Contamination of meat with microorganisms during slaughter is inevitable. Hygiene management systems (HMSs) such as the Hygiene Assessment System (HAS) and Hazard Analysis Critical Control Point (HACCP) are used to prevent the contamination of beef with both spoilage and pathogenic microorganisms during slaughter. This study compared the effect of the HAS alone and a combination of HAS + HACCP on the microbiological quality of beef and investigated the survival of Escherichia coli O157:H7 co-cultured with different levels of Pseudomonas fluorescens and Lactobacillus plantarum on fresh beef. HAS alone and HAS combined with HACCP systems were each represented by two abattoirs. Sponge swab samples were collected from chilled beef carcasses for indicator organisms: Aerobic Plate Counts (APC), Enterobacteriaceae, Pseudomonas spp., and lactic acid bacteria. Swabs were also collected for pathogenic bacteria: E. coli O157:H7, Staphylococcus aureus and Salmonella spp. There was no significant difference between the microbiological quality of beef carcasses processed in the abattoirs with the HAS and that of beef carcasses processed in abattoirs with combined HAS + HACCP. E. coli O157:H7 was isolated from carcasses processed in an abattoir with the combined HAS + HACCP system. Moreover, although overall S. aureus counts at all abattoirs were comparable, a higher incidence (47% of carcasses) was obtained from an abattoir with combined HAS + HACCP. Salmonella spp. was not detected during the study. The microbiological quality of beef at HAS abattoirs is not significantly different to that of beef processed at HAS + HACCP abattoirs. The combined HAS + HACCP did not prevent contamination of beef carcasses with E. coli O157:H7 and S. aureus. Effective implementation of HAS can reduce contamination of beef with spoilage and pathogenic microorganisms. The effect of different levels of P. fluorescens (102 and 106 log10 cfu/ml) and L. plantarum (102 and 104 log10 cfu/ml) on the survival of E. coli O157:H7 on beef loins was investigated. Sterile beef loins inoculated with E. coli O157:H7 and P. fluorescens were aerobically stored for 7 days at 4°C, while those inoculated with E. coli O157:H7 and L. plantarum were vacuum-packaged and stored for 8 weeks at 4°C. APC, E. coli O157:H7 and either P. fluorescens or L. plantarum counts were determined at different storage intervals. For the aerobically packaged beef loins, E. coli O157:H7 was detected throughout the 7-day storage period regardless of the P. fluorescens level in the inoculum. For the vacuum packaged beef loins, similar inoculum levels of E. coli O157:H7 and L. plantarum allowed E. coli O157:H7 to survive until week 5 of storage, while a higher inoculum level of L. plantarum inhibited E. coli O157:H7 from week 3. Once fresh beef has been contaminated with E. coli O157:H7 the level of P. fluorescens in the background flora does not inhibit its survival and growth. However, under vacuum storage, the application of L. plantarum as a biopreservative inhibits the survival of E. coli O157:H7 on beef. Comprehensive strengthening of preventive strategies is required to eliminate contamination of beef carcasses with E. coli O157:H7. Bacterial contamination of carcasses during slaughter is inevitable. Effective implementation of HAS at abattoirs produces beef carcasses of microbiological quality comparable to that produced through the use of combined HAS and HACCP. While the level of P. fluorescens on beef does not inhibit the survival of E. coli O157:H7 on aerobically stored beef, the combination of L. plantarum, and low storage temperature inhibits the survival of this pathogen on beef under vacuum storage. / Thesis (PhD)--University of Pretoria, 2011. / Food Science / unrestricted

