Spray deposited fluoropolymer/multi-walled carbon nanotube composite films with high dielectric permittivity at low percolation threshold

High performance perfluoro alkoxy (PFA) and chemical vapor deposition-grown multi-walled carbon nanotube (MWCNT) composite films with thicknesses of 30 μm were prepared using a scalable spray deposition technique. A homogeneous distribution of MWCNTs within the PFA matrix was confirmed by electron and optical microscopy. Dielectric and AC conductivity measurements showed a significant enhancement of dielectric permittivity for PFA/MWCNT films at low frequencies, and a very weak dependence of dielectric permittivity on temperature in the range 25-230 °C. Very low percolation threshold volume fractions of ca. 0.0043 and 0.0017 were attained for MWCNTs with two different aspect ratios, which have been explained by an inherent feature of spray route, a microcapacitor model and percolation theory. The combination of PFA/MWCNT composites and the spray deposition route provides a promising approach for the fabrication of industrial scale composite films with well-controlled dielectric properties for micro-electronic and high temperature applications.     

An experimental investigation of ion-drag pump in a vertical andaxisymmetric configuration

An ion-drag pump in a vertical, axisymmetric configuration was built. Two pumping sections with 1 and 10 electrode pairs were constructed. The total length of the pumping loop with one electrode pair was 133.0 cm; with 10 electrode pairs it was 186.0 cm. The electrodes were designed from the fluid mechanics standpoint. The ions were injected into the fluid where the viscous shear stresses were the highest. The fluid used was dodecylbenzine, and all the experiments were conducted at 25°C. Pumping velocities as high as 33.4 cm/s (corresponding mass flow rate of 1.1 kg/s and total pressure generation of 111.9 Pa) at 25 kV have been achieved. The highest pump power efficiency obtained was 6.0%. The effect of the electrical conductivity level of dodecylbenzine on the pump performance was also studied. Increasing the conductivity level reduced the pumping velocity     

Salt recovery from agricultural drainage water using a liquid film solar-assisted concentrator – Simulation and model validation

Salt management in irrigated agriculture is critical to the economies of the San Joaquin Valley of California and many other areas around the world. Purified salts can be recovered as marketable products through fractional crystallization following concentration of final stage drainage water from integrated on-farm drainage management systems. To obtain recovered salt and use as a commercial product, new systems which can perform with higher efficiency and lower environmental impact than solar evaporation basins or solar ponds that have previously been used for the final stage are in need of development. For this purpose, a number of solar-assisted brine concentration concepts have been explored, including an open liquid film-type using a tilted evaporation surface described here. Model performance was conceptually evaluated and then experimentally verified.A transient model was developed from energy and component mass balances and employed constitutive heat and mass transfer relationships from various other sources for simulating concentration of agricultural drainage water using a liquid film solar-assisted concentrator.Measured maximum evaporation rate and productivity were between 1.3 and 1.5 kg m⁻² h⁻¹, and 80 kg m⁻² over a 7 day experimental period respectively which was about a third better performance compared with a shallow basin horizontal concentrator. Measurements were in good agreement with model predictions: within 2 °C at the peak and 4 °C at the lowest evaporation, and 0.2 kg m⁻² h⁻¹ for evaporation rates during the peak evaporation periods of the day when compared with independent data sets. Cumulative evaporation rates were from 75 to 85 kg m⁻² for the tilted concentrator model and 60 to 65 kg m⁻² for the horizontal concentrator model after 7 days. The tilted concentrator yielded productivity and efficiency that were 33% higher than the horizontal concentrator according to the experimental result for the same period and location.     

Early observations on an emerging Great Lakes invader Hemimysis anomala in Lake Ontario

Hemimysis anomala, a Ponto-Caspian littoral mysid, is an emerging Great Lakes invader that was discovered in Lakes Michigan and Ontario in 2006. Similar to the native mysid Mysis diluviana, Hemimysis exhibits a diel vertical migration pattern but generally inhabits shallower and warmer waters than M. diluviana. Because basic information on the distribution, habitat use, and biology of Hemimysis in the Great Lakes is scarce, the potential for food web disruption by Hemimysis cannot easily be predicted. Preliminary observations indicate widespread invasion of Hemimysis in Lake Ontario. In this study, we confirm the presence of Hemimysis at sites spanning the northern and southern shores of Lake Ontario and the presence of the individuals during winter months. In one horizontal tow in November 2007, over 26,000 individuals were collected with a length range of 4.4 to 9.0 mm and an average caloric density of 611 cal/g wet weight. The most effective methods for sampling Hemimysis were horizontal tows with either a zooplankton net in the water column or a benthic sled near the lake bottom. Although more quantitative data on the life history and distribution of this species is necessary, our preliminary observations support the prediction that the potential for Hemimysis to impact the nearshore food web in Lake Ontario appears high.     

