Modelling the effect of physical variability on the midwater chlorophyll maximum

A coupled model, employing turbulence closure physics and cell-quota threshold limitation biology, has been used to simulate the evolution of the vertical distribution of phytoplankton in a seasonally stratified shelf sea. Predictions are compared with observations from the North Sea. Variations in surface wind stress, which episodically weaken the thermocline barrier to nutrient input to the photic zone, are shown to make an important contribution to the formation of a midwater chlorophyll maximum in Summer

Using widgets to provide portable services for IMS Learning Design

Since the publication of the IMS LD specification it has been recognised that the lack of a rich set of runtime services is a major barrier to adoption. The approaches taken to resolving this problem are reviewed, and their strengths and limitations identified. A generic widget server developed by the authors is described. Integration of the widget server with the IMS LD runtime system provides an extensible set of services. This has been demonstrated with the creation of widgets for forums, messaging, vote, and Google maps which are provided for users within the context of their role and activities in a Unit of Learning. Authoring and administration are described, showing how the system is both extensible and portable

HST Observations of Giant Arcs: High Resolution Imaging Of Distant Field Galaxies.

We present HST imaging of eight spectroscopically-confirmed giant arcs, pairs and arclets. These objects have all been extensively studied from the ground and we demonstrate the unique advantages of HST imaging in the study of such features by a critical comparison of our data with the previous observations. In particular we present new estimates of the core radii of two clusters (Cl0024+16, A370) determined from lensed features which are identifiable in our HST images. Although our HST observations include both pre- and post-refurbishment images, the depth of the exposures guarantees that the majority of the arcs are detected with diffraction-limited resolution. A number of the objects in our sample are multiply-imaged and we illustrate the ease of identification of such features when working at high resolution. We discuss the morphological and scale information on these distant field galaxies in the light of HST studies of lower redshift samples. We conclude that the dominant population of star-forming galaxies at z=1 is a factor of 1.5-2 times smaller than the similar group in the local field. This implies either a considerable evolution in the sizes of star-forming galaxies within the last $\sim$10 Gyrs or a shift in the relative space densities of massive and dwarf star-forming systems over the same timescale.Comment: 9 pages (no figures), uuencoded, compressed Postscript. Postscript text, tables and figures (803 Kb) available via anonymous ftp in at ftp://ociw.edu//pub/irs/pub/hstarcs.tar.

Cost-effectiveness of left ventricular assist devices (LVADs) for patients with advanced heart failure : analysis of the British NHS Bridge to Transplant (BTT) program

Background: A previous cost-effectiveness analysis showed that bridge to transplant (BTT) with early design left ventricular assist devices (LVADs) for advanced heart failure was more expensive than medical management while appearing less beneficial. Older LVADs were pulsatile, but current second and third generation LVADs are continuous flow pumps. This study aimed to estimate comparative cost-effectiveness of BTT with durable implantable continuous flow LVADs compared to medical management in the British NHS. Methods and results: A semi-Markov multi-state economic model was built using NHS costs data and patient data in the British NHS Blood and Transplant Database (BTDB). Quality-adjusted life years (QALYs) and incremental costs per QALY were calculated for patients receiving LVADs compared to those receiving inotrope supported medical management. LVADs cost £80,569 ($127,887) at 2011 prices and delivered greater benefit than medical management. The estimated probabilistic incremental cost-effectiveness ratio (ICER) was £53,527 ($84,963)/QALY (95%CI: £31,802–£94,853; $50,479–$150,560) (over a lifetime horizon). Estimates were sensitive to choice of comparator population, relative likelihood of receiving a heart transplant, time to transplant, and LVAD costs. Reducing the device cost by 15% decreased the ICER to £50,106 ($79,533)/QALY. Conclusions: Durable implantable continuous flow LVADs deliver greater benefits at higher costs than medical management in Britain. At the current UK threshold of £20,000 to £30,000/QALY LVADs are not cost effective but the ICER now begins to approach that of an intervention for end of life care recently recommended by the British NHS. Cost-effectiveness estimates are hampered by the lack of randomized trials

Cost-effectiveness of left ventricular assist devices (LVADs) for patients with advanced heart failure : analysis of the British NHS Bridge to Transplant (BTT) program

