4,395 research outputs found

    Nonlinear Dynamics of Mountain Pine Beetle Populations: Discussion of Forestry Policy, a Survey of Existing Mathematical Models, and Code Base Demonstration

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    This article presents existing mathematical models associated with mountain pine beetle populations in lodgepole pine forests, whose reproductive cycle requires the destruction of colonized host trees, decreasing timber availability/quality, and providing fuel sources for wildfires. With the existence of a positive-feedback loop with environmental warming, the need for intervention and management is clear. However, the legislative responses to the focusing events from our 2000-2010 North American epidemics are characterized as under-leveraged. While the reasons for this are multifaceted, increasing the capacity of STEM-informed individuals to take part in quantitative modeling of the underlying ecosystem generates awareness and provides pathways connecting the ``how\u27\u27 of public land management to the ``what\u27\u27 and ``why\u27\u27 of policy creation. To this end, we survey existing mathematical models for the mountain pine beetle, ranging from a simple planar model to a chemotactic model involving pheromone/kairomone signaling between beetles and host trees. The latter can be localized to a host tree characterized by a nonlinear system of ordinary differential equations whose solution is reasonable to approximate numerically

    Nonlinear Scattering of a Bose-Einstein Condensate on a Rectangular Barrier

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    We consider the nonlinear scattering and transmission of an atom laser, or Bose-Einstein condensate (BEC) on a finite rectangular potential barrier. The nonlinearity inherent in this problem leads to several new physical features beyond the well-known picture from single-particle quantum mechanics. We find numerical evidence for a denumerably infinite string of bifurcations in the transmission resonances as a function of nonlinearity and chemical potential, when the potential barrier is wide compared to the wavelength of oscillations in the condensate. Near the bifurcations, we observe extended regions of near-perfect resonance, in which the barrier is effectively invisible to the BEC. Unlike in the linear case, it is mainly the barrier width, not the height, that controls the transmission behavior. We show that the potential barrier can be used to create and localize a dark soliton or dark soliton train from a phonon-like standing wave.Comment: 15 pages, 15 figures, new version includes clarification of definition of transmission coefficient in general nonlinear vs. linear cas

    Surgical Treatment of Induced Peri‚ÄźImplantitis in the Micro Pig: Clinical and Histological Analysis

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141550/1/jper0984.pd

    Spatio-temporal dynamics of Marbled Murrelet hotspots during nesting in nearshore waters along the Washington to California coast

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    The Marbled Murrelet, Brachyramphus marmoratus, is a federally listed alcid that forages in nearshore waters of the Pacific Northwest, and nests in adjacent older-forest conifers within 40-80 km of shore. To estimate abundance and distribution of murrelets, we conduct at-sea surveys from May to July each year, starting in 2000 and continuing to present. We record numbers of individuals sighted by using distance-based transects and compute annual estimates of density after adjusting for detectability. At-sea transects are subdivided into 5-km segments, and we summarized mean and variance of density at each segment in Puget Sound and along the coast from the Canadian border South to San Francisco Bay. We used a boosted regression tree analysis to investigate the contributions of marine and terrestrial attributes on murrelet abundance in each segment. We observed that terrestrial attributes, especially the amount and pattern of suitable nesting habitat in proximity to each segment, made the strongest contribution, but that marine attributes also helped explain variation in murrelet abundance. Hotspots of murrelet abundance therefore reflect not only suitable marine foraging habitat but proximity of suitable inland nesting habitat

    A cluster randomized controlled trial of a theory-based sleep hygiene intervention for adolescents

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    Study Objectives To use theory to design and evaluate an intervention to promote sleep hygiene and health among adolescents. Methods The Theory of Planned Behavior (TPB) and the Health Action Process Approach (HAPA) were used to develop an intervention, which was then evaluated in a cluster randomized trial. Participants were high school students (N = 2,841, M age = 15.12, SD = 1.50). Adolescents in the intervention group received four face-to-face sessions providing behavior change techniques targeting the theoretical determinants of sleep hygiene. Adolescents in the control group only received educational material at the end of the study. The primary outcome was sleep hygiene measured at 1 and 6 months postintervention. A number of secondary outcomes were also measured, including beliefs about sleep, self-regulatory processes, and outcomes related to health and wellbeing. Results Sleep hygiene was improved in the intervention group when compared with the control group at both follow-up points (coefficients = 0.16 and 0.19, 95% CIs = 0.12‚Äď0.20 and 0.15‚Äď0.23 at 1 and 6 months, respectively, for scores on the Adolescent Sleep Hygiene Scale), as were psychosocial and general aspects of health. Mediation analyses suggested that beliefs about sleep hygiene as specified by the TPB, along with self-regulatory processes from HAPA, both mediated the effect of the intervention on outcomes. In turn, the effects of the intervention on sleep hygiene mediated its impact on general health. Conclusions Healthcare practitioners might consider intervention programs based on the TPB and the HAPA to improve sleep among adolescents

    Galactic-Centre Gamma Rays in CMSSM Dark Matter Scenarios

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    We study the production of gamma rays via LSP annihilations in the core of the Galaxy as a possible experimental signature of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which supersymmetry-breaking parameters are assumed to be universal at the GUT scale, assuming also that the LSP is the lightest neutralino chi. The part of the CMSSM parameter space that is compatible with the measured astrophysical density of cold dark matter is known to include a stau_1 - chi coannihilation strip, a focus-point strip where chi has an enhanced Higgsino component, and a funnel at large tanb where the annihilation rate is enhanced by the poles of nearby heavy MSSM Higgs bosons, A/H. We calculate the total annihilation rates, the fractions of annihilations into different Standard Model final states and the resulting fluxes of gamma rays for CMSSM scenarios along these strips. We observe that typical annihilation rates are much smaller in the coannihilation strip for tanb = 10 than along the focus-point strip or for tanb = 55, and that the annihilation branching ratios differ greatly between the different dark matter strips. Whereas the current Fermi-LAT data are not sensitive to any of the CMSSM scenarios studied, and the calculated gamma-ray fluxes are probably unobservably low along the coannihilation strip for tanb = 10, we find that substantial portions of the focus-point strips and rapid-annihilation funnel regions could be pressured by several more years of Fermi-LAT data, if understanding of the astrophysical background and/or systematic uncertainties can be improved in parallel.Comment: 33 pages, 12 figures, comments and references added, version to appear in JCA
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