Trajectories toward maximum power and inequality in resource distribution networks.

Resource distribution networks are the infrastructure facilitating the flow of resources in both biotic and abiotic systems. Both theoretical and empirical arguments have proposed that physical systems self-organise to maximise power production, but how this trajectory is related to network development, especially regarding the heterogeneity of resource distribution in explicitly spatial networks, is less understood. Quantifying the heterogeneity of resource distribution is necessary for understanding how phenomena such as economic inequality or energetic niches emerge across socio-ecological and environmental systems. Although qualitative discussions have been put forward on this topic, to date there has not been a quantitative analysis of the relationship between network development, maximum power, and inequality. This paper introduces a theoretical framework and applies it to simulate the power consumption and inequality in generalised, spatially explicit resource distribution networks. The networks illustrate how increasing resource flows amplify inequality in power consumption at network end points, due to the spatial heterogeneity of the distribution architecture. As increasing resource flows and the development of hierarchical branching can both be strategies for increasing power consumption, this raises important questions about the different outcomes of heterogeneous distribution in natural versus human-engineered networks, and how to prioritise equity of distribution in the latter.

Scattering of near normal incidence SH waves by sinusoidal and rough surfaces in 3-D: comparison to the scalar wave approximation.

The challenge of accurately simulating how incident scalar waves interact with rough boundaries has made it an important area of research within many scientific disciplines. Conventional methods, which in the majority of cases focus only on scattering in two dimensions, often suffer from long simulation times or reduced accuracy, neglecting phenomena such as multiple scattering and surface self-shadowing. A simulation based on the scalar wave distributed point source method (DPSM) is presented as an alternative which is computationally more efficient than fully meshed numerical methods while obtaining greater accuracy than approximate analytical techniques. Comparison is made to simulated results obtained using the finite element method for a sinusoidally periodic surface where scattering only occurs in two dimensions, showing very good agreement (<0.2 dB). In addition to two-dimensional scattering, comparison to experimental results is also carried out for scattering in three dimensions when the surface has a Gaussian roughness distribution. Results indicate that for two-dimensional scattering and for rough surfaces with a correlation length equal to the incident wavelength (λ) and a root mean square height less than 0.2λ, the scalar wave approximation predicts reflected pulse shape change and envelope amplitudes generally to within 1 dB. Comparison between transducers within a three-element array also illustrate the sensitivity pulse amplitude can have to sensor position above a rough surface, differing by as much as 17 dB with a positional change of just 1.25λ.

Surgeon administered regional blocks for day case forefoot surgery.

INTRODUCTION: The aim was to see if as surgeons we were providing safe, efficient and effective, regional blocks for patients undergoing day case, forefoot surgery. We also assessed the costs of, providing this service. METHODS: 63 consecutive patients were recruited prospectively for local anaesthetic block. Blocks were, performed by the orthopaedic team. Efficacy of block was assessed intra-operatively with a visual, analogue score (VAS) of 0-10. Satisfaction with the anaesthetic procedure was also assessed. RESULTS: Average time to perform the block was 6 min. Mean VAS for knife to skin was 0.44 (95%, confidence 0.07-0.81) and for ankle tourniquet was 1.39 (95% confidence 0.85-1.39). Patients were, highly satisfied with the blocks. No complications were reported. CONCLUSIONS: These blocks are quick and easy to perform by orthopaedic surgeons. They are well, tolerated and effective. They result in considerable cost savings to the Hospital.

Past, present, and future controls on levels of persistent organic pollutants in the global environment.

Understanding the legacy of persistent organic pollutants requires studying the transition from primary to secondary source control.

Seasonality of the air-forest canopy exchange of persistent organic pollutants.

Forest canopies represent an extensive organic surface available for partitioning of semivolatile organic pollutants with the atmosphere. To date, the ability of forests to sequester such compounds (the so-called "forest filter effect") has been investigated using indirect methods that yield time integrated deposition fluxes and scenario-dependent deposition velocities. In the present study, experimental data collected at three different alpine forest sites were used to assess the dynamics of PCB deposition fluxes (F, ng m(-2) d(-1)) during the growing season. Estimated values of Fwere consistent with previously reported data. Furthermore, this study showed that maximum levels of F in late spring can be a factor of 1.4-3.4 higher than their seasonal mean value. These data, in conjunction with a simple modelframeworkthatincludesthe main forcing parameters of air concentration, temperature, foliage structure, and biomass dynamics, are used to estimate the plant-air mass transfer coefficient (ku, m d(-1)) and its variation with time in one of the forests. ku did not appear to significantly vary during the season, and its mean seasonal value ranged between 43 and 95 m d(-1) for selected compounds. The proposed framework was successfully applied to predict the variation in canopy concentration with time in the other two forests.

Biosynthesis of the insect pheromone (S)-4-methyl-3-heptanone.

Using stable isotope-labelled probes and mass spectrometry, the insect pheromone (S)-4-methyl-3-heptanone is shown to be biosynthesised from three propionate units following a polyketide/fatty acid-type metabolic route.

Comparison of anti-feedant and insecticidal activity of nimbin and salannin photo-oxidation products with neem (Azadirachta indica) limonoids.

Photo-oxidation of the neem limonoids nimbin and salannin with UV light in the presence of oxygen gives two isomeric lactone products per limonoid, nimbinolide and isonimbinolide, and salanninolide and isosalanninolide, respectively. When compared in insect tests with the important limonoids of neem seeds, azadirachtin, nimbin and salannin, isonimbinolide and isosalanninolide show activity greater than that of nimbin or salannin and in some respects show activity approaching that of azadirachtin. The photo-oxidation products were tested for anti-feedant activity and toxicity against larvae of three species of Lepidoptera, Spodoptera littoralis (Boisd), Spodoptera frugiperda (FE Smith) and Helicoverpa armigera (Hübner) and nymphs of the locusts Schistocerca gregaria (Forskål) and Locusta migratoria (L).