Influence of seaward boundary condition on contaminant transport in unconfined coastal aquifers.

Contaminant transport in coastal aquifers is complicated partly due to the conditions at the seaward boundary including seawater intrusion and tidal variations of sea level. Their inclusion in modelling this system will be computationally expensive. Therefore, it will be instructive to investigate the consequence of simplifying the seaward boundary condition by neglecting the seawater density and tidal variations in numerical predictions of contaminant transport in this zone. This paper presents a comparison of numerical predictions for a simplified seaward boundary condition with experimental results for a corresponding realistic one including a saltwater interface and tidal variations. Different densities for contaminants are considered. The comparison suggests that the neglect of the seawater intrusion and tidal variations does not affect noticeably the overall migration rate of the plume before it reaches the saltwater interface. However, numerical prediction shows that a more dense contaminant travels further seaward and part of the solute mass exits under the sea if the seawater density is not included. This is not consistent with the experimental result, which shows that the contaminant travels upwards to the shoreline along the saltwater interface. Neglect of seawater density, therefore, will result in an underestimation of the exit rate of solute mass around the coastline and fictitious migration paths under the seabed. For a less dense contaminant, neglect of seawater density has little effect on numerical prediction of migration paths.     

Error orientation questionnaire (EOQ): reliability,validity, and different language equivalence

An Error Orientation Questionnaire (EOQ) was developed, consisting of eight scales on attitudes to and on coping with errors at work. In Study I (representative sample of a German city, N=478) six scales were developed with the help of a confirmatory factor analysis using LISREL techniques. They comprise error competence, learning from errors, error risk taking, error strain, error anticipation, covering up errors. All constructs were validated. In a second study, items were added to the scales and two additional scales, ‘error communication’ and ‘thinking about errors’, were included. The scales were translated into English and Dutch and 160 students in the Netherlands filled out both language versions (Study II). The 8‐factor solutions in English and Dutch were replicated. The issue of language equivalence of these two language versions were taken up (equivalence across correlations exists). Potentially biasing variables did not influence the solutions. Practical uses of the EOQ are pointed out. Copyright © 1999 John Wiley & Sons, Ltd.     

Integrated and adaptive water resources management: exploring public participation in the UK

Regional Environmental Change - Contemporary water management practices worldwide are informed by two leading paradigms: integrated water resources management and adaptive management. While...     

Ants use directionless odour cues to recall odour-associated locations

Ants are key model organisms in the study of navigation and memory formation. Many ants learn food locations very quickly and with high accuracy. But can individual ants learn multiple separate food locations, associate them with a cue, and then correctly recall the food location and navigate towards it when later presented with that cue? In this experiment, we sequentially trained Lasius niger foragers to two scented feeders at either end of a T-maze. The next day, an odour cue corresponding to one of the food sources was presented to the ants in the air, on the substrate and via trophallaxis with nest mates. Trained foragers accurately navigated to the correct side of the T-maze (89 % correct decisions), but only after the first 10 min of testing. This demonstrates the ability of ants to perform associative recall, forming clear associates between odour cues and food locations and using these associations to navigate to food sources. We also found that trained ants in the first 10 min of testing showed no preference for the correct side (57 % correct decisions), which may be related to the motivational state of the ants tested. Ants with different motivational states (whether they are ‘scouting’ or ‘recruited’) made use of route memories in a completely different manner. This highlights the importance of taking account of motivational states when performing behavioural experiments.     

Digitale Bildanalyse als optische Meßtechnik in der Biochemie

Digital image analysis can be used to assist or complement visual perception. In quantifying light intensities it is superior to the human visual system and therefore is an appropriate and useful tool for research. Using microphotometry as an example the physical bases of digital image analysis are explained and the applications of this measuring technique to biochemical analysis are demonstrated.     

Post-socialist forest disturbance in the Carpathian border region of Poland, Slovakia, and Ukraine.

