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[en] The phosphorus uptake by the yeasts Torulopsis utilis and Torula cremoris, cultivated on sweet potato mash with the density of 4,8 and 160Blg, were investigated to establish an optimal phosphorus dose for protein biosynthesis on this substrate. For determining the phosphorus uptake, 32P labelled KH2PO4 was used. Bulk protein content was determined, to determine the correlation between the phosphorus uptake by yeasts and protein synthesis on the one hand and the use of sugars on the other
[en] We stated that crystalline grains in the nanocrystalline alloys obtained by a proper annealing consist of the ordered α-FeCo phase. However, in the partially crystallized alloys during a rapid solidification α-FeCo phase is completely disordered. In both, the amorphous and nanocrystalline samples broad disaccommodation spectra are observed. The activation energies of relaxation processes range from 1.00 to 1.34 eV and from 1.47 to 1.82 eV for the amorphous and nanocrystalline samples, respectively
[en] Germanate glasses are interesting materials for photonics applications. Particularly PbO containing glasses are interesting because they combine high photomechanical stability and chemical durability with temperature stability and excellent transmission in the infrared spectral region (up to 4,5 μm). Besides the low phonon energy (around 700 cm-1) compared to borates (around 1400cm -1) and phosphates (around 1200 cm-1) the glasses indicate low nonradiative relaxation rates and makes up conversion easily observable. The results of measurements of a dependence of SHG in these glasses with different Er, Eu, Ag impurities are reported together with thermal measurements of these glasses. We compared the DSC traces with temperature dependences of second order susceptibilities enhancement. Temperature dependence of the second-order optical susceptibilities detected by the SHG correlates well with the differential scanning calorimetric (DSC) measurements. It is demonstrated that although both methods give an evidence of the phase transitions the non-linear optical one is much more sensitive and temperature resolved. Possible physical origins of the observed phenomenon are discussed.
[en] After annealing alloys below crystallization temperatures, the decrease of the average hyperfine field due to the invar effect is observed. At early stages of crystallization, the iron content in the amorphous matrix is the same as in the as-quenched state. The amorphous samples show broad disaccommodation spectra with activation energies from 0.6 to 0.9 eV. The highest initial magnetic susceptibility was obtained for the nanocrystalline Fe85.4Zr5.8Nb1B6.8Cu1 alloy. However, the best thermal stability of the susceptibility is observed for the Fe85.4Zr6.8B6.8Cu1 alloy
[en] Passive Q-switching is presented in a novel, closed-loop, diode side-pumped Nd:YAG slab laser. Q-switched generation provided five pulse series with total energy of 120 mJ, 1 MW peak power and 24 ns single pulse width for maximal pump energy of 840 mJ. Beam quality parameter M2 was less than 2. Generation parameters in both four-wave mixing and classic linear resonator with similar length were compared. (letter)
[en] A complex spectroscopic study of Ca4GdO(BO3)3 (GdCOB) doped with Pr3+ has been performed experimentally and theoretically using the ab initio configuration interaction (CI) calculation method. This approach is based on the numerical discrete-variational Dirac-Slater cluster calculations and numerical solution of the Dirac equation using the local density approximation. All relativistic effects are considered automatically by virtue of the relativistic Hamiltonian. The principal novelty of the approach is that during the calculations the molecular orbitals (MO) consisting of the atomic wave functions of the central ion (in this case, Pr3+) and its nearest ligands (O2-) are used. The principal advantage of the method consists in ab initio approach not requiring the fitting parameters like in the widely used crystal field approach or FLAPW requiring the muffin tin orbitals. Such a complete basis set allows not only to evaluate the main energy terms, but also to analyze the covalent charge transfer effects and to evaluate the energy separations between different MO groups. Using the GdCOB:Pr single crystals as good probes to check the introduced theoretical model, we report the calculations of the complete energy terms (including unoccupied excited MO) for the principal [PrO6]9- cluster. Theoretical simulations are verified by comparison with both the ground and excited state absorption. A particular interest presents