Hydrothermal synthesis and characterization of nanocrystalline ZrO2 and surface modification with 2-acetoacetoxyethyl methacrylate

For the utilization as inorganic/organic hybrid nanomaterials for optical purposes, nanocrytalline tetragonal ZrO₂ was synthesized by hydrothermal method using zirconium(IV)-n-propoxide as precursor material. Surface of the ZrO₂ particles was then modified with 2-acetoacetoxyethyl methacrylate used as a copolymer for coatings. X-ray diffraction analysis revealed that both ZrO₂ and modified ZrO₂ are in tetragonal crystalline phase. As proved by transmission electron microscope and particle size analysis, average particle sizes of ZrO₂ and modified ZrO₂ were found as 6.22 and 14.7 nm, respectively. ZrO₂ powder was easily dispersed either in water or n-hexane. Ultraviolet diffuse reflectance spectrophotometer analysis for ZrO₂ and surface modified ZrO₂ showed that maximum absorption peaks are at 215 and 225 nm, respectively.     

Determination of biothiols by a novel on-line HPLC-DTNB assay with post-column detection

A novel on-line HPLC-DTNB method was developed for the selective determination of biologically important thiols (biothiols) such as l-cysteine (Cys), glutathione (GSH), homocysteine (HCys), N-acetylcysteine (NAC), and 1,4-dithioerythritol (DTE) in pharmaceuticals and tissue homogenates. The biothiols were separated on C18 column using gradient elution, reacted with the postcolumn reagent, DTNB in 0.5% M-β-CD (w/v) solution at pH 8, to form yellow-colored 5-thio-2-nitrobenzoic acid (TNB), and monitored with a PDA detector (λ = 410 nm). With the optimized conditions for chromatography and the post-column derivatization, 40 nM of NAC, 40 nM of Cys, and 50 nM of GSH can be determined. The relative standard deviations of the recommended method were in the range of 3.2–5.4% for 50 μM biothiols. The negative peaks of biothiol constituents were monitored by measuring the increase in absorbance due to TNB chromophore. The detection limits of biothiols at 410 nm (in the range of 0.04–0.58 μM) after post-column derivatization with DTNB + M-β-CD were much lower than those at 205 nm UV-detection without derivatization, and were distinctly lower than those with post-column DTNB alone. The method is rapid, inexpensive, versatile, nonlaborious, uses stable reagents, and enables the on-line qualitative and quantitative estimation of biothiol constituents of biological fluids and pharmaceuticals.     

Exact solutions of nonlinear evolution equations with variable coefficients using exp-function method

In this paper, we apply the exp-function method to construct generalized solitary and periodic solutions of nonlinear evolution equations with variable coefficients. The proposed technique is tested on the Zakharov-Kuznetsov and (2+1)-dimensional Broer-Kaup equations with variable coefficients. These equations play a very important role in mathematical physics and engineering sciences. The suggested algorithm is quite efficient and is practically well suited for use in these problems. Obtained results clearly indicate the reliability and efficiency of the proposed exp-function method.     

Structural and optical properties of thin films prepared from surface modified ZrO2

This paper describes the preparation and characterization of ZrO₂ thin films deposited on silicon wafer by spin coating method. Nanocrystalline ZrO₂ was synthesized by hydrothermal method using zirconium (IV)-n-propoxide as a precursor material. Surface of the ZrO₂ particles was then modified with 2-acetoacetoxyethyl methacrylate used as a copolymer for coatings. The optical properties, nanostructure and surface morphology of the thin films prepared from surface modified ZrO₂ nanoparticles were examined by optical spectroscopy, X-ray diffraction and scanning electron microscopy, respectively. It was found that the films deposited on silicon wafer have crystalline structure of monoclinic (111) at temperature of 150 °C. It was observed that films depict very dense material that does not present any granular or columnar structure. It was found that optical transparency of thin ZrO₂ films distributed in the range of 30-40 percent in the spectral range 400-800 nm. Refractive index of ZrO₂ films were determined as functions of ZrO₂ content and it was found that the refractive index increases from 1.547 to 1.643 with increased ZrO₂ content.     

Influence of the local environment and short-range order on the heats of formation of binary alloys

The concentration dependences of the heats of formation (H(x)) of disordered binary alloys of iron and cobalt with titanium have been calculated in both the single-site approximation and with allowance for the local environment. The dependence of H of equiatomic alloys on the short-range order in the first coordination sphere is investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 62–66, August, 1980.     

Hydrogen ion-selective poly(vinyl chloride) membrane electrode based on a p-tert-butylcalix[4]arene-oxacrown-4

A hydrogen ion-selective poly(vinyl chloride) (PVC) membrane electrode was developed using p-tert-butylcalix[4]arene-oxacrown-4 as ionophore. Apart from the ionophore, plasticisers and lipophilic anions were blended, in various proportions, with PVC in tetrahydrofurane and mixtures so prepared were poured onto glass surfaces to form the membrane. 2-Nitrophenylpentylether has proved to be the best alternative as plasticiser and the lipophilic anions tried have turned out to have an adverse effect on the pH response. The electrode of the optimum characteristics had a composition of 2% p-tert-butylcalix[4]arene-oxacrown-4, 68.3% o-NPPE and 29.7% PVC. The electrode showed an apparent Nernstian response in the pH range 2-11 with a slope of 54.2±0.4 mV pH⁻¹ at 20±1 °C. It has a rapid potential-response to changes of pH, high ion selectivity towards lithium, sodium and potassium, and other characteristics comparable to those reported for the conventional pH glass membrane electrode. It appears to be a suitable potentiometric indicator electrode specifically for hydrofluoric acid solutions.     

Calculation of thermodynamic characteristics of diluted alloys of scandium and titanium in copper with the structure of its d-band taken into account

Calculation is performed of first partial heats of solution and of initial curvatures of isotherms of enthalpies of formation of diluted alloys of scandium and titanium in copper, using information on the detailed structure of copper d-band. Influence of s-electrons and the effect of s-d hybridization was not taken into account in the calculation. Comparison is performed of the values obtained with experimental data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 39–43, February, 1985.     

Multi-channel metabolic imaging, with SENSE reconstruction, of hyperpolarized [1-(13)C] pyruvate in a live rat at 3.0 tesla on a clinical MR scanner

We report metabolic images of (13)C, following injection of a bolus of hyperpolarized [1-(13)C] pyruvate in a live rat. The data were acquired on a clinical scanner, using custom coils for volume transmission and array reception. Proton blocking of all carbon resonators enabled proton anatomic imaging with the system body coil, to allow for registration of anatomic and metabolic images, for which good correlation was achieved, with some anatomic features (kidney and heart) clearly visible in a carbon image, without reference to the corresponding proton image. Parallel imaging with sensitivity encoding was used to increase the spatial resolution in the SI direction of the rat. The signal to noise ratio in was in some instances unexpectedly high in the parallel images; variability of the polarization among different trials, plus partial volume effects, are noted as a possible cause of this.