Iron oxides are a ubiquitous class of magnetic materials, holding the promise of spintronic devices and magnetic hyperthermia based on their tunable magnetic and electric conducting properties. ...However, their high sensitivity towards oxidation/reduction environments makes them difficult to control in a reversible and scalable manner. Here we demonstrate two different approaches for reduction of antiferromagnetic insulator α-Fe
2
O
3
thin films into ferrimagnetic conductor Fe
3
O
4
thin films. The wet H
2
reduction process is more efficient than the vacuum and inert gas atmosphere when producing nanocrystalline Fe
3
O
4
thin films. We measure low-temperature physical properties and find that the wet H
2
reduction process drives pronounced changes in magnetic anisotropy, Verwey transition, and surface spin canting-induced exchange bias in Fe
3
O
4
thin films. We also explain how phase formation in nanocrystalline iron oxide thin films is different from their bulk equilibrium phase diagram.
Biodiesel was produced through transesterification of refined cotton seed oil with methanol and potassium hydroxide (KOH) as a catalyst using batch mode. The physicochemical properties of cotton seed ...oil and biodiesel as an alternative fuel for diesel engine was characterized through ASTM standards for fuel tests. The functional groups of the biodiesel were investigated using Fourier transform infrared spectroscopy. Influence of key parameters like reaction temperature, reaction time, catalyst concentration and methanol/oil molar ratio were determined using batch mode. These process parameters were optimized using response surface methodology (RSM) and analysis of variance (ANOVA). The significance of the different process parameters and their combined effects on the transesterification efficiency were established through a full factorial central composite design. The results obtained are in good agreement with published data for other vegetable oil biodiesel as well as various international standards for biodiesel fuel. An optimum yield of 96% was achieved with optimal conditions of methanol/oil molar ratio, 6:1; temperature, 55°C; time, 60min; and catalyst concentration, 0.6%. This investigation has shown that cotton seed oil from Nigeria can be used to produce biodiesel.
The purpose of present study was to separate novel antioxidant peptides from duck breast protein hydrolysates and characterize their primary sequence, secondary and tertiary structure using ...Nano-LC-ESI-LTQ-Orbitrap MS/MS, NICOLET IS10 FT-IR and PEPstr server, respectively. Results indicated that peptide fraction P1 via gel filtration chromatography displayed high DPPH radical quenching effect and reducing power. Fraction P1 was further purified chromatographically and sequenced as eleven novel antioxidant peptides, in which AGPSIVH possessed the best DPPH inhibition, and LLCVAV exhibited active reducing power, whereas FLLPH and LLCVAV were effective ABTS•+ scavengers. IR study and PEPstr server prediction suggested that spatial structure could play an influential part in antioxidant capacity. Importantly, these peptides were predicted as non-toxic oxidative stress inhibitors, allowing their applications in functional foods.
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•Novel antioxidant peptide was prepared from duck breast protein hydrolysates.•Peptide was purified via ultrafiltration, gel chromatography and RP-HPLC.•Three novel potent antioxidant peptide AGPSIVH, FLLPH and LLCVAV were identified.•Spatial conformation also affected antioxidant potency beyond primary sequence.•AGPSIVH, FLLPH, LLCVAV had no toxic effects and possessed digestive resistances.
In recent times, glass materials appear to be strong candidates for radiation protection applications. In this study, a zinc-bismuth-barium-sodium-silicate (ZBBSS) glass system with a formulation of ...10ZnO – 20Bi2O3– 5BaO – 15Na2O – (50-x) SiO2– xPbO, x: 0, 5, 15 and 25 wt% was synthesized. The traditional melting technique (1325–1375 °C) enabled the synthesis of four different glass samples coded ZBBSS1 to ZBBSS4. Following synthesis, Archimedes' principle, XRD, FTIR, UV-Vis, and DSC techniques showed physical, structural, optical, and thermal property alterations as a function of PbO inclusion, while the triple methodology (experimental, theoretical, and simulation) revealed radiation attenuation aspects in a broader sense. According to the findings, ZBBSS1 had density of 3.1107 g/cm3 while the other samples had density values of 3.2285, 3.6053, and 4.0158 g/cm3 in respective order. The clear existence of non-crystalline structure for the ZBBSS glass series was reported. Similar vibrational modes were found for ZBBSS glass systems, and -OH, Si-OH, Si-O-Si, and Pb-O-Pb bonding types were assigned to peak formations. For determination of thermal properties, it was observed that Tg became lower, from 520.6 to 392.4 °C, in parallel to the increment in the PbO doping rate. Additionally, an increase in the PbO doping rate hindered the transmission phenomenon based on UV-Vis spectra. Gamma absorption coefficients were measured at six energies with four sources using the gamma spectroscopic system. The measured values were compared with the FLUKA code and Phy-X software. Experimental LAC values of 0.2463, 0.2729, 0.3064, and 0.3618 cm−1 were measured using a Cs-137 source for the ZBBSS glass series, respectively. The variation in the values obtained with the triple methodology overlapped with each other for all energies. Among the prepared glasses, the best LAC and MAC, thinnest HVL, lowest MFP and TF were determined for ZBBSS4 glass sample with maximum PbO content. From the results obtained, it is concluded that the addition of PbO is a useful way to improve the gamma attenuation capacity, and among the glasses examined, ZBBSS4 had superior protection against gamma rays.
