Showing papers by "University of British Columbia published in 1976"

Knots and Links

Abstract: Introduction Codimension one and other matters The fundamental group Three-dimensional PL geometry Seifert surfaces Finite cyclic coverings and the torsion invariants Infinite cyclic coverings and the Alexander invariant Matrix invariants 3-manifolds and surgery on links Foliations, branched covers, fibrations and so on A higher-dimensional sampler Covering spaces and some algebra in a nutshell Dehn's lemma and the loop theorem Table of knots and links References Index.

Duplication of biochemical changes of Huntington's chorea by intrastriatal injections of glutamic and kainic acids

Abstract: SYSTEMIC administration of large doses of L-glutamate to immature animals causes degeneration of neurones in the retina and the arcuate nucleus. Olney et al.1 reported that intracerebral injections of the more potent excitatory analogues of glutamate, in particular kainic acid, caused rapid degeneration of certain dendritic and somal structures in the injected area. Presumably the degeneration is related to the ability to bind the ‘excitotoxic’ agent, with necrosis resulting from a sustained increase in membrane permeability. 3H-kainic acid binds more strongly to striatal tissue than to any other area of rat brain tested2. This lends some support to Spencer's theory3—based on antagonism of cortical excitation of striatal neurones by diethyl glutamate—that the massive corticostriatal pathway is glutaminergic. If Huntington's chorea were an excitotoxic phenomenon resulting from chronic overstimulation of glutamate receptors, striatal neurones in particular would be affected because of heavy glutaminergic input. This hypothesis is not readily tested by simple measurement of glutamate in choreic tissue because glutamate is a precursor of γ-aminobutyric acid (GABA) and is also involved in other metabolic activities. As one potential test of this hypothesis, we have injected 1 µl of either kainic acid or L-glutamic acid dissolved in isotonic saline directly into the extrapyramidal nuclei of rats. Injection into the striatum produced local enzymatic changes duplicating those reported in Huntington's chorea.

Classification of knee ligament instabilities. Part II. The lateral compartment.

Abstract: Lateral instability of the knee is less frequent but more disabling than medial instability of a comparable amount. At the same time the diagnostic tests for lateral instability are more subtle and more frequently misinterpreted. Posterolateral rotatory subluxation is demonstrated by an apparently positive posterior drawer test with the tibia in neutral rotation or by the external rotation-recurvatum test with the knee in extension. Anterolateral rotatory subluxation is present when the anterior drawer test with the tibia in neutral rotation demonstrates that the lateral tibial condyle appears to become more prominent or that both condyles appear to become equally prominent.

The distinction between canopy and boundary‐layer urban heat islands

Abstract: Air temperature measurements from car traverses in and near Vancouver, BC are used to test two urban heat island models: one an empirical model, the other a theoretical advective model The empirical model describes the Vancouver observations well, whereas the advective one performs rather poorly This discrepancy may be attributed to a failure to distinguish between meteorological conditions in the urban canopy, and those in the overlying urban boundary layer This leads to a reassessment of the explanation of the relationship between city size (as measured by population) and the heat island intensity (as measured in the urban canopy)

A New Approach to Lagrange Multipliers

Abstract: We consider a mathematical programming problem on a Banach space, and we derive necessary conditions for optimality in Lagrange multiplier form. We prove further that “most mathematical programming problems are normal.” The novelty of our approach lies on the one hand in the absence of both differentiability and convexity hypotheses on the functions delimiting the problem, and on the other hand in the method of proof, which is new. The approach unifies the well-known smooth and convex cases besides treating a new general class of problems. The main analytical tool in this paper is an extension to infinite-dimensional spaces of the “generalized gradient” previously introduced by the author. The calculus of the generalized gradient is explored as a preliminary step.

