Cotton root growth as affected by P fertilizer placement

Growth chamber studies were conducted to evaluate root growth and P uptake by cotton (Gossypium hirsutum L.) as affected by the proportion of the soil volume that is treated with fertilizer P. Cotton seedlings were grown in a Dewey silty clay loam (Typic Paleudult) and a Marvyn loamy sand (Typic Paleudult). The Dewey soil had a low-P status and the Marvyn soil had a high-P status (7 and 44 mg kg^–1 Mehlich I extractable P, respectively). Phosphorus was added at a constant or base rate which was added to decreasing proportions of the soil volume (i.e. 1.0, 0.5, 0.25 and 0.125). The addition of the same amount of P to decreasing proportions of the soil volume resulted in a stimulation of root growth in the P-fertilized soil volume relative to the nonfertilized soil. The degree of stimulation was similar for the two soils which differed in P status. Phosphorus uptake reached a maximum when 0.25 and 0.50 of the soil volume was treated with P on the Marvyn and Dewey soils, respectively.     

Development and characterization of photopolymerizable biodegradable materials from PEG-PLA-PEG block macromonomers

As tissue engineering and drug delivery applications increase in both number and complexity, the demand for new synthetic biocompatible polymers with precisely tailored properties grows accordingly. Block copolymers are a particularly promising biomaterial as the physical and physiological properties of these polymers can be closely controlled through manipulation of the type and organization of the blocks in the polymer's backbone. In this work, poly(ethylene glycol) (PEG) and poly(lactic acid) (PLA) were incorporated into PEG-PLA-PEG block macromonomers with (meth)acrylate functionality to form photopolymerizable, highly cross-linked polymers for potential use in a variety of biomedical applications. Simply by directing the PLA:PEG ratio in these macromonomers, the hydrophobicity, physical behavior, degradation, and biocompatibility of the resulting polymer were controlled. Specifically, it was found that by increasing the PLA:PEG ratio, the degree of water uptake and the mechanical strength of the material is significantly decreased, while the glass transition temperature and degradation of the PEG-PLA polymers are delayed. Additionally, the biocompatibility of the PEG-PLA polymers is significantly influenced by the chemical composition of the material as increased PLA generally yields greater cell compatibility. By demonstrating the versatility of the photopolymerizable PEG-PLA polymers, the results of this study indicate that these materials have the potential to serve as a synthetic biomaterial platform, in which the properties of the polymer can be tailored to a variety of tissue engineering or drug delivery applications.     

Effect of soil pH on the requirement for water-soluble phosphorus in triple superphosphate fertilizers

A greenhouse study was conducted to determine if soil pH affects the requirement for water-soluble P and the tolerance of water-insoluble impurities in TSP fertilizers. Two commercial TSP fertilizers were selected to represent a range in phosphate rock sources and impurities. Phosphate fertilizer impurities were isolated as the water-washed fraction by washing whole fertilizers with deionized water. TSP fertilizers with various quantities of water-soluble P (1.2 to 99% water-soluble P) were simulated by mixing the water-washed fertilizer fractions or dicalcium phosphate (DCP) with reagent-grade monocalcium phosphate (MCP). The fertilizers were applied to supply 40 mg AOAC available P kg^–1 to a Mountview silt loam (fine-silty, siliceous, thermic Typic Paleudults). Wheat (Triticum aestivum (L.)) was harvested at 49 and 84 days after planting. Soil pH values at the final forage harvest were 5.4±0.16 and 6.4±0.15. At a soil pH of 5.4, the TSP fertilizers required only 37% water-soluble P to reach maximum yields while at pH 6.4 the fertilizers required 63% water-soluble P. Results of this study show that higher levels of water -insoluble P can be tolerated in TSP fertilizers when applied to acid soils. Phosphorus uptake was not affected by soil pH, but for the mixtures containing the fertilizer residues the source having the lowest level of Fe and Al had a higher relative agronomic effectiveness.     

Variations in Reactivity on Different Crystallographic Orientations of Cerium Oxide

Cerium oxide is a principal component in many heterogeneous catalytic processes. One of its key characteristics is the ability to provide or remove oxygen in chemical reactions. The different crystallographic faces of ceria present significantly different surface structures and compositions that may alter the catalytic reactivity. The structure and composition determine the number of coordination vacancies surrounding surface atoms, the availability of adsorption sites, the spacing between adsorption sites and the ability to remove O from the surface. To investigate the role of surface orientation on reactivity, CeO₂ films were grown with two different orientations. CeO₂(100) films were grown ex situ by pulsed laser deposition on Nb-doped SrTiO₃(100). CeO₂(111) films were grown in situ by thermal deposition of Ce metal onto Ru(0001) in an oxygen atmosphere. The chemical reactivity was characterized by the adsorption and decomposition of various molecules such as alcohols, aldehydes and organic acids. In general the CeO₂(100) surface was found to be more active, i.e. molecules adsorbed more readily and reacted to form new products, especially on a fully oxidized substrate. However the CeO₂(100) surface was less selective with a greater propensity to produce CO, CO₂ and water as products. The differences in chemical reactivity are discussed in light of possible structural terminations of the two surfaces. Recently nanocubes and nano-octahedra have been synthesized that display CeO₂(100) and CeO₂(111) faces, respectively. These nanoparticles enable us to correlate reactions on high surface area model catalysts at atmospheric pressure with model single crystal films in a UHV environment.     

