Sliding Wear of Al2O3–SiC–(Al,Si) Composites against a Steel Counterface

The sliding-wear behavior of Al₂O₃–SiC–Al composites prepared by melt oxidation against a steel counterface has been recorded in a pin-on-disk machine. At high speeds and pressures (10 m/s, 20 MPa), friction and wear appear to be principally controlled by the in-situ formation of an interfacial film that consists of a layer of Fe₃O₄. The formation of this film is examined as a function of sliding speed, lubrication, and composite microstructure. A model is proposed in which high surface temperatures cause the preferential extrusion of aluminum from the composite onto the pin/disk interface. This promotes the adhesive pickup of iron and its oxidation to form a stable tribologically beneficial layer of Fe₃O₄.     

Spectral (FT-IR,NMR) Analyses,Molecular Structures,and Chemical Bonding of Two Hexahydroacridine-1,8(2H,5H)-dione Derivatives: A Comparative Quantum Chemical Study

A comparative study on two hexahydroacridine-1,8(2H,5H)-dione deriv-atives namely, 9,10-bis(4-fluorophenyl)-3,3,6,6-tetramethyl-3,4,-6,7,9,10-hexahy-droacridine-1,8(2H,5H)-dione (FTHD) and 10-(4-fluorophenyl)-3,3,6,6-tetramethyl-9-(3,4,5-trimethoxyphenyl)-3,4,6,-7,9,10-hexahyd-roacridine-1,8(2H,5H)-dione (FTMPHD) has been performed. ¹H and ¹³C NMR spectra have been recorded in the CDCl₃ solvent. The equilibrium geometries of FTHD and FTMPHD have been determined and analyzed at DFT level employing B3PW91/6-311++G (d,p) method. The vibrational spectra of both the molecules are calculated and compared with the experimental FT-IR spectra. ¹H and ¹³C NMR spectra have been calculated by using the gauge-independent atomic orbital (GIAO) method. The calculated spectra have been found to be in good agreement with the experimental spectra. The quantum theory of atoms-in-molecule (QTAIM) approach is employed to study various intramolecular interactions within these molecules. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and the molecular electrostatic potential (MESP) surfaces have been constructed and analyzed. Various electronic as well as thermodynamic parameters have been reported.     

Ethylene-propylene diene monomer-based polymer composite for attenuation of high energy radiations

Radiation shielding composites of ethylene-propylene diene monomer (EPDM), reinforced with tungsten (W) and barium sulphate (BaSO₄) in different filler weight (wt%) were synthesized. The effects of W and BaSO₄ on gamma and neutron attenuation properties of the composites were studied by experimental methods using ¹³⁷Cs, ⁶⁰Co and ²⁵²Cf radioactive sources. EPDM composites with W and BaSO₄ fillers were also investigated for filler dispersion using scanning electron microscopy and X-ray radiograph. The experimental results revealed that the incorporation of W and BaSO₄ significantly improved the radiation attenuation properties of the EPDM composites. It was observed that the attenuation properties of the composite material increases with higher concentration of the filler. The half-value layer (HVL), tenth value layer thickness and relaxation length of the composites were found to decrease with increasing concentration of the filler. The results also showed that the attenuation behaviour of 50 wt% BaSO₄ filled polymer composite is comparable to that of the composite with 25 wt% W. The developed composite with 75 wt% W filler exhibited the maximum radiation attenuation with lowest HVL thicknesses.     

Combinatory Effects of Cerium Dioxide Nanoparticles and Acetaminophen on the Liver—A Case Study of Low-Dose Interactions in Human HuH-7 Cells

The interactions between pharmaceuticals and nanomaterials and its potentially resulting toxicological effects in living systems are only insufficiently investigated. In this study, two model compounds, acetaminophen, a pharmaceutical, and cerium dioxide, a manufactured nanomaterial, were investigated in combination and individually. Upon inhalation, cerium dioxide nanomaterials were shown to systemically translocate into other organs, such as the liver. Therefore we picked the human liver cell line HuH-7 cells as an in vitro system to investigate liver toxicity. Possible synergistic or antagonistic metabolic changes after co-exposure scenarios were investigated. Toxicological data of the water soluble tetrazolium (WST-1) assay for cell proliferation and genotoxicity assessment using the Comet assay were combined with an untargeted as well as a targeted lipidomics approach. We found an attenuated cytotoxicity and an altered metabolic profile in co-exposure experiments with cerium dioxide, indicating an interaction of both compounds at these endpoints. Single exposure against cerium dioxide showed a genotoxic effect in the Comet assay. Conversely, acetaminophen exhibited no genotoxic effect. Comet assay data do not indicate an enhancement of genotoxicity after co-exposure. The results obtained in this study highlight the advantage of investigating co-exposure scenarios, especially for bioactive substances.     

Intramuscular EMG classifier for detecting myopathy and neuropathy

This article presents an automatic diagnostic system to classify intramuscular electromyography (iEMG) signals, thereby detecting neuromuscular disorders. To this end, we tailored the center symmetric local binary pattern (CSLBP) to analyze one-dimensional ($1$-D) signals. In this approach, the $1$-D CSLBP feature extracted from a decimated iEMG signal is fed to a combination of classifiers, which in turn assigns a set of labels to the signal, and ultimately the signal category is determined by the Boyer-Moore majority voting (BMMV) algorithm. The proposed framework was investigated with a benchmark iEMG dataset that contains signals recorded from three different muscles: biceps brachii (BB), deltoideus (DE), and vastus medialis (VM). In a repeated $10$-fold cross-validation, CSLBP-Combined-Classifiers-BMMV (CSLBP-CC-BMMV) achieved an average classification accuracy of $92.80$%, $94.25$%, and $93.71$% for the iEMG signals recorded from BB, DE, and VM muscle, respectively. Interestingly, the performance of CSLBP-CC-BMMV surpassed the other published approaches and ensemble learning methods that are akin to our scheme in terms of classification accuracy and computational time.