Eigenvalue Spacings and Dynamical Upper Bounds for Discrete One-Dimensional Schroedinger Operators

We prove dynamical upper bounds for discrete one-dimensional Schroedinger operators in terms of various spacing properties of the eigenvalues of finite volume approximations. We demonstrate the applicability of our approach by a study of the Fibonacci Hamiltonian

Do sleep difficulties exacerbate deficits in sustained attention following traumatic brain injury?

Sustained attention has been shown to be vulnerable following traumatic brain injury (TBI). Sleep restriction and disturbances have been shown to negatively affect sustained attention. Sleep disorders are common but under-diagnosed after TBI. Thus, it seems possible that sleep disturbances may exacerbate neuropsychological deficits for a proportion of individuals who have sustained a TBI. The aim of this prospective study was to examine whether poor sleepers post-TBI had poorer sustained and general attentional functioning than good sleepers post-TBI. Retrospective subjective, prospective subjective, and objective measures were used to assess participants’ sleep. The results showed that the poor sleep group had significantly poorer sustained attention ability than the good sleep group. The differences on other measures of attention were not significant. This study supports the use of measures that capture specific components of attention rather than global measures of attention, and highlights the importance of assessing and treating sleep problems in brain injury rehabilitation

Coywolf, Canis latrans × lycaon, Pack Density Doubles Following the Death of a Resident Territorial Male

We studied a subset of four radio-collared individuals that were a part of a larger study documenting Coywolf (Canis latrans × lycaon; Eastern Coyote) ecology in an urbanized landscape (Cape Cod, Massachusetts), and report on the territory of a typical sized pack that was subdivided roughly in half following the death of the breeding male from the original ("Centerville") pack. The original residents lived in a winter pack size (i.e., after pup/juvenile dispersal) of three or four individuals in a 19.66 km2 territory and a density of 0.15-0.20 individuals/km2, as determined by radio-tracking and direct observations, with their territory bordering that of other monitored packs. Following the death of the breeding male, two other radio-collared Coywolves (a young male from the original Centerville pack and a young female from a bordering pack) shifted their respective territories to overlap the majority of the original Centerville pack's territory. These two groups were the same size as the original pack (three or four individuals each) but occupied smaller territories (5.28 km2 and 12.70 km2) within the previous pack's territory. The combined density for the two new packs was estimated at 0.33-0.45 individuals/km2 or 2.2 times greater than the former pack's density and was 2.5 times (0.38-0.50 individuals/km2) greater when accounting for the slight (12%) overlap between the territories of the two new packs. Our results suggest that local Coyote/Coywolf density (i.e., at the pack level) may increase following the death of the breeding male of a given pack, probably because of the reduced (or lack of) protection of territorial boundaries. This finding has particular relevance to Coyote/Coywolf management programs aimed at reducing local densities via removal of individuals from these populations. Further implications exist for enriching our understanding of the trophic dynamics of urbanized habitats

Numerical simulation of pressure response in partially completed oil wells.

Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002.This work is concerned with the application of finite difference simulation to modelling the pressure response in partially penetrating oil wells. This has relevance to the oil and hydrology industries where pressure behaviour is used to infer the nature of aquifer or reservoir properties, particularly permeability. In the case of partially penetrating wells, the pressure response carries information regarding the magnitude of permeability in the vertical direction, a parameter that can be difficult to measure by other means and one that has a direct influence on both the total volumes of oil that can be recovered and on the rate of recovery. The derivation of the non-linear differential equations that form the basis for multiphase fluid flow in porous media is reviewed and it is shown how they can be converted into a set of finite difference equations. Techniques used to solve these equations are explained, with particular emphasis on the approach followed by the commercial simulation package used in this study. This involves use of Newton's method to linearize the equations followed by application of a pre-conditioned successive minimization technique to solve the resulting linear equations. Finite difference simulation is applied to a hypothetical problem of solving pressure response in a partially penetrating well in an homogenous but anisotropic medium and the results compared with those from analytical solutions. Differences between the results are resolved, demonstrating that the required level of accuracy can be achieved through selective use of sufficiently small grid blocks and time-steps. Residual discrepancies with some of the analytical methods can be traced to differences in the boundary conditions used in their derivation. The simulation method is applied to matching a complex real-life well test with vertical and lateral variation in properties (including fluid saturation). An accurate match can be achieved through judicious adjustment of the problem parameters with the proviso that the vertical permeability needs to be high. This suggests that the recovery mechanism in the oil field concerned can be expected to be highly efficient, something that has recently been confirmed by production results