The purchase of medical devices involves engaging various stakeholders as well as balancing clinical, technical and financial requirements. Failure to consider these requirements can lead to wider consequences in the delivery of care. This study first builds a general knowledge base of current purchasing practice in a sample of NHS Trusts, which confirms the direction and guidance given by policy documents and literature as to the extent of the challenges faced by purchasing stakeholders. This then leads to an analysis to identify inefficiencies in the purchasing process, and how such practice can lead to risks in the delivery of care. These risks range from injury to individuals, impacts to the healthcare delivery service, and financial and litigation risks. Finally, a framework that highlights these potential risks in the life-cycle of medical devices in hospitals is presented. Key policy guidance has encouraged both researchers and implementers of healthcare services to approach patient safety from a systems perspective, acknowledging that medical device errors are not only directly related to device design, but to the design of the healthcare delivery service system in which the device operates. Little evidence exists of successfully applying systems approaches specifically to medical device purchasing practice. Medical device purchasing, because of its implications to patient safety on the one hand, and the uniqueness of the healthcare context, requires a unique approach. By demonstrating the influence of purchasing practice to service delivery and patient care, the thesis made is that taking a holistic systems approach is one method to improve device purchasing practice, and hence influence better care.

This thesis investigates the efficiency of a design optimisation scheme that is appropriate for systems which require a high likelihood of functioning on demand. Traditional approaches to the design of safety critical systems follow the preliminary design, analysis, appraisal and redesign stages until what is regarded as an acceptable design is achieved. For safety systems whose failure could result in loss of life it is imperative that the best use of the available resources is made and a system which is optimal, not just adequate, is produced. The object of the design optimisation problem is to minimise system unavailability through manipulation of the design variables, such that limitations placed on them by constraints are not violated. Commonly, with mathematical optimisation problem; there will be an explicit objective function which defines how the characteristic to be minimised is related to the variables. As regards the safety system problem, an explicit objective function cannot be formulated, and as such, system performance is assessed using the fault tree method. By the use of house events a single fault tree is constructed to represent the failure causes of each potential design to overcome the time consuming task of constructing a fault tree for each design investigated during the optimisation procedure. Once the fault tree has been constructed for the design in question it is converted to a BDD for analysis. A genetic algorithm is first employed to perform the system optimisation, where the practicality of this approach is demonstrated initially through application to a High-Integrity Protection System (HIPS) and subsequently a more complex Firewater Deluge System (FDS). An alternative optimisation scheme achieves the final design specification by solving a sequence of optimisation problems. Each of these problems are defined by assuming some form of the objective function and specifying a sub-region of the design space over which this function will be representative of the system unavailability. The thesis concludes with attention to various optimisation techniques, which possess features able to address difficulties in the optimisation of safety critical systems. Specifically, consideration is given to the use of a statistically designed experiment and a logical search approach.

