Showing papers by "University of Alberta published in 1974"

A Theory of Term Importance in Automatic Text Analysis

Abstract: Most existing automatic content analysis and indexing techniques are based on word frequency characteristics applied largely in an ad hoc manner. Contradictory requirements arise in this connection, in that terms exhibiting high occurence frequencies in individual documents are often useful for high recall performance (to retrieve many relevant items), whereas terms with low frequency in the whole collection are useful for high precision (to reject nonrelevant items).

Impinging Circular Turbulent Jets

Abstract: The normal impingement of turbulent circular jets on smooth walls is studied both experimentally and analytically. This type of flow can be divided into three distinct flow regions: the free-jet region; the impingement region; and the wall-jet region. The impingement region is the most important. It is shown that the impingement region occupies about 14% of the impingement height above the wall, whereas it extends about 22% of the impingement height radially. Semi-empirical methods to predict axail variations of velocity and static pressure are developed. Similarity of velocity and static pressure profiles is investigated and it is shown that these profiles are well described by the Gaussian error function. Variation of pertinent length scales are obtained empirically using dimensional analysis so that the time-averaged velocity and pressure fields in the impingement region can be predicted. A method to predict the wall shear stress in the impingement region is developed.

Effect of amendments on the microbial utilization of oil applied to soil.

Abstract: Replicate field plots comprising a control, plus oil, plus oil and bacteria, plus oil and fertilizer (urea-phosphate; 27:27:0), and plus oil, bacteria, and fertilizer were monitored over a 308-day period for changes in bacterial and mold numbers. Changes in the chemical composition of the oil applied to the plots was followed by using chromatographic techniques. Application of fertilizer resulted in a stimulation of bacterial numbers and in the rate of utilization of n-alkane components of the saturate fraction. The application of oil-utilizing bacteria, however, resulted in only a slightly accelerated rate of utilization of n-alkane components of chain lengths C20 to C25. The isoprenoids, phytane and pristane, were still present in gas-liquid chromatography profiles after digestion of the n-alkane components of the saturate fraction. Those plots which received fertilizer showed an accelerated rate of recovery of native vegetation.

Studies on Down's syndrome in tissue culture. I. Growth rates protein contents of fibroblast cultures

Abstract: Skin fibroblast cultures from six patients with Down's syndrome (Trisomy 21) were compared with four in vitro age-matched normal fibroblast cultures. Growth rates were calculated from increases in cell number and total protein during exponential growth, early in culture lifetime (less than 20 doublings). The Down's syndrome (D.S.) cultures had an average population doubling time of 35.6 ± 1.1 hours and average mass doubling time of 38.6 ± 3.2 hours, significantly lower (p<0.005) than the corresponding normal culture values of 23.0 ± 0.7 hours, and 23.3 ± 1.9 hours. D. S. Cells also contained 4.46 ± 0.19 ± 10−4 μg protein/cell as compared to 3.06 ± 0.13 × 10−4 μg/cell (p<0.001) for normal fibroblasts. Similar in vitro observations of increased doubling time and protein content have been reported in normal fibroblasts from older donors, and from individuals with premature aging syndromes, as well as in normal fibroblasts near the end of their in vitro lifetime. The present results, obtained from cultures young in vitro, may therefore suggest that D.S. fibroblast cultures age prematurely. This hypothesis is consistent with clinical manifestations of premature aging in D.S. patients and points to a defect in growth regulation, both in vivo and in vitro, resulting from an extra copy of chromosome 21.

