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In this study, three different size (100-300-500 µm) of the rubber powder (waste tire) were used in the formulation of epoxy- phenolic adhesive. Rubber powder was modified with grafting method by acrylamide monomer. In order to prevent any loss in properties such as modulus and strength of the adhesive, which is due to the addition of rubber powder to the adhesive, the micro particles of silica were used in formulation of epoxy- phenolic adhesive.  The experiment was designed by Taguchi method, and in the experiment, the effect of the composition of rubber powder, size of rubber powder, composition of silica filler and phenolic resin on mechanical and thermal properties of epoxy adhesives were investigated. To study the mechanical properties of adhesives and adhesion properties, dumbbell-shaped specimens and single edge lap bonds that have been made of metal (stainless steel) to composite (epoxy resin / carbon fiber) were prepared and subjected to tensile test. Thermal stability and interfacial interaction between epoxy and filler in adhesive formulation were explored by thermogravimetric analysis and Fourier transform infrared spectroscopy analyses, respectively.  Tensile test results showed that for lap- joint bonding with the addition of each factor in its optimal level into epoxy adhesive, strength, modulus and toughness increase by 7.5%, 27.56% and 114% respectively in comparison with  the samples bonded with the neat  epoxy adhesive. A significant increase was obtained in thermal stability for formulated adhesive samples compared with neat epoxy adhesive.
 
 

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In the  Bacillusamyloliquefaciens α-amylase (BAA), the loop (residues from 177-185; region І) is the constructive part of the cage responsible for attachment to calcium. It has two more amino acid residues than the α-amylase from Bacillus licheniformis (BLA). Arg176 in this region makes an ionic interaction with Glu126 from region ІІ (residues 118-131) but this interaction is lost in BLA due to substitution of R176Q and E126V. It is the common feature of α-amylases that calcium ion is required for their thermal stability. The present work quantitatively estimates the effect of ionic interaction on the overall stability of the enzyme. To clarify the functional and structural significance of corresponding salt bridge, first an automated homology model of the mutant enzyme (∆E126) was built by the Swiss-Model Protein Modeling Server.  Bacillus amyloliquefaciens α-amylase (3BH4.pdb) was used as the template and examined by GETAREA and WHAT IF programs, then Glu126 was deleted (∆E126) by site-directed mutagenesis and the thermostability was examined for the wild-type and mutant enzymes. Modeling results showed that deletion of salt bridge affected on the hydrophobic and hydrophilic residues orientation of two discussed regions (Ι, ΙΙ). The mutant enzyme also exhibited lower thermostability relative to the wild-type enzyme. Thus, it may be suggested that salt bridge could affect on accessible surface area of the discussed regions, decrease water diffusion,  prevent diffusion of cations and improve the thermostability of the whole protein.

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The aim of this project is the design and optimization of the formulation of epoxy adhesives for bonding metal to composite parts . This joints are most widely used in the aerospace industry to reduce stress concentration at a point. Joints for single edge joining include stainless steel metal with commercial code 316L and composite epoxy resin / carbon fiber. In this study, the effect of three types of additives: filler (alumina micro-particles), nylon 6.6 and phenolic resin (type of resin) on the mechanical and thermal properties of epoxy adhesive have been investigated. Tensile test results showed that increasing alumina fillers increases the tensile strength and overlap shear adhesive samples, respectively, in single lap joint dumbbells and elderly. The test showed that increasing the amount of nylon 6.6 When is slightly higher due to a sharp drop in tensile strength and overlap shear, respectively, in both cases is dog bone and single lap joint adhesives. This limit depends on the capacity epoxy ring to absorb amide hydrogens. The test for thermal properties (TGA) showed that increasing the amount of phenolic thermal stability is improved. High-temperature tensile test of appropriateness is also increasing impact of phenolic resin. Finally, the adhesive properties built with the similar adhesive (UHU) were compared. Results showed superiority in single lap joint metal to composite adhesive is made in the study.