With increasingly complex safety-critical systems like healthcare being developed and managed, there is a need for a tool that allows us to understand their complexity, design better strategies and guide effective change. System dynamics (SD) has been widely used in modelling across a range of applications from socio-economic to engineering systems, but its potential has not yet been fully realised as a tool for understanding trade-off dynamics between safety and efficiency in healthcare. SD has the potential to provide balanced and trustworthy insights into strategic decision making. Participatory SD modelling and learning is particularly important in healthcare since problems in healthcare are difficult to comprehend due to complexity, involvement of multiple stakeholders in decision making and fragmented structure of delivery systems. Participatory SD modelling triangulates stakeholder expertise, data and simulation of implementation plans prior to attempting change. It provides decision-makers with an evaluation and learning tool to analyse impacts of changes and determine which input data is most likely to achieve desired outcomes. This thesis aims to examine the feasibility of applying participatory SD modelling approach to safe and efficient staffing level management within hospital pharmacies and to evaluate the utility and usability of participatory SD modelling approach as a learning method. A case study was conducted looking at trade-offs between dispensing backlog (efficiency) and dispensing errors (safety) in a hospital pharmacy dispensary in an English teaching hospital. A participatory modelling approach was employed where the stakeholders from the hospital pharmacy dispensary were engaged in developing an integrated qualitative conceptual model. The model was constructed using focus group sessions with 16 practitioners consisting of labelling and checking practitioners, the literature and hospital pharmacy databases. Based on the conceptual model, a formal quantitative simulation model was then developed using an SD simulation approach, allowing different scenarios and strategies to be identified and tested. Besides the baseline or business as usual scenario, two additional scenarios (hospital winter pressures and various staffing arrangements, interruptions and fatigue) identified by the pharmacist team were simulated and tested using a custom simulation platform (Forio: user-friendly GUI) to enable stakeholders to play out the likely consequences of the intervention scenarios. We carried out focus group-based survey of 21 participants working in the hospital pharmacy dispensaries to evaluate the applicability, utility and usability of how participatory SD enhanced group learning and building of shared vision for problems within the hospital dispensaries. Findings from the simulation illustrate the knock-on impact rework has on dispensing errors, which is often missing from the traditional linear model-based approaches. This potentially downward-spiral knock-on effect makes it more challenging to deal with demand variability, for example, due to hospital winter pressures. The results provide pharmacy management in-depth insights into potential downward-spiral knock-on effects of high workload and potential challenges in dealing with demand variability. Results and simulated scenarios reveal that it is better to have a fixed adequate staff number throughout the day to keep backlog and dispensing errors to a minimum than calling additional staff to combat growing backlog; and that whilst having a significant amount of trainees might be cost efficient, it has a detrimental effect on dispensing errors (safety) as number of rework done to correct the errors increases and contributes to the growing backlog. Finally, capacity depletion initiated by high workload (over 85% of total workload), even in short bursts, has a significant effect on the amount of rework. Evaluative feedback revealed that participatory SD modelling can help support consensus agreement, thus gaining a deeper understanding of the complex interactions in the systems they strive to manage. The model introduced an intervention to pharmacy management by changing their mental models on how hospital winter pressures, various staffing arrangements, interruptions and fatigue affect productivity and safety. Although the outcome of the process is the model as an artefact, we concluded that the main benefit is the significant mental model change on how hospital winter pressures, various staffing arrangements, interruptions and fatigue are interconnected, as derived from participants involvement and their interactions with the GUI scenarios. The research contributes to the advancement of participatory SD modelling approach within healthcare by evaluating its utility and usability as a learning method, which until recently, has been dominated by the linear reductionist approaches. Methodologically, this is one of the few studies to apply participatory SD approach as a modelling tool for understanding trade-offs dynamics between safety and efficiency in healthcare. Practically, this research provides stakeholders and managers, from pharmacists to managers the decision support tools in the form of a GUI-based platform showcasing the integrated conceptual and simulation model for staffing level management in hospital pharmacy.

Multi-trailer articulated heavy vehicles (MTAHVs) exhibit unstable motion modes at high speeds, including jack-knifing, trailer swing, and roll-over. These unstable motion modes may lead to fatal accidents. On the other hand, these vehicle combinations have poor maneuverability at low speeds. Of all contradictory design criteria of MTAHVs, the trade-off relationship between the maneuverability at low speeds and the lateral stability at high speeds is the most important and fundamental. This trade-off relationship has not been adequately addressed. The goal of this research is to address this trade-off relationship through the design optimization of MTAHVs with active safety systems. A parallel design optimization (PDO) method is developed and applied to the design of MTAHVs with integrated active safety systems, which involve active trailer steering (ATS) control, anti-roll (AR) control, differential braking (BD) control, and a variety of combinations of these three control strategies. To derive model-based controllers, a single-trailer articulated heavy vehicle (STAHV) model with 5 degrees of freedom (DOF) and a MTAHV model with 7 DOF are generated. The vehicle models are validated with those derived using a commercial software package, TruckSim, in order to examine their applicability for the design optimization of MTAHVs with active safety systems. The PDO method is implemented to perform the concurrent design of the plant (vehicle model) and controllers. To simulate the closed-loop testing maneuvers, a driver model is developed and it is used to drive the virtual vehicle following the prescribed path. Case studies indicate that the PDO method is effective for identifying desired design variables and predicting performance envelopes in the early design stages of MTAHVs with active safety systems. / UOIT

