Search results for: proteins stability

Authors: Sang-Myung Jung, Jeong Hyun Ju, Gwang Heum Yoon, Hwa Sung Shin

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Central nervous system (CNS) consists of neuronal cell and supporting cells. Astrocytes are the most common supporting cells and play roles in metabolism between neurons and blood vessel. For this function, engineered astrocytes have been studied as a therapeutic source for CNS injury. In neural tissue engineering, nanofiber has been suggested as an effective scaffold for providing structure and mechanical properties influencing physiology. Cellulose acetate (CA) has been investigated for material to fabricate scaffold because of its biocompatibility, biodegradability and fine thermal stability. In this research, CA nanofiber was modified via heat treatment and its effect on astrocyte activity was evaluated. Adhesion and viability of astrocyte were increased in proportion to stiffness. Additionally, expression of GFAP, a marker of astrocyte activation, was increased via stiffness of scaffold. This research suggests a simple modification method to change stiffness of CA nanofiber and shows cellular behavior affecting stiffness of three-dimensional scaffold independently. For the results, we highlight that the stiffness is a factor to regulate astrocyte activity.

Keywords: astrocyte, cellulose acetate, cell therapy, stiffness of scaffold

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Authors: Samera Salimpour Abkenar

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In traditional dyeing of natural fibers with natural dyes, metal salts are commonly used to increase color stability. This method always carries the risk of environmental pollution (contamination of arable soils and fresh groundwater) due to the release of dyeing effluents containing large amounts of metal. Therefore, researchers are always looking for new methods to obtain a green dyeing system. In this research, the use of the enzymatic dyeing method to prevent environmental pollution with metals and reduce production costs has been proposed. After degumming and bleaching, raw silk fabrics were dyed with natural dyes (Madder and Sumac) by three methods (pre-mordanting with a metal salt, one-step enzymatic dyeing, and two-step enzymatic dyeing). Results show that silk dyed with natural dyes by the enzymatic method has higher color strength and colorfastness than the pretreated with a metal salt. Also, the amount of remained dyes in the dyeing wastewater is significantly reduced by the enzymatic method. It is found that the enzymatic dyeing method leads to improvement of dye absorption, color strength, soft hand, no change in color shade, low production costs (due to low dyeing temperature), and a significant reduction in environmental pollution.

Keywords: eco-friendly, natural dyes, silk, traditional dyeing

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Authors: Tabbye Chavous, Felecia Webb, Bridget Richardson, Gloryvee Fonseca-Bolorin, Seanna Leath, Robert Sellers

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There has been recent renewed attention to Black students’ experiences at predominantly White U.S. universities (PWIs), e.g., the #BBUM (“Being Black at the University of Michigan”), “I too am Harvard” social media campaigns, and subsequent student protest activities nationwide. These campaigns illuminate how many minority students encounter challenges to their racial/ethnic identities as they enter PWI contexts. Students routinely report experiences such as being ignored or treated as a token in classes, receiving messages of low academic expectations by faculty and peers, being questioned about their academic qualifications or belonging, being excluded from academic and social activities, and being racially profiled and harassed in the broader campus community due to race. Researchers have linked such racial marginalization and stigma experiences to student motivation and achievement. One potential mechanism is through the impact of college experiences on students’ identities, given the relevance of the college context for students’ personal identity development, including personal beliefs systems around social identities salient in this context. However, little research examines the impact of the college context on Black students’ racial identities. This study examined change in Black college students’ (N=329) racial identity beliefs over the freshman year at three predominantly White U.S. universities. Using cluster analyses, we identified profile groups reflecting different patterns of stability and change in students’ racial centrality (importance of race to overall self-concept), private regard (personal group affect/group pride), and public regard (perceptions of societal views of Blacks) from beginning of year (Time 1) to end of year (Time 2). Multinomial logit regression analyses indicated that the racial identity change clusters were predicted by pre-college background (racial composition of high school and neighborhood), as well as college-based experiences (racial discrimination, interracial friendships, and perceived campus racial climate). In particular, experiencing campus racial discrimination related to high, stable centrality, and decreases in private regard and public regard. Perceiving racial climates norms of institutional support for intergroup interactions on campus related to maintaining low and decreasing in private and public regard. Multivariate Analyses of Variance results showed change cluster effects on achievement motivation outcomes at the end of students’ academic year. Having high, stable centrality and high private regard related to more positive outcomes overall (academic competence, positive academic affect, academic curiosity and persistence). Students decreasing in private regard and public regard were particularly vulnerable to negative motivation outcomes. Findings support scholarship indicating both stability in racial identity beliefs and the importance of critical context transitions in racial identity development and adjustment outcomes among emerging adults. Findings also are consistent with research suggesting promotive effects of a strong, positive racial identity on student motivation, as well as research linking awareness of racial stigma to decreased academic engagement.

Keywords: diversity, motivation, learning, ethnic minority achievement, higher education

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Authors: Sharifah Nabihah Syed Jaafar, Umar Adli Amran, Rasidi Roslan, Chia Chin Hua, Sarani Zakaria

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Bio-composites derived from plant fiber and bio-derived polymer, are likely more ecofriendly and demonstrate competitive performance with petroleum based. In this research, the green phenolic resin was used as a matrix and oil palm empty fruit bunch fiber (EFB) was used as filler. The matrix was synthesized from soda lignin, phenol and hydrochloric acid as a catalyst. The phenolic resin was synthesized via liquefaction and condensation to enhance the combination of phenol during the process. Later, the phenolic resin was mixed with EFB by using mechanical stirrer and was molded with hot press at 180 oC. In this research, the composites were prepared with EFB content of 5%, 10%, 15% and 20%. The samples that viewed under scanning electron microscopy (SEM) showed that the EFB filler remained embedded in the resin. From impact and hardness testing, samples 10% of EFB showed the optimum properties meanwhile sample 15% showed the optimum properties for flexural testing. Thermal stability of the composites was investigated using thermogravimetric (TGA) analysis and found that the weight loss and the activation energy (Ea) of the composites samples were decreased as the filler content increased.

