Synthesis,characterization, crystal structure,and antimicrobial studies of 2-morpholinoethyl-substituted benzimidazolium salts and their silver(I)-N-heterocyclic carbene complexes

Research on Chemical Intermediates - This article describes synthesis of N-morpholinoethylbenzimidazole (1), 2-morpholinoethyl-substituted benzimidazolium salts (NHC precursors, 2a–c), and...     

In vitro swelling studies in simulated physiological solutions and biocompatibility of NIPAM-based hydrogels with some biochemical parameters of human sera

In modern medicine, commonly used biomaterials originating from metals, ceramics and polymers have shown biocompatibility with blood, tissues, cells, etc., in the human body. Polymeric biomaterials are usually understood as polymeric materials and articles made from them which are used in medicine, biotechnology biomedicine, bioengineering, pharmaceutical, veterinary, food industry, agriculture and related fields. In this in vitro study, swellings and the biocompatibility of environmentally sensitive N-isopropyl acrylamide-based (ES) hydrogels such as N-isopropyl acrylamide/acrylamide (ES/0), and N-isopropyl acrylamide/acrylamide/ carboxylic acids (ES/XAc) prepared by free radical polymerization in aqueous solutions has been investigated. Selected carboxylic acids for this study were acrylic, methacrylic, crotonic, itaconic, maleic, mesaconic and aconitic acid. The equilibrium swelling of the hydrogels are investigated in simulated physiological fluids or crystalloid solutions such as HCl-KCl buffer (pH = 1.1), universal buffer (pH = 5.5), phosphate buffer (pH = 7.4), urea, isotonic NaCl, isotonic KCl, 5% dextrose, 5% dextrose+isotonic NaCl, Ringer's lactate, human blood serum and human serum albumin solution at 37°C. For the analysis of biocompatibility, ES hydrogels are incubated in 5 different human sera and their biocompatibilities with some biochemical parameters have been investigated for 24 h at 37°C. No significant differences in values before and after the test procedures have been found. It is therefore concluded that environmentally sensitive N-isopropyl acrylamide-based hydrogels are biocompatible for biochemical parameters of human sera.     

Synthesis and characterization of poly(3-thiophene acetic acid)/Fe3O4 nanocomposite

Poly(3-thiophene acetic acid)/Fe₃O₄ nanocomposite is synthesized by the precipitation of Fe₃O₄ in the presence of poly(3-thiophene acetic acid) (P3TAA). Structural, surface, morphological, thermal properties and conductivity characterization/evaluation of the nanocomposite were performed by XRD, FT-IR, TEM, TGA, and conductivity measurements, respectively. The capping of P3TAA around Fe₃O₄ nanoparticles was confirmed by FT-IR spectroscopy, the interaction being via bridging oxygens of the carboxylate and the nanoparticle surface through bidentate binding. The crystallite and particle size were obtained as 9 ± 2 nm and 11 ± 1 nm from XRD line profile fitting and TEM image analysis, respectively, which reveal nearly single crystalline nature of Fe₃O₄ nanoparticles. Magnetization measurements reveal that P3TAA coated magnetite particles do not saturate at higher fields. There is no coercivity and remanence revealing superparamagnetic character. Magnetic particle size calculated from the theoretical fitting as 9.1 nm which coincides the values determined from TEM micrographs and XRD line profile fitting. The comparison to the TEM particle size reveals slightly modified magnetically dead nanoparticle surface.     

Controlling of electronic parameters of GaAs Schottky diode by poly(3,4-ethylenedioxithiophene)-block-poly(ethylene glycol) organic interlayer

The electronic properties of metal-organic semiconductor-inorganic semiconductor structure between GaAs and poly(3,4-ethylenedioxithiophene)-block-poly(ethylene glycol) organic film have been investigated via current-voltage and capacitance-voltage methods. The Au/PEDOT/n-GaAs contact exhibits a rectification behavior with the barrier height of 0.69 eV and ideality factor value of 3.94. The barrier height of the studied diode (0.67 eV) is lower than that of Ni/n-GaAs/In (0.85 eV) and Au/n-GaAs/In Schottky diodes. The decrease in barrier height of Au/n-GaAs/In Schottky diode is likely to be due to the variation in the space charge region in the GaAs. The obtained results indicate that control of the interfacial potential barrier for metal/n-GaAs diode was achieved using thin interlayer of the poly(3,4-ethylenedioxithiophene)-block-poly(ethylene glycol).     

