Showing papers by "University of British Columbia published in 1969"

Natural convection above unconfined horizontal surfaces

Abstract: The paper discusses free convective flows above a horizontal plate, both theoretically and on the basis of experiments which yield quantitative data. The theory is applicable to the semi-infinite plate and is extended to cover the complete range of Prandtl number values including Pr → 0 and Pr → ∞. Experiments were carried out to demonstrate the existence of a laminar boundary layer above a horizontal plate at intermediate Grashof (respectively Rayleigh) numbers, and its extent along the plate. This layer breaks down into large-eddy instability some distance from the leading edge. The value of the critical Rayleigh number for this to occur, obtained experimentally using semi-focusing colour-Schlieren photography is in reasonable qualitative agreement with previously known data (Tritton 1963a,b).

Infrared Reflection Studies of the Oxidation of Copper and Iron

Abstract: Infrared multiple reflectance spectra were used to record the growth of oxide films on copper and iron mirrors. Cuprous oxide and cupric oxide films were readily distinguished since they exhibit intense single bands at 640 cm−1 and ~560 cm−1, respectively. Iron oxide films of a single composition also exhibit highly characteristic bands in the 230 to 1100 cm−1 region of the reflectance spectra. Spectra of mixed iron oxide films were composed of many highly overlapping bands making quantitative interpretations difficult. The intensities of the infrared bands from the copper oxide and iron oxide films were directly proportional to the oxide film thicknesses. Using a seven reflection −73° incidence optical accessory, sensitivity to detect oxide films as thin as about 5Aa was achieved.

The population dynamics of Newfoundland caribou

Abstract: The p o p u l a t i o n dynamics o f caribou (Rangifer tarandus) on the I s l a n d of Newfoundland were s t u d i e d 1957 to 1967. Four herds were recognized and censused: the Northern P e n i n s u l a — 450 animals i n 1958 and 400 i n 1966, the Avalon P e n i n s u l a — 125 i n 1957 and 720 In 1967., the'. Humber Ri v e r — 130 i n 1956 and 115 i n 1964, and the I n t e r i o r -4600 i n 1957 and 6200 animals i n 1966. The I s l a n d p o p u l a t i o n 1900-1910 was estimated at 40,000 animals. A f t e r 1915 these herds r a p i d l y d e c l i n e d and reached a low of perhaps only 2000 animals by 1930. The annual r a t e of increase Cr) of a l l the herds was low. The' Humber and Northern Peninsula herds showed no increase while the I n t e r i o r Herd grew at only 0.044. The Avalon Peninsula Herd showed the great e s t r a t e o f i n c r e a s e 1961 t o 1967, r= 0.120. The p o t e n t i a l r of Newfoundland carib o u i s probably greater than 0.30. A herd of carib o u introduced t o Brunette I s l a n d increased at r=0.352, from 17 t o 100 animals i n 5 years. In the I n t e r i o r Herd, b i r t h r a t e s were high and constant and averaged 0.85 c a l f per doe 2-years-of-age and o l d e r and 0.94 c a l f per doe 3 years and o l d e r . N a t u r a l m o r t a l i t y r a t e s were low beyond 6-months-of-age. They were 4 per cent f o r does, y e a r l i n g s , and calves and 9 per cent f o r stags 2-years-of-age and o l d e r . The k i l l of stags by hunters was 11 per cent and reduced the p r o p o r t i o n of stags i n the po p u l a t i o n . The s u r v i v a l of calves t o 6-months-of-age was s t r o n g l y c o r r e l a t e d w i t h growth of populations and appeared the main i n f l u e n c e on numbers ( c o r r e l a t i o n c o e f f i c i e n t r=0.922, P<0.01). The m o r t a l i t y of calves i n the f i r s t summer was h i g h ; an average of 69 per cent died i n the I n t e r i o r Herd and i n the Avalon Pe n i n s u l a Herd 30 per cent of the calves d i e d .

