1,350 research outputs found
Long Term Observation of the Grassland Vegetation Used Intensively or Extensively and Ecologically
The aim of the present paper was to study alterations of the grassland flora from 55 plots following a more extensive management under long term observation within 6 years. Extensification of grassland use leads to an increase of the numbers of plant species by 32%, “Red-list-species” included. The moisture number of the soils slightly increased and the reaction and nitrogen numbers decreased. Results are presented for different vegetation units
Approximation of conformal mappings using conformally equivalent triangular lattices
Consider discrete conformal maps defined on the basis of two conformally
equivalent triangle meshes, that is edge lengths are related by scale factors
associated to the vertices. Given a smooth conformal map , we show that it
can be approximated by such discrete conformal maps . In
particular, let be an infinite regular triangulation of the plane with
congruent triangles and only acute angles (i.e.\ ). We scale this
tiling by and approximate a compact subset of the domain of
with a portion of it. For small enough we prove that there exists a
conformally equivalent triangle mesh whose scale factors are given by
on the boundary. Furthermore we show that the corresponding discrete
conformal maps converge to uniformly in with error of
order .Comment: 14 pages, 3 figures; v2 typos corrected, revised introduction, some
proofs extende
Airbag-related chest wall burn as a marker of underlying injury: a case report
<p>Abstract</p> <p>Introduction</p> <p>This case of a man who sustained an airbag-induced thoracic injury and burn, highlights the potential harm that can be caused by airbags. It also serves to illustrate that a surface burn which looks small and benign can actually be a surface marker of a more serious injury. Staff working in emergency departments need to be aware of the risk of possible airbag-associated injuries.</p> <p>Case presentation</p> <p>A 65-year-old man was the driver in a frontal collision. He was wearing a seatbelt. The airbag was activated and caused a superficial chest wall burn. Initial chest x-rays were unremarkable but following deterioration in his condition, a computed tomography scan revealed a serious sternal fracture. The location of the fracture was marked on the surface by the burn.</p> <p>Conclusion</p> <p>Airbags can cause significant chest wall injuries and burns. Surface burns at the point of impact should not be dismissed as trivial as the forces involved can cause significant injury. We recommend that all people with chest wall injuries and/or burns due to airbags should have more detailed chest imaging as initial emergency radiographs can be falsely reassuring.</p
Translation-invariance of two-dimensional Gibbsian point processes
The conservation of translation as a symmetry in two-dimensional systems with
interaction is a classical subject of statistical mechanics. Here we establish
such a result for Gibbsian particle systems with two-body interaction, where
the interesting cases of singular, hard-core and discontinuous interaction are
included. We start with the special case of pure hard core repulsion in order
to show how to treat hard cores in general.Comment: 44 pages, 6 figure
Interpersonal neural synchrony when predicting others’ actions during a game of rock-paper-scissors
As members of a social species, we spend most of our time interacting with others. In interactions, we tend to mutually align our behavior and brain responses to communicate more effectively. In a semi-computerized version of the Rock-Paper-Scissors game, we investigated whether people show enhanced interpersonal neural synchronization when making explicit predictions about others’ actions. Across four experimental conditions, we measured the dynamic brain activity using the functional near-infrared spectroscopy (fNIRS) hyperscanning method. Results showed that interpersonal neural synchrony was enhanced when participants played the game together as they would do in real life in comparison to when they played the game on their own. We found no evidence of increased neural synchrony when participants made explicit predictions about others’ actions. Hence, neural synchrony may depend on mutual natural interaction rather than an explicit prediction strategy. This study is important, as it examines one of the presumed functions of neural synchronization namely facilitating predictions
Formation of Structure in Snowfields: Penitentes, Suncups, and Dirt Cones
Penitentes and suncups are structures formed as snow melts, typically high in
the mountains. When the snow is dirty, dirt cones and other structures can form
instead. Building on previous field observations and experiments, this work
presents a theory of ablation morphologies, and the role of surface dirt in
determining the structures formed. The glaciological literature indicates that
sunlight, heating from air, and dirt all play a role in the formation of
structure on an ablating snow surface. The present work formulates a
mathematical model for the formation of ablation morphologies as a function of
measurable parameters. The dependence of ablation morphologies on weather
conditions and initial dirt thickness are studied, focusing on the initial
growth of perturbations away from a flat surface. We derive a single-parameter
expression for the melting rate as a function of dirt thickness, which agrees
well with a set of measurements by Driedger. An interesting result is the
prediction of a dirt-induced travelling instability for a range of parameters.Comment: 28 pages, 13 figure
Constructing solutions to the Bj\"orling problem for isothermic surfaces by structure preserving discretization
In this article, we study an analog of the Bj\"orling problem for isothermic
surfaces (that are more general than minimal surfaces): given a real analytic
curve in , and two analytic non-vanishing orthogonal
vector fields and along , find an isothermic surface that is
tangent to and that has and as principal directions of
curvature. We prove that solutions to that problem can be obtained by
constructing a family of discrete isothermic surfaces (in the sense of Bobenko
and Pinkall) from data that is sampled along , and passing to the limit
of vanishing mesh size. The proof relies on a rephrasing of the
Gauss-Codazzi-system as analytic Cauchy problem and an in-depth-analysis of its
discretization which is induced from the geometry of discrete isothermic
surfaces. The discrete-to-continuous limit is carried out for the Christoffel
and the Darboux transformations as well.Comment: 29 pages, some figure
Content in fatty acids and carotenoids in phytoplankton blooms during the seasonal sea ice retreat in Hudson Bay complex, Canada.
The Hudson Bay complex (HBC) is home to numerous indigenous communities that traditionally have relied
heavily on its marine resources. The nutritional quality and stocks of the entire HBC food web depend in
large part on the phytoplankton production of bioactive molecules (long chain polyunsaturated fatty acids
and carotenoids) and their transfer through trophic levels. The purpose of this study was thus to
determine which molecules were produced during spring phytoplankton blooms, as well as the
environmental factors driving this production. We investigated 21 stations in 5 sub-regions of the HBC.
At the time of sampling, the sub-regions studied had different environmental settings (e.g., ice cover,
nutrients, seawater salinity and temperature) conditioning their bloom stages. Pre- and post-bloom stages
were associated with relatively low concentrations of bioactive molecules (either fatty acids or
carotenoids). In contrast, the highest concentrations of bioactive molecules (dominated by
eicosapentaenoic acid and fucoxanthin) were associated with the diatom bloom that typically occurs at
the ice edge when silicates remain available. Interestingly, the large riverine inputs in eastern Hudson Bay
led to a change in protist composition (larger contribution of Dinophyceae), resulting in lower while more
diverse content of bioactive molecules, whether fatty acids (e.g., aa-linolenic acid) or carotenoids
(e.g., peridinin). As greater stratification of the HBC is expected in the future, we suggest that
a mixotrophic/heterotrophic flagellate-based food web would become more prevalent, resulting in
a smaller supply of bioactive molecules for the food web
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