Incremental Construction of Large Specifications: Case Study and Techniques

The RODIN project is an EU-funded project concerned with the provision of methods and tools for rigorous development of complex software-based systems. Ultimately, through the development of open-source tools and techniques, the project aims to make formal methods more appealing and accessible to industry. The project is driven by a number of case studies, each of which is designed to exercise the technology being developed and create methodologies for the future. In this paper we focus on the methodologies being developed in one of the case studies (the CDIS subset). This case study is based on a commercial air traffic information system that was developed using formal methods 14 years ago, and it is still in operation today. The key goals of our approach are to improve the comprehensibility of large specifications and to achieve a complete mechanical proof of consistency

Redevelopment of an industrial case study using Event-B and Rodin

CDIS is a commercial air traffic information system that was developed using formal methods 15 years ago by Praxis, and it is still in operation today. This system is an example of an industrial scale system that has been developed using formal methods. In particular, the functional requirements of the system were specified using VVSL -- a variant of VDM. A subset of the original specification has been chosen to be reconstructed on the Rodin platform based on the new Event-B formalism. The goal of our reconstruction was to overcome three key difficulties of the original formalisation, namely the difficulty of comprehending the original specification, the lack of any mechanical proof of the consistency of the specification and the difficulty of dealing with distribution and atomicity refinement. In this paper we elucidate how a new formal notation and tool can help to overcome these difficulties

Modelling and Refinement in CODA

This paper provides an overview of the CODA framework for modelling and refinement of component-based embedded systems. CODA is an extension of Event-B and UML-B and is supported by a plug-in for the Rodin toolset. CODA augments Event-B with constructs for component-based modelling including components, communications ports, port connectors, timed communications and timing triggers. Component behaviour is specified through a combination of UML-B state machines and Event-B. CODA communications and timing are given an Event-B semantics through translation rules. Refinement is based on Event-B refinement and allows layered construction of CODA models in a consistent way.Comment: In Proceedings Refine 2013, arXiv:1305.563

Economic issues in a trial of the controlled provision of heroin

Executive Summary: This paper discusses some economic issues that may be investigated as part of a proposed trial of the controlled provision of heroin in the Australian Capital Territory. Such a trial would provide an opportunity to gather empirical evidence on some aspects of the operation of the market for heroin. Specifically, it would enable the investigation of the extent to which purity, rather than price, is the equilibrating mechanism in this market. If purity is an important equilibrating mechanism, then provision of heroin of constant purity to trial participants would yield important health benefits to those participants. However, if purity on the black market is increased in economic retaliation against a trial, there may be unintended adverse effects on the health of black market users in the short run. In the long run, stabilisation of purity on the black market may be associated with an improvement in the health status of non-trial users. An important issue that cannot be addressed in the context of the proposed trial is the price elasticity of demand for heroin, that is, the responsiveness of demand for heroin to a change in its price. The use of pre–specified criteria to determine eligibility for participation in a trial will preclude any estimation of the increase in demand for heroin attributable to a fall in its price

Emerging Technologies in Metal Working Fluids and Compatibility with Refrigeration Systems

Metal working fluids (MWF) are basically two types, metal removal (chip making) and metal forming (chip-less). MWF are used in all aspects of production fabrication of refrigeration systems. Metal removal applications typically include turning followed by finish lapping of crankshafts and piston connecting rods, also milling and finish grinding of screw compressor vanes. Metal forming applications include deep drawing of compressor housings, wire drawing, tube forming and stamping of electric motor laminations. MWF are not always completely removed before final assembly. The MWF residuals may get mixed into the refrigerant and compressor lubricant affecting system life and efficiency.  To date, very little compatibility testing of residual MWF in refrigeration lubes and refrigerants has been investigated.  Unlike most lube oils, MWF are typically water-based and traditionally make very high usage of extreme pressure (EP) additives. EP additives help remove metal during the cutting process and actually increase wear. EP containing MWF may interfere with compressor lube oil performance. EP are additives are known to be somewhat acidic and corrosive.  Due environmental persistence concerns, the EPA will restrict the use of chlorinated alkanes as EP additives. Chlorinated alkanes will be being phased out over the next few years and replacements are needed. It has been proven that preformed emulsions are capable of replacing traditional EP additives in MWF. Preformed emulsions allow non-traditional base “oils†to be used in MWF. These non-traditional base oils are generally very high in viscosity and viscosity index. Some of these base stocks exhibit very high film strengths under high pressures encountered in metal removal operations. These high VI and high film strength synthetic base stocks can replace corrosive EP additives without loss of machining or drawing (stamping) performance. Residual films remaining after machining are non-reactive and oil like, providing corrosion protection of in process metal parts prior to assembly. Additionally, high viscosity synthetic base stocks provide low pour points, lower volatility and less vapor interaction within a refrigeration system. Better compatibility with mostly non-polar water insoluble refrigeration lubricants are a benefit. In the future, new refrigerants are likely to be more reactive to reduce environmental persistence. Interactions and effects of various classes MWF with traditional compressor lubes and refrigerants are examined and reported