Investigation of gf0ργ and coupling constants in light cone sum rules

We present a calculation of the coupling constant of f₀→ργ and a₀→ργ decays from the point of view of the light cone QCD sum rules. We estimate the coupling constants g_f0ργ, which are an essential ingredient in the analysis of physical processes involving the isoscalar f₀(980) and the isovector a₀(980) mesons. PACS 12.38.Lg, 13.40.Hq, 14.40.AqAn erratum to this article can be found at     

Trapping centers in undoped GaS layered single crystals

Nominally undoped p-GaS layered single crystals were grown using the Bridgman technique. Thermally stimulated current measurements in the temperature range 10–300 K were performed at a heating rate of 0.10 K/s. The analysis of the data revealed six trap levels at 0.05, 0.06, 0.12, 0.63, 0.71, and 0.75 eV. The calculations for these traps yielded 1.2×10^-21, 2.9×10^-23, 2.4×10^-21, 8.0×10^-9, 1.9×10^-9 and 4.3×10^-10 cm² for the capture cross sections and 1.6×10¹³, 5.0×10¹², 7.3×10¹², 1.2×10¹⁴, 8.9×10¹³ and 2.6×10¹³ cm^-3 for the concentrations, respectively. PACS 71.55.-i; 72.20.Jv; 72.80.Jc     

Numerical calculation of trapped magnetic field for square multiple bulk superconductors

In this work, the trapped magnetic field was calculated for square bulk superconductors using the sand-pile model and Biot–Savart law. The numerical simulation of the trapped magnetic field was performed varying the sample dimensions, distance between the sample surface and observation point. In addition the magnetic field characteristics of superconducting bulk arrangement in an array was determined. The trapped magnetic field was found to be depending on the sample dimensions and distance between the sample and observation point. It is observed that, when the distance from the surface is larger, the value of the trapped magnetic field decreases, but the variation of the trapped magnetic field becomes small due to averaging the distribution of the trapped magnetic field.     

On Approximation Properties of Generalized q-Bernstein Operators

In this study, we identify a generalization of q-Bernstein type operators and investigate approximation properties of a sequence of these operators . We estimate rate of approximation by modulus of continuity. We prove Voronovskaya type theorem for these operators.     

A comparative study on large scale kernelized support vector machines

Kernelized support vector machines (SVMs) belong to the most widely used classification methods. However, in contrast to linear SVMs, the computation time required to train such a machine becomes a bottleneck when facing large data sets. In order to mitigate this shortcoming of kernel SVMs, many approximate training algorithms were developed. While most of these methods claim to be much faster than the state-of-the-art solver LIBSVM, a thorough comparative study is missing. We aim to fill this gap. We choose several well-known approximate SVM solvers and compare their performance on a number of large benchmark data sets. Our focus is to analyze the trade-off between prediction error and runtime for different learning and accuracy parameter settings. This includes simple subsampling of the data, the poor-man’s approach to handling large scale problems. We employ model-based multi-objective optimization, which allows us to tune the parameters of learning machine and solver over the full range of accuracy/runtime trade-offs. We analyze (differences between) solvers by studying and comparing the Pareto fronts formed by the two objectives classification error and training time. Unsurprisingly, given more runtime most solvers are able to find more accurate solutions, i.e., achieve a higher prediction accuracy. It turns out that LIBSVM with subsampling of the data is a strong baseline. Some solvers systematically outperform others, which allows us to give concrete recommendations of when to use which solver.