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Artificial Structures (artificial + structure)
Selected AbstractsDescriptions and biological notes of Ctenoplectra bees from Southeast Asia and Taiwan (Hymenoptera: Apidae: Ctenoplectrini) with a new species from North BorneoENTOMOLOGICAL SCIENCE, Issue 3 2009I-Hsin SUNG Abstract Six Ctenoplectra species are recorded from Southeast Asia and Taiwan. They are C. chalybea Smith, C. cornuta Gribodo, C. davidi Vachal, C. elsei Engel, C. sandakana sp. nov. and C. vagans Cockerell. Females of C. sandakana sp. nov. from North Borneo are similar to the mainland species C. chalybea, but differ mainly in the clypeal keel and the length of the antennal segments. The small blackish species, C. cornuta, is distributed in Myanmar, China and Taiwan and C. davidi is distributed in China, Russia and Taiwan; both species are seen at the flowers of Thladiantha. Ctenoplectra chalybea was collected from the Malay Peninsula, Myanmar, Taiwan and Vietnam. Ctenoplectra apicalis Smith and C. kelloggi Cockerell are allied to C. chalybea; however, C. kelloggi is excluded from this study due to insufficient material. A key to the six known Ctenoplectra species is given. The large metallic species, C. chalybea and C. elsei, visit flowers of Momordica cochinchinensis (Lour.) Spreng. For the first time observations on the nest structures of C. chalybea and C. cornuta are presented. They choose remarkable places, such as artificial structures and buildings, for nest sites. The nest architecture prevents rain and direct sunlight from entering the nest. Bees used pre-existing holes or crevices in wood for nesting shelters and collected soil and appeared to mix it with some other substance to build nests. The cell lining materials and rubbing behaviors against the cell wall suggest that Ctenoplectra bees use floral oil mainly for cell lining materials. [source] Visual isolation furthers access to drift-feeding positions for subordinate juvenile brown trout (Salmo trutta) in dominance hierarchiesJOURNAL OF FISH BIOLOGY, Issue 2003J-M. Roussel Juvenile salmonids are visual predators that primarily feed on drifting invertebrates and compete for suitable feeding positions in swift water. We used an outdoor experimental stream to test the effect of visual isolation on agonistic interactions and habitat use by age-1 brown trout (Salmo trutta) in riffle-pool sections. We hypothesized that dominant fish defend suitable feeding positions in riffle and that visual obstruction between individuals enhance access to riffle for subordinates. Groups of juveniles, caught in the wild, were stocked in high and low visibility treatments. Visual isolation was manipulated by placing dark plastic ribbons or opaque Plexiglas boards onto the substrate of riffles. As expected, dominant fish held profitable positions in riffle and the proportion of fish in riffle significantly increased in presence of artificial structures. In high visibility treatment, the dominant fish despotically excluded subordinates from the riffle. In low visibility treatment, the proportion of fish that foraged on benthic prey in the pool and the number of major aggressive acts (chase, nip) decreased. Our results support the hypothesis that screening effect of physical structures in the water column loosen resource monopolization in dominance hierarchies of juvenile salmonids. [source] Fabrication of Artificial Petal Sculptures by Replication of Sub-micron Surface Wrinkles,MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2010Alexandra Schweikart Abstract In this contribution, we discuss wrinkling as a process resulting in well-defined periodic micron-sized structures, as known from the interface of several plant cells. We show possible pathways to transfer this principle to artificial materials such as epoxy resins or polymers. While topographical structuring of surfaces by wrinkling is meanwhile well established for elastomers like poly (dimethyl siloxane), so far the step towards other classes of materials has not been taken. This puts several limitations to potential applications of artificial wrinkled structures, as elastomers show poor dimensional stability, low optical quality, and tend to swell in organic solvents. As well, artificial structures formed by wrinkling are not tension-free on the microscopic level, which makes them metastable. Residual mechanical tensions can affect dimensional stability on long timescales. We introduce two processes, micro thermoforming and molding, as means to overcome these restrictions and to pattern non-elastomeric materials by using wrinkled elastomers as templates. The two approaches allow the formation of negative and positive replicas and allow the transfer of sub-micron features with high fidelity. [source] Striking a balance between retaining populations of protected seahorses and maintaining swimming netsAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2010David Harasti Abstract 1.The fish family Syngnathidae (seahorses, pipefish, pipehorses and seadragons) is fully protected in New South Wales, Australia, but in some countries certain species are threatened by unsustainable collecting, capture as incidental bycatch, and habitat degradation. 2.Within Sydney Harbour, two species of seahorses (Hippocampus abdominalis and Hippocampus whitei) have been found to colonize artificial structures such as jetty pylons and protective netted swimming enclosures. These protective nets are subject to fouling from epibiotic growth (algae, ascidians, bryozoans, etc.) and rubbish, which causes the nets to collapse from the additional weight. Local authorities employ diving contractors on an ad hoc basis to remove the epibiota from nets. 3.Surveys showed a significant decline in the numbers of both seahorse species at one site following the replacement of a net, and recovery of the H. whitei population took more than 15 months. 4.A manipulative experiment tested the importance of epibiotic growth for seahorses. H. whitei, tagged with individual marks, were allocated to sections of a net that had undergone different cleaning procedures. Seahorse size, position on the net and total population abundance were recorded every 2 weeks over a 3 month period. It was demonstrated that seahorses have a significant positive association with epibiotic growth and proximity to the sea floor. Seahorse populations also showed seasonal variation in abundance with increased numbers on the net during the breeding season (spring,summer). 5.This project has led to the development of best practice net cleaning procedures for local authorities in Sydney Harbour to manage growth on the nets while minimizing impacts on seahorse populations. Copyright © 2009 John Wiley & Sons, Ltd. [source] Fish assemblages associated with urban structures and natural reefs in Sydney, AustraliaAUSTRAL ECOLOGY, Issue 2 2008B. G. CLYNICK Abstract Fish ecology in urban estuaries is poorly understood. As coastal landscapes are transformed, recognizing the impact that urban structures, such as marinas, seawalls and wharfs, have on local fish populations is becoming increasingly important. The extent to which fish are able to maintain natural ecological assemblages can be measured, to a certain extent, by how closely they mimic natural habitats. In Sydney Harbour, assemblages of fish associated with artificial structures were compared with those associated with natural rocky reefs. Sampling was carried out in five locations, each with a marina, swimming enclosure and natural reef. In each location, different habitats supported different assemblages, but differences between habitats were not consistent among locations. Subsequent sampling compared artificial and natural sites in three different areas in each of three different estuaries. Results indicated that differences in fish assemblages between artificial and natural sites were greater than differences between sites within each habitat, but there were no patterns among different positions in an estuary or from estuary to estuary. This study provides initial evidence that, although artificial habitats generally support the same species as found on natural reefs, assemblages usually differed between natural and artificial habitats. In addition, without knowing if these habitats do, in fact, sustain viable populations of fish, it would be premature to label artificial structures as effective habitat for fish. [source] | ||||||||||