A continuous mechanobiological model of lateral inhomogeneous biological surfaces

Thin elastic surfaces containing molecules infuencing the mechanical prop- erties of the surface itself are wide spreaded structures of different scales in biological systems. Prominent examples are bilayer membranes and cell tis- sues. In this paper we present a continuous dynamical model of deforming lateral inhomogeneous surfaces, using the example of biological membranes. In agreement with experimental observations the membrane consists of dif- ferent molecule species undergoing lateral phase separation and influencing the mechanical properties of the membrane. The presented model is based on the minimization of a free energy leading to a coupled nonlinear PDE system of fourth order, related to the Willmore flow and the Cahn-Hilliard equation. First simulations show the development of budding structures from stochas- tic initial conditions as a result of the gradient flow, which is comparable to experimentally observed structures. In our model mechanical properties are described via macroscopic mechanical moduli. However, the qualitative and quantitative relationships of mechanical moduli and the local composi- tion of the membrane are unkown. Since the exact relationship significantly influences the emerging structures, this study motivates the development of techniques allowing for upscaling from the molecular scale

Effiziente Wärmesysteme für Wohngebäude

Die Entwicklung effizienter Wärmesysteme für Wohngebäude ist eine zentrale Aufgabe der Energieforschung. Der Wohngebäudesektor hat seit Jahren einen – witterungsbedingt leicht schwankenden – Anteil von 25 – 30 % am Endenergieverbrauch in Deutschland. Dabei werden über 80 % der im Sektor Haushalte verbrauchten Energie zur Bereitstellung von Wärme verwendet, im Jahr 2013 z. B. 585 TWh oder mehr als ein Fünftel des gesamtdeutschen Endenergieverbrauchs. Da die Wärmeversorgung hauptsächlich noch über die fossilen Energieträger Erdgas und Heizöl betrieben wird, bieten Wärmesysteme für Wohngebäude ein erhebliches Potenzial für CO2-Einsparungen. Die Energiewende im Heizungskeller beruht dabei – genau wie in anderen Sektoren auch – auf den beiden Säulen erneuerbare Energieversorgung und Effizienz. Durch verschärfte Regelungen für Neubauten und energetische Sanierungen von Bestandsimmobilien wurde in den vergangenen Jahren ein leichter Rückgang des durchschnittlichen flächenspezifischen Heizenergiebedarfs in Wohngebäuden erreicht. Diesem Trend stand jedoch ein steigender Wohnflächenverbrauch pro Person entgegen, so dass der gesamte Heizenergieverbrauch langsamer sinkt als der spezifische Heizenergiebedarf in den Gebäuden. Die jährliche Totalsanierungsquote im Wohnbereich liegt zudem weit unterhalb der als für die Erreichung der Effizienzziele 2050 nötigen postulierten 2,7 %. Ein verstärkter Ausbau des Einsatzes erneuerbarer Energien im Heizungskeller bietet einen zusätzlichen Freiheitsgrad, der zur Erreichung der angestrebten CO2-Minderung beitragen kann

W262 Converting between Doyle and International 1/4 Board Foot Rules

Renewable Resources Notes Version 5.

W261 When a Tornado Strikes: Steps to Claim a Timber Casualty Loss

Renewable Resources notes Version 3.

SP595 Timber Theft! How to Avoid It and What to Do If It Happens

Renewable Resources Notes Version 2.

Forest Certification and Nonindustrial Private Forest Landowners: Who Will Consider Certifying and Why?

Nonindustrial private forest owners in western Tennessee who own 40 or more acres of forestland were sent a mail survey to assess their awareness, acceptance, and perception of forest certification. More than eight in 10 participants indicated a willingness to consider certification. Landowners who would most likely consider certifying their forest were typically well-educated new forest owners, and had received advice or information about their forestland. They would certify for both utilitarian and environmental reasons, and they most trust the State Division of Forestry and consulting foresters as potential third-party certifiers

Models, Numerics and Simulations of Deforming Biological Surfaces

Thin, elastic surfaces are a fundamental building block in each biological system. Their main representative on the small scale are biomembranes; an important example on the larger scale are cell tissues. In both cases, the surfaces define a mechanical and chemical border, indispensable for the genesis and maintenance of each organism. An essential property of the surfaces is a lateral inhomogeneous composition of the surfaces themselves: without these inhomogeneities, the complexity of shapes, mechanochemical properties and dynamics would not be possible. In this thesis, we develop continuous mechanobiological models of membranes and tissues. Since these surfaces are experimentally often difficult to access, our approaches allow to investigate their behavior theoretically. The developed mathematical models are coupled nonlinear systems of partial differential equations (PDE) of fourth order. To enable simulations of these models, we significantly extend numerical algorithms for surface deformation based on the finite-element method (FEM). Extensive systematic simulations of the different models - in close comparison to recent experimental and theoretical studies on different scales - lead to new findings in membrane as well as tissue research. The key findings are the prediction and characterization of new mechanisms of communication between the two monolayers of a biomembrane, the investigation of the elusive role of the Gaussian rigidity in different fundamental membrane processes (like budding and lateral sorting), and moreover, the postulation and investigation of a new model for pattern formation in biological tissues, leading to experimental evidences for a new key mechanism for symmetry break in Hydra polyps

Migrating curlews on schedule: departure and arrival patterns of a long-distance migrant depend on time and breeding location rather than on wind conditions

Background However, few studies have tried to validate the significance of these three concepts simultaneously, and long-term, high-resolution tagging datasets recording individual movements across consecutive years are scarce. We used such a dataset to explore intraspecific and intra-individual variabilities in departure and arrival decisions from/to wintering grounds in relation to these three different concepts in bird migration.We equipped 23 curlews (Numenius arquata) wintering in the Wadden Sea with Global Positioning System data loggers to record their spatio-temporal patterns of departure from and arrival at their wintering site, and the first part of their spring migration. We obtained data for 42 migrations over 6 years, with 12 individuals performing repeat migrations in consecutive years. Day of year of departure and arrival was related to 38 meteorological and bird-related predictors using the least absolute shrinkage and selection operator (LASSO) to identify drivers of departure and arrival decisions.Curlews migrated almost exclusively to Arctic and sub-Arctic Russia for breeding. Curlews breeding further away in areas with late snowmelt departed later. Departures dates varied by only < 4 days in individual curlews tagged over consecutive years.These results suggest that the trigger for migration in this long-distance migrant is largely independent of weather conditions but is subject to resource availability in breeding areas. The high intra-individual repeatability of departure days among subsequent years and the lack of relationship to weather parameters suggest the importance of genetic triggers in prompting the start of migration. Further insights into the timing of migration in immatures and closely related birds might help to further unravel the genetic mechanisms triggering migration patterns

Evolving surface finite element method for the Cahn-Hilliard equation

We use the evolving surface finite element method to solve a Cahn- Hilliard equation on an evolving surface with prescribed velocity. We start by deriving the equation using a conservation law and appropriate transport for- mulae and provide the necessary functional analytic setting. The finite element method relies on evolving an initial triangulation by moving the nodes according to the prescribed velocity. We go on to show a rigorous well-posedness result for the continuous equations by showing convergence, along a subse- quence, of the finite element scheme. We conclude the paper by deriving error estimates and present various numerical examples