Data Availability (data + availability)

Distribution by Scientific Domains

Selected Abstracts

Model uncertainty in the ecosystem approach to fisheries

Simeon L. Hill
Abstract Fisheries scientists habitually consider uncertainty in parameter values, but often neglect uncertainty about model structure, an issue of increasing importance as ecosystem models are devised to support the move to an ecosystem approach to fisheries (EAF). This paper sets out pragmatic approaches with which to account for uncertainties in model structure and we review current ways of dealing with this issue in fisheries and other disciplines. All involve considering a set of alternative models representing different structural assumptions, but differ in how those models are used. The models can be asked to identify bounds on possible outcomes, find management actions that will perform adequately irrespective of the true model, find management actions that best achieve one or more objectives given weights assigned to each model, or formalize hypotheses for evaluation through experimentation. Data availability is likely to limit the use of approaches that involve weighting alternative models in an ecosystem setting, and the cost of experimentation is likely to limit its use. Practical implementation of an EAF should therefore be based on management approaches that acknowledge the uncertainty inherent in model predictions and are robust to it. Model results must be presented in ways that represent the risks and trade-offs associated with alternative actions and the degree of uncertainty in predictions. This presentation should not disguise the fact that, in many cases, estimates of model uncertainty may be based on subjective criteria. The problem of model uncertainty is far from unique to fisheries, and a dialogue among fisheries modellers and modellers from other scientific communities will therefore be helpful. [source]

The Neutralizer: a self-configurable failure detector for minimizing distributed storage maintenance cost

Zhi Yang
Abstract To achieve high data availability or reliability in an efficient manner, distributed storage systems must detect whether an observed node failure is permanent or transient, and if necessary, generate replicas to restore the desired level of replication. Given the unpredictability of network dynamics, however, distinguishing permanent and transient failures is extremely difficult. Though timeout-based detectors can be used to avoid mistaking transient failures as permanent failures, it is unknown how the timeout values should be selected to achieve a better tradeoff between detection latency and accuracy. In this paper, we address this fundamental tradeoff from several perspectives. First, we explore the impact of different timeout values on maintenance cost by examining the probability of their false positives and false negatives. Second, we propose a self-configurable failure detector called the Neutralizer based on the idea of counteracting false positives with false negatives. The Neutralizer could enable the system to maintain a desired replication level on average with the least amount of bandwidth. We conduct extensive simulations using real trace data from a widely deployed peer-to-peer system and synthetic traces based on PlanetLab and Microsoft PCs, showing a significant reduction in aggregate bandwidth usage after applying the Neutralizer (especially in an environment with a low average node availability). Overall, we demonstrate that the Neutralizer closely approximates the performance of a perfect ,oracle' detector in many cases. Copyright © 2008 John Wiley & Sons, Ltd. [source]

The relationship of environmental and economic performance at the firm level: a review of empirical studies in Europe and methodological comments

Marcus Wagner
This paper reviews empirical studies on the relationship between environmental and economic performance carried out with European data in order to derive conclusions with regard to their methodological comparability. Two types of research are analysed, namely (model) portfolio studies and multiple-regression-based studies. For each type two representative empirical studies are contrasted in order to establish methodological influences, as well as the importance of data availability. The review allows us to formulate a set of criteria to support improved research design in the future. These point to a strong need to develop further the methodology of studies on the relationship between environmental and economic performance. Copyright © 2002 John Wiley & Sons, Ltd. and ERP Environment [source]

An Applied Econometricians' View of Empirical Corporate Governance Studies

Axel Börsch-Supan
The economic analysis of corporate governance is in vogue. In addition to a host of theoretical papers, an increasing number of empirical studies analyze how ownership structure, capital structure, board structure, and the market for corporate control influence firm performance. This is not an easy task, and indeed, for reasons explained in this survey, empirical studies on corporate governance have more than the usual share of econometric problems. This paper is a critical survey of the recent empirical literature on corporate governance , to show which methodological lessons can be learned for future empirical research in the field of corporate governance, paying particular attention to German institutions and data availability. [source]

