Brushes of flexible, semiflexible and rodlike diblock polyampholytes: Molecular dynamics simulation and scaling analysis

Planar brushes of flexible, semiflexible and rodlike diblock polyampholytes are studied using molecular dynamics simulations and scaling analysis in a wide range of the grafting density. Simulations show linear dependence of the average thickness on the grafting density for all the brushes regardless of their different equilibrium conformations and different flexibility of anchored chains. Slopes of fitted lines to the average thickness of the brushes of semiflexible and rodlike polyampholytes versus the grafting density are approximately the same and differ considerably from that of the brush of flexible chains. The average thickness of the brush of diblock polyampholytes is also obtained as a function of the grafting density using a simple scaling analysis which is in good agreement with the results of our simulations.Comment: 5 Figure

An Advanced Method to Assess the Diet of Free-Ranging Large Carnivores Based on Scats

<div><h3>Background</h3><p>The diet of free-ranging carnivores is an important part of their ecology. It is often determined from prey remains in scats. In many cases, scat analyses are the most efficient method but they require correction for potential biases. When the diet is expressed as proportions of consumed mass of each prey species, the consumed prey mass to excrete one scat needs to be determined and corrected for prey body mass because the proportion of digestible to indigestible matter increases with prey body mass. Prey body mass can be corrected for by conducting feeding experiments using prey of various body masses and fitting a regression between consumed prey mass to excrete one scat and prey body mass (correction factor 1). When the diet is expressed as proportions of consumed individuals of each prey species and includes prey animals not completely consumed, the actual mass of each prey consumed by the carnivore needs to be controlled for (correction factor 2). No previous study controlled for this second bias.</p> <h3>Methodology/Principal Findings</h3><p>Here we use an extended series of feeding experiments on a large carnivore, the cheetah (<em>Acinonyx jubatus</em>), to establish both correction factors. In contrast to previous studies which fitted a linear regression for correction factor 1, we fitted a biologically more meaningful exponential regression model where the consumed prey mass to excrete one scat reaches an asymptote at large prey sizes. Using our protocol, we also derive correction factor 1 and 2 for other carnivore species and apply them to published studies. We show that the new method increases the number and proportion of consumed individuals in the diet for large prey animals compared to the conventional method.</p> <h3>Conclusion/Significance</h3><p>Our results have important implications for the interpretation of scat-based studies in feeding ecology and the resolution of human-wildlife conflicts for the conservation of large carnivores.</p> </div

The Structural and Mechanical Basis for Passive‐Hydraulic Pine Cone Actuation

The opening and closing of pine cones is based on the hygroscopic behavior of the individual seed scales around the cone axis, which bend passively in response to changes in environmental humidity. Although prior studies suggest a bilayer architecture consisting of lower actuating (swellable) sclereid and upper restrictive (non‐ or lesser swellable) sclerenchymatous fiber tissue layers to be the structural basis of this behavior, the exact mechanism of how humidity changes are translated into global movement are still unclear. Here, the mechanical and hydraulic properties of each structural component of the scale are investigated to get a holistic picture of their functional interplay. Measurements of the wetting behavior, water uptake, and mechanical measurements are used to analyze the influence of hydration on the different tissues of the cone scales. Furthermore, their dimensional changes during actuation are measured by comparative micro‐computed tomography (µ‐CT) investigations of dry and wet scales, which are corroborated and extended by 3D‐digital image correlation‐based displacement and strain analyses, biomechanical testing of actuation force, and finite element simulations. Altogether, a model allowing a detailed mechanistic understanding of pine cone actuation is developed, which is a prime concept generator for the development of biomimetic hygromorphic systems

Photoinduced absorption and photoluminescence in poly(2,5-dimethoxy-p- phenylene vinylene)

We report a study of the photoexcited states in the conjugated polymer poly(2,5-dimethoxy-p-phenylene vinylene). Photoluminescence due to radiative recombination of singlet excitons is observed at energiesjust below the onset of the pi-pi* absorption band at 2.1 eV. Photoinduced absorption at 80 K shows bands peaking at 0.68, 1.35, and 1.80 eV. The features at 0.68 and 1.8 eV are associated with the same excited state which we propose is a doubly charged bipolaron, while the third at 1.35 eV is unrelated. We assign this 1.35-eV absorption to a triplet-triplet transition of a triplet exciton. The bipolarons are long lived with significant numbers surviving in excess of 100 ms at 80 K, and have a weak temperature dependence such that photoinduced absorption is readily detectable even at room temperature. The triplet exciton has a lifetime of order 2.5 ms at 80 K but this falls rapidly at higher temperature and the response is not detected at room temperature. We contrast these results with those obtained previously for the related poly(arylene vinylene) polymers poly(p-phenylene vinylene), and poly(2,5-thienylene vinylene) and for other conjugated polymers, and draw attention to the important role played in the photophysics of these materials by neutral excited states

Tick burden on European roe deer (Capreolus capreolus)

