Papers by Keyword: Stability

Abstract: Currently, native starch as a binder and sizing component is used extremely rarely due to its inherent disadvantages. It has been replaced everywhere with modified starches of various kinds. Studies have shown that polyelectrolyte flocculants can be created on the basis of starch if ionizable groups are introduced into the macromolecules of amylose and amylopectin. At the same time, it was found that the treatment of starch with oxidizing agents (of various natures and activities) can significantly improve the functional properties of native starch when gluing, used for surface sizing, and as a binder for corrugated cardboard. In this work, we also obtained oxidized starch in order to create an adhesive binder on its basis, and only local raw materials were used. It is shown that this method makes it possible to regulate the number of functional groups (oxidizing effect, or OE) in oxidized starch and its paste viscosity within a wide range. This is achieved by changing the molar ratio of the catalyst and oxidizer. During the oxidation process, it is possible to vary the concentration ratios of the oxidizer, catalyst, and conditions. Using FeSO₄ as a catalyzer, the oxidized starch pastes show a less pronounced pseudoplasticity and are characterized by reduced viscosity. The analysis showed that during the oxidation of corn starch with hydrogen peroxide, changes in the supramolecular structure of starch are insignificant: a certain repeated decrease in the level of crystallinity takes place, which leads to a decrease in the gelatinization temperature and also the viscosity of starch pastes.

Abstract: This research evaluates the performance of hot mix asphalt modified with fly ash and waste foundry sand for road development. Preliminary tests were conducted to determine material properties. Hot mix asphalt samples with varying percentages of granite, sand, stone dust, and bitumen (5%, 5.5%, 6%, 6.5%, and 7%) were produced using ASTM D6927 Marshall mix design. The optimum bitumen content (OBC) was found from the mix to be 5.7%. Using the same mix design, bituminous mixtures were created with waste foundry sand as a partial replacement for fine aggregate (10% - 50% at 10% intervals), along with granite, stone dust, and 5.7% bitumen (OBC). The mix with 40% replacement performed optimally. A new mixture, incorporating granite, sand, fly ash (10% - 60% replacement for filler material, at 10% intervals), and 5.7% bitumen (OBC), was produced. The optimal replacement percentage was 50%. A combination mix of the materials, based on derived optimums, achieved a stability value of 26.09 kN, meeting the Asphalt Institute's criteria. Microstructural analysis indicated a densely packed agglomeration of particles, implying good strength properties. This research demonstrates the viability of waste foundry sand and fly ash as alternative materials, enhancing the strength and flexibility of hot mix asphalt. Reusing these waste materials in road construction is a positive step towards sustainability.

Abstract: The xynBTN63D gene sub-cloned on the plasmid shuttle vector pESC and pYHM1 in the host Escherichia coli BL21 (DE3) was successfully expressed and characterized. The xynBTN63D gene in the soluble fraction of each plasmid is expressed at induction temperatures of 25, 30, 35, 37, and 40 °C with a molecular weight of ±30 kDa. The soluble fraction of the xynBTN63D gene in both plasmids was expressed at induction temperatures of 25, 30, 35, 37, and 40°C with a molecular weight of ±30 kDa. The recombinant XynBTN63D, purified using the fast protein liquid chromatography (FPLC) method also has a molecular weight of ±30 kDa, observed using the sodium dodecyl polyacrylamide sodium electrophoresis (SDS-PAGE) method. The recombinant XynBTN63D has a temperature of 40 °C and an optimum pH of 5.5. It shows stability from 4 to 40 °C after preincubation for 1 hour with relative activity on the pCES and pMH1 plasmid of more than 50%. Recombinant XynBT63D also showed pH stability after being preincubated for 24 hours by showing relative activity of 86-100% at pH 5.0 to 6.0 for each plasmid

Abstract: Perovskite semiconductor have gained increasing attention in the recent years. However, pristine halide perovskites often faces bottle-neck related to low their stability. Herein, for the first time synthesis and fabrication of CsPbBr3/PAN fiber composite with electrospinning method is reported. CsPbBr3 quantum dots (QDs) embedded PAN fiber were successfully fabricated based on the XRD and FTIR test result. The result demonstrates electrospun fiber stable for over than one week in the condition of being immersed in water. The CsPbBr3 QDs was synthesized by Ligand Assisted Reprecipitation Process (LARP) method. The average particle size of our CsPbBr3 particle sizes ranging from 80 to 240 nm. Our findings reveal that the effect of variations between toluene and acetone had an effect on the size of the fiber and the intensity of photoluminescence reduction of the CsPbBr3/PAN fiber composite. Which is the smallest fiber and the lowest reduction intensity belongs to the 4:1 variation, namely with a fiber size of a 727.56 nm and a percentage decrease in intensity of 66,67%.

