Coarse‐grained models for frontal photopolymerization with evolving conversion profile

We introduce a series of ‘minimal’ models to describe a common light‐driven directional solidification process, known as frontal photopolymerization (FPP ), focusing on experimental observables: the solidification kinetics, light attenuation and spatiotemporal monomer‐to‐polymer conversion. Specifically, we focus on FPP propagation that yields conversion profiles that are not invariant with time, and which cannot be simply described by the presence of mass or heat diffusion. The models are assessed against experimental data for the photopolymerization of a model trimethacrylate system. We find that the simplest model, comprising a single equation of motion for the conversion fraction ? and a generalized Beer–Lambert law, can only describe the experimental data by assuming an unphysical variation in optical absorption. Introducing a ? ‐dependent reaction constant K _eff is found to require a time dependence, regardless of the functional form in ? . We conclude by introducing a ‘minimal’ chemical model, which is based on a simple three‐step reaction scheme involving the spatiotemporal evolution of the photoinitiator fraction, relative fraction of radicals and monomer conversion fraction, that is able to capture the experimental data with a small number of parameters and under reasonable FPP assumptions. Our framework provides important predictive ability for ubiquitous solidification and patterning processes, including three‐dimensional printing, via photopolymerization. © 2017 Society of Chemical Industry     

Social problem solving and community integration in postacute rehabilitation outpatients with traumatic brain injury.

Objective: To enhance understanding of the role that social problem solving (SPS) plays in community integration following traumatic brain injury (TBI). Study Design: Regression analysis. Participants: Forty-five adults with TBI participating in higher level outpatient cognitive rehabilitation and 15 uninjured adults. Main Outcome Measures: Measures of community integration, problem-solving ability, and SPS self-appraisal and performance. Results: Individuals with TBI demonstrated poorer problem-solving as measured by both neuropsychological and SPS methods; however, the largest effect' size was observed for SPS self-appraisal. Only SPS self-appraisal predicted a significant proportion of the variance in community integration. Conclusions: It is important to assess brain-injured persons' confidence in their ability to cope with problems. A focus on objective test scores alone may lead to underdetection of disabling problem-solving deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nanoporous Silver Thin Films: Multifunctional Platforms for Influencing Chain Morphology and Optical Properties of Conjugated Polymers

Disordered nanoporous silver (NPAg) thin films fabricated by a thermally assisted dewetting method are employed as a platform to influence chain alignment, morphology, and optical properties of three well‐known conjugated polymers. Grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) measurements show that the porous structure of the metal induces close π–π stacking of poly(3‐hexylthiophene) (P3HT) chains and extended, planar chain conformations of poly(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl) (PFO) and poly[(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl)‐alt‐(benzo[2,1,3]thiadiazol‐4,8‐diyl)] (F8BT). A greater degree of vertically‐oriented P3HT chains are found on NPAg compared with planar Ag. However, PFO and F8BT chain alignment is only affected when pore size is large. The optical properties of NPAg films are investigated by transmission and back‐scattering spectroscopies. Strong back‐scattering is observed for all NPAg morphologies, especially for NPAg with small pore sizes. Photoluminescence spectroscopy of conjugated polymer layers on NPAg showed pronounced emission enhancements (up to factors of 26) relative to layers on glass. The enhancements are attributed primarily to: 1) redistribution of conjugated polymer emission by Ag; 2) redirection of emission by polymer‐filled nanopores; and 3) local electromagnetic field effects. This work demonstrates the potential of NPAg‐thin films to influence molecular chain morphology and to improve light‐extraction in organic optoelectronic devices.     

Computer technology and architecture: an evolving interaction

The interaction between computer architecture and IC technology is examined. To evaluate the attractiveness of particular technologies, computer designs are assessed primarily on the basis of performance and cost. The focus is mainly on CPU performance, both because it is easier to measure and because the impact of technology is most easily seen in the CPU. The technology trends discussed concern memory size, design complexity and time, and design scaling. Architectural trends in the areas of pipelining, memory systems, and multiprocessing are considered. Opportunities and problems to be solved in the years ahead are identified     

Textile Waste Waters: Treatment and Environmental Effects

The paper considers the use of water and chemicals in the textile industry and the volume, nature and composition of process effluents, the effect they have on the environment and the limitations they pose on the reuse of water. An outline is given of the methods available for treatment of waste waters from the industry, on site or at a Water Authority's works and the effects that chemical constituents of the effluents have on the treatment processes and on disposal of water and sludge. The assessment and significance of biodegradability and the extent of present-day knowledge on the biodegradability of the main classes of chemicals used in textile processing are discussed. The paper concludes with a section dealing with the removal of colour from waste waters.     

Mechanically stabilized walls over soft clay: Geosynthetic to prevent deep-seated failures

Mechanically stabilized walls can sometimes be economically constructed over poor foundations such as a soft clay. A major design concern in such a case, however, is the stability against deep-seated failure where the potential slip surface passes through the unreinforced backfill and the clayey foundation. To attain a prescribed safety margin against deep-seated instability, a high-strength geosynthetic sheet, placed at the backfill-clay interface, can be used. The objective of this paper is to present an analysis method which enables the user to determine the required distribution of tensile resistance of the reinforcing sheet and therefore can be used as a design tool. The analysis is based on limit-equilibrium and by virtue of the mechanism used it is rigorous in the sense that no statical assumptions are utilized. Its predictions compare favorably with some conventional methods; its application, however, is easier. It is demonstrated how the analysis results can be condensed into a useful format of design charts. Since the direction of the reinforcement's tensile resistance is not known, a zone is suggested within which is the probably required distribution of this force.     

Learning theory: Two trials and tribulations.

Conducted a series of experiments to demonstrate that organisms tend not to repeat a response after reinforcement is "consumed," contrary to the basic tenet of learning theory. Using varied combinations of Ss, including college sophomores, nurses, children, and "real people," and varying apparatus from a black box to paper cups, the hypothesis was confirmed. Additional hypotheses were developed relating to naivete, expectancies of deception, and elaborate instrumentation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)