A comprehensive study on the kinetics of aqueous free-radical homo- and copolymerization of acrylamide and diallyldimethylammonium chloride by online 1H-NMR spectroscopy

Free-radical homo- and copolymerization of acrylamide (AAm) and diallyldimethylammonium chloride (DADMAC) initiated with potassium persulfate (KPS) were performed in the presence of 0.1 M NaCl solution in D₂O at 50 °C. Online ¹H-NMR kinetic experiments were used to study polymerization kinetics via determination of the individual and overall conversion of the comonomers and compositions of the comonomer mixture and produced copolymer as a function of the reaction time. Reactivity ratios of the AAm and DADMAC were calculated by Mao-Huglin (MH) and extended Kelen-Tudos (KT) methods to be 7.0855?±?1.3963, 0.1216?±?0.0301 and 6.9458?±?2.0113, 0.1201?±?0.0437 respectively. “Lumped” kinetic parameter (k _p k _t ^??0.5 ) was estimated from experimental data. Results showed that k _p k _t ^??0.5 value increases by increasing mole fraction of the AAm in the initial reaction mixture. Drift in the comonomer mixture and copolymer compositions with reaction progress was evaluated experimentally and theoretically. Theoretical values were calculated from Meyer-Lowry equation by using reactivity ratios obtained from MH method. A good fitting between the experimental and theoretical values was observed, indicating accuracy of the reactivity ratios estimated in the present work. It was found from following changes in the copolymer composition with the comonomer conversion that produced copolymer has a statistical structure.     

Modification of silica nanoparticles with hydrophilic sulfonated polymers by using surface-initiated redox polymerization

Sulfonated polymer/silica hybrid nanoparticles were prepared by free radical polymerization of 2-acrylamido-2-methyl-1-propane sulfonic acid (PAMPS-g-SN) and styrene sulfonic acid sodium salt (PSSA-g-SN), initiated on the surfaces of aminopropyl-functionalized silica nanoparticles (ASN). Ce(IV) ammonium nitrate/nitric acid and sodium dodecyl sulfate were used as redox initiator and stabilizer, respectively. ASN Nanoparticles were synthesized by a covalently attached 3-aminopropyltriethoxysilane onto the surface of silica nanoparticles. Sulfonated monomers (AMPS or SSA) were then grafted onto the ASN nanoparticles, ultrasonically dispersed in water, using redox initiator system at 40?°C. ASN, PAMPS-g-SN and PSSA-g-SN nanoparticles were characterized by Fourier transform infrared (FTIR), thermogravimetry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. FTIR and TGA results indicated that both AMPS and SSA monomers were successfully grafted onto the silica nanoparticles. The grafted amounts of sulfonated polymers onto the silica nanoparticles were estimated from TGA thermograms to be 46 and 22?% for PAMPS and PSSA, respectively. From SEM and TEM micrographs, the average-diameters of the polymer-grafted silica nanoparticles were measured to be <50?nm with a (semi)spherical morphology, in which several silica nanoparticles were able to form a core with PAMPS or PSSA existing around the silica nanoparticles.     

Betalains,the nature-inspired pigments,in health and diseases

Abstract

Betalains are unique nitrogen-containing pigments found exclusively in families of the Caryophyllales order and some higher order fungi, where they replace anthocyanin pigments. Betalains, consisting of betacyanins and betaxanthins are generally used as color additives in food. This review discusses on the favorable effects of acute and chronic consumption of betalains, whose edible sources consist primarily of red beetroots (Beta vulgaris) and prickly pears (fruit of the Opuntia genus of cacti). Moreover, it encompasses in vivo and in vitro studies about the bioavailability and bioaccessibility of betanin and indicaxanthin. It seems that treatment with betalains and betalain-rich diets is not only nontoxic but could also prove to be a promising alternative to supplement therapies in oxidative stress-, inflammation-, and dyslipidemia-related diseases such as stenosis of the arteries, atherosclerosis, hypertension, and cancer, among others. Due to its toxicological safety, accessibility, low price, biodegradability, and potentially advantageous biological effects on health, the incorporation of betalains in food manufacturing and related industries could pave the way to overcome current concerns over the health risks of artificial colors. Nevertheless, further studies using pure betalains are required to gain a deeper understanding of their precise biological functions.     