On the foundations of biological systematics

Abstract: The foundations of systematics lie in ontology, not in subjective epistemology Systems and their elements should be distinguished from classes; only the latter are constructed from similarities The term classification should be restricted to ordering into classes; ordering according to systematic relations may be called systematization The theory of organization levels portrays the real world as a hierarchy of open systems, from energy quanta to ecosystems; followingHartmann these systems as extended in time are considered the primary units of reality Organization levels should be distinguished from levels of differentiation within each organization level Certain biological systems, such as species, continue to be misinterpreted as classes, particularly by logicians unfamiliar with modern biological theory Replacement of Aristotelian definitions of species by “polytypic” definitions achieves nothing, because species are individual systems which can be defined from an ontological viewpoint only as wholes The dispute whether classes (universals) are real per se or only in individuals is of no scientific importance; irrespective of which view is taken, any ordering of physical objects into classes constitutes an hypothesis about the structure of the real world The distinction between essential and contingent characters (attributes) is relevant only to classification There are no universal rules for evaluating characters for purposes of systematization Character statements do not form separate linear sequences The search for “unit characters” in an absolute sense is futile All real characters are reducible to relations and are in principle measurable, although there are limitations on the extent to which this can be presently achieved The concept of the sexual (“biological”) species is fundamental to theories of biosystematics Sexual species may be defined as lineages consisting at any given time of series of populations between which genetic exchange can occur and delimited in time by two successive processes of speciation Linnaean nomenclature needs modification; in its traditional form it is appropriate only to non-truncated hierarchies, whereas real phylogenies (lineages of species) form truncated hierarchies In consequence of the distinction between systematization and classification it is concluded that, while taxa may be classified into age classes or evolutionary grades, their limits as taxa (systematic units) can be no different in either case Classification into evolutionary grades remains an imprecise endeavour, since no general measure of evolutionary differentiation has been devised The spatial and temporal extent of ecosystems, the postulated basic units of ecosystematics, remains unclarified Nevertheless there are grounds for expecting progress in this field as the energetic relations between organisms become better understood Biotic communities are not “abstract” classes, but systematic units Physiognomic classification should not be confused with systematization of plant communities; both approaches contribute to an understanding of vegetational structure

The solubility of H2S and CO2 in aqueous monoethanolamine solutions

Abstract: The solubility of hydrogen sulphide and carbon dioxide, respectively, in 2.5 and 5.0 N aqueous monoethanolamine solutions has been determined at temperatures of 40°C and 100°C. Partial pressures of CO2 ranged from 0.1 to 1000 psia, while partial pressures of H2S ranged from 0.3 to 650 psia. The results have been used, together with literature data, to calculate enthalpies of solution.

Classification of Argillaceous Soils and Rocks

Abstract: A distinction is made between clays and mudstones on the basis of the loss of undrained strength of cylindrical specimens immersed freely in water. Clays are weaker at the outset and lose more of their strength more readily than mudstones. On the basis of the rate of strength reduction a further distinction can be made between hard clays and stiff clays. Many clay-shales fit into the hard-clay category. Index tests based upon the amount and rate of slaking are also presented. The amount of slaking is adequately indicated by the liquid limit. The suggested classification and index tests are supported by substantial experimental data.

Two Algorithms for Piecewise-Linear Continuous Approximation of Functions of One Variable

Abstract: Two simple heuristic algorithms for piecewise-linear approximation of functions of one variable are described. Both use a limit on the absolute value of error and strive to minimize the number of approximating segnents subject to the error limit. The first algorithm is faster and gives satisfactory results for sufficiently smooth functions. The second algorithm is not as fast but gives better approximations for less well-behaved functions. The two algorithms are ilustrated by several examples.

An improved method for obtaining axenic clones of planktonic blue‐green algae1,2

Abstract: SUMMARY Axenic clones from 5 isolates of Anabaena flosaquae, 1 isolate of Microcystis acruginosa, and 1 isolate of Aphanizomenon flos-aquae were obtained by a combination of steps that provided a 1000-fold reduction in the bacteria-algae ratio and permitted bacteria-free filaments or cells to be isolated and grown from agar pour plates. The first step consisted of the addition of phenol to a dark-treated culture to selectively reduce the numbers of actively growing bacteria while leaving the resting algal cells viable. The next steps involved washing the treated algal suspension on a Millipore filter pad or membrane followed by plating in washed agar containing buffered mineral medium plus vitamins and soil extract. The final steps consisted of incubating the agar pour plates, coring bacteria-free filaments or cells, culturing the agar cores in a buffered mineral medium, and rigorously testing the resulting cultures for bacteriological contamination. Between 50 and 90% of the cores grew, and of these about 50% were judged axenic. The method, with appropriate adaptations, should be suitable for obtaining axenic clones of other freshwater and marine algae.

Prediction of transport processes within porous media: Creeping flow relative to a fixed swarm of spherical particles

Abstract: A geometric model for an homogeneous swarm of spherical particles was introduced by us in an earlier paper and successfully employed in a theoretical investigation of diffusive transport processes occurring therein. The same geometric model is used here in a theoretical study of the hydrodynamic transport process occurring within a fixed swarm of spherical particles. The product of the application of this model to the problem of incompressible, creeping fluid flow within an homogeneous swarm of impermeable spherical particles may be regarded as a logical extension of the well-known Brinkman model; it permits physical representation and rigorous mathematical solution, yielding predictions which are in good agreement with experimental data throughout the entire porosity range. For porosities in excess of 0.7, the predictions agree closely with those obtained by means of Happel's free surface model.

