Showing papers by "University of Alberta published in 1976"

On the cause and characteristic scales of meandering and braiding in rivers

Abstract: A stability analysis of meandering and braiding perturbations in a model alluvial river is described. A perturbation technique, involving a small parameter representing the ratio of sediment transport to water transport, is used to obtain the following results.Under appropriate conditions, the existence of sediment transport and friction are necessary conditions for the occurrence of instability in the flow and on the bed; thus instability is not inherent in the flow alone. An Anderson-type scale relation for longitudinal instability is obtained for meandering. A relation estimating the number of braids and differentiating between meandering and braided regimes is derived. These relations are independent of sediment transport.

The role of cutaneous afferents from the distal hindlimb in the regulation of the step cycle of thalamic cats

Abstract: The pad and the plantar surface of the foot were stimulated electrically in thalamic cats. Weak stimulation evoked an extensor reflex in the animal at rest. The same stimuli in a spontaneously walking animal applied during the stance phase produced an increase both in amplitude and duration of the ongoing extensor activity. When given during the swing phase, the stimuli either prolonged the ongoing flexor activity and/or shortened the following extensor burst. These changes in flexor and extensor burst duration were reflected in changes in the step cycle duration. Similar results were seen with direct stimulation of the sural nerve. For the latter experiments the ipsilateral hindlimb was fixed and denervated except for the ankle extensors and flexors, which showed rhythmic contractions correlated normally with the walking movements of the three remaining limbs. At rest, threshold stimulation of the sural nerve evoked a reflex contraction in the triceps surae of the fixed leg. The same stimuli applied during the contraction phase of the fixed triceps surae during walking resulted in a larger and longer extensor contraction and a delay of the following flexion. Stimulation during the relaxation phase of the fixed triceps surae reduced the duration of the following contraction phase. The findings are discussed in relation to the possible role of cutaneous input during locomotion.

Tremor and other oscillations in neuromuscular systems.

Abstract: A model has been analyzed which is based on recent experimental evidence concerning the properties of muscles and the sensory feedback pathways from muscles. Damped oscillations can arise in the absence of sensory feedback due to the interaction of a muscle with inertial loads. These mechanical oscillations can have a wide range of frequencies depending on the inertial and elastic loads that are attached to the muscle. Small amounts of sensory feedback will tend to reduce deviations from a steady muscle length, but larger amounts of feedback can produce oscillations. The frequency of these reflex oscillations is determined by the properties of the muscle and feedback pathway, and is rather independent of load. If the strength of the sensory feedback is sufficient, either the mechanical oscillations or the reflex oscillations or both can grow, rather than decay, with time. The growth of these oscillations is limited by saturation non-linearities in the muscle receptors and the muscle itself, so that the oscillations approach a steady amplitude and frequency. Using typical properties of muscles and spinal reflex pathways, the frequency of reflex oscillations will be within the range 8–12 Hz found for physiological tremor. With the longer latency found for supraspinal reflexes, oscillations will occur in the range 4–6 Hz which is characteristic of Parkinson's and cerebellar diseases. The role of longer latency reflexes in the generation of these tremors is discussed.

Factors Influencing Innovation Success at the Project Level

Abstract: (1976). Factors Influencing Innovation Success at the Project Level. Research Management: Vol. 19, No. 3, pp. 15-20.

Substituent Effect on the Oxidation of Phenols and Aromatic Amines by Horseradish Peroxidase Compound I

Abstract: A stopped-flow kinetic study shows that the reduction rate of horseradish peroxidase compound I by phenols and aromatic amines is greatly dependent upon the substituent effect on the benzene ring. Moreover it has been possible to relate the reduction rate constants with the ionization constants of monosubstitutcd substrates by a linear free-energy relationship (Hammett equation). The correlation of log (rate constants) with σ values (Hammett equation) and the absence of correlation with σ+ values (Okatnoto-Brown equation) can be explained by a mechanism of aromatic substrate oxidations, in which the substrate gives an electron to the enzyme compound I and simultaneously loses a proton. The analogy which has been made with oxidation potentials of phenols or anilines strengthens the view that the reaction is only dependent on the relative ease of oxidation of the substrate. The rate constant obtained for p-aminophenol indicates that a value of 2.3 × 108 M−1 s−1probably approaches the diffusion-controlled limit for a bimolecular reaction involving compound I and an aromatic substrate.

The estimation of sex on the basis of the talus and calcaneus

Abstract: The present report records and describes sexual dimorphism of the talus and calcaneus in American Blacks and Whites from the Terry Collection housed in the Smithsonian Institution, Washington, D.C. The greater amount of sexual dimorphism was observed in the talus, where 81 percent of the study sample could be accurately sexed. Four discriminant functions based on measurements from the talus and/or the calcaneus allowed sexing 79 to 89% of the study sample accurately. The techniques developed were then applied to two North American Indian samples, and sex of the individuals in these samples was assessed with the same degree of accuracy.