Keywords: EFB, liquefaction, phenol formaldehyde, lignin

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Authors: Wenxiao Liu, Kun Zhang, Yongqing Li

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Bovine herpesvirus 1, a member of the genus Variellovirus of the subfamily Alphaherpesvirinae, has caused severe economic cost to the bovine industry. In this study, BoHV-1 glycerol protein gD was expressed in insect cells, and the purified gD was immunized in the Balb/C mice to generate monoclonal antibodies. Based on hybridoma cell fusion techniques, 20 monoclonal antibodies against Bovine herpesvirus 1 have been obtained. Further, mAb 3F8 with neutralizing activity and gD were applied to develop a blocking enzyme-linked immunosorbent assay (Elisa) for detecting neutralizing antibodies against BoHV-1, which shows a significant correlation between the blocking Elisa and VNT. The sensitivity and specificity of the test were estimated to be 94.59% and 93.42%, respectively. Furthermore, antibody pairing tests revealed that mAb 1B6 conjugated to fluorescence microspheres was used as the capture antibody, and mAb 3F9 was used as the detectable antibody to establish the immunochromatographic assay (ICS). The ICS was conducted to detect BoHV-1 in bovine samples with high sensitivity, specificity, and good stability. Clinical sample testing revealed that the results of ICS and real-time PCR have a coincidence rate of 95.42%. Our research confirmed that the ICS is a rapid and reliable method for the diagnosis of BoHV-1. In conclusion, our results lay a solid foundation for the prevention and control of BoHV-1 infection.

Keywords: bovine disease, BoHV-1, ELISA, ICS assay

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Authors: Tsu-Hsu Yen

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The interfacial gas adsorption presents a frequent challenge and opportunity for micro-/nano-fluidic operation. In this study, we investigate the wettability, gas accumulation, and nanobubble formation on various homogeneous surface conditions by using MD simulation, including a series of 3D and quasi-2D argon-water-solid systems simulation. To precisely determine the wettability on various substrates, several indicators were calculated. Among these wettability indicators, the water PMF (potential of mean force) has the most correlation tendency with interfacial water molecular orientation than depletion layer width and droplet contact angle. The results reveal that the aggregation of argon molecules on substrates not only depending on the level of hydrophobicity but also determined by the competition between gas-solid and water-solid interaction as well as water molecular structure near the surface. In addition, the surface nanobubble is always observed coexisted with the gas enrichment layer. The water structure adjacent to water-gas and water-solid interfaces also plays an important factor in gas out-flux and gas aggregation, respectively. The quasi-2D simulation shows that only a slight difference in the curved argon-water interface from the plane interface which suggests no noticeable obstructing effect on gas outflux from the gas-water interfacial water networks.

Keywords: gas aggregation, interfacial nanobubble, molecular dynamics simulation, wettability

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Authors: Kristina Karapetyan, Flora Tkhruni, Tsovinar Balabekyan, Arevik Israyelyan, Tatyana Khachatryan

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The ability of the lactic acid bacteria (LAB) to prevent and cure a variety of diseases, their protective role against infections and colonization of pathogenic microorganisms in the digestive tract, has lead to the coining of the term probiotics or pro-life. LAB inhibiting the growth of pathogenic and food spoilage microorganisms, maintaining the nutritive quality and improving the shelf life of foods. They have also been used as flavor and texture producers. Enterococcus strains have been used for treatment of diseases such as diarrhea or antibiotic associated diarrhea, inflammatory pathologies that affect colon such as irritable bowel syndrome, or immune regulation, diarrhea caused by antibiotic treatments. The obtaining and investigation of biological properties of proteinoceous antibiotics, on the basis of probiotic LAB shown, that bacteriocins, metabiotics, and peptides of LAB represent bactericides have a broad range of activity and are excellent candidates for development of new prophylactic and therapeutic substances to complement or replace conventional antibiotics. The genotyping by 16S rRNA sequencing for LAB were used. Cell free culture broth (CFC) broth was purified by the Gel filtration method on the Sephadex Superfine G 25 resin. Antimicrobial activity was determined by spot-on-lawn method and expressed in arbitrary units (AU/ml). The diversity of multidrug-resistance (MDR) of pathogenic strains to antibiotics, most widely used for treatment of human diseases in the Republics of Armenia and Nagorno Karabakh were examined. It was shown, that difference of resistance of pathogens to antibiotics depends on their isolation sources. The influences of partially purified antimicrobial preparations (AMP), obtained from the different strains of Enterococcus genus on the growth of MDR pathogenic bacteria were investigated. It was shown, that bacteriocin containing partially purified preparations, obtained from different strains of Enterococcus faecium and durans species, possess bactericidal or bacteriostatic activity against antibiotic resistant intestinal, spoilage and food-borne pathogens such as Listeria monocytogenes, Staphylococcus aureus, E. coli, and Salmonella. Endemic strains of LAB, isolated from Matsoni made from donkey, buffalo and goat milk, shown broad spectrum of activity against food spoiling microorganisms, moulds and fungi, such as Salmonella sp., Esherichia coli, Aspergillus and Penicillium species. Highest activity against MDR pathogens shown bacteria, isolated from goat milk products. High stability of the investigated strains of the genus Enerococcus, isolated from samples of matsun from different regions of Nagorno-Karabakh (NKR) to the antibiotics was shown. The obtained data show high stability of the investigated different strains of the genus Enerococcus. The high genetic diversity in Enterococcus group suggests adaptations for specific mutations in different environments. Thus, endemic strains of LAB are able to produce bacteriocins with high and different inhibitory activity against broad spectrum of microorganisms isolated from different sources and belong to different taxonomic group. Prospect of the use of certain antimicrobial preparations against pathogenic strains is obvious. These AMP can be applied for long term use against different etiology antibiotic resistant pathogens for prevention or treatment of infectional diseases as an alternative to antibiotics.

