Determination of the enthalpy of fusion of K<Subscript>3</Subscript>NbO<Subscript>2</Subscript>F<Subscript>4</Subscript>

Areas of fusion and crystallization peaks of K₃NbO₂F₄ were measured using the DCS mode of a high-temperature calorimeter (SETARAM 1800 K). On the basis of these quantities, considering the temperature dependence of the calorimeter sensitivity, the value of the fusion enthalpy of K₃NbO₂F₄ of (98 ± 6) kJ mol⁻¹ was determined at the fusion temperature of 1257 K.     

Crystallization of TiO2 xerogel

Journal of Thermal Analysis and Calorimetry - For utilization of TiO2 in advanced applications, TiO2 after thermal treatment has to be in crystalline phase of anatase, because it gives the desired...     

High throughput method for multielemental analysis of horse hair by oaTOF-ICP-MS

An approach for high throughput reliable multielemental analysis of trace elements in a large number of horse hair samples was designed. Suitability of time-of-flight mass spectrometer (oaTOF-ICP-MS) for fast determination of unlimited numbers of isotopes in the low volume samples was demonstrated. Due to quasi-simultaneous capability of the oaTOF-ICP-MS the large number of highly valuated data with unaffected isotopic ratio in a very short time could be obtained. The choice of horse hair was obvious because of easy reachability and clear conception about horse nutritional habits and stabling. Such large data set with preserved isotopic ratios is ideal for statistical evaluation which could reveal some interesting interconnection between elemental composition of horse hair and the way of stabling, feeding, etc. Statistical treatment of the data is not a part of this study and will be presented later. We collected one hundred horse hair samples from horse stables through Czech Republic. Samples were washed by optimized washing process to eliminate exogenic contamination prior to digestion and following analysis. A determination of 36 elements (As, Au, B, Be, Cd, Ce, Co, Cr, Dy, Er, Eu, Ga, Gd, Ge, Ho, La, Li, Lu, Nd, Ni, Pb, Pd, Pr, Pt, Rb, Sb, Sc, Sm, Ta, Tb, Te, Tm, U, V, Y, Yb) in horse hair by oaTOF-ICP-MS was optimized. A throughput of 100 samples with unlimited numbers of isotopes per 6 h was achieved. Proposed very fast multielemental method preserves isotopic ratios, and therefore, is undoubtedly highly suitable for statistical studies. Detection limits of the proposed method ranged from 0.13 μg kg^?1 (Eu, Gd, Tm) to 27.9 μg kg^?1 (Au), except for Ni (48.5 μg kg^?1) that is probably affected by contamination raised from nickel cones.     

Estimation of seasonal correction factor for indoor radon concentration in Slovakia: a preliminary survey

Journal of Radioanalytical and Nuclear Chemistry - In this study, 56 rooms were monitored throughout the year in four stages based on 3-month indoor radon measurements. The first seasonal...     

Determination of the enthalpy of fusion of K<Subscript>3</Subscript>TaO<Subscript>2</Subscript>F<Subscript>4</Subscript> and KTaF<Subscript>6</Subscript>

Areas of fusion and crystallization peaks of K₃TaO₂F₄ and KTaF₆ were measured using the DSC mode of a high-temperature calorimeter (SETARAM 1800 K). On the basis of these quantities, considering the temperature dependence of the calorimeter sensitivity, values of the fusion enthalpy of K₃TaO₂F₄ at the fusion temperature of 1181 K of (43 ± 4) kJ mol⁻¹ and of KTaF₆ at the fusion temperature of 760 K of (8 ± 1) kJ mol⁻¹ were determined.     

Spectroscopic study of protonation of oligonucleotides containing adenine and cytosine

Acidobasic properties of purine and pyrimidine bases (adenine, cytosine) and relevant nucleosides (adenosine, cytidine) were studied by means of glass-electrode potentiometry and the respective dissociation constants were determined under given experimental conditions (I = 0.1 M (NaCl), t = (25.0 ± 0.1) °C): adenine (pK _HL = 9.65 ± 0.04, pK _H2L = 4.18 ± 0.04), adenosine (pK _H2L = 3.59 ± 0.05), cytosine (pK _H2L = 4.56 ± 0.01), cytidine (pK _H2L = 4.16 ± 0.02). In addition, thermodynamic parameters for bases: adenine (ΔH ⁰ = (−17 ± 4) kJ mol⁻¹, ΔS ⁰ = (23 ± 13) J K⁻¹ mol⁻¹), cytosine (ΔH ⁰ = (−22 ± 1) kJ mol⁻¹, ΔS ⁰ = (13 ± 5) J K⁻¹ mol⁻¹) were calculated. Acidobasic behavior of oligonucleotides (5′CAC-CAC-CAC3′ = (CAC)₃, 5′AAA-CCC-CCC3′ = A₃C₆, 5′CCC-AAA-CCC3′ = C₃A₃C₃) was studied under the same experimental conditions by molecular absorption spectroscopy. pH-dependent spectral datasets were analyzed by means of advanced chemometric techniques (EFA, MCR-ALS) and the presence of hemiprotonated species concerning (C⁺-C) a non-canonical pair (i-motif) in titled oligonucleotides was proposed in order to explain experimental data obtained according to literature.     

Gold Microelectrodes Decorated by Spike-Like Nanostructures as a Promising Non-Enzymatic Glucose Sensor

Gold microelectrodes modified via easy method by gold nanostructures were studied as an ideal substrate for non-enzymatic glucose detection. The results confirmed that spike-like nanostructure displays the best electrocatalytic activity because of higher amount of edges. Results prove that modified electrode is able to detect glucose in two linear ranges from 100–500 μM and 0.5–30 mM, with limit of detection (48 μM), high sensitivities for both linear ranges (1.7 μA/mM and 2.4 μA/mM), and good stability. In addition, modified electrodes were able to detect glucose in blood serum. This work demonstrates glucose detection on miniaturised system.     

Capillary electrophoresis-mass spectrometry - a fast and reliable tool for the monitoring of milk adulteration

The development of a rapid, simple and accurate analytical method aimed at the detection and quantification of bovine milk in either ovine or caprine milk samples by means of CE-MS analyses of whey proteins with high-ionic strength and presence of acidic running buffer is described. The high-ionic strength buffer was used in order to minimize the problems with the adsorption of the proteins onto the fused-silica capillary wall. The acidic running electrolyte, pH 1.9, was used to support the production of positive ions in electrospray. Highly linear dependences of the ratio of the sum of non-bovine beta-lactoglobulins (ovine or caprine) to the total beta-lactoglobulins in milk mixture (bovine plus ovine or bovine plus caprine) vs. the volume percentage of added bovine milk in ovine (or caprine) milk were obtained. This technique allowed the fast and reliable evaluation of milk adulteration. The amount of bovine milk added into the "non-bovine" ones can be well within the concentration range of 5-95%.     

An Iterative Technique for Construction of Invariant Subspaces

The restarted GMRES(m ) method for solving linear systems Ax = b is attractive when a good preconditioner is available. The determining of efficient preconditioners is often connected to a construction of an A –invariant subspace corresponding to eigenvalues closest to zero. One class of methods for determination of invariant subspaces is based on the construction of polynomial filters. We study the usage of Tchebychev polynomials for constructing suitable filters. Applying filters on the initial restart vectors amplifies the components of eigenvectors belonging to the small (wanted) eigenvalues and damp the remaining (unwanted) components. The presented convergence theorem describes the repeated application of filters for the construction of the wanted eigenspace of the matrix A . (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)