Background: A previous cost-effectiveness analysis showed that bridge to transplant (BTT) with early design left ventricular assist devices (LVADs) for advanced heart failure was more expensive than medical management while appearing less beneficial. Older LVADs were pulsatile, but current second and third generation LVADs are continuous flow pumps. This study aimed to estimate comparative cost-effectiveness of BTT with durable implantable continuous flow LVADs compared to medical management in the British NHS. Methods and results: A semi-Markov multi-state economic model was built using NHS costs data and patient data in the British NHS Blood and Transplant Database (BTDB). Quality-adjusted life years (QALYs) and incremental costs per QALY were calculated for patients receiving LVADs compared to those receiving inotrope supported medical management. LVADs cost £80,569 ($127,887) at 2011 prices and delivered greater benefit than medical management. The estimated probabilistic incremental cost-effectiveness ratio (ICER) was £53,527 ($84,963)/QALY (95%CI: £31,802–£94,853; $50,479–$150,560) (over a lifetime horizon). Estimates were sensitive to choice of comparator population, relative likelihood of receiving a heart transplant, time to transplant, and LVAD costs. Reducing the device cost by 15% decreased the ICER to £50,106 ($79,533)/QALY. Conclusions: Durable implantable continuous flow LVADs deliver greater benefits at higher costs than medical management in Britain. At the current UK threshold of £20,000 to £30,000/QALY LVADs are not cost effective but the ICER now begins to approach that of an intervention for end of life care recently recommended by the British NHS. Cost-effectiveness estimates are hampered by the lack of randomized trials

Design Requirements for Effective Hybrid Decision Making with Evolvable Assembly Systems

This paper examines 10 challenges for making automation a team player (Klein et al., 2004) in the context of Evolvable Assembly Systems (EAS) with the aim of delivering requirements for effective hybrid human-automation decision making. Specific decision making use cases for a demonstrator system were analysed to capture opportunities and requirements for effective human-agent cooperative decision making. These requirements covered agent design, human-machine interface design, context aware computing requirements and human competency. As such, the paper provides concrete examples of how general principles for hybrid decision making can be applied to EAS, and presents a pilot of a method for future requirements elicitation

Design requirements for effective hybrid decision making with Evolvable Assembly Systems

This paper examines 10 challenges for making automation a team player (Klein et al., 2004) in the context of Evolvable Assembly Systems (EAS) with the aim of delivering requirements for effective hybrid human-automation decision making. Specific decision making use cases for a demonstrator system were analysed to capture opportunities and requirements for effective human-agent cooperative decision making. These requirements covered agent design, human-machine interface design, context aware computing requirements and human competency. As such, the paper provides concrete examples of how general principles for hybrid decision making can be applied to EAS, and presents a pilot of a method for future requirements elicitation

Reply to: Punctuated transgression (?): Comment on Oliver, T.S.N., Donaldson, P., Sharples, C., Roach, M., and Woodroffe, C.D. Punctuated progradation of the Seven Mile Beach Holocene barrier system, southeastern Tasmania

Our interpretation of the depositional history of the prograded barrier at Seven Mile Beach in Tasmania, described in Oliver et al. (2017a), was based on the morphology of ridges apparent in the LiDAR-based digital elevation data and a sample of 14 optically-stimulated luminescence (OSL) ages. Dougherty (2018) has identified gaps in the chronology and speculated that progradation may have occurred as sea level fell from a mid-Holocene highstand inappropriately applying sea-level curves from mainland Australia. Despite a highstand being inferred by early research in Tasmania, glacio-isostatic modelling and recent sea-level studies adopted a prevailing view that excluded a highstand. Our observations led us to question this prevailing view and to suggest that it might be appropriate to reopen the debate on Holocene sea-level change in Tasmania. We welcome the renewed interest in the chronology and sea-level history of this prograded barrier, and look forward to further clarification based on new evidence. The site may have the potential to become one of the more continuous and better-constrained sea-level records in southern Australia

How stress affects functional near-infrared spectroscopy (fNIRS) measurements of mental workload

Recent work has demonstrated that functional Near-Infrared Spectroscopy has the potential to measure changes in Mental Workload with increasing ecological validity. It is not clear, however, whether these measurements are affected by anxiety and stress of the workload, where our informal observations see some participants enjoying the workload and succeeding in tasks, while others worry and struggle with the tasks. This research evaluated the effects of stress on fNIRS measurements and performance, using the Montreal Imaging Stress Task to manipulate the experience of stress. While our results largely support this hypothesis, our conclusions were undermined by data from the Rest condition, which indicated that Mental Workload and Stress were often higher than during tasks. We hypothesize that participants were experiencing anxiety in anticipation of subsequent stress tasks. We discuss this hypothesis and present a revised study designed to better control for this result