Keywords: antimicrobial biopreparation, endemic lactic acid bacteria, intra-species diversity, multidrug resistance of pathogens

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Authors: Mohammad Ahmad Ahmad Odah

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Aging is a complex biological process characterized by the progressive decline of physiological functions and increased vulnerability to age-related diseases. Epigenetic changes, particularly DNA methylation alterations, play a critical role in the aging process by influencing gene expression and genomic stability. This study explores the potential of epigenetic reprogramming as a strategy to reverse aging phenotypes in human fibroblasts. Using CRISPR-Cas9 gene editing and small molecule inhibitors targeting DNA methylation and histone acetylation, we successfully induced significant changes in DNA methylation and gene expression profiles. Our results demonstrate a global reduction in DNA methylation levels and the identification of differentially methylated regions (DMRs) associated with cellular senescence and DNA repair. Additionally, treated fibroblasts exhibited enhanced proliferative capacity, reduced cellular senescence, and improved differentiation potential. These findings suggest that epigenetic reprogramming could be a promising approach for regenerative medicine, offering potential therapeutic strategies to counteract age-related decline and extend healthy lifespan.

Keywords: epigenetic reprogramming, aging, regenerative medicine, DNA methylation, cellular rejuvenation, CRISPR-Cas9, senescence

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Authors: Yousef Naserzadeh, Niloufar Mahmoudi

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Oxidation resistance is one of the important parameters in maintaining the quality of olive oil during its storage. Ensuring the stability of the quality of olive oil is one of the important concerns of the producers and consumers. Prooxidants such as iron and copper accelerate the oxidation reaction, and also anti-oxidants and chelating compounds delay it. In this study, chelating effect of tea extract which contains significant amounts of tannic acid is investigated in comparison with citric acid. To do it, 0.1 ppm copper was added to these four kinds of oil, sunflower, olive, canola, and tallow, and then chelating effect of citric acid (0.01%), tannic acid (0.01%) and tea extract (0.1%) were measured by adding to this composition. To this end, the resistance time of the oils against oxidation was measured at 120 °C and an air flow of 20 liters per hour. And the value of peroxide was measured by oven test in six periods of 24 hours at 105 °C. The results showed that citric acid, tannic acid and tea extract had chelating property and increased the resistance time of the studied oils. As a result, considering chelating property and increasing resistance of oil, tannic acid showed better effect than tea extract and tea extract had better effect than citric acid.

Keywords: tannic acid, chelate, edible oils, black tea extract, TBHQ

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Authors: Amarjyoti Das Mahapatra, Umesh Kumar, Bhaskar Datta

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A pseudo peptide can mimic the biological or structural properties of natural peptides. They have become an increasing attention in medicinal chemistry because of their interesting advantages like more bioavailability and less biodegradation than compare to the physiologically active native peptides which increase their therapeutic applications. Many biologically active compounds contain urea as functional groups, and they have improved pharmacokinetic properties because of their bioavailability and metabolic stability. Recently we have reported a single-step synthesis of sulfonyl urea and sulfonyltriuret from sulfonyl chloride and sodium cyanate. But the yield of sulfonyltriuret was less around 40-60% because of the formation of other products like sulfonamide and sulfonylureas. In the present work, we mainly focused on the selective synthesis of sulfonyltriuret using tetrabutylammonium cyanate and sulfonyl chloride. More precisely, we are interested in the controlled synthesis of oligomeric urea mainly sulfonyltriuret as a new class of pseudo peptide and their application as protease modulators. The distinctive architecture of these molecules in the form of their pseudo-peptide backbone offers promise as a potential pharmacophore. The synthesized molecules have been screened on trypsin enzyme, and we observed that these molecules are the efficient modulator of trypsin enzyme.

Keywords: pseudo peptide, pharmacophore, sulfonyltriuret, trypsin

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Authors: Maryam Khazaei Pool, Lori Lewis

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This is a summary of articles based on higher order B-splines methods and the variation of B-spline methods such as Quadratic B-spline Finite Elements Method, Exponential Cubic B-Spline Method, Septic B-spline Technique, Quintic B-spline Galerkin Method, and B-spline Galerkin Method based on the Quadratic B-spline Galerkin method (QBGM) and Cubic B-spline Galerkin method (CBGM). In this paper, we study the B-spline methods and variations of B-spline techniques to find a numerical solution to the Burgers’ equation. A set of fundamental definitions, including Burgers equation, spline functions, and B-spline functions, are provided. For each method, the main technique is discussed as well as the discretization and stability analysis. A summary of the numerical results is provided, and the efficiency of each method presented is discussed. A general conclusion is provided where we look at a comparison between the computational results of all the presented schemes. We describe the effectiveness and advantages of these methods.

