6,299 research outputs found

    New Ways to Make People Save: A Social Marketing Approach

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    In this study, we use a social marketing approach to develop a planning aid to help new employees at a not-for-profit institution contribute to supplementary pensions. We employed different methods, such as surveys, focus groups and in-depth interviews, to "listen" to employees' needs and difficulties with saving. Moreover, we targeted specific groups that were less likely to save and contribute to supplementary pensions, such as women and low-income employees. The program we developed is not only effective but also inexpensive. While this program was implemented at a single institution, it is suitable to be applied to a variety of employers and demographic groups.

    Statistical Distributions and q-Analogues of k-Fibonacci Numbers

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    Abstract We study q-analogues of k-Fibonacci numbers that arise from weighted tilings of an n × 1 board with tiles of length at most k. The weights on our tilings arise naturally out of distributions of permutations statistics and set partitions statistics. We use these q-analogues to produce q-analogues of identities involving k-Fibonacci numbers. This is a natural extension of results of the first author and Sagan on set partitions and the first author and Mathisen on permutations. In this paper we give general q-analogues of k-Fibonacci identities for arbitrary weights that depend only on lengths and locations of tiles. We then determine weights for specific permutation or set partition statistics and use these specific weights and the general identities to produce specific identities

    The Magnetohydrodynamic Kelvin-Helmholtz Instability: A Three-Dimensional Study of Nonlinear Evolution

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    We investigate through high resolution 3D simulations the nonlinear evolution of compressible magnetohydrodynamic flows subject to the Kelvin-Helmholtz instability. We confirm in 3D flows the conclusion from our 2D work that even apparently weak magnetic fields embedded in Kelvin-Helmholtz unstable plasma flows can be fundamentally important to nonlinear evolution of the instability. In fact, that statement is strengthened in 3D by this work, because it shows how field line bundles can be stretched and twisted in 3D as the quasi-2D Cat's Eye vortex forms out of the hydrodynamical motions. In our simulations twisting of the field may increase the maximum field strength by more than a factor of two over the 2D effect. If, by these developments, the Alfv\'en Mach number of flows around the Cat's Eye drops to unity or less, our simulations suggest magnetic stresses will eventually destroy the Cat's Eye and cause the plasma flow to self-organize into a relatively smooth and apparently stable flow that retains memory of the original shear. For our flow configurations the regime in 3D for such reorganization is 4â‰ČMAxâ‰Č504\lesssim M_{Ax} \lesssim 50, expressed in terms of the Alfv\'en Mach number of the original velocity transition and the initial Alfv\'en speed projected to the flow plan. For weaker fields the instability remains essentially hydrodynamic in early stages, and the Cat's Eye is destroyed by the hydrodynamic secondary instabilities of a 3D nature. Then, the flows evolve into chaotic structures that approach decaying isotropic turbulence. In this stage, there is considerable enhancement to the magnetic energy due to stretching, twisting, and turbulent amplification, which is retained long afterwards. The magnetic energy eventually catches up to the kinetic energy, and the nature of flows become magnetohydrodynamic.Comment: 11 pages, 12 figures in degraded jpg format (2 in color), paper with original quality figures available via ftp at ftp://ftp.msi.umn.edu/pub/users/twj/mhdkh3dd.ps.gz or ftp://canopus.chungnam.ac.kr/ryu/mhdkh3dd.ps.gz, to appear in The Astrophysical Journa

    Striation and convection in penumbral filaments

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    Observations with the 1-m Swedish Solar Telescope of the flows seen in penumbral filaments are presented. Time sequences of bright filaments show overturning motions strikingly similar to those seen along the walls of small isolated structures in the active regions. The filaments show outward propagating striations with inclination angles suggesting that they are aligned with the local magnetic field. We interpret it as the equivalent of the striations seen in the walls of small isolated magnetic structures. Their origin is then a corrugation of the boundary between an overturning convective flow inside the filament and the magnetic field wrapping around it. The outward propagation is a combination of a pattern motion due to the downflow observed along the sides of bright filaments, and the Evershed flow. The observed short wavelength of the striation argues against the existence of a dynamically significant horizontal field inside the bright filaments. Its intensity contrast is explained by the same physical effect that causes the dark cores of filaments, light bridges and `canals'. In this way striation represents an important clue to the physics of penumbral structure and its relation with other magnetic structures on the solar surface. We put this in perspective with results from the recent 3-D radiative hydrodynamic simulations.Comment: Accepted for publication in A&

    Cross-Transfer Effects on Muscle Strength, Size, and Quality following Unilateral Blood Flow Restriction Training

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    Unilateral resistance training (RT) has been shown to induce contralateral strength improvements in the untrained homologous muscle. Notably, low-load blood flow restriction (BFR) RT has shown superior increases in muscle strength and hypertrophy compared to low-load non-BFR RT. Previous literature has also reported that BFR RT has systemic cross-transfer effects of strength on other active skeletal muscles compared to low-load non-BFR RT. PURPOSE: Therefore, the purpose was to examine the cross-transfer effects of 4 weeks of unilateral BFR dorsiflexion RT on muscle strength, hypertrophy, and muscle quality. METHODS: Fourteen untrained participants were randomized into two groups: (BFR; n=8) (177.6 ± 4.1 cm, 84.8 ± 15.1 kg, 21.3 ± 1 years) or control (non-BFR; n=6) (173.2 ± 7.5 cm, 77.9 ± 10.3 kg, 23 ± 2.6 years). Subjects completed 4 weeks (8 sessions) of unilateral isokinetic dorsiflexion RT at 30% of their daily peak torque at a velocity of 60°/s. Isokinetic peak torque, echo intensity (EI), and muscle cross-sectional area (mCSA) were taken bilaterally pre and post RT. Statistical analyses included 3 separate 3-way mixed factorial ANOVAs (Group [BFR, non-BFR] x Time [pre, post] x Leg [right, left]). RESULTS: For isokinetic strength, there were no significant interactions or main effects (p\u3e.05). For EI, there were no significant interactions (p\u3e.05); however, when collapsed across time and leg, there was a significant main effect for group (p=.017; BFR (91.7 ± 1.6 vs. non-BFR (84.8 ± 1.9); mean ± SE). Furthermore, there was no significant interaction for mCSA (p\u3e.05), but there was a significant main effect for time (

    The jellification of north temperate lakes.

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    Calcium (Ca) concentrations are decreasing in softwater lakes across eastern North America and western Europe. Using long-term contemporary and palaeo-environmental field data, we show that this is precipitating a dramatic change in Canadian lakes: the replacement of previously dominant pelagic herbivores (Ca-rich Daphnia species) by Holopedium glacialis, a jelly-clad, Ca-poor competitor. In some lakes, this transformation is being facilitated by increases in macro-invertebrate predation, both from native (Chaoborus spp.) and introduced (Bythotrephes longimanus) zooplanktivores, to which Holopedium, with its jelly coat, is relatively invulnerable. Greater representation by Holopedium within cladoceran zooplankton communities will reduce nutrient transfer through food webs, given their lower phosphorus content relative to daphniids, and greater absolute abundances may pose long-term problems to water users. The dominance of jelly-clad zooplankton will likely persist while lakewater Ca levels remain low.This work was primarily supported by grants from the Natural Sciences and Engineering Research Council of Canada and funding from the Ontario Ministry of the Environment.This is the accepted manuscript. The final version is available at http://rspb.royalsocietypublishing.org/content/282/1798/20142449
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