Rheological properties and structure of step‐ and chain‐growth gels concentrated above the overlap concentration

Cross‐linked polymeric gels are widely used in applications ranging from biomaterial scaffolds to additives in enhanced oil recovery. Despite this, fundamental understanding of the effect of polymer concentration and reaction mechanism on the scaffold structure is lacking. We measure scaffold properties and structure during gelation using multiple particle tracking microrheology. To determine the effect of concentration, we measure gelation as polymer interactions are increased in the backbone precursor solution: below, at and above the overlap concentration, . To determine structural changes due to the gelation mechanism, we measure gelation between the same polymers undergoing both step‐ and chain‐growth reactions using self‐assembling maleimide:thiol and photo‐initiated acrylate:thiol chemistries, respectively. We determine the critical relaxation exponent, n, a measure of structure. n decreases with increasing concentration, indicating a change from a percolated ( ) to a tightly cross‐linked network ( ). The gelation mechanism does not have a measurable effect on the scaffold structure. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3168–3176, 2018     

西雅图某休息厅室内设计

“Posh”这个词是用来表述优雅和时尚，内在魅力和翩翩的风度，贝尔城地区是西雅图的明珠，这个混凝土的丛林实现了新生活方式的起点和不同于主流的购物环境，提供的服务包括个性的服饰，各国美味，现代风格的俱乐部和家庭风格的咖啡，我的理想是在休息厅设计中实现这种豪华的味道，体现出高贵感受。     

Use of Ozone for Disinfection and Taste and Odor Control at Proposed Membrane Facility

Zone 7 of Alameda County Flood Control and Water Conservation District, in coordination with Black & Veatch, conducted a 9-month pilot study to determine preliminary design parameters for a new water treatment plant (WTP). The pilot study was performed to verify the performance of membrane filters and to establish preliminary design parameters for the submerged membrane process, followed by ozonation and biological granular activated carbon filtration. The pilot testing was conducted using water from the Patterson Pass WTP reservoir. The process included coagulation with either ferric chloride or polyaluminum chloride, flocculation, sedimentation, membrane filtration, ozonation, and filtration using biological granular activated carbon (BAC). The goals of the study were as follows:

1. Determine the potential effectiveness of ozone and BAC for removing geosmin and MIB.

2. Determine the impacts of different levels of pathogen inactivation, i.e., 0.5-log Giardia and 2-log virus inactivation.

3. Monitor the formation of bromate under various conditions of ozone oxidation for different levels of pathogen inactivation as well as for taste and odor control, and evaluate bromate mitigation strategies, if necessary.

The results of the study showed that the use of ozone achieved 2.0-log virus inactivation and 0.5-log Giardia inactivation. It also decreased the disinfection by-product formation and effectively controlled geosmin and removed a significant fraction of the MIB during a taste and odor event. Because the raw water bromide concentrations were low, bromate formation remained below the regulated level of 0.010 mg/L. However, in one instance, bromate mitigation was utilized by applying sulfuric acid to lower the pH to less than 7.1, which reduced bromate formation to less than 0.010 mg/L.     

Molecular-level composition design for efficient synthesis of SiAlON ceramics

SiAlONs are a class of liquid-phase sintered ceramics with excellent room-temperature strength and toughness, but whose residual grain boundary glass softens at high temperatures, limiting use in extreme environments. For this reason, efforts are made to minimize the volume of the grain boundary glass while still facilitating full densification. This work describes a potential route for the densification of SiAlONs with very low concentrations of liquid-phase sintering additive (e.g., rare-earth oxides such as yttria) by using an organometallic precursor. Solid solution of Al and O in the Si₃N₄ lattice was accomplished through the incorporation of solute atoms via liquid organic precursor aluminum sec-butoxide (ASB). Al₂O₃ powder is conventionally used for this purpose, and the subsequent lattice softening associated with the solid solution helps to facilitate densification. However, a liquid-phase additive is still essential for the full densification of SiAlONs. Higher densities were obtained from SiAlON powder blends utilizing organometallic ASB than those utilizing alumina powder, allowing for greater densification at very low Y₂O₃ concentrations. The thermal decomposition of the organic precursor was investigated by high-temperature scanning electron microscopy, thermogravimetric analysis, and various X-ray diffraction experiments. Immersion density measurements and lattice parameter refinements were performed for samples sintered with varying Y₂O₃ concentrations and/or dwell times. Results indicate that ASB-containing powder blends favor SiAlON formation more strongly than Al₂O₃-containing powder blends and favor densification at very low Y₂O₃ concentration.     

Multimodal Characterization of Crystal Structure and Formation in Rubrene Thin Films Reveals Erasure of Orientational Discontinuities

Multimodal multiscale characterization provide opportunities to study organic semiconducting thin films with multiple length scales, across multiple platforms, to elucidate crystallization mechanisms of the various microstructures that impact functionality. With polarized scanning transmission X-ray and 4D-scanning transmission electron microscopy, hybrid crystalline structures in rubrene thin films in which large crystalline domains surround a common nucleus and transition to a spherulite morphology at larger radii is observed. These high-resolution techniques reveal how azimuthal orientational discontinuities at smaller radii are erased as spherulite morphology takes hold. In situ crystallization in the films with optical microscopy is also captured, discovering the importance of considering the initial temperature increase of a film during thermal annealing over the crystallization timescale. This kinetic information of the radial crystallization rate and of corresponding film heating kinetics is used to estimate the temperature at which the larger crystalline regions transition into a spherulite. By combining the results obtained from the different characterization modes, it is learned that thermal conditions can sensitively affect the crystallization of rubrene and other organic thin films. The observations suggest opportunities for more complex temperature-dependent processing to maximize hybrid structures’ functionality in organic thin films and demonstrate that multimodal studies deepen the understanding of structure-function dynamics.