A formal model of real-time program compilation

Program compilation can be formally defined as a sequence of equivalence-preserving transformations, or refinements, from high-level language programs to assembler code, Recent models also incorporate timing properties, but the resulting formalisms are intimidatingly complex. Here we take advantage of a new, simple model of real-time refinement, based on predicate transformer semantics, to present a straightforward compilation formalism that incorporates real-time constraints. (C) 2002 Elsevier Science B.V. All rights reserved.

Refining exceptions using King and Morgan's exit construct

In this paper we discuss the refinement of exceptions. We extend the Guarded Command Language normally used in the refinement calculus, with a simple exception handling statement, which we model using King and Morgan's exit statement (1995). We derive some variants of King and Morgan's refinement laws for their exit statement, and illustrate the approach with an example of a refinement of a simple program.

A partial-correctness semantics for modelling assembler programs

Previous work on formally modelling and analysing program compilation has shown the need for a simple and expressive semantics for assembler level programs. Assembler programs contain unstructured jumps and previous formalisms have modelled these by using continuations, or by embedding the program in an explicit emulator. We propose a simpler approach, which uses techniques from compiler theory in a formal setting. This approach is based on an interpretation of programs as collections of program paths, each of which has a weakest liberal precondition semantics. We then demonstrate, by example, how we can use this formalism to justify the compilation of block-structured high-level language programs into assembler.

Reasoning about deadlines in concurrent real-time programs

We propose a method for the timing analysis of concurrent real-time programs with hard deadlines. We divide the analysis into a machine-independent and a machine-dependent task. The latter takes into account the execution times of the program on a particular machine. Therefore, our goal is to make the machine-dependent phase of the analysis as simple as possible. We succeed in the sense that the machine-dependent phase remains the same as in the analysis of sequential programs. We shift the complexity introduced by concurrency completely to the machine-independent phase.

Experimental Verification of Decoherence-Free Subspaces

Using spontaneous parametric down-conversion, we produce polarization-entangled states of two photons and characterize them using two-photon tomography to measure the density matrix. A controllable decoherence is imposed on the states by passing the photons through thick, adjustable birefringent elements. When the system is subject to collective decoherence, one particular entangled state is seen to be decoherence-free, as predicted by theory. Such decoherence-free systems may have an important role for the future of quantum computation and information processing.

Bellerophon: a program to detect chimeric sequences in multiple sequence alignments

Bellerophon is a program for detecting chimeric sequences in multiple sequence datasets by an adaption of partial treeing analysis. Bellerophon was specifically developed to detect 16S rRNA gene chimeras in PCR-clone libraries of environmental samples but can be applied to other nucleotide sequence alignments.

Combining GIS and Expert Opinion to Model Landscapes for a Smallholder Forest Extension Program in Leyte, the Philippines

A Geographic Information System (GIS) was used to model datasets of Leyte Island, the Philippines, to identify land which was suitable for a forest extension program on the island. The datasets were modelled to provide maps of the distance of land from cities and towns, land which was a suitable elevation and slope for smallholder forestry and land of various soil types. An expert group was used to assign numeric site suitabilities to the soil types and maps of site suitability were used to assist the selection of municipalities for the provision of extension assistance to smallholders. Modelling of the datasets was facilitated by recent developments of the ArcGIS® suite of computer programs and derivation of elevation and slope was assisted by the availability of digital elevation models (DEM) produced by the Shuttle Radar Topography (SRTM) mission. The usefulness of GIS software as a decision support tool for small-scale forestry extension programs is discussed.

