Ceramic Foams with Controlled Geometries Through 3D-Printed Sacrificial Templates

Powder-based 3D printing was combined with sacrificial templating to realize highly porous yttria-stabilized ZrO₂ (YSZ) ceramic foam objects with well-defined geometries. The porous sacrificial template is 3D printed using poly(methyl methacrylate) powder. Various methods are evaluated to optimize ceramic slurry infiltration into the 3D-printed template and subsequent burn-out. The optimized method yields ceramic foam objects with an open porosity of >66% and replicates the geometry of the 3D-printed template with high fidelity.     

Physiologically-Based Kinetic Modeling of Intravenously Administered Gold (Au) Nanoparticles

Physiologically-based kinetic (PBK) modeling is a valuable tool to understand the kinetics of nanoparticles (NPs) in vivo. However, estimating PBK parameters remains challenging and commonly requires animal studies. To develop predictive models to estimate PBK parameter values based on NP characteristics, a database containing PBK parameter values and corresponding NP characteristics is needed. As a first step toward this objective, this study estimates PBK parameters for gold NPs (AuNPs) and provides a comparison of two different NPs. Two animal experiments are conducted in which varying doses of AuNPs attached with polyethylene glycol (PEG) are administered intravenously to rats. The resulting Au concentrations are used to estimate PBK model parameters. The parameters are compared with PBK parameters previously estimated for poly(alkyl cyanoacrylate) NPs loaded with cabazitaxel and for LipImage 815. This study shows that a small initial database of PBK parameters collected for three NPs is already sufficient to formulate new hypotheses on NP characteristics that may be predictive of PBK parameter values. Further research should focus on developing a larger database and on developing quantitative models to predict PBK parameter values.     

Book reviews

Urban Policy Evaluation: Challenge and Change. R. Hambleton & H. Thomas (Eds). Liverpool, Paul Chapman, 1995, 258 pp., £17.95 ISBN 1–85396–271–6

Environmental Strategy and Sustainable Development. R. Welford. Routledge, London, 1995, 217 pp, £12.99, ISBN 0–415–10552–8

Urban Agriculture in Zimbabwe. B. Mbiba. Ashgate, Aldershot, UK and Brookfield, VT, 1995, £35.00, ISBN 185628 857 9

Housing Women. Rose Gilroy & Roberta Woods (Eds.). London, Routledge, 1994, 304 pp., £14.99, ISBN 0–415–09463–1

Census User's Handbook. S. Openshaw (Ed.). Longmans, 1995, 454 pp., £19.95, ISBN 0–470234–814

Reconstituting Rurality. J. Murdoch & T. Marsden. London, UCL Press, 1994, 272 pp., £40.00, ISBN 1–85728–041–5

Development and Administration of Prague. M. Barlow, P. Dostal, & M. Hampl (Eds). Amsterdam, Instituut voor Sociale Geographie, Universiteit van Amsterdam, 1994, 170 pp., 35DG, ISBN 9–06993–086‐Z

Local Development, Restructuring, Locality and Local Initiative in Portugal. S. Syrett. Aldershot, Avebury, 1995, 371 pp., £40.00, ISBN 1 85628 484 0     

Removal of THM precursors by coagulation or ion exchange

The removal of natural organic matter (NOM) from drinking water supplies can be achieved by different processes, among them coagulation and adsorption. Synthetic waters made from concentrates of humic substances from reservoir and river waters were tested in the laboratory for ease of removal of NOM by coagulation with cationic organic polymers and with alum, and by adsorption on anion exchangers. For polymers such as high molecular weight polydiallyldimethylammonium chloride (polyDADMAC) and cationic polyacrylamides of high charge, performance was nearly as effective as alum, with colour removals 86–100% of those obtained for alum. Ion exchange using the best commercially available resins designed for this purpose, a gel polystyrene and a macroporous acrylic resin, was more effective than alum treatment for two of the natural waters studied, but inferior for a third. The resins were overall superior to cationic polymers.

The NOM was separated into four fractions based on hydrophobic and hydrophilic properties. Alum was not as effective as ion exchange for the elimination of individual ionic NOM fractions. It was better than cationic polymers for removal of humic and fulvic acids, although polyDADMAC was as good for one water. For the removal of charged compounds alum then polyDADMAC were the best performers for that water. Unequivocal evidence was obtained that coagulants remove material that is not adsorbed by resins, and vice versa. A combination of coagulation with a cationic polymer and adsorption by an anion exchanger removed essentially all of the NOM. The preference of the coagulants was for the larger, more hydrophobic molecules, and of resins for smaller highly charged hydrophilic molecules. Each fraction had trihalomethane formation potentials in the range 11–24 μg/mg, except for one water that was more reactive. Hence, the actual amount of each fraction in the original water becomes a crucial factor.     