Keywords: Burgers’ equation, Septic B-spline, modified cubic B-spline differential quadrature method, exponential cubic B-spline technique, B-spline Galerkin method, quintic B-spline Galerkin method

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Authors: Bingjie Wang, Qianqian Qang, Nan Lu, Xiubing Liang, Baolong Shen

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Novel composites of HfNbTaTiZrV refractory high-entropy alloy (RHEA) reinforced with 0-5 vol.% Al₂O₃ particles have been synthesized by vacuum arc melting. The microstructure evolution, compressive mechanical properties at room and elevated temperatures, as well as strengthening mechanism of the composites, are analyzed. The HfNbTaTiZrV RHEA reinforced with 4 vol.% Al₂O₃ displays excellent phase stability at elevated temperatures. A superior compressive yield strength of 2700 MPa at room temperature, 1392 MPa at 800 °C, and 693 MPa at 1000 °C has been obtained for this composite. The improved yield strength results from multiple strengthening mechanisms caused by Al₂O₃ addition, including interstitial strengthening, grain boundary strengthening, and dispersion strengthening. Besides, the effects of interstitial strengthening increase with the temperature and is the main strengthening mechanism at elevated temperatures. These findings not only promote the development of oxide-reinforced RHEAs for challenging engineering applications but also provide guidelines for the design of light refractory materials with multiple strengthening mechanisms.

Keywords: Al₂O₃-reinforcement, HfNbTaTiZrV, refractory high-entropy alloy, interstitial strengthening

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Authors: M. Pacio, H. Juárez, R. Pérez-Cuapio E. Rosendo, T. Díaz, G. García

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In this study, zinc oxide (ZnO) quantum dots (QDs) have been prepared by a simple route. The growth parameters for ZnO QDs were systematically studied inside a SiO2 shell; this shell acts as a capping agent and also enhances stability of the nanoparticles in water. ZnO QDs in silica shell could be produced by initially synthesizing a ZnO colloid (containing ZnO nanoparticles in methanol solution) and then was mixed with 3-aminopropylsiloxane used as SiO2 precursor. ZnO QDs were deposited onto silicon substrates (100) orientation by spin-coating technique. ZnO QDs into a SiO2 shell were pre-heated at 300 °C for 10 min after each coating, that procedure was repeated five times. The films were subsequently annealing in air atmosphere at 500 °C for 2 h to remove the trapped fluid inside the amorphous silica cage. ZnO QDs showed hexagonal wurtzite structure and about 5 nm in diameter. The composition of the films at the surface and in the bulk was obtained by Secondary Ion Mass Spectrometry (SIMS), the spectra revealed the presence of Zn- and Si- related clusters associated to the chemical species in the solid matrix. Photoluminescence (PL) spectra under 325 nm of excitation only show a strong UV emission band corresponding to ZnO QDs, such emission is enhanced with annealing. Our results showed that the method is appropriate for the preparation of ZnO QDs films embedded in a SiO2 shell with high UV photoluminescence.

Keywords: ZnO QDs, sol gel, functionalization

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Authors: Metinee Kawsomboon, Thanchanok Tulaphol, Manit Nithitanakul, Jitima Preechawong

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PolyHIPE is a porous polymeric material from polymerization of high internal phase emulsion (HIPE) which contains 74% of internal phase (disperse phase) and 26 % of external phase (continues phase). Typically, polyHIPE was prepared from styrene (S) and divinylbenzene (DVB) and they were used in various kind of applications such as catalyst support, gas adsorption, separation membranes, and tissue engineering scaffolds due to high specific surface areas, high porousity, ability to adsorb large quantities of liquid. In this research, cellulose from water hyacinth (Eichornia Crassipes), an aquatic plant that grows and spread rapidly in rivers and waterways in Thailand was added into polyHIPE to increase mechanical property of polyHIPE. Addition of unmodified and modified cellulose to poly(S/DVB)HIPE resulting in a decrease in the surface area and thermal stability of the resulting materials. Mechanical properties of the resulting polyHIPEs filled with both unmodified and modified cellulose exhibited higher compressive strength and Young’s modulus by 146.3% and 162.5% respectively, compared to unfilled polyHIPEs. The water adsorption capacity of filled polyHIPE was also improved.

Keywords: porous polymer, PolyHIPE, cellulose, surface modification, water hyacinth

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Authors: Mohamed A. Eid, Sobhy M. Aly, Marwa M. Ibrahim, Nadia L. Radwan

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To investigate the interaction effects of vitamin D supplementation combined with aerobic exercises (AE) and conventional physical therapy program (CPTP) on balance and physical performance in children with Down syndrome (DS).Methods: A randomized controlled trial was conducted for 38 children with DS, with ages ranging from 8 to 12 years. They were divided randomly to two groups. The control group (n=19) received the CPTP, while the study group (n=19) received the CPTP, AE, and vitamin D in the form of an oral daily dose of vitamin D3 400 IU (Cholecalciferol). Evaluation of balance by using the Biodex Stability System and physical performance by using the six-minute walk test (6MWT)was performed before and after 12 weeks of the treatment program. Findings: All groups showed a significant improvement in balance and physical performance after treatment (p < 0.05). The study group showed a significant improvement in balance and physical performancecompared with that of the control group (p < 0.05). Conclusion: Vitamin D supplementation combined with AE and CPTP could improve balance and physical performance in children with DS. Therefore, vitamin D and AEshould be considered as adjunctive to the rehabilitation program of these children.

