Electrochemical CO2 Reduction: Recent Advances and Current Trends

With rising levels of CO₂ in our atmosphere, technologies capable of converting CO₂ into useful products have become more valuable. The field of electrochemical CO₂ reduction is reviewed here, with sections on mechanism, formate (formic acid) production, carbon monoxide production, reduction to higher products (methanol, methane, etc.), use of flow cells, high pressure approaches, molecular catalysts, non-aqueous electrolytes, and solid oxide electrolysis cells. These diverse approaches to electrochemical CO₂ reduction are compared and contrasted, emphasizing potential processes that would be feasible for large-scale use. Although the focus is on recent reports, highlights of older reports are also included due to their important contributions to the field, particularly for high-rate electrolysis.     

Influence of filtration conditions on membrane fouling and scouring aeration effectiveness in submerged membrane bioreactors to treat municipal wastewater

Membrane fouling and scouring aeration effectiveness were studied using three large pilot-scale submerged membrane bioreactors (MBRs) operated at a series of permeate fluxes, scouring aeration intensities and cyclic aeration frequencies to treat municipal wastewater. The results showed that when operated at the sustainable conditions, the MBRs had a stable reversible fouling resistance. At unsustainable conditions, the reversible fouling resistance increased exponentially as filtration progressed. For each of above two cases, the fouling ratios newly defined by Eqs. (7) and (8) were calculated from the transmembrane pressure increases to compare the relative reversible fouling rates. With the range of sustainable filtration conditions, the fouling ratios at the same reference scouring aeration intensity were found to be proportional to permeate flux. Similarly, the fouling ratios calculated with the same reference permeate flux decreased exponentially with increasing scouring aeration intensity. Moreover, the effects of scouring aeration intensity and permeate flux on the fouling ratios were found to be independent of one another. As a result, an empirical relationship was derived to relate the stable reversible fouling resistance to sustainable permeate fluxes and scouring aeration intensities. Its application was demonstrated by constructing transmembrane pressure contours overlaid with scouring aeration effectiveness contours to aid in the selection of optimal MBR filtration conditions.     

Effects of neuropeptide Y on feeding microstructure: Dissociation of appetitive and consummatory actions.

The effects of intracerebroventricular application of Neuropeptide Y (NPY) on licking microstructure for sucrose, saccharin, and water solutions were evaluated. In Experiment 1, NPY increased meal size for three sucrose concentrations (0.03 M, 0.3 M, and 1.0 M) by increasing licking burst number but not size and by extending meals more than four-fold in duration with a slow, sustained rate of ingestion in late phases of the meal. Results are consistent with the interpretation that NPY suppressed inhibitory postingestive feedback. Experiment 2 supported this conclusion. NPY significantly increased the number of meals initiated for water, 0.1% saccharin, and 1.0 M sucrose solutions, but meal size was only increased for 1.0 M sucrose. Therefore, NPY also increased appetitive feeding behaviors, but its consummatory effects were limited to caloric solutions. The results are discussed with regard to their potential to explain current discrepancies in the literature. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An investigation of segregation and mixing in dense phase pneumatic conveying

Pneumatic conveying of bulk materials has become an important technology in many industries: from pharmaceuticals to petro-chemicals and power generation. Particulate segregation has been investigated in many solids handling processes. However, little work has been published on the segregation and mixing in pneumatic conveying pipelines, particularly in dense phase pneumatic conveying. Due to the character of dense phase flow, it is difficult to investigate the segregation in a flowing plug. A sampling device was designed and built to take samples from the pneumatic conveying pipeline after “catching a plug”. Several experiments were conducted over a range of gas–solids flow conditions with 3 mm nylon pellets and 3 mm ballotini as a segregating mixture. Experimental data combined with video footage were analysed to describe the segregation and mixing of solids plugs in pipes. This investigation provides initial research on establishing a segregation index in a flowing plug. A gas–solids two-dimensional mathematical model was developed for plug flow of a nylon-glass particulate mixture in a horizontal pipeline in dense phase pneumatic conveying. The model was developed based on the discrete element method (DEM). The model was used to simulate the motion of particles both in a homogeneous flow and as binary mixtures taking into account the various interactions between gas, particles and pipe wall. For the gas phase, the Navier Stokes equations were integrated by the semi-implicit method for pressure-linked equations (SIMPLE) using the scheme of Patankar employing the staggered grid system. For the particle motion the Newtonian equations of motion of individual particles were integrated, where repulsive and damping forces for particle collision, the gravity force, and the drag force were taken into account. For particle contact, a model with a simple non-linear spring and dash pot model for both normal and tangential components was used. This model employed a mixture of 3 mm pellets and ballotini as virtual materials with properties of nylon and glass. The results from the model are discussed and compared with experimental work and show qualitative agreement. Further modelling and experimental work in key areas is proposed.     

Effects of self-focus, discrepancy between self and standard, and outcome expectancy favorability on the tendency to match self to standard or to withdraw.

Objective self-awareness theory (S. Duval and R. A. Wicklund, 1972) assumes that the intensity of attempts to match self to standard or to withdraw is a function of degree of self–standard discrepancy. Self-regulation theory (C. S. Carver and M. F. Scheier, 1981) assumes that the decision to match or withdraw is determined by outcome expectancy favorability. Combining these assumptions, it was predicted that increasing self–standard discrepancy would increase efforts to conform self to standard when outcome expectancies are favorable. When unfavorable, increasing discrepancy was predicted to increase efforts to avoid the situation. Results from Exps 1 and 2 provided partial support for these hypotheses. Results from Exp 3 suggested that deviations from prediction were due to outcome expectancy favorability being a function of the rate of progress toward discrepancy reduction relative to the magnitude of self–standard discrepancy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition of a complex place task in rats with selective ibotenate lesions of hippocampal formation: Combined lesions of subiculum and entorhinal cortex versus hippocampus.

