Showing papers by "University of Guelph published in 2001"

Measurement of the rate of ve + d → p + p + e- interactions produced by 8B solar neutrinos at the sudbury neutrino observatory

Abstract: Solar neutrinos from the decay of 8B have been detected at the Sudbury Neutrino Observatory (SNO) via the charged current (CC) reaction on deuterium and by the elastic scattering (ES) of electrons. The CC reaction is sensitive exclusively to νe, while the ES reaction also has a small sensitivity to νμ and ντ. The flux of νe from 8B decay measured by the CC reaction rate is φCC(ν e )=[1.75±0.07(stat.) −0.11 +0.12 (syst.)×0.05(theor.)]×106cm−2s−1. Assuming no flavor transformation, the flux inferred from the ES reaction rate is φES(ν x )=[2.39±0.34(stat.) −0.14 +0.16 (syst.)]×106cm−2s−1. Comparison of φCC(νe) to the Super-Kamiokande collaboration’s precision value of φES(νx) yields a 3.3σ difference, assuming the systematic uncertainties are normally distributed, providing evidence that there is a nonelectron flavor active neutrino component in the solar flux. The total flux of active 8B neutrinos is thus determined to be (5.44±0.99)×106 cm−2 s−1, in close agreement with the predictions of solar models.

GGEbiplot—A Windows Application for Graphical Analysis of Multienvironment Trial Data and Other Types of Two-Way Data

Abstract: facilitate the application of the GGE biplot methodology in MET data analysis and in analyses of other types Plant breeding trials produce quantities of data and finding the of two-way data, a Windows application, the GGEbiplot useful information within that data has historically been a major challenge of plant breeding. A recently developed graphical data software, was developed. This paper describes the funcsummary, called GGEbiplot, can aid in data exploration. GGEbiplot tions built in this software and exemplifies their use in is a Windows application that performs biplot analysis of two-way MET data analysis. data that assume an entry tester structure. GGEbiplot analyzes the data and outputs the results as an image, and it also produces an WHAT IS A GGE BIPLOT? interactive show of the data. It allows interactive visualization of the biplot from various perspectives. A multienvironment trial data set, The Concept of Biplot in which cultivars are entries and environments are testers, was used The concept of biplot was first proposed by Gabriel to demonstrate the functions of GGEbiplot. These include but are not limited to: (i) ranking the cultivars based on their performance (1971). The main ideas follow. Any two-way table or in any given environment, (ii) ranking the environments based on matrix X that contains n rows and m columns can be the relative performance of any given cultivar, (iii) comparing the regarded as the product of two matrices: A with n rows performance of any pair of cultivars in different environments, (iv) and r columns and B with r rows and m columns. Thereidentifying the best cultivar in each environment, (v) grouping the fore, Matrix X can always be decomposed to its two environments based on the best cultivars, (vi) evaluating the cultivars component matrices, A and B. If r happens to be 2, based on both average yield and stability, (vii) evaluating the environ- Matrix X is referred to as a rank-two matrix. Each row ments based on both discriminating ability and representativeness, in Matrix A has two values, which define a point in a and (viii) visualizing all of these aspects for a subset of the data by two-dimensional plot. Similarly, each column in Matrix removing some of the cultivars or environments. GGEbiplot has been

Dynamics of the 2001 UK foot and mouth epidemic: stochastic dispersal in a heterogeneous landscape

Abstract: Foot-and-mouth is one of the world's most economically important livestock diseases. We developed an individual farm-based stochastic model of the current UK epidemic. The fine grain of the epidemiological data reveals the infection dynamics at an unusually high spatiotemporal resolution. We show that the spatial distribution, size, and species composition of farms all influence the observed pattern and regional variability of outbreaks. The other key dynamical component is long-tailed stochastic dispersal of infection, combining frequent local movements with occasional long jumps. We assess the history and possible duration of the epidemic, the performance of control strategies, and general implications for disease dynamics in space and time.

