Science
Permanent URI for this community
Researchers in the Faculty of Science are involved in an impressive variety of fields – from astrophysics to zoology, nanotechnology to virtual reality, metabolomics to mathematics and much more!
In all cases, our faculty researchers, post-doctoral fellows, and graduate and undergraduate students live up to the highest standards in their disciplines, seeking to expand human knowledge through curiosity, innovation, and discovery.
Browse
Browsing Science by Issue Date
Now showing 1 - 20 of 1834
Results Per Page
Sort Options
- ItemOpen AccessTwo exceptionally preserved juvenile specimens of Gorgosaurus libratus (Tyrannosauridae, Albertosaurinae) provide new insight into the timing of ontogenetic changes in tyrannosaurids(Journal of Vertebrate Paleontology (Taylor and Francis), 0022-04-13) Voris, Jared. T.; Zelenitsky, Darla K.; Therrien, Francois; Ridgely, Ryan C.; Currie, Philip J.; Witmer, Lawrence, M.Known from dozens of specimens discovered since the early 20th century, Gorgosaurus libratus has arguably contributed more than any other taxon to our understanding of the life history of tyrannosaurids. However, juvenile material for this taxon is rare. Here, we describe two small, articulated Gorgosaurus specimens (skull lengths of ca. 500 mm) that help advance our knowledge of the anatomy and ontogeny of this taxon and of tyrannosaurids in general. The new specimens exhibit hallmark juvenile tyrannosaurid features, including long, low, and narrow skulls, large circular orbits, absent or incipient cranial ornamentation, ziphodont dentition, and an overall gracile skull frame. Comparison with other Gorgosaurus specimens of various ontogenetic stages allows for an examination of the timing of morphological changes that occurred through ontogeny in this taxon relative to other tyrannosaurids. Of particular note, Gorgosaurus and the larger Tyrannosaurus rex are found to have experienced similar ontogenetic transformations at similar percent skull length relative to the large known individuals for each respective taxon but at different absolute body sizes and biological ages, occurring at a larger size and older age in Tyrannosaurus than in Gorgosaurus. These results suggest a dissociation between the timing of cranial development and body size in tyrannosaurids. Finally, the recognition of ontogenetically invariant characters in Gorgosaurus makes it possible to determine the taxonomic identity of previously misidentified specimens.
- ItemOpen AccessKinetics of Thermal Decomposition of Aqueous Perchloric Acid(National Research Council Canada, 1971) Birss, Viola I.; Henderson, M. Patricia; Swaddle, T. W.
- ItemOpen AccessFine Structure and Differentiation of Ascidian Muscle I. DIFFERENTIATED CAUDAL MUSCULATURE OF DlSTAPLlA OCClDENTALlS TADPOLES(John Wiley & Sons, Inc., 1972) Cavey, Michael J.; Cloney, Richard A.; Biological Sciences; Faculty of Science; University of CalgaryThe structure of the caudal muscle in the tadpole larva of the compound ascidian Distaplia occidentalis has been investigated with light and electron microscopy. The two muscle bands are composed of about 1500 flattened cells arranged in longitudinal rows between the epidermis and the notochord. The muscle cells are mononucleate and contain numerous mitochondria, a small Golgi apparatus, lysosomes, proteid-yolk inclusions, and large amounts of glycogen. The myofibrils and sarcoplasmic reticulum are confined to the peripheral sarcoplasm. Myofibrils are discrete along most of their length but branch qear the tapered ends of the muscle cell, producing a Felderstmktur. The myofibrils originate and terminate at specialized intercellular junctional complexes. These myomuscular junctions are normal to the primary axes of the myofibrils and resemble the intercalated disks of vertebrate cardiac muscle. The myofibrils insert at the myomuscular junction near the level of a Z-line. Thin filaments (presumably actin) extend from the terminal Z-line and make contact with the sarcolemma. These thin filaments frequently appear to be continuous with filaments in the extracellular junctional space, but other evidence suggests that the extracellular filaments are not myofilaments. A T-system is absent, but numerous peripheral couplings between the sarcolemma and cisternae of the sarcoplasmic reticulum (SR) are present on all cell surfaces. Cisternae coupled to the sarcolemma are continuous with transverse components of SR which encircle the myofibrils at each I-band and H-band. The transverse component over the I-band consists of anastomosing tubules applied as a single layer to the surface of the myofibril. The transverse component over the H-band is also composed of anastomosing tubules, but the myofibrils are invested by a double or triple layer. Two or three tubules of sarcoplasmic reticulum interconnect consecutive transverse components. Each muscle band is surrounded by a thin external lamina. The external lamina does not parallel the irregular cell contours nor does it penetrate the extracellular space between cells. In contracted muscle, the sarcolemmata at the epidermal and notochordal boundaries indent to the level of each Z-line, and peripheral couplings are located at the base of the indentations. The external lamina and basal lamina of the epidermis are displaced toward the indentations. The location, function, and neuromuscular junctions of larval ascidian caudal muscle are similar to vertebrate somatic striated muscle. Other attributes, including the mononucleate condition, transverse myomuscular junctions, prolific gap junctions, active Golgi apparatus, and incomplete nervous innervation are characteristic of vertebrate cardiac muscle cells.
