Detecting abundance trends under uncertainty: the influence of budget, observation error and environmental change

ArticleCopyright © 2014 The Authors. Animal Conservation published by John Wiley & Sons Ltd on behalf of The Zoological Society of London.Population monitoring must robustly detect trends over time in a cost-effective manner. However, several underlying ecological changes driving population trends may interact differently with observation uncertainty to produce abundance trends that are more or less detectable for a given budget and over a given time period. Errors in detecting these trends include failing to detect declines when they exist (type II), detecting them when they do not exist (type I), detecting trends in one direction when they are actually in another direction (type III) and incorrectly estimating the shape of the trend. Robust monitoring should be able to avoid each of these error types. Using monitoring of two contrasting ungulate species and multiple scenarios of population change (poaching, climate change and road development) in the Serengeti ecosystem as a case study, we used a ‘virtual ecologist’ approach to investigate monitoring effectiveness under uncertainty. We explored how the prevalence of different types of error varies depending on budgetary, observational and environmental conditions. Higher observation error and conducting surveys less frequently increased the likelihood of not detecting trends and misclassifying the shape of the trend. As monitoring period and frequency increased, observation uncertainty was more important in explaining effectiveness. Types I and III errors had low prevalence for both ungulate species. Greater investment in monitoring considerably decreased the likelihood of failing to detect significant trends (type II errors). Our results suggest that it is important to understand the effects of monitoring conditions on perceived trends before making inferences about underlying processes. The impacts of specific threats on population abundance and structure feed through into monitoring effectiveness; hence, monitoring programmes must be designed with the underlying processes to be detected in mind. Here we provide an integrated modelling framework that can produce advice on robust monitoring strategies under uncertainty.Portuguese Foundation for Science and TechnologyEuropean Commissio

Elastically restrained Bernoulli-Euler beams applied to rotary machinery modelling

Facing the lateral vibration problem of a machine rotor as a beam on elastic supports in bending, the authors deal with the free vibration of elastically restrained Bernoulli-Euler beams carrying a finite number of concentrated elements along their length. Based on Rayleigh's quotient, an iterative strategy is developed to find the approximated torsional stiffness coefficients, which allows the reconciliation between the theoretical model results and the experimental ones, obtained through impact tests. The mentioned algorithm treats the vibration of continuous beams under a determined set of boundary and continuity conditions, including different torsional stiffness coefficients and the effect of attached concentrated masses and rotational inertias, not only in the energetic terms of the Rayleigh's quotient but also on the mode shapes, considering the shape functions defined in branches. Several loading cases are examined and examples are given to illustrate the validity of the model and accuracy of the obtained natural frequencies

Time dependent transformations in deformation quantization

We study the action of time dependent canonical and coordinate transformations in phase space quantum mechanics. We extend the covariant formulation of the theory by providing a formalism that is fully invariant under both standard and time dependent coordinate transformations. This result considerably enlarges the set of possible phase space representations of quantum mechanics and makes it possible to construct a causal representation for the distributional sector of Wigner quantum mechanics.Comment: 16 pages, to appear in the J. Math. Phy

Stargenfunctions, generally parametrized systems and a causal formulation of phase space quantum mechanics

We address the deformation quantization of generally parametrized systems displaying a natural time variable. The purpose of this exercise is twofold: first, to illustrate through a pedagogical example the potential of quantum phase space methods in the context of constrained systems and particularly of generally covariant systems. Second, to show that a causal representation for quantum phase space quasidistributions can be easily achieved through general parametrization. This result is succinctly discussed.Comment: 19 pages, to appear in J. Math. Phy

Analysis of sensory effects of chitosan-based coatings applied on frozen salmon over six-months storage

The 19th Gums & Stabilisers for the Food Industry Conference: Hydrocolloid MultifunctionalityDue to an increase in fish consumption over the past years, in combination with the perishable nature of fish, the fish industry has given an added focus on the improvement of the currently used fish preservation techniques. Chitosan coatings may add improvements to the traditional water glazing, namely in physical and anti-microbial protection, allowing for shelf life extension. This work was meant to determine the influence of chitosan coatings in the organoleptic characteristics of salmon. The effects of chitosan coatings on microbiological (Total Viable Count – TVC) and chemical (Total Volatile Base Nitrogen – TVB-N) parameters were also assessed. A 15 g/L solution of chitosan was used to coat frozen salmon samples, and its effect on the sensory properties of Atlantic salmon (Salmo salar) was compared with uncoated and water glazed samples, and was studied over six months of storage at -18 °C. Samples were dipped in the chitosan solution at 8 °C during 10 s; water glazing was applied at 0.5 °C, with a dipping time of 40 s. Textural properties were evaluated through Texture Profile Analysis (TPA), while sensory properties of frozen, frozen+thawed and frozen+thawed+cooked samples were assessed by a trained panel of judges. Microbiological stability was assessed through TVC (ISO 4833-1:2013 standard), and chemical stability was determined as TVB-N (NP 2930:2009 standard). TVC analysis showed an anti-microbial effect of chitosan in the coated samples (reduction of the number of microorganisms), while TVB-N results showed to remain stable during the experiment. Textural results from the TPA analysis showed no significant differences between different coatings. Results of the trained panel indicated that for frozen samples chitosan was the preferred choice, while no significant differences existed between chitosan-coated and glazed samples in thawed and cooked samples. Flavor diffusion from the chitosan coating to the samples was assessed by Principal Component Analysis and no correlation between coating type and sample flavor could be established, meaning that no chitosan flavor was detected by the panellists.info:eu-repo/semantics/publishedVersio

Single-photon source based on FWM with adjustable linear SOP

We present a setup able to generate and detect single photons in optical fibers using the stimulated four-wave mixing (FWM) process. The results show an accurate generation of single photons at four different linear states of polarization (SOPs), with angles 0, 45, 90 and -45 degrees. The detection was performed in back-to-back configuration and after transmission over an optical fiber with a length up to 10 m