Practical modelling issues for masonry building retrofitted with squat shear wall

Damage observed following moderate to large earthquakes has shown masonry buildings are vulnerable to lateral shaking. The results of statistical analyses in Iran show that 90% of schools in the retrofitting list are unreinforced masonry buildings. A Practical Guideline for Seismic Rehabilitation of Masonry Schools has been published in Iran. This guideline proposed 2 retrofitting methods for retrofitting masonry schools: use of shear wall and shotcreting the perimeter of building. In the case of shear wall, their construction is usually expensive; there are less projects retrofitted by shear walls, and in most retrofitting masonry schools projects, perimeter shotcrete is used. The main aim of this study is offering recommendation to improve this guideline, resulting in more economical approaches. This study proposes including lateral resistance of masonry walls in resisting seismic loads and in the case of shear wall foundation proposes strip shallow foundation for concrete shear walls by including effect of rocking, sliding, and settlement response. It has been shown that with including masonry walls in lateral resistance of building, a considerable reduction in maximum drift occurred. Interaction of soil and structure by considered strip shallow foundation reduces the base shear and increases maximum drift of the building.     

Direct Observation of Halide Migration and its Effect on the Photoluminescence of Methylammonium Lead Bromide Perovskite Single Crystals

Optoelectronic devices based on hybrid perovskites have demonstrated outstanding performance within a few years of intense study. However, commercialization of these devices requires barriers to their development to be overcome, such as their chemical instability under operating conditions. To investigate this instability and its consequences, the electric field applied to single crystals of methylammonium lead bromide (CH₃NH₃PbBr₃) is varied, and changes are mapped in both their elemental composition and photoluminescence. Synchrotron‐based nanoprobe X‐ray fluorescence (nano‐XRF) with 250 nm resolution reveals quasi‐reversible field‐assisted halide migration, with corresponding changes in photoluminescence. It is observed that higher local bromide concentration is correlated to superior optoelectronic performance in CH₃NH₃PbBr₃. A lower limit on the electromigration rate is calculated from these experiments and the motion is interpreted as vacancy‐mediated migration based on nudged elastic band density functional theory (DFT) simulations. The XRF mapping data provide direct evidence of field‐assisted ionic migration in a model hybrid‐perovskite thin single crystal, while the link with photoluminescence proves that the halide stoichiometry plays a key role in the optoelectronic properties of the perovskite.     

Factors Motivating Citizen Engagement in Mobile Sensing: Insights from a Survey of Non-Participants

Mobile sensing uses features of mobile technology to monitor the environment and if a community participates in such monitoring, there can be community improvements in the quality of life. Despite the numerous potential benefits, the rate of citizen engagement in mobile sensing is generally low. Using the urban sensing project called “2Loud?,” this study was designed to uncover the reasons for non-participation and to discuss the motivations for intention to participate. A survey was administered to citizens who had been invited to participate but had decided not to participate. Examining the four motivational factors of “Concern,” “Belief,” “Technology,” and “Time” through a series of Kruskal-Wallis H Tests indicated that respondents had a statistically significant favorable attitude toward “Intention to Participate” if they had some concern and belief, and if they had access to technology and available time, compared to those who did not. However, binary logistic regression analysis indicated that only “Time” and “Technology” were significant predictors of “Intention to Participate.” These findings are discussed in light of social psychology and information technology theories, and recommendations for improved communication and engagement strategies are suggested.     

OH*-chemiluminescence during autoignition of hydrogen with air in a pressurised turbulent flow reactor

Autoignition of hydrogen in air was studied in a turbulent flow reactor using OH*-chemiluminescence. High-speed imaging was used to visualise the formation of autoignition kernels in the flow, and to analyse the conditions under which temporary stabilisation of the flame kernels occurred. The experiments were carried out at temperatures of 800–850 K, pressures of 0.8–1.2 MPa and an equivalence ratio of φ = 0.25. Measurements of the autoignition delays yielded values in the range of τ = 210–447 ms. The autoignition delay results indicated that, over the range of conditions studied, ignition delays reduced with decreasing pressure. This observation contradicted homogeneous gas-phase kinetic calculations, which predicted an increase in autoignition delay with decreasing pressure. If the kinetic model was altered to include surface reactions at the reactor walls, the calculations could be qualitatively reconciled with the experimental data, suggesting that wall reactions had a significant influence on autoignition delays.