Lichen Trimlines in the Peace-Athabasca Delta: Variations in Flora, Form, and Disturbance Regime

Lichen trimlines are characteristic of aquatic systems where lichen-covered rocks border fluctuating water bodies. This study examined water-origin saxicolous lichen trimlines on acidic metacrystalline bedrock outcrops in the Peace-Athabasca Delta, northern Alberta, Canada. Twenty-seven species of saxicolous lichens were found in the vicinity of the trimlines. Species richness above the trimline (26 species) was almost twice that found below the trimline (14 species). Colonization lag time, differences in susceptibility to disturbance, and site influences on lichen establishment and survival might be involved in the absence of many species below trimlines. In frequently inundated areas, rock surfaces are dominated by the amphibious lichens Staurothele fissa and S. drummondii. The dominant lichen colonizer below trimlines was Physcia caesia. Other important colonizers below trimlines included Phaeophyscia sciastra and Physcia dubia, and on rocks fertilized by bird feces, Xanthoria elegans. A curious feature of the saxicolous flora was the presence of many calciphiles. Variations in trimline form and height and constituent species are related to the hydrologic and disturbance regime. Trimlines in perched basins tend to be near current water level, horizontal, and distinct, and indicate a relatively stable, infrequently flooded environment. Trimlines at open-drainage sites tend to be high above current water, wavy, and indistinct, and indicate a strongly-pulsed environment with frequent disturbances. Those at restricted-drainage basins are variable in form and height and disturbance regime

Estimating the Economic Value of Specific Characteristics Associated with Angus Bulls Sold at Auction

The genetic traits of a purebred bull convey the reproductive and economic value to buyers. This study examines and compares the value of actual production weights (birth, weaning, and yearling weight), production expected progeny differences (EPDs) (birth, weaning, milk, and yearling), and ultrasound EPDs (carcass quality predictors) for purebred Angus bulls sold at auction. One EPD, birth weight, was valued by buyers more than its corresponding actual weight, though both actual weights and EPDs significantly impact price. Predictors of carcass quality were important in determining price. Finally, several individual animal factors and sale characteristics were significant in determining price.Angus bulls, carcass characteristics, EPDs, marketing factors, production factors, Agribusiness, Agricultural and Food Policy, Agricultural Finance, Food Consumption/Nutrition/Food Safety, Livestock Production/Industries, Q10, Q12,

ESTIMATING THE ECONOMIC VALUES ASSOCIATED WITH EPDS FOR ANGUS BULLS AT AUCTION

The genetic traits that an Angus bull possesses convey the reproductive and economic value of the animal to potential buyers. This paper examines and draws comparisons between the value of actual production weights and production EPDs, while also establishing values for ultrasound EPDs. Results indicate that only one EPD, birth weight, was valued by buyers more than its corresponding actual weight, though actual weights and EPDs significantly impacted price. Ultrasound EPDs were also found to be significant, suggesting buyers of Angus bulls consider carcass information when purchasing bulls.Angus Bulls, Birth Weight, Carcass, EPDs, Hedonic Model, Livestock Production/Industries,

Congestion-gradient driven transport on complex networks

We present a study of transport on complex networks with routing based on local information. Particles hop from one node of the network to another according to a set of routing rules with different degrees of congestion awareness, ranging from random diffusion to rigid congestion-gradient driven flow. Each node can be either source or destination for particles and all nodes have the same routing capacity, which are features of ad-hoc wireless networks. It is shown that the transport capacity increases when a small amount of congestion awareness is present in the routing rules, and that it then decreases as the routing rules become too rigid when the flow becomes strictly congestion-gradient driven. Therefore, an optimum value of the congestion awareness exists in the routing rules. It is also shown that, in the limit of a large number of nodes, networks using routing based on local information jam at any nonzero load. Finally, we study the correlation between congestion at node level and a betweenness centrality measure.Comment: 11 pages, 8 figure

Optimal routing on complex networks

We present a novel heuristic algorithm for routing optimization on complex networks. Previously proposed routing optimization algorithms aim at avoiding or reducing link overload. Our algorithm balances traffic on a network by minimizing the maximum node betweenness with as little path lengthening as possible, thus being useful in cases when networks are jamming due to queuing overload. By using the resulting routing table, a network can sustain significantly higher traffic without jamming than in the case of traditional shortest path routing.Comment: 4 pages, 5 figure

