[en] Short communication

[en] The presence of residual thyroid tissue even after total or near total thyroidectomy for Differentiated Thyroid Carcinoma (DTCa) is relatively common as observed on post-surgical ¹³¹I scan. Parallel with many controversial debates to ablate the residual thyroid tissue by ¹³¹I therapy is being widely practiced for the last five decades. The purpose of this to evaluate the effectiveness of the I^13I therapy with post-surgical remnants in DTCa patients. (author) 6 tabs., 20 refs

[en] In this research, electrokinetic process was applied for the decontamination of cesium contaminated soil. As a result, about 4.0 times cesium removal was achieved by applying a DC electric field of 80 V/m to comparing zero electric field in treatment for 30 days. Therefore, the electrokinetic process has a possibility to decontamination of cesium contaminated soil. (author)

[en] Studies were made to estimate the beta-particle dose rates to micro-organisms of various sizes in soil. The small insects and organisms living in soil are constantly exposed to beta-radiation arising from naturally occuring radionuclides in soil as in this case no overlying tissue shields them. The technique of measuring beta-particle dose rate consisted of using of a thin plastic scintillator to measure the pulse height distribution as the beta particle traverses the scintillator. The integrated response was determined by the number and size of the photomultiplier pulses. From the data of soil analyses it was estimated that typically about 29% of the beta particles emitted per gm. of soil were contributed by the U/Ra series, 21% by the Th series and about 50% by potassium. By combining the individual spectra of these three radionuclides in the proportion found in a typical soil, a resultant spectrum was computed representing the energy distribution of the beta particles. The dose rate received by micro-organisms of different shape and size in soil was derived from the equilibrium dose rates combined with a 'Geometrical Factor' of the organisms. For small organisms, the dose rates did not vary between the spherical and cylindrical types, but in the case of larger organisms, the dose rates were found to be greater for the spherical types of the same diameter. (auth.)

[en] Dielectric properties of rubber wood were studied at different microwave frequencies, structural directions, and moisture contents using an open-ended coaxial probe. Frequencies used for this study were 1.00, 2.45, 6.0, 8.0, 10.0, 14.0, and 17.0 GHz; and the measurements were carried out at a room temperature of 22-24°C. The dielectric constant and dielectric loss factor were found to increase continuously as the moisture content increased. A sharp rise in the dielectric constant and dielectric loss factor was obtained at high moisture content, and the trends became concave upward. As the frequency increased, the dielectric constant decreased, whereas the dielectric loss factor increased. The dielectric loss factor remained almost constant above the frequency of 6 GHz for all structural directions. Fourth-order polynomial equations were found suitable for the best fit curve. Dielectric constant and dielectric loss factor of oven-dry wood were higher in the longitudinal direction than in the radial and tangential directions. With respect to frequency, the dielectric loss factor exhibited a peak value around 10 GHz. The dielectric anisotropy of wood may be attributed to the microscopic and macroscopic molecular structures as well as to chemical constituents of wood

[en] In this study toxicity and tolerance of Samanea saman (Jacq.) Merr. was investigated for Pb, Cd, Cu and Zn under lab conditions. Germination rate of S. saman showed that increased concentration of different metals from 25 to 100 ppm, significantly (p<0.05) reduced germination which was more prominent for Pb treatments. Seedling growth variables i.e. root and shoot length, seedling size, root/shoot ratio, seedling fresh and dry weights also declined significantly (p<0.05). Seedlings growth of S. saman gradually reduced with increasing in concentrations of metals especially Pb and Cd compared to Cu and Zn. The inhibitory effects of metals had the following order Pb>Cd>Cu>Zn of sequence at different concentrations. Tolerance indices determined for different metal illustrated that increasing concentrations of metals reduced the tolerance of S. saman but this reduction was more prominent for Pb and Cd as compared to Cu and Zn treatments. (author)

[en] The impact of auto-vehicular pollution on the qualitative and quantitative characteristics of Azadirachta indica A. Juss. growing along different polluted roads of Karachi was evaluated. Reductions in leaves parameters such as leaf area, leaf fresh and dry weight of A. indica were observed at University Campus, University Road, Board Office Road, Shaheed-e-Millat Road and Shahrah-e-Faisal during different seasons of the years from, 2008-2009. Some visual observations as leaf color, fruit and seed production were also recorded periodically, which showed variation at different sites. Results indicated that A. indica at control site were growing as fast as they were given the favorable resources such as bio-climatic factors which include heat index, chill, humidity, temperature and wind speed naturally available to them but road-side pollution stressed the growth. Climatic conditions were comparatively different on the city roads as compared to the University Campus. The automobiles density has significantly (p<0.05) reduced the leaf area of A. indica at Shahrah-e-Faisal in summer season (July, 2008). The soil of the studied area showed a high percentage of CaCO/sub 3/, slightly alkaline pH, electrical conductivity (E.C.), total dissolved salts (T.D.S.) in city roads as compared to University Campus soil. These findings demonstrated that traffic density and harsh bio-climatic conditions showed poor appearance and reduction in the qualitative characters and biomass of A. indica. (author)

