An Object-Based Approach to Modelling and Analysis of Failure Properties

In protection systems, when traditional technology is replaced by software, the functionality and complexity of the system is likely to increase. The quantitative evidence normally provided for safety certification of traditional systems cannot be relied upon in software-based systems. Instead there is a need to provide qualitative evidence. As a basis for the required qualitative evidence, we propose an object-based approach that allows modelling of both the application and software domains. From the object class model of a system and a formal specification of the failure properties of its components, we generate a graph of failure propagation over object classes, which is then used to generate a graph in terms of object instances in order to conduct fault tree analysis. The model is validated by comparing the resulting minimal cut sets with those obtained from the fault tree analysis of the original system. The approach is illustrated on a case study based on a protection system from..

Coherent Topological Charge Structure in CPN−1CP^{N-1} Models and QCD

In an effort to clarify the significance of the recent observation of long-range topological charge coherence in QCD gauge configurations, we study the local topological charge distributions in two-dimensional $CP^{N-1}$ sigma models, using the overlap Dirac operator to construct the lattice topological charge. We find long-range sign coherence of topological charge along extended one-dimensional structures in two-dimensional spacetime. We discuss the connection between the long range topological structure found in $CP^{N-1}$ and the observed sign coherence along three-dimensional sheets in four-dimensional QCD gauge configurations. In both cases, coherent regions of topological charge form along membrane-like surfaces of codimension one. We show that the Monte Carlo results, for both two-dimensional and four-dimensional gauge theory, support a view of topological charge fluctuations suggested by Luscher and Witten. In this framework, the observed membranes are associated with boundaries between ``k-vacua,'' characterized by an effective local value of $\theta$ which jumps by $\pm 2\pi$ across the boundary.Comment: 26 page

Narrow Linewidth 780 nm Distributed Feedback Lasers for Cold Atom Quantum Technology

Cold atom quantum technology systems have a wide range of potential applications which includes atomic clocks, rotational sensors, inertial sensors, quantum navigators, magnetometers and gravimeters. The UK Quantum Technology Hub in Sensors and Metrology has the aim of developing miniature cold atom systems using an approach similar to that pioneered by the chip scale atomic clock where microfabricated vacuum chambers have atomic transitions excited and probed by lasers. Whilst narrow linewidth Ti:Sa and external cavity diode lasers have been required for cooling and control, such lasers are too large, power hungry and expensive for future miniature cold atom systems. Here we demonstrate 1 mm long 780.24 nm GaAs/AlGaAs distributed feedback (DFB) lasers aimed at 87Rb cold atom systems operating at 20 ˚C with over 50 mW of power and side-mode suppression ratios of 46 dB using sidewall gratings and no regrowth. Rb spectroscopy is used to demonstrate linewidths below the required 6.07 MHz natural linewidth of the 87Rb D2 optical transition used for cooling. Initial packaged fibre-coupled devices demonstrate lifetimes greater than 200 hours. We also investigate the use of integrated semiconductor amplifiers (SOAs) and longer devices to further reduce the linewidths well below 1 MHz. A range of options to control the populations of electrons in the hyperfine split energy levels spaced by 3.417 GHz are examined. Two integrated lasers, integrated electro-absorption modulators (EAMs) and the direct modulation of a single DFB laser approaches are investigated and we will discuss which is best suited to integrated cold atom systems

Extensive small bowel gangrene at mid-term pregnancy with fruitful outcome

Intestinal obstruction during pregnancy is very rare. The mechanical intestinal obstruction was mostly due to adhesion from previous surgery.  Pregnancy may mask the symptoms of intestinal obstruction, and virgin abdomen adds to the ambiguity of the diagnosis. The mortality and morbidity increased for the mother and the fetus in the presence of bowel gangrene. We present a case of intestinal obstruction at mid-term pregnancy with extensive small bowel gangrene which necessitates right hemicolectomy and ends with a good outcome for the mother and fetus

Incidence of surgical site infection following caesarean section: a systematic review and meta-analysis protocol

Introduction: Caesarean section (CS) rates have increased globally during the past three decades. Surgical site infection (SSI) following CS is a common cause of morbidity with reported rates of 3 -15%. SSI represents a substantial burden to the health system including increased length of hospitalisation and costs of postdischarge care. The definition of SSI varies with the postoperative follow-up period among different health systems, resulting in differences in the reporting of SSI incidence. We propose to conduct the first systematic review and meta-analysis to determine the pooled estimate for the overall incidence of SSI following CS. Methods and analysis: We will perform a comprehensive search to identify all potentially relevant published studies on the incidence of SSI following CS reported from 1992 in the English language. Electronic databases including PubMed, CINAHL, EMBASE and Scopus will be searched using a detailed search strategy. Following study selection, full-text paper retrieval, data extraction and synthesis, we will appraise study quality and risk of bias and assess heterogeneity. Incidence data will be combined where feasible in a meta-analysis using Stata software and fixed-effects or random-effects models as appropriate. This systematic review will be reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Ethics and dissemination: Ethical approval is not required as this review will use published data. The review will evaluate the overall incidence of SSI following CS and will provide the first quantitative estimate of the magnitude of SSI. It will serve as a benchmark for future studies, identify research gaps and remaining challenges, and emphasise the need for appropriate prevention and control measures for SSI post-CS. A manuscript reporting the results of the systematic review and meta-analysis will be submitted to a peer-reviewed journal and presented at scientific conferences. Trial registration number CRD42015024426

Unusual Lymphomas Developing in Chronic Lymphocytic Leukemia

We report three patients with chronic lymphocytic leukemia (CLL) who developed malignant lymphomas of unusual character and modes of presentation. Two of the patients had received low doses of chlorambucil for several years before they developed malignant lymphoma, diffuse, large cell type (LCL). In one of these patients LCL manifested as a grossly evident osteolytic lesion. In the second patient LCL developed initially as a localized lesion in the iliac bone. Both patients died within a few weeks after LCL was diagnosed. The third patient, who was found to have CLL during a routine examination, did not receive any therapy for the leukemia. Within six months the patient developed diffuse malignant lymphoma, mixed small and large cell type, with total extinction of the leukemic component. The disease responded favorably to chemotherapy for lymphoma, and the patient is alive with minimal residual disease at this time. Immunohistochemical studies in all three patients suggested transformation or dedifferentiation of the original neoplastic lymphoid clone rather than de novo appearance of another neoplasm