Physics in Penguin Colonies

In polar regions, highly adapted social behavior is crucial for the survival of several species. One prominent example is the huddling behavior of Emperor penguins. To understand how Emperor penguins solve the physical problem of movement in densely packed huddles, we observed an Emperor penguin colony (Atka Bay) with time-lapse imaging and tracked the positions of more than 1400 huddling penguins. The trajectories revealed that Emperor penguins move collectively in a highly coordinated manner to ensure mobility while at the same time keeping the huddle tightly packed. Every 30 - 60 seconds, all penguins make small steps, which travel as a wave through the entire huddle. Over time, these small movements lead to large-scale reorganization of the huddle. Our data show that the dynamics of penguin huddling is governed by intermittency and approach to kinetic arrest in striking analogy with inert non-equilibrium systems. We will also present observations from a different Emperor penguin colony (Adélie Land), an Adélie penguin colony (Adélie Land), and a King penguin colony (Crozet Island)

Hydrogenated butadiene/ethene/1-olefin terpolymers as model substances for short-chain branched polyethylene

Poly[(butadiene-alt-ethene)-co-(butadiene-alt-1-olefin)] terpolymers were synthesized by Ziegler-Natta polymerization using VO(O-neopentyl)2Cl/Al(i-Bu)3 catalyst system in toluene. Variation of the 1-olefin/ethene ratio in the monomer feed produces terpolymers with mixed units of butadiene-alt-ethene and butadiene-alt-1-olefin. After hydrogenation one obtains model substances for LLDPE with a special distribution of methylene sequences between branching points. Differential scanning calorimetry (DSC) was used to determine the degree of crystallinity and the melting behavior. From the melting temperature region, the thickness distribution of the crystal lamellac, and thus the average number of C-atoms between the alkyl branches, can be determined. From detailed X-ray diffractometry, the mean crystallite size, the lattice distortions and the degree of crystallinity was determined for those products which show distinct reflections. The crystallization behavior can only be described by a three-phase model

Data from: A remote-controlled observatory for behavioural and ecological research: a case study on emperor penguins

1. Long-term photographic recordings of animal populations provide unique insights in ecological and evolutionary processes. However, image acquisition at remote locations under harsh climatic conditions is highly challenging. 2. We present a robust, energetically self-sufficient and remote-controlled observatory designed to operate year-round in the Antarctic at temperatures below -50 °C and wind speeds above 150 km/h. The observatory is equipped with multiple overview cameras and a high resolution steerable camera with a telephoto lens for capturing images with high spatial and temporal resolution. 3. Our observatory has been in operation since 2013 to investigate an emperor penguin (Aptenodytes forsteri) colony at Atka Bay near the German Neumayer III research station. Data recorded by this observatory give novel biological insights in animal life cycle and demographic trends, but also in collective and individual behaviour. As an example, we present data showing how wind speed and direction influence movements of the entire colony and of individual penguins. We also estimate daily fluctuations in the total number of individuals present at the breeding site. 4. Our results demonstrate that remote-controlled observation systems can bridge the gap between remote sensing, simple time-lapse recording setups, and on-site observations by human investigators to collect unique biological datasets of undisturbed animal populations

MEE_SPOT_Fig5_ColonyLocomotion

Meteorological data and time lapse image recordings (04/02/2013 to 04/07/2013) used to evaluate the influence of wind speed and wind direction on the position of the Atka Bay emperor penguin colon

MEE_SPOT_Fig6_SingleLocomotion

Video (4008x2672, 5 fps, 60s) recorded on 07/22/2013 at 11:40:47 UTC used to evaluate the movement characteristics of single emperor penguins at the huddle boundarie

MEE_SPOT_Fig4_Abundance

High resolution panoramic images for 04/01/2014 to 04/21/2014 used to evaluate emperor penguin numbers and arrival patter

The desmin mutation R349P increases contractility and fragility of stem cell-generated muscle micro-tissues

Aims Desminopathies comprise hereditary myopathies and cardiomyopathies caused by mutations in the intermediate filament protein desmin that lead to severe and often lethal degeneration of striated muscle tissue. Animal and single cell studies hinted that this degeneration process is associated with massive ultrastructural defects correlating with increased susceptibility of the muscle to acute mechanical stress. The underlying mechanism of mechanical susceptibility, and how muscle degeneration develops over time, however, has remained elusive. Methods Here, we investigated the effect of a desmin mutation on the formation, differentiation, and contractile function of in vitro-engineered three-dimensional micro-tissues grown from muscle stem cells (satellite cells) isolated from heterozygous R349P desmin knock-in mice. Results Micro-tissues grown from desmin-mutated cells exhibited spontaneous unsynchronised contractions, higher contractile forces in response to electrical stimulation, and faster force recovery compared with tissues grown from wild-type cells. Within 1 week of culture, the majority of R349P desmin-mutated tissues disintegrated, whereas wild-type tissues remained intact over at least three weeks. Moreover, under tetanic stimulation lasting less than 5 s, desmin-mutated tissues partially or completely ruptured, whereas wild-type tissues did not display signs of damage. Conclusions Our results demonstrate that the progressive degeneration of desmin-mutated micro-tissues is closely linked to extracellular matrix fibre breakage associated with increased contractile forces and unevenly distributed tensile stress. This suggests that the age-related degeneration of skeletal and cardiac muscle in patients suffering from desminopathies may be similarly exacerbated by mechanical damage from high-intensity muscle contractions. We conclude that micro-tissues may provide a valuable tool for studying the organization of myocytes and the pathogenic mechanisms of myopathies