This study investigated the extraction, structure and antioxidant activity of turmeric polysaccharides (TPs). A crude polysaccharide yield of 2.23 g/100 g was extracted by the hot water method. Four ...polysaccharide fractions (TPs-0, TPs-1, TPs-2, and TPs-3) with different molecular weights were purified by anion-exchange chromatography. Glucose, galactose and arabinose were the main polysaccharide components of TPs-0 and TPs-1, whereas TPs-2 and TPs-3 were primarily composed of rhamnose, glucose, galactose, arabinose, xylose, galacturonic acid and glucuronic acid. TPs-0 was further investigated using methylation, GC-MS and NMR, the results showed that TPs-0 comprised a main chain of α-Araf- (1 → 4) -α-Glcp- (1 → 3) -α-Arap- (1 → 3) -β-Galp- (1 → 3,6) -α-Galp- (1 → 5) -α-Araf- (1 → 3) -β-Galp- (1→R. Scanning electron microscopy analysis revealed that the characteristic morphology of different fractions. Furthermore, assays of antioxidant activity showed that any one of TPs had antioxidant effects against DPPH radical, ABTS radical cation, hydroxyl radical, among which TPS-2 was stronger. In general, the results demonstrated that TPs had great potential as a natural antioxidant in the functional food.
•Optimized the extraction process of turmeric polysaccharides (TPs).•Four polysaccharides were successively isolated and characterized.•The putative structure of TPs-0 was the reported for the first time.•The four polysaccharides especially TPs-2 exhibited antioxidant activity.
In this paper, time reversal with multiple signal classification (TR-MUSIC) and its phase-coherent form (PC-MUSIC), the two typical ultrasonic time-reversal-based super resolution imaging techniques, ...have been introduced and explored to image defects in metallic samples. The principles for super resolution imaging technique and defect characterization based on ultrasonic image have been presented firstly. And then both TR-MUSIC and PC-MUSIC are tested with experimental ultrasonic array data acquired from the metallic samples including defects using the full matrix capture (FMC) process. Here, if the size of defect is smaller than the central ultrasonic wavelength, the defect can be regarded as point-like target. On the contrary, if the size of defect is larger than the central ultrasonic wavelength, it can be regarded as extended target. The comparison on super resolution imaging for point-like and extended targets has been investigated. For point-like targets, TR-MUSIC as well as PC-MUSIC can distinguish and locate the position, and the overall performance of TR-MUSIC is better than that of PC-MUSIC. For extended target, TR-MUSIC can only determine the area where the defect occurs. PC-MUSIC can distinguish and assess the length of extended target parallel to the array, the lowest error is 9.62% when the dimension of signal subspace is set to be 10 for the case considered. In addition, the defect characterization based on ultrasonic super-resolved image has been studied, and a sizing strategy is introduced. The length and angle of extended targets oblique to the array can be obtained from the PC-MUSIC images. The worst errors for assessing the length and angel are 9.14% and 13.3% respectively. And for the cases considered in the experiment, the longer the length of extended target, the smaller the error.
