3,584 research outputs found
Generalizing the first-difference correlated random walk for marine animal movement data
Animal telemetry data are often analysed with discrete time movement models
assuming rotation in the movement. These models are defined with equidistant
distant time steps. However, telemetry data from marine animals are observed
irregularly. To account for irregular data, a time-irregularised
first-difference correlated random walk model with drift is introduced. The
model generalizes the commonly used first-difference correlated random walk
with regular time steps by allowing irregular time steps, including a drift
term, and by allowing different autocorrelation in the two coordinates. The
model is applied to data from a ringed seal collected through the Argos
satellite system, and is compared to related movement models through
simulations. Accounting for irregular data in the movement model results in
accurate parameter estimates and reconstruction of movement paths. Measured by
distance, the introduced model can provide more accurate movement paths than
the regular time counterpart. Extracting accurate movement paths from uncertain
telemetry data is important for evaluating space use patterns for marine
animals, which in turn is crucial for management. Further, handling irregular
data directly in the movement model allows efficient simultaneous analysis of
several animals
A framework for luck egalitarianism in health and healthcare
Several attempts have been made to apply the choice-sensitive theory of distributive justice, luck egalitarianism, in the context of health and healthcare. This article presents a framework for this discussion by highlighting different normative decisions to be made in such an application, some of the objections to which luck egalitarians must provide answers and some of the practical implications associated with applying such an approach in the real world. It is argued that luck egalitarians should address distributions of health rather than healthcare, endorse an integrationist theory that combines health concerns with general distributive concerns and be pluralist in their approach. It further suggests that choice-sensitive policies need not be the result of applying luck egalitarianism in this context
Choosing the observational likelihood in state-space stock assessment models
Data used in stock assessment models result from combinations of biological,
ecological, fishery, and sampling processes. Since different types of errors
propagate through these processes it can be difficult to identify a particular
family of distributions for modelling errors on observations a priori. By
implementing several observational likelihoods, modelling both numbers- and
proportions-at-age, in an age based state-space stock assessment model, we
compare the model fit for each choice of likelihood along with the implications
for spawning stock biomass and average fishing mortality. We propose using AIC
intervals based on fitting the full observational model for comparing different
observational likelihoods. Using data from four stocks, we show that the model
fit is improved by modelling the correlation of observations within years.
However, the best choice of observational likelihood differs for different
stocks, and the choice is important for the short-term conclusions drawn from
the assessment model; in particular, the choice can influence total allowable
catch advise based on reference points.Comment: To be published in Canadian Journal of Fisheries and Aquatic Science
Report drawn up on behalf of the Committee on Social Affairs, Employment and education on the first European social budget (revised) 1970-1975. EP Working Documents, document 397/76, 8 November 1976
1969 Results of Field Experiments
Determination of rates of P and S required for maintenance of optimum pasture growth on old land, using individually grazed plots
Engineering the spatial organization of metabolic payhways:-a new approach for optimization of cell factories
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