An anti-symmetric exclusion process for two particles on an infinite 1D lattice

A system of two biased, mutually exclusive random walkers on an infinite 1D lattice is studied whereby the intrinsic bias of one particle is equal and opposite to that of the other. The propogator for this system is solved exactly and expressions for the mean displacement and mean square displacement (MSD) are found. Depending on the nature of the intrinsic bias, the system's behaviour displays two regimes, characterised by (i) the particles moving towards each other and (ii) away from each other, both qualitatively different from the case of no bias. The continuous-space limit of the propogator is found and is shown to solve a Fokker-Planck equation for two biased, mutually exclusive Brownian particles with equal and opposite drift velocity.Comment: 19 pages, 5 figure

Activity, ranging, and habitat use by rodents in county Durham

The activity, home - ranging, and habitat use behaviour of two species of rodent, Apodemus sylvaticus (L.), the wood mouse, and Clethrionomys glareolus (Schreber), the bank vole, was investigated over a period of 14 weeks in two contrasting habitats. In farmland, woodmice utilised the rough vegetation around a crop of winter - sown wheat as a nest site, and probably as a food source, while the field surface also formed part of the home range of many animals studied. Weather conditions had little effect on the capture success of woodmice in farmland. Bank voles were caught exclusively in the boundaries around the edge of the field. Home range sizes and levels of activity of woodmice in woodland were lower than those of animals in farmland. Capture success of woodmice was not related to vegetative cover in woodland. Bankvoles were caught preferentially in scrub vegetation in all weather conditions, though weather was an important factor in capture success under other catagories of vegetation. The extent of intersexual range overlap of bankvoles in woodland fell significantly during the period of the study though no other changes were apparent for either species. Home range sizes and levels of activity were consistently lower than those reported in other studies

The Many Faces of the Hero in \u3ci\u3eThe Lord of the Rings\u3c/i\u3e

Guest of Honor address at Mythcon 22. Reviews various definitions and characteristics of the hero according to several folklorists and psychologists. Discusses Aragorn, Gandalf, Frodo, and Sam as heroes according to these definitions

Falsification as Contempt

The last twenty years have been witness first to an expansion and then to a retrenchment of constitutionally protected civil liberties. The exercise of the contempt power is an area in which constitutional limitations on modes of procedure are inapplicable so long as the power is used to preserve the judiciary.\u27 Contempts are either direct or constructive. Direct contempts are committed in the presence of the court whereas constructive contempts are committed outside the presence of the court. This distinction is significant in that direct contempts are punishable without a formulated charge, hearing or formal judgment of guilt. Constructive contempts are less summarily punishable. Both negative and positive conduct may constitute a contempt of court. Examples of negative direct contempts are failure to produce a prisoner at a trial or hearing and refusal of a witness to testify. Acts punishable as positive direct contempts include assaults on judges, jurors, attorneys, witnesses, and officers of the court; interferences with the trial jury by invitation to the room of defendant\u27s counsel to drink liquor or discussion of the case by a litigant in the presence of jurors who may try it; and perjury or false swearing by a witness in court or before a grand jury. The problems raised by the positive direct contempt of perjury or false swearing are the subject of this note

Emigration behavior of Clark's Nutcracker

Journal ArticleEruptive movements of the Clark's Nutcracker (Nucifraga columbiana) were observed during the late summer and fall of 1977, 1978 and 1979 in northern Utah and adjacent states. Over 2,000 emigrating nutcrackers were seen during these periods. Eruptions began in mid to late August, about the time nutcrackers began foraging on developing conifer cones, and continued until early October. Nearly all nutcrackers traveled in small, loose flocks (x = 10.1 individuals). During 1977-1978, most emigrating nutcrackers appeared to winter in p&on-juniper woodlands of Utah and adjacent states and no nutcrackers were reported outside their normal breeding range. A northward movement of nutcrackers, presumably the same population observed emigrating southward in fall 1977, was noted in summer 1978. Evidence for breeding of nutcrackers on their wintering areas is presented. A compartmental model summarizes current knowledge on the temporal and spatial aspects of nutcracker emigration

Aquilegia, Vol. 27 No. 2, March-June 2003: Newsletter of the Colorado Native Plant Society

https://epublications.regis.edu/aquilegia/1097/thumbnail.jp

Aquilegia, Vol. 27 No. 1, January-February 2003: Newsletter of the Colorado Native Plant Society

https://epublications.regis.edu/aquilegia/1096/thumbnail.jp

Pyrogenic fuels produced by savanna trees can engineer humid savannas

Natural fires ignited by lightning strikes following droughts frequently are posited as the ecological mechanism maintaining discontinuous tree cover and grass-dominated ground layers in savannas. Such fires, however, may not reliably maintain humid savannas. We propose that savanna trees producing pyrogenic shed leaves might engineer fire characteristics, affecting ground-layer plants in ways that maintain humid savannas. We explored our hypothesis in a high-rainfall, frequently burned pine savanna in which the dominant tree, longleaf pine (Pinus palustris), produces resinous needles that become highly flammable when shed and dried. We postulated that pyrogenic needles should have much greater influence on fire characteristics at ground level, and hence post-fire responses of dominant shrubs and grasses, than other abundant fine fuels (shed oak leaves and grass culms). We further reasoned that these effects should increase with amounts of needles. We managed site conditions that affect fuels (time since fire, dominant vegetation), manipulated amounts of needles in ground-layer plots, prescribed burned the plots, and measured fire characteristics at ground level. We also measured characteristics of ground-layer oaks and grasses before, then 2 and 8 months after fires. We tested our hypotheses regarding effects of pyrogenic pine fuels on fire characteristics and vegetation regrowth and explored direct and indirect effects of fuels on fire characteristics and vegetation using a structural equation model. Pine needles influenced fire characteristics, elevating maximum temperature increases, durations of heating above 60°C, and fine fuel consumption considerably above measurements when fuels only included other savanna plants. Presence of pine needles depressed post-fire numbers of oak stems and grass culms, especially in the interior of grass genets, as well as post-fire flowering of grasses. The structural equation model indicated strong direct and indirect pathways from pine needles to post-fire responses of oaks and grasses. The experimental field tests of hypotheses, bolstered by structural equation modeling, indicate pyrogenic fine fuels modify characteristics of prescribed fires at ground level, negatively affecting dominant ground-layer oaks and grasses. Frequent fires fueled by pyrogenic needles should maintain humid savannas and generate spatial pyrodiversity that affects composition and dynamics of pine savanna ground-layer vegetation