- ItemOpen AccessOsmium-Fixed and Epon-Embedded Whole Mounts of Delicate Specimens(Blackwell Publishing, 1973) Cavey, Michael J.; Cloney, Richard A.; Biological Sciences; Faculty of Science; University of CalgaryOsmium-fixed and Epon-embedded whole mounts of delicate specimens. An osmium fixative and an epoxy mountant were used to prepare delicate organisms and tissues as whole mounts for light microscopy. Fine structural details are well preserved by the technique, and common artifacts of whole mount preparation are largely eliminated. The final specimens are suitable as bright field objects or as phase/quasi-phase objects.
- ItemOpen AccessFine Structure and Differentiation of Ascidian Muscle II. MORPHOMETRICS AND DIFFERENTIATION OF THE CAUDAL MUSCLE CELLS OF DlSTAPLlA OCClDENTALlS TADPOLES(John Wiley & Sons, Inc., 1974) Cavey, Michael J.; Cloney, Richard A.; Biological Sciences; Faculty of Science; University of CalgaryThe locomotor function of the caudal muscle cells of ascidian larvae is identical with that of lower vertebrate somatic striated (skeletal) muscle fibers, but other features, including the presence of transverse myomuscular junctions, an active Golgi apparatus, a single nucleus, and partial innervation, are characteristic of vertebrate myocardial cells. Seven stages in the development of the compound ascidian Distaplia occidentalis were selected for an ultrastructural study of caudal myogenesis. A timetable of development and differentiation was obtained from cultures of isolated embryos in vitro. The myoblasts of the neurulating embryo are yolky, undifferentiated cells. They are arranged in two bands between the epidermis and the notochord in the caudal rudiment and are actively engaged in mitosis. Myoblasts of the caudate embryo continue to divide and rearrange themselves into longitudinal rows so that each cell simultaneously adjoins the epidermis and the notochord. The formation of secretory granules by the Golgi apparatus coincides with the onset of proteid-yolk degradation and the accumulation of glycogen in the ground cytoplasm. Randomly oriented networks of thick and thin myofilaments appear in the peripheral sarcoplasm of the muscle cells of the comma embryo. Bridges interconnect the thick and thin myofilaments (actomyosin bridges) and the thick myofilaments (H-bridges), but no banding patterns are evident. The sarcoplasmic reticulum (SR), derived from evaginations of the nuclear envelope, forms intimate associations (peripheral couplings) with the sarcolemma. Precursory Z-lines are interposed between the networks of myofilaments in the uesicutate embryo, and the nascent myofibrils become predominantly oriented parallel to the long axis of the muscle cell. Muscle cells of the papittate embryo contain a single row of cortical myofibrils. Myofibrils, already spanning the length of the cell, grow only in diameter by the apposition of myofilaments. The formation of transverse myomuscular junctions begins at this stage, but the differentiating junctions are frequently oriented obliquely rather than orthogonally to the primary axes of the myofibrils. With the appearance of H-bands and M-lines, a single perforated sheet of sarcoplasmic reticulum is found centered on the Z-line and embracing the I-band. The sheet of SR establishes peripheral couplings with the sarcolemma. In the prehatching tadpole, a second collar of SR, centered on the M-line and extending laterally to the boundaries with the A-bands, is formed. A single perforated sheet surrounds the myofibril but is discontinuous at the side of the myofibril most distant from the sarcolemma. To produce the intricate architecture of the fully differentiated collar in the swimming tadpole (J. Morph., 138: 349, 1972), the free ends of the sheet must elevate from the surface of the myofibril, recurve, and extend peripherally toward the sarcolemma to establish peripheral couplings. Morphological changes in the nucleus, nucleolus, mitochondria, and Golgi bodies are described, as well as changes in the ground cytoplasmic content of yolk, glycogen, and ribosomes. The volume of the differentiating cells, calculated from the mean cellular dimensions, and analyses of cellular shape are presented, along with schematic diagrams of cells in each stage of caudal myogenesis. In an attempt to quantify the differences observed ultrastructurally, calculations of the cytoplasmic volume occupied by the mqjor classes of organelles are included. Comparison is made with published accounts on differentiating vertebrate somatic striated and cardiac muscles.
