Showing papers by "University of Alberta published in 1985"

Structure of the calcium regulatory muscle protein troponin-C at 2.8 Å resolution

Abstract: Crystals of turkey skeletal muscle troponin-C reveal a molecule of two domains with an unusual structure. Two Ca2+ ions are bound to the C-terminal domain. The two cation-binding sites of the regulatory (N-terminal) domain are Ca2+ free; this domain adopts a markedly different conformation from the C-terminal domain. The two domains are connected by a long nine-turn α-helix; three of these turns are exposed fully to solvent.

Global stability and persistence of simple food chains

Abstract: The main purpose of this paper is to develop criteria for which a simple food-chain model of intermediate type and of arbitrary length has a globally stable positive equilibrium and to develop criteria under which such a food chain exhibits uniform persistence. The same techniques are used to obtain conditions for a model of a predator-prey system with mutual interference of the predator to possess a globally stable positive equilibrium.

An Algorithm for Generalized Fractional Programs

Abstract: An algorithm is suggested that finds the constrained minimum of the maximum of finitely many ratios. The method involves a sequence of linear (convex) subproblems if the ratios are linear (convex-concave). Convergence results as well as rate of convergence results are derived. Special consideration is given to the case of (a) compact feasible regions and (b) linear ratios.

The dynamics of articulated rigid bodies for purposes of animation

Abstract: Curves and surfaces satisfying continuity and smoothness conditions are used in computer graphics to fit spatial data points. In a similar fashion, smooth motions of objects should be available to animators in such a way that the dynamics are correct to the degree required for realism. The motion, like a curve or surface shape, should be controllable by easy manipulations of a set of control parameters or by real-time interaction between the animator and a scene generated by dynamic simulation. In this paper, the objects considered have the form of rigid links joined at hinges to form a tree. This is a reasonable first approximation to human and animal bodies. The equations of motion are formulated with respect to hinge-centered coordinates, and are solved by an efficient technique in time which grows linearly with the number of links.

Socioeconomic variations in perceived barriers to recreation participation among would‐be participants

Abstract: The effects of fifteen barriers to participation were examined among people who expressed a desire for but were unable to participate in a new recreational activity. Work commitments, overcrowding of facilities, and lack of partners were the three main barriers. The effects of barriers were not perceived uniformly across the sample but varied between subgroups defined according to socioeconomic variables: the people most likely to be affected by barriers to participation included the poor, the elderly, and single parents. The extent to which recreation practitioners can and should respond to these kinds of research findings is discussed, and several ways in which the effects of barriers to participation might be modified or alleviated are evaluated.

Composition of liquids coexisting with spinel lherzolite at 10 kbar and the genesis of MORBs

Abstract: Because of the controversy over the nature of the parental magma for MORBs, experiments have been performed at 10 kbar in order to assess the effect of modal variations in the source peridotite and the effect of temperature (degree of partial melting) on the composition of partial melts. A peridotite-basalt sandwich method was used and a run duration of 72 h was found to be necessary to equilibrate basalt and peridotite. A range of melt compositions, coexisting with olivine, orthopyroxene, clinopyroxene and spinel, was produced at 10 kbar, indicating that partial melting of peridotite cannot be regarded as isobarically pseudoinvariant. On projections in the normative tetrahedron OL-PL-CPX-SIL, the liquids obtained in this study define an area, rather than a point or narrow band. The compositions of some liquids in this study are similar to magnesian MORBs (MgO>9.5 wt%), providing evidence in support of the derivation of magnesian MORBs by partial melting of mantle lherzolite at about 10 kbar.