A typology of community opportunity and vulnerability in metropolitan Australia

A multivariate model using hierarchical clustering and discriminant analysis is used to identify clusters of community opportunity and community vulnerability across Australia's mega metropolitan regions. Variables used in the model measure aspects of structural economic change, occupational change, human capital, income, unemployment, family/household disadvantage, and housing stress. A nine-cluster solution is used to categorise communities across metropolitan space. Significant between -city variations in the incidence of these clusters of opportunity and vulnerability are apparent, suggesting the emergence of marked differentiation between Australia's mega metropolitan regions in their adjustments to changing economic and social conditions. Received: 15 October 1999 / Accepted: 21 June 2000     

A Cache Architecture for Extremely Unreliable Nanotechnologies

In the drive to create ever smaller transistors, conventional silicon CMOS devices are becoming more difficult to fabricate reliably as process size shrinks. New technologies are being investigated to replace silicon CMOS. While offering greater numbers of devices per unit area, all of these technologies are more difficult to fabricate, and more likely to fail in operation than current technologies. Nanotechnology research has identified the need for fault and defect tolerance at the architectural level so that future devices can be used in large-scale electronics circuits. This paper examines the problem of creating reliable caches using extremely unreliable technologies. We incorporate support logic (i.e., control, datapath, and self-test logic) into the analysis, and propose a novel Content Addressable Memory-based design incorporating "best practice" fault tolerant design techniques. The design requires 15 times the number of devices of a conventional design, but enables the use of device technologies with defect rates higher than 10^-6, a three order of magnitude improvement over non-fault tolerant designs     

Electricity consumption and energy savings potential of video game consoles in the United States

Total energy consumption of video game consoles has grown rapidly in the past few decades due to rapid increases in market penetration, power consumption of the devices, and increasing usage driven by new capabilities. Unfortunately, studies investigating the energy impacts of these devices have been limited and potential responses, such as ENERGY STAR requirements, have been difficult to define and implement. We estimate that the total electricity consumption of video game consoles in the US was around 11?TWh in 2007 and 16?TWh in 2010 (approximately 1?% of US residential electricity consumption), an increase of almost 50?% in 3?years. However, any estimate of total game console energy consumption is highly uncertain, and we have determined that the key uncertainty is the unknown consumer behavior with regards to powering down the system after use. Even under this uncertainty, we demonstrate that the most effective energy-saving modification is incorporation of a default auto power down feature, which could reduce electricity consumption of game consoles by 75?% (10?TWh reduction of electricity in 2010), saving consumers over $1 billion annually in electricity bills. We conclude that using an auto power down feature for game consoles is at least as effective for reducing energy consumption as implementing a strict set of energy efficiency improvements for the devices, is much easier to implement given the nature of the video game console industry, and could be applied retroactively to currently deployed consoles through firmware updates.     

Visible light driven photoelectrochemical water oxidation on nitrogen-modified TiO2 nanowires

We report hydrothermal synthesis of single crystalline TiO(2) nanowire arrays with unprecedented small feature sizes of ~5 nm and lengths up to 4.4 μm on fluorine-doped tin oxide substrates. A substantial amount of nitrogen (up to 1.08 atomic %) can be incorporated into the TiO(2) lattice via nitridation in NH(3) flow at a relatively low temperature (500 °C) because of the small cross-section of the nanowires. The low-energy threshold of the incident photon to current efficiency (IPCE) spectra of N-modified TiO(2) samples is at ~520 nm, corresponding to 2.4 eV. We also report a simple cobalt treatment for improving the photoelectrochemical (PEC) performance of our N-modified TiO(2) nanowire arrays. With the cobalt treatment, the IPCE of N-modified TiO(2) samples in the ultraviolet region is restored to equal or higher values than those of the unmodified TiO(2) samples, and it remains as high as ~18% at 450 nm. We propose that the cobalt treatment enhances PEC performance via two mechanisms: passivating surface states on the N-modified TiO(2) surface and acting as a water oxidation cocatalyst.     

Critical perspectives on network governance in urban regeneration, community involvement and integration

Significant claims have been made about the benefits of network governance and management in securing community involvement and assisting social integration in complex urban regeneration programmes. The move from vertical to horizontal forms of coordination, and the assumption of a more equal power distribution between participants, have combined with an emphasis on mutuality and trust to present networks as a promising mechanism for pluriform involvement and collective decision-making. Often this promise runs ahead of the evidence of how network governance functions in practice, the opportunities for different actors to influence the process and the often disappointing outcomes of joint decision-making. This special issue contributes to the ‘second generation of research on governance networks’ by tackling key questions relating to the sources of governance network failure and success. Building on the articles in this special issue, we explore these questions in relation to urban regeneration, community involvement and the integration of minority groups in The Netherlands, Sweden and England. This article reviews the articles in this special issue from the perspective of Klijn and Skelcher’s (2007) four conjectures on democracy and governance networks and Sørensen and Torfing’s (2007) four conditions for democratic anchorage. It also suggests ways in which the research agenda on networks in urban regeneration, community involvement and integration might be developed.