Preparation of sol�Cgel hybrid materials from ��-methacryloxypropyltrimethoxysilane and tetramethyl orthosilicate: study of the hydrolysis and condensation reactions

Organic?Cinorganic hybrid materials suitable for the development of sol?Cgel coatings for metallic surfaces were prepared by hydrolysis and condensation of ??-methacryloxypropyltrimethoxysilane (MAPTMS) and tetramethyl orthosilicate (TMOS). The hydrolysis of MAPTMS/TMOS was carried out in an ethanol/water solution. The prehydrolysis stage of MAPTMS/TMOS system was monitored by Fourier transform infrared spectroscopy (FTIR) and liquid-state ²⁹Si and ¹³C nuclear magnetic resonance (²⁹Si and ¹³C NMR). FTIR analysis indicated that the hydrolysis of MAPTMS/TMOS was accomplished as far as the (SiOMe) band corresponding to unhydrolyzed silane disappeared. The concentration of the alkoxy groups and the extent of self-condensation of mono-, di-, and trisubstituted siloxanes (T species) in the sol were estimated by using liquid-state ²⁹Si NMR spectroscopy. The hydrolysis of the prepared sol was also evaluated by liquid-state ¹³C NMR spectroscopy. The results indicated that under the adopted synthesis strategy conditions, the hydrolysis process requires 4?h to be completed.     

Jacobis Vierquadratesatz und die Zetafunktion der Hurwitz-Quaternionen

Mathematische Semesterberichte - Wir stellen eine weitere Variante des Beweises des Jacobischen Vierquadratesatzes vor, die auf arithmetischen Eigenschaften der Hurwitzschen Quaternionen basiert.     

Reactive Compression Molding Post-Inverse Vulcanization: A Method to Assemble,Recycle, and Repurpose Sulfur Polymers and Composites

Inverse vulcanization provides dynamic and responsive materials made from elemental sulfur and unsaturated cross-linkers. These polymers have been used in a variety of applications such as energy storage, infrared optics, repairable materials, environmental remediation, and precision fertilizers. In spite of these advances, there is a need for methods to recycle and reprocess these polymers. In this study, polymers prepared by inverse vulcanization are shown to undergo reactive compression molding. In this process, the reactive interfaces of sulfur polymers are brought into contact by mechanical compression. Upon heating these molds at relatively low temperatures (≈100 °C), chemical bonding occurs at the polymer interfaces by S−S metathesis. This method of processing is distinct from previous studies on inverse vulcanization because the polymers examined in this study do not form a liquid phase when heated. Neither compression nor heating alone was sufficient to mold these polymers into new architectures, so this is a new concept in the manipulation of sulfur polymers. Additionally, high-level ab initio calculations revealed that the weakest S−S bond in organic polysulfides decreases linearly in strength from a sulfur rank of 2 to 4, but then remains constant at about 100 kJ mol⁻¹ for higher sulfur rank. This is critical information in engineering these polymers for S−S metathesis. Guided by this insight, polymer repair, recycling, and repurposing into new composites was demonstrated.     

Linear formulations and valid inequalities for a classic location problem with congestion: a robust optimization application

This study investigates a classic stochastic location problem in a service system with immobile servers that are represented by M/G/1 queues. It shows that     

Inhibition of aluminum corrosion by phthalazinone and synergistic effect of halide ion in 1.0 M HCl

The inhibitive effects of 1-(2H)-phthalazinone (PTO) for aluminum alloy (2024) corrosion in 1.0 M HCl solution and the synergistic effect of KI on the corrosion inhibition efficiency were assessed using electrochemical measurements. Results showed that the inhibition efficiency increased with an increase in concentration of the PTO and synergistically increased with addition of KI. Adsorption characteristic of PTO molecules in absence and presence of KI was approximated by Freundlich and Langmuir adsorption isotherm models, respectively. The synergistic effect is found to decrease with increase in the concentration of PTO and a competitive inhibition mechanism exists between KI and PTO cations.     

Waste generated bio-char supported co-nanoparticles of nickel and cobalt oxides for efficient adsorption of uranium and organic pollutants from industrial phosphoric acid

Journal of Radioanalytical and Nuclear Chemistry - The ultimate usage of phosphoric acid is declared in food and fertilizers industries. Therefore, purification of commercial phosphoric from their...     

Dense coating of surface mounted Cu<Subscript>2</Subscript>O nanoparticles upon silk fibers under ultrasound irradiation with antibacterial activity

The growth of Cu₂O nanoparticles on silk fibers was achieved under ultrasound irradiation. The effect of temperature, reaction time, ultrasound irradiation and solvent in growth of the Cu₂O nanoparticles upon fiber has been studied. These systems depicted a decrease in the size accompanying a decrease in the reaction time. Particle sizes and morphology of nanoparticle depend on power of ultrasound irradiation. Results show that in presence of ultrasound radiation, particle sizes are in a very low range. The susceptibility of the microorganisms to Cu₂O upon fiber was determined by minimum inhibitory concentration (MIC) using micro dilution method and disk diffusion method. Results suggest that the Cu₂O nanoparticles on silk fibers have antibacterial activity. The Cu₂O nanoparticles upon fibers were characterized with X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM). XRPD analyses indicated that the prepared Cu₂O nanoparticles on silk fibers were crystalline.