Showing papers by "University of Guelph published in 1980"

Correction of flux measurements for density effects due to heat and water vapour transfer

Abstract: When the atmospheric turbulent flux of a minor constituent such as CO2 (or of water vapour as a special case) is measured by either the eddy covariance or the mean gradient technique, account may need to be taken of variations of the constituent's density due to the presence of a flux of heat and/or water vapour. In this paper the basic relationships are discussed in the context of vertical transfer in the lower atmosphere, and the required corrections to the measured flux are derived. If the measurement involves sensing of the fluctuations or mean gradient of the constituent's mixing ratio relative to the dry air component, then no correction is required; while with sensing of the constituent's specific mass content relative to the total moist air, a correction arising from the water vapour flux only is required. Correspondingly, if in mean gradient measurements the constituent's density is measured in air from different heights which has been pre-dried and brought to a common temperature, then again no correction is required; while if the original (moist) air itself is brought to a common temperature, then only a correction arising from the water vapour flux is required. If the constituent's density fluctuations or mean gradients are measured directly in the air in situ, then corrections arising from both heat and water vapour fluxes are required. These corrections will often be very important. That due to the heat flux is about five times as great as that due to an equal latent heat (water vapour) flux. In CO2 flux measurements the magnitude of the correction will commonly exceed that of the flux itself. The correction to measurements of water vapour flux will often be only a few per cent but will sometimes exceed 10 per cent.

The requirement and toxicity of selenium in rainbow trout (Salmo gairdneri).

Abstract: This study measured the dietary selenium requirement of rainbow trout and their response to excessive levels of dietary selenium. A dietary selenium level of 0.07 microgram/g dry feed with a waterborne selenium level of 0.4 +/- 0.2 microgram/liter and a dietary vitamin E level of 0.4 IU/g dry diet was sufficient to prevent frank selenium deficiency symptoms. Maximal plasma GSH.px activity was obtained at a dietary selenium level between 0.15 and 0.38 microgram/g dry feed which is less than the average selenium concentration of commercial diets. Chronic dietary selenium toxicity occurred at 13 microgram selenium/g dry feed. Major effects of selenium toxicity were reduced growth rate, poor feed efficiency and a high number of mortalities. No histopathological lesions or significant deviation in the investigated blood parameters or liver somatic index were detected in trout raised on diets containing 13 microgram selenium/g dry feed. Tissue selenium analysis indicated that trout can maintain homeostasis with dietary selenium levels up to 1.25 microgram/g dry feed. The selenium uptake and accumulation in tissues of trout reared on diets containing in excess of 3 microgram/g dry feed may ultimately be toxic to trout if maintained over long periods of time.

Satisfaction and Happiness

Abstract: I review the recent literature on satisfaction and happiness, identify some plausible next steps to take at the frontiers of the research field and offer some suggestions to facilitate those steps. Using partial correlation techniques, substantial levels of covariation are found among the variables that are used in predictions of satisfaction and happiness with life as a whole from satisfaction with specific domains (e.g. family life, health). Using path analysis, confirmation is found in a dozen domains for a model which has satisfaction as a function of a perceived goal-achievement gap, and the latter as a function of comparisons with previous best experience and the status of average folks. Using discriminant analysis, satisfaction with family life is found to be a powerful and predominant discriminator among three groups, identified as Frustrated (dissatisfied and unhappy), Resigned (satisfied and unhappy) and Achievers (satisfied and happy).

Why the Preferred Hand Taps More Quickly than the Non-preferred Hand: Three Experiments on Handedness*

Abstract: Three separate experiments pursue the question of why the preferred hand outperforms the non-preferred hand on a simple finger tapping task. Experiment I rules out possible differential effects of fatigue on the differences between hands. Experiment 11 shows that the singledirection components of the 'up' and 'down' travel of the index finger are not significantly related to tapping speed and contribute little to the performance differences between hands. This is not so for the reversal portion of the tapping movement, where the transition between movement directions is made. This portion contributes significantly to the superiority of the preferred hand. It is suggested that sensory feedback plays a minor role and that the principal factor in the preferred hand's better performance is precision of force modulation. Manipulation of this factor (Experiment m) leads to changes in the magnitude of the preferred hand's superiority.

