Using Probability to Reason about Soft Deadlines

Soft deadlines are significant in systems in which a bound on the response time is important, but the failure to meet the response time is not a disaster. Soft deadlines occur, for example, in telephony and switching networks. We investigate how to put probabilistic bounds on the time-complexity of a concurrent logic program by combining (on-line) profiling with an (off-line) probabilistic complexity analysis. The profiling collects information on the likelihood of case selection and the analysis uses this information to infer the probability of an agent terminating within k steps. Although the approach does not reason about synchronization, we believe that its simplicity and good (essentially quadratic) complexity mean that it is a promising first step in reasoning about soft deadlines

Analysis of a Multimedia Stream using Stochastic Process Algebra

It is now well recognised that the next generation of distributed systems will be distributed multimedia systems. Central to multimedia systems is quality of service, which defines the non-functional requirements on the system. In this paper we investigate how stochastic process algebra can be used in order to determine the quality of service properties of distributed multimedia systems. We use a simple multimedia stream as our basic example. We describe it in the Stochastic Process Algebra PEPA and then we analyse whether the stream satisfies a set of quality of service parameters: throughput, end-to-end latency, jitter and error rates

Parametric study of advanced multistage axial-flow compressors

Axial flow compressor study to increase pressure ratio and reduce overall lengt

Perceptions of dementia: an exploratory study of the first signs noted by carers and primary care practitioners

Dementia is a complex syndrome that poses challenges for the person with dementia, their family, and health and social care professionals. Primary care is often the first point of contact for people with dementia (Briggs & Askham, 1999), and primary care practitioners are recognised as having an integral role to play in the diagnosis and management of dementia (Downs, 1996). Around 70 per cent of people with dementia living in the community live with their carer. Most informal carers are the spouse or daughter of the person with dementia (Alzheimer's Scotland, 2000). Previous research has shown that caring for people with dementia can be stressful, although it also has many positive aspects, and that carers need support systems in place for themselves and their relative.The aim of the current study was to explore the first reported signs of dementia by two groups known to be closely involved with individuals within the earlier stages of the condition, carers and primary care practitioners. Previously unanalysed data collected from carers and practitioners who participated in the Downs et al (2003) study "Improving the response of primary care practitioners to people with dementia and their families: A randomised controlled trial of educational interventions" was used.A grounded theory approach (Strauss & Corbin, 1990) was adopted to explore the first signs of dementia reported by 122 carers and 204 primary care practitioners. Five main categories and thirty-two subcategories related to cognitive, emotional, behavioural, physical and other (non-categorised) signs of dementia were generated. Statistical analysis was carried out to explore the effect of sociodemographic and occupational variables on the first signs of dementia reported by carers and practitioners, and the effect oftraining on practitioner signs reported.Findings were discussed and implications for clinical practice and future research considered

The Effect of DNA Methylation on Transcription From the SV40 Early Promoter

The effect of DNA methylation on transcription from the SV40 early promoter was studied. The plasmid pVHC1 containing the SV40 promoter in the early direction linked to the chloramphenicol acetyltransferase (CAT) gene was methylated in vitro with mouse Krebs II ascites cell DNA methylase. This resulted in methylation of 10-25% of CpG dinucleotides. Comparison of this DNA with unmethylated plasmid in a transient expression assay indicated a 30-40% inhibition of CAT expression by methylation. At this level of methylation an average of only 1 to 2 of the CpGs contained within the promoter region will be methylated and the enhancer sequence which does not contain any CpG dinucleotides will remain unmodified. Therefore it is unlikely that this effect is caused by the direct inhibition of transcription factor binding, it is most likely due to the formation of inactive chromatin structures induced by the presence of methyl groups throughout the plasmid. This theory is supported by the observation that binding of the transcription factor Sp1 to GC box motifs is unaffected by methylation. In experiments where mouse cells were cotransfected with pVHC1 and oligonucleotides containing methylated or unmethylated GC boxes, the level of CAT expression was greatly reduced regardless of the methylation state of the GC box, indicating that methylation had no effect on Sp1 binding. Similarly in gel retardation assays, methylated and unmethylated GC box-containing oligonucleotides competed equally well with a labelled restriction fragment containing the SV40 promoter for Sp1 binding. These findings indicate that the SV40 promoter is methylation sensitive in a methylcytosine rich environment where these residues are most likely acting in an indirect manner, causing the formation of inactive chromatin and hence limiting transcription

Asset-Base: New Reserve Requirements for a New Banking Industry

This paper discusses a regulatory plan known as asset-based reserve requirements. By examining the history of reserve requirements in the United States and of current regulatory proposals and practices, I argue that a system of asset-based reserve requirements may provide a useful, though not often considered alternative to the current structures of liability based reserve requirements and capital requirements. Required reserves based on assets provide the Federal Reserve with a powerful, versatile, and adaptable policy tool for monetary policy. Additionally, they ensure risk-assessment, reduce the moral hazard problem associated with deposit insurance, and when applied to all fmancial institutions create a level playing field in the desegregated financial sector. Asset-based reserve requirements do all those things without burdening depositors as liability based reserve requirements do, and without the pro-cyclical characteristics inherent in capital requirements. The work of Thomas Palley (2000 & 2001), Frederic Mishkin (1998), Alan Greenspan (1998), Henry Kaufman (1994), Joshua Feinman (1993), and Paul Bennett (1997 & 2001) was relied upon to reach this conclusion

Complexing additives to reduce the immiscible phase formed in the hybrid ZnBr2 flow battery

The zinc-bromine redox flow battery (RFB) is one of a very few commercially viable RFB energy storage system capable of integration with intermittent renewable energy sources to deliver improved energy management. However, due to the volatility of the electrogenerated bromine and potential for its crossover from positive to negative electrolytes, this system requires the use of quaternary ammonium complexes (N-methyl-N-ethylpyrrolidinium, (MEP)) to capture this bromine. This produces an immiscible phase with the Br2 which requires a complex network of pipes, pumps and automated controls to ensure access to the electroactive material during discharge. In this work, the use of novel quaternary ammonium complexes to capture the electrogenerated bromine but to keep it in the aqueous phase is examined. Three compounds, 1-(carboxymethyl) pyridine-1-ium, 1-(2-carboxymethyl)-1-methylmorpholin-1-ium and 1-(2-carboxymethyl)-1-methylpyrrolidin-1-ium, were found to successfully reduce the volume of the immiscible phase formed on complexing with the polybromide (Brx-) whilst displaying similar enthalpy of vaporisation values as that of MEP. Electrochemical analysis also revealed that these compounds did not impact on the electrode kinetics of the Br-/Brx- reaction indicating that the resulting surface film formed with these compounds behaved as a chemically modified electrode, in contrast to the surface film formed with MEP