- ItemOpen AccessUltrastructure and Differentiation of Ascidian Muscle I. Caudal Musculature of the Larva of Diplosoma Macdonaldi(Springer-Verlag, 1976) Cavey, Michael J.; Cloney, Richard A.; Biological Sciences; Faculty of Science; University of CalgaryThe larval caudal musculature of the compound ascidian Diplosoma macdonaldi consists of two longitudinal bands of somatic striated muscle. Approximately 800 mononucleate cells, lying in rows between the epidermis and the notochord, constitute each muscle band. Unlike the caudal muscle cells of most other ascidian larvae, the myofibrils and apposed sarcoplasmic reticulum occupy both the cortical and the medullary sarcoplasm. The cross-striated myofibrils converge near the tapered ends of the caudal muscle cell and integrate into a field of myofilaments. The field originates and terminates at intermediate junctions at the transverse cellular boundaries. Close junctions and longitudinal and transverse segments of nonjunctional sarcolemmata flank the intermediate junctions, creating a transverse myomuscular (TMM) complex which superficially resembles the intercalated disk of the vertebrate heart. A perforated sheet of sarcoplasmic reticulum (SR) invests each myofibril. The sheet of SR spans between sarcomeres and is locally undifferentiated in relation to the cross-striations. Two to four saccular cisternae of SR near each sarcomeric Z-line establish interior (dyadic) couplings with an axial analogue of the vertebrate transverse tubular system. The axial tubules are invaginations of the sarcolemma within and adjacent to the intermediate junctions of the TMM complex. The caudal muscle cells of larval ascidians and the somatic striated muscle fibers of lower vertebrates bear similar relationships to the skeletal organs and share similar locomotor functions. At the cellular level, however, the larval ascidian caudal musculature more closely resembles the vertebrate myocardium.
- ItemMetadata only
- ItemMetadata onlyNUMERICALLY COMPUTABLE BOUNDS FOR THE RANGE OF VALUES OF INTERVAL POLYNOMIALS(1976-01-01) Rokne, JonA central problem in interval analysis is the computation of the range of values of an interval polynomial over an interval. This problem has been treated by Dussel and Schmitt [1] and, disregarding the computational cost of their algorithm, solved in a satisfactory manner. In this paper we will discuss two algorithms by Rivlin [4] (see also Cargo and Shiska [2]) where the accuracy of the bounds depend on the amount of work one is willing to do. The first algorithm is based upon the expression of a polynomial in Bernstein polynomials. This algorithm as given by Rivlin [4] is valid for an estimate over the interval [0,1]. We will generalize the algorithm to an arbitrary finite interval and we will show that it is an appropriate algorithm if the width of the interval is not too large. The second algorithm is based upon the mean value theorem. As stated by Rivlin [4] it is valid for the interval [0,1]. We will generalize the algorithm so that it is valid for any finite interval. The algorithms are then generalized to interval arithmetic versions. Finally we compare the algorithms numerically on several polynomials.
- ItemMetadata only
- ItemMetadata only
- ItemMetadata onlyA housing allocation algorithm for policy impact analysis(1976-07-01) Merlino, Gianfranco; Unger, Brian WAn algorithm designed to simulate the behavior of households while they compete for housing is described. The algorithm accepts as inputs an existing housing state, a new household demand for dwellings and a new supply of dwellings. The acquisition of these available dwellings by the homeless households is simulated producing a new housing state, modified dwelling costs and measures of household dissatisfaction and dwelling shortages. The algorithm is defined using the Algol 60 language and preliminary parameter sensitivity results are presented.