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Research Subject: Poor mechanical strengths and lack of thermal stabilities of hydrogels confine their extensive practical applications in many areas. The growing scientific need for solving this problem and achievement to the hydrogels with improved properties has led to the design and production of the nanocomposite hydrogels.
Research Approach: The polymeric networks of nanocomposite hydrogels compared to the ordinary hydrogels have improved elasticity and rheological properties. Other points that increase the importance of structural studies of nanocomposite hydrogels are the high strength of these materials versus the application of external forces, as well as maintaining its structure against increasing of temperatures. In this regard, the type and amounts of nanomaterial, the preparation method and formation of hydrogel network have a significant role in improving the physical, chemical and biological properties of hydrogels, and, it must be noted that these parameters will depend on the application of nanocomposite hydrogels. This also highlights the need for the production of nanocomposite tailored hydrogels. Therefore, orientation of the range of nanomaterials, the preparation method and product identification, along with sufficient information on the application of these materials, might have an important role in ensuring the success of these materials, requiring comprehensive library research and studies on polymerization processes, morphology and rheology.
Main Results: In this review article, the scientific advances in the field of nanocomposite hydrogels, focusing on its types based on the type of nanoparticles, its properties, preparation methods, identification methods with a new perspective on rheology, thermal analysis and morphology is investigated. Finally, the applicability of these materials is collected in a comprehensive table in various fields such as tissue engineering, enhanced oil recovery, agriculture, and etc…

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Research subject: Polymer nanofibers have attracted much industrial interest over the past decade. In general, these fibers are suitable for a variety of applications including medical applications, insulation, capacitors, advanced aerospace technologies, and so on. Specifically in aerospace technology, the used materials must be thermally stable with suitable electrical conductivity. However, many of these polymer nanofibers suffer from low temperature degradation and low electrical conductivity, limiting their use in many potential applications. Graphite has unique properties such as high conductivity and high thermal stability. This exceptional material can be included as a nanoparticle in polymer nanofibers to modify electrical and thermal properties.The aim of this research was to investigate the effect of addition of graphite nanoparticle on thermal and electrical propertiesof polymer fibers.
Research approach:  For this purpose, polyvinyl alcohol 72000 (PVA) as a non-conductive polymer and graphite nanoparticles were used. Polyvinyl alcohol-graphite nanofibers were synthesized method by electrospinning technique under optimized parameters. The optimum conditions for the electrospinning process were: PVA concentration of 8%, applied voltage of 22 Kv, flow rate of 10 ml and tip/collector distance of 20 cm.
Main results:  Scanning electron microscopy (SEM) studies showed that produced PVA fibers were smooth, continuous without any bead, with a diameter of about 350 nm. The PVA / graphite nanofibers were also smooth but much thinner (about 200 nm) than PVA fibers at the same processing parameters. Moreover, X-ray patterns of PVA/graphite nanofibers include peaks of graphite particles in the structure and slso the suppression of crystallinity.  According to the results of 4 point probe teste, by increasing weight percentage of graphite in the fibers, electrical conductivity increased up to 0.5 . The thermal behavior of PVA nanofibers after mixing with graphite was also investigated by differential calorimetry analysis (DSC) and TGA. It was demonstrated that PVA / graphite nanofibers are thermally stable up to 300 ° C.

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Aspartic proteases (APs) (EC 3.4.23.X) catalyze the hydrolysis of peptide bonds, a reaction that is fundamental to many biological processes. All of the vertebrate and most of the fungal APs are synthesized as zymogens. Porcine pepsin (EC 3.4.23.1) belongs to the aspartic protease family. Pepsin is a gastric aspartic protease and one of the three principal protein degrading enzymes in the digestive system. Pepsin is an industrial enzyme in the food industry. In this study, thermal stability of pepsin investigated in the different concentrations of aluminium in presence and absence of organic solvents ) butanol, ethanol, 1,4-Butanediol and glycerol). Thermal stability of pepsin increased in the presence of aluminium and decreased in presence of organic solvents ) butanol, ethanol, 1,4-butanediol ) and unchanged in presence of glycerol .Thermal stability of pepsin increased in presence organic solvents with adding of aluminium to its absence. possibly aluminum ions through electrostatic and dative interactions with carboxylate groups of Aspartic acid and Glutamic acid residues are bonded to pepsin structure, and causing to condense enzyme structure which leading to increasing thermal stability of pepsin. Mechanism of increasing thermal stability of pepsin is unknown in presence of aluminium. Therefore, we can reduce the instability of pepsin in presence of organic solvents by
Aluminium.

