Interface refinement in reactive systems (extended abstract)

Suppose one has a system that has a synchronous interface with its environment. Now, suppose that one refines this system and changes its interface to an asynchronous one. Whatever is meant here by refinement, it cannot be standard (process) refinement since the interface actions have changed; nor is it action refinement in the sense that a process is substituted for an action, as the intention presumably is to allow the system to proceed without having to wait until the environment is willing to synchronize. In this paper we propose a notion of interface refinement of which changing synchronous to asynchronous communication is an instance; as is in fact the reverse change. This notion of interface refinement is quite powerful; it generalizes all existing methods w.r.t. the class of interface changes that it allows. The major part of the paper is concerned with developing proof rules with which to verify interface refinement. We use (linear) temporal logic as specification language and an adaptation of the Manna-Pnueli verification framework. The method is illustrated by verifying an interface change in which synchronous communication is replaced by asynchronous send and receive. Proofs of the various theorems and lemma's are delegated to an appendix

Interface refinement in reactive systems (extended abstract)

Suppose one has a system that has a synchronous interface with its environment. Now, suppose that one refines this system and changes its interface to an asynchronous one. Whatever is meant here by refinement, it cannot be standard (process) refinement since the interface actions have changed; nor is it action refinement in the sense that a process is substituted for an action, as the intention presumably is to allow the system to proceed without having to wait until the environment is willing to synchronize. In this paper we propose a notion of interface refinement of which changing synchronous to asynchronous communication is an instance; as is in fact the reverse change. This notion of interface refinement is quite powerful; it generalizes all existing methods w.r.t. the class of interface changes that it allows. The major part of the paper is concerned with developing proof rules with which to verify interface refinement. We use (linear) temporal logic as specification language and an adaptation of the Manna-Pnueli verification framework. The method is illustrated by verifying an interface change in which synchronous communication is replaced by asynchronous send and receive. Proofs of the various theorems and lemma's are delegated to an appendix

A white man in exile: the failure of masculinity in Athol Fugard's Sorrows and Rejoicings

This article explores intersections between understandings of masculinity and nationalism. Etymologically, ‘patriotism’ refers to a love for a fatherland and a patriarchal order; it includes notions of loyalty, honour and a range of qualities often associated with conceptions of masculinity. But if gender remains fixed to these normative constructions, what happens to one’s sense of masculine identity when the national state changes? My interest lies in exploring how white South African men have been repositioned in terms of a shift in their gendered identification, with a reflection on the possibly tragic consequences of maintaining an overly rigid gender role identification. As long as masculinity is embedded within nationalism, it will be caught up within a defensive reactive mode which can turn self-destructive. In order to explore these ideas the article employs as its central metaphor the character of Dawid Olivier, who is the protagonist of Athol Fugard’s Sorrows and Rejoicings (2002)

The continuous heart failure spectrum: moving beyond an ejection fraction classification.

Randomized clinical trials initially used heart failure (HF) patients with low left ventricular ejection fraction (LVEF) to select study populations with high risk to enhance statistical power. However, this use of LVEF in clinical trials has led to oversimplification of the scientific view of a complex syndrome. Descriptive terms such as 'HFrEF' (HF with reduced LVEF), 'HFpEF' (HF with preserved LVEF), and more recently 'HFmrEF' (HF with mid-range LVEF), assigned on arbitrary LVEF cut-off points, have gradually arisen as separate diseases, implying distinct pathophysiologies. In this article, based on pathophysiological reasoning, we challenge the paradigm of classifying HF according to LVEF. Instead, we propose that HF is a heterogeneous syndrome in which disease progression is associated with a dynamic evolution of functional and structural changes leading to unique disease trajectories creating a spectrum of phenotypes with overlapping and distinct characteristics. Moreover, we argue that by recognizing the spectral nature of the disease a novel stratification will arise from new technologies and scientific insights that will shape the design of future trials based on deeper understanding beyond the LVEF construct alone

The continuous heart failure spectrum: Moving beyond an ejection fraction classification

Randomized clinical trials initially used heart failure (HF) patients with low left ventricular ejection fraction (LVEF) to select study populations with high risk to enhance statistical power. However, this use of LVEF in clinical trials has led to oversimplification of the scientific view of a complex syndrome. Descriptive terms such as ‘HFrEF’ (HF with reduced LVEF), ‘HFpEF’ (HF with preserved LVEF), and more recently ‘HFmrEF’ (HF with mid-range LVEF), assigned on arbitrary LVEF cut-off points, have gradually arisen as separate diseases, implying distinct pathophysiologies. In this article, based on pathophysiological reasoning, we challenge the paradigm of classifying HF according to LVEF. Instead, we propose that HF is a heterogeneous syndrome in which disease progression is associated with a dynamic evolution of functional and structural changes leading to unique disease trajectories creating a spectrum of phenotypes with overlapping and distinct characteristics. Moreover, we argue that by recognizing the spectral nature of the disease a novel stratification will arise from new technologies and scientific insights that will shape the design of future trials based on deeper understanding beyond the LVEF construct alone. © The Author(s) 2019

Development of floating rafts after the rewetting of cut-over bogs: the importance of peat quality

Contains fulltext : 60321.pdf (publisher's version ) (Closed access)The usual method of restoring cut-over bogs is to rewet the peat surface. but this often leads to the remaining peat layers being deeply inundated. For Sphagnum-dominated vegetation to develop at deeply inundated locations. it is important for floating rafts of buoyant residual peat to develop. In this study. the chemical and physical characteristics of buoyant and inundated peat collected from rewetted cut-over bog were compared. In general. buoyant peat was poorly humified: high methane (CH4) production rates (greater than or equal to2 mumol g(-1) DW day(-1)) were important to ensure buoyancy. Although the peat water CH4 concentrations increased with depth. the CH4 production rates were higher in the uppermost peat layers. High CH4 production rates were related positively with P concentrations and negatively with lignin concentrations. The pH to bulk density ratio (greater than or equal to0.05) also appeared to be a good indicator of CH4 production rates, providing an easy and cheap way to measure. the variable for restoration practitioners. Our results indicated that analysing certain simple characteristics of the residual peat can greatly improve the success of the rewetting measures taken in cut-over bogs. If the analysis reveals that the residual peat is unsuitable for floating raft formation, deep inundation is inappropriate unless suitable peat from other locations can be introduced