Source shape estimation and deconvolution of teleseismic bodywaves

Abstract: We consider the deconvolution of a suite of teleseismic recordings of the same event in order to separate source and transmission path phenomena. The assumption of source uniformity may restrict the range of muths and distances of the seismograms included in the suite. The source shape is estimated by separately averaging the log amplitude spectra and the phase spectra of the recordings. This method of source estimation uses the redundant source information contained in secondary arrivals. The necessary condition for this estimator to resolve the source wavelet is that the travel times of the various secondary arrivals be evenly distributed with respect to the initial arrivals. The subsequent deconvolution of the seismograms is carried out by spectral division with two modifications. The first is the introduction of a minimum allowable source spectral amplitude termed the waterlevel. This parameter constrains the gain of the deconvolution filter in regions where the seismogram has little or no information, and also trades-off arrival time resolution with arrival amplitude resolution. The second modification, designed to increase the time domain resolution of the deconvolution, is the extension of the frequency range of the transmission path impulse response spectrum beyond the optimal passband (the passband of the seismograms). The justification for the extension lies in the fact that the impulse response of the transmission path is itself a series of impulses which means its spectrum is not band-limited. Thus, the impulse response is best represented by a continuous spectrum rather than one which is set to zero outside the optimal passband. This continuity is achieved by a recursive application of a unit-step prediction operator determined by Burg's maximum entropy algorithm. The envelopes of the deconvolution are used to detect the presence of phase shifted arrivals.

Some results on generalized difference estimation and generalized regression estimation for finite populations

Abstract: Let S = {s} be the set of subsets of {1, , N} such that each s eS contains n elements We consider in this paper only designs p(s) with fixed sample size, that is P(S) > 0 only if s eS and ESp(s) = 1, where Es denotes summation over s eS Let p(s) be independent of the Yk, where Yk is the value of the variable of interest for the population unit labelled k (k = 1, , N) We consider a superpopulation model: Yl, , YN is a realization of Y1, ,YN with joint distribution 6 If d( ) denotes expectationwith respect to 6, let, for k, I = 1, , N, 6 be further specified by

Decreased intracranial self-stimulation after neuroleptics or 6-hydroxydopamine: evidence for mediation by motor deficits rather than by reduced reward.

Abstract: Rats were implanted with electrodes in the lateral hypothalamus, put on a 22-h food deprivation schedule and trained to bar-press for ICS and for food on a CRF schedule. Haloperidol (0.08 mg/kg) and pimozide (0.22 mg/kg) significantly decreased responding for both reinforcers, although responding for ICS was decreased more than it was for food. The same doses of these drugs did not decrease food consumption on a 15-min ad libitum test after 22-h of food deprivation, suggesting that the decreased bar-pressing for food was not the result of anorexia or reduced motivation for food. When similar rates of responding for ICS and for food were obtained on a V1 60 schedule, haloperidol (0.1 mg/kg) reduced responding for food and ICS to a similar extent. Thus, when baseline rate is controlled for, neuroleptics do not selectively reduce responding for ICS. In addition, examination of cumulative response records revealed that rather than producing an extinction curve, as would be predicted if neuroleptics reduced the rewarding properties of ICS, haloperidol produced a uniform decrease in the rate of responding throughout the experimental session. Similar results were obtained with intraventricular 6-hydroxydopamine (6-OHDA) injections. While these experiments do not exclude the possibility that dopaminergic (DA) systems participate in some central reinforcement mechanisms, they suggest that neuroleptics and 6-OHDA decrease responding for food or ICS primarily by impairing the function of DA systems critically involved in the initiation or maintenance of operant behaviour rather than by interfering with reward.

A k-sample significance test for independent alpha coefficients

Abstract: The earlier two-sample procedure of Feldt [1969] for comparing independent alpha reliability coefficients is extended to the case ofK ≥ 2 independent samples. Details of a normalization of the statistic under consideration are presented, leading to computational procedures for the overallK-group significance test and accompanying multiple comparisons. Results based on computer simulation methods are presented, demonstrating that the procedures control Type I error adequately. The results of a power comparison of the case ofK=2 with Feldt's [1969]F test are also presented. The differences in power were negligible. Some final observations, along with suggestions for further research, are noted.

The insulinotropic action of gastric inhibitory polypeptide in the perfused isolated rat pancreas.

Abstract: Gastric inhibitory polypeptide (GIP) produced a dose-related increase in immunoreactive insulin (IRI) from the perfused isolated rat pancreas. The doses employed were within physiological limits. This effect was glucose-concentration-dependent in that there existed a threshold concentration of glucose above which GIP exerted the insulinotropic action, and that, at a fixed concentration of GIP, increased glucose concentrations stimulated IRI release in more than an additive manner. A biologically active fragment of the GIP molecule was isolated and purified. All criteria have been satisfied that GIP is an insulinotropic hormone.

