Demography and spatial activity of fire salamanders, Salamandra salamandra (Linnaeus, 1758), in two contrasting habitats in the Vienna Woods

Understanding population dynamics is vital in amphibian conservation. To compare demography and movements, we conducted a capture-recapture study over three spring seasons in two populations of Salamandra salamandra in the Vienna Woods. The study sites differ in topography, vegetation, and the type of breeding waters. Population density in a beech forest traversed by a stream was more than twice as high as in an oak-hornbeam forest with temporary pools. Movement distances were on average higher at the latter site whereas home range estimates were similar for both sites. The sexes did not differ significantly in the observed movement patterns at either site. Annual apparent survival was mostly high (~0.85), but the estimate for females from the low-density site was lower (~0.60), indicating a higher rate of emigration or mortality

Wood fiber reinforced multicomponent, multiphase PP composites : Structure, properties, failure mechanism

Polypropylene (PP) was reinforced with wood flour and impact modified with elastomers to increase stiffness and impact resistance simultaneously. Elastomer was added in 0, 5, 10 and 20 wt%, while wood content changed from 0 to 60 wt% in 10 wt% steps. Structure and adhesion were controlled by the addition of functionalized (maleated) polymers. Composites were homogenized in a twin-screw extruder and then injection molded to tensile bars. The results showed that composite structure is determined by the relative strength of adhesion and shear forces prevailing during processing. Structure can be controlled by the application of function-al polymers within limits. Although embedding is favored by thermodynamics and further promoted by coupling, deencapsulation occurs at the large shear stresses of injection molding even in the presence of a functionalized elastomer. Composite properties depend on composition, increasing elastomer content results in decreasing stiffness and strength. Model calculations showed that the elastomer does not contribute to load bearing, average stress in the matrix increases with increasing elastomer content. Local stresses and adhesion define the initiation of deformation processes around wood particles, which start at the same stress irrespectively of elastomer content. Local processes determine the mechanism of failure and composite strength independently of their mechanism

Organic Acid Excretion in Penicillium ochrochloron Increases with Ambient pH

Despite being of high biotechnological relevance, many aspects of organic acid excretion in filamentous fungi like the influence of ambient pH are still insufficiently understood. While the excretion of an individual organic acid may peak at a certain pH value, the few available studies investigating a broader range of organic acids indicate that total organic acid excretion rises with increasing external pH. We hypothesized that this phenomenon might be a general response of filamentous fungi to increased ambient pH. If this is the case, the observation should be widely independent of the organism, growth conditions, or experimental design and might therefore be a crucial key point in understanding the function and mechanisms of organic acid excretion in filamentous fungi. In this study we explored this hypothesis using ammonium-limited chemostat cultivations (pH 2–7), and ammonium or phosphate-limited bioreactor batch cultivations (pH 5 and 7). Two strains of Penicillium ochrochloron were investigated differing in the spectrum of excreted organic acids. Confirming our hypothesis, the main result demonstrated that organic acid excretion in P. ochrochloron was enhanced at high external pH levels compared to low pH levels independent of the tested strain, nutrient limitation, and cultivation method. We discuss these findings against the background of three hypotheses explaining organic acid excretion in filamentous fungi, i.e., overflow metabolism, charge balance, and aggressive acidification hypothesis

Ecotoxicity and fungal deterioration of recycled polypropylene/wood composites: Effect of wood content and coupling

Polypropylene (PP)/wood composites were produced by homogenization in a twin-screw extruder and injection molding of tensile bars. Their mechanical properties were determined before and after exposure to biological treatment, and the effect of the treatment was assessed by various ways including visual inspection and the measurement of weight loss. The ecotoxicity of the materials was also evaluated by using the bioluminescent bacteria Vibrio fischeri. The results proved that wood facilitates biodeterioration (colonization) under the conditions used. The coupling agents do not have inhibitory effect, but seems to stimulate fungal growth (biodeterioration) at large loads of wood flour. PP/wood composites can be considered quite durable, but the influence of wood content on environmental resistance must be taken into account for materials intended for applications requiring long-term outdoor exposure as the time of exposure to microbial colonization increases. Direct ecotoxic effect on aquatic ecosystems cannot be expected from PP/wood composites

Fracture resistance of hybrid PP/elastomer/wood composites

PP was modified with elastomer and wood to prepare materials with large stiffness and impact resistance. Three wood fibers with different particle characteristics were used, and elastomer as well as wood content changed in a wide range. Interfacial adhesion was modified through the use of maelated polypropylene (MAPP) coupling agent. The structure of ternary PP/elastomer/wood composites was manipulated by the use of functionalized polymers and processing conditions. Considerable embedding of the wood into the elastomer was achieved in some cases depending on the variables. Wood increases impact resistance slightly, elastomer drastically in two-component composites and blends, but fracture toughness remains small in three-component hybrid systems irrespectively of structure. Depending on particle size and interfacial adhesion fiber fracture and debonding occur in wood reinforced composites, mainly plastic deformation takes place in blends. This latter process is suppressed by cavitation promoted further by the presence of wood fibers which increase local stresses. The usual concept of three-component materials does not work in wood composites, micromechanical deformations must be controlled to diminish or completely eliminate cavitation and to increase the plastic deformation of the matrix polymer

Water Uptake Behavior of Injection-Molded Wood–Plastic Composites

Wood–plastic composites (WPC) are partially biobased composite materials that exhibit appealing properties, but also some drawbacks. One is the inherent propensity to take up water, which influences different composite properties. In this work, we investigated the general water uptake behavior of injection-molded WPC and applied a simple model to evaluate different formulations. We found that the major influence is the wood content, but also, wood particle size showed a distinct influence on the water uptake speed, while the saturation concentration correlated with the equilibrium moisture content of the wood. The mechanical properties, such as elastic modulus and tensile strength, were reduced with increasing water uptake, and the reduction correlated with wood content and the moisture content of the wood, while the particle size did not show an influence in the investigated region

Feasibility of Cherry Pit Particles as a Natural Reinforcement in Polypropylene

Using natural materials as reinforcements for polypropylene to alter composite properties and cost is a well-known approach. Often, wood particles are used for that. These give reasonable reinforcement, but are also sought after by other industries, e.g., for energy production, and may also not be available everywhere. Therefore, the aim of this work was to investigate cherry pit particles as an alternative material for polypropylene reinforcement. Cherry pits originate as a by-product from fruit processing and have not been utilized until now as reinforcement. Cherry pit particles were produced by milling the pits, and afterwards composites were produced by compounding and injection molding. Mechanical properties and melt flow were investigated. We found some reinforcement effect, but to a lesser extent than wood particles. The cherry pit particles contain some fatty acid components, which reduce tensile properties and increase the melt flow rate of the composites. For future applications, methods for reducing these fatty acids to improve reinforcement capabilities should be investigated

Partially Compacted Commingled PLA-Flax Biocomposites

Non-woven materials feature unique properties that allow them to be used in different applications, such as the automotive sector that is increasingly seeking lightweight and sustainable materials. The aim of this work was to investigate the influence of reinforcement type and porosity on the properties of commingled, partially compacted composites based on polypropylene (PP) and polylactic acid (PLA). Furthermore, a model was applied to predict the properties of such composites, i.e., the elastic modulus, to aid materials development. It was found that high properties could be achieved using flax as reinforcement for partially compacted fleece biocomposites. Porosity is an important factor influencing these types of composites and was influenced by the compaction grade achieved as a result of stacking different numbers of layers during the consolidation of the composites. The modeling of the elastic modulus was found to be adequate for both PP-flax and PLA-flax composites for porosities under 20 vol.%