[Correction Notice: An erratum for this article was reported in Vol 103(1) of Behavioral Neuroscience (see record 2008-10623-001). This article's corresponding plate appears on page 995. The information should read, "Plate A. Photomicrographs of horizontal, cresyl violet stained sections at dorsal, middle, and ventral levels of the brain for an unoperated control rat (left), an animal from the Subiculum + Entorhinal lesion group (middle), and a rat from the hippocampus group (right)."] The effects of isolating the hippocampus from its neocortical inputs and outputs by damaging the deep layers of entorhinal cortex and subiculum were compared with direct removal of the hippocampus using acquisition of a complex radial maze task. A series of eight problems (four out of eight arms being correct) were learned under either massed (45 s) or distributed (10 min) practice conditions, thus varying contextual information. Performance of rats with subiculum/entorhinal cortex lesions was similar to that of controls in all aspects of the radial maze task; whereas animals with hippocampal lesions were impaired on nearly all dependent measures. Although the effects of varying the intertrial interval were generally small, distributed practice did serve to facilitate the performance of hippocampal rats in terms of working memory. These findings are discussed as they related to recent theorizing in the area. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Study on a large-scale discrete element model for fine particles in a fluidized bed

The discrete element method (DEM) is widely used to comprehend complicated phenomena such as gas–solid flows. This is because the DEM enables us to investigate the characteristics of the granular flow at the particle level. The DEM is a Lagrangian approach where each individual particle is calculated based on Newton’s second law of motion. However, it is difficult to use the DEM to model industrial powder processes, where over a billion particles are dealt with, because the calculation cost becomes too expensive when the number of particles is huge. To solve this issue, we have developed a coarse grain model to simulate the non-cohesive particle behavior in large-scale powder systems. The coarse grain particle represents a group of original particles. Accordingly, the coarse grain model makes it possible to perform the simulations by using a smaller number of calculated particles than are physically present. As might be expected, handling of fine particles involving cohesive force is often required in industry. In the present study, we evolved the coarse grain model to simulate these fine particles. Numerical simulations were performed to show the adequacy of this model in a fluidized bed, which is a typical gas–solid flow situation. The results obtained from our model and for the original particle systems were compared in terms of the transient change of the bed height and pressure drop. The new model can simulate the original particle behavior accurately.     

Comparison of mixed liquor filterability measured with bench and pilot-scale membrane bioreactors.

Parallel experimental tests to measure mixed liquor filterability for submerged membrane bioreactors were conducted over a six month period using three ZW-500 pilot plants and a ZW-10 lab-scale filterability apparatus. Non-air sparged conditions during the tests yielded operation behaviour that was equivalent to dead-end filtration. The fouling resistance increased linearly with the intercepted mass until a critical point was reached at which point significant cake compression was induced and the resistance began to increase exponentially. Although the point of cake compression appears to be dependent on the membrane module design, similar resistance per unit solid mass intercepted per unit area (R(mass)) values were observed when the same mixed liquor was filtered. Coupled with the established correlation between the R(mass) and the critical flux, it is suggested that the filterability test results from a side-stream, lab-scale module may be used to predict fouling potential in a full scale MBR wastewater treatment system without interrupting the full-scale MBR operation.     

Temporal and Qualitative Dynamics of Conditioned Taste Aversion Processing: Combined Generalization Testing and Licking Microstructure Analysis.

The pattern of licking microstructure during various phases of a conditioned taste aversion (CTA) was evaluated. In Experiment 1, rats ingested lithium chloride (LiCl) for 3 trials and were then offered sodium chloride (NaCl) or sucrose on 3 trials. A CTA to LiCl developed and generalized to NaCl but not to sucrose. CTA intake suppression was characterized by reductions in burst size, average ingestion rate, and intraburst lick rate, and increases in brief pauses and burst counts. Compared with previous studies, LiCl licking shifted from a pattern initially matching that for normally accepted NaCl to one matching licking for normally avoided quinine hydrochloride by the end of the 1st acquisition trial. In Experiment 2, a novel paradigm was developed to show that rats expressed CTA generalization within 9 min of their first LiCl access. These results suggest that licking microstructure analysis can be used to assay changes in hedonic evaluation caused by treatments that produce aversive states. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temperature responsive polymers as multiple function reagents in mineral processing

A processing scheme which uses a single chemical that has multiple functions to achieve both efficient mineral flotation and solids dewatering is presented. Temperature sensitive polymers which display hydrophilic/hydrophobic transitions in response to changes in temperature such as poly (N-isopropyl acrylamide) (PNIPAM) have been found to be useful as such multiple function reagents. This polymer can cause the mineral particles’ surfaces to be hydrophilic at temperature below the critical solution temperature (CST = 32 °C) and hydrophobic at temperature above the CST. Therefore, both particle surface wettability and inter-particle interaction forces are reversibly controllable. When the surface is hydrophilic, particle dispersion is achieved by repulsive inter-particle forces whereas when the surface is hydrophobic, particle aggregation is induced by inter-particle hydrophobic attractive forces. In addition, the hydrophobic surface condition allows for the attachment of particles to bubbles. Flotation and solid settling tests have been conducted with silica and kaolinite suspensions treated with (PNIPAM). Both effective suspension dispersion or hydrophobic aggregation and flotation without any additional collector have been demonstrated. In solid/liquid separation, rapid settling was obtained with hydrophobic aggregation at temperature above the CST and further sediment consolidation (and water release) occurred at temperature below the CST. The approach has the potential to reduce the amount and types of reagents required for mineral processing.