The Physiological Ecology of Mytilus californianus Conrad. 1. Metabolism and Energy Balance

Abstract: Mytilus californianus regulated its rate of oxygen consumption (VO2) during decline in oxygen tension, but did not acclimate VO2 when held at 58 mm Hg PO2. In spite of a capacity to consume oxygen while exposed to air (the average VO2 in air being equivalent to 0.74xthe standard rate of oxygen consumption in water), these mussels acquired an “oxygen debt” during aerial exposure which was discharged on subsequent reimmersion. During exposure to air the oxygen tension of the fluid in the mantle cavity was rapdly reduced to approximately 40 mm Hg, in animals both in the laboratory and on the shore. Heart rate was also reduced during air exposure, though not to the point of cardiac arrest. The concentration of ammonia in the fluid of the mantle cavity increased during aerial exposure, but the rate of excretion of ammonia was much lower than during immersion. Observations of mussels on the shore at low tide indicated that dehydration of the tissues was not a serious threat, possibly due to the large volume of fluid retained in the mantle cavity. During aerial exposure some end-products of anaerobic metabolism (alanine and malate) accumulated in the posterior adductor muscle. Malate accumulation was rapid during the first hour of exposure; alanine accumulated more gradually. It is concluded that during aerial exposure M. californianus resorts to anaerobiosis in spite of a capacity to extract some oxygen from the atmosphere. This results in a metabolic deficit during each period of low tide which, coupled with the reduced time available for feeding, imposes a physiological stress on mussels distributed on the shore.

Darwin's finches: population variation and natural selection

Abstract: Van Valen's model, which relates morphological variation to ecological variation in an adaptive scheme, was investigated with individually marked and measured Darwin's finches on two adjacent Galapagos islands, Santa Cruz and Daphne Major. Results show that environmental heterogeneity is correlated with large continuous, morphological variation: variation in bill dimensions of Geospiza fortis is greater on Santa Cruz than on Daphne, as is environmental heterogeneity. Within populations of this species, different phenotypes distribute themselves in different habitat patches, select foods of different sizes and hardness, and exploit them with efficiencies that are phenotype- (bill size) dependent. These data constitute indirect evidence that natural selection has a controlling influence over the level of phenotypic variation exhibited by a population. Further evidence is that phenotypes did not survive equally well during the study period; on Daphne island G. fortis was apparently subjected to directional selection on bill tip length and G. scandens to normalizing selection on body weight and bill depth. Other factors which may have contributed to the establishment of a difference in variation between Santa Cruz and Daphne populations are the founder effect, genetic drift, and assortative mating. Annual climatic unpredictability is considered a source of environmental heterogeneity which, through its effect upon food supply, favors large morphological variation. It is predicted that species of large individual size are more influenced by this than are small species, and consequently exhibit greater size-corrected variation. The prediction is tested with data from six Geospiza species, and found to be correct.

A delayed-recruitment model of population dynamics, with an application to baleen whale populations.

Abstract: This paper studies the delay equation x k+1=λx k+F(x k−β), which has been employed as a model of baleen whale population dynamics. The two main questions discussed are (a) stability of equilibria, and (b) optimal exploitation policies.

Classification and Analysis of River Processes

Abstract: Aerial photographs and brief field visits are frequently the only data sources for the preliminary design of river engineering works in romote or undeveloped areas. Even if short-term field data are available, they may be misleading because of the nonuniform rates at which river processes take place. The major active processes are, however, reflected in the river morphology so that correct classification and interpretation of channel, flood-plain, and terrace features on maps and photographs can, to some degree, overcome a lack of long-term data. Rivers present a wide spectrum of intermediate forms between the familiar classic braided and meandering types. This reflects a similarly wide spectrum of flow distribution, bed material size, sediment transport, and channel stability. Existing river classification schemes are reviewed and a modified system is proposed to take account of the gradual transition between classical types.

A framework for social motives.

