Showing papers by "University of Calgary published in 1986"

Data Structure for Soft Objects

Abstract: We introduce the concept ofsoft objects whose shape changes in response to their surroundings. Established geometric modelling techniques exist to handle most engineering components, including ‘free form’ shapes such as car bodies and telephones. More recently, there has been a lot of interest in modelling natural pheomena such as smoke, clouds, mountains and coastlines where the shapes are described stochastically, or as fractals. None of these techniques lends itself to the description ofsoft objects. This class of objects includes fabrics, cushions, living forms, mud and water. In this paper, we describe a method of modelling such objects and discuss its uses in animation. Our method is to represent asoft object, or collection of objects, as a surface of constant value in a scalar field over three dimensions. The main technical problem is to avoid calculating the field value at too many points. We do this with a combination of data structures at some cost in internal memory usage.

Sexual abuse in childhood: Psychosocial outcomes and implications for social work practice.

Abstract: A study of the prevalence of serious sexual assualt in childhood (up to age 16) is reported in the context of a community mental health study in a random sample of 377 women in a large Canadian city. Twenty-two percent of women reported sexual abuse in childhoos. Sexually abused women were twice as likely to have poor mental health as women who were not abused. The implications are addressed for helping adults whose poor mental health reflects the complex interaction of negative childhood events, including sexual abuse.

Training non-native speech contrasts in adults: Acquisition of the English /ð/-/θ/ contrast by francophones

Abstract: Speech perception abilities are modified by linguistic experience to maximize sensitivity to acoustic contrasts that are important for one’s linguistic community, while reducing sensitivity to other acoustic cues. Although some of these changes may be irreversible, in other cases adults may learn to perceive non-native speech sounds in a linguistically meaningful manner with limited perceptual training. The present study investigates the possibility of using a technique based on perceptual fading to train Canadian francophone adults to distinguish the voiced and voiceless “th” sounds of English: Ið/, as in “the,” versus Iθ/, as in “theta.” Following a pretest to measure identification and discrimination performance with both natural and synthetic speech tokens, 10 subjects were trained using synthetic stimuli. Approximately 90 min of this training improved performance with both natural and synthetic tokens relative to that of untrained control subjects. The results suggest that there is a much higher degree of plasticity in these acoustic/linguistic categories than would be inferred from the normal performance of Canadian francophones who learn English as adults. The nature of the training technique is discussed in relation to other training paradigms.

The influence of wettability and critical pore-throat size ratio on snap—off

Abstract: Experiments under quasistatic conditions show that the aspect ratio (pore-to-throat effective diameter ratio) necessary for snap-off in throats is ∼ 1.5 when advancing contact angles (θA) are equal to zero and increases only slightly, to 1.75, when θA is equal to 55°. Above ∼70°, snap-off in throats does not occur in systems with pressure equilibrium between pores and throats. Three critical contact angles are recognized for two types of interfaces. Advancing (θA) and receding (θR) angles for convex interfaces and θS, the angle measured for selloidal interfaces at the moment of instability when snap-off occurs. Capillary pressure, disjoining pressure, thin-film thickness, and contact angles are interrelated phenomena and, for a given solid and fluid pair, θA, θR and θS may be defined at different pressures and are not equal but are points on a common curve, the equation for which is defined. As θA increases from 0° to 70° we estimate that θS increases from 30° to 77°. The difference between θS and θA decreases with increase in θA. The Young-Laplace equation assumes constancy of contact angle and must be applied with caution since contact angle is a function of capillary pressure as well as of interface type.

Viscosity of compressed athabasca bitumen

Abstract: New data for the effect of pressure and temperature on Athabasca bitumen viscosity are presented The viscosity data cover a temperature range of 43–120°C and pressures up to 10 MPa It is shown that the compression of bitumen results in a significant increase in its viscosity but only a small increase in its density Also presented are correlations that include the effect of pressure and temperature on the viscosity of the bitumen On presente de nouvelles donnees sur l'influence de la pression et de la temperature sur la viscosite du bitume d'Athabasca Les donnees de viscosite ont ete obtenues pour des temperatures comprises entre 43 et 120°C et des pressions jusqu'a 10 MPa On montre que la compression du bitume entraǐne une augmentation importante de sa viscosite tandis que l'on n'observe qu'une faible augmentation de sa densite On presente egalement des correlations decrivant l'influence de la pression et de la temperature sur la viscosite du bitume