Function of Segmental Reflexes in the Control of Stepping in Cockroaches and Cats

Abstract: The reflex mechanisms controlling stepping in the cockroach and cat have been compared in an attempt to identify common functional reflexes in the control of terrestrial walking. The main question examined was: what initiates the transition from stance to swing in a single limb? In both animals it has been found that blocking leg extension during the stance phase inhibits the rhythmic movements of that leg but not the rhythm in the other legs. Allowing the blocked leg to extend slowly eventually leads to the initiation of swing. Two mechanisms could explain these observations: 1) the activity in receptors signalling the position of the limb at the transition point causes the switch from stance to swing, and 2) as the leg is extended the load carried by that leg is reduced and decreased activity in receptors detecting the load causes the initiation of swing. In the cat the hip angle at the end of stance remains constant in a variety of behavioural situations, indicating that the signal for swing initiation originates from hip position afferents (mechanism 1). For the cockroach it has been found that activity in cuticular stress receptors (campaniform sensilla) during stance inhibits the system responsible for producing swing. Thus swing is initiated when the inhibition of the swing generating system by load receptors is reduced (mechanism 2).

The Grampian Orogeny

Abstract: Synopsis Review of existing plate tectonic theories of the Lower Palaeozoic development of the north and northwest British Isles leads to the conclusion that ridge-trench impingement theory can be used to integrate all known geological observations within one unified plate tectonic theory for the area. Consideration of the consequences of the progressive impingement of a ridge-transform system with a northwesterly-dipping subduction zone in Arenig time gives explanations for: (a) termination of Dalradian sedimentation in the Arenig; (b) initiation of Barrovian metamorphism at the same time; (c) development and history of the Girvan-Ballantrae complex; (d) initiation of the Highland Boundary Fault as a dextral transform fault in the Arenig; (e) its absence in western Scotland; (f) the postulated presence of a boundary fault southeast of Connemara and perhaps at Pomeroy; (g) the peak of metamorphism (Barrovian and Buchan types) in the Dalradian and associated basic intrusions in the Arenig in both Scotland and Connemara; (h) the development of the Moine Thrust (and related foreland folds and thrusts) also in the Arenig and (i) the origin of the South Mayo trough on oceanic crust. Related events explained by this model include the location of the Donegal batholith, the generally low-grade metamorphism of Donegal and southwest Scotland, the location of the Great Glen Fault and all known faunal province and Ordovician sedimentological data from the Midland Valley and Southern Uplands. It is proposed that this Lower Ordovician sequence of related events be termed the Grampian Orogeny, distinct from the later Caledonian Orogeny, which is tectonically and geographically separate.

Simultaneous and backward fear conditioning as a function of number of CS-UCS pairings.

Abstract: Four experiments examined the possibility that the outcome of simultaneous and backward fear conditioning procedures might depend upon the number of CS-UCS pairings A punishment procedure will rats as subjects and shock as the UCS was used; the amount of suppression produced by response-contingent CS presentations indexed the strength of acquired fear Experiments 1, 3, and 4 examined the suppressive tendencies of simultaneous-and backward-trained CSs after 0, 10, 20, 40, 80, and 160 pairings The pattern of data suggested that initial pairings have the effect of increasing suppressive tendencies of the CS, while subsequent pairings decrease them In addition, evidence of fear inhibition was found after 160 pairings in the case of the backward paradigm Experiment 2 examined several nonassociative accounts based upon differential shock exposure Groups given 10 pairings or 80 pairings were compared to ggroups given 10 pairings plus 70 shock-alone presentations The results indicated that number of pairings, rather than number of UCS occurrences, is the important factor in decreasing the initial suppression The evidence for eventual inhibition in the backward paradigm suggests that this occurs through the acquisition of inhibitory tendencies which are antagonistic to the previously conditioned excitation

Precision Weighting—An Effective Automatic Indexing Method

Abstract: A great many automatic indexing methods have been implemented and evaluated over the last few years, and automatic procedures comparable in effectiveness to conventional manual ones are now easy to generate Two drawbacks of the available automatic indexing methods are the absence of reliable linguistic inputs during the indexing process and the lack of formal, analytical proofs concerning the effectiveness of the proposed methods The precision weighting procedure described in the present study uses relevance criteria to weight the terms occurring in user queries as a function of the balance between relevant and nonrelevant documents in which these terms occur; this approximates a semantic know-how of term importance Formal mathematical proofs are given under well-defined conditions of the effectiveness of the method

Proliferation of Murine Thymic Lymphocytes in Vitro Is Mediated by the Concanavalin A-Induced Release of a Lymphokine (Costimulator)