The connectance of real ecosystems

Abstract: In the work of Gardner and Ash by1, and May2 it has been shown that ecosystem stability (in the sense of Liapunov stability of equilibria3) imposes nontrivial constraints (summarised below) on ecosystem structure, but little has been done to relate this work to observations. One such study was undertaken by Rejm´nek and Starý4, who found in a collection of plant–aphid–parasitoid food webs that connectance C (roughly speaking, the fraction of pairs of species that directly interact) decreases like S−1 as species richness S (the total number of species) increases. Here I analyse a sample of community food webs (the webs of ref. 4 are sink webs5), and find a somewhat slower decrease of connectance with increasing species richness. This behaviour suggests, within the context of May's theory2, that complex ecosystems will tend either to be more fragile or to have weaker interspecific interactions than simpler ones.

Evolutionary implications of polyploidy in amphibians and reptiles.

Abstract: In plants, Polyploidy is recognized to be a wide-spread phenomenon and of considerable practical and evolutionary importance, whereas polyploid animal species have been relegated for the most part, to insignificance in terms of their existence or evolutionary importance. Evolutionary and genetic authorities have adhered mostly to Mullers’s 1925 (1) contention that sexual imbalance in polyploids would not permit bisexual polyploids to exist as natural entities in animals as they do in plants, which are capable of vegetative reproduction. Asexual polyploids are also condemned, in animals, by the commonly held, and mathematically “proven” (2) viewpoint that this method of reproduction reduces genetic recombination and is tantamount to phylogenetic suicide (3–5). It is evident, however, that an increasing number of polyploid amphibians and reptiles are being encountered in natural populations living in North America, South America, Europe, Asia, and Africa. To ignore their existence or to pass judgement on their evolutionary significance without adequate study is incomprehensible. In spite of the theoretical dogma surrounding animal polyploids, there is a growing bank of data which suggests that naturally occurring animal polyploids may play an interesting and significant role in population genetics and speciation.

Metallothionein occurs in roots of Agrostis tolerant to excess copper

Abstract: Metallothioneins have an important function in metal metabolism in animals1. These low molecular weight proteins have high contents of half-cystinyl residues (up to 33%) which can bind metals such as Zn, Cu, Cd, Hg or Ag in mercaptide complexes1. In normal conditions animal tissues have low concentrations of metallothioneins, but these increase on administration of metal2–4, a reaction which is consistent with their suggested role in detoxification mechanisms2,5,6. Various plant genotypes exhibit tolerance to excesses of metals7, and Jowett8 proposed that such genotypes contain compounds capable of specific metal chelation. Metallothioneins could serve such a role. We report here that copper-thionein occurs in the roots of a clone of Agrostis gigantea Roth tolerant to excess copper9. This is the first unequivocal demonstration of a metallothionein in a vascular plant. These unusual proteins may have a role in metal metabolism in plants and could be important in the elucidation of the mechanism of metal tolerance.

Accuracy of catch-effort methods for estimating fish density and biomass in streams

Abstract: At each of 11 localities a section of stream was closed off with nets and an electrofisher used to estimate the abundance of fishes in the section. Each section was fished from 5–7 times with each fishing equalling one unit of effort. Using the catch-effort methods of Leslie, DeLury and Ricker, separate estimates were made for each species. In several cases species were split into size groups and estimates made for each group. The fish remaining in each section after the fishings were collected using rotenone. Thus the estimates could be compared to the actual number of fish present. Estimates were considered to be either ‘good’, if the regressions used in the above methods were statistically significant or ‘bad’ if they were not significant. Lower limits for the number of fish and mean weight of a fish for ‘good’ estimates were identified. The Leslie and Ricker estimates, which did not differ significantly, were least in error. They tended to underestimate (−21.6% on the average for the Leslie method). Direct estimates of biomass did not differ significantly from those made using the estimates for numbers and the mean weight of fish caught. The interrelationships among variables such as mean weight, numbers, catchability, density, biomass, number of catches used, proportion of fish taken during the estimate, number of fish in the last catch and their relationships with the error of the estimates were examined using correlation and principal components analysis. Error was most closely related to the proportion of fish collected. The effects of other variables such as mean weight affected error through catchability and subsequently the proportion of fishes caught. It was not possible to predict a significant proportion of the error using variables which could be measured without a complete collection. The effects of locality, electrofisher, and species on error were examined. Each accounted for a significant proportion of the variability in error but primarily by affecting the proportion of fish caught. These results suggest that the most appropriate way of decreasing error would be to increase the total effort and consequently the proportion of fish collected. This would be best done by increasing the number of fishings used in the estimate. Catchability tended to decrease in successive fishings. The observed trends in changing catchability accounted for most of the error. Size-selectivity, which was evident as a change in mean weight in successive catches, was not significantly associated with changing catchability.

