A novel role of computers in the natural products field

We describe several computer programs developed in our laboratory as aids in the determination of unknown molecular structures. These programs include CONGEN [1], for determination of all plausible structural candidates; REACT [2, 3], for simulation of sequences of chemical reactions; and STRUCC, for evaluating candidates and planning new experiments. We stress the importance of symbiosis between chemist and computer, the combination building on their respective strengths to increase the speed and accuracy of structural assignments.     

Analysis of halogenated polycyclic aromatic hydrocarbons in urban air, snow and automobile exhaust

Urban air, snow and automobile exhaust samples were extensively cleaned up by open column liquid chromatography. The appropriate fractions were analysed for halogenated polycyclic aromatic hydrocarbons (XPAH) by gas chromatography/negative chemical ionization mass spectrometry (GC/NCIMS). XPAH were found in all three sample types. A urban air sample was found to contain chlorinated pyrenes, fluoranthenes and benzopyrene and brominated pyrenes and fluoranthenes. Furthermore, the concentration of 1-chloropyrene in that air sample was estimated to be 10 pg/m³. XPAH were also found in snow samples taken in the vicinity of a motor-way. Ethylene dibromide and ethylene dichloride, are probably the source of the halogen atoms in the XPAH detected in car exhaust.     

Offspring reproductive value and nest defense in the magpie (Pica pica)

Summary Magpie (Pica pica) brood defense against a human at the nest was studied in a Mediterranean population with low renesting potential. Variations in two defense measures recorded during 106 trials at 41 different nests were positively correlated with brood age. Ineremental effects due to the number of successive visits to nests by us, brood size, and the time in the breeding season were not significant. Partial correlation analyses showed that visit rate was not an important determinant of nest defense, which thus favors an adaptive explanation of nest defense patterns. Two functional hypotheses to account for the increase in defense intensity with brood age were tested: whether (1) increased parental defense serves to compensate the higher predation risk of older nests or (2) increased parental defense reflects the increasing reproductive value of nestlings as they grow older. Daily mortality and incidende of predation (estimated from contribution of whole-brood losses to total mortality) was higher early in the nestling period, hence providing weak evidence for the assumption on which hypothesis (1) is based. The timing of parental defense intensity did not mirror variations in predation risk for the nest but variations in reproductive value of the brood, as can be estimated from daily mortality, thus supporting hypothesis (2). Magpie parents increased defense intensity in response to premature escaping by almost fully-developed nestlings. Since such a response lowers predation risk for the offspring and increases their probability of survival, this finding supports hypothesis (2), but runs contrary to hypothesis (1). Parents also increased defense in response to play-backs of alarm calls uttered by nestlings during escaping episodes. It is argued that parents should continuously monitor the degree of offspring development in order to assess their reproductive value and that, by alarm calling, chicks honestly make their parents aware of the gain in reproductive value that results from enhancement in locomotory abilities that occur at the end of the nestling period.     

Meadow management and occurrence of corncrake Crex crex

The aim of this study was to analyse the occurrence of corncrakes in two Swedish meadow sites managed by mowing and grazing, but also with abandoned meadows. Most corncrakes (58%) on meadows were found in unmanaged areas without subsidies to the farmers (i.e. areas with tall vegetation). Several corncrakes (62%) were found in restored areas, managed for less than 10 of the last 40 years, fewer (38%) in areas under continuous management. Vegetation height was negatively associated with number of years of management the last 40 years, and the continuously managed areas were avoided by corncrakes. Sites where corncrake territories occur regularly should be managed to maintain tall vegetation suitable for the species, which requires increased use of mowing. However, the results from our study also suggest that yearly mowing might result in a vegetation structure that is avoided by corncrakes. To achieve a balance between tall grassy vegetation and prevention of succession to scrub a possible management regime would therefore be mowing at intervals of a few years.     

Implementation of cleaner production in small and medium-sized enterprises

The aim of this article is to analyse whether it is possible for an external group to act as a catalyst when trying to make small and medium-sized enterprises (SMEs) adopt a cleaner production concept. At Linköping University, Sweden, nine SMEs cooperated in a cleaner production project that uses the University and the County Administration as catalysts. This article is based on a survey that evaluated the project. The survey shows that the SMEs did modify their products and processes after taking part in the project. They were especially successful in changing their products. Why products were changed to a larger extent than processes is not fully understood. Maybe this was done as a part of introducing a preventive environmental care system. Most SMEs did, as a part of introducing an environmental care system, introduce an environmental policy and an educational programme. The SMEs also experienced lower costs and better cooperation with the authorities. A reason for this is the good cooperation between the three participants of the project. In general, the SMEs did not think that they had gained marketing benefits. This attitude could have been different if more SMEs from the same value chain (supplier-producer-wholesalers-customer) had been involved.     

Diversity of chlorobiphenyl-metabolizing bacteria and their biphenyl dioxygenases in contaminated sediment

Bacteria and bacterial communities in sites contaminated with polychlorinated biphenyls have been extensively studied in the past decades. However, there are still major gaps in the knowledge of environmental processes, especially in the behavior of previously described bacteria in vitro, their real degradation abilities and the enzymes that are involved in the degradation processes.     

Varying rotation lengths in northern production forests: Implications for habitats provided by retention and production trees

Because of the limited spatial extent and comprehensiveness of protected areas, an increasing emphasis is being placed on conserving habitats which promote biodiversity within production forest. For this reason, alternative silvicultural programs need to be evaluated with respect to their implications for forest biodiversity, especially if these programs are likely to be adopted. Here we simulated the effect of varied rotation length and associated thinning regimes on habitat availability in Scots pine and Norway spruce production forests, with high and low productivity. Shorter rotation lengths reduced the contribution made by production trees (trees grown for industrial use) to the availability of key habitat features, while concurrently increasing the contribution from retention trees. The contribution of production trees to habitat features was larger for high productivity sites, than for low productivity sites. We conclude that shortened rotation lengths result in losses of the availability of habitat features that are key for biodiversity conservation and that increased retention practices may only partially compensate for this. Ensuring that conservation efforts better reflect the inherent variation in stand rotation lengths would help improve the maintenance of key forest habitats in production forests.