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  • 1
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Based on its Mediterranean origins and close relationship with other highly invasive Asteraceae species, Crupina vulgaris was declared a Federal Noxious Weed shortly after its discovery in Idaho in 1968. Twenty-two years later, surveys revealed over 25 500 ha infested with five separate populations in four states. Despite this expansion, no-one knew how this unlikely invader with its large seed was moving long distances or how it had escaped detection entering the country. The objectives of this study were to characterize the invasion history by estimating when, how, from where and how many times Crupina vulgaris was introduced in North America. Methods included molecular markers (random amplification of polymorphic DNA), distribution maps and historical sleuthing. Molecular markers linked all five North American populations with the Iberian Peninsula, with at least three colonization events. Distribution maps limited the area to northern Spain, where C. vulgaris occurs outside the range of Crupina crupinastrum. Site histories indicated four, perhaps five, successful introductions from northern Spain, associated with Basque sheepherders. Two remote sites (Lake Chelan, WA, and Modoc County, CA) had direct links with northern Spain from the 1950s into the 1970s. It appeared that the other introductions also occurred decades before the discovery dates. Detailed knowledge of individual invasion case histories is relevant for preventing future weed introductions and as a framework for future ecological investigations, such as effects of selection pressures during immigration or niche relationships in native and introduced habitats.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2207-2210 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A coaxial niobium quarter-wave resonant cavity has been fabricated and used for measurement of the surface resistance of disk-shaped samples of high-Tc superconductors at 820 MHz and 4.2 K, and at surface rf magnetic fields ranging to 300 G. The cavity can accommodate samples as large as 36 mm in diameter. A measurement procedure has been developed with which rf surface resistances less than 20 μΩ can be resolved for a 24-mm-diam sample at 820 MHz. This cavity is useful in determining the suitability of high-Tc superconductors for high-power rf applications.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The increase in the microwave surface resistance Rs of high Tc superconductors at elevated microwave power levels is reported for both oriented and unoriented Tl-based films as a function of rf magnetic field at 820 MHz and 18 GHz. The application of dc magnetic fields produces qualitatively similar increases in Rs and in the surface reactance Xs. The increase in Rs with dc field is shown to arise from simple decoupling of grains by intergranular magnetic flux. The increase in Rs with microwave power, on the other hand, is a consequence of hysteretic intergranular processes.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 274 (1975), S. 131-137 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The fission fragment angular distributions from reactions of 140-MeV4He ions with238U,209Bi and197Au have been studied. From the anisotropies in the angular distributions, values forℊ eff, the effective moment of inertia at the fission saddle point, have been estimated and compared with results obtained at lower bombarding energies. The derivation ofℊ eff values has included corrections for the effects of incomplete fusion mechanisms on the orbital angular momentum distribution of the fissioning nuclei and for neutron evaporation prior to fission. The results are also compared with heavy-ion-induced fission data for systems of similar fissility. Also, examination of the forward-backward symmetry of the238U angular distribution substantiates other results which show that the fraction of fission reactions which follow complete fusion of the target and projectile is less than 0.5 for 140-MeV4He-ion bombardment of238U.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of superconductivity 3 (1990), S. 243-250 
    ISSN: 1572-9605
    Keywords: High-T c ; superconductors ; microwave ; accelerator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We report measurements of the r.f. surface resistance of a wide variety of high-T c superconductors in bulk form and as films on silver substrates. Several apparatuses have been constructed and used for measurements at frequencies from 0.15 to 40 GHz and r.f. surface magnetic fields as high as 640 G. In every case in which the field dependence of the surface resistance was measured, the surface resistance increased monotonically with field amplitude through a transition region characterized by a strong field dependence. It then saturated at high field at a value of a few percent of the normal-state surface resistance just aboveT c . In the presence of this field dependence, the frequency dependence of the surface resistance changed from quadratic to less than linear.
    Type of Medium: Electronic Resource
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