Particle aggregation rate in a microchannel due to a dilute suspension flow

Particle-laden flow in a microchannel results in cluster formation and growth on the channel surface and the cluster growth, due to aggregation of polystyrene microparticles, has been investigated in this study. In particular, the initial stage of cluster growth is examined, where particle–cluster interaction is the dominant growth mechanism. Both experimental measurements and theoretical considerations were utilized to explore the functional dependence of the cluster growth rate on the following parameters: suspension void fraction, flow shear strain rate, and channel-height to particle-diameter ratio. The growth rate of an average cluster is found to increase linearly with suspension void fraction which is consistent with previous reports. The growth rate coefficient is found to obey a power-law relationship with respect to the shear strain rate, and predictions based on the modernized flocculation theory agree well with the experimental results. Furthermore, the growth rate coefficient obeys a power-law relationship with respect to the channel-height to particle-diameter ratio as well, qualitatively similar to other reported studies. However, to our knowledge, the exponent value estimated in this study does not agree with any previously published values; this disagreement is likely due to differences in experimental conditions.     

The initial stage of high‐pressure induced β‐lactoglobulin aggregation: the long‐run simulation

Research objective of this study was to clarify how the initial stage of high‐pressure induced aggregation of β‐lactoglobulin takes place. For this purpose a special simulation method was developed. Distinctive features of this approach are: the lowest resolution model of protein particles, the local interaction potential and the abandonment of the continuous simulation of particle trajectories. Relatively short molecular dynamics trajectories are used only in order to find the average time step between the collisions. Results of particle collisions that occur with some probability, are separately (‘statically’) modelled using a random variable. This allows the analysis of the process which takes place within 10²–10³ s real‐time, with an existing probability of successful collision of 10^?10–10^?11. Modelling results confirm that at the initial stage of aggregation of 0.5–2% solutions with a neutral pH‐value only dimers as well as trimers arise due to SH/S–S interaction. In addition it was shown that aggregation follows the general principles of the reaction‐limited aggregation of colloids. The proposed approach could further be used in research projects examining the aggregation of β‐lactoglobulin or similar systems.     

Multi-physics design and optimization of flexible matrix composite driveshafts

Flexible matrix composites (FMCs) consist of low modulus elastomers such as polyurethanes which are reinforced with high-stiffness continuous fibers such as carbon. This fiber–resin system is more compliant compared to typical rigid matrix composites and hence allows for higher design flexibility. Continuous, single-piece FMC driveshafts can be used for helicopter applications. In the present investigation, an optimization tool using a genetic algorithm approach is developed to determine the best combination of stacking sequence, number of plies and number of in-span bearings for a minimum-weight, spinning, misaligned FMC helicopter driveshaft. In order to gain more insight into designing driveshafts, various loading scenarios are analyzed and the effect of misalignment of the shaft is investigated. This is the first time that a self-heating analysis of a driveshaft with frequency- and temperature-dependent material properties is incorporated within a design optimization model.     

Lycopene extraction from extruded products containing tomato skin

To determine the lycopene content of extruded products containing 10% tomato skin, the conditions for solvent extraction were optimised. After three extraction cycles at 50 °C each for 15 min at a solvent to meal ratio of 40:1, a maximum of 6.6 ppm lycopene was extracted. However, the extraction was considered incomplete, thus the product was digested by pancreatin prior to extraction. The extracted lycopene content was increased to 23.5 ppm using the optimum conditions of 20 min of digestion with 10 mg mL^?1 pancreatin. To validate the extraction efficiency at optimum conditions, a set of extruded products containing different lycopene concentrations was used. Digestion increased the extracted lycopene content by more than 2.5‐fold between the products. Furthermore, this inclusion significantly improved the correlation coefficient between the red colour and the extracted lycopene content. Therefore, including a digestion step prior to extraction by solvents was necessary to efficiently extract lycopene from extruded products.     

