Work domain analysis and sensors II: Pasteurizer II case study

In this paper we use sensor-annotated abstraction hierarchies (Reising & Sanderson, 1996, 2002a,b) to show that unless appropriately instrumented, configural displays designed according to the principles of ecological interface design (EID) might be vulnerable to misinterpretation when sensors become unreliable or are unavailable. Building on foundations established in Reising and Sanderson (2002a) we use a pasteurization process control example to show how sensor-annotated AHs help the analyst determine the impact of different instrumentation engineering policies on a configural display that is part of an ecological interface. Our analyses suggest that configural displays showing higher-order properties of a system are especially vulnerable under some conservative instrumentation configurations. However, sensor-annotated AHs can be used to indicate where corrective instrumentation might be placed. We argue that if EID is to be effectively employed in the design of displays for complex systems, then the information needs of the human operator need to be considered while instrumentation requirements are being formulated. Rasmussen's abstraction hierarchy-and particularly its extension to the analysis of information captured by sensors and derived from sensors-may therefore be a useful adjunct to up-stream instrumentation design. (C) 2002 Elsevier Science Ltd. All rights reserved.

Work domain analysis and sensors I: principles and simple example

In this paper we establish a foundation for understanding the instrumentation needs of complex dynamic systems if ecological interface design (EID)-based interfaces are to be robust in the face of instrumentation failures. EID-based interfaces often include configural displays which reveal the higher-order properties of complex systems. However, concerns have been expressed that such displays might be misleading when instrumentation is unreliable or unavailable. Rasmussen's abstraction hierarchy (AH) formalism can be extended to include representations of sensors near the functions or properties about which they provide information, resulting in what we call a sensor-annotated abstraction hierarchy. Sensor-annotated AHs help the analyst determine the impact of different instrumentation engineering policies on higher-order system information by showing how the data provided from individual sensors propagates within and across levels of abstraction in the AH. The use of sensor-annotated AHs with a configural display is illustrated with a simple water reservoir example. We argue that if EID is to be effectively employed in the design of interfaces for complex systems, then the information needs of the human operator need to be considered at the earliest stages of system development while instrumentation requirements are being formulated. In this way, Rasmussen's AH promotes a formative approach to instrumentation engineering. (C) 2002 Elsevier Science Ltd. All rights reserved.

Speciation and distribution of the members of the Anopheles punctulatus (Diptera : Culicidae) group in Papua New Guinea

Mosquito collections were made throughout the mainland of Papua New Guinea to identify the members of the Anopheles punctulatus group present and to determine their distribution. Identification was made using morphology, DNA hybridization, and polymerase chain reaction (PCR)-RFLP analysis. Nine members of the group were identified: An. farauti s.s. Laveran, An.farauti 2, An. koliensis Owen, and An. punctulatus Donitz, were common and widespread; An. farauti 4 was restricted to the north of the central ranges where it was common; An. farauti 6 was found only in the highlands above 1,000 m; and An. farauti 3, An. sp. near punctulatus and An. clowi Rozeboom & Knight were uncommon and had restricted distributions. Identification of An. koliensis and An. punctulatus using proboscis morphology was found to be unreliable wherever An. farauti 4 occurred. The distribution and dispersal of the members of the An. punctulatus group is discussed in regard to climate, larval habitats, distance from the coast, elevation, and proximity to human habitation.

An alternative method for predicting body mass: the case of the Pleistocene marsupial lion

Accurate estimates of body mass in fossil taxa are fundamental to paleobiological reconstruction. Predictive equations derived from correlation with craniodental and body mass data in extant taxa are the most commonly used, but they can be unreliable for species whose morphology departs widely from that of living relatives. Estimates based on proximal limb-bone circumference data are more accurate but are inapplicable where postcranial remains are unknown. In this study we assess the efficacy of predicting body mass in Australian fossil marsupials by using an alternative correlate, endocranial volume. Body mass estimates for a species with highly unusual craniodental anatomy, the Pleistocene marsupial lion (Thylacoleo carnifex), fall within the range determined on the basis of proximal limb-bone circumference data, whereas estimates based on dental data are highly dubious. For all marsupial taxa considered, allometric relationships have small confidence intervals, and percent prediction errors are comparable to those of the best predictors using craniodental data. Although application is limited in some respects, this method may provide a useful means of estimating body mass for species with atypical craniodental or postcranial morphologies and taxa unrepresented by postcranial remains. A trend toward increased encephalization may constrain the method's predictive power with respect to many, but not all, placental clades.

