background: this study was carried out to determination of heavy metals (cd, cr, cu, fe, pb, ni and zn) concentration in upstream and downstream of the entry of the wastewater (untreated urban, traditional slaughterhouse waste, leachate from solid wastes has accumulated in river and  run off waters flowing across the city ) to the tembi river. methods: samples were collected for 1 year, before ...

a new method for the determination of trace copper(ii) in food samples by cloud point extraction(cpe) combined with flame atomic absorption spectrometry(faas) is presented and evaluated. the method is based on the fact that hydrophobic complex of copper(ii) with sodium diethyldithiocarbamate (ddtc) was formed at ph 6.0 and subsequently the hydrophobic complex was extracted into surfactant-rich ...

This work presents N, O K-edge x-ray absorption near-edge structure sXANESd and Ta L3-edge extended x-ray absorption fine structure sEXAFSd studies of amorphous TasN,Od films prepared with various flow rate ratios of N2/O2. The N and O K-edge XANES and Ta L3-edge EXAFS spectra demonstrate the presence of N2 molecules. These spectra also show that TasN,Od films have similar local atomic structur...

We present accurate measurements of the central wavelengths of 4947 atomic absorption lines in the solar optical spectrum. The wavelengths, precise to a level ∼ 50 − 150 m s −1 , are given for both flux and disc-centre spectra, as measured in relatively recent FTS solar atlases. This catalogue modernizes existing sources based on photographic measurements and provides a benchmark to test and pe...

We comment on the applicability of the stationary line argument recently used by Jordan et al. (1998) to account for the unusual absorption features in the observed optical spectra of GD 229. Moreover, we provide an alternative explanation based upon the existence of neutral and singly ionized atomic helium atoms as the main elements comprising the atmosphere of this magnetized white dwarf star.

The mass absorption coefficients of tungsten and tantalum were measured with soft x-ray photons from 1450 eV to 2350 eV using an undulator source. This region includes the M3, M4, and M5 absorption edges. X-ray absorption fine structure was calculated within a real-space multiple scattering formalism; the predicted structure was observed for tungsten and to a lesser degree tantalum as well. Sep...

The singlet excited states of the model DNA duplex (dA)10.(dT)10 are studied. Calculations are performed in the exciton theory framework. Molecular dynamics calculations provide the duplex geometry. The dipolar coupling is determined using atomic transition charges. The monomer transition energies are simulated by Gaussian functions resembling the absorption bands of nucleosides in aqueous solu...

Absorption L-lines of iron ions are observed, in absorption, in spectra of Seyfert 1 galaxies by the new generation of X-ray satellites: Chandra (NASA) and XMM-Newton (ESA). Lines associated to Fe 23+ to Fe 17+ are well resolved. Whereas, those corresponding to Fe 16+ to Fe 6+ are unresolved. Forbidden transitions of the Fe 16+ to Fe 6+ ions were previously observed, for the same objects, in th...

The optical absorption spectra of magnesium oxide (MgO) nanoparticles, along with the atomic centres responsible, are studied using a combination of time-dependent density functional theory (TD-DFT) and coupled-cluster methods. We demonstrate that TD-DFT calculations on MgO nanoparticles require the use of range-separated exchange-correlation (XC-) functionals or hybrid XC-functionals with a hi...