Keywords: aerobic exercises, balance, down syndrome, physical performance, vitamin D

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Authors: Tatyane Lopes de Freitas, Antonio Diogo S. Vieira, Susana Marta Isay Saad, Maria Ines Genovese

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The fruit processing industries generate a large volume of residues to produce juices, pulps, and jams. These residues, or by-products, consisting of peels, seeds, and pulps, are routinely discarded. Fruits are rich in bioactive compounds, including polyphenols, which have positive effects on health. Dry residues from two fruits, acerola (M. emarginata D. C.) and orange (C. sinensis), were characterized in relation to contents of ascorbic acid, minerals, total dietary fibers, moisture, ash, lipids, proteins, and carbohydrates, and also high performance liquid chromatographic profile of flavonoids, total polyphenols and proanthocyanidins contents, and antioxidant capacity by three different methods (Ferric reducing antioxidant power assay-FRAP, Oxygen Radical Absorbance Capacity-ORAC, 1,1-diphenyl-2-picrylhydrazil (DPPH) radical scavenging activity). Acerola by-products presented the highest acid ascorbic content (605 mg/100 g), and better antioxidant capacity than orange by-products. The dry residues from acerola demonstrated high contents of proanthocyanidins (617 µg CE/g) and total polyphenols (2525 mg gallic acid equivalents - GAE/100 g). Both presented high total dietary fiber (above 60%) and protein contents (acerola: 10.4%; orange: 9.9%), and reduced fat content (acerola: 1.6%; orange: 2.6%). Both residues showed high levels of potassium, calcium, and magnesium, and were considered sources of these minerals. With acerola by-product, four formulations of probiotics fermented milks were produced: F0 (without the addition of acerola residue (AR)), F2 (2% AR), F5 (5% AR) and F10 (10% AR). The physicochemical characteristics of the fermented milks throughout of storage were investigated, as well as the impact of in vitro simulated gastrointestinal conditions on flavonoids and probiotics. The microorganisms analyzed maintained their populations around 8 log CFU/g during storage. After the gastric phase of the simulated digestion, the populations decreased, and after the enteric phase, no colonies were detected. On the other hand, the flavonoids increased after the gastric phase, maintaining or suffering small decrease after enteric phase. Acerola by-products powder is a valuable ingredient to be used in functional foods because is rich in vitamin C, fibers and flavonoids. These flavonoids appear to be highly resistant to the acids and salts of digestion.

Keywords: acerola, orange, by-products, fermented milk

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Authors: Asma Hanif, A. I. K. Butt, Shabir Ahmad, Rahim Ud Din, Mustafa Inc

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This paper is devoted to a study of the fuzzy fractional mathematical model reviewing the transmission dynamics of the infectious disease Covid-19. The proposed dynamical model consists of susceptible, exposed, symptomatic, asymptomatic, quarantine, hospitalized and recovered compartments. In this study, we deal with the fuzzy fractional model defined in Caputo’s sense. We show the positivity of state variables that all the state variables that represent different compartments of the model are positive. Using Gronwall inequality, we show that the solution of the model is bounded. Using the notion of the next-generation matrix, we find the basic reproduction number of the model. We demonstrate the local and global stability of the equilibrium point by using the concept of Castillo-Chavez and Lyapunov theory with the Lasalle invariant principle, respectively. We present the results that reveal the existence and uniqueness of the solution of the considered model through the fixed point theorem of Schauder and Banach. Using the fuzzy hybrid Laplace method, we acquire the approximate solution of the proposed model. The results are graphically presented via MATLAB-17.

Keywords: Caputo fractional derivative, existence and uniqueness, gronwall inequality, Lyapunov theory

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Authors: Ghada Ben Hamad, Zohir Younsi, Fabien Salaun, Hassane Naji, Noureddine Lebaz

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The graphene oxide (GO) material has attracted much attention for solar energy applications. This paper reports the synthesis and characterization of partially oxidized graphite oxide (GTO). GTO was obtained by modified Hummers method, which is based on the chemical oxidation of natural graphite. Several samples were prepared with different oxidation degree by an adjustment of the oxidizing agent’s amount. The effect of the oxidation degree on the chemical structure and on the morphology of GTO was determined by using Fourier transform infrared (FT-IR) spectroscopy, Energy Dispersive X-ray Spectroscopy (EDS), and scanning electronic microscope (SEM). The thermal stability of GTO was evaluated by using thermogravimetric analyzer (TGA) in Nitrogen atmosphere. The results indicate high degree oxidation of graphite oxide for each sample, proving that the process is efficient. The GTO synthesized by modified Hummers method shows promising characteristics. Graphene oxide (GO) obtained by exfoliation of GTO are recognized as a good candidate for thermal energy storage, and it will be used as solid shell material in the encapsulation of phase change materials (PCM).

Keywords: modified hummers method, graphite oxide, oxidation degree, solar energy storage

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Authors: S. N. Deepa, A. D. Srinivasan, K. T. Veeramanju, R. Sandeep Kumar, Ashwini Mathapati

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Power transformer is a vital element in a power system as it continuously regulates power flow, maintaining good voltage regulation. The working of transformer much depends on the oil insulation, the oil insulation also decides the aging of transformer and hence its reliability. The mineral oil based liquid insulation is globally accepted for power transformer insulation; however it is potentially hazardous due to its non-biodegradability. In this work efficient alternative biodegradable insulating fluid is presented as a replacement to conventional mineral oil. Dielectric tests are performed as distinct alternating fluid to evaluate the suitability for transformer insulation. The selection of the distinct natural esters for an insulation system is carried out by the laboratory investigation of Breakdown voltage, Oxidation stability, Dissipation factor, Permittivity, Viscosity, Flash and Fire point. It is proposed to study and characterize the properties of natural esters to be used in power transformer. Therefore for the investigation of the dielectric behavior rice bran oil, sesame oil, and sunflower oil are considered for the study. The investigated results have been compared with the mineral oil to validate the dielectric behavior of natural esters.