Genetic covariation of pelvic organ and elbow mobility in twins and their sisters

A range of environmental risk factors, with childbirth the most notable, have been associated with the development of pelvic organ prolapse and urinary incontinence. However, indications of genetic influence (positive family histories, ethnic differences) have prompted research into the heritability of measures of pelvic organ descent and joint mobility, which have also been associated with prolapse and incontinence. Genes appear to influence about half of the variation in these measures and, furthermore, the pelvic organ measures are associated with elbow hyperextension at a phenotypic level (r approximate to .2). We examined these measures in young, nulligravid women to determine if their association is due to a common genetic source. Data were collected from 178 Caucasian female co-twins and non-twin sisters, 50 of whom returned to be retested, which allowed reliability to be estimated and unreliable variance to be isolated in the multivariate analyses. Structural equation modeling was used to estimate genetic associations between latent elbow and bladder mobility factors for which heritabilities were estimated to be 0.80 and 0.64 respectively. The association between these factors appeared to be mediated by common genes (genetic r = .48, non-shared environmental r = -.06), with genes influencing latent elbow mobility accounting for 14% of the variation in latent bladder mobility. We speculate that genes influencing connective tissue structure may underlie this association.

Reliability of the Knee Examination in Osteoarthritis: Effect of Standardization

Objective. To assess the reliability of physical examination of the osteoarthritic (OA) knee by rheumatologists, and to evaluate the benefits of standardization. Methods. Forty-two physical signs and techniques were evaluated using a 6 X 6 Latin square design. Patients with mild to severe knee OA, based on physical and radiographic signs, were examined in random order prior to and following standardization of techniques. For those signs with dichotomous scales, agreement among the rheumatologists was calculated as the prevalence-adjusted bias-adjusted kappa (PABAK), while for the signs with continuous and ordinal scales, a reliability coefficient (R-c) was calculated using analysis of variance. A PABAK of >0.60 and an Re of >0.80 were considered to indicate adequate reliability. Results. Adequate poststandardization reliability was achieved for 30 of 42 physical signs/techniques (71%). The most highly reliable signs identified by physical examination of the OA knee included alignment by goniometer (R-c = 0.99), bony swelling (R-c = 0.97), general passive crepitus (R-c = 0.96), gait by inspection (PABAK = 0.78), effusion bulge sign (R-c = 0.97), quadriceps atrophy (R. = 0.97), medial tibiofemoral tenderness (R-c = 0.94), lateral tibiofemoral tenderness (R-c = 0.85), patellofemoral tenderness by grind test (R-c = 0.94), and flexion contracture (R-c = 0.95). The standardization process resulted in substantial improvements in reliability for evaluation of a number of physical signs, although for some signs, minimal or no effect of standardization was noted. After standardization, warmth (PABAK = 0.14), medial instability at 30degrees flexion (PABAK = 0.02), and lateral instability at 30degrees flexion (PABAK = 0.34) were the only 3 signs that were highly unreliable. Conclusion. With the exception of physical examinations for instability, a comprehensive knee examination can be performed with adequate reliability. Standardization further improves the reliability for some physical signs and techniques. The application of these findings to future OA studies will contribute to improved outcome assessments in OA.

Quantitative myocardial contrast echocardiography for prediction of thrombolysis in myocardial infarction flow in acute myocardial infarction

Clinical evaluation of arterial potency in acute ST-elevation myocardial infarction (STEMI) is unreliable. We sought to identify infarction and predict infarct-related artery potency measured by the Thrombolysis In Myocardial Infarction (TIMI) score with qualitative and quantitative intravenous myocardial contrast echocardiography (MCE). Thirty-four patients with suspected STEMI underwent MCE before emergency angiography and planned angioplasty. MCE was performed with harmonic imaging and variable triggering intervals during intravenous administration of Optison. Myocardial perfusion was quantified offline, fitting an exponential function to contrast intensity at various pulsing intervals. Plateau myocardial contrast intensity (A), rate of rise (beta), and myocardial flow (Q = A x beta) were assessed in 6 segments. Qualitative assessment of perfusion defects was sensitive for the diagnosis of infarction (sensitivity 93%) and did not differ between anterior and inferior infarctions. However, qualitative assessment had only moderate specificity (50%), and perfusion defects were unrelated to TIMI flow. In patients with STEMI, quantitatively derived myocardial blood flow Q (A x beta) was significantly lower in territories subtended by an artery with impaired (TIMI 0 to 2) flow than those territories supplied by a reperfused artery with TIMI 3 flow (10.2 +/- 9.1 vs 44.3 +/- 50.4, p = 0.03). Quantitative flow was also lower in segments with impaired flow in the subtending artery compared with normal patients with TIMI 3 flow (42.8 +/- 36.6, p = 0.006) and all segments with TIMI 3 flow (35.3 +/- 32.9, p = 0.018). An receiver-operator characteristic curve derived cut-off Q value of

Grain size measurements in Mg-Al high pressure die castings using electron back-scattered diffraction (EBSD)

Optical metallographic techniques for grain-size measurement give unreliable results for high pressure diecast Mg-Al alloys and electron back-scattered diffraction mapping (EBSD) provides a good tool for improving the quality of these measurements. An application of EBSD mapping to this question is described, and data for some castings are presented. Ion-beam milling was needed to prepare suitable samples, and this technique is detailed. As is well-known for high pressure die castings, the grain size distribution comprises at least two populations. The mean grain size of the fine-grained population was similar in both AZ91 and AM60 and in two casting thicknesses (2 mm and 5 mm) and, contrary to previously published reports, it did not vary with depth below the surface.

