Advanced techniques in reliability model representation and solution

The current tendency of flight control system designs is towards increased integration of applications and increased distribution of computational elements. The reliability analysis of such systems is difficult because subsystem interactions are increasingly interdependent. Researchers at NASA Langley Research Center have been working for several years to extend the capability of Markov modeling techniques to address these problems. This effort has been focused in the areas of increased model abstraction and increased computational capability. The reliability model generator (RMG) is a software tool that uses as input a graphical object-oriented block diagram of the system. RMG uses a failure-effects algorithm to produce the reliability model from the graphical description. The ASSURE software tool is a parallel processing program that uses the semi-Markov unreliability range evaluator (SURE) solution technique and the abstract semi-Markov specification interface to the SURE tool (ASSIST) modeling language. A failure modes-effects simulation is used by ASSURE. These tools were used to analyze a significant portion of a complex flight control system. The successful combination of the power of graphical representation, automated model generation, and parallel computation leads to the conclusion that distributed fault-tolerant system architectures can now be analyzed

User's guide to the Reliability Estimation System Testbed (REST)

The Reliability Estimation System Testbed is an X-window based reliability modeling tool that was created to explore the use of the Reliability Modeling Language (RML). RML was defined to support several reliability analysis techniques including modularization, graphical representation, Failure Mode Effects Simulation (FMES), and parallel processing. These techniques are most useful in modeling large systems. Using modularization, an analyst can create reliability models for individual system components. The modules can be tested separately and then combined to compute the total system reliability. Because a one-to-one relationship can be established between system components and the reliability modules, a graphical user interface may be used to describe the system model. RML was designed to permit message passing between modules. This feature enables reliability modeling based on a run time simulation of the system wide effects of a component's failure modes. The use of failure modes effects simulation enhances the analyst's ability to correctly express system behavior when using the modularization approach to reliability modeling. To alleviate the computation bottleneck often found in large reliability models, REST was designed to take advantage of parallel processing on hypercube processors

Steelhead Habitat Assessment of Three Small Coastal Central California Streams

Anadromous steelhead (Oncorhynchus mykiss) populations on the central coast of California have been reduced to critical levels throughout the last century. Six streams run through the Coast Dairies Property near Davenport, CA; three of the streams are known to support steelhead, and three do not support any known populations. This study examined two physical factors that are potentially limiting steelhead success in the three small streams. The first potential limiting factor examined is low density substrate found in the three streams (Santa Cruz mudstone). The presence of low density substrate could lead to increased risk of redd ‘washout,’ or destruction of the steelhead nest and the associated eggs due to gravel mobility. Alternatively, the presence of low density substrate could shift the size range suitable for spawning. This study used tracer stones of mudstone and granite to populate a logistic regression model that can be used to predict the probability of entrainment for a given particle under defined shear stress conditions. The second potential limiting factor is a migration barrier caused by the presence of a culvert on each stream where it passes under Highway 1. Culverts in the three streams without steelhead and two culverts on streams that have known populations of steelhead were surveyed and modeled using a 1-dimentional hydraulic modeling program. Three separate passage criteria were used to assess if the modeled hydraulic conditions were suitable for steelhead passage. We found that both factors were potentially limiting steelhead success in the three streams. This study shows substantial evidence that the low density mudstone substrate is more mobile than typical granitic particles. The results indicate a mudstone particle has a probability of motion approximately 30% higher than a similar granite particle under the same flow conditions. This increase in mobility could result in increased redd washout frequency, and might limit steelhead spawning success. The results of the culvert modeling study revealed it is highly likely the tunnels are presenting a barrier at most flows. The two study culverts what are known to pass steelhead had noticeably better depth and velocity conditions than the three culverts with unknown passage suitability. One of the three passage criteria, suggested by the National Marine Fisheries Service and the California Department of Fish and Game, indicated none of the five culverts were passable, suggesting that it may be too conservative to reflect the swimming abilities of steelhead on the central coast of California

Examining affective structure in chickens: valence, intensity, persistence and generalization measured using a conditioned place preference test

When measuring animals’ valenced behavioural responses to stimuli, the Conditioned Place Preference (CPP) test goes a step further than many approach-based and avoidance-based tests by establishing whether a learned preference for, or aversion to, the location in which the stimulus was encountered can be generated. We designed a novel, four-chambered CPP test to extend the capability of the usual CPP paradigm to provide information on four key features of animals’ affective responses: valence, scale, persistence and generalization. Using this test, we investigated the affective responses of domestic chickens (Gallus gallus domesticus) to four potentially aversive stimuli: 1. Puffs of air; 2. Sight of (robotic) snake; 3. Sprays of water; 4. Sound of conspecific alarm calls. We found conditioned avoidance of locations associated with the air puffs and water sprays (Friedman’s χ2(3) = 13.323 p > .005; χ2(3) = 14.235 p > .005), but not with the snake and alarm calls. The scale of the learned avoidance was similar for the air puff and water spray stimuli, but persistence and generalization differed. We conclude that the four chambered CPP test can have a valuable role to play in making multi-feature measurements of stimulus-generated affective responses, and we highlight the value of such measurements for improving our understanding of the structure of affect in chickens and other animals

Efficacy of needle-placement technique in radiofrequency ablation for treatment of lumbar facet arthropathy.