Abstract: Mitogen-induced proliferation of lymphocytes may in theory result directly from the interaction of mitogen with the cells, or indirectly as a result of the mitogen-stimulated release of lymphokines. In the case of murine thymic lymphocytes exposed to concanavalin A (Con A) in tissue culture, we have determined that mitogenesis depends upon a lymphokine. Interaction of the thymic lymphocytes with lectin is necessary, but not sufficient, for mitogenesis. A lymphokine, or costimulator for mitogenesis, is released by normal spleen or thymus cells during the first 16 hr of their exposure to Con A, and in the presence of a phytomitogen it stimulates thymic mitogenesis. Under conditions of low costimulator levels, no mitogenesis follows the interaction of Con A with cells. The response of adult CBA/J mouse thymocytes to phytohemagglutinin (PHA) is very low, compared to their response to Con A. When costimulator is added to PHA, the cells respond as well as they do to Con A. Costimulator does not act through Con A-binding sites on thymus cells. Its production is dependent on both cells carrying omega surface antigen (T lymphocytes) and adherent cells of the macrophage-monocyte series. The adherent population, but not the T cells, may be heavily irradiated without affecting production of costimulator. Costimulator is not a mitogen on its own.

Streptomycin Accumulation in Susceptible and Resistant Strains of Escherichia coli and Pseudomonas aeruginosa

Abstract: Streptomycin accumulation by susceptible strains of Escherichia coli and Pseudomonas aeruginosa has been shown to be prevented or inhibited by inhibitors of electron transport, sulfhydryl groups and protein synthesis, and agents that uncouple oxidative phosphorylation. Streptomycin is recovered from cells in an unchanged form and is intracellularly concentrated above extracellular concentrations. Accumulation kinetics are multiphasic; an initial phase which cannot be prevented by the above inhibitors is unable to cause inhibition of cell growth or loss of cell viability. Prevention of further phases of uptake does prevent these events. Inhibitor-susceptible accumulation is time dependent and begins almost immediately upon exposure of cells to streptomycin. Streptomycin accumulation remains energy dependent even when cells are losing acid-soluble [(3)H]adenine, presumably through loss of permeability control. These results demonstrate that streptomycin accumulation necessary for inhibition of cell growth or cell death requires energy and is not a process of diffusion or secondary to membrane leakage. Streptomycin accumulation in ribosomally resistant mutants of E. coli and P. aeruginosa is similar in that both energy-independent and energy-dependent accumulation can be demonstrated. The total energy-dependent accumulation is, however, significantly lower than that in streptomycin-susceptible cells due to the absence of an additional energy-dependent phase of accumulation, which seems dependent on ribosomal binding of streptomycin. Ribosomally resistant strains can be shown to concentrate streptomycin accumulated by the energy-dependent process above the external concentration in nutrient broth but not in Trypticase soy broth. The energy-dependent accumulation can be saturated in the Str(r) strain of E. coli in nutrient broth, implying limited accumulation sites.

Questions and question asking in verbal discourse: A cross-disciplinary review.

Abstract: The linguistic, psychological, and social aspects of questions and question asking in verbal discourse are discussed. Classification taxonomies for question forms and functions are outlined. Research on the processes of question formation, question selection, and question asking is reviewed. Descriptive data for the occurence of question types in verbal discourse are presented. Suggestions are made concerning further descriptive and experimental approaches to the study of questions.

"In General" vs. "It Depends": Some Comments of the Gergen-Schlenker Debate

Abstract: This is the Cybernetics and Stuff That covered Chaotic Confusion and Bluff That hung on the Turn of a Plausible Phrase And Thickened the Erudite Verbal Haze Cloaking Constant K That saved the Summary Based on the Mummery Hiding the Flaw That lay in the theory Jack built. (Winsor & Parry, 1958, Poem 30)

Two and three phase equilibrium calculations for systems containing water

Abstract: A recently proposed two-constant equation of state is used to predict the phase behaviour of systems exhibiting a water-rich liquid phase, a hydrocarbon-rich liquid phase and a vapor phase. The algorithm proposed is efficient and thermodynamically rigorous and it converges significantly faster than earlier models. Representative calculations are shown for the methane-n butane water system, the n butane-1 butane-water system, and a synthetic six-component hydrocarbon mixture containing waer. On emploie une equation d'etat a deux constantes, qui a ete proposee recemment, pour prevoir le comportement des phases de systemes impliquant une phase liquide riche en eau, une phase liquide riche en hydrocarbure et une phase vapeur. L'algorithme propose est efficace et rigoreux au point de vue thermodynamique; il converge bien plus vite que ne le font des modeles anterieurs. On presente des calculs representatifs pour les deux systemes methane-butane normal-eau et butane normal-butene 1-eau, ainsi que pour un melange d'hydrocarbures dont six composants sont synthetiques et qui contient de l'eau.