Improved neuronal models for studying neural networks.

Abstract: Previous neuronal models used for the study of neural networks are considered. Equations are developed for a model which includes: 1) a normalized range of firing rates with decreased sensitivity at large excitatory or large inhibitory input levels, 2) a single rate constant for the increase in firing rate following step changes in the input, 3) one or more rate constants, as required to fit experimental data for the adaptation of firing rates to maintained inputs. Computed responses compare well with the types of neuronal responses observed experimentally. Depending on the parameters, overdamped increases and decreases, damped oscillatory or maintained oscillatory changes in firing rate are observed to step changes in the input. The integrodifferential equations describing the neuronal models can be represented by a set of first-order differential equations. Steady-state solutions for these equations can be obtained for constant inputs, as well as the stability of the solutions to small perturbations. The linear frequency response function is derived for sufficiently small time-varying inputs. The linear responses are also compared with the computed solutions for larger non-linear responses.

Quality and nutritional composition of tomato fruit as influenced by certain biochemical and physiological changes

Abstract: The chemical contituents are concerned in the quality of tomato fruit in respect to color, texture, flavor, nutritive value, and wholesomeness. In general, high sugar contents, redness of color, and firm texture are associated with prominence of rich flavor. Biochemical changes as influenced by growth, maturation, and environment of tomato fruit are discussed.

Three-Dimensional Turbulent Wall Jets

Abstract: Experiments on three-dimensional turbulent bluff wall jets originating from circular, elliptic, square, rectangular, and equilateral triangular nozzles have shown that in the region of fully-developed flow, the distribution of the axial velocity in the central as well as transverse planes is similar. The velocity scale varies inversely with the axial distance whereas the length scales vary linearly with the axial distance from the respective virtual origins. The boundary shear stress in the center line has been measured and correlated. The square root of the area of the nozzle serves as a convenient length scale in correlating the data for the nozzles of different shapes.

Cell-mediated Immunity to Herpes Simplex Virus in Man

Abstract: The immune response to herpes simplex virus was assessed by complement fixation tests, in vitro stimulation of lymphocytes, and intradermal skin tests on 63 healthy volunteers and 26 patients receiving antilymphocyte globulin (ALG) and/or adrenocorticotropic hormone. Lymphocytes from subjects with frequent recurrent herpes infections all showed significant stimulation by herpes simplex antigen, but only four of 37 without a history of previous herpes were positive. Skin tests with herpes simplex antigen demonstrated intact delayed hypersensitivity in the 10 patients tested. Lymphocyte responses to phytohemagglutinin (PHA), purified protein derivative (PPD), streptokinase, or vaccinia were similar in subjects with or without previous herpes. We were, therefore, unable to demonstrate any defect in these parameters of the immune response in patients with recurrent herpes simplex infections. Therapy with ALG totally abrogated both in vitro and in vivo evidence of cell-mediated immunity and was associated with herpes labialis in seven of the 21 courses. These infections were more severe than usual, and it may be that the cell-mediated response is more important in the localization of recurrent herpetic infections than in their prevention.

Prostaglandin-Induced Resorption of the Adult Rat Calvarium

Abstract: Prostaglandin E1-containing solutions injected under the skin overlying the calvarium of adult rats produced a visible resorptive lesion within the bone in seven days. The resorptive process was characterized by fibrous replacement of bone matrix and by increased vascularity. Inflammatory cells were not apparent.

Cutting down recursive trees

Abstract: A recursive tree is constructed by starting with a source node and repeatedly adjoining new nodes to one node of the tree already constructed. Such a tree could represent, for example, the spread of contamination from a single source within some organism. If we remove an edge from such a tree it falls into two subtrees one of which contains the source. If we continue to remove edges from the successively smaller subtrees that contain the source we eventually isolate the source. We consider how many randomly selected edges must be removed on the average before isolating the source by this procedure.

Taylor's Pig-Tale: A Historical Analysis of Frederick W. Taylor's Pig-iron Experiments

Abstract: Frederick Taylor is cited as the father of scientific management. His account of the loading of pig-iron has been accepted virtually without question. An investigation of that story reveals it to b...

Regeneration Electrode Units: Implants for Recording from Single Peripheral Nerve Fibers in Freely Moving Animals

Abstract: Implantable electrode assemblies that become penetrated by regenerating axons were used to record signals from single sensory and motor nerve fibers associated with leg movement in unrestrained amphibians (Xenopus laevis). Such neuroimplants may provide a means for establishing the roles of various muscle afferents and efferents in posture and locomotion, and have potential clinical applications.