In our study we assessed the tick burden on roe deer (Capreolus capreolus L.) in relation to age, physical condition, sex, deer density and season. The main objective was to find predictive parameters for tick burden. In September 2007, May, July, and September 2008, and in May and July 2009 we collected ticks on 142 culled roe deer from nine forest departments in Southern Hesse, Germany. To correlate tick burden and deer density we estimated deer density using line transect sampling that accounts for different detectability in March 2008 and 2009, respectively. We collected more than 8,600 ticks from roe deer heads and necks, 92.6% of which were Ixodes spp., 7.4% Dermacentor spp. Among Ixodes, 3.3% were larvae, 50.5% nymphs, 34.8% females and 11.4% males, with significant seasonal deviation. Total tick infestation was high, with considerable individual variation (from 0 to 270 ticks/deer). Adult tick burden was positively correlated with roe deer body indices (body mass, age, hind foot length). Significantly more nymphs were found on deer from forest departments with high roe deer density indices, indicating a positive correlation with deer abundance. Overall, tick burden was highly variable. Seasonality and large scale spatial characteristics appeared to be the most important factors affecting tick burden on roe deer

Hantaviren und Nagetiere in Deutschland: Das Netzwerk „Nagetier-übertragene Pathogene”

ZusammenfassungHantavirus-Infektionen sind in Deutschland seit etwa 25 Jahren bekannt. Die durchschnittliche Antikörperprävalenz in der Bevölkerung liegt bei ca. 1 bis 2%. Nach Einführung der Meldepflicht im Jahr 2001 sind jährlich durchschnittlich etwa 70 bis 240 Fälle gemeldet worden. Im Jahr 2005 und insbesondere im Jahr 2007 ist jedoch ein deutlicher Anstieg der Zahl der gemeldeten Fälle registriert worden. Die am meisten betroffenen Regionen lagen in den Bundesländern Baden-Württemberg, Bayern, Nordrhein-Westfalen und Niedersachsen. Im Gegensatz zur gut dokumentierten Situation beim Menschen ist die Kenntnis der geografischen Verbreitung und Häufigkeit von Hantavirus-Infektionen in den Nagetier-Reservoiren und deren Schwankungen sehr begrenzt. Aus diesem Grund wurde in Deutschland das Netzwerk „Nagetier-übertragene Pathogene“ etabliert, das interdisziplinäre Untersuchungen zur Nagetier-Populationsdynamik, Prävalenz und Evolution von Hantaviren und anderen Nagetier-assoziierten Zoonoseerregern und den zugrunde liegenden Mechanismen sowie deren Auswirkungen auf die Häufigkeit humaner Infektionen erlaubt. Ein Monitoring von Hantaviren in Nagetieren wurde in Endemiegebieten (Baden-Württemberg, Bayern, Nordrhein-Westfalen, Niedersachsen) und Regionen mit einer geringen Zahl humaner Fälle (Mecklenburg-Vorpommern, Brandenburg, Sachsen, Sachsen-Anhalt, Thüringen, Schleswig-Holstein, Hessen, Rheinland-Pfalz) initiiert. Insgesamt wurde eine breite geographische Verbreitung des Puumalavirus (PUUV) in Rötelmäusen und des Tulavirus in Microtus-Mäusen dokumentiert. Dobrava-Belgrad-Virus-positive Apodemus-Mäuse wurden bisher ausschließlich in Brandenburg, Mecklenburg-Vorpommern und Niedersachsen gefunden. In den Hantavirus-Ausbruchsgebieten in Baden-Württemberg, Bayern, Nordrhein-Westfalen und Niedersachsen wurde bei Rötelmäusen eine hohe PUUV-Prävalenz beobachtet. Initiale Longitudinalstudien in Nordrhein-Westfalen (Stadt Köln), Bayern (Niederbayern) und Niedersachsen (ländliche Region bei Osnabrück) zeigten ein stabiles Vorkommen des PUUV in den Rötelmaus-Populationen. Neben den Untersuchungen zu Hantaviren ist auch mit Studien zum Vorkommen von anderen Nagetier-assoziierten Zoonoseerregern begonnen worden. Die begonnenen Longitudinalstudien werden Schlussfolgerungen zur Evolution von Hantaviren und anderen Nagetierassoziierten Erregern und zu Veränderungen in deren Häufigkeit und Verbreitung ermöglichen. Diese Untersuchungen werden zukünftig eine verbesserte Risikoabschätzung für die Gefährdung der Bevölkerung ermöglichen, die auch die möglichen zukünftigen Klimawandel-bedingten Veränderungen in der Epidemiologie Nagetier-assoziierter Zoonoseerreger berücksichtigt

Effect of extracellular polymeric substances on the mechanical properties of Rhodococcus

The mechanical properties of Rhodococcus RC291 were measured using force spectroscopy equipped with a bacterial cell probe. Rhodococcal cells in the late growth stage of development were found to have greater adhesion to a silicon oxide surface than those in the early growth stage. This is because there are more extracellular polymeric substances (EPS) that contain nonspecific binding sites available on the cells of late growth stage. It is found that EPS in the late exponential phase are less densely bound but consist of chains able to extend further into their local environment, while the denser EPS at the late stationary phase act more to sheath the cell. Contraction and extension of the EPS could change the density of the binding sites, and therefore affect the magnitude of the adhesion force between the EPS and the silicon oxide surface. By treating rhodococcal EPS as a surface-grafted polyelectrolyte layer and using scaling theory, the interaction between EPS and a solid substrate was modelled for the cell approaching the surface which revealed that EPS possess a large capacity to store charge. Changing the pH of the surrounding medium acts to change the conformation of EPS chains