Caffeine and exercise: metabolism, endurance and performance

Abstract: Caffeine is a common substance in the diets of most athletes and it is now appearing in many new products, including energy drinks, sport gels, alcoholic beverages and diet aids. It can be a powerful ergogenic aid at levels that are considerably lower than the acceptable limit of the International Olympic Committee and could be beneficial in training and in competition. Caffeine does not improve maximal oxygen capacity directly, but could permit the athlete to train at a greater power output and/or to train longer. It has also ben shown to increase speed and/or power output in simulated race conditions. These effects have been found in activities that last as little as 60 seconds or as long as 2 hours. There is less information about the effects of caffeine on strength; however, recent work suggests no effect on maximal ability, but enhanced endurance or resistance to fatigue. There is no evidence that caffeine ingestion before exercise leads to dehydration, ion imbalance, or any other adverse effects. The ingestion of caffeine as coffee appears to be ineffective compared to doping with pure caffeine. Related compounds such as theophylline are also potent ergogenic aids. Caffeine may act synergistically with other drugs including ephedrine and anti-inflammatory agents. It appears that male and female athletes have similar caffeine pharmacokinetics, i.e., for a given dose of caffeine, the time course and absolute plasma concentrations of caffeine and its metabolites are the same. In addition, exercise or dehydration does not affect caffeine pharmacokinetics. The limited information available suggests that caffeine non-users and users respond similarly and that withdrawal from caffeine may not be important. The mechanism(s) by which caffeine elicits its ergogenic effects are unknown, but the popular theory that it enhances fat oxidation and spares muscle glycogen has very little support and is an incomplete explanation at best. Caffeine may work, in part, by creating a more favourable intracellular ionic environment in active muscle. This could facilitate force production by each motor unit.

Impact of Bt corn pollen on monarch butterfly populations: A risk assessment

Abstract: A collaborative research effort by scientists in several states and in Canada has produced information to develop a formal risk assessment of the impact of Bt corn on monarch butterfly (Danaus plexippus) populations. Information was sought on the acute toxic effects of Bt corn pollen and the degree to which monarch larvae would be exposed to toxic amounts of Bt pollen on its host plant, the common milkweed, Asclepias syriaca, found in and around cornfields. Expression of Cry proteins, the active toxicant found in Bt corn tissues, differed among hybrids, and especially so in the concentrations found in pollen of different events. In most commercial hybrids, Bt expression in pollen is low, and laboratory and field studies show no acute toxic effects at any pollen density that would be encountered in the field. Other factors mitigating exposure of larvae include the variable and limited overlap between pollen shed and larval activity periods, the fact that only a portion of the monarch population utilizes milkweed stands in and near cornfields, and the current adoption rate of Bt corn at 19% of North American corn-growing areas. This 2-year study suggests that the impact of Bt corn pollen from current commercial hybrids on monarch butterfly populations is negligible.

Osmosensing and osmoregulatory compatible solute accumulation by bacteria

Abstract: Bacteria inhabit natural and artificial environments with diverse and fluctuating osmolalities, salinities and temperatures. Many maintain cytoplasmic hydration, growth and survival most effectively by accumulating kosmotropic organic solutes (compatible solutes) when medium osmolality is high or temperature is low (above freezing). They release these solutes into their environment when the medium osmolality drops. Solutes accumulate either by synthesis or by transport from the extracellular medium. Responses to growth in high osmolality medium, including biosynthetic accumulation of trehalose, also protect Salmonella typhimurium from heat shock. Osmotically regulated transporters and mechanosensitive channels modulate cytoplasmic solute levels in Bacillus subtilis, Corynebacterium glutamicum, Escherichia coli, Lactobacillus plantarum, Lactococcus lactis, Listeria monocytogenes and Salmonella typhimurium. Each organism harbours multiple osmoregulatory transporters with overlapping substrate specificities. Membrane proteins that can act as both osmosensors and osmoregulatory transporters have been identified (secondary transporters ProP of E. coli and BetP of C. glutamicum as well as ABC transporter OpuA of L. lactis). The molecular bases for the modulation of gene expression and transport activity by temperature and medium osmolality are under intensive investigation with emphasis on the role of the membrane as an antenna for osmo- and/or thermosensors.