Modelling bacterial water quality in streams draining pastoral land

A model has been developed to predict concentrations of the faecal bacteria indicator E. coli in streams draining grazed hill-country in New Zealand. The long-term aim of the modelling is to assess effects of land management upon faecal contamination and, in the short term, to provide a framework for field-based research. A daily record of grazing livestock is used to estimate E. coli inputs to a catchment, and transport of bacteria to the stream network is simulated within surface and subsurface flows. Deposition of E. coli directly to streams is incorporated where cattle have access to them, and areas of permanent saturation ('seepage zones') are also represented. Bacteria are routed down the stream network and in-stream processes of deposition and entrainment are simulated. Die-off, both on land and in water, is simulated as a function of temperature and solar radiation. The model broadly reproduces observed E. coli concentrations in a hill-country catchment grazed by sheep and beef cattle, although uncertainty exists with a number of the processes represented. The model is sensitive to the distance over which surface runoff delivers bacteria to a stream and the amount of excretion direct to streams and onto seepage zones. Scenario analysis suggests that riparian buffer strips may improve bacterial water quality both by eliminating livestock defaecation in and near streams, and by trapping of bacteria by the riparian vegetation.     

Co-evolution of waste and electricity regimes: Multi-regime dynamics in the Netherlands (1969–2003)

This article explores how the relation between waste and electricity regimes changed in the Netherlands in a long-term perspective. The concept of socio-technical regime is used to investigate institutional, technological and social (network) changes. The conclusion is that the relationship changed from two regimes being separated into a much more symbiotic and integrated relationship through a multi-level and co-evolutionary process. The concept of ‘biomass’ has become a binding element in the relationship.     

Mathematical modelling of the effect of surface roughness on magnetic field profiles in type II superconductors

One of the defining characteristics of a superconductor is the Meissner effect, in which an external magnetic field is expelled from the bulk of a sample when cooled below the critical temperature. Although there has been considerable theoretical work on the Ginzburg–Landau theory of superconductors, the effects of interest in this paper can be modelled with the simpler London equation. This equation predicts an exponential decay of the local magnetic field magnitude as a function of the distance into the superconductor from a flat surface in the London limit where $\kappa =\lambda /\xi $ , defined as the ratio between the penetration depth and coherence length, is much greater than 1. However, recent measurements of the field profile in high $\kappa $ superconductors show that the observed decay is non-exponential near the surface. In particular, the measured field profiles indicate that the decay rate in the field magnitude is smaller than expected from a simple London model on a short length scale $d$ near the surface. In this paper, we examine the effects of surface roughness on magnetic field penetration into a high $\kappa $ superconductor. We model the roughness as a sinusoidal perturbation from a flat interface and investigate the effect using both an asymptotic method, based upon a small-amplitude perturbation, and a numerical method, using a finite difference discretization with a coordinate mapping from an underlying rectangular domain. A novel discretization is used in the case of 3D calculations and a fast, preconditioned GMRES solver is developed. A careful comparison of asymptotic and numerical methods validates both approaches for small perturbations, but the numerical approach allows for the investigation of rougher surfaces. Our results show that surface roughness reduces the decay rate in the average magnetic field near the surface relative to a London model. However, the reduction is more gradual than the simple dead layer model currently being used to fit experimental data. In addition, we discover some interesting new phenomena in the 3D case.     

Traffic conflicts on bicycle paths: A systematic observation of behaviour from video

In The Netherlands, on bicycle paths, single-bicycle accidents, bicycle–bicycle and bicycle–moped accidents constitute a considerable share of all bicyclist injuries. Over three quarters of all hospitalised bicyclist victims in the Netherlands cannot be directly related to a crash with motorised traffic. As the usage of bicycle paths steadily increases, it is to be expected that safety on bicycle paths will become a major issue in the coming years in The Netherlands.     

Greenhouse gas implications of household energy technology in Kenya

Linkages between household energy technology, indoor air pollution, and greenhouse gas (GHG) emissions have become increasingly important in understanding the local and global environmental and health effects of domestic energy use. We report on GHG emissions from common Kenyan wood and charcoal cookstoves. Our estimations are based on 29 d of measurements under the conditions of actual use in 19 rural Kenyan households. Carbon monoxide (CO), particulate matter (PM10), combustion phase, and fuel mass were measured continuously or in short intervals in day-long monitoring sessions. Emissions of pollutants other than CO and PM10 were estimated using emissions ratios from published literature. We estimated that the daily carbon emissions from charcoal stoves (5202 +/- 2257 g of C: mean +/- SD) were lower than both traditional open fire (5990 +/- 1843 g of C) and improved ceramic woodstoves (5905 +/- 1553 g of C), but the differences were not statistically significant. However, when each pollutant was weighted using a 20-yr global warming potential, charcoal stoves emitted larger amounts of GHGs than either type of woodstove (9850 +/- 4600 g of C for charcoal as compared to 8310 +/- 2400 and 9649 +/- 2207 for open fire and ceramic woodstoves, respectively; differences not statistically significant). Non-CO2 emissions from charcoal stoves were 5549 +/- 2700 g of C in 20-yr CO2 equivalent units, while emissions were 2860 +/- 680 and 4711 +/- 919 for three-stone fires and improved ceramic stoves, respectively, with statistically significant results between charcoal and wood stoves. Therefore in a sustainable fuel-cycle (i.e., excluding CO2), charcoal stoves have larger emissions than woodstoves. When the emissions from charcoal production, measured in a previous study, were included in the assessment, the disparity between the GHG emissions from charcoal and firewood increased significantly, with non-CO2 GHG emissions factors (g of C/kg of fuel burned) for charcoal production and consumption 6-13 times higher than emissions from woodstoves. Policy implications and options for environment and public health are discussed.