| 1. |
- Aye, Tin Nwe, 1989-, et al.
(författare)
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Prediction of tree sapwood and heartwood profiles using pipe model and branch thinning theory
- 2022
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Ingår i: Tree Physiology. - : Oxford University Press. - 0829-318X .- 1758-4469. ; 42:11, s. 2174-2185
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Tidskriftsartikel (refereegranskat)abstract
- Estimates of tree heartwood and sapwood profiles are important in the pulp industry and for dynamic vegetation models, in which they determine tree biomechanical stability and hydraulic conductivity. Several phenomenological models of stem profiles have been developed for this purpose, based on assumptions on how tree crown and foliage distributions change over time. Here, we derive estimates of tree profiles by synthesizing a simple pipe model theory of plant form with a recently developed theory of branch thinning that from simple assumptions quantifies discarded branches and leaves. This allows us to develop a new trunk model of tree profiles from breast height up to the top of the tree. We postulate that leaves that are currently on the tree are connected by sapwood pipes, while pipes that previously connected discarded leaves or branches form the heartwood. By assuming that a fixed fraction of all pipes remain on the trunk after a branching event, as the trunk is traversed from the root system to the tips, this allows us to quantify trunk heartwood and sapwood profiles. We test the trunk model performance on empirical data from five tree species across three continents. We find that the trunk model accurately describes heartwood and sapwood profiles of all tested tree species (calibration; R2: 84-99%). Furthermore, once calibrated to a tree species, the trunk model predicts heartwood and sapwood profiles of conspecific trees in similar growing environments based only on the age and height of a tree (cross-validation/prediction; R2: 68-98%). The fewer and often contrasting parameters needed for the trunk model make it a potentially useful complementary tool for biologists and foresters.
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| 2. |
- Aye, Tin Nwe, 1989-, et al.
(författare)
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Properties in Stage-Structured Population Models with Deterministic and Stochastic Resource Growth
- 2022
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Ingår i: Journal of Applied Mathematics. - : Hindawi Limited. - 1110-757X .- 1687-0042. ; 2022
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Tidskriftsartikel (refereegranskat)abstract
- Modelling population dynamics in ecological systems reveals properties that are difficult to find by empirical means, such as the probability that a population will go extinct when it is exposed to harvesting. To study these properties, we use an aquatic ecological system containing one fish species and an underlying resource as our models. In particular, we study a class of stage-structured population systems with and without starvation. In these models, we study the resilience, the recovery potential, and the probability of extinction and show how these properties are affected by different harvesting rates, both in a deterministic and stochastic setting. In the stochastic setting, we develop methods for deriving estimates of these properties. We estimate the expected outcome of emergent population properties in our models, as well as measures of dispersion. In particular, two different approaches for estimating the probability of extinction are developed. We also construct a method to determine the recovery potential of a species that is introduced in a virgin environment.
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| 3. |
- Brännström, Åke, 1975-, et al.
(författare)
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On the convergence of the Escalator Boxcar Train
- 2013
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Ingår i: SIAM Journal on Numerical Analysis. - : Society for Industrial & Applied Mathematics (SIAM). - 0036-1429 .- 1095-7170. ; 51:6, s. 3213-3231
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Tidskriftsartikel (refereegranskat)abstract
- The Escalator Boxcar Train (EBT) is a numerical method that is widely used in theoretical biology to investigate the dynamics of physiologically structured population models, i.e., models in which individuals differ by size or other physiological characteristics. The method was developed more than two decades ago, but has so far resisted attempts to give a formal proof of convergence. Using a modern framework of measure-valued solutions, we investigate the EBT method and show that the sequence of approximating solution measures generated by the EBT method converges weakly to the true solution measure under weak conditions on the growth rate, birth rate, and mortality rate. In rigorously establishing the convergence of the EBT method, our results pave the way for wider acceptance of the EBT method beyond theoretical biology and constitutes an important step towards integration with established numerical schemes.Read More: http://epubs.siam.org/doi/abs/10.1137/120893215
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| 4. |
- Carlsson, Linus, 1972-, et al.
(författare)
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A note on B-envelope of holomorphy and B-extendable domains
- 2008
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Ingår i: Complex Variables and Elliptic Equations. - Abingdon, Oxon, UK : Taylor & Francis. - 1747-6933 .- 1747-6941. ; 53:4, s. 307-309
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Tidskriftsartikel (refereegranskat)abstract
- Let B subset of H(infinity)(X) be a Banach Algebra on a Riemann domain X over C(n). We show that under certain conditions on B and X, all functions in B can be extended to functions in B(E(B, X)) where E(B, X) is the B-envelope of holomorphy.
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| 5. |
- Carlsson, Linus, 1972-
(författare)
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An equivalence to the Gleason problem
- 2010
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Ingår i: Journal of Mathematical Analysis and Applications. - : Elsevier BV. - 0022-247X .- 1096-0813. ; 370:2, s. 373-378
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Tidskriftsartikel (refereegranskat)abstract
- In this article we study the Gleason problem locally. A new method for solving the Gleason A problem is presented. This is done by showing an equivalent statement to the Gleason A problem. In order to prove this statement, necessary and a sufficient conditions for a bounded domain to have the Gleason A property are found. Also an example of a bounded but not smoothly-bounded domain in C(n) is given, which satisfies the sufficient condition at the origin, and hence has the Gleason A property there.
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| 6. |
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| 7. |
- Carlsson, Linus, 1972-
(författare)
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Nebenhülle and the Gleason problem
- 2010
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Ingår i: Proceedings of the American Mathematical Society. - : American Mathematical Society (AMS). - 0002-9939 .- 1088-6826. ; 138:1, s. 267-273
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Tidskriftsartikel (refereegranskat)
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| 8. |
- Carlsson, Linus, 1972-, et al.
(författare)
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Spectrum of certain Banach algebras and DBAR-problems
- 2007
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Ingår i: Annales Polonici Mathematici. - 0066-2216. ; 90:1, s. 51-58
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Tidskriftsartikel (refereegranskat)abstract
- We study the spectrum of certain Banach algebras of holomorphic functions defined on a domain Ω where ∂−-problems with certain estimates can be solved. We show that the projection of the spectrum onto Cn equals Ω−− and that the fibers over Ω are trivial. This is used to solve a corona problem in the special case where all but one generator are continuous up to the boundary.
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