Abstract: For bridges with a slender bridge deck, ensuring sufficient stability under external loads is one of the technical problems that must be addressed. This paper studies the stability of a flat arch under asymmetric loads. Flat arch structures can form a directly walkable bridge deck. These structures can be realized without external prestressing only up to certain spans due to the necessity of capturing significant horizontal forces. The paper includes a static study that analyses the possible arrangements of the prestressing cables. The study evaluates the stabilizing effect of external prestressing and the possibility of creating a self-anchored system. Based on the results of the static study, a suitable variant was chosen for the design of a physical experiment. The experimental measurements compare the increase of stability for an arch discretely connected to a prestressing cable and an arch structure with a tie without mutual connection.

Abstract: The Dirac contour representation functions fk(z) and fb(z) are employed to represent theket states |f ⟩ and bra states ⟨f |, respectively, in quantum systems with a finite-dimensional Hilbertspace H_2j+1. The scalar product within these quantum systems is defined using a contour integral.Moreover, a numerical approach is utilized to examine the time evolution of both periodic and non-periodic systems, utilizing several Hamiltonian matrices. Furthermore, the stability of periodic systemsis investigated. In addition to these aspects, we study the most significant application of the Dirac con-tour representation, which is its capability to handle an extended Hilbert space, suitable for describingquantum physics at negative temperatures.

Abstract: Nanolubricants are a critical topic currently due to their outstanding thermal conductivity and system performance. A highly stable nanolubricant dispersion is extremely useful for good lubrication performance. However, maintaining their dispersion stability over time is still a major challenge in this field. As a result, the goal of this paper is to evaluate the influence of sonication duration on the stability and thermal conductivity of nanolubricants. In this work, 0.1 vol% concentrations of graphene (Gr) and aluminium nitride (AlN) nanoparticles and polyolester oil (POE) as the base fluid are used. The duration of mechanical stirrer is constant however the ultrasonication time is varied. The stability of nanolubricants are observed by using visual observation technique for 21 days and measured by thermal conductivity and Zeta potential. The results show that the 45 min of sonication time for AlN and 15 min of sonication time for Gr are the optimum time for the ultrasonication.

Abstract: Anthocyanins exhibit exciting colours in plants. Java plum fruit (Syzygium cumini) is considered a non-conventional and rarely consumed fruit with high levels of anthocyanins. This study was conducted to extract, purify, and characterise anthocyanins from dried Java plum fruits. The stability of anthocyanins was also studied. Anthocyanins in this study were extracted from dried Java plum fruits using acidified water (0.01% HCl, v/v) as a sustainable solvent. The crude extracts were loaded into a solid phase extraction (SPE) column packed with Amberlite-XAD-7HP with sequential elution. The ethanol solution was then analysed and characterised using UV-Vis spectrophotometry and Liquid Chromatography-Mass Spectrometry (LC-MS) to confirm the anthocyanins profiles present in the extracts; Anthocyanins extracted from Java plum fruits were identified as cyanidin-3-O-glucoside ([M+] m/z of 449.3), delphinidin-3-O-glucoside ([M+] m/z of 465.3), and petunidin-3-O-glucoside ([M+] m/z of 479.3). Total monomeric anthocyanin content (TMAC) was 0.13 mg/mL (cyanidin-3-O-glucoside eq.). Anthocyanins show various colours depending on the pH of the solution. Anthocyanins are stable at acidic pH and start degrading at neutral to alkaline pH. The suggested application of highly coloured anthocyanins extracted from dried Java plum is as natural colorants in foods, beverages, textiles, cosmetics etc.

Abstract: A methodology for analytical stability assessment of individual compressed flexible phases of discretely heterogeneous composite elements of engineering structures is proposed to ensure their reliable safe operation and minimise the consequences of emergencies. Based on the energy balance equation for the proportional forces of a normal resistance of the medium to the phase displacement, expressions are obtained for determining the critical force, taking into account the possible initial curvature (non-rectilinearity) of a single phase in the elastic medium of the matrix for three possible cases of stability loss. The approbation of the results of the study on the example of deformation features of reinforcing bars in a compressed reinforced concrete column is presented.

Abstract: The aim of this study was to improve the stability and rheological properties of water-in-oil-in-water (W/O/W) multiple emulsions containing 30 wt% paraffin oil, and 4 wt% polyglycerol-3-polycinoleate (PGPR) as a lipophilic surfactant. This was done by adding different concentrations of xanthan gum (GX) and the hydrophilic surfactants (Polyoxyethylene (80) sorbitan monooleate (Tween® 80), poloxamer 407(Lutrol® F127) using the emulsification in a two-steps process. The stability of the W/O/W multiple emulsions was analyzed over one-month storage period using physicochemical and rheological measurements. An excellent structure appeared with 0.175 wt% of xanthan gum in the outer aqueous phase and 1 wt% of Tween® 80. The modified Cross model was successfully applied to fit the flow curves of multiple W/O/W emulsions at different concentrations of xanthan gum. The incorporation of xanthan gum in a concentration range of 0.05-0.175 wt% induced an increase in the yield stress, in the zero-shear rate viscosity, and in the infinite shear rate viscosity of the multiple emulsions. The study also showed that adding xanthan gum in a concentration range of 0.05-0.175 wt% to W/O/W emulsions caused an increase in the viscosity of the system in the Newtonian regime and viscoelastic behavior.