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Aims: Studies based on thermal stability are considered as one of the methods for investigating the physicochemical properties of proteins in biotechnology. The aim of this study was to evaluate the effect of replacement of Arginine 39 amino acid with lysine on the heat denaturation of mnemiopsin photoprotein 1.
Materials and Methods: In the current experimental study, R39K mutated mnemiopsin was compared with wild protein (in which arginine 39 amino acid was converted to the lysine amino acid). In order to investigate the effect of mutation on the content of the secondary structure, a rotation interpolation method was used. To investigate the possible changes in the rate of thermal stability of mutated and wild proteins, heat denaturation measurements were performed by differential scanning calorimeter. Bioinformatics software were used to compare the structure of two types of proteins.
Findings: The mutated R39K compression decreased in comparison with wild protein. No significant change was observed in the values of thermodynamic parameters, especially T_m. The upward movement of arginine 187 amino acid in the mutated protein decreased the thermal stability of this protein. Increasing the accessible surface of lysine 188 in the mutated protein increased its stability.
Conclusion: In thermal stability of the R39K mutated protein, various factors are effective, including the molecular movements of amino acids, their accessible surface, and the content of the secondary structure of protein stabilizing. This mutation reduces the mutated R39K compression rather than the wild protein; increasing ASA related to Lys188 amino acid in the mutated R39K compared with wild protein increases protein stability, but reducing the amount of secondary structure in this mutated, accompanied by an increase in the molecular upward movement in the Arg187 amino acid serves to reduce the stability of this mutated.

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Aims: Invertase is an enzyme that is widely used in industries. The main source of industrial production of invertase is yeast Saccharomyces cerevisiae (S. cerevisiae). Increasing thermal stability makes an important contribution to improving productivity in related production. The aim of this study was increasing thermal stability of Saccharomyces cerevisiae recombinant protein invertase by site-directed mutagenesis.
Materials and Methods: In the present experimental study, using invertase enzyme from thermophilic bacteria, Thermotoga maritima as template, it was decided to replace the threonine 345 and asparagine 349 amino acid with alanine, using site-directed mutagenesis and in Pichia pastoris, cloning was performed with the SOEing polymerase chain reaction. The activity of natural and mutant recombinant invertase enzymes at different temperatures, different pHs, stability duration, and thermal-performance stability, and Michaelis–Menten kinetics were drawn.
Findings: The thermal-structural stability of the natural and mutant invertease enzymes at 55°C showed that the mutant enzyme had a higher thermal stability at 55°C compared with the natural enzyme. Both natural and mutant enzymes exhibited a similar trend in functional stability. Reduction of K_m and increase of V_max in sucrose substrate and 5-fold increase in K_cat/K_m ratio of mutant enzyme was observed.
Conclusion: Site-directed mutagenesis has no negative effect on the amount of production as well as the secretion of recombinant protein invertase and increases enzyme activity. The mutant enzyme has a higher structural stability than the natural enzyme without altering its functional stability.

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Glucoamylase, is an important economic enzyme due to its ability to hydrolyze starch and β-D-glucose polymers. Understanding of factors affecting the thermal stability of the glucoamylase enzyme is critical in the production of isoenzymes with high heat or cold stability.  In this study, the effect of temperature on the structure and properties of each of the isoenzymes of the mesophilic, thermophilic and psychrophilic glucoamylase were studied. For this purpose, molecular dynamics simulation was used to assess these factors and structural differences. 240 nanosecond of MD simulation was done for three isoenzymes of glucoamylase in four temperatures at 300, 350, 400 and 450 K. The variations of each of these parameters were compared for three isoenzymes, and it was found that among the computable factors in molecular dynamics simulation, electrostatic energy of protein with water, van der Waals energy between proteins and water, free energy solubility (∆G_solvation), instability parameter, nonpolar solvent accessible surface, and total solvent accessible surface can be used to predict thermal stability of a protein during increase of temperature.
 

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In this article, the interaction between lysozyme and CdTe nanoparticles was investigated by UV-Vis spectroscopy, fluorescence, thermal stability, kinetics, and circular dichroism (CD) spectroscopic methods at pH 7.25. It was proved that the fluorescence quenching of lysozyme by CdTe NPs was mainly a result of the formation of the CdTe–lysozyme complex. By the fluorescence quenching results, the Stern–Volmer quenching constant (K_SV), binding constant (Ka), and binding sites (n) were calculated. Under pH 7.25 conditions, the level of binding constant is determined to be 2.33×10³ from fluorescence data. The hydrogen bond or van der Waals force is involved in the binding process. The blue shift of the fluorescence spectral peak of protein after the addition of CdTe nanoparticles reveals that the microenvironments around tryptophan residues are disturbed by CdTe nanoparticles. The effect of CdTe NPs on the conformation of lysozyme has been analyzed by means of UV-Vis spectra and CD spectra, which provided evidence that the secondary structure of lysozyme has been changed by the interaction of CdTe NPs with lysozyme.