Predicting river width, depth and velocity at ungauged sites in England and Wales using multilevel models

D. J. Booker
Abstract Using a dataset of gauged river discharges taken from sites in England and Wales, linear multilevel models (also known as mixed effects models) were applied to quantify the variability in discharge and the discharge-hydraulic geometry relationships across three nested spatial scales. A jackknifing procedure was used to test the ability of the multilevel models to predict hydraulic geometry, and therefore width, mean depth and mean velocity, at ungauged stations. These models provide a framework for making predictions of hydraulic geometry parameters, with associated levels of uncertainty, using different levels of data availability. Results indicate that as one travels downstream along a river there is greater variability in hydraulic geometry than is the case between rivers of similar sizes. This indicates that hydraulic geometry (and therefore hydrology) is driven by catchment area, to a greater extent than by natural geomorphological variations in the streamwise direction at the mesoscale, but these geomorphological variations can still have a major impact on channel structure. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Climate variability and change in the Greater Alpine Region over the last two centuries based on multi-variable analysis

Michele Brunetti
Abstract An extensive analysis of the HISTALP database is presented with the aim of giving a comprehensive picture of secular climate variability and change in the Greater Alpine Region (GAR, 4,19 E, 43,49 N). The HISTALP database encompasses 242 sites and concerns temperature, pressure, precipitation, cloudiness, sunshine duration, vapour pressure and relative humidity. The analyses are based on four regional mean records representing different GAR low-level areas and on an additional mean record representing high-level locations. The first goal of the paper is to give an overview of the seasonal and annual records for the different variables, aiming to highlight both variability on decadal time scale and long-term evolution. Then it focuses on trend and correlation analysis. Trends are presented both for the period of common data availability for all regional average series and for moving windows that permit studying the trends over a wide range of timescales. Correlations among the different variables are presented both for the regional average series and for their high-pass-filtered versions. The analyses, beside highlighting a warming that is about twice as large as the global trend, also show that the different variables have responded in different ways to this warming and that the mutual interactions linking the different variables are often present only at specific temporal scales and only in parts of the GAR and in defined seasons. In spite of this complex behaviour, which may also be due to some residual inhomogeneities still affecting the data, the analyses give evidence that the HISTALP database has an excellent internal consistency and show that the availability of a multi-variable database turns out to be very useful in order to evaluate the reliability of the reconstruction of each variable and to better understand the behaviour and the mutual interactions of the different variables. Copyright © 2009 Royal Meteorological Society [source]

Trends in extreme daily rainfall and temperature in Southeast Asia and the South Pacific: 1961,1998

M.J. Manton
Abstract Trends in extreme daily temperature and rainfall have been analysed from 1961 to 1998 for Southeast Asia and the South Pacific. This 38-year period was chosen to optimize data availability across the region. Using high-quality data from 91 stations in 15 countries, significant increases were detected in the annual number of hot days and warm nights, with significant decreases in the annual number of cool days and cold nights. These trends in extreme temperatures showed considerable consistency across the region. Extreme rainfall trends were generally less spatially coherent than were those for extreme temperature. The number of rain days (with at least 2 mm of rain) has decreased significantly throughout Southeast Asia and the western and central South Pacific, but increased in the north of French Polynesia, in Fiji, and at some stations in Australia. The proportion of annual rainfall from extreme events has increased at a majority of stations. The frequency of extreme rainfall events has declined at most stations (but not significantly), although significant increases were detected in French Polynesia. Trends in the average intensity of the wettest rainfall events each year were generally weak and not significant. Copyright © 2001 Royal Meteorological Society [source]

The STRokE DOC trial technique: ,video clip, drip, and/or ship'