Bacterial Recognition of Mineral Surfaces: Nanoscale Interactions Between Shewanella and α-FeOOH

Abstract: Force microscopy has been used to quantitatively measure the infinitesimal forces that characterize interactions between Shewanella oneidensis (a dissimilatory metal-reducing bacterium) and goethite (alpha-FeOOH), both commonly found in Earth near-surface environments. Force measurements with subnanonewton resolution were made in real time with living cells under aerobic and anaerobic solutions as a function of the distance, in nanometers, between a cell and the mineral surface. Energy values [in attojoules (10(-18) joules)] derived from these measurements show that the affinity between S. oneidensis and goethite rapidly increases by two to five times under anaerobic conditions in which electron transfer from bacterium to mineral is expected. Specific signatures in the force curves suggest that a 150-kilodalton putative iron reductase is mobilized within the outer membrane of S. oneidensis and specifically interacts with the goethite surface to facilitate the electron transfer process.

Chromate reduction by a pseudomonad isolated from a site contaminated with chromated copper arsenate.

Abstract: A pseudomonad (CRB5) isolated from a decommissioned wood preservation site reduced toxic chromate [Cr(VI)] to an insoluble Cr(III) precipitate under aerobic and anaerobic conditions. CRB5 tolerated up to 520 mg of Cr(VI) liter(-1) and reduced chromate in the presence of copper and arsenate. Under anaerobic conditions it also reduced Co(III) and U(VI), partially internalizing each metal. Metal precipitates were also found on the surface of the outer membrane and (sometimes) on a capsule. The results showed that chromate reduction by CRB5 was mediated by a soluble enzyme that was largely contained in the cytoplasm but also found outside of the cells. The crude reductase activity in the soluble fraction showed a K(m) of 23 mg liter(-1) (437 microM) and a V(max) of 0.98 mg of Cr h(-1) mg of protein(-1) (317 nmol min(-1) mg of protein(-1)). Minor membrane-associated Cr(VI) reduction under anaerobiosis may account for anaerobic reduction of chromate under nongrowth conditions with an organic electron donor present. Chromate reduction under both aerobic and anaerobic conditions may be a detoxification strategy for the bacterium which could be exploited to bioremediate chromate-contaminated or other toxic heavy metal-contaminated environments.

Pigs expressing salivary phytase produce low-phosphorus manure

Abstract: To address the problem of manure-based environmental pollution in the pork industry, we have developed the phytase transgenic pig. The saliva of these pigs contains the enzyme phytase, which allows the pigs to digest the phosphorus in phytate, the most abundant source of phosphorus in the pig diet. Without this enzyme, phytate phosphorus passes undigested into manure to become the single most important manure pollutant of pork production. We show here that salivary phytase provides essentially complete digestion of dietary phytate phosphorus, relieves the requirement for inorganic phosphate supplements, and reduces fecal phosphorus output by up to 75%. These pigs offer a unique biological approach to the management of phosphorus nutrition and environmental pollution in the pork industry.

Deconstructing Family Time: From Ideology to Lived Experience

Abstract: “Family time” is often uncritically accepted as a uniform, coherent concept and a universally desirable goal. In order to fully understand the meaning of family time in experience, interviews were conducted with parents in 17 dual-earner and 11 single-parent families, and 8 observation episodes were done with 4- and 5-year-old children in childcare. What emerged was a dramatic discordance between the expectations and experiences of family time. Although families have held on to an expectation of a positive experience of togetherness, they are typically left with a feeling that there is never enough, that it is in the service of children, and that they are duty-bound by it. There is a structural contradiction between the ideals and experience of family time that is typically expressed through disillusionment and guilt.

