High-performance nanocomposites based on polyetherketones

Polyetherketones, PEKs, are an important family of high-performance thermoplastic materials that display a unique combination of toughness, stiffness, thermooxidative stability, chemical and solvent resistance, flame retardancy, and retention of physical properties at high temperatures. A relevant step forward in the development of these materials has been the recent incorporation of nanofillers to extend their utility in advanced technological applications. This review provides an extensive overview of the research on PEK-based nanocomposites with a special emphasis on both carbon-based nanofillers, such as nanotubes or nanofibers, and inorganic nanoparticles. Nanocomposites can be fabricated by simple, low-cost conventional techniques such as extrusion and compression molding, generally combined with pre-processing stages involving mechanochemical treatments in organic solvents. Different strategies employed to efficiently incorporate carbon nanofillers into these matrices, including polymer functionalization, covalent grafting and nanofiller wrapping in compatibilizing systems are described. The analysis of the influence of the preparation and processing conditions as well as the nanofiller type, attributes and loading on the structure and properties of the resulting materials is also considered. Composites incorporating carbon nanofillers display remarkably improved thermal stability, electrical and thermal conductivity as well as mechanical property enhancements compared to the neat polymers. On the other hand, the incorporation of inorganic nanoparticles such as WS₂, SiO₂ or Al₂O₃ significantly enhances the tribological properties of the matrix, mainly the coefficient of friction and wear resistance. Finally, current and potential applications of these multifunctional nanocomposite materials in fields such as medicine, telecommunications, electronics, aerospace, automobile and chemical industries are described.     

N-(Anilinoethyl)amide Melatonergic Ligands with Improved Water Solubility and Metabolic Stability

The MT₂-selective melatonin receptor ligand UCM765 (N-(2-((3-methoxyphenyl)(phenyl)amino)ethyl)acetamide), showed interesting sleep inducing, analgesic and anxiolytic properties in rodents, but suffers from low water solubility and modest metabolic stability. To overcome these limitations, different strategies were investigated, including modification of metabolically liable sites, introduction of hydrophilic substituents and design of more basic derivatives. Thermodynamic solubility, microsomal stability and lipophilicity of new compounds were experimentally evaluated, together with their MT₁ and MT₂ binding affinities. Introduction of a m-hydroxymethyl substituent on the phenyl ring of UCM765 and replacement of the replacement of the N,N-diphenyl-amino scaffold with a N-methyl-N-phenyl-amino one led to highly soluble compounds with good microsomal stability and receptor binding affinity. Docking studies into the receptor crystal structure provided a rationale for their binding affinity. Pharmacokinetic characterization in rats highlighted higher plasma concentrations for the N-methyl-N-phenyl-amino derivative, consistent with its improved microsomal stability and makes this compound worthy of consideration for further pharmacological investigation.     

Aerobic Exercise Ameliorates Cancer Cachexia-Induced Muscle Wasting through Adiponectin Signaling

Cachexia is a multifactorial syndrome characterized by muscle loss that cannot be reversed by conventional nutritional support. To uncover the molecular basis underlying the onset of cancer cachectic muscle wasting and establish an effective intervention against muscle loss, we used a cancer cachectic mouse model and examined the effects of aerobic exercise. Aerobic exercise successfully suppressed muscle atrophy and activated adiponectin signaling. Next, a cellular model for cancer cachectic muscle atrophy using C2C12 myotubes was prepared by treating myotubes with a conditioned medium from a culture of colon-26 cancer cells. Treatment of the atrophic myotubes with recombinant adiponectin was protective against the thinning of cells through the increased production of p-mTOR and suppression of LC3-II. Altogether, these findings suggest that the activation of adiponectin signaling could be part of the molecular mechanisms by which aerobic exercise ameliorates cancer cachexia-induced muscle wasting.     

Optimized laser processing of calibration blocks for grinding burn detection with Barkhausen noise

Calibration samples for the Barkhausen noise (BN) method were produced with laser processing. A planet gear wheel used for production quality control was subjected to laser irradiation to verify the BN sensor output. Different samples were found to respond similarly to the laser processing although the laser parameters needed to be adjusted for different surface qualities separately. The surface optimization for laser processing was studied with different surface qualities of samples. The ground surface was compared with a sandblasted and vibratory ground surface. The ground and sandblasted surfaces were both amenable to the laser processing whereas the vibratory grinding process created inhomogeneous surfaces for laser beam absorption. Laser processing was found to produce uniform changes in the residual stress values in two perpendicular measuring directions. The root mean square value of the BN voltage signal exhibited linear correlations with the values of the residual stress and surface hardness.     

Towards Automated Binding Affinity Prediction Using an Iterative Linear Interaction Energy Approach

Binding affinity prediction of potential drugs to target and off-target proteins is an essential asset in drug development. These predictions require the calculation of binding free energies. In such calculations, it is a major challenge to properly account for both the dynamic nature of the protein and the possible variety of ligand-binding orientations, while keeping computational costs tractable. Recently, an iterative Linear Interaction Energy (LIE) approach was introduced, in which results from multiple simulations of a protein-ligand complex are combined into a single binding free energy using a Boltzmann weighting-based scheme. This method was shown to reach experimental accuracy for flexible proteins while retaining the computational efficiency of the general LIE approach. Here, we show that the iterative LIE approach can be used to predict binding affinities in an automated way. A workflow was designed using preselected protein conformations, automated ligand docking and clustering, and a (semi-)automated molecular dynamics simulation setup. We show that using this workflow, binding affinities of aryloxypropanolamines to the malleable Cytochrome P450 2D6 enzyme can be predicted without a priori knowledge of dominant protein-ligand conformations. In addition, we provide an outlook for an approach to assess the quality of the LIE predictions, based on simulation outcomes only.     

Deep-level Transient Spectroscopy of GaAs/AlGaAs Multi-Quantum Wells Grown on (100) and (311)B GaAs Substrates

Si-doped GaAs/AlGaAs multi-quantum wells structures grown by molecular beam epitaxy on (100) and (311)B GaAs substrates have been studied by using conventional deep-level transient spectroscopy (DLTS) and high-resolution Laplace DLTS techniques. One dominant electron-emitting level is observed in the quantum wells structure grown on (100) plane whose activation energy varies from 0.47 to 1.3 eV as junction electric field varies from zero field (edge of the depletion region) to 4.7 × 10⁶ V/m. Two defect states with activation energies of 0.24 and 0.80 eV are detected in the structures grown on (311)B plane. The E_c-0.24 eV trap shows that its capture cross-section is strongly temperature dependent, whilst the other two traps show no such dependence. The value of the capture barrier energy of the trap at E_c-0.24 eV is 0.39 eV.     

Optimal design of stepped spillways using the HBMO algorithm

Studies on stepped spillways as flood energy dissipators have been conducted to understand the hydraulics on the stepped face of roller-compacted concrete dams as well as overlays of embankment dams. Significant energy losses occur along the stepped chute so that the energy dissipation structure becomes smaller and more economic. In addition, considering the design discharge, downstream face slope, height of spillway, different combinations of spillway width and number of spillway steps may lead to different head losses. In each feasible combination, the remaining head after the steps should be dissipated by downstream energy dissipators. Design and construction of spillways and energy disspators are very cost-consuming and build up a major part of the dam's construction expenses. Thus, the cost of a financially viable stepped spillway project that consists of the steps’ cost and downstream dissipator's cost should be minimised. In this paper, the honey-bee mating optimisation (HBMO) algorithm is used to determine the best combination of design variables so as to minimise the total cost of both spillway chute and stilling basin. Results are compared with those previously obtained by genetic algorithm (GA) and show the promising potential of the HBMO algorithm in this field of application.     

Effect of CO2 Exposure on the Chemical Stability and Mechanical Properties of BaZrO3‐Ceramics

The reactivity of BaZrO₃ with CO₂ has been addressed as one of the major challenges with BaZrO₃‐based electrolytes in protonic ceramic fuel cells. Here, we present a study of the effect of CO₂ exposure on BaZrO₃‐materials at elevated temperatures. Dense BaZr_1?xY_xO_3?x/2 (x = 0, 0.05, 0.1, 0.2) and BaCe_0.2Zr_0.7Y_0.1O_2.95 ceramics were prepared by sintering of powder prepared by spray pyrolysis. The Vickers indentation method was used to determine the hardness and estimate the fracture toughness of pristine materials as well as the corresponding materials exposed to CO₂. Formation of BaCO₃ on the surface of exposed ceramics was confirmed by X‐ray diffraction and electron microcopy. The reaction resulted in formation of Ba‐deficient perovskite at the exposed surface. The reaction with CO₂ was most pronounced at 650°C compared to the other temperatures applied in the study. The reactivity was also shown to depend on the Y‐content and the grain size and was most pronounced for BaZr_0.9Y_0.1O_2.95. The reaction with CO₂ was observed to have a profound effect on the fracture toughness of the ceramics, demonstrating a depression of the mechanical stability of the materials. The results are discussed with respect to the chemical and mechanical stability of BaZrO₃ materials, with particular emphasis on the composition and grain size.