Kinetic retention of sialic acid and antioxidants in Malaysian edible bird’s nest during low-temperature drying

Drying is one of the essential processing steps for dried edible bird’s nest; however, sialic acid and antioxidant can be highly thermosensitive and unstable. Therefore, aim of this study was to determine the degradation kinetics of sialic acid and antioxidants during low-temperature drying at 25–40°C as compared to conventional hot air-drying at 70°C. These compounds’ degradation exhibited first-order kinetics. Sialic acid and antioxidant retentions were 83.9 and 96.6%, respectively, at 25°C, and 78.7 and 91.5% at 40°C, respectively, by low-temperature drying; while, 42.5 and 38.7%, respectively, at 70°C by conventional hot air-drying. Finally, empirical models were significantly fitted to predict sialic acid and antioxidant retention as edible bird’s nest reached a certain level of drying, which may be useful from the processing standpoint and validate the usage of low-temperature drying as a process tool for retention of sialic acid and antioxidant in edible bird’s nest.     

A comparative study of two different configurations for exothermic–endothermic heat exchanger reactor

The coupling of the energy intensive endothermic reaction systems with appropriate exothermic reactions reduces the size of the reactors and can improve the thermal efficiency of processes. One type of a suitable reactor for such a kind of coupling is the heat exchanger reactor. In this study, the catalytic methanol synthesis is coupled with the catalytic dehydrogenation of cyclohexane to benzene in an integrated reactor formed from two fixed beds separated by a wall where heat is transferred across the surface of the tube. A steady-state heterogeneous model of the two fixed beds predicts the performance of the two different configurations of the thermally coupled reactor. The co-current mode is investigated and the simulation results are compared with the corresponding predictions for the industrial methanol fixed bed reactor operating in the same feed conditions. The results of the study reveal that should the exothermic and endothermic reactions be located in the shell side and tube side, respectively, the methanol production rate will increase in comparison with the conventional methanol synthesis reactor as well as the case where the exothermic reaction is located in the tube side and endothermic reaction in the shell side.     

Influence of the batch’s ash content on coke quality (CRI and CSR)

To permit more precise assessment of Russia’s coal reserves, the influence of the batch’s ash content on the reactivity (CRI) and postreactive strength (CSR) of the coke produced is analyzed.     

Influence of the blast furnace’s operating conditions and coke quality on the life of air tuyeres

The influence of the coke characteristics and blast-furnace conditions on the durability of air tuyeres is considered.     

Synthesis and characteristics of fly ash and bottom ash based geopolymers–A comparative study

The research was carried out to develop geopolymers mortars and concrete from fly ash and bottom ash and compare the characteristics deriving from either of these products. The mortars were produced by mixing the ashes with sodium silicate and sodium hydroxide as activator solution. After curing and drying, the bulk density, apparent density and porosity, of geopolymer samples were evaluated. The microstructure, phase composition and thermal behavior of geopolymer samples were characterized by scanning electron microscopy, XRD and TGA-DTA analysis respectively. FTIR analysis revealed higher degree of reaction in bottom ash based geopolymer. Mechanical characterization shows, geopolymer processed from fly ash having a compressive strength 61.4 MPa and Young's modulus of 2.9 GPa, whereas bottom ash geopolymer shows a compressive strength up to 55.2 MPa and Young's modulus of 2.8 GPa. The mechanical characterization depicts that bottom ash geopolymers are almost equally viable as fly ash geopolymer. Thermal conductivity analysis reveals that fly ash geopolymer shows lower thermal conductivity of 0.58 W/mK compared to bottom ash geopolymer 0.85 W/mK.     

Assessment of ζ-potential in TiO2 aqueous suspensions: A comparative study based on thermodynamic and rheological methods

It is widely demonstrated that the distinct electrokinetic techniques lead to different values of ζ-potential despite what should be expected from the classical theory. Electrophoresis and conductivity measurements were used to estimate the ζ-potential and the electrical double layer parameters of TiO₂ aqueous suspensions. An assessment of the results was made following thermodynamic and rheological methods. In the first case, the Gibbs free energy increment was compared. In the second one, the yield stress/ζ-potential plots were used. In spite of the ζ-potentials obtained from conductivity, electrophoresis and electrophoresis-conductivity combined techniques are different, the Gibbs free energy increment values do not discriminate the best ζ-potential value. Moreover, the correlation between the yield stress and the square of the ζ-potential has shown that all the ζ-potentials can physically be acceptable. Therefore, the only reasonably conclusion from this study is that the use of combined techniques, like electrophoresis-conductivity, should always be taken as the more cautious approach of evaluating ζ-potentials.     

