Gold and Silver Extraction from Leach Solutions

There has been carried out an investigation on the extraction of gold and silver from thiosulfate solutions: standard test and technological solutions of chemical and electrochemical leaching. The influence of related metals on the process of extracting gold from solution was studied. There has been conducted a comparative study of the IR spectra of solutions after the sorption of gold, silver and related metals

Phonon Spectrum in Hydroxyapatite: Calculations and EPR Study at Low Temperatures

© 2015, Springer Science+Business Media New York.Density functional theory-based calculations within the framework of the plane-wave pseudopotential approach are carried out to define the phonon spectrum of hydroxyapatite Ca10(PO4)6(OH)2 (HAp). It allows to describe the temperature dependence of the electronic spin-lattice relaxation time T 1e of the radiation-induced stable radical NO32- in HAp, which was measured in X-band (9 GHz, magnetic field strength of 0.34 T) in the temperature range T = (10–300) K. It is shown that the temperature behavior of T1e at T> 20 K can be fitted via two-phonon Raman type processes with the Debye temperature ΘD≈280K evaluated from the phonon spectrum

Phonon Spectrum in Hydroxyapatite: Calculations and EPR Study at Low Temperatures

© 2015 Springer Science+Business Media New York Density functional theory-based calculations within the framework of the plane-wave pseudopotential approach are carried out to define the phonon spectrum of hydroxyapatite (Formula presented.) (HAp). It allows to describe the temperature dependence of the electronic spin-lattice relaxation time (Formula presented.) of the radiation-induced stable radical (Formula presented.) in HAp, which was measured in X-band (9 GHz, magnetic field strength of 0.34 T) in the temperature range T = (10–300) K. It is shown that the temperature behavior of (Formula presented.) at (Formula presented.) 20 K can be fitted via two-phonon Raman type processes with the Debye temperature (Formula presented.) evaluated from the phonon spectrum

Connection Between the Carotid Plaque Instability and Paramagnetic Properties of the Intrinsic Mn²⁺ Ions

© 2016, Springer Science+Business Media New York.The pulsed W-band (the microwave frequency of 94 GHz, magnetic field of 3.4 T) electron paramagnetic resonance (EPR) comparative studies of a series of 20 atherosclerotic plaques (AP) obtained during carotid endarterectomy in patients with atherosclerosis is presented. The AP stability was established by ultrasound angiography. In all of the obtained species EPR spectra due to the presence of Mn2+ ions in a crystal matrix of hydroxyapatites (HAp) is observed. The existence of HAp in plaque fragments is confirmed by X-ray diffraction analyses. The spectral parameters of Mn2+ are ascribed to two possible locations in the HAp constituent of the atherosclerotic plaques. The difference in the electronic relaxation times of T2e for Mn2+ ions in stable and unstable plaques is observed that can indicate the more homogeneous distribution of Mn2+ in stable plaques as compared to unstable species. The results can be potentially used for the understanding the mechanisms of pathological calcifications and AP stability

Radiofrequency induced heating of biodegradable orthopaedic screw implants during magnetic resonance imaging

Magnesium (Mg)-based implants have re-emerged in orthopaedic surgery as an alternative to permanent implants. Literature reveals little information on how the degradation of biodegradable implants may introduce safety implications for patient follow-up using medical imaging. Magnetic resonance imaging (MRI) benefits post-surgery monitoring of bone healing and implantation sites. Previous studies demonstrated radiofrequency (RF) heating of permanent implants caused by electromagnetic fields used in MRI. Our investigation is the first to report the effect of the degradation layer on RF-induced heating of biodegradable orthopaedic implants. WE43 orthopaedic compression screws underwent in vitro degradation. Imaging techniques were applied to assess the corrosion process and the material composition of the degraded screws. Temperature measurements were performed to quantify implant heating with respect to the degradation layer. For comparison, a commercial titanium implant screw was used. Strongest RF induced heating was observed for non-degraded WE43 screw samples. Implant heating had shown to decrease with the formation of the degradation layer. No statistical differences were observed for heating of the non-degraded WE43 material and the titanium equivalent. The highest risk of implant RF heating is most pronounced for Mg-based screws prior to degradation. Amendment to industry standards for MRI safety assessment is warranted to include biodegradable materials