On the mixed Hodge structure on the cohomology of the Milnor fibre

Abstract: In [18], the second author introduced a mixed Hodge structure on the cohomology of the Milnor fibre of an isolated hypersurface singularity. (For the definition of a mixed Hodge structure, el. [17, Sect. 3.4].) The weight filtration is essentially the "monodromy weight filtration" [18, Sect. 4] and thus simplifies the Jordan normal form of the unipotent part of the monodromy. The significance of the Hodge filtration, however, is not so dear, and its description seems difficult to use. This paper gives another description of the Hodge filtration which we hope is easier to understand and apply. Its definition does not use resolution of singularities. Instead it relies on the theory of holonomic ~-modules in one variable with regular singularities. This paper arose from conversations at the 1980 Arbeitstagung in Bonn, where Varchenko's conjectured Hodge filtration [22] had been discussed in Brieskorn's seminar. We have since learned that Varchenko obtained similar results to those in this paper in the summer and autumn of 1980 [23-25]. In Sect. 1 the Milnor fibration is embedded in a family of smooth projective hypersurfaces. The Hodge theory of a smooth projective hypersurface is explained in the fashion of Brylinski [2] in Sect. 2. In Sect. 3 we recall the description of the Gauss-Manin system from [8]. Our new formula for the Hodge filtration is explained in Sects. 4, 5. In Sect. 6 we prove that it gives the same result as [18]. We prove a "Thom-Sebastiani" formula for the Hodge filtration in Sect. 7 which leads to a proof of conjecture (5.4) of [18]. In Sect. 8 we show how to prove Varchenko's result about the Jordan normal forms of multiplication by f in the Jacobian ring of f and the logarithm of the unipotent monodormy of f with our method. In the last chapter the mixed Hodge structure is calculated for two examples:

The effect of fluorine on viscosities in the system Na2O–Al2O3–SiO2: implications for phonolites, trachytes and rhyolites

Abstract: The effect of fluorine on melt viscosities of five compositions in the system Na2O-Al2O3- SiO2h as been investigateda t one atmospherea nd 1000-1600'Cb y concentric-cylinder viscometry. The compositions chosen were albite, jadeite and nepheline on the join NaAlOlSiO2 and two others of the join at 75 mole percent SiO2, one peralkaline and one peraluminous. All melt viscosities were independent of shear rate over two orders of magnitude, indicating Newtonian behavior. All viscosity-temperature relationships were Arrhenian within error. Fluorine reduces the viscosities and activation energies of all melts investigated. The viscosity-reducing power of fluorine increases with the SiO2 content of melts on the join NaAlO2-SiO2 and is a maximum at Na/Al (molar) = I for melts containing 75 mole percent SiO2. Fluorine and water have similar effects on aluminosilicate melt viscosities, probably due to depolymerization of these melts by replacement of Si-O-(Si, Al) bridges with Si-OH and Si-F bonds, respectively. Evidence from slag systems shows that fluorine also reduces the viscosity of depolymerized silicate melts. The viscous flow of phonolites, trachytes and rhyolites will be strongly afected by fluorine. It appears that fluorine contents of igneous rocks may be combined with water in calculation schemes for determining the viscosity of natural melts.

Non-sex hormone-binding globulin-bound testosterone as a marker for hyperandrogenism.

Abstract: Recent evidence suggests that the biologically active testosterone includes both the free and albumin-bound fractions, while the sex hormone-binding globulin (SHBG)-bound steroid dissociates less readily. To examine the significance of the non-SHBG-bound testosterone (i.e. free plus albumin bound) in hyperandrogenism, we obtained single blood samples from 17 normal women, 20 regularly menstruating but hirsute women, and 20 oligoamenorrheic hirsute women. Each serum sample was analyzed for total testosterone by RIA, SHBG-binding capacity was determined by protein precipitation with 50% saturated (NH4)2SO4, and albumin was measured by colorimetry. Non-SHBG-bound and free testosterone and the testosterone to SHBG molar ratio were then calculated. Non-SHBG-bound testosterone was also assayed using differential protein precipitation. There were significant differences among the groups in the mean values of all variables (all P less than 0.05) except albumin. Measurement and calculation of serum non-SHBG-bound testosterone produced similar results, suggesting that the binding equation is valid. There was considerable overlap between normal (control mean +/- 2 SD) and abnormal subjects in all variables except non-SHBG-bound testosterone, for which only 3 regularly menstruating and 2 oligoamenorrheic hirsute subjects were in the normal range. As total testosterone levels increased, there was a significant increase in the ratio of non-SHBG-bound testosterone to free testosterone. These data suggest that albumin becomes increasingly more important in testosterone binding as the total serum testosterone level increases and that non-SHBG-bound testosterone may be the optimal marker to identify hyperandrogenism in hirsute women.

