Modelling dynamics of managed tropical rainforests—An aggregated approach

The overuse of rainforests in the last century and its consequences necessitate a rethinking of logging policies. To this end models have been developed to simulate rainforest dynamics and to allow optional management strategies to be evaluated. Parameterisation of presently existing models for a certain site needs a lot of work, thus the parameterisation effort is too high to apply the models to a wide range of rainforests. Hence, in this paper we introduce the simplified model FORREG using the knowledge we have gained from a more complex model, FORMIX3-Q.     

Preliminary Measurements of Turbulence and Environmental Parameters in a Sub-Tropical Estuary of Eastern Australia

In natural systems, mixing is driven by turbulence, but current knowledge is limited in estuarine zones where predictions of contaminant dispersion are often inaccurate. A series of detailed field studies was conducted in a small sub-tropical creek in eastern Australia. Hydrodynamic, physio-chemical and ecological measurements were conducted simultaneously to assess the complexity of the estuarine zone, notably the interactions between turbulence and environment. The measurements were typically performed at high frequency over a tidal cycle. The results provide an original data set to complement long-term monitoring and a basis for a more detailed study of mixing in sub-tropical systems. Unlike many long-term observations, velocity and water quality scalars were measured herein with sufficient spatial and temporal resolutions to determine quantities of interest in the study of turbulence, while ecological indicators were sampled systematically and simultaneously. In particular the results yielded contrasted outcomes, and the finding impacts on the selection process for key water quality indicators.     

The poison gland of the antMyrmicaria eumenoides and its role in recruitment communication

Summary The antMyrmicaria eumenoides is a significant arthropod predator. For rapid attraction of large numbers of nestmates to newly discovered food sources the ants use an efficient recruitment communication system based on the poison gland secretion. Workers exhibit age-based division of labour. Young workers perform brood-care; their poison gland reservoir develops and reaches its final size of 0.5 µl at an age of 6 weeks, when they become foragers. The secretion deposited during combat with enemies or prey is composed of equal amounts of both a high volatile and a low volatile fraction. Within the high volatile fraction (+)—limonene is the main component (97%) and is the only olfactory trigger to alert ants in the vicinity and to recruit them to places of combat, where they assemble. Ants respond to synthetic (+)—limonene in exactly the same way as to the poison gland secretion when applied at the same airborne concentrations. Further components of the high volatile fraction are four additional monoterpene hydrocarbons and hexanoic nitrile. The high volatile and the low volatile fraction of the poison gland secretion each have dual functions: The low volatiles, of which the main component is an alkaloid, serve as a fixative and extend the effective period of the limonene signal by modifying its evaporation kinetics. On the other hand the high volatile recruitment signal (+)—limonene is also the solvent for the alkaloid and enhances its spreading on the surface of the cuticle of arthropod enemies or prey.     

Nebenprodukte der Lebensmittelverarbeitung als Futtermittel

The use of byproducts of the food industry as feedstuffs for animals has become a significant conflict for agriculture. Public regulations concerning the improvement of nutrient recycling and economic production with less financial support, on one hand, and the avoidance of all risks for human and animal health, on the other hand, are seen to affect agriculture practice. In this paper, information is presented about the quantities and quality of byproducts of the food industry used as feedstuffs. Also the nutritional and economical value of meat meal is discussed including ecological aspects. Other use or the disposal of products high in their nutritional value should, in the future, be no alternatives to the use as feed for animals, when risks are carefully controlled, because of the necessity for a sustainable agriculture and economy.     

Dynamics of Turbulence in Low-Speed Oscillating Bottom-Boundary Layers of Stratified Basins

This paper focuses on the impact of an oscillating low-speed current on the structure and dynamics of the bottom-boundary layer (BBL) in a small stratified basin. A set of high-resolution current profile measurements in combination with temperature-microstructure measurements were collected during a complete cycle of the internal oscillation (`seiching') in the BBL of Lake Alpnach, Switzerland. It was found that even a relatively long seiching period of 24 hours significantly changed the form of the near-bottom current profiles as well as the dynamics of the turbulent dissipation rate compared to the steady-state law-of-the-wall. A logarithmic fit to the measured current profiles starting at a distance of 0.5 m above the sediment led to inconsistent estimates of both friction velocity and roughness length. Moreover, a phase lag between the current and the turbulent dissipation of 1.5 hours and a persistent maximum in the current profile at a height of 2.5 to 3 m above the sediment were observed. The experimental findings were compared to the results of a k- turbulence model and showed good agreement in general. Specifically, the inconsistent logarithmic fitting results and the observed phase lag were reproduced well by the model.     

Chemical structure and biological activities of lipid A's from various bacterial families

The endotoxic principle of lipopolysaccharides (LPS) is localized in their lipid A component. Biological effects of LPS on, for instance, body temperature, blood pressure, and blood picture, are also induced by free lipid A. In contrast to the great variability of the 0-specific chains, the chemical structure of lipid A is much more constant. It is common for Salmonella and similar for other genera of the Enterobacteriaceae. Recently, a number of lipid A's have been recognized that exhibited distinct structural features compared with Enterobacteriaceae. These lipid A's were found to be also distinct with regard to some of their biological properties.