Lack of international consensus on the disposition and storage of disused sealed sources

A lower-activity analogue of the trans-national problem of spent fuel management and disposal is the global problem of radioactive sealed source [source: The IAEA definition of a sealed source is “Radioactive material that is permanently sealed in a capsule or closely bonded and in a solid form.” Taken from glossary of Nuclear Waste Data Management found at http://www-ewmdb.iaea.org/showhelp.asp?Topic=8-1-1.] disposal. Sources are found in almost every country in the world because of their beneficial medical and commercial or industrial applications. Some of the isotopes used have short half-lives—iridium-192 (Ir-192), 73.8 days—while others have very long half-lives—americium-241 (Am-241), 432 years or plutonium-239 (Pu-239), 24,130 years. It is critically important, particularly for longer-lived isotopes, to find final disposition pathways. Lack of a permanent disposition pathway such as recycling or irretrievable disposal creates numerous problems, including the potential loss of regulatory control, which increases the risk of inadvertent or deliberate misuse of the material.The misuse of radioactive materials has the potential for substantial public health and economic damage. Disused sources also pose an inherent risk to the end-users from a liability, safety, and public health perspectives. This paper examines various disposition pathways employed by several key source manufacturing or possessing nation-states for disused sources. Examples of source disposition pathways include long-term storage, deep geological disposal, borehole disposal and shallow land burial. The Off-Site Source Recovery Project (OSRP), part of the office of Global Threat Reduction Initiative (GTRI), acts as an intermediary in the recovery and ultimate disposition of US origin sealed radiological materials. Several concepts that could help mitigate the challenge of a lack of long-term disposition options for sources are available, but these tools have not yet been applied by most nation-states. For example, regional consolidation and repatriation of sources to the country of manufacture would ease or eliminate the need for in situ disposal or storage in a number of developing nation-states.     

Internal friction of the glassy tektites

Tektites are naturally occurring glasses, perhaps of meteoritic origin. They occur all over the world. They range in size from μm to decimeter. They are based on the compounds silica and alumina, with smaller concentrations of alkali metal and transition metal oxides. Their origin is in vigorous dispute; some scientists think they are of terrestrial earth origin, others believe they come from interplanetary space, as is true of meteorites. We have secured seven specimens from various regions of the earth and have measured the internal friction spectrum of several in the kilocycle frequency range above room temperature, where internal friction peaks of synthetic glasses have been observed. A well defined loss peak is observed around 500 K in a number of specimens. We have also measured the loss spectrum of obsidian and of blast furnace slag. From comparison of these measurements, we conclude that tektites are probably of volcanic origin, the loss peaks being associated with the reorientation of Fe–oxygen complexes.     

Judgment under emotional certainty and uncertainty: The effects of specific emotions on information processing.

The authors argued that emotions characterized by certainty appraisals promote heuristic processing whereas emotions characterized by uncertainty appraisals result in systematic processing. The 1st experiment demonstrated that the certainty associated with an emotion affects the certainty experienced in subsequent situations. The next 3 experiments investigated effects on processing of emotions associated with certainty and uncertainty. Compared with emotions associated with uncertainty, emotions associated with certainty resulted in greater reliance on the expertise of a source of a persuasive message in Experiment 2, more stereotyping in Experiment 3, and less attention to argument quality in Experiment 4. In contrast to previous theories linking valence and processing, these findings suggest that the certainty appraisal content of emotions is also important in determining whether people engage in systematic or heuristic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Resuspension of Particulate Matter from Carpet Due to Human Activity

This work investigated the resuspension and subsequent translocation of particulate matter (PM) from carpeted flooring surfaces due to walking. In addition, the effect of HVAC systems and ceiling fans on mixing and/or translocation of resuspended PM was studied. Testing took place both in a residence with a well-worn, soiled carpet and in an environmental test chamber. Prescribed walking occurred with PM measurements taken at multiple sampling heights. Scanning electron microscopy (SEM) of carpet fibers was used to determine the fraction of dust available for resuspension. These data, in conjunction with resuspended mass concentrations from this study, were used to generate emission factors by particle size for walking on both new and worn carpet.

Carpet loading does not affect the emission factor, indicating that the amount of resuspended PM is directly proportional to the available PM in the carpet. While relative humidity (RH) plays an important role in resuspension from new carpets, with high RH enhancing resuspension, it has the opposite affect with old carpets, with increased RH decreasing resuspension. With the HVAC system on, translocated particles 1.2 m horizontally from the source had number concentrations of approximately 20–40% of those at the source. With a ceiling fan on, extensive mixing was noted with little difference seen in particle resuspension by height. With the ceiling fan off, there was very little mixing present and particle size varied substantially by height.