Flies and flowers: taxonomic diversity of anthophiles and pollinators

Abstract: The Diptera are the second most important order among flower-visiting (anthophilous) and flower-pollinating insects worldwide. Their taxonomic diversity ranges from Nematocera to Brachycera, including most families within the suborders. Especially important are Syrphidae, Bombyliidae, and Muscoidea. Other families, especially of small flies, are less appreciated and often overlooked for their associations with flowers. We have compiled records of their flower visitations to show that they may be more prevalent than usually thought. Our knowledge of anthophilous Diptera needs to be enhanced by future research concerning (i) the significance of nocturnal Nematocera and acalypterate muscoids as pollinators, (ii) the extent to which the relatively ineffective pollen-carrying ability of some taxa can be compensated by the abundance of individuals, and (iii) the role of Diptera as pollinators of the first flowering plants (Angiospermae) by using phylogenetic and palaeontological evidence. Specializations in floral relationships involve the morphology of Diptera, especially of their mouthparts, nutritional requirements, and behaviour, as well as concomitant floral attributes. The South African flora has the most highly specialized relations with dipterous pollinators, but in arctic and alpine generalist fly–flower relations are important in pollination and fly nutrition.

beta-Amyloid efflux mediated by p-glycoprotein.

Abstract: A large body of evidence suggests that an increase in the brain beta-amyloid (Abeta) burden contributes to the etiology of Alzheimer's disease (AD). Much is now known about the intracellular processes regulating the production of Abeta, however, less is known regarding its secretion from cells. We now report that p-glycoprotein (p-gp), an ATP-binding cassette (ABC) transporter, is an Abeta efflux pump. Pharmacological blockade of p-gp rapidly decrease extracellular levels of Abeta secretion. In vitro binding studies showed that addition of synthetic human Abeta1-40 and Abeta1-42 peptides to hamster mdr1-enriched vesicles labeled with the fluorophore MIANS resulted in saturable quenching, suggesting that both peptides interact directly with the transporter. Finally, we were able to directly measure transport of Abeta peptides across the plasma membranes of p-gp enriched vesicles, and showed that this phenomenon was both ATP- and p-gp-dependent. Taken together, our study suggests a novel mechanism of Abeta detachment from cellular membranes, and represents an obvious route towards identification of such a mechanism in the brain.

Molecular weight dependence of reductions in the glass transition temperature of thin, freely standing polymer films.

Abstract: We have used transmission ellipsometry to perform a comprehensive study of the glass transition temperature ${T}_{g}$ of freely standing polystyrene films. Six molecular weights ${M}_{w},$ ranging from $575\ifmmode\times\else\texttimes\fi{}{10}^{3}$ to $9100\ifmmode\times\else\texttimes\fi{}{10}^{3},$ were used in the study. For each ${M}_{w}$ value, large reductions in ${T}_{g}$ (as much as $80\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ below the bulk value) were observed as the film thickness h was decreased. We have studied in detail the dependence of the ${T}_{g}$ reductions on ${M}_{w}$ in a regime dominated by chain confinement effects. The empirical analysis presented is highly suggestive of the existence of a mechanism of mobility in thin freely standing films that is inhibited in the bulk and distinct from the usual cooperative motion associated with the glass transition.

Two Types of GGE Biplots for Analyzing Multi-Environment Trial Data

Abstract: SA genotype main effect plus genotype x environment interaction (GGE) biplot graphically displays the genotypic main effect (G) and the genotype x environment interaction (GE) of the multienvironment trial (MET) data and facilitates visual evaluation of both the genotypes and the environments. This paper compares the merits of two types of GGE biplots in MET data analysis. The first type is constructed by the least squares solution of the sites regression model (SREG 2 ), with the first two principal components as the primary and secondary effects, respectively. The second type is constructed by Mandel's solution for sites regression as the primary effect and the first prindpal component extracted from the regression residual as the secondary effect (SREG M+1 ). Results indicate that both the SREG 2 biplot and the SREG M+1 biplot are equally effective in displaying the which-won-where pattern of the MET data, although the SREG 2 biplot explains slightly more GGE variation. The SREG M+1 biplot is more desirable, however, in that it always explicitly indicates the average yield and stability of the genotypes and the discriminating ability and representativeness of the test environments.