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In recent years, many advances have been made in improving the biocatalytic activities of enzymes. Interaction of enzymes and macromolecules have important role in stabilization of enzyme’s structure and function. Lysozyme lyses the bacterial cell wall by splitting ß (1–4) linkages between N-acetylmuramic acid and N-acetylglucosamine of the peptidoglycan in bacterial cell walls. Tragacanth is a polysaccharide obtained from exudates of the species of Astragalus. It is a very complex heterogeneous anionic polysaccharide of high molecular weight. Tragacanth consists of two main fractions: a water-insoluble component called bassorin, and a water-soluble component called tragacanthin. The aim of this investigation was to attach tragacanthin (water-soluble component of tragacanth) to lysozyme by Maillard reaction. The covalent attachment of this hydrocolloid with lysozyme was confirmed by SDS-PAGE and ion exchange chromatography. The conjugates exhibited improved solubility, foaming and emulsion properties. In addition, thermal stability of lysozyme in this conjugate was increased significantly. According to these results, attachment of lysozyme to tragacanthin can increase the application of this hydrocolloid as a functional component and lysozyme as a natural antimicrobial component in food and pharmaceutical industry.

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Heating at high temperatures creates a large change in the chemical properties of oils. Due to effects of oils on health, further research is necessary to choose the best type and quality of oils. Extra virgin olive oil is considered one of the best due to the beneficial effects of dietary oils. The aim of this study was to compare the thermal stability of Iranian and foreign extra virgin olive oil. Eight samples of olive oil were tested in this study. Oils were heated at 120 ° C for 4 h to evaluate the thermal stability, were sampled every 2 hours. Fatty acid composition, Acid value, Peroxide value, Anisidine value, Totox value, Rancimat oxidative stability test, was conducted in accordance with Iranian national standards. Results showed that oleic acid, the major fatty acid in olive oil, was between 69 to 74 percent. There was a significant relationship between time and acid value (P= 0/013), peroxide value (P≤ 0/001), anisidine value (P≤ 0/001), totox value (P≤ 0/001). There was not observed any significant relationship between changes in oil and acid value, peroxide value, anisidine value, but with totox value (P= 0/003) a significant relationship was observed. Interpretation of the data suggests that the thermal process changes the index of acidity, peroxide, anisidine and totox. The changes will further increase with time. According to the obtained results,foreign  extra virgin olive oils are better and are more resistant to heat than Iranian ones.

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The use of essential oils as the preservative agents in food industry faces the problem of interactions with food matrix components, low solubility in aqueous phase, high volatile character and sensitivity to environmental conditions. The aim of this study was to enhance thermal stability and antioxidant activity of Thyme essential Oil (TO) by encapsulation in Chitosan Nanoparticles (CS-NP). TO was encapsulated in CS-NP with an emulsion–ionic gelation crosslinking method and the construction was confirmed by Fourier Transform Infrared spectroscopy (FT-IR) and thermogravimetric analysis techniques. The effect of CS: TO weight ratio encapsulation efficiency, loading capacity, particle size and zeta potential of TO-loaded Chitosan Nanoparticle (CS-NP-TO) were investigated. The encapsulated TO was decomposed at a higher temperature (318-325.4ºC) than free TO (170ºC) reflecting the enhanced thermal stability of TO by encapsulation. Also, when TO was encapsulated in CS-NP, antioxidant activity proved to be superior from that of free TO. The considerable antioxidant activity and thermal stability reveal that such particles have promising application for delivery of TO in medicine, food and feed.

