Iron exchanged ZSM-5 and Y zeolites calcined at different temperatures: activity in N2O decomposition

ZSM-5 and Y zeolites were modified with iron by an ion-exchange method and then calcined at 773, 873, 973 and 1,073 K. The obtained materials were characterized with respect to textural parameters (low-temperature N₂ sorption), structure (X-ray diffraction, UV–vis–DRS), redox properties (H₂-temperature programmed desorption, TPD) and surface acidity (NH₃-TPD). The obtained results have shown that the structure of zeolites influenced form, aggregation and content of the introduced iron species. In case of the FAU type structure characterized by wide pores (max. ring size, T-atoms—12) mainly iron in form of mononuclear Fe³⁺ cations and Fe _x ³⁺ O_y oligonuclear clustered species was found. On the other hand for the MFI type structure characterized by smaller pores (max. ring size, T-atoms—10) significant contribution of iron in the form of bulky Fe₂O₃ clusters located possibly on the outer surface of ZSM-5 was detected. Such significant differences in distribution of iron species is probably related to various mobility of iron species in the pore systems of both zeolites. The obtained materials were tested as catalysts in the process of N₂O decomposition. Calcination of zeolites at different temperatures influenced neither the properties nor the activity of the obtained catalysts.     

Catalytic reduction of N2O by ethylbenzene over novel hydrotalcite-derived Mg–Cr–Fe–O as an alternative route for simultaneous N2O abatement and styrene production

New hydrotalcite-like materials containing magnesium, chromium, and/or iron were synthesized by the coprecipitation method and then thermally transformed into mixed metal oxides. The obtained catalysts were characterized with respect to chemical composition (XRF), structural (XRD, Mössbauer spectroscopy) and textural (BET) properties. The catalytic performance of the hydrotalcite-derived oxides was tested in the N₂O decomposition and the N₂O reduction by ethylbenzene. An influence of N₂O/ethylbenzene molar ratio on the process selectivity was studied. The relationship between catalytic performance and structure of catalysts was discussed.     

Content driven QoE assessment for video frame rate and frame resolution reduction

Video bit rate reduction is very important for all video streaming applications. One possibility involves quantization domain and the majority of the work devoted to bit rate reduction focuses on this aspect only. The other possibility is to modify a video in time or space domain i.e. change the frames per second FPS rate or frame resolution FR. In this paper we present two no reference metrics mapping FPS rate and FR into MOS (Mean Opinion Scale). The performance of both models is significantly improved by incorporating content characteristics such as spatial information SI and temporal information TI. The impact on Quality of Experience (QoE) of both content characteristics is discussed with relation to the FPS rate and FR changes and general conclusions are drawn. The models were estimated and verified upon results of subjective experiments performed using video sequences of diverse spatial and temporal variability. The considered FPS rate was changed from 5 to 30 and the considered FR was changed from SQCIF to SD.     

Spectroscopic study of a novel bis(heptamethine cyanine) dye and its interaction with human serum albumin

A newly synthesized near-infrared (NIR) bis(heptamethine cyanine) dye 7 was evaluated for its utility as a non-covalent label for proteins. This dye forms inter- and intramolecular H-aggregates in polar solvents, even at very low concentrations. The intramolecular dimeric form of the dye can be described as a clam-shell complex with two interacting hydrophobic carbocyanine moieties. In this intramolecular H-aggregate, the chromophore has a low extinction coefficient and low fluorescence quantum yield. In aqueous solution, in the absence of human serum albumin (HSA), dye 7 has characteristic absorption bands at 792 and 435 nm, and its fluorescent emission is significantly diminished in comparison to that in methanol or when compared to its monomeric equivalent 5. Dye 7 seems to be more advantageous than its monomeric counterpart 5 as a non-covalent label for biomolecules. Upon addition of HSA, the H and D bands are decreased and the monomeric band is increased, with concomitant increase in fluorescence intensity, suggesting that clam-shell H-aggregates open up in the complex with HSA. The binding stoichiometry is 1:1. The main advantage of this dimeric dye as a non-covalent label is that the free dye has negligible fluorescence.     

Numerical stress and crack initiation analysis of the compressor blades after foreign object damage subjected to high-cycle fatigue

This paper presents results of the complex stress and crack initiation analysis of the PZL-10 W turbo-engine compressor blade subjected to high cycle fatigue (HCF). A nonlinear finite element method was utilized to determine the stress state of the blade during the first mode of transverse vibration. In this analysis, the numerical models without defects and also with V-notches were defined. The quality of the numerical solution was checked by the convergence analysis. Obtained results were next used as an input data into crack initiation (ε–N) analyzes performed for the load time history equivalent to one cycle of the transverse vibration. In the fatigue analysis the different methods such as: Neuber elastic–plastic strain correction, linear damage summation and Palmgreen–Miner rule were utilized. As a result of ε–N analysis, the number of load cycles to the first fatigue crack appearing in the compressor blades was obtained. Moreover, the influence of the blade vibration amplitude on the number of cycles to the crack initiation was analyzed. Values of the fatigue properties of the blade material according to Baumel–Seeger and Muralidharan methods were calculated. The influence of both the notch radius and values of the UTS of the blade material on the fatigue behavior of the structure was also considered. In the last part of work, the finite element results were compared with the results of an experimental vibration HCF tests performed for the compressor blades.     