Abstract: In any complex social system, the choices of a single person often affect the outcomes of others. When one takes the others' outcomes into account in making choices, we say one is manifesting a social motive. We assume that an individual's social motives are manifested in his social preferences. Any theory of decision or choice requires information about preferences, and so in addition to attempting to clarify definitions of social motives, this study provides a framework for theories of social decision. To begin, we establish operational definitions for the motives of self-interest, self-sacrifice, altruism, aggression, cooperation, and competition. These definitions are based on the simple operators of summations and differences. Then we examine some supplementary motives involving proportionality operators. Next we eliminate the assumption that an individual has a fixed preference structure which is applied to all social choices. This leads to a focus on the specific distribution of consequences resulting in conditional motives; conditional motives reflect varying basic motives depending on whether the individual is ahead or behind. All these motives are represented graphically, and a correspondence matrix is given to illustrate the interrelationships among the motives. Finally, we investigate combinations of the motives since such composites are less restrictive and can better account for observed behavior. Linear combinations are interesting but still too restrictive. Conjunctive, disjunctive and lexicographic combinations offer useful possibilities for characterizing particular social motives. Complex combinations involving general nonlinear forms arise and some representative forms are explored.

Factors affecting the canopy resistance of a Douglas-fir forest

Abstract: The physiological nature of canopy resistance was studied by comparing the stomatal and canopy resistance of a 10-m high Douglas-fir forest. Stomatal resistance of the needles was measured using porometry, while the canopy resistance was calculated using energy balance/Bowen ratio measurements of evapotranspiration. A typical steady increase in the forest canopy resistance during daytime hours, even at high soil water potentials, was observed. A similar trend in the stomatal resistance indicated that increasing canopy resistance during the daytime was caused by gradually closing stomata. During a dry period when soil water potentials declined from 0 to −10.5 bars, the mean daytime value of canopy resistance increased in proportion to the mean daytime value of the stomatal resistance. Values of canopy resistance calculated from stomatal resistance and leaf area index measurements agreed well with those calculated from energy balance measurements. The dependences of stomatal resistance on light, vapour pressure deficit, twig and soil water potentials art summarized.

Mutagaenic action of ascorbic acid

Abstract: MICROBIAL1, mammalian2,3 and human4,5 bioassays are being applied to uncover the mutagenic action of synthetic compounds which have been introduced accidently or intentionally into the environment. Somewhat less attention has been given to the potential genetic hazard of chemicals which are an essential part of human nutrition or are formed within mammalian tissues and organs. Ascorbic acid belongs to this group of “neglected” naturally occurring compounds, although its capacity to form radicals and its interaction with viral6 and bacterial7 DNA should have raised suspicion about its possible mutagenic capacity. Considering the large daily intake of ascorbic acid, its addition to many food products8 and its potential use as an inhibitor of the intragastric formation of N-nitroso compounds8,9 and nitrosamine formation in food products10, its action on the genome of human cells requires investigation. We here present evidence, from several experimental systems, suggesting that vitamin C, particularly in the presence of copper, has a mutagenic effect.

Flagellate Phylogeny: A Study in Conflicts*

Abstract: SYNOPSIS. Information relating to the ultrastructure of 4 organellar systems of flagellates—nuclei (including mitosis), flagella, mitochondria and chloroplasts—is examined for bearing on the probable phylogeny of the principal flagellate groups, first considered singly and then in combination. The mitotic mechanism has not proved to be as conservative a character as might be hoped, but still remains characteristic for the average condition in many of the groups. Flagellar features are useful if allowance is made for the reduction or multiplication of the basic pair, and the loss of lateral and terminal hairs seems to have occurred independently several times. The presence of paraxial rods within flagella may be a useful indication of affinity. Rootlet systems are not dealt with in detail here, although the possible similarity between axial microtubular sheets in axostylar flagellates and some members of the green algae containing “manchettes” is noted. The basic patterns of chloroplast internal structure are summarized and their general agreement with other characters is affirmed, noting however that cryptomonads may be closer to the green flagellates (including euglenoids) than is generally accepted. Attention is drawn to the potential value of internal mitochondrial morphology as an indicator of large assemblages. Finally, a “tree” based on multiple cell organizational features is presented and discussed.