Search results for "observation"

Analysis of the spawning stock-recruitment relationship of vendace (Coregonus albula (L.)) with evaluation of alternative models, additional variable…

2004

–  Spawning biomass and recruitment data for vendace from a central Finnish lake were analysed by fitting various recruitment models and comparing the fits statistically. The compensatory models of Ricker, Cushing and Beverton & Holt fitted the data better than the H0 hypothesis of constant proportionality, but model and parameter uncertainties were high. Additional variables were included in an attempt to reduce uncertainties. Heavy wind forcing during the first month after hatching of larvae reduced the recruitment success. For the Ricker and the Cushing models, recruitment seemed to be also negatively associated with the density of the previous year-class. The r2 increased considerably w…

Error calculation for the PSA quotient.

2008

Abstract Objective Prostate specific antigen (PSA) assays have significant measurement errors, but the error associated with the PSA quotient (free to total PSA) often remains unknown. Methods We used both Gaussian error calculation and measurement of imprecision to investigate the level of error associated with the PSA quotient. Results Surprisingly, we found that the error of the PSA quotient at low levels is markedly smaller than that of the total PSA value. Conclusions The PSA quotient should be calculated and considered as a clinically relevant value.

Selection Correction in Panel Data Models: An Application to Labour Supply and Wages

2000

In recent years a number of panel estimators have been suggested for sample selection models, where both the selection equation and the equation of interest contain individual effects which are correlated with the explanatory variables. We review and compare some of these estimators, and apply them to estimating the return to actual labour market experience for females, using a panel of twelve years. All these estimators rely on the assumption of strict exogeneity of regressors in the equation of interest, conditional on individual specific effects and the selection mechanism. This assumption is likely to be violated in many applications. Also, life history variables are often measured with…

SM identification of approximating models forH∞ robust control

1999

Set Membership (SM) W, identification of mixed parametric and nonparametric models is investigated, aimed to estimate a low order approximating model and an identification error, giving a measure of the unmodeled dynamics in a form well suited for H, control methodologies. In particular, the problem of estimating the parameters of the parametric part and the H, bound on the modeling error is solved using frequency domain data, supposing lbo bounded measurement errors and exponentially stable unmodeled dynamics. The effectiveness of the proposed procedure is tested on some numerical examples, showing the advantages of the proposed methods over the existing nonparametric H, identification app…

Estimation of errors in mechanical efficiency

1990

Errors in measurements of mechanical work, net energy expenditure and mechanical efficiency (ME) were calculated, when subjects performed isolated eccentric or concentric muscle actions and combinations of these actions [stretch-shortening cycle (SSC) exercises] with a special sledge apparatus. The relative error of mechanical work was 6.1%. When estimating the error of energy metabolism from oxygen consumption the error would be about 4% (McArdle et al. 1981). The maximum error of ME was the sum of these two values (10.1%). Obviously the error of ME was less than 5%, because 30 muscle actions were averaged and, in addition, the errors of mechanical work and energy expenditure were not in t…

2020

This study examined the stability of reading difficulties (RD) from grades 2 to 6 and focused on the effects of measurement error and cut-off selection in the identification of RD and its stability with the use of simulations. It addressed methodological limitations of prior studies by (a) applying a model-based simulation analysis to examine the effects of measurement error and cut-offs in the identification of RD, (b) analyzing a non-English and larger sample, and (c) examining RD in both reading fluency and reading comprehension. Reading fluency and reading comprehension of 1,432 Finnish-speaking children were assessed in grades 2 and 6. In addition to the use of single cut-off points on…

Seawater carbonate chemistry and nest guarding behaviour of a temperate wrasse

2021

Organisms may respond to changing environmental conditions by adjusting their behaviour (i.e., behavioural plasticity). Ocean acidification (OA), resulting from anthropogenic emissions of carbon dioxide (CO2), is predicted to impair sensory function and behaviour of fish. However, reproductive behaviours, and parental care in particular, and their role in mediating responses to OA are presently overlooked. Here, we assessed whether the nesting male ocellated wrasse Symphodus ocellatus from sites with different CO2 concentrations showed different behaviours during their breeding season. We also investigated potential re-allocation of the time-budget towards different behavioural activities b…

Seawater carbonate chemistry and shell mineralogy, microstructure, and mechanical strength of four Mediterranean gastropod species near a CO2 seep

2017

Marine CO2 seeps allow the study of the long-term effects of elevated pCO2 (ocean acidification) on marine invertebrate biomineralization. We investigated the effects of ocean acidification on shell composition and structure in four ecologically important species of Mediterranean gastropods (two limpets, a top-shell snail, and a whelk). Individuals were sampled from three sites near a volcanic CO2 seep off Vulcano Island, Italy. The three sites represented ambient (8.15 pH), moderate (8.03 pH) and low (7.73 pH) seawater mean pH. Shell mineralogy, microstructure, and mechanical strength were examined in all four species. We found that the calcite/aragonite ratio could vary and increased sign…

Physiological advantages of dwarfing in surviving extinctions in high-CO2 oceans

2015

Excessive CO2 in the present-day ocean-atmosphere system is causing ocean acidification, and is likely to cause a severe biodiversity decline in the future, mirroring effects in many past mass extinctions. Fossil records demonstrate that organisms surviving such events were often smaller than those before, a phenomenon called the Lilliput effect. Here, we show that two gastropod species adapted to acidified seawater at shallow-water CO2 seeps were smaller than those found in normal pH conditions and had higher mass-specific energy consumption but significantly lower whole-animal metabolic energy demand. These physiological changes allowed the animals to maintain calcification and to partial…

The impact of ocean acidification and warming on the skeletal mechanical properties of the sea urchin Paracentrotus lividus from laboratory and field…

2016

Increased atmospheric CO2 concentration is leading to changes in the carbonate chemistry and the temperature of the ocean. The impact of these processes on marine organisms will depend on their ability to cope with those changes, particularly the maintenance of calcium carbonate structures. Both a laboratory experiment (long-term exposure to decreased pH and increased temperature) and collections of individuals from natural environments characterized by low pH levels (individuals from intertidal pools and around a CO2 seep) were here coupled to comprehensively study the impact of near-future conditions of pH and temperature on the mechanical properties of the skeleton of the euechinoid sea …