Show Quality Quarter Horse Auctions: Price Determinants and Buy-Back Practices

This study estimates the price determinants of show quality quarter horses sold at auction. Several characteristics including genetic and physical traits, quality of pedigree, and performance record of the horse, as well as the horse's offspring, were found to significantly impact selling price. Sale order positively affected price and appears to be driven by buyers rather than intentional ordering of the horses. A common practice at horse auctions is for the seller to reject the final bid offered and buy back the horse. Model-predicted prices for these buy-back horses indicate they are not undervalued by the final bids, based on their characteristics.auction, equine, hedonic pricing, quarter horses, Demand and Price Analysis,

Longitudinal analyses of immune responses to Plasmodium falciparum derived peptides corresponding to novel blood stage antigens in coastal Kenya.

We have recently described 95 predicted alpha-helical coiled-coil peptides derived from putative Plasmodium falciparum erythrocytic stage proteins. Seventy peptides recognized with the highest level of prevalence by sera from three endemic areas were selected for further studies. In this study, we sequentially examined antibody responses to these synthetic peptides in two cohorts of children at risk of clinical malaria in Kilifi district in coastal Kenya, in order to characterize the level of peptide recognition by age, and the role of anti-peptide antibodies in protection from clinical malaria. Antibody levels from 268 children in the first cohort (Chonyi) were assayed against 70 peptides. Thirty-nine peptides were selected for further study in a second cohort (Junju). The rationale for the second cohort was to confirm those peptides identified as protective in the first cohort. The Junju cohort comprised of children aged 1-6 years old (inclusive). Children were actively followed up to identify episodes of febrile malaria in both cohorts. Of the 70 peptides examined, 32 showed significantly (p<0.05) increased antibody recognition in older children and 40 showed significantly increased antibody recognition in parasitaemic children. Ten peptides were associated with a significantly reduced odds ratio (OR) for an episode of clinical malaria in the first cohort of children and two of these peptides (LR146 and AS202.11) were associated with a significantly reduced OR in both cohorts. LR146 is derived from hypothetical protein PFB0145c in PlasmoDB. Previous work has identified this protein as a target of antibodies effective in antibody dependent cellular inhibition (ADCI). The current study substantiates further the potential of protein PFB0145c and also identifies protein PF11_0424 as another likely target of protective antibodies against P. falciparum malaria

Evidence for over-dispersion in the distribution of clinical malaria episodes in children.

BACKGROUND: It may be assumed that patterns of clinical malaria in children of similar age under the same level of exposure would follow a Poisson distribution with no over-dispersion. Longitudinal studies that have been conducted over many years suggest that some children may experience more episodes of clinical malaria than would be expected. The aim of this study was to identify this group of children and investigate possible causes for this increased susceptibility. METHODOLOGY AND PRINCIPAL FINDINGS: Using Poisson regression, we chose a group of children whom we designated as 'more susceptible' to malaria from 373 children under 10 years of age who were followed up for between 3 to 5 years from 1998-2003. About 21% of the children were categorized as 'more susceptible' and although they contributed only 23% of the person-time of follow-up, they experienced 55% of total clinical malaria episodes. Children that were parasite negative at all cross-sectional survey were less likely to belong to this group [AOR = 0.09, (95% CI: 0.14-0.61), p = 0.001]. CONCLUSIONS AND SIGNIFICANCE: The pattern of clinical malaria episodes follows a negative binomial distribution. Use of lack of a clinical malaria episode in a certain time period as endpoints for intervention or immunological studies may not adequately distinguish groups who are more or less immune. It may be useful in such studies, in addition to the usual endpoint of the time to first episode, to include end points which take into account the total number of clinical episodes experienced per child

Transport optimization on complex networks

We present a comparative study of the application of a recently introduced heuristic algorithm to the optimization of transport on three major types of complex networks. The algorithm balances network traffic iteratively by minimizing the maximum node betweenness with as little path lengthening as possible. We show that by using this optimal routing, a network can sustain significantly higher traffic without jamming than in the case of shortest path routing. A formula is proved that allows quick computation of the average number of hops along the path and of the average travel times once the betweennesses of the nodes are computed. Using this formula, we show that routing optimization preserves the small-world character exhibited by networks under shortest path routing, and that it significantly reduces the average travel time on congested networks with only a negligible increase in the average travel time at low loads. Finally, we study the correlation between the weights of the links in the case of optimal routing and the betweennesses of the nodes connected by them.Comment: 19 pages, 7 figure