B. C. Meyer
Rationale To describe the clinical trial methods of a site-independent telemedicine system used in stroke. Aims A lack of readily available stroke expertise may partly explain the low rate of rt-PA use in acute stroke. Although telemedicine systems can reliably augment expertise available to rural settings, and may increase rt-PA use, point-to-point systems do require fixed base stations. Site-independent systems may minimize delay. The STRokE DOC trial assesses whether site-independent telemedicine effectively and efficiently brings rt-PA to a remote population. Design STRokE DOC is a 5-year, 400-participant, noninvasive trial, comparing two consultative techniques at four remote sites. Participants are randomized to acute ,STRokE DOC telemedicine' or ,telephone' consultations. Treatment decision accuracy is adjudicated at two time points, using three levels of data availability and an independent auditor. Study outcomes The primary outcome measure is whether there was a ,correct decision to treat or not to treat using rt-PA' at each of three adjudication levels (primarily at Level #2). Secondary outcomes include the number of thrombolytic recommendations, intracerebral hemorrhage, and 90-day outcomes. Using the STRokE DOC system (or telephone evaluation), medical history, neurologic scales, CT interpretations, and recommendations have been completed on over 200 participants to date. Of the initial 11, nonrandomized, ,run-in' patients, six (65%) were evaluated wirelessly, and five (45%) were evaluated with a site-independent LAN or cable modem. Three (27%) received rt-PA. The adjudication methodology was able to show both agreements and disagreements in these 11 cases. It is feasible to perform site-independent stroke consultations, and adjudicate those cases, using the STRokE DOC system and trial design. Telemedicine efficacy remains to be proven. [source]

Conundrums in mixed woody,herbaceous plant systems

Joanna I. House
Abstract Aims To identify approaches to improve our understanding of, and predictive capability for, mixed tree,grass systems. Elucidation of the interactions, dynamics and determinants, and identification of robust generalizations that can be broadly applied to tree,grass systems would benefit ecological theory, modelling and land management. Methods A series of workshops brought together scientific expertise to review theory, data availability, modelling approaches and key questions. Location Ecosystems characterized by mixtures of herbaceous and woody plant life-forms, often termed ,savannas', range from open grasslands with few woody plants, to woodlands or forests with a grass layer. These ecosystems represent a substantial portion of the terrestrial biosphere, an important wildlife habitat, and a major resource for provision of livestock, fuel wood and other products. Results Although many concepts and principles developed for grassland and forest systems are relevant to these dual life-form communities, the novel, complex, nonlinear behaviour of mixed tree,grass systems cannot be accounted for by simply studying or modelling woody and herbaceous components independently. A more robust understanding requires addressing three fundamental conundrums: (1) The ,treeness' conundrum. What controls the relative abundance of woody and herbaceous plants for a given set of conditions at given site? (2) The coexistence conundrum. How do the life-forms interact with each other? Is a given woody,herbaceous ratio dynamically stable and persistent under a particular set of conditions? (3) The net primary productivity (NPP) conundrum. How does NPP of the woody vegetation, the herbaceous vegetation, and the total ecosystem (woody + herbaceous) change with changes in the tree,grass ratio? Tests of the theory and conceptual models of determinants of mixed woody,herbaceous systems have been largely site- or region-specific and have seldom been broadly or quantitatively evaluated. Cross-site syntheses based on data and modelling are required to address the conundrums and identify emerging patterns, yet, there are very few data sets for which either biomass or NPP have been quantified for both the woody and the herbaceous components of tree,grass systems. Furthermore, there are few cross-site comparisons spanning the diverse array of woody,herbaceous mixtures. Hence, initial synthesis studies should focus on compiling and standardizing a global data base which could be (1) explored to ascertain if robust generalizations and consistent patterns exist; and (2) used to evaluate the performance of savanna simulation models over a range of woody,herbaceous mixtures. Savanna structure and productivity are the result of complex and dynamic interactions between climate, soils and disturbances, notably fire and herbivory. Such factors are difficult to isolate or experimentally manipulate in order to evaluate their impacts at spatial and temporal scales appropriate for assessing ecosystem dynamics. These factors can, however, be evaluated with simulation models. Existing savanna models vary markedly with respect to their conceptual approach, their data requirements and the extent to which they incorporate mechanistic processes. Model intercomparisons can elucidate those approaches most suitable for various research questions and management applications. Conclusion Theoretical and conceptual advances could be achieved by considering a broad continuum of grass,shrub,tree combinations using data meta-analysis techniques and modelling. [source]