A comparative study on dielectric and mechanical properties of porous β-Si3N4 ceramics by controlling porosity and microstructure

To ensure the porous Si₃N₄ ceramics with an excellent comprehensive performance for the application of radome, the commonly neglected effect of designed microstructures on dielectric and mechanical properties was investigated. Two typical porous Si₃N₄ ceramics with similar porosity but different microstructures (unidirectionally aligned and uniformly micropore structure with a different dimension of grains) were obtained by freeze casting and gel-casing process. The results indicate that the microstructure has a significant influence on the mechanical properties yet not an obvious effect on the dielectric properties, which means the dielectric constant can be reliably designed based on the porosity without consideration of different microstructures, meanwhile, the mechanical properties can be optimized by the microstructure. Besides, the results of the dielectric properties predicted by Finite Element Analysis show a high agreement with the experimental results. The study could be helpful to design a wave-transmitting component with integrated structure and function.     

Effect of temperature and velocity of superheated steam on initial condensation of distillers’ spent grain pellets during drying

Initial condensation on the sample surface during superheated steam (SS) drying leads to increased sample moisture affecting its mechanical and thermal properties. A study was conducted to understand the effect of temperature and velocity of SS on the amount of initial condensation on distillers’ spent grain pellets with an initial moisture content of 25% (wet basis). These pellets were dried using SS at 120, 150, and 180°C with velocities 0.5, 1.0, 1.2, and 1.4 m/s. Separate experiments were conducted for recording mass and surface temperature of the pellets during SS drying. Mass recorded over the drying period was then compared with the predicted mass obtained by solving the standard heat balance and film condensation equations. The predicted values of mass flux due to initial condensation were in close agreement with directly measured values with a maximum mean square error of 0.20. There was a 60–64% decrease in the amount of initial condensation as the temperature of SS was increased from 120 to 180°C. The results indicate that the initial condensation can be minimal when the temperature of SS is equal or above 180°C with SS velocity equal or above 1 m/s using a preheated drying chamber.     

A modelling study on hydrolysis of whey lactose and stability of β-galactosidase

In the present study, the effect of process conditions on whey lactose hydrolysis and enzyme inactivation were investigated. The experiments were carried out in 250 mL of 25 mM phosphate buffer solution by using β-galactosidase produced from Kluyveromyces marxianus lactis in a batch reactor system. The degree of lactose hydrolysis (%) and residual enzyme activity (%) against time were investigated versus lactose concentration, enzyme concentration, temperature and pH. The mathematical models were derived from the experimental data to show the effect of process conditions on lactose hydrolysis and residual enzyme activity (in the presence and absence of lactose). At the optimum process conditions obtained (50 g/L of lactose concentration, 1 mL/L of enzyme concentration, 37 °C of temperature and pH 6.5), 81% of lactose was hydrolyzed and enzyme lost its activity by 32%. The activation energy for hydrolysis reaction (E _A ) and the enzymatic inactivation energy (E _D ) were calculated as 52.7 kJ/mol and 96.7 kJ/mol. Mathematical models at various process conditions have been confirmed with the experimental results.     

A comparative study on selective properties of Kraft lignin–natural rubber composites containing different plasticizers

Effect of plasticizer type on the kraft lignin–natural rubber composite microstructure and selected properties was determined. The composites were prepared with addition of a commonly used naphthenic oil plasticizer to study the decomposition product of polyurethane (glycerolysate) and its characteristics. Kraft lignin powder was incorporated into the natural rubber matrix in amounts of 10 and 40 parts per 100 parts of natural rubber (phr). The reference samples were prepared without any lignin present. The chemical interaction between the filler particles and natural rubber macromolecules was analyzed by Fourier transform infrared spectroscopy (FTIR) and the adhesion was characterized by scanning electron microscopy (SEM). The results of the adhesion measurements confirmed poor distribution of lignin particles into the natural rubber matrix with increasing filler content. Optimal lignin content in the composites was 10 phr in the case of both plasticizers. Moreover, the results of FTIR verified the formation of non-covalent bonds and the need for modification of the filler to enhance the reinforcing effect in the natural rubber matrix. Dynamic mechanical analysis (DMA) and mechanical measurements proved that the specimen containing 10 phr of lignin with the use of glycerolysate as plasticizer displayed the highest mechanical performance. It was demonstrated that glycerolysate and naphthenic oil as plasticizing agents showed similar effect on the thermal properties of the prepared composites. Also, the measured mechanical properties, such as tensile strength, hardness, resilience, and abrasiveness confirmed these findings.     