Lattice vibrations of alpha'-NaV2O5

We have measured far infrared reflectance and transmittance spectra as well as Raman scattering spectra of \alpha'-NaV2O5 single crystals for all the principal polarizations. The temperature range above the phase transition temperature T_c=35 K was investigated, mainly. On the basis of this experimental study and of the lattice dynamics calculations we conclude that the symmetry of NaV2O5 in the high temperature phase is described by the centrosymmetric D_{2h}^{13} space group. The assignment of the observed phonons is given. Values of dielectric constants are obtained from the infrared data. Asymmetric shapes of several infrared lines as well as higher order infrared vibrational spectra are discussed. The crystal field energy levels of the 3d electron localized at the V^{4+} site have been calculated in the framework of the exchange charge model using the values of effective charges obtained from the lattice dynamics calculations. According to the results of these calculations, the earlier observed broad optical bands in the region of 1 eV can be interpreted as phonon assisted d-d transitions.Comment: 12 pages, 8 figures, 5 tables; submitted to PR

Phonon Spectrum in Hydroxyapatite: Calculations and EPR Study at Low Temperatures

© 2015, Springer Science+Business Media New York.Density functional theory-based calculations within the framework of the plane-wave pseudopotential approach are carried out to define the phonon spectrum of hydroxyapatite Ca10(PO4)6(OH)2 (HAp). It allows to describe the temperature dependence of the electronic spin-lattice relaxation time T 1e of the radiation-induced stable radical NO32- in HAp, which was measured in X-band (9 GHz, magnetic field strength of 0.34 T) in the temperature range T = (10–300) K. It is shown that the temperature behavior of T1e at T> 20 K can be fitted via two-phonon Raman type processes with the Debye temperature ΘD≈280K evaluated from the phonon spectrum

Phonon Spectrum in Hydroxyapatite: Calculations and EPR Study at Low Temperatures

© 2015 Springer Science+Business Media New York Density functional theory-based calculations within the framework of the plane-wave pseudopotential approach are carried out to define the phonon spectrum of hydroxyapatite (Formula presented.) (HAp). It allows to describe the temperature dependence of the electronic spin-lattice relaxation time (Formula presented.) of the radiation-induced stable radical (Formula presented.) in HAp, which was measured in X-band (9 GHz, magnetic field strength of 0.34 T) in the temperature range T = (10–300) K. It is shown that the temperature behavior of (Formula presented.) at (Formula presented.) 20 K can be fitted via two-phonon Raman type processes with the Debye temperature (Formula presented.) evaluated from the phonon spectrum

Phonon Spectrum in Hydroxyapatite: Calculations and EPR Study at Low Temperatures

© 2015 Springer Science+Business Media New York Density functional theory-based calculations within the framework of the plane-wave pseudopotential approach are carried out to define the phonon spectrum of hydroxyapatite (Formula presented.) (HAp). It allows to describe the temperature dependence of the electronic spin-lattice relaxation time (Formula presented.) of the radiation-induced stable radical (Formula presented.) in HAp, which was measured in X-band (9 GHz, magnetic field strength of 0.34 T) in the temperature range T = (10–300) K. It is shown that the temperature behavior of (Formula presented.) at (Formula presented.) 20 K can be fitted via two-phonon Raman type processes with the Debye temperature (Formula presented.) evaluated from the phonon spectrum

Phonon Spectrum in Hydroxyapatite: Calculations and EPR Study at Low Temperatures

© 2015, Springer Science+Business Media New York.Density functional theory-based calculations within the framework of the plane-wave pseudopotential approach are carried out to define the phonon spectrum of hydroxyapatite Ca10(PO4)6(OH)2 (HAp). It allows to describe the temperature dependence of the electronic spin-lattice relaxation time T 1e of the radiation-induced stable radical NO32- in HAp, which was measured in X-band (9 GHz, magnetic field strength of 0.34 T) in the temperature range T = (10–300) K. It is shown that the temperature behavior of T1e at T> 20 K can be fitted via two-phonon Raman type processes with the Debye temperature ΘD≈280K evaluated from the phonon spectrum