Neonatal Growth of Northwest Atlantic Harp Seals, Pagophilus groenlandicus

Abstract: Morphometric data were obtained from 219 neonatal harp seals in the Northwest Atlantic in March and April, 1976 to 1979. At birth, pups weighed 10.8 ± 0.65 kg and grew at a rate of 2.5 kg/day during the nursing period, which lasted about 9 days. Much of this weight gain (1.9 kg/day) was associated with deposition of the subcutaneous layer of insulating fat, with the remainder accounted for by growth of the lean body mass. During the post-weaning period, total body weight declined considerably from the weaning weight. Energy was lost primarily from the core, which decreased in weight by 35%; the weight of the blubber layer with pelt attached declined by only 10%. Maintenance of the blubber layer may be necessary to facilitate homeothermy by reducing heat loss as the young seal begins to forage in the aquatic environment. In view of the complex series of events experienced by newly-weaned harp seals, the common assumption that natural mortality is constant over all age classes warrants further investigation.

Effect of Dehydration on Leakage and Membrane Structure in Lotus corniculatus L. Seeds.

Abstract: Membrane damage as a result of dehydration was studied in Lotus corniculatus L. cv. Carroll seeds which had been pregerminated for 0, 12, and 24 hours prior to dehydration. During reimbibition, desiccation-tolerant (0- and 12-hour) seeds leaked relatively low quantities of all solutes (total electrolytes, potassium, phosphate, sugar, amino acid, and protein). Desiccation-sensitive (24-hour) seeds leaked higher levels, but evidence of selective permeability remained. Membrane damage was not manifested as a complete removal of the diffusion barrier, although its permeability properties were dramatically altered. Consequently, the plasmalemma was not ruptured or torn by the dehydration treatment, but a more subtle structural alteration occurred. The possibility that seed membranes form a hexagonal rather than a lamellar phase at moisture contents below 20% was investigated by x-ray diffraction. Phospholipids were extracted from desiccation-tolerant (0-hour) and desiccation-sensitive (24-hour) seeds and hydrated to 5, 10, 20, and 40% water. This phospholipid-water system was examined using low-and wide-angle x-ray diffraction and was found to be exclusively lamellar, even at 5% water. Consequently, membrane damage and the leakage of cytoplasmic solutes from seeds cannot be explained by the formation of a hexagonal phase by membrane phospholipids.

The Role of Sulfate in the Calciuria of High Protein Diets in Adult Rats

Abstract: Diets containing different sources of protein were evaluated for their effect or urinary calcium (Ca) excretion in adult male rats. High protein diets were prepared by adding 24 g N/kg as lactalbumin (Hi-Lact), egg white (Hi-EW), casein (Hi-Cas) or gelatin (Hi-Gel) to a control diet containing 24 g N/kg ascasein (Cas). There were significant differences in the degree of hypercalciuria produced by different dietary protein mixtures. A peak in Ca excretion occurred at about 2 days, when the relative values were as follows (Cas = 100): Hi-Lact, 489; Hi-EW, 429; Hi-Cas, 340, and Hi-Gel, 263. Subsequently urinary Ca declined, but a moderate hypercalciuria persisted to the end of the 8-weekexperiment, when the corresponding values (% Cas) were 200, 183,160 and 136, respectively. The degree of hypercalciuria was proportional to the sulfur content of the diets, i.e., Hi-Lact greater than Hi-EW greater than Hi-Cas greater than Hi-Gel greater than Cas. Supplementing the Cas diet with sulfur amino acids to the level present in the Hi-Lact diet resulted in a comparable increase in Ca excretion. Supplementing the Cas diet with 1.42% sulfate produced a 570% increase in urinary Ca on day 2 and a 306% increase at 5 weeks. There was a linear relationship between Ca excretion and sulfate excretion. It is proposed that a major factor in the hypercalciuria of high protein feeding is the production and excretion of sulfate. Variability in the calciuric effect of different proteins appears to be related mainly to differences in their sulfur amino acid content.

The process of habituation to treadmill walking at different velocities

Abstract: Eighteen young adult male subjects, who were naive to treadmill walking were walked for ten minutes on a motorised treadmill. The subjects were split into three groups with the six subjects in each group walking at a given relative speed. The use of relative speed factors out stature differences which are known to affect walking velocity. The relative speeds chosen were 0-55 (slow), 0-86 (normal) and 1-2 (fast) statures s-1. The angular kinematics and temporal aspects of gait were analysed to determine at which point in the exposure to treadmill walking a stable walking pattern was achieved. The results showed that there was an initial, rapid accommodiation to the new modality followed by a longer more gradual habituation. However even after ten minutes of treadmill walking a steady state had not been achieved in any of the groups.