Speleothem master chronologies: combined Holocene O-18 and C-13 records from the North Island of New Zealand and their palaeoenvironmental interpretation

The stable isotope records of four stalagmites dated by 19 TIMS uranium series ages are combined to produce master chronologies for delta(18)O and delta(13)C The delta(18)O records display good overall coherence, but considerable variation in detail. Variability in the delta(13)C records is greater, but general trends can still be discerned. This implies that too fine an interpretation of the structure of individual isotopic records can be unreliable. Speleothem delta(18)O values are demonstrated to show a positive relationship with temperature by comparing trends with other proxy records, but also to respond negatively to rainfall amount. Speleothem delta(13)C is considered to be most influenced by rainfall. The postglacial thermal optimum occur-red around 10.8 ka BP, which is similar in timing to Antarctica but up to 2000 years earlier than most Northern Hemisphere sites. Increasingly negative delta(18)O values after 7.5 ka BP indicate that temperatures declined to a late mid-Holocene minimum centred around 3 ka BP, but more positive values followed to mark a warm peak about 750 years ago which coincided with the 'Mediaeval Warm Period' of Europe. Low 5110 values at 325 years BP suggest cooling coincident with the 'Little Ice Age'. A marked feature of the delta(13)C record is an asymmetric periodicity averaging c. 2250 years and amplitude of c. 1.9parts per thousand. It is concluded that this is mainly driven by waterbalance variations with negative swings representing particularly wet intervals. The 5110 record shows a higher-frequency cyclicity with a period of c. 500 years and an amplitude of c. 0.25 parts per thousand. This is most likely to be temperature-driven, but some swings may have been amplified by precipitation.

The cross-entropy method for network reliability estimation

Consider a network of unreliable links, modelling for example a communication network. Estimating the reliability of the network-expressed as the probability that certain nodes in the network are connected-is a computationally difficult task. In this paper we study how the Cross-Entropy method can be used to obtain more efficient network reliability estimation procedures. Three techniques of estimation are considered: Crude Monte Carlo and the more sophisticated Permutation Monte Carlo and Merge Process. We show that the Cross-Entropy method yields a speed-up over all three techniques.

Application of the cross-entropy method to the buffer allocation problem in a simulation-based environment

The buffer allocation problem (BAP) is a well-known difficult problem in the design of production lines. We present a stochastic algorithm for solving the BAP, based on the cross-entropy method, a new paradigm for stochastic optimization. The algorithm involves the following iterative steps: (a) the generation of buffer allocations according to a certain random mechanism, followed by (b) the modification of this mechanism on the basis of cross-entropy minimization. Through various numerical experiments we demonstrate the efficiency of the proposed algorithm and show that the method can quickly generate (near-)optimal buffer allocations for fairly large production lines.

Optimal preventive maintenance of leased equipment with corrective minimal repairs

For leased equipment, the lessor carries out the maintenance of the equipment. Usually, the contract of lease specifies the penalty for equipment failures and for repairs not being carried out within specified time limits. This implies that optimal preventive maintenance policies must take these penalty costs into account and properly traded against the cost of preventive maintenance actions. The costs associated with failures are high as unplanned corrective maintenance actions are costly and the resulting penalties due to lease contract terms being violated. The paper develops a model to determine the optimal parameters of a preventive maintenance policy that takes into account all these costs to minimize the total expected cost to the lessor for new item lease. The parameters of the policy are (i) the number of preventive maintenance actions to be carried out over the lease period, (ii) the time instants for such actions, and (iii) the level of action. (c) 2005 Elsevier B.V. All rights reserved.

Reliably estimating the effect of toxicants on fertilization success in marine broadcast spawners

Recently, there has been a dramatic increase in the number of ecotoxicological studies examining the effects of toxicants on fertilization success in marine broadcast spawners and it appears that this life-history stage is one of the most vulnerable to toxicants. Most of the studies examining this issue use single sperm concentrations in their assays. Here, I discuss recent advances in fertilization ecology that suggest this technique has some severe limitations resulting in unreliable estimations of the size and direction of toxicant effects. I present an alternative assay technique and two metrics (F-max and [Sperm](max)) that will reliably estimate the size of a toxicant's effect on fertilization success. This technique has the added advantage of making comparisons among species and studies easier without an impractical increase in effort. (c) 2006 Elsevier Ltd. All rights reserved.