Using hospital administrative data to evaluate the knowledge-to-action gap in pressure ulcer preventive care

Pieter Van Herck Msc RN
Abstract Rationale, aims and objectives, Issues of overuse, underuse and misuse are paramount and lead to avoidable morbidity and mortality. Although evidence-based practice is advocated, the widespread implementation of this kind of practice remains a challenge. This is also the case for evidence-based practice related to the prevention of pressure ulcers, which varies widely in process and outcome in Belgian hospital care. One major obstacle to bridging this knowledge-to-action gap is data availability. We propose using large-scale hospital administrative data combined with the latest evidence-based methods as part of the solution to this problem. Method, To test our proposal, we applied this approach to pressure ulcer prevention, using an administrative dataset with regard to 6030 patients in 22 Belgian hospitals as a sample of nationally available data. Methods include a systematic review approach, evidence grading, recommendations formulation, algorithm construction, programming of the rule set and application on the database. Results, We found that Belgian hospitals frequently failed to provide appropriate prevention care. Significant levels of underuse, up to 28.4% in pressure ulcer prevention education and 17.5% in the use of dynamic systems mattresses, were detected. Figures for overuse were mostly not significant. Misuse couldn't be assessed. Conclusions, These results demonstrate that this approach can indeed be successfully used to bridge the knowledge-to-action gap in medical practice, by implementing an innovative method to assess underuse and overuse in hospital care. The integrative use of administrative data and clinical applications should be replicated in other patient groups, other datasets and other countries. [source]

Evaluation of the Personal Dental Services (Wave 1) for Lambeth, Southwark and Lewisham Primary Care Trusts , Part 2: Retrospective analyses of treatment and other dental record data

Helen Best BDS MDS PhD
Abstract Aim/Objective, The purpose of the study was to undertake analyses of treatment data for the Personal Dental Services (PDS) of Lambeth, Southwark and Lewisham Primary Care Trusts and relate the analyses to the PDS goals of supporting practitioners deliver appropriate quality dental care and ensuring that appropriate quality safety net services are available for all residents. Method, Analyses of treatment data provided by the Dental Practice Board were undertaken for the post-PDS period (February 1999,March 2003, based on data availability). Analyses of the clinic notes for 1500 patients were also undertaken for the 1 year pre-PDS period (October 1997,September 1998) and post-introduction of the PDS (October 1998,June 2003). Two sets of analyses were undertaken to evaluate trends in treatment claims for the Dental Practice Board data, absolute numbers of each type of treatment claimed each month and change in numbers of types of treatments claimed over time. The clinic notes were used to undertake post-PDS, pre-PDS comparisons of the number of treatment items and grouped treatment item categories undertaken and the number of courses and percentages of private treatment items provided. The following sociodemographic characteristics of the patients were also analysed, age, gender, exemption ,status ,and ,attendance ,status. Results, Overall it was identified that the percentage reduction in the number of treatment items undertaken was 13% (95% CI ,19%, ,7%), post- as compared to the pre-PDS introduction period. On an annual basis it was identified that the percentage reduction in the number of treatment items undertaken per year per patient post-PDS was 4% (95% CI ,6%, ,2%). There were significant variations in the impact of the PDS on the number of treatment items undertaken for different types of patients. A limited number of treatment types changed significantly post- as compared to pre-PDS. The proportion of exempt patients treated did not increase ,post-PDS. Conclusions, It is possible that a less, invasive style of dental treatment was provided during the course of the PDS, however, there was only limited evidence to indicate that dentists practice style changed based on types of treatment categories provided. The PDS provided a limited safety net service for local residents. In setting program goals the nature of quality dental practice requires definition and evaluation should be undertaken on a prospective basis. [source]