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Although synthetic antioxidants are effective in stabilizing oils against oxidation, because of their negative effects on the health of consumers, their use are being limited. Therefore, the use of natural antioxidants such as essential oils of some plants is increasing. In this study, the effect of three types of essential oils of  oregano, thyme and rosemary as natural antioxidants at concentrations of  0 (control sample) 250, 500, 750 and 1000 ppm and synthetic antioxidant hydroquinone tertiary butyl (TBHQ) at a concentration of 100 ppm on the oil quality characteristics of Nigella Sative seed oil (OSI index, peroxide value, acidity and thymoquinone content) were evaluated on the extraction days, 30, 60 and 90 days of storage. The results showed that the highest and lowest peroxide values ​​were related to antioxidant-free oil (61.13 meqO2/kg oil) and oil containing 750 ppm rosemary essential oil (7.7 meqO2 / kg oil), respectively. The results also showed that the oil samples did not differ significantly in terms of acidity (p <0.05). Thymoquinone as the active ingredient of the oil was better preserved in oils containing essential oils, so that the highest and lowest values ​​were related to oils containing 750 ppm rosemary essential oil (1684 ppm) and oil without antioxidants (1230 ppm), respectively. In general, the results showed that rosemary essential oil at a concentration of 750 ppm instead of TBHQ can be used to stabilize black seed oil and maintain its properties.

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Edible oils are exposed to physicochemical changes during heating, cooking and frying. Due to the high importance of this issue and the public perception of the health of oils prepared in oil shops in the city, this study was conducted to evaluate and compare the thermal stability of sesame oils prepared by shop and industrial press. Sesame oil samples were prepared from four lubrication centers in Ahvaz and their stability during 12 days during the thermal process with tests, acid number, peroxide, anisidine, Totex and iodine to evaluate the oxidative stability and also measure the composition of fatty acids with The use of gas chromatography was performed and evaluated according to Iranian national standards. The results showed that linoleic acid (C18: 2) Level (41.5-42.7) Percentand and oleic acid (C18: 1) Level (38.5- 39.47) Percentand of the maximum fatty acids in sesame oils were studied which The fatty acids of all samples were in the range specified by the National Standard of Iran. The results of acid, iodine, peroxide, anisidine and totex tests all showed a significant difference between the sample of industrially prepared sesame oil and other oils prepared by shop press method and the better performance of industrial oil at a significant level Showed 5%. By interpreting the data and results, it can be found that sesame oils prepared by industrial method have higher thermal stability than oils prepared by shop press method and are more suitable for thermal applications.

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The purpose of this study was to compare the efficacy of citrus peel phenolic compounds extracted using carboxylated multi-walled carbon nanotubes (MWCNT–COOH) with common synthetic antioxidants [butylhydroxyanisole (BHA) and butylhydroxytoluene (BHT)] in stabilizing sunflower oil (SO) during frying (180 ± 5 °C, 24 h). To evaluate the antioxidant activity of these compounds, total phenolic, and flavonoid contents, reducing power, ABTS scavenging activity, β-carotene bleaching ability, and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were measured. Extracts were combined at various concentrations (100-1000 ppm) with SO, and both synthetic antioxidants were standardized at 200 ppm. Thermal-oxidative stability was investigated by assessing the change in peroxide value (PV), color, free fatty acid (FFA) content, conjugated diene value (CDV), and thiobarbituric acid (TBA). Bitter orange peel extract (BPE) displayed a higher content of phenolic compounds and antioxidant activity. At 1000 ppm, it showed a lower FFA content, PV, TBA, and CDV. It can be used as an alternative to synthetic antioxidants. As a result, citrus peel phenolic compounds extracted with MWCNT–COOH can be used as preservatives in frying oils.
 

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In this research, the potential of the electrospraying technique was used for encapsulation of curcumin in natural polymers such as Whey Protein Isolate (WPI) and mixture of WPI/β-CycloDextrin (β-CD). The encapsulated particles were physicochemically characterized and curcumin release profile was evaluated. At WPI concentration of 25%, more uniform particles were formed and most of them were smaller than 0.7 µm in diameter. The encapsulation efficiency of curcumin in WPI and WPI/β-CD solutions was determined as 45.4% and 53.6%, respectively. Differential Scanning Calorimetry (DSC) and ThermoGravimetric Analysis (TGA) of the obtained encapsulated curcumin revealed that WPI and WPI/β-CD polymers could not increase thermal stability of curcumin. Encapsulated curcumin had a better stability than pure curcumin at acidic and alkaline conditions, and the release of curcumin after 7 hours was lower than 40% with the sustained mode in buffer solution conditions (pH= 7.4).