Biogenic Structures in Outcrops and Cores. I. Approaches to Ichnology

Abstract: Fossilized traces, or trace fossils (= ichnofossils), are difficult to identify and classify phylogenetically but can be assigned relatively easily to various taxonomical, behavioural, preservational, and environmental categories. Analyses of these aspects of trace fossils, in turn, can yield information that is invaluable in sedimentary geology. The most significant contributions of trace fossils have been in paleoecology, sedimentology, and environmental reconstruction, including recognition of local and regional-temporal facies changes, patterns of bioturbation, and documentation of individual paleoecological parameters. Trace fossils are potential indicators of bathymetry, currents, food supplies, aeration, rate of deposition, depositional history, and substrate stability; to some extent, they may also be useful in establishing ancient temperature and salinity regimes. STRUCTURES BIOGENIQUES DANS LES AFFLEUREMENTS ET CAROTTES. I. APPROCHE A L'ICHNOLOGIE RESUME Les empreintes fossiles (i.e., ichnofossiles), sont difficiles a identifier et a classifier pylogenetiquement mais peuvent etre assignes relativement aisement aux differentes categories taxonomiques, de compartement biologique, de preservation et de milieux de deposition. Les analyses de ces aspects des empreintes fossils generent, a leur tour, de l'information tres importante pour le domaine de la sedimentologie. Les contributions les plus significatives des empreintes fossiles ont ete dans les secteurs de la paleoecologie, de la sedimentologie, de la reconstruction de l'environnement, incluant l'identification des changements locaux de facies, des reseaux de bioturbation, et de la documentation des parametres individuelles paleoecologiques. Les empreintes fossiles sont des indicateur potentiels de bathymetrie, de courants, de source d'approvisionnement de nutrients, d'aeration, de taux de deposition, de l'histoire de la deposition et de la stabilite des couches inferieures; jusqu'a un certain point, elles peuvent etre aussi utiles dans la determination de paleotemperatures et des paleosalinites des regimes anciens.

Stable isotope studies of cave seepage water

Abstract: D/H and 18O16O ratios for vadose seepage and precipitation were determined at three cave sites in the eastern U.S.A. Samples were collected over a period of ∼ 1 yr. between the summers of 1978 and 1979. In addition, isotopic determinations were made on a number of individual vadose seepage samples from a variety of caves predominantly located throughout North America. The results of the former portion of the study suggest that the isotopic composition of the recharge water is constant and approximately equal to that of the weighted mean annual precipitation in the locality. In the latter part of the study, the notion of the constancy of isotopic composition of vadose seepage was applied to a number of cave sites and the results agree with other precipitation data. Since it has been shown that caves record mean annual surface temperatures, the relationship between mean temperature and δ18O of precipitation can also be determined. There is good agreement between the relationship based on our data and that based on meteorological data and isotopic analyses by I.A.E.A. The study demonstrates that vadose seepage provides an effective means of assessing mean annual isotope ratios of precipitation in most continental regions.

Infrared Intensities of Liquids I: Determination of Infrared Optical and Dielectric Constants by FT-IR Using the CIRCLE ATR Cell:

Abstract: The CIRCLE ATR accessory has been used to measure the optical and dielectric constants of organic liquids and water. The method, based on Fresnel's equations, is described in detail, and the agreement between the results obtained and literature values is shown to be adequate for chemical use. The utility of optical and dielectric constants for the calculation of traditional infrared intensities in liquids and of dipole moment derivatives is outlined.

Melting of peridotite to 14 GPa and the genesis of komatiite

Abstract: It is generally accepted that the Earth's upper mantle is made of peridotite1,2. In volatile-absent conditions, partial melting of mantle peridotite close to the solidus yields a variety of basaltic melts that are progressively more olivine-normative with increasing depth3,4. At 3–4 GPa (30–40 kbar), the highest pressures so far investigated, the melts are picritic with up to 20 wt% MgO (ref. 5). Basaltic magmas that are dominant on the Earth's surface today, therefore, are considered to have been generated at relatively shallow depths ( 30 wt% MgO. Based on these results, we describe a model for the genesis of komatiite magmas by partial melting at depths of 150–200 km in the Archaean upper mantle.

The University of Alberta user interface management system

Abstract: In this paper the design and implementation of the University of Alberta user interface management system (UIMS) is discussed. This UIMS is based on the Seeheim model of user interfaces, which divides the user interface into three separate components. The Seeheim model of user interfaces is discussed along with its relationship to the design of UIMSs. The techniques used to design the three user interface components are briefly presented. A mixture of interactive and written notations are used in the design of the user interface. Some interesting features of this UIMS are interactive screen and menu layout, support for three dialogue notations, flexible interface to the application program, ability to adapt to different users, and the use of concurrent processes in user interface implementation The techniques used in the implementation of this UIMS are discussed.