Interpretation of genotype × environment interaction for winter wheat yield in Ontario

Abstract: An understanding of the causes of genotype × environment (GE) interaction can help identify traits that contribute to better cultivar performance and environments that facilitate cultivar evaluation. Through subjecting environment-centered yield of a multi-environment trial data to singular value decomposition, the portion of yield variation that is relevant to cultivar evaluation is partitioned into noncrossover and crossover GE interaction, quantified by the first two principal components (PC), respectively. Each PC is a set of genotypic scores multiplied by a set of environmental scores. By relating the PC scores to genotypic and environmental covariates, GE interaction represented by each PC can be interpreted in terms of trait × factor interactions. This strategy was employed in analysis of the 1992 to 1998 Ontario winter wheat (Triticum aestivum L.) performance trial data. Results indicated that plant height and maturity were the major genotypic causes of GE interaction, whereas cold temperature in the winter and hot temperature in the summer were the major environmental causes of GE interaction. Positive interactions were found between earlier maturity vs. warmer winters or hotter summers, and between shorter plant height vs. warmer winters or cooler summers. In addition, better resistance to septoria leaf blotch (caused by Septoria secalis Prill. & Delacr.) was frequently associated with overall performance. The results of this study should help in determining breeding objectives and for selecting test sites or environments for winter wheat breeding in Ontario.

Weather Derivatives for Specific Event Risks in Agriculture

Abstract: This paper examines the economics and pricing of weather derivatives in Ontario and argues that weather derivatives and weather insurance can be used as a form of agricultural insurance. Using historical data, the relationship between crop productivity and weather is examined. Then a variety of put and call options for rain- and heat-based weather risk are discussed and numerically evaluated. The evaluation examines in detail the pricing of insurance contracts at a given location and across space.

The Behavioral Ecology of Intermittent Locomotion1

Abstract: Most physiological and ecological approaches to animal locomotion are based on steady state assumptions, yet movements of many animals are interspersed with pauses lasting from milliseconds to minutes. Thus, pauses, along with changes in the duration and speed of moves, form part of a dynamic system of intermittent locomotion by which animals adjust their locomotor behavior to changing circumstances. Intermittent locomotion occurs in a wide array of organisms from protozoans to mammals. It is found in aerial, aquatic and terrestrial locomotion and in many behavioral contexts including search and pursuit of prey, mate search, escape from predators, habitat assessment and general travel. In our survey, animals exhibiting intermittent locomotion paused on average nearly 50% of their locomotion time (range 6–94%). Although intermittent locomotion is usually expected to increase energetic costs as a result of additional expenditure for acceleration and deceleration, a variety of energetic benefits can arise when forward movement continues during pauses. Endurance also can be improved by partial recovery from fatigue during pauses. Perceptual benefits can arise because pauses increase the capacity of the sensory systems to detect relevant stimuli. Several processes, including velocity blur, relative motion detection, foveation, attention and interference between sensory systems are probably involved. In animals that do not pause, alternative mechanisms for stabilizing the perceptual field are often present. Because movement is an important cue for stimulus detection, pauses can also reduce unwanted detection by an organism's predators or prey. Several models have attempted to integrate energetic and perceptual processes, but many challenges remain. Future advances will require improved quantification of the effects of speed on perception.

