Furfural Oxidation with Hydrogen Peroxide Over ZSM-5 Based Micro-Mesoporous Aluminosilicates

Micro-mesoporous aluminosilicates based on ZSM-5 zeolite, obtained by a dual template method, as well as in the presence of a dual-functional template (i.e. a Gemini-type surfactant), were tested in the oxidation of furfural with hydrogen peroxide. Even substantial changes in acidity and porosity of the catalysts result in minor variations of selectivity towards the desired products. Application of the synthesized zeolite-based materials in the oxidation of furfural with hydrogen peroxide leads to formation of 2(5H)-furanone (yield up to 28.5%) and succinic acid (up to 19.5%) as the main C4 reaction products. The kinetic model developed previously to treat the results for oxidation of furfural over sulfated zirconia was able to describe the data also for micro-mesoporous aluminosilicates.

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Polymer matrices on the basis of polyacrylamide and β-cyclodextrin-containing pseudorotaxane for prolonged drug release: Synthesis and properties

Polymer cross-linked matrices based on polyacrylamide (PAA) and β-cyclodextrin-pseudorotaxane have been designed. The structure and properties of the objects synthesized were confirmed and studied by a series of methods, involving ultraviolet-, Fourier transform infrared-spectroscopy, thermal mass spectrometry, DSC, X-ray diffraction analysis (WAXS and SAXS). Desorption kinetics (especially significant slowing of desorption process) of some drugs, like metoprolol succinate and loratadine from obtained polymer matrices is shown to be optimal with 10 wt% β-CD-pseudorotaxane in their structure.     

Single-electron transfer living radical copolymerization of SWCNT-g-PMMA via graft from approach

The sidewall functionalization of single-walled carbon nanotubes (SWCNTs) was established by poly (methyl methacrylate) (PMMA) using controlled radical polymerization (CRP) method. A bromide functionalized SWCNT (SWCNT-Br) has been used as an initiator for the synthesis of SWCNT-graft-PMMA (SWCNT-g-PMMA). The efficiency of the sacrificial initiator (S) was monitored during the polymerization process. The obtained polymers possess a uniform distribution of molecular weight with a lower polydispersity index of 1.36. The SWCNTs-based initiator acts as an efficient medium for the controlled growth of polymer on the SWCNTs surfaces. The presence of bimodal gel permeation chromatographic (GPC) curve for the SWCNT-g-PMMA(S) obtained through sacrificial initiator (S) confirms uncontrolled behavior. However, the clear sharp peak for SWCNT-g-PMMA obtained without sacrificial initiator shows its well-controlled process of polymerization, which acts as a mimic to bone cement. The efficiency of the functionalization of SWCNT and the controlled formation of SWCNT-g-PMMA composites were characterized by TGA, Raman, TEM, NMR, XPS and dispersion measurements.     

Temperature‐Dependent Exciton and Trap‐Related Photoluminescence of CdTe Quantum Dots Embedded in a NaCl Matrix: Implication in Thermometry

Temperature‐dependent optical studies of semiconductor quantum dots (QDs) are fundamentally important for a variety of sensing and imaging applications. The steady‐state and time‐resolved photoluminescence properties of CdTe QDs in the size range from 2.3 to 3.1 nm embedded into a protective matrix of NaCl are studied as a function of temperature from 80 to 360 K. The temperature coefficient is found to be strongly dependent on QD size, with the highest sensitivity obtained for the smallest size of QDs. The emission from solid‐state CdTe QD‐based powders is maintained with high color purity over a wide range of temperatures. Photoluminescence lifetime data suggest that temperature dependence of the intrinsic radiative lifetime in CdTe QDs is rather weak, and it is mostly the temperature‐dependent nonradiative decay of CdTe QDs which is responsible for the thermal quenching of photoluminescence intensity. By virtue of the temperature‐dependent photoluminescence behavior, high color purity, photostability, and high photoluminescence quantum yield (26%–37% in the solid state), CdTe QDs embedded in NaCl matrices are useful solid‐state probes for thermal imaging and sensing over a wide range of temperatures within a number of detection schemes and outstanding sensitivity, such as luminescence thermochromic imaging, ratiometric luminescence, and luminescence lifetime thermal sensing.     

Correlation Between <Emphasis Type="Italic">T</Emphasis><Subscript>c</Subscript> and Hyperfine Parameters of Fe in Layered Chalcogenide Superconductors

Although pairing mechanism in unconventional superconductors is still an open question, the density of states at the Fermi level is considered to be one of the factors affecting the superconducting transition temperature. Herein, we report on ⁵⁷Fe-Mössbauer studies of β-FeSe, FeSe _0.5Te _0.5, and Rb _0.8Fe _1.6Se ₂ superconductors as well as two intercalate products consisting of FeSe layers and a lithium-containing molecular spacer in between. In these materials, the hyperfine parameters of ⁵⁷Fe are directly related to the 3d-electron density on Fe atoms and show strong correlation with superconducting properties.     

Spectroscopic analysis of the arc plasma of underwater wet flux-cored arc welding

Experiments in air and under water (0.4 m depth) were conducted and the spectrum signals collected. The width of the weld under water was about two-thirds of the width in air, suggesting that the arc plasma was compressed by the water environment. The two sets of spectrum signals were largely similar except for the ultraviolet spectrum, from where the environmental effects were inferred. The analysis identified a unique peak at 656.2793 nm in the underwater spectrum, consistent with H atomic transitions, suggesting that H atoms become involved, although without affecting the overall spectral similarity of the two environments. In either environment the arc plasma was mainly composed of self-shielding gas and evaporated metals, with only minor effects stemming from the interaction with water.     

Hardware implementation of radial-basis neural networks with Gaussian activation functions on FPGA

Neural Computing and Applications - This article introduces a method for realizing the Gaussian activation function of radial-basis (RBF) neural networks with their hardware implementation on...     

A Neumann series of Bessel functions representation for solutions of Sturm–Liouville equations

A Neumann series of Bessel functions (NSBF) representation for solutions of Sturm–Liouville equations and for their derivatives is obtained. The representation possesses an attractive feature for applications: for all real values of the spectral parameter \(\omega \) the estimate of the difference between the exact solution and the approximate one (the truncated NSBF) depends on N (the truncation parameter) and the coefficients of the equation and does not depend on \(\omega \). A similar result is valid when \(\omega \in {\mathbb {C}}\) belongs to a strip \(\left| \hbox {Im }\omega \right| <C\). This feature makes the NSBF representation especially useful for applications requiring computation of solutions for large intervals of \(\omega \). Error and decay rate estimates are obtained. An algorithm for solving initial value, boundary value or spectral problems for the Sturm–Liouville equation is developed and illustrated on a test problem.