Persistence in a model of three competitive populations

Abstract: A model of three competitive populations is considered. Conditions are given for the strong persistence of the system. These conditions are in terms of the existence of equilibria on the bounding coordinate planes and their stability characteristics, and are independent, in the general case, of the existence of an interior equilibrium. Some special cases are also discussed.

Personal and Situational Factors Affecting Exercise Involvement: The Importance of Enjoyment

Abstract: Interviews were conducted with continuing participants (n=51) and dropouts (n=60) from a male employee fitness program in order to investigate programmatic, personal, and social factors affecting involvement. It was found that a combination of items pertaining to reactions to the program, goals for initially joining the program, and social support for involvement in the program could effectively discriminate between the participant and dropout groups. Continuing participants scored higher than dropouts on the goals to develop recreational skills, to go out with friends, to satisfy curiosity, to release competitive drive and to develop social relationships. They also reported a greater increase in positive reactions to the program over their period of involvement in it than did the dropouts. Continuing participants rated the level of friendship within the exercise class higher and reported receiving more encouragement for involvement from their friends and work supervisor than did dropouts. Partic...

The disc of the human temporomandibular joint: design, function and failure.

Abstract: The directions and limits of mandibular movements are controlled by muscles and nerves, and by biomechanical constraints in the dentition and the temporomandibular joints with their associated ligaments. This paper analyses biomechanical constraints in relation to shape, function, stability and dysfunction of the disc in the joint. It is argued that the dense part of the disc is modelled in response to condylar forces which compress it into the articular eminence thereby thinning its centre and squeezing out a thickened anulus around its rim. Because of a lack of congruence between the two articulating surfaces of the joint and a very low coefficient of friction, the disc is potentially squeezed off the condyle by compression forces during opening, closing and mastication. It is stabilized mainly by its anulus whose thick rim is unable to prolapse between the condyle and articular eminence. An important function of the elastic tissue behind the thick part of the disc may be, by contracting, to prevent the soft tissues behind the joint being nipped between the condyle/disc/temporal bone when the jaw is closing. The author suggests that during mastication the function of the disc is not only to spread the joint forces but also to limit the depth to which the condyle is compressed into the soft tissues covering the temporal bone and thereby allow the condyle (and disc) sufficient freedom to spin and slide over the temporal bone without distorting and damaging the surfaces. In other words, the function of the disc is to destabilize the condyle. In terms of biomechanical constraints the disc seems more liable to prolapse anteriorly than posteriorly. It prolapses when the compression forces which tend to wedge it off the condyle cannot be resisted by its thickened anulus. If the energy of compression is stored within the distorted disc and suddenly released there is an audible click.

Energy costs of ion pumping by animal tissues.

Abstract: Results from recent in vitro studies indicate that in excess of 20% of the energy expenditure of skeletal muscle, duodenal epithelium and liver of domestic ruminants is to achieve Na+ and K+ transport across the plasma membrane. The energy cost of active Ca2+ transport is less clear but is likely less than 10% of the total expenditure of skeletal muscle at rest. Energy expenditure on Na+ and K+ transport was quite sensitive to the physiological state of the animal. During lactation, Na+ and K+ transport accounted for nearly half of the in vitro O2 uptake of skeletal muscle, duodenal epithelium and liver. The energetic cost of supporting Na+ and K+ transport was also elevated in young, as compared with older animals, by feed intake and by exposure to cold. Na+ and K+ transport appears to be a substantial component of the maintenance energy expenditure of ruminant tissues. Its variation, therefore, implies that change of maintenance energy expenditures with physiological state of the animal warrants serious attention.

A General Formulation of Nonequilibrium Thermo Field Dynamics

Abstract: Un cadre fondamental pour construire une theorie quantique du champ pour des systemes ouverts est etabli sur deux concepts de base: le gros grain realise par la methode de projection de la theorie de l'amortissement et l'etat thermique, concept fondamental de la dynamique des thermochamps

Defects in pulsatile LH release in normally menstruating runners.

Abstract: Intense physical exercise has been associated with reproductive dysfunction and menstrual cycles may be abnormal in a majority of women with a heavy training load. To determine whether training influenced pulsatile LH release, we measured LH pulse frequency, LH pulse amplitude and area under the curve over six hours during the early follicular phase of the menstrual cycle in four sedentary women and six eumenorrheic women runners with a training volume of at least 32 km per week. All three LH variables were significantly lower in runners than in controls. These data suggest that there is a central inhibition of the hypothalamic-pituitary-gonadal axis in eumenorrheic runners.