Barriers to Agricultural Exports from Developing Countries: The Role of Sanitary and Phytosanitary Requirements

Abstract: This paper explores the impact of sanitary and phytosanitary (SPS) measures in developed countries on developing country exports of agricultural and food products. It identifies the problems that developing countries face in meeting SPS requirements and how these relate to the nature of SPS measures and the compliance resources available to government and the supply chain. The paper examines the impact of the WTO's SPS Agreement on the extent to which SPS measures impede exports from developing countries. It identifies the problems that limit the participation of developing countries in the SPS Agreement and their concerns about the way in which it currently operates.

Essential smoothness, essential strict convexity, and legendre functions in banach spaces

Abstract: The classical notions of essential smoothness, essential strict convexity, and Legendreness for convex functions are extended from Euclidean to Banach spaces. A pertinent duality theory is developed and several useful characterizations are given. The proofs rely on new results on the more subtle behavior of subdifferentials and directional derivatives at boundary points of the domain. In weak Asplund spaces, a new formula allows the recovery of the subdifferential from nearby gradients. Finally, it is shown that every Legendre function on a reflexive Banach space is zone consistent, a fundamental property in the analysis of optimization algorithms based on Bregman distances. Numerous illustrating examples are provided.

Thermolysis of fluoropolymers as a potential source of halogenated organic acids in the environment

Abstract: Following the introduction of hydrochlorofluorocarbon (HCFCs) and hydrofluorocarbon (HFCs) gases as replacements for the ozone-destroying chlorofluorocarbons (CFCs), it has been discovered that HCFCs/HFCs can degrade in the atmosphere to produce trifluoroacetic acid1, a compound with no known loss mechanisms in the environment2,3, and higher concentrations in natural waters4 have been shown to be mildly phytotoxic5. Present environmental levels of trifluooracetic acid are not accounted by HCFC/HFC degradation alone8,9,10. Here we report that thermolysis of fluorinated polymers, such as the commercial polymers Teflon and Kel-F, can also produce trifluoroacetate and the similar compound chlorodifluoroacetate. This can occur either directly, or indirectly via products that are known to degrade to these haloacetates in the atmosphere11. The environmental significance of these findings is confirmed by modelling, which indicates that the thermolysis of fluoropolymers in industrial and consumer high-temperature applications (ovens, non-stick cooking utensils and combustion engines) is likely to be a significant source of trifluoroacetate in urban rain water (∼25 ng l-1, as estimated for Toronto). Thermolysis also leads to longer chain polyfluoro- and/or polychlorofluoro- (C3–C14) carboxylic acids which may be equally persistent. Some of these products have recently been linked with possible adverse health6 and environmental impacts and are being phased out of the US market7. Furthermore, we detected CFCs and fluorocarbons—groups that can destroy ozone and act as greenhouse gases, respectively—among the other thermal degradation products, suggesting that continued use of fluoropolymers may also exacerbate stratospheric ozone-depletion and global warming.

Gradient Flow in Recurrent Nets: The Difficulty of Learning LongTerm Dependencies

Abstract: This chapter contains sections titled: Introduction Exponential Error Decay Dilemma: Avoiding Aradient Decay Prevents Long-Term Latching Remedies Conclusion ]]>

Must top predators be culled for the sake of fisheries

Abstract: If humankind occupies the ecological role of top predator, then within individual ecosystems it must compete with other top predators for valuable food resources. This notion presents a fascinating ecological problem, with tremendous social and economic ramifications. Because of the socioeconomic dimension, the scientific debate has at times been controversial. The recent attention and data gathering resources focused on the problem present a unique opportunity to test and refine ecological theory in the arena of complex, large-scale systems.

Measures of Human Capital and Nonlinearities in Economic Growth

Abstract: In this paper we study the relationship between human capital accumulation and economic growth using various measures of human capital frequently employed by researchers. We use semiparametric estimation techniques to uncover any nonlinearities that may exist. Using mean years of schooling measures of human capital we find a nonlinear effect on economic growth. There seem to be important differences in the growth effect of educational attainment by gender and level of education. Enrollment rates do not yield a nonlinear effect.