Numerical simulation of pressure response in partially completed oil wells.

Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002.This work is concerned with the application of finite difference simulation to modelling the pressure response in partially penetrating oil wells. This has relevance to the oil and hydrology industries where pressure behaviour is used to infer the nature of aquifer or reservoir properties, particularly permeability. In the case of partially penetrating wells, the pressure response carries information regarding the magnitude of permeability in the vertical direction, a parameter that can be difficult to measure by other means and one that has a direct influence on both the total volumes of oil that can be recovered and on the rate of recovery. The derivation of the non-linear differential equations that form the basis for multiphase fluid flow in porous media is reviewed and it is shown how they can be converted into a set of finite difference equations. Techniques used to solve these equations are explained, with particular emphasis on the approach followed by the commercial simulation package used in this study. This involves use of Newton's method to linearize the equations followed by application of a pre-conditioned successive minimization technique to solve the resulting linear equations. Finite difference simulation is applied to a hypothetical problem of solving pressure response in a partially penetrating well in an homogenous but anisotropic medium and the results compared with those from analytical solutions. Differences between the results are resolved, demonstrating that the required level of accuracy can be achieved through selective use of sufficiently small grid blocks and time-steps. Residual discrepancies with some of the analytical methods can be traced to differences in the boundary conditions used in their derivation. The simulation method is applied to matching a complex real-life well test with vertical and lateral variation in properties (including fluid saturation). An accurate match can be achieved through judicious adjustment of the problem parameters with the proviso that the vertical permeability needs to be high. This suggests that the recovery mechanism in the oil field concerned can be expected to be highly efficient, something that has recently been confirmed by production results

An Ethogram Developed on Captive Eastern Coyotes Canis latrans

We studied capture Eastern Coyotes (Canis latrans) from 27-585 days of age and compiled an ethogram on them. A total of 72247 15-sec samples were taken, amounting to 301 h of field time varying between 59.4–61.3 h per Coyote. A total of 540 behavioral patterns was observed amongst the 16 behaviour categories ranging from 9 (miscellaneous) to 72 (explore/investigate) action patterns per parent category. The 16 parent categories that we believed best described and appropriately sorted the behavioural actions were resting, sitting, sitting1, sitting2, standing, traveling, explore/investigating, hunting, feeding, infantile, greeting, self play, play initiating, playing, agonistic, and miscellaneous. Exploring accounted for >31% of all of the behaviours observed with resting and sitting (combined), standing, traveling, and play as categories decreasing in order of most to least frequent. Despite some omissions in our ethogram and drift associated with its ongoing development, we believe that the large amount of data collected made it rigorous enough to be a useful guide for the species. We argue that although future research will no doubt add to and/or modify components of it, its ease of use in the field (in captivity or in the wild) and it being the first complete ethogram described for the species, make it a useful tool for future researchers

Livestock in diverse cropping systems improve weed management and sustain yields whilst reducing inputs

<p>Dataset used for the article: </p> <p>MacLaren, C.; Storkey, J.; Strauss, J.; Swanepoel, P.; and Dehnen-Schmutz, K. (2018). Livestock in diverse cropping systems improve weed management and sustain yields whilst reducing inputs. <em>Journal of Applied Ecology.</em></p> <p> </p