Keywords: alternative insulating fluid, dielectric properties, natural esters, power transformers

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Authors: Turban Kar, Maitree Bhattacharyya

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Curcumin, a dietary antioxidant has been identified as a wonder molecule to possess therapeutic properties protecting the cellular macromolecules from oxidative damage. In our experimental study, we have explored the effectiveness of curcumin in protecting the structural paradigm of Human Serum Albumin (HSA) when exposed to gamma irradiation. HSA, being an important transport protein of the circulatory system, is involved in binding of variety of metabolites, drugs, dyes and fatty acids due to the presence of hydrophobic pockets inside the structure. HSA is also actively involved in the transportation of drugs and metabolites to their targets, because of its long half-life and regulation of osmotic blood pressure. Gamma rays, in its increasing concentration, results in structural alteration of the protein and superoxide radical generation. Curcumin, on the other hand, mitigates the damage, which has been evidenced in the following experiments. Our study explores the possibility for protection by curcumin during the molecular and conformational changes of HSA when exposed to gamma irradiation. We used a combination of spectroscopic methods to probe the conformational ensemble of the irradiated HSA and finally evaluated the extent of restoration by curcumin. SDS - PAGE indicated the formation of cross linked aggregates as a consequence of increasing exposure of gamma radiation. CD and FTIR spectroscopy inferred significant decrease in alpha helix content of HSA from 57% to 15% with increasing radiation doses. Steady state and time resolved fluorescence studies complemented the spectroscopic measurements when lifetime decay was significantly reduced from 6.35 ns to 0.37 ns. Hydrophobic and bityrosine study showed the effectiveness of curcumin for protection against radiation induced free radical generation. Moreover, bityrosine and hydrophobic profiling of gamma irradiated HSA in presence and absence of curcumin provided light on the formation of ROS species generation and the protective (magical) role of curcumin. The molecular mechanism of curcumin protection to HSA from gamma irradiation is yet unknown, though a possible explanation has been proposed in this work using Thioflavin T assay. It was elucidated, that when HSA is irradiated at low dose of gamma radiation in presence of curcumin, it is capable of retaining the native characteristic properties to a greater extent indicating stabilization of molecular structure. Thus, curcumin may be utilized as a therapeutic strategy to protect cellular proteins.

Keywords: Bityrosine content, conformational change, curcumin, gamma radiation, human serum albumin

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Authors: Meng-Hao Chen, Jeng-Der Huang, Chia-Ray Chen

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With the new space mission need of high power dissipation, low thermal inertia and cyclical operation unit, such as high power amplifier (HPA) for synthetic aperture radar (SAR) satellite, the development of phase change material (PCM) technology seems to be a proper solution. Generally, the expected benefit of PCM solution is to eliminate temperature variation and maintain the stability of electronic units by using the latent heat during phase change process. It can also result in advantages of decreased radiator area and heater power. However, the PCMs have a drawback of low thermal conductivity that leads to large temperature gradient between the heat source and PCM. This paper thus presents both experimental and simplified numerical investigations on configuration design of PCM’s container. A comparison was carried out between the container with and without internal pin-fins structure. The results showed the benefit of pin-fins that act as the heat transfer enhancer to improve the temperature uniformity during phase transition. Furthermore, thermal testing and measurements were presented for four PCM candidates (i.e. n-octadecane, n-eicosane, glycerin and gallium). The solidification and supercooling behaviors on different PCMs were compared with available literature data and discussed in this study

Keywords: phase change material (PCM), thermal control, solidification, supercooling

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Authors: Khries Sawsan

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the phenomenon of urbanization is considered as one of the most important tourism resources that differ from one country to another and from one region to another in the same country. Our concern in tourism accommodation is explained by the fact that their location is directly related to the movement to tourist sites .Besides, these constructions comport security considered as the most important motivation for tourists in their choice of any destination. Hotels are the most representative expression of tourism. This is due to their physical prominence in the landscape and being the sole urban component totally unique to tourism. This study sheds light on the impact of tourism development on the spatial pattern in Jordan. It describes the linkages between existing tourism development policies and the spatial development patterns that have occurred as a result throughout Jordan, particularly looking at the impact that tourism has had on the physical environment of major tourism destinations. It puts an illustrative plan of the impact of the augmentation of tourism accommodations in Jordan in the past 40 years ago. The findings of this study help us to understand better the operation of Jordan’ dynamic changes in the location An intensive analysis is then applied on a representative case study in three regions: Amman, Petra and Aqaba. The study proceeds from an historical perspective to, show the evolution of the current development patterns an increase of tourism’s impact on spatial, in the presence of factors as political and economic stability, is expected.

