Mössbauer studies of interactions between titanium atoms dissolved in iron

The room temperature ⁵⁷Fe Mössbauer spectra for binary iron-based solid solutions Fe_1???x Ti _x , with x in the range 0.010 ≤?x?≤ 0.045, were analysed in terms of binding energy E _b between two Ti atoms in the Fe-Ti system. The extrapolated values of E _b for x?= 0 were used for computation of enthalpy of solution of titanium in iron. The results were compared with that resulting from the Miedema’s model of alloys as well as those derived from the heat of formation of the system, obtained with both calorimetric measurements and theoretical calculations. The comparison shows that our Mössbauer spectroscopy findings are in a quite good agreement with all the other results mentioned above.     

Kinetics and Characterization of Degradation Products of Dihydralazine and Hydrochlorothiazide in Binary Mixture by HPLC-UV,LC-DAD and LC–MS Methods

Dihydralazine and hydrochlorothiazide were stored at high temperature and humidity, under UV/Vis light and different pH, as individual drugs and the mixture. Then, a sensitive and selective HPLC-UV method was developed for simultaneous determination of dihydralazine and hydrochlorothiazide in presence of their degradation products. Finally, the degradation products were characterized through LC-DAD and LC–MS methods. Dihydralazine was sensitive to high temperature and humidity, UV/Vis light and pH?≥?7. At the same time, it was resistant to acidic conditions. Hydrochlorothiazide was sensitive to high temperature and humidity, UV/Vis light and changes in pH. Its highest level of degradation was observed in 1 M HCl. Degradation of the drugs was higher when they were stressed in the mixture. In the case of dihydralazine, the percentage degradation was 5–15 times higher. What is more, dihydralazine became sensitive to acidic conditions. Hydrochlorothiazide was shown to be more sensitive to UV/Vis light and pH?>?4. Degradation of dihydralazine and hydrochlorothiazide followed first-order kinetics. The quickest degradation of dihydralazine was found to be in 1 M NaOH while of hydrochlorothiazide was in 1 M HCl (individual hydrochlorothiazide) or at pH 7–10 (hydrochlorothiazide in the mixture). A number of new degradation products were detected and some of them were identified by our LC-DAD and LC–MS methods. In the stressed individual samples, (phenylmethyl)hydrazine and 1,2,4-benzothiadiazine-7-sulfonamide 1,1-dioxide were observed for the first time. Interactions between dihydralazine and hydrochlorothiazide in the mixture were confirmed by additional degradation products, e.g., 2H-1,2,4-benzothiadiazine-7-sulfonamide 1,1,4-trioxide.     

Microcalorimetric analysis of methylcellulose influence on the hydration process of tricalcium aluminate,alite and their mixture

In the paper, the results of investigation concerning the influence of 0.3% addition of hydroxypropyl methylcellulose (MC) of 40 and 70 Pa s viscosity on the hydration process of main clinker phases C₃S and C₃A are presented. The course of hydration is documented using microcalorimetry, and formed phases were identified by XRD. The research indicated that methylcellulose inhibited the hydration process of clinker phases, analysed both, separately and in their mixture. Moreover, it was found that the presence of MC admixture also led to the reduction in calcium sulphate dihydrate reactivity in the system.     

Tunable dual-band liquid crystal based near-infrared perfect metamaterial absorber with high-loss metal

ABSTRACT

In this work, a tunable dual-band near-infrared perfect metamaterial absorber formed by combining a highly birefringent nematic liquid crystal with a nanoscale metamaterial cavity arranged in mirror symmetry is designed and numerically investigated. Electromagnetic simulations indicate that the absorbance greater than 99.4% may be achieved at 328 THz and 364 THz. Perfect absorbance results both form the use of highly lossy metal and the optimization of the metamaterial structure. In addition, absorbance of the metamaterial device can be substantially tuned both in terms of its magnitude and wavelength with the spectral tunability up to 8 THz by switching of liquid crystal alignment. The soft-matter-based metamaterial absorbers may pave a crucial role towards various active multifunctional systems working in the near-infrared range.     

SIMS accurate determination of matrix composition of topological crystalline insulator material Pb1 − xSnxSe

Substitutional alloy Pb_1 − xSn_xSe is a new class of electronic materials called topological crystalline insulators, which at the temperature range from 0 K to 300 K exhibit topological state at compositions in the range 0.18 < x < 0.40 (in the rock-salt structure). In this report, we present a secondary ion mass spectrometry (SIMS) analysis technique to provide accurate Pb and Sn composition based on the measurement of PbCs⁺ and SnCs⁺ cluster ions intensities. Studies of Pb_1 − xSn_xSe bulk samples with various values of x show that x/(1 − x) is linear in relation to the intensity ratio of PbCs⁺/SnCs⁺ over the range from x = 0.15 to x = 0.41. This technique allows us to obtain an accurate Sn content for multilayered heterostructures, quantum wells containing Pb_1 − xSn_xSe with different x values for each layer.     

Dilation theorems for positive definite operator kernels having majorants

Dilation theorems for Banach space valued stochastic processes and operator valued positive definite kernels are considered. It is shown, e.g., that a Banach space valued stochastic process X can be dilated to another process Y, if and only if the covariance kernel of Y is a majorant of the covariance kernel of X. Positive definite operator kernels having majorants of certain special type are characterized.     

Solid phase synthesis of two muramyl pentapeptide derivatives

Solid phase peptide synthesis (SPPS) of two selected muramyl pentapeptide derivatives is described. The simplicity of removing the protecting groups via one-step deprotection and cleavage from the resin is the biggest advantage of SPPS. Using this method, two muramyl pentapeptide derivatives, D-MurN₃-L-Ala-D-iGlu-L-Lys-D-Ala-D-Ser (5) and D-MurN₃-L-Ala-D-iGlu-L-Lys-D-Ala-D-Ala (6), were obtained. Their chemical structures were confirmed by high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy. To determine the absolute configuration of the carbon atom in the side chain of the muramic acid derivative, single-crystal X-ray diffraction measurements were recorded.