5,542 research outputs found
Correspondence -- George S. Ricker, 1932-1935
No full textA set of correspondence between Bates President Clifton D. Gray and George S. Ricker, member of the Bates class of 1867 (first graduating class of the college), plus one additional letter from Alumni Secretary Harry Rowe. Much of the correspondence concerns Ricker\u27s disagreement over the College giving retroactive degrees to two women--Sybill Chase Ballard and Francena White Morrell--who went to Bates for a time with the 1867 class but did not graduate. Ricker talks about the events concerning coeducation and the comings and goings of various female students in Bates\u27 first years
On Mean Ergodic Operators
No full textAspects of the theory of mean ergodic operators and bases in Fréchet spaces were recently developed in [A.A. Albanese, J. Bonet, W.J. Ricker, Mean ergodic operators i Fréchet spaces, Ann. Acad. Sci. Math. Fenn. Math. 34 (2009), 1-36]. This investigation is extended here to the class of barrelled locally convex spaces. Duality theory, also for operators, plays a prominent role
Grothendieck spaces with the Dunford-Pettis property
No full textBanach spaces which are Grothendieck spaces with the Dunford-Pettis property (briefly, GDP) are classical. A systematic treatment of GDP-Fréchet spaces occurs in Bonet and Ricker (Positivity 11.77-93, 2007). This investigation is continued here for locally convex Hausdorff spaces. The product and (most) inductive limits of GDP-spaces are again GDP-spaces. Also, every complete injective space is a GDP-space. For p\in \{0}\cup [1,\infty) it is shown that the classical co-echelon spaces and K_p(\ov{V}) are GDP-spaces if and only if they are Montel. On the other hand, K_\infty(\ov{V}) is always a GDP-space and is a GDP-space whenever its (Fréchet) predual, i.e., the Kothe echelon space , is distinguished
Leuctra moha in Ricker 1952
No full textLeuctra moha Ricker, 1952 Blackwater Needlefly http://lsid.speciesfile.org/urn:lsid: Plecoptera.speciesfile.org:TaxonName:4523 (Figs. 1–8, 13) Leuctra (Leuctra) moha Ricker 1952:169. Holotype ♂ (INHS), Mossy Creek, 4.6 mi N Perry, (Houston or Peach Co.), Georgia, USA (examined) Leuctra moha Illies, 1966:100 Leuctra moha Harper & Harper, 1997:472Published as part of Grubbs, Scott A., Metzger, Madeline L. & Wei, Summer, 2020, Systematics of eastern Nearctic Leuctra moha Ricker, 1952 with notes on L. hicksi Harrison & Stark, 2010 (Plecoptera: Leuctridae), pp. 361-373 in Zootaxa 4768 (3) on page 364, DOI: 10.11646/zootaxa.4768.3.3, http://zenodo.org/record/378405
Keith Gendreau, Mark Bautz, George Ricker
No full textWe report measurements of effects of 2.1 MeV and 40 MeV protons on Charge Coupled Device X-ray detectors of a type soon to be launched on several astronomical research satellites. We discuss ground performance characterization techniques and compare our measurements to simple models of the detector damage mechanism. We predict detector peformance degradation rates in low-earth orbit. We plan to compare these predictions to early flight data obtained from the Solid State Imaging Spectrometer (SIS) focal plane instrument mounted on the Japan/US X-ray astronomy satellite Asuka launched on February 20, 1993. Introduction At MIT, we are developing photon counting imaging x-ray spectrometers using Charge Coupled Device (CCD) detectors for several astronomical research satellites. The first of these, the Japan/US mission Asuka, has been developed jointly by the Japanese Institute for Space and Aeronautical Science (ISAS) and the National Aeronautics and Space Administration (NASA) (Ricker e..
A dinâmica do modelo populacional de Ricker
No full textO modelo de Ricker é um dos vários modelos utilizados em ecologia para descrever a dinâmica
populacional que depende da densidade ao longo do tempo, observada em intervalos de tempo
discreto. Este modelo é adequado para estudar espécies onde as estimativas anuais (ou
geracionais) de abundância são caracterizadas adequadamente como dinâmica populacional e para
transições entre estágios da história de vida, tais como produção de descendentes ou sobrevivência
de um estágio para o próximo. A última aplicação é comum na ciência da pesca, onde o modelo
de Ricker é frequentemente usado para relacionar a produção de recrutas (peixes jovens que
sobrevivem para se juntar à população) a fatores na densidade observada, tais como abundância,
biomassa total ou potencial total de desova de peixes adultos, como parte de um modelo
populacional abrangente.
O objetivo deste trabalho é aplicar alguns resultados da teoria de estabilidade de sistemas
dinâmicos discretos ao Modelo de Ricker. Em particular, estudamos a dinâmica populacional em
ambos os casos, no modelo autónomo e no modelo não autónomo.The Ricker model is one of several models used in ecology to describe population dynamics that
depend on density over time, observed at discrete intervals. This model is suitable for studying
species where annual (or generational) estimates of abundance are adequately characterized as
population dynamics, and for transitions between life history stages, such as offspring production
or survival from one stage to the next. The latter application is common in fisheries science, where
the Ricker model is frequently used to relate the production of recruits (young fish that survive to
join the population) to factors in observed density, such as abundance, total biomass, or total
potential spawning of adult fish, as part of a comprehensive population model.