Keywords: spatial patterns, urbanisation, spatial transformations, tourism planning, Jordan

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Authors: Chengzhu Liao, Jianbo Zhang, Haiou Wang, Jing Ming, Huili Li, Yanyan Li, Hua Cheng, Sie Chin Tjong

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Since Bonfield’s group’s pioneer work, there has been growing interest amongst the materials scientists, biomedical engineers and surgeons in the use of novel biomaterials for the treatment of bone defects and injuries. This study focuses on the fabrication, mechanical characterization and biocompatibility evaluation of high density polyethylene (HDPE) reinforced with hydroxyapatite nanorods (HANR) and carbon nanofibers (CNF). HANRs of 20 wt% and CNFs of 0.5-2 wt% were incorporated into HDPE to form biocomposites using traditional melt-compounding and injection molding techniques. The mechanical measurements show that CNF additions greatly improve the tensile strength and Young’s modulus of HDPE and HDPE-20% nHA composites. Meanwhile, the nHA and CNF fillers were found to be effective to improve dimensional and thermal stability of HDPE. The results of osteoblast cell cultivation and dimethyl thiazolyl diphenyl thiazolyl tetrazolium (MTT) tests showed that the HDPE/ CNF-nHA nanocomposites are biocompatible. Such HDPE/ CNF-nHA hybrids are found to be potential biomaterials for making orthopedic joint/bone replacements.

Keywords: biocompatibility, biocomposite, carbon nanofiber, high density polyethylene, hydroxyapatite

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Authors: Sheng-Long Lee, Tse-An Pan

Abstract:

In this study, an optical microscope (OM), electron microscope (SEM), electrical conductivity meter (% IACS), hardness test, and wear test were subjected to analyze the microstructure of the wrought Al-11Si-3Cu-0.5Mg alloys. The effect of eutectic silicon morphology and alloy hardness on wear properties was investigated. The results showed that in the cast state, the morphology of eutectic silicon modified by strontium and antimony is lamellar and finer fibrous structure. After homogenization, the eutectic Si modified by Sr coarsened, and the eutectic Si modified by Sb refined due to fragmentation. The addition of modifiers, hot rolling, and solution aging treatment can control eutectic silicon morphology and hardness. The finer eutectic silicon and higher hardness have better wear resistance. During the wearing process, a protective oxide layer, also known as Mechanical Mixed Layer (MML), is formed on the surface of the alloy. The MML has higher stability and cracking resistance in Sr-modified alloys than in Sb-modified alloys. The study found that the wearing behavior of Al-11Si-3Cu-0.5Mg alloy was enhanced by the combination of adding Sr with lower solution time and T6 peak aging.

Keywords: Al-Si-Cu-Mg alloy, eutectic silicon, heat treatment, wear property

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Authors: Kageeporn Wongpreedee, Bongkot Phichaikamjornwut, Duangkhae Bootkul

Abstract:

The technique of stone in place casting had been established in jewelry production for two decades. However, the process were not widely used since it was limited to precious stones with high hardness and high stabililty at high temperature. This experiment were tested on tourmaline which is semi-precious gemstone having less hardness and less stability comparing to precious stones. The experiment were designed into two parts. The first part is to understand the phenomena of tourmaline under the heating conditions. Natural tourmaline stones were investigated and compared inclusions inside stones tested at temperature of 500 °C, 600 °C, and 700 °C. The second part is to cast the treated tourmaline with ion-implanation under the stones in place casting conditions. The results showed that stones were able to tolerate as much as at 700 °C showing the growths of inclusions inside the stones. The second part of this experiment were compared tourmaline with ion-implantation and natural tourmaline using on stones in place casting process at different stone setting types. The results showed that the cracks and inclustions of both treat and natural tourmaline with stones in place casting were propagate due to high stress of metal contractions. The stones with ion-implatation were more likely tolerate to cracks and inclusion propagations inside the stones.

Keywords: stone in place casting, tourmaline, ion implantation, metal contraction

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Authors: K. Thiel, P. Patrikainen, C. Nagy, D. Fitzpatrick, E.-M. Aro, P. Kallio

Abstract:

Photosynthetic cyanobacteria have been recognized as potential future biotechnological hosts for the direct conversion of CO₂ into chemicals of interest using sunlight as the solar energy source. However, in order to develop commercially viable systems, the flux of electrons from the photosynthetic light reactions towards specified target chemicals must be significantly improved. The objective of the study was to investigate whether the autotrophic production efficiency of specified end-metabolites can be improved in engineered cyanobacterial cells by rescuing excited electrons that are normally lost to molecular oxygen due to the cyanobacterial flavodiiron protein Flv1/3. Natively Flv1/3 dissipates excess electrons in the photosynthetic electron transfer chain by directing them to molecular oxygen in Mehler-like reaction to protect photosystem I. To evaluate the effect of flavodiiron inactivation on autotrophic production efficiency in the cyanobacterial host Synechocystis sp. PCC 6803 (Synechocystis), sucrose was selected as the quantitative reporter and a representative of a potential end-product of interest. The concept is based on the native property of Synechocystis to produce sucrose as an intracellular osmoprotectant when exposed to high external ion concentrations, in combination with the introduction of a heterologous sucrose permease (CscB from Escherichia coli), which transports the sucrose out from the cell. In addition, cell growth, photosynthetic gas fluxes using membrane inlet mass spectrometry and endogenous storage compounds were analysed to illustrate the consequent effects of flv deletion on pathway flux distributions. The results indicate that a significant proportion of the electrons can be lost to molecular oxygen via Flv1/3 even when the cells are grown under high CO₂ and that the inactivation of flavodiiron activity can enhance the photosynthetic electron flux towards optionally available sinks. The flux distribution is dependent on the light conditions and the genetic context of the Δflv mutants, and favors the production of either sucrose or one of the two storage compounds, glycogen or polyhydroxybutyrate. As a conclusion, elimination of the native Flv1/3 reaction and concomitant introduction of an engineered product pathway as an alternative sink for excited electrons could enhance the photosynthetic electron flux towards the target endproduct without compromising the fitness of the host.