Interfacial Water Structure in Montmorillonite from Neutron Diffraction Experiments

Abstract: Neutron diffraction measurements for a preferentially oriented aggregate slab sample of deu- terated Na-montmorillonite from Upton, Wyoming, are described for a series of clay-water contents rang- ing from 0 to 500 mg/g. A neutron wavelength of 2.39 A was used with extended detectors to collect much of the "out of plane" component of the diffraction peak intensities. The diffraction pattern intensities from the 00~ e planes of the clay, corresponding to a reflection geometry, are a strong function of sample water content and show a variation in basal spacing from 9.8 to 19.0/~. The hk reflections from transmission geometry measurements show, however, that the lattice a and b axes are constant within experimental uncertainty (0.02/~) over the range in water content and their intensities vary only by a few percent. In this geometry, a broad, water-like diffraction pattern was noted as a background under the usual hk peak intensity series. This underlying water-like pattern varies in proportion to the sample water content. Data reduction steps included consideration of background removal, multiple scattering, flux normali- zation, and attenuation of scattering due to sample thickness. Analysis of the reduced data revealed that the clay-water has a "liquid-like" ordering, with a density increase of approximately 5% over bulk water. An association between a few interlayer water molecules and the silicate superstructure is indicated by the slight change in the hk band intensities, but this change seems to be complete at water contents below 100 mg/g. Fourier analysis of the basal peak series from the dry clay shows that the hydrogens of the lattice hydroxyl groups lie in the same basal plane as their associated oxygen atoms.

Information Seeking by Fashion Opinion Leaders and Followers

Abstract: A self-designating scale was included in a mailed questionnaire to identify fashion opinion leaders, followers, and indeterminates among female undergraduates. The number, fre quency, type, and variety of fashion information sources used by leaders and followers in the awareness, comprehension, and legitimation stages of the fashion adoption process were studied. The demographic characteristics of the respondents were also examined. Both the leaders and followers used all of the twenty-one sources studied. However, the leaders consulted a greater number of sources more frequently than did the followers. Both the leaders and followers recalled marketer-dominated sources as creating awareness of new clothing styles. However, the most important sources in the comprehension stage were marketer-dominated sources for the leaders and consumer-dominated sources for the fol lowers. Leaders and followers could not be differentiated by demographic characteristics.

Evidence for a thermal spike mechanism in the erosion of frozen xenon

Abstract: Recent measurements of the sputtering of frozen gases by MeV ions exhibit yields that are several orders of magnitude larger than predicted by collision cascade theory. Of the models considered, only a “thermal spike” model is consistent with our experimental observations. The various experimental parameters studied include the energy (0.3–2.0 MeV), atomic number (H+. He+. N+ and Ar+). angle of incidence and current density of the incident ion beam. the thermal conductivity of the substrate, and the temperature and thickness of the frozen film. Calculations for 1.0 MeV He + in Xe. based on a thermal spike mechanism, indicate that a localized cylindrical region around each incident ion track is raised to a temperature sufficiently high to evaporate a significant quantity of the frozen gas film.

Numerical response of coccinellids to aphids in corn in southern Ontario.

Abstract: Populations of two abundant coccinellid species, Coleomegilla maculata lengi Timberlake and Hippodamia tredecimpunctata tibialis Say, responded rapidly to corn leaf aphid populations [ Rhopalosiphum maidis (Fitch)] once the aphids became exposed to predation when the plants tasselled. Coleomegilla m . lengi oviposited at lower densities of aphids than did H . t . tibialis but H . t . tibialis was shown to have a greater numerical response than C . m . lengi at high densities of aphids due to its greater fecundity. The numerical response of the coccinellids by oviposition was linear with a lag of 1/2 week behind the aphid population.

Charles Darwin and group selection.

Abstract: Summary The question of the levels at which natural selection can be said to operate is much discussed by biologists today and is a key factor in the recent controversy about sociobiology. It is shown that this problem is one to which Charles Darwin addressed himself at some length. It is argued that apart from some slight equivocation over man, Darwin opted firmly for hypotheses supposing selection always to work at the level of the individual rather than the group. However, natural selection's co-discoverer, Alfred Russel Wallace, endorsed group selection hypotheses.