1,465 research outputs found
The Distribution, Abundance, and Communities of Deepwater Hawaiian Crustose Corallinaceae (Rhodophyta, Cryptonemiales)
Two deepwater (8-28 m) areas studied off Oahu, Hawaii, are remarkably
similar in the kinds and order of importance of calcareous producer organisms.
Hydrolithon breviclavium is primary at the Maile deep area (25-percent cover) as well
as at Waikiki (37-percent cover). At Maile H. reinboldii (7-percent cover) ranks
second in relative importance; however, at Waikiki Tenarea tessellatum (5-percent
cover) and corals (3-percent cover) are so abundant at the stations below 20 m that
they surpass H. reinboldii (2 percent) in total cover. Corals (2-percent cover) and
T. tessellatum (I-percent cover) rank third and fourth, respectively, as important
builders in the Maile deep area. At Waikiki, when density and frequency are considered
with the cover values, corals are second in importance followed by H.
reinboldii and T. tessellatum. The deepwater crustose Corallinaceae (38-percent mean
cover) overshadow all other calcareous organisms in terms of standing stock and
also seem to have more biological influence than do the other limestone producers
The Annual Distribution of Phytoplankton Communities in a Southeastern Ohio Pond
Author Institution: Department of Population and Environmental Biology, University of California, and Department of Botany, Ohio UniversityThe phytoplankton communities of a southeastern Ohio pond were monitored weekly from October 1964 to October 1965. Ninety taxa were identified: 56 Chlorophyta, 6 Chrysophyta, 14 Cyanophyta, 10 Euglenophyta, and 4 Pyrrhophyta. The pond was partially drained and the fish were removed during winter 1964; this had no marked effect on the phytoplankton community present at that time. Prominant pulses occurred during fall 1964, April 1965, and summer 1965; the fall and summer peaks were associated with pH values greater than 9.0. The fall pulse was comprised of Anabaena planctonica, A . spiroides var. crassa, Botryococcus braunii, and Ceratium hirundinella. Major components of the April pulse were Dinobryon cylindricum, Oscillatoria limosa, 0. amphibia, C. hirundinella, and Uroglena americana. During the summer pulse a distinct succession of dominants was evident, with the community in July composed of Staurastrum uniseriatum, Scenedesmus spp., Pediastrum duplex, and Euglena spp., giving way to a community in August that included Staurastrum tetracerum, Closterium spp., and Euastrum denticulatum; the last community being displaced in September by a Glenodinium quadridens, Scenedesmus spp., Anabaena sp., P. duplex community
Technology requirements for advanced earth-orbital transportation systems, dual-mode propulsion
The application of dual-mode propulsion concepts to fully reusable single-stage-to-orbit (SSTO) vehicles is discussed. Dual-mode propulsion uses main rocket engines that consume hydrocarbon fuels as well as liquid hydrogen fuel. Liquid oxygen is used as the oxidizer. These engine concepts were integrated into transportation vehicle designs capable of vertical takeoff, delivering a payload to earth orbit, and return to earth with a horizontal landing. Benefits of these vehicles were assessed and compared with vehicles using single-mode propulsion (liquid hydrogen and oxygen engines). Technology requirements for such advanced transportation systems were identified. Figures of merit, including life-cycle cost savings and research costs, were derived for dual-mode technology programs, and were used for assessments of potential benefits of proposed technology activities. Dual-mode propulsion concepts display potential for significant cost and performance benefits when applied to SSTO vehicles
Technology requirements for advanced earth-orbital transportation systems: Summary report
Areas of advanced technology that are either critical or offer significant benefits to the development of future Earth-orbit transportation systems were identified. Technology assessment was based on the application of these technologies to fully reusable, single-state-to-orbit (SSTO) vehicle concepts with horizontal landing capability. Study guidelines included mission requirements similar to space shuttle, an operational capability beginning in 1995, and main propulsion to be advanced hydrogen-fueled rocket engines. The technical and economic feasibility of this class of SSTO concepts were evaluated as well as the comparative features of three operational take-off modes, which were vertical boost, horizontal sled launch, and horizontal take-off with subsequent inflight fueling. Projections of both normal and accelerated technology growth were made. Figures of merit were derived to provide relative rankings of technology areas. The influence of selected accelerated areas on vehicle design and program costs was analyzed by developing near-optimum point designs
Marine Macroalgal Diversity Assessment of Saba Bank, Netherlands Antilles
Background: Located in the Dutch Windward Islands, Saba Bank is a flat-topped seamount (20â45 m deep in the shallower regions). The primary goals of the survey were to improve knowledge of biodiversity for one of the worldâs most significant, but little-known, seamounts and to increase basic data and analyses to promote the development of an improved management plan. Methodology/Principal Findings: Our team of three divers used scuba to collect algal samples to depths of 50 m at 17 dive sites. Over 360 macrophyte specimens (12 putative new species) were collected, more than 1,000 photographs were taken in truly exceptional habitats, and three astonishing new seaweed community types were discovered. These included: (1) ââField of Greensâ â (N 17u30.6209, W63u27.7079) dominated by green seaweeds as well as some filamentous reds, (2) ââBrown Townâ â (N 17u28.0279, W63u14.9449) dominated by large brown algae, and (3) ââSeaweed Cityâ â (N 17u26.4859, W63u16.8509) with a diversity of spectacular fleshy red algae. Conclusions/Significance: Dives to 30 m in the more two-dimensional interior habitats revealed particularly robust specimens of algae typical of shallower seagrass beds, but here in the total absence of any seagrasses (seagrasses generally do not grow below 20 m). Our preliminary estimate of the number of total seaweed species on Saba Bank ranges from a minimum of 150 to 200. Few filamentous and thin sheet forms indicative of stressed or physically disturbed environments were observed. A more precise number still awaits further microscopic and molecular examinations in the laboratory. The expedition, while intensive, has only scratched the surface of this unique submerged seamount/atoll
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Progressive voices in the arts and heritage sector have called for a politics of cultural democracy as a means of empowering all to participate in public life. Through a rejection of policies of 'inclusion', they have asked more searching questions about the role culture can play in the fight for social justice. At the same time the sector is preparing for a change of ideological direction, as rumours run rife about what a future Tory government, highly critical of state intervention, will do to the bodies that run the arts and heritage sector. This article looks at the prospects for a radical cultural democracy in the face of these potential political changes
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Creative hubs: a co-operative space?
How equitable and co-operative are creative hubs? Whilst their image is often one of creative conviviality, their political economies are often fairly diverse; including a range of forms of cultural industry from the corporate to the co-operative. Indeed, we might, for example, map a spectrum or a taxonomy of co-working ranging from corporate industries leasing communal space to cultural workers through to the workerâs co-operative where responsibilities and profits are shared. Drawing on a range of historical material and contemporary interviews with workerâs co-operatives in the cultural sector, this chapter considers the benefits brought by workerâs co-ops to cultural hubs in London in both their contemporary and recent historical manifestations. Taking a critical and polemical stance, it argues that supporting workerâs co-operatives should be central to any strategic provision for creative hubs
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