Ion Concentration Dynamics as a Mechanism for Neuronal Bursting

We describe a simple conductance-based model neuron that includes intra- and extra-cellular ion concentration dynamics and show that this model exhibits periodic bursting. The bursting arises as the fast spiking behavior of the neuron is modulated by the slow oscillatory behavior in the ion concentration variables, and vice versa. By separating these time scales and studying the bifurcation structure of the neuron, we catalog several qualitatively different bursting profiles that are strikingly similar to those seen in experimental preparations. Our work suggests that ion concentration dynamics may play an important role in modulating neuronal excitability in real biological systems.Comment: The most recent version now contains citation information: Journal of Biological Physics 37, 361-373 (2011

Some aspects of grazing ecosystems : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University

The conversion of plant material to meat and milk by ruminants is one of the main ways in which the demand for energy and more especially protein for human consumption is met. While research in soil, plant and animal sciences is all more or less relevant to this conversion process a considerable amount of the agricultural research effort in Australasia has been directed more specifically to the grazing situation. Much of this work has been concerned with specific components of the grazing ecosystem such as the factors limiting pasture production (Brougham 1968), the definition of those plant factors contributing to nutritive value (Butler et al. 1968; Minson 1968), animal nutrition (Moir 1968) and pasture establishment (Swain 1968). While such research is basic to the understanding of the processes operating within a grazing system it must be complimented by a recognition of the interactions which exist within such grazing ecosystems and the way in which such interactions can affect interpretation of evidence from isolated parts of the grazing ecosystem. For example, the adoption of defoliation systems based on evidence from experiments of which grazing animals are not an integral part is often difficult to reconcile with the reality of having to graze a more or less fixed number of animals on a fixed area of land over a long period of time (Campbell 1969). In an effort to take account of the interactions which may invalidate conclusions based on evidence from component parts of the grazing ecosystem, the "whole-farm" approach to experimentation has been evolved. However in many cases such experiments have been designed to study the importance of different management factors on animal production from a given area of land (McMeekan 1961; Willoughby 1968) rather than to study the inter-relationships occurring between the soil, plant and animal components of the ecosystem. For example there is little information available on these inter-relationships from over 150 experiments of this kind carried out in Australia, evaluation of treatments having been carried out almost entirely in terms of animal production (Allden 1968)

The detection and interpretation of long-term changes in ozone from space

Long-term measurements of backscattered ultraviolet radiances, now being acquired by orbiting monochromators, will provide the basis for seeking trends in atmospheric ozone. The unambiguous detection of ozone trends on decadal time scales demands a data set that is essentially free of instrument drifts. Periodic flights of an ultraviolet monochromator on the space shuttle will provide an independent means of evaluating the long-term stability of identical instruments operating on free-flying satellites. A successful calibration of the free-flying sensors using the shuttle instrument places strict demands on calibration repeatability from one flight to the next. In addition, spatial and temporal variability in cloud cover could pose further complications in carrying out these in-flight calibrations

The Pitfalls of Constructing Yield Maps

Crop Production/Industries,

In-Suit Doppler Technology Assessment

The objective of this program was to perform a technology assessment survey of non-invasive air embolism detection utilizing Doppler ultrasound methodologies. The primary application of this technology will be a continuous monitor for astronauts while performing extravehicular activities (EVA's). The technology assessment was to include: (1) development of a full understanding of all relevant background research; and (2) a survey of the medical ultrasound marketplace for expertise, information, and technical capability relevant to this development. Upon completion of the assessment, LSR was to provide an overview of technological approaches and R&D/manufacturing organizations

European Springtails Orchesella cincta (L.) and O. villosa (L.) (Collembola: Entomobryidae): Vagabond Species of the Nearctic Region

North American specimens of the European invasive springtail Orchesella cincta (L.) were compared to several published European haplotypes in a phylogenetic framework using likelihood methods based on a portion of cytochrome oxidase II (cox2). Our analyses provide direct evidence of at least two distinct introductions of this invasive to North America from different regions of Europe. Additional introduction events cannot be ruled out because detection is limited by extremely low sequence divergence among populations inhabiting different regions of the continent. Orchesella villosa (L.), another invasive from Europe, is another candidate for multiple introductions. Herein we include the cox2 sequence from single specimens of O. villosa from Maine and Oregon. Although these two specimens are identical in sequence, they differ from a published sequence from a European specimen by 15%, indicating significant undocumented genetic variation in the natal range of O. villosa. Additional sampling of Nearctic populations of O. villosa might reveal the same situation reported herein for O. cincta

Adverse Consequences to Assisting Victims of Campus Violence: Initial Investigations Among College Students

Despite growing interest in the use of bystander education programs to address the problems of sexual and relationship violence on college campuses, little knowledge exists on adverse consequences experienced by students intervening as a bystander. The current study examined the prevalence and correlates of adverse consequences of bystander intervention in two samples of first-year college students. In Study 1, 281 students completed a measure of negative consequences experienced when acting as a bystander to help someone at risk of sexual assault, relationship abuse, or stalking. Efficacy for bystander behavior was also assessed. Approximately one third of the students (97/281) reported having tried to help someone who had been at risk of violence during the previous academic year. Of these, approximately 17% (16/97) reported experiencing a negative consequence from having tried to help. Experiencing negative consequences was associated with lower levels of bystander efficacy. In Study 2, conducted at a different university, 299 students completed measures of negative consequences resulting from intervening as a bystander and efficacy for bystander behavior. Students also participated in virtual-reality simulations that provided opportunities to intervene as a bystander. Again, approximately one third of the students (99/299) reported having tried to help someone at risk of violence. Of these, 20% (20/99) reported experiencing a negative consequence. Two of the adverse consequences (physically hurt, got into trouble) were negatively associated with bystander efficacy and observed effectiveness of bystander behavior in the virtual simulations. Results of exploratory analyses suggest that training in bystander intervention might reduce the likelihood of experiencing adverse consequences