accounted for by electron-phonon or electron-local structural excitation mechanisms.     

A switched controller for an underactuated underwater vehicle

We present a switched control law for stabilizing an underactuated underwater vehicle (UUV) moving in a horizontal plane in a neutrally buoyant condition. The control law consists of a sequential series of control actions, each of which achieves a certain objective, finally resulting in the system being moved to the origin. Finite-time controllers are employed at each stage to achieve the desired objective. Simulation results are presented to validate the control law.     

Dispersion and stability analyses of the linearized two‐dimensional shallow water equations in boundary‐fitted co‐ordinates

In the present investigation, a Fourier analysis is used to study the phase and group speeds of a linearized, two‐dimensional shallow water equations, in a non‐orthogonal boundary‐fitted co‐ordinate system. The phase and group speeds for the spatially discretized equations, using the second‐order scheme in an Arakawa C grid, are calculated for grids with varying degrees of non‐orthogonality and compared with those obtained from the continuous case. The spatially discrete system is seen to be slightly dispersive, with the degree of dispersivity increasing with an decrease in the grid non‐orthogonality angle or decrease in grid resolution and this is in agreement with the conclusions reached by Sankaranarayanan and Spaulding (J. Comput. Phys., 2003; 184 : 299–320). The stability condition for the non‐orthogonal case is satisfied even when the grid non‐orthogonality angle, is as low as 30° for the Crank Nicolson and three‐time level schemes. A two‐dimensional wave deformation analysis, based on complex propagation factor developed by Leendertse (Report RM‐5294‐PR, The Rand Corp., Santa Monica, CA, 1967), is used to estimate the amplitude and phase errors of the two‐time level Crank–Nicolson scheme. There is no dissipation in the amplitude of the solution. However, the phase error is found to increase, as the grid angle decreases for a constant Courant number, and increases as Courant number increases. Copyright © 2003 John Wiley & Sons, Ltd.     

Development of an HPLC method for determination of pentachloronitrobenzene, hexachlorobenzene and their possible metabolites

Background

Pentachloronitrobenzene (PCNB) and hexachlorobenzene (HCB) are highly toxic and widespread in every environmental compartment. Some of metabolic products such as amino/nitro containing chlorinated aromatic compounds can be determined by gas chromatography coupled with electron capture detector (GC-ECD). However, it is difficult to identify some of chlorophenolic and chloroquinolic intermediates produced from PCNB and HCB by the above mentioned technique. Therefore, for analysis of these compounds and their metabolites, we have developed a high performance liquid chromatography (HPLC) based method.

Results

The extraction of PCNB and HCB from soil and minimal salt medium was carried out with ethyl acetate and hexane respectively with good recoveries (98% for PCNB and 97% for HCB). The validation of the proposed extraction and HPLC method was done by analysis of PCNB and HCB biodegradation and their metabolites identification from anaerobic enriched soil samples.

Conclusion

A rapid, sensitive and simple HPLC based analytical method was developed for the analysis of PCNB, HCB and their possible intermediates.