A generalized Young’s equation for contact angles of droplets on homogeneous and rough substrates

Using Gibbs’ method of dividing surfaces, the contact angle of a drop on a flat homogeneous rough non-deformable solid substrate is investigated. For this system, a new generalized Young’s equation for the contact angle, including the influences of line tension and which valid for any dividing surface between liquid phase and vapor phase is derived. Under some assumptions, this generalized Young’s equation reduces to the Wenzel’s equation or Rosanov’s equation valid for the surface of tension.     

A screening study on the activation energy of vanadate‐based catalysts for diesel soot combustion

The activation energy of carbon combustion catalysed by alkali vanadates or alkali vanadates/chlorides mixtures is assessed by the Ozawa method. The most active catalyst, Cs₄V₂O₇, entails more than 50% decrease of the activation energy compared to non‐catalytic combustion (from 157 down to 75 kJ/mol). The catalyst performance is enhanced when the catalyst is dissolved in a eutectic liquid (e.g., AgCl + CsCl), which likely improves the catalyst/carbon contact conditions. This revised version was published online in August 2006 with corrections to the Cover Date.     

A comparative study of the effect of Pd-doping on the structural,optical, and photocatalytic properties of sol–gel derived anatase TiO2 nanoparticles

Pd-doped anatase TiO₂ nanoparticles were synthesized by a modified sol–gel deposition technique. The synthetic strategy is applicable to other transition and post-transition metals to obtain phase-pure anatase titania nanoparticles. This is important in the sense that anatase titania forms the most hydroxyl radicals (compared to other polymorphs like rutile, brookite, etc.) for better photocatalytic performance. XRD and Raman data confirm the phase-pure anatase formation. Doping of Pd²⁺ into Ti⁴⁺ sites (for substitutional doping) or interstitial sites (for interstitial doping) creates strain within the nanoparticles and is reflected in the XRD peak broadening and Raman peak shifts. This is because of the ionic radii difference between Ti⁴⁺(∼68 pm) and Pd²⁺(∼86 pm). XPS data confirm the formation of high surface titanol groups at the nanoparticle surface and a large number of loosely bound Ti³⁺–O bonds, both of which considerably enhance the photocatalytic activity of the doped nanoparticles. A comparative study with other metal doping (Ga) shows that TiO₂: Pd nanoparticles have more Ti³⁺–O bonds, which enhance the charge transfer rate and hence improve the photocatalytic activity compared to other transition and post-transition metal-doped titania nanostructures.     

Experimental study on nozzle’s characteristics in secondary cooling zone of slab continuous casting

连铸钢坯的质量直接受到二次冷却的影响,二冷段喷嘴的冷却效果受喷嘴的种类、喷水压力、水流密度等因素的影响。本文设计了测试连铸二冷喷嘴性能的实验方案。实验测定了不同喷水条件下喷嘴的压力和水流量的关系、喷水密度的分布、不同喷嘴对喷水效果的影响,分析了不同喷嘴的性能曲线,实验结果为合理布置二冷段喷嘴、优化二冷制度提供一定的依据。     

A comparative study of the magnetic and microwave properties of Al3+ and In3+ substituted Mg–Mn ferrites

The effect of substitution of diamagnetic Al³⁺ and In³⁺ ions for partial Fe³⁺ ions in a spinel lattice on the magnetic and microwave properties of magnesium–manganese (Mg–Mn) ferrites has been studied. Three kinds of Mg–Mn based ferrites with compositions of Mg_0.9Mn_0.1Fe₂O₄, Mg_0.9Mn_0.1Al_0.1Fe_1.9O₄, and Mg_0.9Mn_0.1In_0.1Fe_1.9O₄ were prepared by the solid-state reaction route. Each mixture of high-purity starting materials (oxide powders) in stoichiometric amounts was calcined at 1100 °C for 4 h, and the debinded green compacts were sintered at 1350 °C for 4 h. XRD examination confirmed that the sintered ferrite samples had a single-phase cubic spinel structure. The incorporation of Al³⁺ or In³⁺ ions in place of Fe³⁺ ions in Mg–Mn ferrites increased the average particle size, decreased the Curie temperature, and resulted in a broader resonance linewidth as compared to un-substituted Mg–Mn ferrites in the X-band. In this study, the In³⁺ substituted Mg–Mn ferrites exhibited the highest saturation magnetization of 35.7 emu/g, the lowest coercivity of 4.1 Oe, and the highest Q×f value of 1050 GHz at a frequency of 6.5 GHz.     

