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Search Results: 1 - 10 of 22 matches for " Atte Komonen "
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Negative density-distribution relationship in butterflies
Jussi P?ivinen, Alessandro Grapputo, Veijo Kaitala, Atte Komonen, Janne S Kotiaho, Kimmo Saarinen, Niklas Wahlberg
BMC Biology , 2005, DOI: 10.1186/1741-7007-3-5
Abstract: We report a strong, but counterintuitive, negative relationship between density and distribution in the butterfly fauna of Finland. With an exceptionally comprehensive data set (data includes all 95 resident species in Finland and over 1.5 million individuals), we have been able to submit several of the mechanisms to powerful direct empirical testing. Without exception, we failed to find evidence for the proposed mechanisms creating a positive density-distribution relationship. On the contrary, we found that many of the mechanisms are equally able to generate a negative relationship.We suggest that one important determinant of density-distribution relationships is the geographical location of the study: on the edge of a distribution range, suitable habitat patches are likely to be more isolated than in the core of the range. In such a situation, only the largest and best quality patches are likely to be occupied, and these by definition can support a relatively dense population leading to a negative density-distribution relationship. Finally, we conclude that generalizations about the positive density-distribution relationship should be made more cautiously.Species that are locally abundant tend to be more widespread than species that are locally rare [1,2]. This positive relationship between density and distribution of species has been observed in a variety of species assemblages over a spectrum of spatial scales, and it has been suggested that it may be almost an universal pattern in ecology [3-6]. However, a few studies document a negative relationship between density and distribution [7-14] (but see [15]). Only recently Gaston et al. [5] encouraged ecologists to pay more attention to the possibility of a negative relationship.Nine mechanisms have been proposed to explain the positive relationship between density and distribution [2,3,14,16-25]. Of these, two are artefactual (sampling artefact, phylogenetic non-independence) and seven are ecological (pattern of a
Occurrence and abundance of fungus–dwelling beetles (Ciidae) in boreal forests and clearcuts: habitat associations at two spatial scales
A. Komonen,J. Kouki
Animal Biodiversity and Conservation , 2005,
Abstract: Insect material (> 30,000 individuals) reared from the fruiting bodies of wood–decaying Trametes fungi was compared between old–growth boreal forests and adjacent clearcuts in Finland. Sulcacis affinis and Cis hispidus occurred more frequently and were, on average, more abundant in the clearcuts. Interestingly, Octotemnus glabriculus and Cis boleti had a slightly higher frequency of occurrence in the forests, despite lower resource availability. The former also showed a higher average abundance. On average, the cluster size of Trametes fruiting bodies occurring on woody debris was higher in the clearcuts than in the forests and had a positive effect on species occurrence and abundance in these clusters. The independent effect of the macrohabitat (forest or clearcut) underscores the importance of the macrohabitat where specific resources occur, and this may override the positive effects of resource availability.
Drinking to death: traditional masculinity, alcohol and shame in Finnish metal lyrics
Atte Oksanen
Nordic Studies on Alcohol and Drugs , 2011, DOI: 10.2478/v10199-011-0030-3
Abstract: AIM - This article analyzes the use of alcohol in Finnish metal music lyrics from the perspective of cultural studies. It explores how alcohol is represented in the lyrics and focuses on the theme of shame and self-destructive drinking. MATERIAL - Songs by Timo Rautiainen ja Trio Niskalaukaus (n=28), Kotiteollisuus (n=101) and Viikate (n=155) are analysed. Most attention is given to Elegia (2002, Elegy), a song by Timo Rautiainen ja Trio Niskalaukaus. METHOD - Analysis of the lyrics involves narratology, semiotics and cultural theory. RESULTS - Shame is the common factor in the lyrics and also the root of problem drinking. Alcohol is used as a way to overcome the feelings of shame. In Elegia the son's death caused by drinking brings shame over his mother. The song portrays a traditional Finnish tale of male misfortune. Such tragedies filled with shame are cultural narratives in Finnish culture. They portray alcohol and shame as the root of male problems. CONCLUSIONS - These tragedies leave little hope for the male main characters; recovery is not an option. Understanding such cultural narratives can broaden knowledge of alcohol and drug abuse.
Output error minimizing back and forth nudging method for initial state recovery
Atte Aalto
Mathematics , 2015,
Abstract: We show that for linear dynamical systems with skew-adjoint generators, the initial state estimate given by the back and forth nudging method with colocated feedback, converges to the minimizer of the discrepancy between the measured and simulated outputs - given that the observer gains are chosen suitably and the system is exactly observable. If the system's generator A is essentially skew-adjoint and dissipative (with not too much dissipation), the colocated feedback has to be corrected by the operator e^{At}e^{A*t} in order to obtain such convergence. In some special cases, a feasible approximation for this operator can be found analytically. The case with wave equation with constant dissipation will be demonstrated.