Vermiculites intercalated with Al2O3 pillars and modified with transition metals as catalysts of DeNOx process

Vermiculites intercalated with alumina pillars and modified with transition metals (Cu, Fe) were studied as catalysts of selective reduction of NO with ammonia. Prior to the pillaring process, a raw vermiculite was treated with a solution of nitric acid and then citric or oxalic acid in order to reduce the overall charge of layers. This modification was necessary for a successful pillaring of the clay. Transition metals (Fe, Cu) were deposited on the surface of the modified vermiculites by an ion-exchange method. The obtained samples were characterized with respect to composition (EPMA), structure (XRD), texture (BET) and chemical nature of deposited transition metal species (UV–vis–DRS). The vermiculite based materials have been found to be active and selective catalysts of the DeNOx process. The Cu-containing samples were catalytically active at lower temperatures than the pillared clays modified with iron. A side reaction of ammonia oxidation by oxygen decreased the effectiveness of the DeNOx process in the high temperature range.     

Structure and cyclic oxidation resistance of Pt, Pt/Pd-modified and simple aluminide coatings on CMSX-4 superalloy

The coatings were prepared by the means of Pt and Pt/Pd galvanizing, followed by vapor phase aluminizing at 1050 °C. Microstructural and phase analysis revealed that all the investigated coatings consisted mainly of β-NiAl phase, however the Pt-modified aluminide coating also contained PtAl₂ phase and pure platinum precipitates. The cross-sectional microstructure of the coatings was zonal and composed of β-NiAl phase zone and the diffusion zone. The Pt modified aluminide coating's cross-section also incorporated an outermost zone consisting of β-NiAl and PtAl₂ phases. The concentration profiles proved that both Pt and Pd contents decrease gradually inwards the modified coatings. Cyclic oxidation tests at 1100 °C proved that Pt/Pd-modified aluminide coatings exhibit the best performance under cyclic conditions. The analysis of oxidation kinetics curves showed that the course of simple aluminide coating's oxidation is slightly different from that of Pt- and Pt/Pd-modified aluminide coatings.     

Automated qualitative assessment of multi-modal distortions in digital images based on GLZ

This paper introduces a novel approach to a qualitative assessment of images affected by multi-modal distortions. The idea is to assess the image quality perceived by an end user in an automatic way in order to avoid the usual time-consuming, costly and non-repeatable method of collecting subjective scores during a psycho-physical experiment. This is achieved by computing quantitative image distortions and mapping results on qualitative scores. Useful mapping models have been proposed and constructed using the generalised linear model (GLZ), which is a generalisation of the least squares regression in statistics for ordinal data. Overall qualitative image distortion is computed based on partial quantitative distortions from component algorithms operating on specified image features. Seven such algorithms are applied to successfully analyse the seven image distortions in relation to the original image. A survey of over 12,000 subjective quality scores has been carried out in order to determine the influence of these features on the perceived image quality. The results of quantitative assessments are mapped on the surveyed scores to obtain an overall quality score of the image. The proposed models have been validated in order to prove that the above technique can be applied to automatic image quality assessment.     

Induction of Oxidative Stress in SH-SY5Y Cells by Overexpression of hTau40 and Its Mitigation by Redox-Active Nanoparticles

Abnormally phosphorylated tau protein is the principal component of neurofibrillary tangles, accumulating in the brain in many neurodegenerative diseases, including Alzheimer’s disease. The aim of this study was to examine whether overexpression of tau protein leads to changes in the redox status of human neuroblastoma SH-SY5Y cells. The level of reactive oxygen species (ROS) was elevated in tau-overexpressing cells (TAU cells) as compared with cells transfected with the empty vector (EP cells). The level of glutathione was increased in TAU cells, apparently due to overproduction as an adaptation to oxidative stress. The TAU cells had elevated mitochondrial mass. They were more sensitive to 6-hydroxydopamine, delphinidin, 4-amino-TEMPO, and nitroxide-containing nanoparticles (NPs) compared to EP controls. These results indicate that overexpression of the tau protein imposes oxidative stress on the cells. The nitroxide 4-amino-TEMPO and nitroxide-containing nanoparticles (NPs) mitigated oxidative stress in TAU cells, decreasing the level of ROS. Nitroxide-containing nanoparticles lowered the level of lipid peroxidation in both TAU and EP cells, suggesting that nitroxides and NPs may mitigate tau-protein-induced oxidative stress.     

3D supramolecular network constructed by intermolecular interactions in mixed ligand complex of zinc

New complex [Zn(quin-2-c)₂(Him)₂] (quin-2-c = quinoline-2-carboxylate ion, Him = imidazole) was synthesized by self assembly and its structure was determined by X-ray analysis. The compound crystallizes in P21/c space group. Four independent molecules of complex are present in the structure. Strong hydrogen bonds create three different 1D chains which are collected in two different layers. The alternately packed layers form the 3D supramolecular structure. The interchain and interlayer contacts are of the C–HO, ππ and C–Hπ type. The influence of strong hydrogen bond on the vibrational characteristics of the monodentately coordinated carboxylate group in zinc complexes with quin-2-c ion is discussed.