Broadcast communications is critically important in vehicular networks. Many safety applications need safety warning messages to be broadcast to all vehicles present in an area. In this thesis, we propose a novel repetition-based broadcast protocol based on ``optical orthogonal codes.'' Optical orthogonal codes are used because of their ability to reduce the possibility of collision. We present a detailed mathematical analysis for obtaining the probability of success and the average delay. Furthermore, we propose to use coding to increase network throughput, and ``adaptive elimination'' of potentially colliding transmissions to further increase reliability. We show, by analysis and simulations, that the proposed protocol outperforms existing repetition-based ones and provides reliable broadcast communications and can reliably deliver safety messages under load conditions deemed to be common in vehicular environments. We also show that the proposed protocol is able to provide different levels of quality of service.

Broadcast communications is critically important in vehicular networks. Many safety applications need safety warning messages to be broadcast to all vehicles present in an area. In this thesis, we propose a novel repetition-based broadcast protocol based on ``optical orthogonal codes.'' Optical orthogonal codes are used because of their ability to reduce the possibility of collision. We present a detailed mathematical analysis for obtaining the probability of success and the average delay. Furthermore, we propose to use coding to increase network throughput, and ``adaptive elimination'' of potentially colliding transmissions to further increase reliability. We show, by analysis and simulations, that the proposed protocol outperforms existing repetition-based ones and provides reliable broadcast communications and can reliably deliver safety messages under load conditions deemed to be common in vehicular environments. We also show that the proposed protocol is able to provide different levels of quality of service.

As active safety systems installed in vehicles become more common and more sophisticated, a concise method of testing them in conditions as close to real risk situations as possible becomes necessary. This study looks at the possibilities of developing use cases, using video recordings of real risk situations, obtained through naturalistic driving studies. The concept of conflicts is explored as a substitute to actual accidents. A method of finding conflicts in a large data material from looking at the acceleration signal and its derivative, referred to as jerk is also sought. These possibilities are tried on material from a previously conducted naturalistic driving study. The results are an improvement in the ability to find conflict situations automatically, and a suggestion to how use cases can be produced from video recordings of conflicts obtained through naturalistic driving studies. The DREAM framework is used and modified in order to aid with data collection and interpretation.