Forests provide important ecosystem services, and protected areas around the world are intended to reduce human disturbance on forests. The question is how forest cover is changing in different parts of the world, why some areas are more frequently disturbed, and if protected areas are effective in limiting anthropogenic forest disturbance. The Carpathians are Eastern Europe's largest contiguous forest ecosystem and are a hotspot of biodiversity. Eastern Europe has undergone dramatic changes in political and socioeconomic structures since 1990, when socialistic state economies transitioned toward market economies. However, the effects of the political and economic transition on Carpathian forests remain largely unknown. Our goals were to compare post-socialist forest disturbance and to assess the effectiveness of protected areas in the border triangle of Poland, Slovakia, and Ukraine, to better understand the role of broadscale political and socioeconomic factors. Forest disturbances were assessed using the forest disturbance index derived from Landsat MSS/TM/ETM+ images from 1978 to 2000. Our results showed increased harvesting in all three countries (up to 1.8 times) in 1988-1994, right after the system change. Forest disturbance rates differed markedly among countries (disturbance rates in Ukraine were 4.5 times higher than in Poland, and those in Slovakia were 4.3 times higher than in Poland), and in Ukraine, harvests tended to occur at higher elevations. Forest fragmentation increased in all three countries but experienced a stronger increase in Slovakia and Ukraine (approximately 5% decrease in core forest) than in Poland. Protected areas were most effective in Poland and in Slovakia, where harvesting rates dropped markedly (by nearly an order of magnitude in Slovakia) after protected areas were designated. In Ukraine, harvesting rates inside and outside protected areas did not differ appreciably, and harvests were widespread immediately before the designation of protected areas. In summary, the socioeconomic changes in Eastern Europe that occurred since 1990 had strong effects on forest disturbance. Differences in disturbance rates among countries appear to be most closely related to broadscale socioeconomic conditions, forest management practices, forest policies, and the strength of institutions. We suggest that such factors may be equally important in other regions of the world.     

Umbilical cord haematoma as a complication of intrauterine intravascular blood transfusion

Between October 1985 and February 1989, 49 ultrasound-guided intravascular fetal blood transfusions were performed in 16 patients (14 with rhesus (Rh) isoimmunization, 2 with non-immunologic hydrops fetalis (NIHF)). As an intra-operative complication, perivascular haematoma of the cord occurred in three patients (7 per cent). In two cases, fetal bradycardia necessitated delivery by Caesarean section at 30 and 32 weeks' gestation, respectively. In the third case, fetal bradycardia developed during transfusion, at 31 weeks' gestation, but normalized within 3 min. The baby was delivered as planned at 36 weeks of gestation, after another transfusion at 34 weeks. Dislodgement of the needle tip into perivascular tissue, caused by sudden fetal or maternal movements, is the reason for this complication. The haematoma develops as a result of delayed recognition and continuous transfusion into Wharton' s jelly. Cord haematoma may be diagnosed in time by continuous ultrasound imaging, as illustrated in case 3. To minimize the risk of needle dislodgement during transfusion, sedation of the mother and complete immobilization of the fetus by injecting a short-acting muscle relaxant into the umbilical vessel are recommended.     

Differential timing of spring migration in northern wheatears Oenanthe oenanthe: hurried males or weak females?

In a field experiment on the island of Helgoland (southeast North Sea), we investigated whether migration strategy or competition between the sexes cause the differential timing of spring migration of male and female northern wheatears (Oenanthe oenanthe) (males migrating earlier). The study included two subspecies, heading towards Greenland/Iceland and Scandinavia, respectively, and is based on colour-ringing and remote weighing of individuals. Despite food offered ad libitum, most Scandinavian birds left the island on the day of arrival or stayed only 1–3 days, whereas more than half of Greenlandic/Icelandic birds stayed for up to 12 days and refuelled rapidly. In the latter subspecies, males showed a positive correlation of departure fuel load and fuel deposition rate, resembling time-minimizers in optimal migration theory. In contrast, females departed irrespective of fuel deposition rate, with an approximately constant level of fuel stores. This level was lower than in males, but sufficient to enable by-passing of stopover sites en route, allowing us to regard females as time-minimizers also. Since females are not able to reach Greenland without additional refuelling elsewhere and males appeared to have a larger potential for by-passing stopover sites, time-selection seems to be more pronounced in males and may be the reason for earlier migration of males. Intraspecific aggressive interactions between colour-ringed birds were predominantly won by the initiator, by males and by larger birds, whereas fuel load and subspecies did not affect the outcome. Although compared to females, males were more often dominant at the feeding stations or held territories, refuelling patterns could not be explained by dominance. Subordinate or non-territorial birds did not refuel at a lower rate or depart with lower fuel loads than dominant or territorial birds. In non-territorial birds, the restricted access to feeding stations was made up with larger doses of food taken per visit, leading to the same energy intake as that of dominant and territorial birds. Therefore, competition during stopover could be eliminated as the reason for differential timing of migration of male and female wheatears, but this result may be species-specific.Communicated by W. Wiltschko