Modeling powder properties remains a complex and difficult area of study because particulate materials can behave differently under variable conditions based on their bulk and surface-level ...properties. The research presented in this manuscript was designed to support the fundamental understanding of powder systems by joining experimental and theoretical calculations of dimensionless numbers groups for design purposes. In order to do so, this work focused on two critical variables to better understand fluidization design: physical and chemical surface properties. To better resolve the influence of surface properties, surface-treated powders were used. Five different powder samples of varying particle size distribution were characterized using physical property measurements, including pressure drop profiles to obtain the minimum fluidization velocity, density measurements, and particle sizing. Using theoretical equations, the minimum fluidization velocity was also calculated to compare with those obtained experimentally and determine typical dimensionless number groups used in bulk handling system design. The results showed that the theoretically determined values were lower than those calculated using the experimentally umf. In the case of the Reynolds number, the experimental values were 3–20% higher than the theoretical values, which is an important distinction for designing conveying systems and pipeline flow. Similar results were observed for the theoretical and experimental Froude numbers, indicating an important dependence on the cohesive properties of the particle interactions. Additional dimensionless number groups were considered, including the granular bond number and flow factors. To investigate the influence of surface forces, Hamaker constants were utilized for alumina and polydimethylsiloxane in the calculation of the granular bond number. A lower granular bond was observed with a decrease in the Hamaker constant for PDMS, suggesting that the surface forces would be lower for our surface-treated powders.
•The antioxidant activity of four Auricularia polysaccharides were studied.•Polysaccharides of four Auricularia were mainly composed of mannose and galactose.•All polysaccharides contained uronic ...acid and pyran ring with spectroscopy analysis.•Molecular weight was correlated with DPPH, superoxide anion and hydroxyl radicals.•The result indicated that fucose and galactose jointly determine FRAP capacity.
The structural characterization and antioxidant activity of four Auricularia polysaccharides (A.cornea ACP)、A.auricula(AAP)、A.polytricha (APP) and M.fungus(MFP)) were studied in this paper. The results shown: polysaccharides of four Auricularia were mainly composed of mannose and galactose, all polysaccharides contained uronic acid and pyran ring structure with spectroscopy and NMR analysis. There was a significant difference in the total antioxidant capacity and APP was significantly higher than the other polysaccharides. The ability of APP to scavenge DPPH radicals and hydroxyl radicals was significantly higher than that of other polysaccharides, respectively. The molecular weight was significantly positively correlated with DPPH radicals, superoxide anion radicals and hydroxyl radicals. Total antioxidant capacity was significantly negatively correlated with fucose and galactose. The result indicated that fucose and galactose jointly determine total antioxidant capacity. The polysaccharide from four Auricularia had good oxidation resistance and could be used as natural antioxidants.
Fatigue zones in a material can be identified using ultrasonic waves, as it has been shown that their propagation speed will reduce when travelling through such a zone. However, as fatigue damage is ...usually concentrated in a thin near-surface layer, through-thickness measurements result in very small changes of the average propagation speed across the full thickness, which are potentially difficult to reliably correlate to specific fatigue states. In this study, we have completed fatigue state assessments using Rayleigh waves, which travel on the surface of a material, to maximise those changes. We found that the use of Rayleigh waves amplifies the changes in speed, after propagation in the damaged region, by a factor of up to ten. The monotonic nature of the reduction in wave speed was verified against the theory using dislocation density measurements. Finally, a stiffness-reducing finite-element modelling technique, able to capture the effects of fatigue on the time of flight of longitudinal bulk and Rayleigh waves, was also derived and verified against the experimental measurements.
Background
Developments in digital image correlation (DIC) in the last decade have made it a practical and effective optical technique for displacement and strain measurement at high temperatures.
...Objective
This overview aims to review the research progress, summarize the experience and provide valuable references for the high-temperature deformation measurement using DIC.
Methods
We comprehensively summarize challenges and recent advances in high-temperature DIC techniques.
Results
Fundamental principles of high-temperature DIC and various approaches to generate thermal environment or apply thermal loading are briefly introduced first. Then, the three primary challenges presented in performing high-temperature DIC measurements, i.e., 1). image saturation caused by intensified thermal radiation of heated sample and surrounding heating elements, 2) image contrast reduction due to surface oxidation of the heated sample and speckle pattern debonding, and 3) image distortion due to heat haze between the sample and the heating source, and corresponding countermeasures (i.e., the suppression of thermal radiation, fabrication of high-temperature speckle pattern and mitigation of heat haze) are discussed in detail. Next, typical applications of high-temperature DIC at various spatial scales are briefly described. Finally, remaining unsolved problems and future goals in high-temperature deformation measurements using DIC are also provided.
Conclusions
We expect this review can guide to build a suitable DIC system for kinematic field measurements at high temperatures and solve the challenging problems that may be encountered during real tests.
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