2,029 research outputs found
Ratcheting in Renewable Resources Contracting
No full textReal life implies that public procurement contracting of renewable resources results in repeated interaction between a principal and the agents. The present paper analyses ratchet effects in contracting of renewable resources and how the presence of a resource constraint alters the “standard” ratchet effect result. We use a linear reward scheme to influence the incentives of the agents. It is shown that for some renewable resources we might end up both with more or with less pooling in the first-period compared to a situation without a resource constraint. The reason is that the resource constraint implies a smaller performance de-pendent bonus, which reduces the first-period cost from concealing information but at the same time the resource constraint may also imply that second-period benefits from this concealment for the efficient agent are reduced. In situations with high likelihood of first-period pooling, the appropriateness of applying lin-ear incentive schemes can be questioned.Political support function, political economy, environmental regula-tion, lobbyism, rent-seeking, taxation, auction, grandfathering, emission trad-ing, European Union, interest groups, industry, consumers, environmentalists
An Enforcement-Coalition Model: Fishermen and Authorities forming Coalitions
No full textThe paper sets up a four-stage enforcement model of fish quotas. The purpose of the paper is to show how the level of enforcement set by the authorities af-fects the way fishermen form coalitions. We show that a high level of control effort yields less cooperation among fishermen, while in the case of low control effort, coalitions are somewhat self-enforcing. The paper further discusses how the optimal enforcement level changes when the coalition formation among au-thorities changes: centralised, partly centralised and decentralised authorities. We show that decentralised authorities set a lower level of control effort com-pared to the centralised authorities. The theoretical results are illustrated by simulations of the Baltic Sea cod fishery.Coalition formation, Fisheries management, Quota enforcement, Self-enforcing policy
Supplemental material for Tele-delivered mindfulness-based cognitive therapy in chronic obstructive pulmonary disease: A mixed-methods feasibility study
No full textSupplemental material for Tele-delivered mindfulness-based cognitive therapy in chronic obstructive pulmonary disease: A mixed-methods feasibility study by Ingeborg Farver-Vestergaard, Maja O’Connor, Nina C Smith, Anders Løkke, Elisabeth Bendstrup and Robert Zachariae in Journal of Telemedicine and Telecare</p
Fractures in users of antidepressants and anxiolytics and sedatives: effects of age and dose
No full textSUMMARY: Antidepressants have been associated with fractures. In a case-control study, increasing age was associated with more fractures in users of selective serotonin reuptake inhibitors and tricyclic antidepressants, whereas for anxiolytics and sedatives, more fractures were seen among the younger users. Depression per se did not seem associated with fractures.INTRODUCTION: This study aims to study the effects of age and dose of selective serotonin reuptake inhibitors (SSRI), tricyclic antidepressants (TCA) and anxiolytics/sedatives on fracture risk.METHODS: The study was designed as a case-control study. From the Danish National Health Service, we identified 124,655 fracture cases and 373,962 age- and gender-matched controls. Crude odds ratios were estimated, and propensity score adjustment was used to minimise confounding by indication.RESULTS: A higher risk of fractures was associated with an increasing dose of anxiolytics and sedatives; the highest excess risk was present in the age stratum below 40 years of age (p?<?0.01), and thereafter, the excess risk of fractures declined with age. For SSRI, a growing excess risk of fractures was seen with both increasing dose and age. Regarding TCA, no particular trend with age was present. However, an increasing risk of fractures was associated with increasing TCA dose in the age group above 60 years. Finally, for other antidepressants, no particular trend with age or dose was observed. In our data, a hospital diagnosis of depression or manic depression was associated with fewer fractures.CONCLUSION: Caution should be shown upon prescription of SSRI to older subjects. A hospital diagnosis of depression or manic depression and thus potentially a more severe disease was not a risk factor for fractures.<br/
Impact of spatially constrained sampling of temporal contact networks on the evaluation of the epidemic risk
No full textThe ability to directly record human face-to-face interactions increasingly enables the development of detailed data-driven models for the spread of directly transmitted infectious diseases at the scale of individuals. Complete coverage of the contacts occurring in a population is however generally unattainable, due for instance to limited participation rates or experimental constraints in spatial coverage. Here, we study the impact of spatially constrained sampling on our ability to estimate the epidemic risk in a population using such detailed data-driven models. The epidemic risk is quantified by the epidemic threshold of the SIRS model for the propagation of communicable diseases, i.e. the critical value of disease transmissibility above which the disease turns endemic. We verify for both synthetic and empirical data of human interactions that the use of incomplete data sets due to spatial sampling leads to the underestimation of the epidemic risk. The bias is however smaller than the one obtained by uniformly sampling the same fraction of contacts: it depends non-linearly on the fraction of contacts that are recorded, and becomes negligible if this fraction is large enough. Moreover, it depends on the interplay between the timescales of population and spreading dynamics
