Lethal and non-lethal effects of multiple indigenous predators on the invasive golden apple snail (Pomacea canaliculata)

1. We investigated the individual and combined effects of two predators (the climbing perch, Anabas testudineus, and the wetland crab, Esanthelphusa nimoafi) indigenous to wetlands in Laos, on the behaviour and survival of the invasive South American golden apple snail (Pomacea canaliculata). The snail is considered a pest, consuming large amounts of rice and other aquatic vegetation in the region. 2. Snail avoidance reactions to released predator chemical cues were investigated in aquaria while the effects of predators on a mixed snail population were studied in field enclosures that contained native aquatic plants (Salvinia cucullata, Ludwigia adscendens and Ipomoea aquatica). 3. In the aquaria experiment, neonate (2-3 mm) and medium-sized snails (8-10 mm) responded to fish chemical cues by going to the surface, whereas adult snails (35-40 mm) went to the bottom. In contrast, no size class of snails reacted to chemical cues released by crabs. 4. In the field experiment, fish reduced the abundance of neonate snails, and crabs reduced the abundance of all size classes. The effect of the combined predators could not be predicted from the mortality rate observed in single predator treatments. The survival of neonate and medium-sized snails was greater and of adults less than expected. The presence of predators did not affect egg production. Snails consumed significant amounts of plants despite the presence of predators. 5. Our findings suggest that some indigenous Asian predators have lethal and sublethal effects on P. canaliculata that depend on snail size and predator type. When in the presence of several predators the response of snails to one predator may either increase or decrease the vulnerability of snails to the others

Electron-spectroscopy study of LiC60: Charge transfer and dimer formation

Li−C60 compounds Lix¯C60 were studied for average Li concentration x¯<~1 using photoelectron spectroscopy. Strong evidence is found for the formation of LiC60 dimers, as well as a second phase. The study suggests that the smallest alkali-metal Li bonds to C60 largely ionically for certain configurations. An investigation of the Li 1s level shows that under certain conditions the energetics favor a backdonation of the transferred electron to the Li ion

Formation and Structure of Graphene Waves on Fe(110)

A very rich Fe-C phase diagram makes the formation of graphene on iron surfaces a challenging task. Here we demonstrate that the growth of graphene on epitaxial iron films can be realized by chemical vapor deposition at relatively low temperatures, and that the formation of carbides can be avoided in excess of the carbon-containing precursors. The resulting graphene monolayer creates a novel periodically corrugated pattern on Fe(110). Using low-energy electron microscopy and scanning tunneling microscopy, we show that it is modulated in one dimension forming long waves with a period of similar to 4 nm parallel to the [001] direction of the substrate, with an additional height modulation along the wave crests. The observed topography of the graphene/Fe superstructure is well reproduced by density functional theory calculations, and found to result from a unique combination of the lattice mismatch and strong interfacial interaction, as probed by core-level photoemission and x-ray absorption spectroscopy

Dublin Core in practice : A survey on the usage of Dublin Core within five Swedish search engines

The purpose of this thesis is to investigate how the metadata format Dublin Core is applied within five Swedish search engines. The objects of the investigation are Rättskällan, studera.nu, Svenska miljönätet, Svesök and the web catalogue of Uppsala University. Dublin Core is a flexible and adjustable format, which can be used in many different ways and in various projects depending on the target groups and objectives of the activity. We compare the differences and similarities between the five search engines concerning their usage of metadata in general and Dublin Core in particular. The material of the investigation consists of metadata records, which are collected by a robot and examined manually. We present the reader with an overview of the metadata concept and explain in particular the Dublin Core Metadata Element Set. The review of the investigation result begins with a presentation of the five search engines and is concluded by an exposition of the usage frequency of the fifteen Dublin Core elements within the examined search engines. The five search engines show notable differences with respect to the usage of Dublin Core. The number of Dublin Core elements in the templates of these search engines varies from five to fifteen, and furthermore different priorities have been given to the selection of mandatory elements and qualifiers. The investigation shows that the metadata producers often limit themselves to registration of the mandatory elements. The study shows further that the differences are bigger than the similarities concerning the usage of metadata within the five search engines. The search engines take advantage of the flexibility of the format by focusing on different elements and qualifiers and complementing the descriptions of the resources with different types of additions. We conclude that the search engines have to collaborate and coordinate their usage of metadata in order to improve public access to reliable and trustworthy information on the Internet.Uppsatsnivå: