Browsing by Subject "lead"

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Open Access
Phytoremediation of Cu, Cr and Pb mixtures by lemna minor
(2013) Üçüncü, E.; Tunca, E.; Fikirdeşici, S.; Özkan, A.D.; Altindaǧ, A.
The present study reports the capacity of the aquatic macrophyte Lemna minor to remediate combinations of Cu(II), Pb(II) and Cr(III) from a simulated natural environment. The effect of these metal mixtures on the growth of L. minor was also investigated using growth rate and biomass inhibition calculations. L. minor was successful in removing Cr and Pb from the water, and it remained an effective remediation agent when both metals were present in the environment. However, a relatively low absorption capacity was observed for Cu, increasing concentrations of which were associated with significant decreases in growth rate. No statistically significant difference was found between the 24 h and 7 days absorption rates of Cu, Pb and Cr, suggesting that, at the concentrations tested, equilibrium occurs within 24 h of metal exposure. © 2013 Springer Science+Business Media New York.
Open Access
A simple analytical expression for the gradient induced potential on active implants during MRI
(2012) Turk, E.A.; Kopanoglu, E.; Guney, S.; Bugdayci, K.E.; Ider, Y. Z.; Erturk, V. B.; Atalar, Ergin
During magnetic resonance imaging, there is an interaction between the time-varying magnetic fields and the active implantable medical devices (AIMD). In this study, in order to express the nature of this interaction, simplified analytical expressions for the electric fields induced by time-varying magnetic fields are derived inside a homogeneous cylindrical volume. With these analytical expressions, the gradient induced potential on the electrodes of the AIMD can be approximately calculated if the position of the lead inside the body is known. By utilizing the fact that gradient coils produce linear magnetic field in a volume of interest, the simplified closed form electric field expressions are defined. Using these simplified expressions, the induced potential on an implant electrode has been computed approximately for various lead positions on a cylindrical phantom and verified by comparing with the measured potentials for these sample conditions. In addition, the validity of the method was tested with isolated frog leg stimulation experiments. As a result, these simplified expressions may help in assessing the gradient-induced stimulation risk to the patients with implants.
Open Access
Tissue distribution and correlation profiles of heavy-metal accumulation in the freshwater crayfish astacus leptodactylus
(2013) Tunca, E.; Ucuncu, E.; Ozkan, A.D.; Ulger, Z.E.; Tekinay, T.
The present work details the analysis of heavy-metal and metalloid concentrations in exoskeleton, gill, hepatopancreas, and abdominal muscle tissues of 60 crayfish (Astacus leptodactylus) specimens collected from Lake HirfanlI, a dam lake located in KIrşehir (Turkey) with a low metal-contamination profile. Concentrations of 11 metals (aluminum [Al], chromium [Cd], manganese [Mn], cobalt [Co], nickel [Ni], copper [Cu], molybdenum [Mo], silver [Ag], cadmium [Cd], mercury [Hg], and lead [Pb]) and a metalloid (arsenic [As]) were measured by inductively coupled plasma-mass spectrometry, and the relative frequencies of the most abundant isotopes of Cr, Cu, Ag, Cd, Hg, and Pb were evaluated. Three correlation trends were evaluated between the following: (1) different elements in the each individual tissue, (2) individual elements in different tissues, and (3) different elements in different tissues. In addition, correlation rates of growth parameters (weight, cephalothorax length, and total length) with heavy-metal and metalloid concentrations in each tissue were investigated. Our results suggest that substantial differences in metal and metalloid-accumulation levels exist between male and female specimens, with stronger correlations between the heavy-metal concentrations observed in the male cohort. It is notable that correlation trends of Co, Cu, 52As, Cr, and Ni in exoskeleton of the male specimens display strong similarities. Likewise, a very strong correlation is present in Ni-Cd and Ni-Pb accumulations in abdominal muscle of the male specimens; a similar trend is present between Cd and Pb concentrations in the same tissue of female specimens. For correlation rates of different heavy metals and metalloid in different tissues, the strongest positive association observed was between 63Cu in gill and As in hepatopancreas, whereas the strongest negative correlation was between accumulated Ni in abdominal muscle and As in exoskeleton. Strong correlations between metals and metalloid accumulations were observed between exoskeleton and gill. In many cases, metal and metalloid accumulation was negatively correlated with growth parameters. Preferential accumulation of Cr and Cu isotopes was observed in different tissues, suggesting that significant amounts of isotope fractionation occur during heavy-metal accumulation. Relatively low correlation rates were observed between 52Cr/ 53Cr and 63Cu/65Cu concentrations in several tissue types in both male and female cohorts, whereas no such trend was observed between Cd and Pb isotopes. © 2013 Springer Science+Business Media New York.