estimations of the crystal field splitting of the localized Pr3+ 5d orbitals (10 Dq) (about 20,800 cm-1) and energy separations between the 2p (O2-)-4f (Pr3+), 2p (O2-)-5d (Pr3+), and 2p (O2-)-6s (Pr3+) MO (13,300, 40,050, and 78,900 cm-1, respectively). These values are in sufficient agreement with performed excited state absorption experimental data and available ground state absorption data including the low temperatures study at 4.2 K. Several discrepancies between the calculated and measured intensities of the optical transitions can be explained by contribution of electron-phonon coupling and sample's imperfections. In addition to the first principles calculations, crystal field theory was used to calculate the Pr3+ energy levels; a set of crystal field parameters for Pr3+ ion in GdCOB crystal is suggested
[en] Experimental measurements of linear electro-optical coefficients are reported for BixLayScz(BO3)4 (x + y + z = 4) (BLSB) nanocrystallites incorporated into polymer matrices of different polarizabilities. The nanochromophores in the matrices were oriented by external dc-electric field during spin coating. The measurements were performed under illumination of CW semiconducting GaAlAs laser emitting at 1040 nm. We have achieved the maximal values of the Pockels coefficients equal to 3.5 pm/V for the BLSB nanocrystallites incorporated into the polycarbonate matrices. The optimal sizes of nanocrystallites were below 20 nm and their content was equal to about 7.5% (in weight. units). We have eliminated a contribution to the Pockels effect due to the piezo-optical coefficients as well as due to other bothering factors. The temperature influence is very low (due to low ionic contribution), and do not exceed 6%, which is related to low contribution of electron-phonon interaction to the Pockels effect. So these alloys may be proposed as promising materials for high power laser electro-optic modulators.
[en] PbO-Sb2O3-B2O3 glasses mixed with different concentrations of CoO (ranging from 0 to 2.0 mol%) were crystallized. The samples were characterized by x-ray diffraction, scanning electron microscopy and differential scanning calorimetric techniques. The x-ray diffraction and scanning electron microscopic studies have revealed the presence of CoSb2O6, Co2.33Sb0.67O4, Pb5Sb2O8,Pb3(SbO4)2, PbB4O7 and Co3O4 crystalline phases in these samples. The DSC studies have indicated the spreading of the crystallization from the inside to the surface of the samples as the concentration of the crystallizing agent is increased. The IR and Raman spectroscopic studies have pointed out the existence of conventional BO3, BO4, SbO4 and also CoIII-O structural units in the glass ceramic samples. These studies have further indicated the decreasing concentration of symmetrical structural vibrational groups with increase in the concentration of CoO. The results of various studies, namely dielectric properties over a range of frequency and temperature, photo-induced birefringence, optical absorption, fluorescence and magnetic susceptibility at room temperature of PbO-Sb2O3-B2O3:CoO glass ceramics, have also been reported. The variations observed as a function of the concentration of crystallizing agent in all these properties have been analyzed in the light of different oxidation states and environments of cobalt ions in the glass ceramic network.
[en] A novel infrared optoelectronic material Tl_4CdI_6 was studied using the density functional theory (DFT)-based techniques. Its structural, electronic, optical and elastic properties were all calculated in the generalized gradient approximation (GGA) with the Perdew–Burke–Ernzerhof (PBE) and the local density approximation (LDA) with the Ceperley-Alder–Perdew-Zunger (CA–PZ) functionals. The studied material is a direct band gap semiconductor with the calculated band gaps of 2.043 eV (GGA) and 1.627 eV (LDA). The wavelength dependence of the refractive index was fitted to the Sellmeier equation in the spectral range from 400 to 2000 nm. Good agreement between the GGA-calculated values of refractive index and experimental data was achieved. To the best of our knowledge, this is the first consistent theoretical description of the title compound, which includes calculations and analysis of the structural, electronic, optical and elastic properties. - Graphical abstract: Display Omitted - Highlights: • Infrared optoelectronic material Tl_4CdI_6 was studied using ab initio methods. • Structural, electronic, optical and elastic properties were calculated. • Independent components of the elastic constants tensor were calculated. • Good agreement with available experimental results was achieved