Syftet med denna studie har varit att, med utgångspunkt från marinens haveristatistik för grundstötningar, söka dominerande riskfaktorer för fartygens framförande, se i vilken omfattning uppföljning genomförs och hur dragna erfarenheten används och kan utvecklas inom militär sjöfart. Vi har även undersökt om det går att finna några gemensamma orsakssamband mellan olika attribut för fartyg som grundstöter.   De viktigaste iakttagelserna i studierna är att:   •    risker i samband med praktisk navigationsutbildning i skärgård bör analyseras vidare, varvid kommunicerade färdighetsnivåer, dess bibehållande och examination utgör centrala delar •    risker i samband med omorganiseringar och nya organisationer bör klarläggas •    risker vid nya fartygssystem eller metoder bör analyseras •    avvikelsesystemet i Försvarsmaktens sjösäkerhetssystem kan i sig angränsa till större avvikelse •    systemet fungerar inte fullt ut, då förmågan brister i att långsiktigt och systematiskt identifiera, analysera och förankra betydelsefull kunskap •    avvikelserapporteringssystemet, DIUS-M, har stora brister. Återrapportering, revisionsresultat och rapportering av ”närahändelser/near misses” inom nautik saknas i stort sett helt. Hanteringen av förbättringsförslag inryms inte i DIUS-M. Detta har sammantaget sannolikt givit en låg rapporteringsbenägenhet. Rapporterna är inte alltid primärdata •    sjösäkerhetssystemet saknar balans mellan korrigerande åtgärder och ”Lessons Learned” •    trender kan ej statistiskt visas i förhållande mot fartygens nyttjande och således är resultat av åtgärder svåra att överblicka •    upprepade anmärkningar i revisionsresultat för avvikelsehanteringen kvarstår •    erfarenheter ur sjösäkerhetssystemet och nautik behandlas inte i marinens erfarenhetsprocess •    klassificering av ”performance shaping factors” saknas i analyserna, vilket försvårar statistisk tolkning •    verksamheten rörande förbättringsförlag är idag otydlig och disharmoniserar helt i styrande dokument •    införandet av gemensamma regler för militär sjöfart har förbättrat fartygens nautisk-tekniska status och sannolikt minimerat olyckor.   Vi har inte funnit några beskrivna metoder för att hindra ett sluttande plan, s.k. negativ nedärvning, rörande färdigheter inom den praktiska navigationskonsten, efter att den programbundna sjöofficersutbildningen genomförts. Detta trots att högre krav på både färdighet och erfarenheter finns. Rollerna som skapar lärande behöver identifieras, beskrivas och kravsättas på ett tydligare sätt Tillräckliga resurser finns för att med små medel kunna starta en levande avvikelsehantering och erfarenhetsprocess.   Delresultatet visade att marinens fartyg grundstöter oftare då någon form av navigationsutbildning genomförs och att analyserna ofta avslutats där de ur ett evalueringsperspektiv börjar bli intressanta. Utifrån det påträffade sambanden genomfördes några försök att reda ut gångtider och exponeringstider för riskattributet utbildning. Vidare undersöktes förekomsten av utvärderingsmodeller för sjöfarten samt marinens möjlighet till att erfarenhetshantera sitt avvikelsesystem.   En ansats till förslag om erfarenhetshantering för att avvikelsesystemet skall uppfylla Försvarsmaktens manual sjösäkerhet (FMMS) redovisas. / The aim of this study has been that, starting from a marine accident statistics for the groundings, searching dominant risk factors for ships' performance, see the extent to which follow-up is carried out and how it uses and can be drawn from experience developing within military shipping. We have also examined whether it is possible to find some common causal link between the various attributes of the ship groundings/stranding.   The main findings of this study : risks associated with practical navigation practice in the archipelago should be analyzed further.   Skill levels and examination forms are the central parts risks in connection with reorganization and new organizations have to be clarified risks from new ship systems or new navigational methods should be analyzed SMS system in the armed forces may have probably major “non-conformities” the system does not work fully: capacity gaps in the long term to systematically identify, analyze and take care of important knowledge the reporting system, DIUS-M, has major shortcomings. Feedback, audit results and reporting of "near misses" within nautical missing almost completely. The handling of the suggestions for improvements is not included in DIUS-M. This has probably given a low overall reporting tendency. The reports are not always the primary data lacks balance between rules of corrections and "Lessons Learned" trends cannot statistically shown in relation to the use of the ships and are difficult to visualize repeated identical audit results for the safety management system (SMS) itself as non-confirmative lessons learned from the SMS system and are not take care of  in the Navy’s nautical lessons-learned process classification of "performance shaping factors" are missing from the analyses activity concerning improvement publishers is today unclear and gaping completely in the documents the introduction of common rules for military shipping has improved the ships ' nautical-technical status and likely minimized casualties.   We have not found any procedures to prevent a sloped plane, so-called “negative inheritance”, concerning practical navigation skills in the arts, after the sea officers training. This is despite the fact that the navy has higher demands on both skill and experience. The learning syllabus needs to be identified, described and better demanded.   The Armed Forces have resources to launch a working SMS and lessons-learned process. A part result showed that the Navy ship grounds more frequently when any form of navigation training is conducted and that analyses often terminated where they from an evaluation perspective begins to become interesting. Based on the found relations we do attempts to sort out sea going hours and exposure times for risks when training navigation onboard. It was further examined the presence of evaluation models for maritime traffic, as well as the Navy's ability to evaluate its deviation system.   A proposal for adding a Lessons Learned model to the reporting system for meet the skills of the armed forces SMS (FMMS) is shown.

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