An Adaptive Synchronous Machine Stabilizer

Abstract: An adaptive synchronous machine stabilizer utilizing the least-squares identification with varying forgetting factor and a self-searching control strategy is proposed in this paper. The use of varying forgetting factor in the identification algorithm improves parameter tracking under both transient and dynamic conditions, and the use of a self-searching pole shifting control technique increases the flexibility when applied to varying operating conditions encountered in power systems. These features make this stabilizer very robust. Studies given in the paper show that the proposed self-tuning stabilizer provides excellent damping under varying operating conditions and with different types of disturbances.

Human sperm protamines. Amino-acid sequences of two forms of protamine P2.

Abstract: Human protamine P2 was purified to homogeneity by solubilizing whole spermatozoa in guanidinium X HCl containing 2-mercaptoethanol, alkylating the resulting protamine thiols with vinylpyridine, removing acid-insoluble material by acid dialysis and using CM-cellulose chromatography to remove non-protamine basic proteins and separate protamines P1 and P2. The P2 preparation contained two components, P2a and P2b, which were sequenced completely without being separated. The peptides obtained from thermolysin and endoproteinase Lys-C digestions were purified by reverse-phase high-pressure liquid chromatography and sequenced using a gas-phase sequencer. P2a contains 57 amino acids and has a relative molecular mass of 7636 while P2b contains 54 amino acids, which are identical to residues 4-57 of P2a, and has a relative molecular mass of 7242. Protamine P2a is approximately 50% homologous with human protamine P1. The amino acid sequence of P2a is: (sequence; see text)

Mast Cell Differentiation and Heterogeneity

Abstract: Major differences between mast cells from different tissues and species have been known for at least 20 years but have been rigorously studied only recently. A recent meeting focused on the ontogeny and differentiation of mast cells, their functional characteristics and the clinical and biological significance of their heterogeneity.

Mechanisms of nonwetting phase trapping during imbibition at slow rates

Abstract: Experiments performed in transparent-glass micromodels were used to observe the mechanisms of both wetting phase (wp) and nonwetting phase (nwp) disconnection and entrapment during drainage and imbibition at slow rates. Convex and selloidal menisci, slowly advanced by an externally imposed flow during imbibition, periodically exceed limits of stability and undergo short, rapid advances during which nwp may become disconnected by one of two processes referred to as snap-off and break-off. Snap-off involves selloidal menisci and can occur within throats, within pores or at the junction region of pores and throats. Break-off refers to rupture during piston-type advance of a convex interface which contacts an opposing pore wall. The critical capillary pressures and other conditions for snap-off in throats, piston-type motions in pores, snap-offin pores and break-off have been determined experimentally and provide the basis for simulating microscopic displacement processes in media with any specified structure and wettability. These interface movements during imbibition are influenced by the sizes, shapes, and arrangement of both pores and throats with respect to the direction of advancing displacing phase. Earlier interface motions determine what is possible subsequently and the sequence and position of snap-off and break-off events determine the amount and location of trapped nonwetting phase. Wettability and topology are the main factors which determine whether snap-off occurs in throats, in pores, or at pore-throat junctions.

Animating soft objects

Abstract: Soft objects change shape as they move. Specifying such changes is a complicated task which has received little attention in the literature largely because, until recently, we had no adequate way to represent such objects. In order to look natural, any animation has to represent possible motion in the physical world. In this sense, the best animation is based on detailed simulation. Fairing in hand animation can be regarded as a crude attempt to use a few simple rules to do this. Oursoft objects are represented by a surface constructed around a set of key points. We use both mathematical descriptions and physical simulation to determine the motion of the key points and thus achieve convincing animation effects.