Integrated estimation of measurement error with empirical process modeling,A hierarchical Bayes approach

AICHE JOURNAL, Issue 11 2009
Hongshu Chen
Abstract Advanced empirical process modeling methods such as those used for process monitoring and data reconciliation rely on information about the nature of noise in the measured variables. Because this likelihood information is often unavailable for many practical problems, approaches based on repeated measurements or process constraints have been developed for their estimation. Such approaches are limited by data availability and often lack theoretical rigor. In this article, a novel Bayesian approach is proposed to tackle this problem. Uncertainty about the error variances is incorporated in the Bayesian framework by setting noninformative priors for the noise variances. This general strategy is used to modify the Sampling-based Bayesian Latent Variable Regression (Chen et al., J Chemom., 2007) approach, to make it more robust to inaccurate information about the likelihood functions. Different noninformative priors for the noise variables are discussed and unified in this work. The benefits of this new approach are illustrated via several case studies. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Bond lengths in organic and metal-organic compounds revisited: X,H bond lengths from neutron diffraction data

Frank H. Allen
The number of structures in the Cambridge Structural Database (CSD) has increased by an order of magnitude since the preparation of two major compilations of standard bond lengths in mid-1985. It is now of interest to examine whether this huge increase in data availability has implications for the mean bond-length values published in the late 1980s. Those compilations reported mean X,H bond lengths derived from rather sparse information and for rather few chemical environments. During the intervening years, the number of neutron studies has also increased, although only by a factor of around 2.25, permitting a new analysis of X,H bond-length distributions for (a) organic X = C, N, O, B, and (b) a variety of terminal and homometallic bridging transition metal hydrides. New mean values are reported here and are compared with earlier results. These new overall means are also complemented by an analysis of X,H distances at lower temperatures (T, 140,K), which indicates the general level of librational effects in X,H systems. The study also extends the range of chemical environments for which statistically acceptable mean X,H bond lengths can be obtained, although values from individual structures are also collated to further extend the chemical range of this compilation. Updated default `neutron-normalization' distances for use in hydrogen-bond and deformation-density studies are also proposed for C,H, N,H and O,H, and the low-temperature analysis provides specific values for certain chemical environments and hybridization states of X. [source]


Pierre Pestieau
ABSTRACT,:,One is used to hearing harsh statements about inefficient public services. It is not surprising to see public sector performance questioned. What is surprising is that what is meant by performance, and how it is measured, does not seem to matter much to either the critics or the advocates of the public sector. The purpose of this paper is to suggest a definition, and a way to measure the performance of the public sector or rather of its main components. Our approach is explicitly rooted in the principles of welfare and production economics. We will proceed in four stages. First of all we present what we call the ,performance approach' to the public sector. This concept rests on the principal-agent relation that links a principal, i.e., the State, and an agent, i.e., the person in charge of the public sector unit, and on the definition of performance as the extent to which the agent fulfils the objectives assigned by the principal. The performance is then measured by using the notion of productive efficiency and the ,best practice' frontier technique. In the second stage we move to the issue of measuring the performance of some canonical components of the public sector (education, health care and railways transport), assuming that there is no constraint as to data availability. The idea is to disentangle the usual confusion between conceptual and data problems. In the third stage, we move to real world data problems. The question is then given the available data, whether it makes sense to assess and measure the performance of such public sector activities. The final stage is devoted to explaining performance or rather lack thereof. This exercise has clear implications for public policy. Finally we argue that when the scope is not components but the entirety of the public sector, one should restrict the performance analysis to outcomes and not relate them to inputs. [source]

