Chutes and Ladders with Large Spinners

We prove a conjecture from a 2011 College Mathematics Journal article addressing the expected number of turns in a Chutes and Ladders game when the spinner range is close to the length of the board. While the original paper approached the question using linear algebra and the theory of Markov processes, our main method uses combinatorics and recursion

Allee Effects May Slow the Spread of Parasites in a Coastal Marine Ecosystem

Allee effects are thought to mediate the dynamics of population colonization, particularly for invasive species. However, Allee effects acting on parasites have rarely been considered in the analogous process of infectious disease establishment and spread. We studied the colonization of uninfected wild juvenile Pacific salmon populations by ectoparasitic salmon lice (Lepeophtheirus salmonis) over a 4-year period. In a data set of 68,376 fish, we observed 85 occurrences of precopular pair formation among 1,259 preadult female and 613 adult male lice. The probability of pair formation was dependent on the local abundance of lice, but this mate limitation is likely offset somewhat by mate-searching dispersal of males among host fish. A mathematical model of macroparasite population dynamics that incorporates the empirical results suggests a high likelihood of a demographic Allee effect, which can cause the colonizing parasite populations to die out. These results may provide the first empirical evidence for Allee effects in a macroparasite. Furthermore, the data give a rare detailed view of Allee effects in colonization dynamics and suggest that Allee effects may dampen the spread of parasites in a coastal marine ecosystem

Alien Registration- Connors, James B. (Portland, Cumberland County)

https://digitalmaine.com/alien_docs/25098/thumbnail.jp

How to Help Students Remember What You Have Taught

No matter how well university students do on quizzes and unit exams, the question always is: “How much will they remember later?” And if they don’t well on tests it may be that they either don’t know how to study, study the wrong information or try to study at the last minute. Using some basic methods of cumulative review faculty can help students learn how to study and remember what they have learned

High-resolution N-body Simulations of Galactic Cannibalism: The Magellanic Stream

Hierarchical clustering represents the favoured paradigm for galaxy formation throughout the Universe; due to its proximity, the Magellanic system offers one of the few opportunities for astrophysicists to decompose the full six-dimensional phase-space history of a satellite in the midst of being cannibalised by its host galaxy. The availability of improved observational data for the Magellanic Stream and parallel advances in computational power has led us to revisit the canonical tidal model describing the disruption of the Small Magellanic Cloud and the consequent formation of the Stream. We suggest improvements to the tidal model in light of these recent advances.Comment: 6 pages, 4 figures, LaTeX (gcdv.sty). Refereed contribution to the 5th Galactic Chemodynamics conference held in Swinburne, July 2003. Accepted for publication in PASA. Version with high resolution figures available at http://astronomy.swin.edu.au/staff/tconnors/publications.htm

Energetic proton spectra in the 11 June 1991 solar flare

We have studied a subset of the 11 June 1991 solar flare γ-ray data that we believe arise from soft proton or ion spectra. Using data from the COMPTEL instrument on the Compton Observatory we discuss the gamma-ray intensities at 2.223 MeV, 4–7 MeV, and 8–30 MeV in terms of the parent proton spectrum responsible for the emission

Interviews with the Apollo lunar surface astronauts in support of planning for EVA systems design

Focused interviews were conducted with the Apollo astronauts who landed on the moon. The purpose of these interviews was to help define extravehicular activity (EVA) system requirements for future lunar and planetary missions.RTOP 199-06-1

Development of a low-maintenance measurement approach to continuously estimate methane emissions: a case study

The chemical breakdown of organic matter in landfills represents a significant source of methane gas (CH4). Current estimates suggest that landfills are responsible for between 3% and 19% of global anthropogenic emissions. The net CH4 emissions resulting from biogeochemical processes and their modulation by microbes in landfills are poorly constrained by imprecise knowledge of environmental constraints. The uncertainty in absolute CH4 emissions from landfills is therefore considerable. This study investigates a new method to estimate the temporal variability of CH4 emissions using meteorological and CH4 concentration measurements downwind of a landfill site in Suffolk, UK from July to September 2014, taking advantage of the statistics that such a measurement approach offers versus shorter-term, but more complex and instantaneously accurate, flux snapshots. Methane emissions were calculated from CH4 concentrations measured 700 m from the perimeter of the landfill with observed concentrations ranging from background to 46.4 ppm. Using an atmospheric dispersion model, we estimate a mean emission flux of 709 μg m−2 s−1 over this period, with a maximum value of 6.21 mg m−2 s−1, reflecting the wide natural variability in biogeochemical and other environmental controls on net site emission. The emissions calculated suggest that meteorological conditions have an influence on the magnitude of CH4 emissions. We also investigate the factors responsible for the large variability observed in the estimated CH4 emissions, and suggest that the largest component arises from uncertainty in the spatial distribution of CH4 emissions within the landfill area. The results determined using the low-maintenance approach discussed in this paper suggest that a network of cheaper, less precise CH4 sensors could be used to measure a continuous CH4 emission time series from a landfill site, something that is not practical using far-field approaches such as tracer release methods. Even though there are limitations to the approach described here, this easy, low-maintenance, low-cost method could be used by landfill operators to estimate time-averaged CH4 emissions and their impact downwind by simultaneously monitoring plume advection and CH4 concentrations

Gamma ray measurements of the 1991 November 15 solar flare

The 1991 November 15 X1.5 flare was a well observed solar event. Comprehensive data from ground-based observatories and spacecraft provide the basis for a contextual interpretation of gamma-ray spectra from the Compton Gamma Ray Observatory (CGRO). In particular, spectral, spatial, and temporal data at several energies are necessary to understand the particle dynamics and the acceleration mechanism(s) within this flare. X-ray images, radio, Ca XIX data and magnetograms provide morphological information on the acceleration region [4,5], while gamma-ray spectral data provide information on the parent ion spectrum. Furthermore, time profiles in hard X-rays and gamma-rays provide valuable information on temporal characteristics of the energetic particles. We report the results of our analysis of the evolution of this flare as a function of energy (∼25 keV–2.5 MeV) and time. These results, together with other high energy data (e.g. from experiments on Yohkoh, Ulysses, and PVO) may assist in identifying and understanding the acceleration mechanism(s) taking place in this event

Differential herbivory on disk and ray flowers of gynomonoecious asters and goldenrods (Asteraceae)

The selective advantage of gynomonoecy, the sexual system wherein plants produce a mixture of female and bisexual flowers, is poorly understood. One hypothesis for the evolution of this system is that the absence of androecia from female flowers reduces herbivore damage to the gynoecia of these flowers. Here, we examined patterns of herbivore damage in 53 collections representing 25 species of asters and goldenrods from Massachusetts, USA. In these taxa flowers are crowded into compact capitula, with bisexual flowers occupying the centre and female flowers situated on the periphery. Damage to gynoecia of bisexual flowers was significantly greater than damage to gynoecia of female flowers overall, and in about half of the individual populations. We also compared damage to central and peripheral flowers in the heads of 16 collections of other Asteraceae that produce only bisexual flowers to see whether the location of flowers rather than their sex might determine the patterns of herbivory. In only one of these 16 collections did we find a significant difference in herbivory between flower positions. We conclude that herbivore damage is influenced by flower type in asters and goldenrods, a pattern consistent with a role for herbivory in the evolution and maintenance of gynomonoecy. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society