Convergence of discrete time Kalman filter estimate to continuous time estimate
Atte Aalto
Mathematics , 2014, DOI: 10.1080/00207179.2015.1090017
Abstract: This article is concerned with the convergence of the state estimate obtained from the discrete time Kalman filter to the continuous time estimate as the temporal discretization is refined. We derive convergence rate estimates for different systems, first finite dimensional and then infinite dimensional with bounded or unbounded observation operators. Finally, we derive the convergence rate in the case where the system dynamics is governed by an analytic semigroup. The proofs are based on applying the discrete time Kalman filter on a dense numerable subset of a certain time interval $[0,T]$.
Convergence of discrete-time Kalman filter estimate to continuous-time estimate for systems with unbounded observation
Atte Aalto
Mathematics , 2015,
Abstract: In this article, we complement recent results on the convergence of the state estimate obtained by applying the discrete-time Kalman filter on a time-sampled continuous-time system. As the temporal discretization is refined, the estimate converges to the continuous-time estimate given by the Kalman--Bucy filter. We shall give bounds for the convergence rates for the variance of the discrepancy between these two estimates. The contribution of this article is to generalize the convergence results to systems with unbounded observation operators under different sets of assumptions, including systems with diagonaliz-able generators, systems with admissible observation operators, and systems with analytic semigroups. The proofs are based on applying the discrete-time Kalman filter on a dense, numerable subset on the time interval [0,T] and bounding the increments obtained. These bounds are obtained by studying the regularity of the underlying semigroup and the noise-free output.
Spatial discretization error in Kalman filtering for discrete-time infinite dimensional systems
Atte Aalto
Mathematics , 2014,
Abstract: We derive a reduced-order state estimator for discrete-time infinite dimensional linear systems with finite dimensional Gaussian input and output noise. This state estimator is the optimal one-step estimate that takes values in a fixed finite dimensional subspace of the system's state space --- consider, for example, a Finite Element space. We then derive a Riccati difference equation for the error covariance and use sensitivity analysis to obtain a bound for the error of the state estimate due to the state space discretization.
New performance guarantees for the greedy maximization of submodular set functions
Jussi Laitila,Atte Moilanen
Mathematics , 2015,
Abstract: We present new tight performance guarantees for the greedy maximization of nondecreasing submodular set functions. Our main result first provides a performance guarantee in terms of the overlap of the optimal and greedy solutions. As a consequence we improve performance guarantees of Nemhauser, Wolsey and Fisher (1978) and Conforti and Cornu\'ejols (1984) for maximization over subsets, which are at least half the size of the problem domain. As a further application, we obtain a new tight performance guarantee in terms of the cardinality of the problem domain.
Where and how to manage: Optimal selection of conservation actions for multiple species.
Astrid van Teeffelen,Atte Moilanen
Biodiversity Informatics , 2008,
Abstract: Multiple alternative options are frequently available for the protection, maintenance or restoration of conservation areas. The choice of a particular management action can have large effects on the species occurring in the area, because different actions have different effects on different species. Together with the fact that conservation funds are limited and particular management actions are costly, it would be desirable to be able to identify where, and what kind of management should be applied to maximize conservation benefits. Currently available site-selection algorithms can identify the optimal set of sites for a reserve network. However, these algorithms have not been designed to answer what kind of action would be most beneficial at these sites when multiple alternative actions are available. We describe an algorithm capable of solving multi-species planning problems with multiple management options per site. The algorithm is based on benefit functions, which translate the effect of a management action on species representation levels into a value, in order to identify the most beneficial option. We test the performance of this algorithm with simulated data for different types of benefit functions and show that the algorithm’s solutions are optimal, or very near globally optimal, partially depending on the type of benefit function used. The good performance of the proposed algorithm suggests that it could be profitably used for large multi-action multi-species conservation planning problems.
Diatom and crustacean zooplankton communities, their seasonal variability and representation in the sediments of subarctic Lake Saanaj rvi
Milla RAUTIO,Sanna SORVARI,Atte KORHOLA
Journal of Limnology , 2000, DOI: 10.4081/jlimnol.2000.s1.81
Abstract: Present and past diatom and crustacean zooplankton communities of subarctic Lake Saanaj rvi in Finnish Lapland were studied with special emphasis on their representation in the sediment surface. Two years monitoring of the present state of the lake revealed it to be ultraoligotrophic with a biomass peak during autumn overturn. Chrysophytes and diatoms were the most abundant phytoplankton groups, with four species forming the main bulk of the crustacean zooplankton community. The comparison of the present plankton community with the species composition in the sediment surface showed that only some plankton groups are suitable for paleolimnological studies. The value of diatoms for paleolimnological studies was supported by the observation that all of the species recorded from various habitats in the lake were detectable in the sediment. In addition, some species (e.g. Cyclotella glomerata) that limnological sampling had not detected were found in the sediment record. Similarly, the zooplankton class Chydoridae and Daphnia hyalina species were equally or better represented in the sediment than in the water column. On the other hand, the sediment trap and core evidence of the whole crustacean zooplankton community suggested many zooplankton species have little or no significance in paleolimnological studies. For example the two dominant copepod species, Eudiaptomus graciloides and Cyclops abyssorum, were not detectable in sediment trap samples. These findings indicate that only a small fraction of the living biota are preserved in the sediments, and this should be taken into account when drawing conclusions based on the detection of just one such species group.
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