- ItemMetadata onlyAn outline of a network operating system model in Simula(1976-07-01) Unger, Brian WA modelling environment within which operating system resource allocation functions can be implemented and evaluated is described. Both conventional operating systems and computer network operating sytems are considered where network resources include information and devices for the processing, storage and transmission of information. These resources correspond to a distributed file system, host processors, host memory and inter-host communication facilities, respectively. A planned Simula implementation of this environment is outlined.
- ItemMetadata onlyA course in operating system development by a team(1976-07-01) Unger, Brian WA one term course on the cooperative development of an operating system by a team of individuals is described. Operating system implementation is limited to resource allocation functions and is facilitated by using a system software design and simulation package. The course is based on a programming project which includes phases of planning, design, implementation and evaluation. Issues involved in designing the project, organizing a project team and project management are briefly discussed. Emphasis is placed on the communication problems which arise in cooperative systems programming efforts. Three experiences with teaching the course are described and it is conjectured that the major issue affecting group productivity was inter-personal communication.
- ItemMetadata onlyAN EXPERIMENT ON THE PERCEPTION OF INTONATIONAL FEATURES(Elsevier, 1976-08-01) Hill, David R.; Reid, Neal A.An experiment was run in which listeners heard pairs of nonsense words exhibiting the same segmental structure, but differing in the form of pitch variation imposed. In each pair, the first word bore a pitch rise over 100 msecs superimposed upon a generally declining pitch frequency, while the second word carried a similar variation, but with the rise occurring later. Listeners made a forced choice response of "SAME" or "DIFFERENT". The null hypothesis, that listeners' ability to discriminate pairs as different would be independent of the mean position of the pitch rises, was rejected with great confidence and, subject to several caveats, the conclusion was drawn that position of ptich rise, under the conditions of the experiment, was perceived categorically, one category being early in the syllable and the other late. There was some evidence for the existence of two further catagories. The generalization and extension of the work will provide a continuing challenge.
- ItemMetadata onlyEIGENVALUES OF $Ax~=~lambda$$Bx$ FOR REAL SYMMETRIC MATRICES $A$ AND $B$ COMPUTED BY THE HR PROCESS(1976-11-25) Brebner, M.A.; Grad, JThis paper presents a method for solving the eigenvalue problem $Ax~=~lambda$$Bx$, where $A$ and $B$ are real symmetric but not necessarily positive definite matrices, and $B$ is nonsingular. The method reduces the general case into a form $Cz~=~lambda$$z$ where $C$ is a pseudo-symmetric matrix. A further reduction of $C$ produces a tridiagonal pseudo-symmetric form to which the interactive HR process is applied. The tridiagonal pseudo-symmetric form is invariant under the HR transformations. The amount of computation is significantly less than treating the problem by a general method.
- ItemOpen AccessSome results from a preliminary study of British English speech rhythm(1977) Hill, David R.; Witten, Ian H.; Jassem, W.
- ItemMetadata only
- ItemMetadata onlyA REDUCTION OF AN INDEFINITE SYMMETRIC MATRIX A TO THE FORM $LJL sup T$ BYROTATION AND DECOMPOSITIONS(1977-01-01) Brebner, M.A.; Grad, M.J.The paper discusses the reduction of a non-singular symmetric matrix $A$ by decomposition and similarity rotations to the form $LJL sup T$ where $L$ is a lower triangular matrix and $J$ is a diagonal matrix with diagonal elements plus or minus unity. In effect $PAP sup T~=~LJL sup T$, where $P$ is the product of plane rotations.
- ItemMetadata onlySIMILARITY TRANSFORMATIONS FOR PSEUDO- SYMMETRIC MATRICES WITH PARTICULARREFERENCE TO THE HR METHOD(1977-01-01) Brebner, M.A.; Grad, J.The paper defines the term pseudo-symmetric matrix and discusses similarity transformations which preserve pseudo-symmetry. In particular the use of these similarity transformations in the $HR$ analogues of the single and double step $QR$ methods is described.
- ItemMetadata onlyOASIS - reference manual(1977-02-01) Unger, Brian W; Bidulock, Donald; Gosling, James; Robinson, DougNo Abstract