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Level Interactions (level + interaction)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Bottom-up, top-down, and within-trophic level pressures on a cactus-feeding insect

ECOLOGICAL ENTOMOLOGY, Issue 2 2008
TOM E. X. MILLER
Abstract 1.,The relative importance of host-plants and predators in the population dynamics of herbivorous insects, and the frequency and intensity of inter-specific competition among herbivores, have both been intensively studied and debated. The joint effects of bottom-up, top-down, and within-trophic level interactions, however, have rarely been integrated in a single system. 2.,I studied the dynamics of the cactus bug (Narnia pallidicornis), a specialist feeder on tree cholla cactus (Opuntia imbricata), in response to variable host-plant quality, spider predation, and interactions with cactus-feeding beetles (Moneilema appressum). Previous work suggests that cactus reproductive effort (the proportion of meristems allocated to reproduction) is an important component of host-plant quality for Narnia. I conducted a 2-year field experiment to test the hypotheses that Narnia abundance is positively related to host-plant reproductive effort, and that interactions with predators and putative competitors alter the shape of this relationship. 3.,I found strong support for the first prediction (positive Narnia,plant quality relationship) in both years, but neither predator removal nor beetle exclusion had detectable effects on this relationship in either year. I conclude that the dynamics of this insect herbivore are driven predominantly from the bottom-up, and that available data from this work and from previous studies are too variable to permit broad generalisations for the combined effects of host-plants, predation, and competition on herbivore dynamics. [source]

Polyaniline Entrapped in Silver: Structural Properties and Electrical Conductivity

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2009
Guy Nesher
Abstract By employing the new methodology of entrapment of organic molecules within metals, we demonstrate the ability to modify the conductivity of a metal by suitable polymer entrapment. Specifically, polyaniline (PANI) in two molecular weights was entrapped in silver at different concentrations and a comprehensive comparison was preformed for a range of the composite properties, characterized by XRD, SEM, BET, TGA, and density measurements. Pressed films were utilized to measure the electrical conductivity of the composites in order to study the PANI-silver interactions at the molecular level and to establish a correlation between the microscopic morphology and the film conduction. Such correlations have been identified, and are interpreted. This work extends the functional applications of the new metallic composites and offers insight on the polymer-metal molecular level interactions. [source]

Child sun protection: Sun-related attitudes mediate the association between children's knowledge and behaviours

JOURNAL OF PAEDIATRICS AND CHILD HEALTH, Issue 12 2008
Caradee Wright
Aim: To describe and investigate the relationship among the sun-related knowledge, attitudes and behaviours of New Zealand primary schoolchildren and consider the roles of sex and school year level. Methods: A randomly selected, two-stage cluster sample of 488 children from 27 primary schools in five regions of New Zealand was surveyed regarding their sun-related knowledge, attitudes and behaviours. A scoring system was used to assign a knowledge, attitude and behaviour score to each child. Results: Although knowledge increased with school year level, there was a decline in sun protective attitudes and behaviours. There was little variation in knowledge, attitudes and behaviour between boys and girls, but sex,year level interactions were found for knowledge and behaviour. When considering children's knowledge, attitudes and behaviours simultaneously, knowledge was only significantly associated with behaviours when mediated by attitudes. Conclusions: When targeting child sun protection and skin cancer prevention programmes, a focus on attitudes towards sun exposure and a suntan may prove beneficial in influencing sun-related behaviours. [source]

Synthesis and properties of magnetite/poly (aniline-co-8-amino-2-naphthalenesulfonic acid) (SPAN) nanocomposites

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2007
Kakarla Raghava Reddy
Abstract Composites were prepared by incorporating magnetite (Fe3O4) nanoparticles into the matrix of a sulfonated polyaniline (SPAN) [poly(aniline-co-8-amino-2-naphthalenesulfonic acid) PANSA] through chemical oxidative polymerization of a mixture of aniline and 8-amino-2-naphthalenesulfonic acid in the presence of magnetite nanoparticles. The composite, magnetite/SPAN(PANSA) was characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD), elemental analysis (EA), Fourier transform infrared (FT-IR) spectra, UV-vis spectroscopy, thermogravimetric analysis (TGA), conductivity and magnetic properties measurements. TEM image shows that magnetite nanoparticles were finely distributed into the SPAN matrix. XRD pattern of the nanocomposite reveals the presence of additional crystalline order through the appearance of a sharp peak at ,43° and 71°. Conductivity of the nanocomposite (0.23,S/cm) is much higher than pristine copolymer (1.97,×,10,2,S/cm). The results of FT-IR and UV-visible spectroscopy reveal the presence of molecular level interactions between SO groups in SPAN and magnetite nanoparticles in the composite. Copyright © 2006 John Wiley & Sons, Ltd. [source]