Covariant Newtonian limit of Lorentz space-times

Abstract: The formulation of this limit given by Dautcourt [1] is slightly improved using the notions of Galilei manifold and Newtonian connection. It is then shown under what conditions the conservation equations ▽μ μα = 0 for an arbitrary relativistic continuum have the correct (also covariantly formulated) Newtonian limit. For electromagnetism one obtains a curved space generalization of the electric or magnetic Galileian theory of LeBellac and Levy-Leblond [4] depending on whether the contravariant or the covariant Maxwell tensor is required to have a regular Galileian limit.

Sea Anemone Reproduction: Patterns and Adaptive Radiations

Abstract: It is known that sea anemones (Anthozoa: Actinaria) are capable of reproducing in a variety of ways both sexually and asexually (Stephenson, 1928; Hyman, 1940; Uchida and Yamada, 1968). Even in the same species the mode of reproduction may differ from population to population (Schmidt, 1967; Rossi, 1975; personal observations). The versatility of reproduction can, perhaps, be best illustrated by Stephenson’s comment (1928): “... breeding, from our imperfect knowledge of it, would appear to be erratic, the individual being a law unto itself.”

Climatic information from 18 O/ 16 O ratios of cellulose in tree rings

Abstract: THE high precision of dendrochronology makes possible the construction of short (∼ 9,000 yr), detailed records of past climates. This paper explores the possibility of using the oxygen isotopic composition of cellulose from tree rings as a ‘thermometer’ to measure past temperatures. Using meteorological data from Edmonton we have shown that temperatures can be measured with a precision of ∼ ±0.15°C when averaged over a 5-yr period.

The use of Langmuir probes in the study of high pressure plasmas

Abstract: The theory of d.c. and transient probes in stationary and moving plasmas is discussed. The success (or otherwise) of theory in explaining experimental results obtained by many researchers working over a wide range of conditions is noted with the aim of enabling some assessment to be made of the feasibility of carrying out a given probe measurement.

Graphical stability, enrichment, and pest control by a natural enemy

Abstract: A two-dimensional mathematical model for predator-prey interactions is proposed. Stability of the equilibrium is examined in the light of a graphical method of Rosenzweig and MacArther. A second graphical method is also discussed. The phase-plane behavior of the model is analyzed. A perturbed form of the model is introduced, and its relation to pest control is discussed. In varying the carrying capacity, the relation to enrichment is analyzed. In addition the stabilizing effects due to the addition of a source term are noted.

Possible Limits on a Science of Social Behavior

Abstract: About a quarter of a century ago Edmund Whittaker (1949) wrote a fascinating series of lectures on the history and implications of recent developments in theoretical physics. Almost parenthetically, he outlined therein a means of viewing scientific progress which is at once both unorthodox and profound. It is a means founded on what Whittaker terms “postulates of impotence,” which he defines as assertions of “… the impossibility of achieving something, even though there may be an infinite number of ways of trying to achieve it.” He continues: A postulate of impotence is not the direct result of an experiment or of any finite number of experiments; it does not mention any measurement, or any numerical relation or analytical equation; it is the assertion of a conviction that all attempts to do a certain thing, however made, are bound to fail. (p. 59)

Characteristics of Photodiode Arrays for Spectrochemical Measurements

Abstract: A rather large number of spectrochemical studies and analyses can be greatly facilitated by the simultaneous measurement of spectral information over a range of wavelengths. Of particular importance and interest to analytical spectroscopists is the development of simultaneous multielement analysis systems. The development and implementation of such analyses have been hampered by a lack of convenient and versatile multichannel spectrochemical measurement systems. New detector subsystems based on modern electronic image sensors are helping to overcome this obstacle. One type of electronic image sensor is the self-scanning linear array of silicon photodiodes. These arrays are available with densities of 1024 photodiodes per in and in lengths of up to 1 in. They are packaged in conventional dual-in-line integrated circuit packages complete with the necessary scanning circuitry. These sensors have simple and inexpensive control and measurement circuitry, and superior blooming and lag performance when compared to most other electronic image sensors. In addition, the signal integrating capability of the arrays is a flexible and powerful asset for many spectrochemical measurements. These and other operational characteristics of photodiode arrays are emphasized in this study. In addition, the measurement capability of a computer coupled photodiode array spectrometer based on a 1024 element array which is capable of simultaneously measuring over 50 nm (500 A) of continuous spectral information anywhere from 200 to 1000 nm is illustrated.

Spontaneous mutation by mutagenic repair of spontaneous lesions in DNA

Abstract: Strains of yeast carrying mutations in many of the steps in pathways repairing radiation-induced damage to DNA have enhanced spontaneous mutation rates. Most strains isolated because they have enhanced spontaneous mutation carry mutations in DNA repair systems. This suggests that much spontaneous mutation arises by mutagenic repair of spontaneous lesions.