A Survey for Outer Satellites of Mars: Limits to Completeness

We surveyed the Hill sphere of Mars for irregular satellites. Our search covered nearly the entire Hill Sphere, but scattered light from Mars excluded the inner few arcminutes where the satellites Phobos and Deimos reside. No new satellites were found to an apparent limiting red magnitude of 23.5, which corresponds to radii of about 0.09 km using an albedo of 0.07.Comment: 5 figures (1 color), 2 Tables, to appear in AJ Nov. 200

The invasion of plant communities following extreme weather events under ambient and elevated temperature

Erworben im Rahmen der Schweizer Nationallizenzen (http://www.nationallizenzen.ch)Although the problem of plant invasions is expected to increase with climate change, there is as yet little experimental evidence, in particular, for the effects of extreme weather events. We established communities of European meadow species, which were subjected to warming and extreme event (drought and deluge) treatments in a factorial design at an experimental garden in Zurich, Switzerland. Phylogenetically matched pairs of native and alien species (Bromus erectus, B. inermis, Trifolium pratense, T. hybridum, Lactuca serriola, and Conyza canadensis) were introduced into the communities to test if invader performance is favored by warming and extreme events, and if alien invaders perform better than native colonizers. With a warming of on average 0.3°C, a higher cover of native plant communities was observed, while drought decreased cover in the short-term and lowered biomass. Germination, survival, and growth of the introduced species were lower under elevated temperature. Survival of all pairs and growth of Trifolium was greater in drought pots, while deluge had no effect. While the alien species showed a faster rate of increase in the number of leaves, mortality of alien species was greater than of native species. Overall, the performance of the focal species varied much more among taxonomic groups than native/alien provenances. The results suggest that with climate change, different types of extreme events will differ in the severity of their effects on native plant communities. Meanwhile, the effects of climate change on plant invasions are more likely to operate indirectly through the impacts on native vegetation

Phase sensitive detection of dipole radiation in a fiber-based high numerical aperture optical system

We theoretically study the problem of detecting dipole radiation in an optical system of high numerical aperture in which the detector is sensitive to \textit{field amplitude}. In particular, we model the phase sensitive detector as a single-mode cylindrical optical fiber. We find that the maximum in collection efficiency of the dipole radiation does not coincide with the optimum resolution for the light gathering instrument. The calculated results are important for analyzing fiber-based confocal microscope performance in fluorescence and spectroscopic studies of single molecules and/or quantum dots.Comment: 12 pages, 2 figure

Are infestations of Cymomelanodactylus killing Acropora cytherea in the Chagos archipelago?

Associations between branching corals and infaunal crabs are well known, mostly due to the beneficial effects of Trapezia and Tetralia crabs in protecting host corals from crown-of-thorns starfish (e.g., Pratchett et al. 2000) and/or sedimentation (Stewart et al. 2006). These crabs are obligate associates of live corals and highly prevalent across suitable coral hosts, with 1–2 individuals per colony (Patton 1994). Cymo melanodactylus (Fig. 1) are also prevalent in branching corals, mostly Acropora, and are known to feed on live coral tissue, but are generally found in low abundance (<3 per colony) and do not significantly affect their host corals (e.g., Patton 1994). In the Chagos archipelago, however, infestations of Cymo melanodactylus were found on recently dead and dying colonies of Acropora cytherea

The Glenburgh Orogeny as a record of Paleoproterozoic continent-continent collision

The Gascoyne Province lies at the western end of the Capricorn Orogen, and includes a range of Paleoproterozoic gneisses and metasedimentary basins, known as the Glenburgh Terrane, that are exotic to both the Yilgarn and Pilbara Cratons. Here we present sensitive high-resolution ion microprobe (SHRIMP) U–Pb ages for a variety of detrital zircons and metamorphic zircon and monazite from several of these pre-collisional siliciclastic basins that were deformed and metamorphosed at high metamorphic grade during the Glenburgh Orogeny, when the Yilgarn Craton collided with a previously assembled Pilbara Craton – Glenburgh Terrane. The precursors to the Moogie Metamorphics were deposited sometime between 2240 and 2125 Ma in either a foreland basin to the Ophthalmian Orogeny, or a retro-arc that formed during the collision of the Glenburgh Terrane with the Pilbara Craton. The Quartpot Pelite of the Camel Hills Metamorphics was deposited between 2000 Ma and 1985 Ma as a fore-arc deposit to the Dalgaringa continental margin arc. The Petter Calc-silicate of the Camel Hills Metamorphics was deposited sometime between 2610 and 1965 Ma as part of the Yilgarn Craton passive margin. Metamorphic zircon and monazite ages indicate that continental collision and high-grade metamorphism during the Glenburgh Orogeny (D2g) took place between 1965 Ma and 1950 Ma

Visual Climate Change Communication: From Iconography To Locally Framed 3D Visualization

Climate change is an urgent problem with implications registered not only globally, but also on national and local scales. It is a particularly challenging case of environmental communication because its main cause, greenhouse gas emissions, is invisible. The predominant approach of making climate change visible is the use of iconic, often affective, imagery. Literature on the iconography of climate change shows that global iconic motifs, such as polar bears, have contributed to a public perception of the problem as spatially and temporally remote. This paper proposes an alternative approach to global climate change icons by focusing on recognizable representations of local impacts within an interactive game environment. This approach was implemented and tested in a research project based on the municipality of Delta, British Columbia. A major outcome of the research is Future Delta, an interactive educational game featuring 3D visualizations and simulation tools for climate change adaptation and mitigation future scenarios. The empirical evaluation is based on quantitative pre/post-game play questionnaires with 18 students and 10 qualitative expert interviews. The findings support the assumption that interactive 3D imagery is effective in communicating climate change. The quantitative post-questionnaires particularly highlight a shift in support of more local responsibility

Azimuthally polarized spatial dark solitons: exact solutions of Maxwell's equations in a Kerr medium

Spatial Kerr solitons, typically associated with the standard paraxial nonlinear Schroedinger equation, are shown to exist to all nonparaxial orders, as exact solutions of Maxwell's equations in the presence of vectorial Kerr effect. More precisely, we prove the existence of azimuthally polarized, spatial, dark soliton solutions of Maxwell's equations, while exact linearly polarized (2+1)-D solitons do not exist. Our ab initio approach predicts the existence of dark solitons up to an upper value of the maximum field amplitude, corresponding to a minimum soliton width of about one fourth of the wavelength.Comment: 4 pages, 4 figure