[en] A quantitative phyto sociological survey was conducted around the industrial areas of Sindh Industrial Trading Estate (S.I.T.E.) of Karachi. The herbaceous, shrubs vegetation was predominantly disturbed in nature. Fifteen plant communities based on Importance Value Index (IVI) of species were recognized. Eighty plant species were recorded in industrial areas. Abutilon fruticosum L., attained the highest importance value index (823.25) followed by Prosopis juliflora DC. (662.62), Corchorus trilocularis L. (467.20), Aerva javanica Burm.f. (419.97), Amaranthus viridis L. (397.65) and Senna holosericea L. (387.22), respectively. P. juliflora and A. fruticosum showed leading first dominant in five and four stands, respectively. Whereas, A. javanica, A. viridis, S. holosericea, Launaea nudicaulis L., Crochorus depressus L. and Salvadora L., attained the presence class III. Zygophyllum simplex L., Suaeda fruticosa L., Convolvulus glomeratus Choisky, Cressa cretica L., Cleome viscosa L., Calotropis procera Willd, Blepharis sindica T. Anderson, Rhynchosia pulverulenta L., Abutilon pakistanicum Jafri and Ali, Chenopodium album L., Capparis decidua Forssk and Digera muricata L. Mart showed the presence of class II. Whereas, rest of 58 species showed presence of class I. The soil characteristics of the polluted industrial area were also analyzed and related with the vegetation of the polluted areas. The Industrial area soil was coarse in texture and ranged from sandy clay loam to sandy loam. The soil was acidic to alkaline in nature. Maximum water holding capacity, bulk density, porosity, CaCO/sub 3/, pH, organic matter, total organic carbon, chloride, electrical conductivity, total dissolved salt, available sulphur contents, exchangeable sodium and potassium were recorded in wide range. It was concluded that certain edaphic factors due to industrial activities and induction of pollutants were responsible for variation in vegetation composition of the study area. (author)

[en] Sensitivity reduction in amorphous Se-based photoconductive x-ray image detectors due to previous exposures is studied by Monte Carlo simulation. Collected charge, hence x-ray sensitivity, is calculated by considering deep carrier trapping, taking into account the effects of trap filling, recombination between trapped and drifting carriers and the generation of x-ray induced new deep trap centers. Space charge effects on the electric field, and hence, the effects of electric field on electron hole pair generation and charge transport are also considered. The comparison of the model with the experimental data reveals that the recombination between trapped and oppositely charged drifting carriers and x-ray induced new deep trap centers are mainly responsible for the sensitivity reduction in biased a-Se-based x-ray detectors

[en] A cascaded linear system model that includes incomplete charge collection and interaction-depth dependent conversion gain and charge collection stages is considered for the calculation of the zero spatial frequency detective quantum efficiency, DQE(0), of a direct conversion x-ray image detector. The model includes signal and noise propagations in the following stages: (1) x-ray attenuation, (2) conversion gain, (3) charge collection, and (4) addition of electronic noise. The primary x-ray photon interaction and also the secondary K-fluorescent photon interaction are included in determining the interaction-depth dependent conversion gain across the photoconductor. We examine DQE(0) of a-Se detectors for fluoroscopic applications as a function of photoconductor thickness with varying amounts of electronic noise and x-ray exposure under (a) constant field, and (b) constant voltage operating conditions. We show that there is an optimum photoconductor thickness, which maximizes DQE(0) under a constant voltage operation. The optimum thickness depends on the added electronic noise, x-ray exposure, charge collection efficiency and bias voltage. For the quantities mentioned above that are appropriate for a-Se detectors and fluoroscopic applications, the optimum a-Se thickness is ∼700 μm and the corresponding DQE is ∼0.4. It is shown that the DQE depends strongly on the charge transport properties of the photoconductors. With the radiation-receiving electrode negatively biased, the DQE is more dependent on electron lifetime (τ_e) than hole lifetime (τ_h). Full electron trapping, (τ_e=0) reduces the DQE by about 73.3% at the detector thickness of 1000 μm whereas full hole trapping (τ_h=0) reduces the DQE by about 43.7%. The DQE for the negative bias is lower than for the positive bias, and the difference in DQE, as expected, increases with the photoconductor thickness because of the asymmetric transport properties of holes and electrons in a-Se. The present results show that the DQE generally does not continue to improve with greater photoconductor thickness because of charge carrier trapping effects. The DQE of a polyenergetic x-ray beam is only slightly lower than a monoenergetic x-ray beam with the same average photon energy. The theoretical model shows a very good agreement with the experimental DQE versus exposure characteristics published in the literature