3,126 research outputs found

    A study of the freshwater dinoflagellates Ceratium hirundinella and Ceratium furcoides with special reference to their taxonomy and recent history in the Lake District

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    Motile cells and cysts of Ceratium were studied usinglight and scanning electron microscopy. Two species, C. hirundinella and C. furcoides, were distinguished on the basis of the cell length to breadth ratio, the shape of the epithecaand the arrangement of apical plates. Cysts differed in shape and in the length of the horns. Analytical scanning electronmicroscopy demonstrated the presence of silicon in the multi-layered granular wall of the cysts of both species.The vertical distribution of viable cysts of C. furcoides and C. hirundinella was studied in 8 cm cores taken over threeseasons from Esthwaite Water, Cumbria. The diatom Stephanodiscus parvus was used as a marker species, to attribute a time scale to the cores. Some agreement was demonstrated between cyst numbers and past populations of Ceratium spp., although the majority of cysts occurred in the upper 4 cm of the cores. A study of the proportion of C. hirundinella to C. furcoides cells from 1946-1986 showed that the ratio of each species changed markedly over this period. It was concluded that the relative numbers of each species were determined by the proportion of cysts germinating in the spring, with parasitism an important factor in controlling cyst viability.Germination of the cysts of both species was induced in the laboratory. The excystment of C. furcoides was achieved down to a depth of 5.5 cm, from cysts with an equivalent age of approximately 7 years. Cysts from sediment which had been leftto dry out failed to germinate.The Ceratium populations of several southern sites were also studied. The number of Ceratium cells was shown to decline when the water column was disturbed, either by the input of water through high velocity jets, or the failure to form a stable thermocline. C. hirundinella was observed to be the more numerous of the two species in the reservoirs studied, but in Virginia Water Lake C. furcoides occurred in greater numbers. <p

    The Grizzly, September 4, 2003

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    A Space to Call Your Own • Pay for Print Solution • Bumpy Ride • Spotlight on Politics: The California Recall • Feeling Disconnected: Internet and Virus Woes • A Plan for Every Future: Career Services Fall 2003 • Opinions: Campus Rooms: Is Space Running Out?; Network Gripes Getting you Down? Elections in California: Business as Usual or Free for All? • Activities, Activities, Activities • Calling all Thespians! • Ursinus in 1893: What was it Like? • New Arts Center • Local Heritage Day Celebration • Bears Versatility Makes the Season Look Promising • UC Field Hockey Team: Ready to Rumble • Promising Season Abound for the Men and Women\u27s Soccer Teams • Ursinus Cross Country Kicks-off • Ursinus Volleyball Team Off to Rough Start • X-Country Team Scoreshttps://digitalcommons.ursinus.edu/grizzlynews/1539/thumbnail.jp

    Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

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    The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum
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