BACKGROUND:Many studies have assessed the efficacy of radiofrequency ablation to denervate the facet joint as an interventional means of treating axial low-back pain. In these studies, varying procedural techniques were utilized to ablate the nerves that innervate the facet joints. To date, no comparison studies have been performed to suggest superiority of one technique or even compare the prevalence of side effects and complications. MATERIALS AND METHODS:A retrospective chart review was performed on patients who underwent a lumbar facet denervation procedure. Each patient's chart was analyzed for treatment technique (early versus advanced Australian), preprocedural visual numeric scale (VNS) score, postprocedural VNS score, duration of pain relief, and complications. RESULTS:Pre- and postprocedural VNS scores and change in VNS score between the two groups showed no significant differences. Patient-reported benefit and duration of relief was greater in the advanced Australian technique group (P=0.012 and 0.022, respectively). The advanced Australian technique group demonstrated a significantly greater median duration of relief (4 months versus 1.5 months, P=0.022). Male sex and no pain-medication use at baseline were associated with decreased postablation VNS scores, while increasing age and higher preablation VNS scores were associated with increased postablation VNS scores. Despite increasing age being associated with increased postablation VNS scores, age and the advanced Australian technique were found to confer greater patient self-reported treatment benefit. CONCLUSION:The advanced Australian technique provides a significant benefit over the early Australian technique for the treatment of lumbar facet pain, both in magnitude and duration of pain relief

Obesity prevalence and associated risk factors in outdoor living domestic horses and ponies

Reasons for performing study. The prevalence of obesity in companion animals, including horses and ponies has risen drastically in recent years and risk factors have been little investigated. Horses are unique amongst companion animals in that many are outdoor-living and forage independently on pasture; they also have a dual utility and companionship role. The body condition of wild and free-living equines is known to vary seasonally, yet previous estimates of the prevalence of obesity and associated risk factors in domestic animals do not consider this. Most previous studies were conducted during the summer months when pasture quality is greater and obesity prevalence is likely to be highest. In addition, many previous estimates do not use validated body condition scoring methods and rely on owner reporting.Objectives. To examine the prevalence and risk factors predictive of equine obesity at both the end of winter and the end of summer, in a domestic population of leisure horses with daily access to pasture. Using validated body condition scoring methods and a single, trained observer.Methods. Body condition and belly girth measurements were taken at the end of winter and during the summer in a population of leisure horses (n = 96) with outdoor pasture access for ≥6 h per day. Risk factor information was obtained by two owner questionnaires and analysed statistically using a mixed effects logistic regression model. The dependent variable was obese (BCS ≥ 7/9) or non-obese (BCS < 7/9). Risk factors associated with seasonal change in belly girth were also explored using a mixed effects linear regression model.Results. Obesity prevalence rose significantly from 27.08% at the end of winter to 35.41% during summer (p < 0.001). Breed was the risk factor most strongly associated with obesity (p < 0.001). Supplementary feed was not a strong predictor and there was no association with low intensity structured exercise. As winter BCS increased, the percentage seasonal change in belly girth decreased.Conclusions. Obesity prevalence differed between winter and summer in domestic equines. Supplementary feed and low intensity structured exercise in equines living outdoors for ≥6 h per day had limited or no effect on obesity levels. Seasonal variation in body condition was lower in obese equines.Potential relevance. It is important to consider season when studying equine obesity and obesity-associated disorders. Risk factor analysis suggests preventative measures may need to be breed specific. The metabolic implications of a lessened seasonal change in body condition in obese animals, warrants investigation

Proteomics reveals that a high-fat diet induces rapid changes in hypothalamic proteins related to neuronal damage and inflammation

Peer reviewedPublisher PD

Keep your Kodak busy: monuments of the Great War

This paper draws together two elements of the Photography strand in an extensive interdisciplinary research project looking at memorialisation: (i) a literature review (Hutchinson) that explored the significance of photography and photographs to processes of loss and mourning, remembrance, commemoration and memorialisation during the Great War and throughout the years of pilgrimage and battlefield tourism that follow, and (ii) a sequence of photographs, ‘Keep Your Kodak Busy’ (Nicol). The article integrates discussion from the literature with presentation of a selection of the photographs to show how photography as creative practice contributes to an understanding of the economic, social and cultural influences impacting on loss, grief and remembrance, and forms of commemoration and memorialisation in relation to World War One. The article offers a different experience of photography in this context to its more usual and familiar illustrative and documentary role. The research explored how photography and photographs facilitate and mediate the experience of memorialisation, commemoration and remembrance, the role of photographs as vehicles for mourning and remembering and how, in addition to their role as documents of the processes of memorialisation, commemoration and remembrance, photographs are also sites of memory