Keywords: cyanobacterial engineering, flavodiiron proteins, redirecting electron flux, sucrose

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Authors: Sung Duk Kim, Kwan U. Kim, Jin Sim, Ryong Jin Jang

Abstract:

The phenomenon of seasonal variations in the Earth’s rotation velocity was discovered in the 1930s when a crystal clock was developed and analyzed in a quantitative way for the first time between 1955 and 1968 when observation data of the seasonal variations was analyzed by an atomic clock. According to the previous investigation, atmospheric circulation is supposed to be a factor affecting the seasonal variations in the Earth’s rotation velocity in many cases, but the problem has not been solved yet. In order to solve the problem, it is necessary to apply dynamics to consider the Earth’s spatial motion, rotation, and change of shape of the Earth (movement of materials in and out of the Earth and change of the Earth’s figure) at the same time and in interrelation to the accuracy of post-Newtonian approximation regarding the Earth body as a system of mass points because the stability of the Earth’s rotation angular velocity is in the range of 10⁻⁸~10⁻⁹. For it, the equation was derived, which can consider the 3 kinds of motion above mentioned at the same time by taking the effect of the resultant external force on the Earth’s rotation into account in a relativistic way to the accuracy of post-Newtonian approximation. Therefore, the equation has been solved to obtain the theoretical values of periodic change in the Earth’s rotation velocity, and they have been compared with the astronomical observation data so to reveal the cause for the periodic change in the Earth’s rotation velocity.

Keywords: Earth rotation, moment function, periodic change, seasonal variation, relativistic change

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Authors: Nuray Yılmaz Baran

Abstract:

The conjugated Schiff base polymers which are also called as polyazomethines are promising materials for various applications due to their good thermal resistance semiconductive, liquid crystal, fiber forming, nonlinear optical outstanding photo- and electroluminescence and antimicrobial properties. In recent years, polyazomethines have attracted intense attention of researchers especially due to optoelectronic properties which have made its usage possible in organic light emitting diodes (OLEDs), solar cells (SCs), organic field effect transistors (OFETs), and photorefractive holographic materials (PRHMs). In this study, N-(pyridin-2-ylmethylidene)pyridin-2-amine Schiff base was synthesized from condensation reaction of 2-aminopyridine with 2-pyridine carbaldehyde. Polymerization of Schiff base was achieved by polycondensation reaction using NaOCl oxidant in methanol medium at various time and temperatures. The synthesized Schiff base monomer and polymer (Poly(N-(pyridin-2-ylmethylidene)pyridin-2-amine)) was characterized by UV-vis, FT-IR, 1H-NMR, XRD techniques. Molecular weight distribution and the surface morphology of the polymer was determined by GPC and SEM-EDAX techniques. Thermal behaviour of the monomer and polymer was investigated by TG/DTG, DTA and DSC techniques.

Keywords: polyazomethines, polycondensation reaction, Schiff base polymers, thermal stability

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Authors: Obaid Alotaibi

Abstract:

Tourism and recreation have become one of the important and influential sectors in most of the modern economies. This sector has been accepted as one of the alternative sources of national income, employment, and foreign exchange. Kuwait has many potentialities in tourism and recreation, and exploitation of this leads to more diversification of the economy besides augmenting its contribution to the GDP. It is an import-oriented economy; it requires hard currencies (foreign exchange) to meet the import costs as well as to maintain stability in the international market. To compensate for the revenue fall stemmed from fluctuations in oil prices -where the agriculture, fisheries, and industrial sectors are too immune and inelastic- the only alternative solution is the regeneration of the tourism and recreation to surface. This study envisages the characteristics of tourism and recreation, the economic and social importance for the society, the physical and human endowments, as well as the tourist pattern and plans for promoting and sustaining tourism in the country. The study summarizes many recommendations, including the necessity of establishing authority or a council for tourism, linking the planning of tourism development with the comprehensive planning for economic and social development in Kuwait in the shadow of 2035 vision, and to encourage the investors to develop new tourist and recreation projects.

Keywords: Kuwait, public-private, partnership, tourism, 2035 vision

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Authors: Olumayede Emmanuel Gbenga, Adeniyi Azeez Adebayo

Abstract:

Carbonyls are the first-generation products from tropospheric degradation reactions of volatile organic compounds (VOCs). This computational study examined the mechanism of removal of carbonyls from the atmosphere via hydroxyl radical. The kinetics of the reactions were computed from the activation energy (using enthalpy (ΔH**) and Gibbs free energy (ΔG**). The minimum energy path (MEP) analysis reveals that in all the molecules, the products have more stable energy than the reactants, which implies that the forward reaction is more thermodynamically favorable. The hydrogen abstraction of the aromatic aldehyde, especially without methyl substituents, is more kinetically favorable compared with the other aldehydes in the order of aromatic (without methyl or meta methyl) > alkene (short chain) > diene > long-chain aldehydes. The activation energy is much lower for the forward reaction than the backward, indicating that the forward reactions are more kinetically stable than their backward reaction. In terms of thermodynamic stability, the aromatic compounds are found to be less favorable in comparison to the aliphatic. The study concludes that the chemistry of the carbonyl bond of the aldehyde changed significantly from the reactants to the products.

Keywords: atmospheric carbonyls, oxidation, mechanism, kinetic, thermodynamic

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