Extraction of cadmium by TODGA–dodecane and TBP–dodecane: A comparative study by MD simulation

Molecular dynamics (MD) simulation of [Cd(II)] along with nitrate ions and water in dodecane was carried out for different nitric acid concentrations. The extraction process using N,N,N’,N’-tetraoctyldiglycolamide (TODGA) and tributyl phosphate (TBP), in biphasic systems, is also simulated at three nitric acid concentrations. In the TBP-based system, the formation of a third phase was observed at 3 M nitric acid concentration. Cd(II) ions form reverse micelles-like clusters with TODGA as an extractant in dodecane. The mass percentage of TODGA in these clusters decreases with increase in the acid concentration while increasing the size of the aggregates at the same time.     

A study on the electrocodeposition processes and properties of Ni�CSiC nanocomposite coatings

Ni–SiC nanocomposite coatings were prepared on a brass substrate by electrocodeposition. The electrodeposition was carried out by adding the SiC nanoparticles to a nickel-containing bath. Nickel deposition processes were analyzed by cathodic polarization curves, and the plating parameters were determined preliminarily by analyzing the effects of different technological parameters on the deposition process. Then, electrocodeposition processes were carried out with different concentrations of SiC nanoparticles in the bath. The effects of current density, stirring rate, and SiC nanoparticle’s concentration in the plating bath on the hardness of coatings were investigated by microhardness tests. Besides the microhardness tests, wearing tests and corrosion tests were also applied to the coatings with the highest hardness and coatings of pure nickel. The structures and surface morphologies of the coatings were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. The experimental results show that the microhardness of the codeposited coating increases with increasing current density and attains a maximum at the SiC concentration of 6 g/L. The decrease in the microhardness at higher SiC concentrations may be due to agglomeration of nanosized particles in the plating bath. Increasing the stirring speed did not give a better quality deposition as coatings produced at low stirring rates always had higher microhardness values than did those at high stirring rates. Furthermore, the Ni–SiC nanocomposite coatings have lower friction coefficient and better corrosion resistance than those of pure nickel coatings.     

Kinetic study and hydrogen peroxide consumption of phenolic compounds oxidation by Fenton’s reagent

Synthetic solutions of phenol, o-, m- and p-cresol were oxidised by using Fenton’s reagent. The application of substoichiometric dosage of H₂O₂ led to the formation of intermediate compounds, continuing later the oxidation to complete oxidation. An important objective was to analyze the effect of hydrogen peroxide dosage applied and the reaction pH together with the iron oxidation state on the degradation level. A kinetic model was derived from a reaction mechanism postulated which was used to analyze the results of the experiments. Another aim was to analyze the hydrogen peroxide consumption. Noteworthy results include an increase in oxidant consumption to intensify phenol removal. Furthermore, oxidant consumption was analyzed through the ratio H₂O₂ to phenol removed and the average specific rate of removal (ASRR). By analyzing these two parameters it has been possible to ascertain the most favorable strategy for an efficient application of H₂O₂.     

Effect of ZnO on the Bioactivity of Hench’s Derived Glasses and Corresponding Glass-Ceramic Derivatives

Some glasses based on Hench’s patented bioglass have been prepared with ZnO replacing Na₂O or CaO in order to investigate their bioactivity in the glassy state or after conversion to their glass-ceramic derivatives. In-vitro investigations of bioactivity of the prepared glass and their glass-ceramics derivatives were carried out by Infrared absorption spectra (IR) of the samples before and after immersion in simulated body fluid (SBF) for different time periods at 37 °C. An X-ray Diffraction (XRD) analysis technique was performed on the glass-ceramic samples to identify the crystalline phases formed during the controlled thermal treatment. Chemical corrosion experiments were also performed to evaluate the chemical behaviour of both glassy and the glass-ceramic derivatives towards SBF. The IR results showed that the amount of the apatite layer formed on the surface of the sample containing ZnO depends on the wt% of ZnO content. The X-ray results indicate that there are two phases formed: sodium calcium silicate and kilchoanite. Weight loss data were observed to change depending on the percent of ZnO and the role of housing of Zn²⁺ in the glass structure. Corrosion behaviour of glass-ceramic derivatives indicates higher durability than in the corresponding parent glasses as expected.