Effects of externally-generated electrons on pressure measurements of inverted magnetron gauges at Diamond

Diamond Light Source (Diamond) utilises a large number of Inverted Magnetron Gauges (IMGs) for both monitoring the vacuum and as a source of interlocks for protection of the machine. During storage ring operation it has been found that, in the presence of the stored electron beam, charged particles, assumed to be electrons, impinging on some of the gauges cause the pressures indicated by the gauges to drop to zero which causes problems with the operation of the storage ring. Diamond has designed and fitted a magnetic filter at the neck of each affected gauge port to eliminate this problem. This paper reports on and discusses experiments and proposed experiments with an electron flood gun and IMGs from two different manufacturers (MKS Instruments and Pfeiffer Vacuum) aimed at obtaining a better understanding of the effect. Externally-generated electrons from the flood gun can cause serious errors in the pressures indicated by the gauges; the error can be positive or negative depending on the gauge current-measuring circuit. Methods aimed at eliminating these spurious pressure readings, such as magnetic filters, bias voltages within the gauges and the use of earth meshes and baffles are also discussed.     

Work stressors, role-based performance, and the moderating influence of organizational support.

As a test of the 2-dimensional model of work stressors, the present study proposed differential relationships between challenge stressors and hindrance stressors and role-based performance, which were expected to be moderated by organizational support. In a sample of 215 employees across 61 offices of a state agency, the authors obtained a positive relationship between challenge stressors and role-based performance and a negative relationship between hindrance stressors and role-based performance. In addition, organizational support moderated the relationship between challenge stressors and role-based performance but did not moderate the relationship between hindrance stressors and role-based performance. This suggests that organizations would benefit from increasing challenges in the workplace as long as they are supportive of employees and removing hindrances. Further implications for organizational theory and practice are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assessing the impact of swales on receiving water quality

Swales are one type of sustainable drainage system (SuDS) which contribute to the management of water quality in receiving waterbodies. Using a semi-quantitative approach, an impact assessment procedure is applied to the residual water quality that is carried forward to surface waters and groundwaters following treatment within a swale. Both volumetric and pollutant distributions are considered as stormwater passes through the swale system. The pollutant pathways followed by TSS, nitrate, chloride, metals (Cd, Cu, Pb, Zn) and polyaromatic hydrocarbons (PAHs) are determined for a swale receiving highway runoff. For TSS, metals and PAHs between 20% and 29% of the total mean influent pollutant load is predicted to be directed to infiltration through the underlying soils compared to between 4% and 16% of chloride and nitrate. Although surface water impacts are deemed possible, the discharges of swales to groundwaters are assessed to represent a negligible impact for effectively maintained systems.     

Performance of four salmonids species in competition with Atlantic salmon

Economically and culturally important salmonid species often compete with Atlantic salmon (Salmo salar) released from stocking programs or that escaped during aquaculture production. Such competitive interactions may lower the individual fitness of these species by reducing survival and body growth. Here, we exposed juvenile brown trout (S. trutta), rainbow trout (Oncorhynchus mykiss), Chinook salmon (O. tshawytscha), and coho salmon (O. kisutch) to juvenile Atlantic salmon in artificial streams for 10 months. Survival and fitness-related traits of the four species were not negatively impacted by the presence of Atlantic salmon. The results suggest that brown trout and rainbow trout have better competitive abilities than Atlantic salmon, and that Chinook salmon and coho salmon have limited competitive interactions with Atlantic salmon. Although we discuss certain environmental conditions that can favor Atlantic salmon as a competitor at the juvenile life stage, Atlantic salmon may have little impact on the productivity of these four species.