Location of community pharmacies and prevalence of oral conditions in the Western Cape Province

Community pharmacists are approached regularly for oral health advice; most commonly for ulcers which could be indicative of oral cancer, HIV, and various systemic diseases. Community pharmacists should know how to manage these conditions yet they have very limited training to manage these conditions appropriately. The area location and socioeconomic status (SES) of the pharmacy should be considered as it may influence patient management. A study of this nature has not yet been conducted in the Western Cape Province of South Africa. To determine the prevalence and frequency of oral complaints at community pharmacies and if these parameters differ by metropolitan location and SES. A cross-sectional survey of 162 randomlyselected private sector pharmacies was conducted. The sample (n = 121) was stratified by SES and metropolitan location. An open-ended structured questionnaire was faxed to pharmacists. A telephonic interview was conducted a day later. Community pharmacists were asked about the frequency and type of oral health problems they encountered. Most pharmacists (91%) dealt with oral health problems frequently, most commonly for ulcers (55.8%), thrush (49.2%), and toothache (33.3%). The results did not differ by metropolitan location and SES (Chi-squared, Fisher’s Exact, p > 0.05), with the exception of toothache and mouth sores. Community pharmacists are an important part of an interdisciplinary team, and play a definite role in the early detection of oral health conditions, namely, caries, HIV and oral cancer. Training on common oral health conditions should be included in undergraduate pharmacy curricula and continuous professional development courses.Department of HE and Training approved lis

Preferential formation of human heteromeric SK2:SK3 channels limits homomeric SK channel assembly and function

Three isoforms of small conductance, calcium-activated potassium (SK) channel subunits have been identified (SK1-3) that exhibit a broad and overlapping tissue distribution. SK channels have been implicated in several disease states including hypertension and atrial fibrillation, but therapeutic targeting of SK channels is hampered by a lack of subtype-selective inhibitors. This is further complicated by studies showing that SK1 and SK2 preferentially form heteromeric channels during co-expression, likely limiting the function of homomeric channels in vivo. Here, we utilized a simplified expression system to investigate functional current produced when human (h) SK2 and hSK3 subunits are co-expressed. When expressed alone, hSK3 subunits were more clearly expressed on the cell surface than hSK2 subunits. hSK3 surface expression was reduced by co-transfection with hSK2. Whole-cell recording showed homomeric hSK3 currents were larger than homomeric hSK2 currents or heteromeric hSK2:hSK3 currents. The smaller amplitude of hSK2:hSK3-mediated current when compared with homomeric hSK3-mediated current suggests hSK2 subunits regulate surface expression of heteromers. Co-expression of hSK2 and hSK3 subunits produced a current that arose from a single population of heteromeric channels as exhibited by an intermediate sensitivity to the inhibitors apamin and UCL1684. Co-expression of the apamin-sensitive hSK2 subunit and a mutant, apamin-insensitive hSK3 subunit [hSK3(H485N)], produced an apamin-sensitive current. Concentration-inhibition relationships were best fit by a monophasic Hill equation, confirming preferential formation of heteromers. These data show that co-expressed hSK2 and hSK3 preferentially form heteromeric channels and suggest that the hSK2 subunit acts as a chaperone, limiting membrane expression of hSK2:hSK3 heteromeric channels