The objective of this work is to apply some results from the theory of stability of discrete dynamic
systems in the Ricker model. In particular, we study population dynamics in both autonomous and
non-autonomous cases
Bolshecapnia Ricker 1965
No full text<i>Bolshecapnia</i> Ricker, 1965 <p>(Figs. 17–18, 29, 33)</p> <p> <i>Capnia (Bolschecapnia)</i> Ricker, 1965 — Ricker 1965: 478. (misspelling in the stating of the name, used as <i>Bolshecapnia</i> elsewhere in the original description).</p> <p> <i>Capnia (Bolshecapnia)</i> Ricker, 1965 — Ricker 1965: 478. (original description, type species <i>Capnia (Bolshecapnia) gregsoni</i> Ricker, 1965).</p> <p> <i>Capnia</i> Pictet, 1841 — Zwick 1973: 370. (synonymy of <i>Capnia (Bolschecapnia)</i> Ricker, 1965 with <i>Capnia</i> Pictet, 1841).</p> <p> <i>Bolshecapnia</i> Ricker, 1965 — Ricker & Scudder 1975: 333. (first use as a generic name, without formal designation and removed from synonymy).</p> <p> <b>Diagnosis.</b> Male epiproct: B-scl large, divided from Ep-scl; Lb-scl small, divided from Ep-scl; Ep-scl laterally divided in the apical part or the whole length with membranous connecting tissue, ventrally divided in the basal and apical or only in the apical section, caudal setae absent; I-scl long, divided hook or tube; Ec present. Male Pp: apical part long and narrow; Fp long and narrow, divided from Rp. Male Sg: divided from St 9 and Tg 9, vesicle present. Female Sg: pointed or rounded, narrower than St 8 but usually overhanging; lateral sclerites present. Male tergites: Tg 9 with process or process lacking. Ventral thoracic sclerites: MPrs and MeFs triangular, MeFsp separated from MePfs. Macropterous wings: forewing A1 beyond a straight or gently curved, R1 before r curved; crossveins between C and Sc one to eight, R veins three to six.</p> <p> <b>Species included.</b> 7 valid species from the West Nearctic (DeWalt <i>et al.</i> 2014); 6 of these examined (see Appendix 1).</p> <p> <b>Remarks.</b> Despite the seemingly obvious differences among the males of the species, males share similar developed epiproct structures. An exception is <i>B. milami</i> (Nebeker & Gaufin, 1967) that has much more divided Ep-scl than other members of the genus. Nevertheless, its epiproct and the entire terminalia share the other features distinctive for the genus. Lacking process on Tg 9 of the type species <i>B. gregsoni</i> (Ricker, 1965) can be regarded as a secondary loss, because of the presence of a setose hump instead of a process.</p>Published as part of <i>Murányi, Dávid, Gamboa, Maribet & Orci, Kirill Márk, 2014, Zwicknia gen. n., a new genus for the Capnia bifrons species group, with descriptions of three new species based on morphology, drumming signals and molecular genetics, and a synopsis of the West Palaearctic and Nearctic genera of Capniidae (Plecoptera), pp. 1-82 in Zootaxa 3812 (1)</i> on page 15, DOI: 10.11646/zootaxa.3812.1.1, <a href="http://zenodo.org/record/4919079">http://zenodo.org/record/4919079</a>
A Darwinian Ricker Equation
No full textThe classic Ricker equation xt + 1= bxtexp (- cxt) has positive equilibria for b&gt; 1 that destabilize when b&gt; e2 after which its asymptotic dynamics are oscillatory and complex. We study an evolutionary version of the Ricker equation in which coefficients depend on a phenotypic trait subject to Darwinian evolution. We are interested in the question of whether evolution will select against or will promote complex dynamics. Toward this end, we study the existence and stability of its positive equilibria and focus on equilibrium destabilization as an indicator of the onset of complex dynamics. We find that the answer relies crucially on the speed of evolution and on how the intra-specific competition coefficient c depends on the evolving trait. In the case of a hierarchical dependence, equilibrium destabilization generally occurs after e2 when the speed of evolution is sufficiently slow (in which case we say evolution selects against complex dynamics). When evolution proceeds at a faster pace, destabilization can occur before e2 (in which case we say evolution promotes complex dynamics) provided the competition coefficient is highly sensitive to changes in the trait v. We also show that destabilization does not always result in a period doubling bifurcation, as in the non-evolutionary Ricker equation, but under certain circumstances can result in a Neimark-Sacker bifurcation. © 2020, Springer Nature Switzerland AG.12 month embargo; first published online 5 January 2021This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
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