LETS get real: constraints on the development of Local Exchange Trading Schemes

Local Exchange Trading Schemes (LETS) are widely promoted as a new tool for local economic development, but until recently the focus has been on their alleged ‘potential’ rather than the realities of their operation. This paper assesses the practical economic role of LETS by examining the amount of trading conducted, and demonstrates that both the volume of trading and the value of the trades are very low. Drawing on an intensive case study of the first UK LETS created explicitly as part of a local authority’s anti-poverty strategy, explanations for the low levels of participation are suggested, and significant structural constraints on the development of LETS are identified

Analytical and experimental studies of an optimum multisegment phased liner noise suppression concept

Results are presented from detailed analytical studies made to define methods for obtaining improved multisegment lining performance by taking advantage of relative placement of each lining segment. Properly phased liner segments reflect and spatially redistribute the incident acoustic energy and thus provide additional attenuation. A mathematical model was developed for rectangular ducts with uniform mean flow. Segmented acoustic fields were represented by duct eigenfunction expansions, and mode-matching was used to ensure continuity of the total field. Parametric studies were performed to identify attenuation mechanisms and define preliminary liner configurations. An optimization procedure was used to determine optimum liner impedance values for a given total lining length, Mach number, and incident modal distribution. Optimal segmented liners are presented and it is shown that, provided the sound source is well-defined and flow environment is known, conventional infinite duct optimum attenuation rates can be improved. To confirm these results, an experimental program was conducted in a laboratory test facility. The measured data are presented in the form of analytical-experimental correlations. Excellent agreement between theory and experiment verifies and substantiates the analytical prediction techniques. The results indicate that phased liners may be of immediate benefit in the development of improved aircraft exhaust duct noise suppressors

Implications of Heavy Top

Lecture at 23 ITEP Winter School. Manifestations of heavy top at low energies (K- and B-mesons) and high energies (Z and W physics) are discussedComment: 12 pages; ps file can be found at http://venus.itep.ru/preprints/1995/95046.ps.g

Electric propulsion options for the SP-100 reference mission

Analyses were performed to characterize and compare electric propulsion systems for use on a space flight demonstration of the SP-100 nuclear power system. The component masses of resistojet, arcjet, and ion thruster systems were calculated using consistent assumptions and the maximum total impulse, velocity increment, and thrusting time were determined, subject to the constraint of the lift capability of a single Space Shuttle launch. From the study it was found that for most systems the propulsion system dry mass was less than 20 percent of the available mass for the propulsion system. The maximum velocity increment was found to be up to 2890 m/sec for resistojet, 3760 m/sec for arcjet, and 23 000 m/sec for ion thruster systems. The maximum thruster time was found to be 19, 47, and 853 days for resistojet, arcjet, and ion thruster systems, respectively

The impact of involvement in mental health research on views about mental health services and service use: findings from a UK survey

Background: Involvement of service users in mental health research, whether predicated on rights-based or instrumentalist arguments, is appropriately understood as a purposive social action likely to have both intended and unintended consequences. Despite rhetoric and some evidence that involvement is a good thing and confers benefits on the people involved, the impact on involved individuals remain underexplored. Aims: To describe the impact of involvement in research on views about mental health services and service use. Method: A cross-sectional survey of service users involved in mental health research across the UK. Data collected from 166 respondents using an online questionnaire were analysed using the framework approach and narratively synthesised. Results: Involvement, through enabling ‘behind the scenes’ access shaped views of service users about services and service use. Increased awareness of challenges and shortcomings of service delivery shifted expectations, commonly empowering service users to proactively engage in treatment. However, for some respondents, disillusionment led to discontinuation of services. Conclusions: Empowerment is a common outcome of involvement but a minority of service users may become critical and drop out of services. People considering involvement in research should be informed about the potential impact on their views and service use and be appropriately supported during involvement. The theory of user involvement needed to support robust examination of process and outcomes must encompass unintended consequences