The use of cationic surfactants to control the structure of zinc oxide films prepared by chemical vapour deposition

This paper describes a powerful and versatile new method for controlling the structure of zinc oxide thin films prepared by aerosol assisted chemical vapour deposition, based on the use of a common surfactant. The technique combines the benefits of solution and vapour based methods and leads to high quality morphologically-defined and orientated thin films.     

Diffraction of light by ultrasound in paratellurite crystals under Fresnel reflection conditions

We show that layers of acousto-optic gyrotropic paratellurite crystals perturbed by ultrasound can be used as efficient light modulators in transmission and reflection mode. We have established that the relative intensities of the diffracted waves are determined by the ratio of the refractive indices of the bounding media, the intensity of the ultrasound, and the thickness of the modulated layer. We show that for an asymmetric diffraction structure, efficient acousto-optic conversion is possible in reflection mode, and the weak effect of the gyrotropy is due to its suppression by Fresnel reflection at the boundaries of the layer. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 819–823, November–December, 2006.     

Optoacoustic diagnostics of absorbing media

We have calculated the intensities of ultrasonic waves excited by counter-propagating light waves of different frequencies and scattered by spherical defects in absorbing isotropic media. We have analyzed the intensity of the scattered sound as a function of the scattering angle and the position of the defect relative to the entry face of the acoustic waveguide. We have shown that for hollow spherical defects, the intensity of the scattered sound tends toward zero for scattering angles close to 90o, and for significantly smaller angles for dense inclusions. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 686–689, September–October, 2006.     

Synthesis of Phospholipid?Ribavirin Conjugates

New conjugates of antiviral nucleoside Ribavirin (=1‐(β‐D ‐ribofuranosyl)‐1H‐1,2,4‐triazole‐3‐carboxamide; 1 ) with 1,2‐ and 1,3‐diacyl glycerophosphates have been synthesized by the phosphoramidite method. A combination of 2′,3′‐phenylboronate protecting group for the sugar moiety of the ribonucleoside 1 and 2‐cyanoethyl protection for the phosphate fragment ensured the preparation of the desired compounds with reasonable yields via a small number of synthetic steps.     

Influence of maturation conditions of hydroxyapatite gel on the composition of xerogel

The influence exerted by conditions of the secondary maturation of hydroxyapatite gel on the composition of a xerogel was determined. It was found that the prolonged stage of the secondary maturation within pH 7.6–7.1, the low pH value of distilled water or a solution of the acid (HCl, H₃PO₄) and the long time of contact of the hydoxyapatite gel with the acid solution assist the formation of α-tricalcium phosphate impurity. A singlephase hydroxyapatite is formed in the presence of distilled water with pH 5.3–5.6, as the time of the secondary stage of maturation of hydroxyapatite gel within pH 7.6–7.1 is decreased and the total washing time is decreased up to 34–40 days.     

Polarization-Independent Ultrasonic Modulation of Light in Gyrotropic Cubic Bismuth Germanate Crystals

An intermediate regime of light diffraction by ultrasound propagating along the [001] and [110] axes of a gyrotropic cubic bismuth germanate crystal is investigated. The possibility of polarization-independent light modulation in the intermediate regime of diffraction close to the Bragg regime is shown. The dependences of the diffraction efficiency on the incident light polarization azimuth at different ultrasonic wave intensities are given.     

Salt Stress Mitigation via the Foliar Application of Chitosan-Functionalized Selenium and Anatase Titanium Dioxide Nanoparticles in Stevia (Stevia rebaudiana Bertoni)

High salt levels are one of the significant and major limiting factors on crop yield and productivity. Out of the available attempts made against high salt levels, engineered nanoparticles (NPs) have been widely employed and considered as effective strategies in this regard. Of these NPs, titanium dioxide nanoparticles (TiO₂ NPs) and selenium functionalized using chitosan nanoparticles (Cs–Se NPs) were applied for a quite number of plants, but their potential roles for alleviating the adverse effects of salinity on stevia remains unclear. Stevia (Stevia rebaudiana Bertoni) is one of the reputed medicinal plants due to their diterpenoid steviol glycosides (stevioside and rebaudioside A). For this reason, the current study was designed to investigate the potential of TiO₂ NPs (0, 100 and 200 mg L⁻¹) and Cs–Se NPs (0, 10 and 20 mg L⁻¹) to alleviate salt stress (0, 50 and 100 mM NaCl) in stevia. The findings of the study revealed that salinity decreased the growth and photosynthetic traits but resulted in substantial cell damage through increasing H₂O₂ and MDA content, as well as electrolyte leakage (EL). However, the application of TiO₂ NPs (100 mg L⁻¹) and Cs–Se NPs (20 mg L⁻¹) increased the growth, photosynthetic performance and activity of antioxidant enzymes, and decreased the contents of H₂O₂, MDA and EL under the saline conditions. In addition to the enhanced growth and physiological performance of the plant, the essential oil content was also increased with the treatments of TiO₂ (100 mg L⁻¹) and Cs–Se NPs (20 mg L⁻¹). In addition, the tested NPs treatments increased the concentration of stevioside (in the non-saline condition and under salinity stress) and rebaudioside A (under the salinity conditions) in stevia plants. Overall, the current findings suggest that especially 100 mg L⁻¹ TiO₂ NPs and 20 mg L⁻¹ Cs–Se could be considered as promising agents in combating high levels of salinity in the case of stevia.     

Preparation of (2′-5′)-oligonucleotides based on 6-<Emphasis Type="Italic">N</Emphasis>-benzylaminopurineriboside using the <Emphasis Type="Italic">Spicaria violacea</Emphasis> fungal enzyme complex

A method for chemico-enzymatic synthesis of (2′-5′)-oligonucleotides with 6-N-benzylaminopurineriboside as the nucleoside units was proposed. The method consisted of enzymatic hydrolysis of the oligonucleotides with mixed (2′-5′)-(3′-5′)-phosphodiesterbonds that were prepared by polymerization of 6-N-benzyladenosine-2′(3′)-monophosphate by using (3′-5′)-specific nuclease and phosphatase contained in the filtrate of culture medium of the mycelial fungus Spicaria violacea. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 64–68, January–February, 2009.     

Studies of Nanosized Iron-Doped TiO<Subscript>2</Subscript> Photocatalysts by Spectroscopic Methods

Iron-doped TiO₂ nanoparticles with iron content in the range of 0.005 < Fe/Ti < 0.3 were prepared using the flame spray pyrolysis method and investigated with CW X-band electron paramagnetic resonance (EPR), X-ray diffraction, and Fourier transform infrared spectroscopy. This allowed for the clarification of the internal organization of Fe–TiO₂ nanoparticles. Different types of Fe(III) centers were distinguished in the samples: isolated high-spin paramagnetic Fe(III) ions (S = 5/2) in rhombic ligand fields state at 0.005 < Fe/Ti < 0.05, and Fe(III) ferromagnetic clusters at Fe/Ti < 0.1. All Fe-doped samples had rather high activity for the photocatalytic mineralization of oxalic acid under visible light illumination (λ > 400 nm) at 25 °C. Correlations were made between EPR and photocatalytic activity results. The specific surface area [S] data allowed us to deduce that the isolated Fe(III) centers were responsible for the photomineralisation of oxalic acid, while the Fe(III) ferromagnetic aggregates decreased the total efficiency of the system.