The development of bird indicators for British fresh waters and wetlands

Mark Everard
Abstract 1.Population trends of breeding birds in freshwater habitats generated from long-term monitoring in the UK provide biodiversity indicators for some wetland habitats. 2.Bird species were assigned to target wetland habitats based on evidence of their association and data availability. Species trends for each habitat were then modelled using a range of survey data from BTO schemes including the Common Bird Census, Breeding Bird Survey, Waterways Bird Survey and Waterways Breeding Bird Survey. 3.Smoothed population trends for the selected species were combined to produce a composite indicator for birds of selected waterways and wetland habitats for England. This forms one of the three strands of a new aggregate bird indicator in the UK. 4.These indicators show generally that breeding bird species associated with slow-moving waterways and standing waters have increased over the past 30 years. Over the same period, species associated with fast-flowing waters show modest declines, species associated with reed habitats have declined and recovered, while species associated with wet grasslands, including marshes, have declined. 5.Further monitoring and exploration of the relationship between these indicators is needed to improve confidence in species trends and identifying potential drivers of change in freshwater and wetland habitats. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Living longer with a greater health burden , changes in the burden of disease and injury in the Northern Territory Indigenous population between 1994,1998 and 1999,2003

Yuejen Zhao
Abstract Objective: To measure changes over time in the burden of disease for Northern Territory (NT) Indigenous and non-Indigenous population. Methods: The numbers, and crude and age-adjusted rates of disability adjusted life years (DALY) were calculated for periods 1994,1998 and 1999,2003. A measure of information bias was developed to adjust for the tendency of years lost to disability (a component of DALY) to increase over time because of increasing data availability. The jackknife method was used for DALY uncertainty assessment. Results: The all-cause DALY rate was stable for the non-Indigenous population, but increased for the Indigenous population. For both populations, the burden of premature death decreased while the burden of disability increased. For the Indigenous population, there were substantial increases in DALY rates for type 2 diabetes, depression, nephritis/nephrosis, suicide and sense organ disorders. Conclusions: The burden of disease for Indigenous people increased over the study periods, with improvement in the burden of fatal outcomes more than offset by substantial increase in the prevalence and severity of non-fatal conditions. Implications: The paradoxical shift of living longer with a greater health burden has not been previously reported for Indigenous Australians, and highlights the critical importance of prevention for sustaining life expectancy improvement and managing escalation of health costs. This study also demonstrated the usefulness of the DALY to monitor population health. [source]

Minimum-data analysis of ecosystem service supply in semi-subsistence agricultural systems

John M. Antle
Antle and Valdivia (2006, Australian Journal of Agricultural and Resource Economics 50, 1,15) proposed a minimum-data (MD) approach to simulate ecosystem service supply curves that can be implemented using readily available secondary data and validated the approach in a case study of soil carbon sequestration in a monoculture wheat system. However, many applications of the MD approach are in developing countries where semi-subsistence systems with multiple production activities are being used and data availability is limited. This paper discusses how MD analysis can be applied to more complex production systems such as semi-subsistence systems with multiple production activities and presents validation analysis for studies of soil carbon sequestration in semi-subsistence farming systems in Kenya and Senegal. Results from these two studies confirm that ecosystem service supply curves based on the MD approach are close approximations to the curves derived from highly detailed data and models and are therefore sufficiently accurate and robust to be used to support policy decision making. [source]


Philip Arestis
E00; E22; E24 ABSTRACT The focus of this paper is to investigate the importance of the capital stock in the determination of wages and unemployment in a range of EMU countries and to compare the results across countries. A time-series analysis is conducted in the case of nine euro area countries, which were selected solely on the basis of data availability and consistency: Austria, Belgium, Finland, France, Germany, Italy, Ireland, the Netherlands and Spain. The paper begins with a short review of the literature on capital stock and unemployment, before it deals with the theoretical model. This is followed by estimation and testing of the theoretical model put forward, using both time-series and panel data. The results are supportive of the main hypothesis of the paper: capital stock is an important determinant of unemployment and wages in the countries considered for the purposes of the paper. [source]

Editorial statement concerning data availability

Dwayne Benjamin Managing Editor
No abstract is available for this article. [source]