179 research outputs found

    A family of non-cocycle conjugate E_0-semigroups obtained from boundary weight doubles

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    We have seen that if \phi: M_n(\C) \rightarrow M_n(\C) is a unital q-positive map and \nu is a type II Powers weight, then the boundary weight double (\phi, \nu) induces a unique (up to conjugacy) type II_0 E_0-semigroup. Let \phi: M_n(\C) \rightarrow M_n(\C) and \psi: M_{n'}(\C) \rightarrow M_{n'}(\C) be unital rank one q-positive maps, so for some states \rho \in M_n(\C)^* and \rho' \in M_{n'}(\C)^*, we have \phi(A)=\rho(A)I_n and \psi(D) = \rho'(D)I_{n'} for all A \in M_n(\C) and D \in M_{n'}(\C). We find that if \nu and \eta are arbitrary type II Powers weights, then (\phi, \nu) and (\psi, \eta) induce non-cocycle conjugate E_0-semigroups if \rho and \rho' have different eigenvalue lists. We then completely classify the q-corners and hyper maximal q-corners from \phi to \psi, obtaining the following result: If \nu is a type II Powers weight of the form \nu(\sqrt{I - \Lambda(1)} B \sqrt{I - \Lambda(1)})=(f,Bf), then the E_0-semigroups induced by (\phi,\nu) and (\psi, \nu) are cocycle conjugate if and only if n=n' and \phi and \psi are conjugate.Comment: 20 page

    IMPACT: The Journal of the Center for Interdisciplinary Teaching and Learning. Volume 8, Issue 1, Winter 2019

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    IMPACT: The Journal of the Center for Interdisciplinary Teaching & Learning is a peer-reviewed, biannual online journal that publishes scholarly and creative non-fiction essays about the theory, practice and assessment of interdisciplinary education. Impact is produced by the Center for Interdisciplinary Teaching & Learning at the College of General Studies, Boston University (www.bu.edu/cgs/citl).In this issue of Impact you will find a humanities scholar deeply engaged with the arcing out of a new territory: the interdisciplinary study of the Grateful Dead. Impact’s own Christopher Coffman’s review essay should be required reading for scholars of popular music, performance studies and history. His review also serves as an important reference for those who aspire to teach a course on the Grateful Dead, as well as for those who wish to write review essays. In this issue we also hear from those who are engaged in teaching people who are incarcerated. Importantly, Stephanie Cage’s essay looks to incarcerated people themselves to find out what they think about prison education. Peter Wakefield encourages us to see The Great Gatsby anew, in particular in the context of American racism and White supremacy. Wakefield’s essay is important too because it had its genesis in Writing, the State, and the Rise of Neo-Nationalism: Historical Contexts and Contemporary Concerns, a conference sponsored by the Center for Interdisciplinary Teaching & Learning

    Ultrabroadband Nonlinear Optics in Nanophotonic Periodically Poled Lithium Niobate Waveguides

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    Quasi-phasematched interactions in waveguides with quadratic nonlinearities enable highly efficient nonlinear frequency conversion. In this article, we demonstrate the first generation of devices that combine the dispersion-engineering available in nanophotonic waveguides with quasi-phasematched nonlinear interactions available in periodically poled lithium niobate (PPLN). This combination enables quasi-static interactions of femtosecond pulses, reducing the pulse energy requirements by several orders of magnitude, from picojoules to femtojoules. We experimentally demonstrate two effects associated with second harmonic generation. First, we observe efficient quasi-phasematched second harmonic generation with <100 fJ of pulse energy. Second, in the limit of strong phase-mismatch, we observe spectral broadening of both harmonics with as little as 2-pJ of pulse energy. These results lay a foundation for a new class of nonlinear devices, in which co-engineering of dispersion with quasi-phasematching enables efficient nonlinear optics at the femtojoule level

    Looking age-appropriate while growing old gracefully: A qualitative study of ageing and body image among older adults

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    © SAGE Publications. Body dissatisfaction can be significantly detrimental to wellbeing. Little is known about older adults' body image, despite the fact that ageing causes unique bodily changes and that sociocultural pressures to resist these changes abound. We conducted six focus groups with a UK community sample of White British and South Asian older adults aged 65-92 years. Thematic analysis highlighted four themes: appearance indicates capability and identity; physical ability trumps appearance; felt pressures to age 'gracefully' while resisting appearance changes; and gender and cultural differences. These findings suggest that older adults' body image can have important implications for their wellbeing and merits researchers' attention

    Solute and sediment export from Amazon forest and soybean headwater streams

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    Author Posting. © Ecological Society of America, 2016. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 27 (2017): 193–207, doi:10.1002/eap.1428.Intensive cropland agriculture commonly increases streamwater solute concentrations and export from small watersheds. In recent decades, the lowland tropics have become the world's largest and most important region of cropland expansion. Although the effects of intensive cropland agriculture on streamwater chemistry and watershed export have been widely studied in temperate regions, their effects in tropical regions are poorly understood. We sampled seven headwater streams draining watersheds in forest (n = 3) or soybeans (n = 4) to examine the effects of soybean cropping on stream solute concentrations and watershed export in a region of rapid soybean expansion in the Brazilian state of Mato Grosso. We measured stream flows and concentrations of NO3−, PO43−, SO42−, Cl−, NH4+, Ca2+, Mg2+, Na+, K+, Al3+, Fe3+, and dissolved organic carbon (DOC) biweekly to monthly to determine solute export. We also measured stormflows and stormflow solute concentrations in a subset of watersheds (two forest, two soybean) during two/three storms, and solutes and δ18O in groundwater, rainwater, and throughfall to characterize watershed flowpaths. Concentrations of all solutes except K+ varied seasonally in streamwater, but only Fe3+ concentrations differed between land uses. The highest streamwater and rainwater solute concentrations occurred during the peak season of wildfires in Mato Grosso, suggesting that regional changes in atmospheric composition and deposition influence seasonal stream solute concentrations. Despite no concentration differences between forest and soybean land uses, annual export of NH4+, PO43−, Ca2+, Fe3+, Na+, SO42−, DOC, and TSS were significantly higher from soybean than forest watersheds (5.6-fold mean increase). This increase largely reflected a 4.3-fold increase in water export from soybean watersheds. Despite this increase, total solute export per unit watershed area (i.e., yield) remained low for all watersheds (<1 kg NO3− N·ha−1·yr−1, <2.1 kg NH4+-N·ha−1·yr−1, <0.2 kg PO43−-P·ha−1·yr−1, <1.5 kg Ca2+·ha−1·yr−1). Responses of both streamflows and solute concentrations to crop agriculture appear to be controlled by high soil hydraulic conductivity, groundwater-dominated hydrologic flowpaths on deep soils, and the absence of nitrogen fertilization. To date, these factors have buffered streams from the large increases in solute concentrations that often accompany intensive croplands in other locations.NSF Grant Numbers: DEB-0640661, DEB-0949370; Fundação de Amparo á Pesquisa do Estado de São Paulo Grant Number: FAPESP 03/13172-2; Watson Graduate Student Fellowship; Center for Latin American and Caribbean Studies at Brown Universit
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