Recalibrating disease parameters for increasing realism in modeling epidemics in closed settings
No full textBackground: The homogeneous mixing assumption is widely adopted in epidemic modelling for its parsimony and represents the building block of more complex approaches, including very detailed agent-based models. The latter assume homogeneous mixing within schools, workplaces and households, mostly for the lack of detailed information on human contact behaviour within these settings. The recent data availability on high-resolution face-to-face interactions makes it now possible to assess the goodness of this simplified scheme in reproducing relevant aspects of the infection dynamics. Methods: We consider empirical contact networks gathered in different contexts, as well as synthetic data obtained through realistic models of contacts in structured populations. We perform stochastic spreading simulations on these contact networks and in populations of the same size under a homogeneous mixing hypothesis. We adjust the epidemiological parameters of the latter in order to fit the prevalence curve of the contact epidemic model. We quantify the agreement by comparing epidemic peak times, peak values, and epidemic sizes. Results: Good approximations of the peak times and peak values are obtained with the homogeneous mixing approach, with a median relative difference smaller than 20 % in all cases investigated. Accuracy in reproducing the peak time depends on the setting under study, while for the peak value it is independent of the setting. Recalibration is found to be linear in the epidemic parameters used in the contact data simulations, showing changes across empirical settings but robustness across groups and population sizes. Conclusions: An adequate rescaling of the epidemiological parameters can yield a good agreement between the epidemic curves obtained with a real contact network and a homogeneous mixing approach in a population of the same size. The use of such recalibrated homogeneous mixing approximations would enhance the accuracy and realism of agent-based simulations and limit the intrinsic biases of the homogeneous mixing
sj-docx-2-eso-10.1177_23969873231197530 – Supplemental material for Intravenous thrombolysis for acute ischemic stroke is associated with lower risk of post-stroke dementia: A nationwide cohort study
No full textSupplemental material, sj-docx-2-eso-10.1177_23969873231197530 for Intravenous thrombolysis for acute ischemic stroke is associated with lower risk of post-stroke dementia: A nationwide cohort study by Sigrid Breinholt Vestergaard, Christina C Dahm, Hanne Gottrup, Jan Brink Valentin, Søren Paaske Johnsen, Grethe Andersen and Janne Kærgård Mortensen in European Stroke Journal</p
sj-pdf-1-eso-10.1177_23969873231197530 – Supplemental material for Intravenous thrombolysis for acute ischemic stroke is associated with lower risk of post-stroke dementia: A nationwide cohort study
No full textSupplemental material, sj-pdf-1-eso-10.1177_23969873231197530 for Intravenous thrombolysis for acute ischemic stroke is associated with lower risk of post-stroke dementia: A nationwide cohort study by Sigrid Breinholt Vestergaard, Christina C Dahm, Hanne Gottrup, Jan Brink Valentin, Søren Paaske Johnsen, Grethe Andersen and Janne Kærgård Mortensen in European Stroke Journal</p
Testing Disk-Wind Models with Quasar CIV 1549Å Associated Absorption Lines:AGN Winds in Charleston. Proceedings of a Conference held 14-21 October, 2011 at the College of Charleston, Charleston, South Carolina, USA. Edited by G. Chartas, F. Hamann, and K.M. Leighly.
No full textNarrow associated C IV 1549Å absorption lines (NALs) with a rest equivalent width EW =3 Å detected in z ˜ 2 radio-loud and radio-quiet quasars, (a) exhibit evidence of an origin in radiatively accelerated gas, and (b) may be closely related to broad absorption line (BAL) outflows. These NALs and the few BALs detected in this quasar sample obey key predictions of models of radiatively driven disk-winds in which (1) the local disk luminosity launches the wind, (2) the central UV radiation drives it outwards, and (3) the wind acceleration (i.e., terminal velocity) depends on the strength of the X-ray to UV emission ratio, i.e., aOX. The latter means that quasars with flat aOX (like radio-louds) should not have strong, high-velocity (BAL-like) outflows. These results are of interest not only to studies of disk wind scenarios and quasar structure, but also to studies of quasar feedback: NALs that originate in powerful outflows are potential probes of quasar feedback on its environment, since NALs are more commonly occuring than BALs, irrespective of quasar radio properties (Vestergaard 2003)
Considerations in association studies in dermatoepidemiology
No full textThe ‘beauty’ of epidemiology is its ability to generate hypotheses. Observations in the clinic or in large datasets can be formally tested and can be used to create new insights or dismiss unsupported ideas. Observational research can identify new lines of inquiry that warrant fundamental or experimental research for validation. The ‘beasts’ within this type of research are spurious findings. These false findings can be scientifically robust and result from consensus on statistical significance (a study with 20 statistical comparisons is expected to have one significant finding owing to the consensus on a Pvalue of 0 05). More common reasons for spurious findings include undersized sample size, residual confounding, multiple comparisons, subgroup analyses without prespecified hypotheses or insufficient power
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