Dosimetric evaluation of an indigenously developed 10 MeV industrial electron beam irradiator

The high dose rate electron beams are increasingly being used for radiation processing of various products worldwide. A comprehensive dosimetric evaluation of an in-house developed 10 MeV industrial electron beam irradiator was carried out in static as well as in dynamic mode of irradiations. Radiochromic B3 film and graphite calorimeter were used for dosimetric measurements. The dose rate from the electron beam was also calculated using the empirical relation prescribed in the ASTM report E2232-02. The measured electron beam profile indicates the dose rate variation within 8% in the irradiated product boxes. The most probable energy determined from the depth dose distribution in PMMA, Al and water was found in agreement with the intended energy of the electron beam. Measured dose rate using radiochromic film and graphite calorimeter were found in good agreement with each other and also found comparable with the theoretically estimated dose rates. Experimentally measured dose rates were considered for the trial irradiation of medical and industrial products. Dosimetric data obtained through this study confirms the suitability of the irradiator for routine radiation processing of various products.     

Microextraction-Colorimetric Determination of Quaternary Ammonium Compounds in Medicines and Disinfectants

Moscow University Chemistry Bulletin - We propose a method for the determination of quaternary ammonium compounds (QACs) in medicines and disinfectants, based on dispersive liquid–liquid...     

Factors affecting the registration and counting of alpha tracks in solid state nuclear track detectors

In view of the fact that the radon progeny contribute the highest to the natural radiation dose to general populations, large scale and long-term measurements of radon and its progeny in the houses have been receiving considerable attention. Solid State Nuclear Track Detector (SSNTD) based systems, being the best suited for large scale passive monitoring, have been widely used for the radon gas (using a cup closed with a semi-permeable membrane) and to a limited extent, for the measurement of radon progeny (using bare mode in conjunction with the cup). These have been employed for radon mapping and indoor radon epidemiological studies with good results. In this technique, alpha tracks recorded on SSNTD films are converted to radon/thoron concentrations using corresponding conversion factors obtained from calibration experiments carried out in controlled environments. The detector response to alpha particles depends mainly on the registration efficiency of the alpha tracks on the detector films and the subsequent counting efficiency. While the former depends on the exposure design, the latter depends on the protocols followed for developing and counting of the tracks. The paper discusses on parameters like etchant temperature, stirring of the etchant and duration of etching and their influence on the etching rates on LR-115 films. Concept of break down thickness of the SSNTD film in spark counting technique is discussed with experimental results. Error estimates on measurement results as a function of background tracks of the films are also discussed in the paper.      

Green's function method for aerosol penetration in channels under laminar flow conditions

A generalized method based on Green's function technique is developed to calculate the penetration fraction of particles by diffusion, formed from a given source in a gas under laminar flow, in cylindrical and rectangular channels. Both the initial value and the formation-in-flight types of problems are brought together in one formal procedure. The task of having to solve the convective-diffusion equation, for a given distribution of source density in the case of formation-in-flight problems, is altogether eliminated. The effect of a first-order reaction, like radioactive decay, is taken into account. Linear approximation for the shift in the eigenvalues due to the reaction term is given for small values of the dimensionless reaction rate constant. Finally, the solution available for an exponentially decreasing source in a cylindrical channel is found to be incorrect and the correct expression is derived using this method.     

Isosteviol and some of its derivatives as receptors and carriers of amino acid picrates

The ability of diterpenoid isosteviol 1 (ent-16-oxobeyeran-19-oic acid) and some of its derivatives with ester and amide groups to bind amino acid picrates in the course of their transport through a liquid chloroform membrane was observed for the first time. Isosteviol was very competitive with dibenzo-18-crown-6 and N,N′-bis(isostevioyl)-1,4-phenylenediamine 5 was even more effective in transportation of d,l-tryptophan through a liquid chloroform membrane.     

CFD-based simulation and experimental verification of 222Rn distribution in a walk-in type calibration chamber

A walk-in type ²²²Rn calibration chamber (~ 22 m³) is established at the Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, India which is being used by research groups working on ²²²Rn in India and other countries as well. In recent times, computational fluid dynamics (CFD) technique is opted as an alternative approach for the prediction of ²²²Rn concentration profile in the closed domain. CFD simulations were carried out to study the transient build-up and spatial behavior of ²²²Rn concentration in the calibration chamber. Measurements were performed using active ²²²Rn measuring devices and results of the CFD predictions and direct measurements were compared. A good agreement was observed between the simulated and experimental results with deviation between the two entities being ~ 3% in the case of transient build up and ~ 8% in the case of spatial distribution of ²²²Rn concentration.

     

Overconvergence Properties of Dirichlet Series

Potential Analysis - In this paper we use potential theoretic arguments to establish new results concerning the overconvergence of Dirichlet series. Let ${\sum }_{j=0}^{\infty } a_{j}e^{-\lambda...