Pharmacokinetics of sufentanil in patients undergoing abdominal aortic surgery

Abstract: The authors determined the pharmacokinetics of fentanyl 100 micrograms X kg-1 iv in patients undergoing elective abdominal aortic surgery. The mean (+/- SD) age of the ten patients was 67.2 +/- 8.7 yr; their mean weight was 78.5 +/- 13.7 kg. Seven patients had aortic aneurysm repair, and the other three patients had aortobifemoral grafts. Serum fentanyl concentrations were determined from samples drawn at increasing intervals over a 24-h period. A three-compartment pharmacokinetic model was fit to the concentration versus time data. Total drug clearance was 9.8 +/- 1.8 ml X min-1 X kg-1. The volume of distribution at steady-state (Vdss) was 5.4 +/- 1.9 X 1 kg-1. Elimination half-time was 8.7 +/- 2.5 h. There were no significant correlations between these pharmacokinetic parameters and patient's age, duration of aortic cross-clamping, duration of surgery, intraoperative blood loss, or volume of iv fluids given intraoperatively. In healthy volunteers or patients undergoing general surgery, other investigators report mean elimination half-times for fentanyl ranging from 1.7 to 4.4 h. The prolonged elimination half-time in patients having abdominal aortic surgery has important clinical implications. In particular, recovery from large doses will take much longer than would have been anticipated from previously published fentanyl pharmacokinetic data.

Phytoplankton and its dynamics in two tropical lakes: a tropical and temperate zone comparison

Abstract: Temporal patterns of phytoplankton biomass and community structure are described for two Kenyan lakes and subsequently compared with patterns reported in other tropical and temperate lakes. Lake Naivasha had a lower and more seasonally variable (10x) biomass, with a seasonal shift between diatoms and blue-greens, while the L. Oloidien biomass was less variable (3.7x) and dominated by blue-greens. Biomass and chlorophyll a were strongly correlated and in turn were coupled to the level of total phosphorus. A total of 143 and 94 taxa were described for L. Naivasha and L. Oloidien, respectively.

A syndrome of microangiopathic hemolytic anemia, renal impairment, and pulmonary edema in chemotherapy-treated patients with adenocarcinoma

Abstract: Chemotherapy is frequently used to treat adenocarcinoma. Thirty-nine cases are reviewed in which the patients developed a hemolytic-uremic-like syndrome, apparently in response to chemotherapy. About 44% of the patients had gastric adenocarcinoma, and 82% had received mitomycin C. Most patients (75%) developed the syndrome 6 to 12 months after starting chemotherapy, and 60% were in remission. Severe microangiopathic hemolytic anemia, thrombocytopenia, and renal impairment were each noted in about 90% of the cases. Neurologic symptoms were usually absent, but 49% of the patients developed adult respiratory distress syndrome (ARDS). The overall case fatality rate was 72%; those patients with ARDS had a 95% mortality rate, while 50% of those without ARDS survived. The half-life of survival of those who ultimately died was 2 months. Treatment is unsatisfactory, although steroids and plasmapheresis may prolong survival.

Multiprocessor ray tracing

Abstract: A multiprocessor algorithm for ray tracing is described. The performance of the algorithm is analysed for a cubic and square array of processors with only local communication between near neighbours. Theoretical expressions for the speedup of the system as a function of the number of processors are derived. These analytic results are supported by simulations of ray tracing on a number of simple scenes with polygonal surfaces. It is found that a square network of processors generally performs better than a cubic network. Some comments are made on the construction of such a system using current (1985) microprocessor technology.

An increased frequency of human sperm chromosomal abnormalities after radiotherapy

Abstract: 13 cancer patients were studied before radiotherapy (RT) and at regular intervals after RT to determine the effect of RT on chromosomal abnormalities in sperm. The men were 19–47 years old and received testicular radiation doses of 0.4–5.0 Gray. Human pronuclear sperm chromosomes were analysed after penetration of zona-pellucida-free hamster eggs. Unfortunately the hamster egg penetration rates were exceedingly low, both before and after RT and this limited the number of sperm chromosome complements which could be analysed. Before RT, the frequency of abnormal sperm chromosome complements was 0% ( 0 9 ). After RT, the majority of men were azoospermic for 24 months but complements could be analysed from 4 men. In the first 12 months the frequency of abnormalities was 13% ( 1 8 ) and at 24 months it was 13% ( 7 55 ). By 36 months after RT, most men had recovered sperm production and the frequency of abnormalities in 8 men was 21% ( 18 86 ), which is significantly higher than the rate in control donors (8.5%). For individual men the range was 6–67%, and there was a significant correlation between testicular radiation dose and the frequency of sperm chromosomal abnormalities. The frequencies of both numerical and structural abnormalities were significantly increased after RT. This is the first evidence that radiation may increase the frequency of chromosomal abnormalities in human gametes.

