Dynamic acoustic field activated cell separation (DAFACS)

Advances in diagnostics, cell and stem cell technologies drive the development of application-specific tools for cell and particle separation. Acoustic micro-particle separation offers a promising avenue for highthroughput, label-free, high recovery, cell and particle separation and isolation in regenerative medicine. Here, we demonstrate a novel approach utilizing a dynamic acoustic field that is capable of separating an arbitrary size range of cells. We first demonstrate the method for the separation of particles with different diameters between 6 and 45 μm and secondly particles of different densities in a heterogeneous medium. The dynamic acoustic field is then used to separate dorsal root ganglion cells. The shearless, label-free and low damage characteristics make this method of manipulation particularly suited for biological applications. Advantages of using a dynamic acoustic field for the separation of cells include its inherent safety and biocompatibility, the possibility to operate over large distances (centimetres), high purity (ratio of particle population, up to 100%), and high efficiency (ratio of separated particles over total number of particles to separate, up to 100%)

Comparing Ecosystem Service preferences between urban and rural dwellers

Urbanization can profoundly alter socioecological relationships, but its influence on how people perceive and value ecosystem services (ES) is poorly understood. We reviewed an emerging literature in which sociocultural valuation of ES is compared among urban and rural dwellers. This research suggests that, although regulating and cultural ES were highly valued by both rural and urban dwellers, urban dwellers tended to value provisioning ES less than rural dwellers did. Differences in ES valuation could result from different experiences, uses, and needs for ES of urban and rural dwellers. We also identified two key gaps in the literature that relate to understanding how diverse ES contribute differently to the well-being of rural and urban populations (and the relevance of these differences for environmental education and policy) and the changing roles of ES in developing countries and vulnerable ecosystems, such as small islands, that face pressing environmental, social, and economic challenges

The influence of landscape context on the production of cultural ecosystem services

Recent efforts to apply sustainability concepts to entire landscapes have seen increasing interest in approaches that connect socioeconomic and biophysical systems. Evaluating these connections through a cultural ecosystem services lens clarifies how different spatiotemporal scales and levels of organisation influence the production of cultural benefits. Currently, however, the effects of multi-level and multi-scale ecological variation on the production of cultural benefits have not yet been disentangled. Objectives To quantify the amount of variation in cultural ecosystem service provision by birds to birders that is due to landscape-level attributes. Methods We used data from 293 birding routes and 101 different birders in South African National Parks to explore the general relationships between birder responses to bird species and environmental conditions, bird-related observations, the biophysical attributes of the landscape and their effect on bird-related cultural benefits. Results Biophysical attributes (particularly biome, vegetation type, and variance in elevation) significantly increased the percentage of variance explained in birder benefits from 57 to 65%, demonstrating that birder benefits are derived from multi-level (birds to ecosystems) and multi-scale (site to landscape) social and ecological interactions. Conclusions Landscape attributes influence people's perceptions of cultural ecosystem service provision by individual species. Recognition of the complex, localised and inextricable linkage of cultural ecosystem services to biophysical attributes can improve our understanding of the landscape characteristics that affect the supply and demand of cultural ecosystem services

Silicon mirror suspensions for gravitational wave detectors

One of the most significant limits to the sensitivity of current, and future, long-baseline interferometric gravitational wave detectors is thermal displacement noise of the test masses and their suspensions. This paper reports results of analytical and experimental studies of the limits to thermal noise performance of cryogenic silicon test mass suspensions set by two constraints on suspension fibre dimensions: the minimum dimensions required to allow conductive cooling for extracting incident laser beam heat deposited in the mirrors; and the minimum dimensions of fibres (set by their tensile strength) which can support test masses of the size envisaged for use in future detectors. We report experimental studies of breaking strength of silicon ribbons, and resulting design implications for the feasibility of suspension designs for future gravitational wave detectors using silicon suspension fibres. We analyse the implication of this study for thermal noise performance of cryogenically cooled silicon suspensions

Micro-cooler Enhancements by Barrier Interface Analysis

Peer reviewedPublisher PD

The first Suzaku observation of SGR 1806-20

The soft gamma-ray repeater SGR 1806-20 has been attracting a lot of attention owing to the fact that in December 2004 it emitted the most powerful giant flare ever observed. Here we present the results of the first Suzaku observation of SGR 1806-20, that seems to have reached a state characterized by a flux close to the pre-flare level and by a relatively soft spectrum. Despite this, the source remained quite active, as testified by several short bursts observed by Suzaku. We discuss the broadband spectral properties of SGR 1806-20 in the context of the magnetar model, considering its recent theoretical developments.Comment: 3 pages, 1 figure. Proceedings of the conference "40 Years of Pulsars, Millisecond Pulsars, Magnetars and More", Montreal, August 12-17 2007. AIP, in pres

The role of socio-demographic characteristics in mediating relationships between people and nature

Research on ecosystem services has focused on their availability or supply and often takes a socially-aggregated approach that assumes a single human community of identical beneficiaries. However, people's ability to derive benefits from ecosystem services can differ strongly across societal groups. Access to ecosystem services can be related to socio-demographic characteristics such as material wealth, gender, education and age. Developing environmental management that does not have unequal impacts on different groups thus depends on taking a socially-disaggregated approach to assessing perceptions of ecosystem services. We explored how socio-demographic characteristics relate to cultural functional groups based on perceived bird traits. Using perception data on 491 bird species from 401 respondents along urban-rural gradients in South Africa, we found that socio-demographic characteristics are strongly associated with cultural functional groups based on perceived bird traits. Our results provide a starting point for understanding heterogeneity in the benefits from avian ecosystem services and how perceptions of cultural functional groups vary across societal groups

Mitigation of Moral Hazard and Adverse Selection in Venture Capital Financing: The Influence of the Country’s Institutional Setting

A venture capitalist (VC) needs to trade off benefits and costs when attempting to mitigate agency problems in their investor-investee relationship. We argue that signals of ventures complement the VC’s capacity to screen and conduct a due diligence during the pre-investment phase, but its attractiveness may diminish in institutional settings supporting greater transparency. Similarly, whereas a VC may opt for contractual covenants to curb potential opportunism by ventures in the post-investment phase, this may only be effective in settings supportive of shareholder rights enforcement. Using an international sample of VC contracts, our study finds broad support for these conjectures. It delineates theoretical and practical implications for how investors can best deploy their capital in different institutional settings whilst nurturing their relationships with entrepreneurs

The development of planar Gunn diodes for the realisation of MMIC oscillators

This review presents the development of planar Gunn diodes over the last few years for the implementation of millimetre-wave sources. The fabrication procedure incorporates electron beam lithography and the oscillation frequency is determined by the anode-to-cathode distance. The evolution of the material design for the maximisation of the maximum frequency of oscillation and the enhancement of the generated power is presented in this paper. The recent implementation of a planar Gunn diode with a high-electron mobility transistor on the same substrate is also described in this work