An evaluation of the Keep on Talking program for maintaining communication skills into old

Communication skills change with age as a result of sensory deficits, memory loss, and increasing word finding difficulties The Keep on Talking program (L. Hickson, H. Barnett, L. Worrall, & E. Yiu, 1994) was developed to assist older people to develop their own strategies for maintaining communication skills into old age. Two hundred and fifty-two healthy older people were recruited from the community and were assessed on a battery of communication assessments on entry to the study and at 1 year after entry. The experimental group (n = 120) participated in the 5-week group Keep on Talking program run by volunteers A further 130 control subjects were assessed only. The short-term effectiveness of the program was evaluated using a short knowledge based and attitudinal questionnaire and qualitative written feedback. At the I-year follow up, subjects were also asked whether they had taken any action as a result of the project. Results concluded that there was a significant difference between the number of correct questionnaire responses on the knowledge based items and the ratings on the attitudinal items pre- and postprogram questionnaire for the experimental subjects. Qualitative written feedback was positive with many participants remarking on the amount of information that they had acquired. Forty-eight experimental and 69 control subjects (n = 117) were assessed I year later, and there was a significant difference between the groups in terms of the number of subjects who reported having taken action as a result of the program. The Keep on Talking program increased knowledge about communication, produced a positive change in attitude toward the importance of communication, and encouraged participants to take action to maintain their communication skills. Maintaining communication skills may prevent social isolation. This simple 5-hour group program has been effective in empowering participants to maintain. their communication skills as they age.

Interval breast cancers in an Australian mammographic screening program

Objective: To determine the incidence of interval cancers which occurred in the first 12 months after mammographic screening at a mammographic screening service. Design: Retrospective analysis of data obtained by crossmatching the screening Service and the New South Wales Central Cancer Registry databases. Setting: The Central & Eastern Sydney Service of BreastScreen NSW. Participants: Women aged 40-69 years at first screen, who attended for their first or second screen between 1 March 1988 and 31 December 1992. Main outcome measures: Interval-cancer rates per 10 000 screens and as a proportion of the underlying incidence of breast cancer (as estimated by the underlying rate in the total NSW population). Results: The 12-month interval-cancer incidence per 10 000 screens was 4.17 for the 40-49 years age group (95% confidence interval [CI], 1.35-9.73) and 4.64 for the 50-69 years age group (95% CI, 2.47-7.94). Proportional incidence rates were 30.1% for the 40-49 years age group (95% CI, 9.8-70.3) and 22% for the 50-69 years age group (95% CI, 11.7-37.7). There was no significant difference between the proportional incidence rate for the 50-69 years age group for the Central & Eastern Sydney Service and those of major successful overseas screening trials. Conclusion: Screening quality was acceptable and should result in a significant mortality reduction in the screened population. Given the small number of cancers involved, comparison of interval-cancer statistics of mammographic screening programs with trials requires age-specific or age-adjusted data, and consideration of confidence intervals of both program and trial data.

A bleach program for inmates in NSW: an HIV prevention strategy

Syringe cleaning guidelines for injecting drug users (IDUs) were revised in 1993. This paper examines efforts by IDUs in NSW prisons to adopt the revised guidelines in 1994. Consecutive inmates (229) nearing release were visited and asked to call a toll free number for an interview once released. Respondents (102) did not differ from non-respondents (127). Many respondents (64%) reported ever injecting and many of these reported injecting (58%), sharing (48%) and syringe cleaning (46%) when last in prison. Some (23%) respondents reported adopting the revised syringe cleaning guidelines. Tattooing (38%) was reported more often than sexual activity in prison (4%). A new methodology for prison research was found to be feasible in this study. The potential for HIV to spread in prison still poses major public health challenges.

CXTANNEAL: an improved program for estimating solute transport parameters

CXTANNEAL is a program for analysing contaminant transport in soils. The code, written in Fortran 77, is a modified version of CXTFIT, a commonly used package for estimating solute transport parameters in soils. The improvement of the present code is that it includes simulated annealing as the optimization technique for curve fitting. Tests with hypothetical data show that CXTANNEAL performs better than the original code in searching for optimal parameter estimates. To reduce the computational time, a parallel version of CXTANNEAL (CXTANNEAL_P) was also developed. (C) 1999 Elsevier Science Ltd. All rights reserved.