Standardization and quality control of sperm concentration and sperm motility counts in semen analysis.

Abstract: The paper reports a study of standardization and quality control of sperm concentration counts and visual motility assessments in human semen analyses performed for infertility investigations and from internal quality control procedures. Sperm concentration determinations were performed in Improved Neubauer haemocytometers on volumetric dilutions made using a positive displacement pipettor for sampling the liquefied semen. In addition to a standard 1 + 19 dilution a second dilution of either 1 + 9, 1 + 19 or 1 + 49 was made according to whether the estimated sperm concentration was less than 20, 20-100 or greater than 100 X 10(6)/ml respectively. The duplicate determinations of sperm concentration were highly significantly correlated (P much less than 0.001) with less than 5% variability. Parallel visual sperm motility assessments were made by two pairs of technicians and showed highly significant correlations (P much less than 0.001) between technicians in the determination of the percentages of motile and progressive spermatozoa as well as the subjective rating of sperm progressivity. When these values were incorporated into a calculated motility index which gave added weight to the progressive spermatozoa and to their quality of progression the correlations between technicians remained highly significant (P much less than 0.001) with average differences of the order of 1.0%. Therefore, provided that sufficient attention is paid to technician training, regular standardization checks and the use of only proven reliable procedures, quantitatively accurate values for sperm concentration and motility can be obtained in routine semen analyses.

Direct conversion of sulphide and sulphate minerals to SO2 for isotope analyses

Abstract: Sulphide and sulphate minerals mixed with V2O5 and SiO2, were heated in a vacuum at 950°C for 15 minutes. The evolved SO3 was converted to SO2 by reaction with metallic Cu for sulphur isotope determinations. This technique yields SO2 of consistent oxygen isotope composition regardless of whether sulphide or sulphate is converted. The reproducibilities of sulphur conversion and δ34S values were 98 ±5% and ±0.2‰, respectively. The technique is particularly suitable for small samples. Successful isotope determinations have been obtained with natural samples containing less than 1 mg S. In some cases, variations in δ34S of 2‰ have been found for single grains analysed from a small specimen.

The histogenesis of adenocarcinoma of the gallbladder.

Abstract: A prospective study of 277 cholecystectomy specimens for evidence of isolated epithelial dysplasia of gallbladder mucosa is presented. In addition, 15 cases of primary adenocarcinoma of the gallbladder are retrospectively reviewed with particular reference to the presence of metaplasia and dysplasia adjacent to the infiltrating tumor, in order to establish the relationship between metaplasia, isolated epithelial dysplasia, and adenocarcinoma of the gallbladder. Only one case of isolated epithelial dysplasia was found in the 277 cholecystectomy specimens, and this arose within focal incomplete intestinal metaplasia. In the 15 cases of adenocarcinoma of the gallbladder, benign antral and/or incomplete intestinal metaplasia was found adjacent to the tumor in 11 cases. In 10 cases, dysplasia of this metaplastic epithelium was found in continuity with the tumor. The authors conclude that the most common pathway to adenocarcinoma is via dysplasia of metaplastic gallbladder epithelium.

Entropy in evolution

Abstract: Daniel R. Brooks and E. O. Wiley have proposed a theory of evolution in which fitness is merely a rate determining factor. Evolution is driven by non-equilibrium processes which increase the entropy and information content of species together. Evolution can occur without environmental selection, since increased complexity and organization result from the likely “capture” at the species level of random variations produced at the chemical level. Speciation can occur as the result of variation within the species which decreases the probability of sharing genetic information. Critics of the Brooks-Wiley theory argue that they have abused terminology from information theory and t thermodynamics. In this paper I review the essentials of the theory, and give an account of hierarchical physical information systems within which the theory can be interpreted. I then show how the major conceptual objections can be answered.