The Early Field Defects in Glaucoma

Abstract: the visual field. We cannot rule out glaucoma by testing a predetermined or specific area in the visual field. A complete examination of the visual field is best performed by using both static and kinetic perimetry together. This seems to constitute the best means of modern quantitative perimetry. Scatter of test points can be controlled only by careful attention to numerous details involving physical, pharmacological, physiological, and psychological factors, the \"chaff\" which must be differentiatied from the \"wheat\"—the pathological patterns to be delineated in testing the visual field. The factors causing scatter also influence the reproducibility of a given visual field from one date to another, as do the refractive media, pupil size, mental status, and choice of data points.

Pyruvate kinase variants of the Alaskan king-crab. Evidence for a temperature-dependent interconversion between two forms having distinct and adaptive kinetic properties

Abstract: 1. Pyruvate kinase of Alaskan king-crab leg muscle exists in two kinetically distinct forms, each of which displays a different temperature-dependence in the Km for phosphoenolpyruvate. 2. A ‘cold’ variant of the enzyme has hyperbolic kinetics and exhibits a minimal Km for substrate at 5°. At physiological concentrations of phosphoenolpyruvate the ‘cold’ enzyme is active only below 10°. A ‘warm’ pyruvate kinase has a minimal Km for substrate at about 12°. This enzyme displays sigmoidal kinetics and is likely to be inactive, at physiological substrate concentrations, at temperatures below 9°. 3. The combined activities of these two pyruvate kinases yield highly temperature-independent rates of catalysis, at physiological substrate concentrations, over the range of habitat temperatures encountered by the organism, namely 4–12°. 4. The two variants of pyruvate kinase do not appear to be isoenzymes in the conventional sense. Electrophoretic and electrofocus analyses revealed only single peaks of activity. 5. The results suggest that the ‘warm’ pyruvate kinase and the ‘cold’ pyruvate kinase are formed by a temperature-dependent interconversion of one protein species. This interconversion has major adaptive significance: as the temperature is lowered the ‘warm’ enzyme is converted into the ‘cold’ enzyme; the opposite situation obtains when the temperature is raised. Temperature changes thus mimic the effects noted for fructose 1,6-diphosphate on certain mammalian pyruvate kinases.

Isoenzymes and short-term temperature compensation in poikilotherms: activation of lactate dehydrogenase isoenzymes by temperature decreases.

Abstract: AT physiological substrate concentrations, the rates of enzymatic reactions of poikilotherms may be highly independent of temperature1–5. The basis of this effect has recently been clarified: for all enzymes from poikilotherms which we have examined, enzyme-substrate (E-S) affinity varies inversely with temperature over a large portion of the species' range of habitat temperatures. In addition, E-S affinity frequently reaches a maximum at temperatures near the lower extreme of the species' habitat temperatures3–5.

Some effects of lake renewal on phytoplankton productivity and species composition1

Abstract: Primary production in Marion Lake is inversely related to the rate at which water enters the lake when light intensity is corrected to a standard level. Increased flushing rates reduce the phytoplankton standing crop thereby lowering the total primary productivity in the lake. Thus seasonal variations in rainfall in southwestern British Columbia exert an appreciable influence on the annual productivity pattern of the lake’s phytoplankton. Lake water artificially enclosed within small areas of the lake produced algal blooms while phytoplankton standing crop in the rest of the lake remained low. Nannoplankton appear to have a selective advantage over larger, more slowly reproducing forms in Marion Lake. The production: biomass ratio for lake phytoplankton was used as an indication of the general type of limiting factor affecting the instantaneous rate of productivity in the lake.

The energetics of mammalian cell growth.

Abstract: SUMMARY Data from batch growth curves of mouse LS cells cultivated at controlled dissolved oxygen partial pressures were used to calculate the weight of cells produced per mole of adenosine triphosphate generated (YArv). These values agree well with those reported for bacteria. A theoretical relationship was developed which allowed the biosynthetic and maintenance energy requirements to be estimated. The biosynthesis of LS cells required i-6 x io" 11 moles of ATP/cell. The maintenance energy, which is a function of growth rate, was 2-9 x io"" 11 moles ATP/new cell when the mean generation time was 1-15 days. The proportion of the total energy used for maintenance under these conditions was 65 %. This corresponds to a value of less than 10 % for bacterial maintenance when the organisms are grown at near their maximum rate. A comparison of biosynthetic energy requirements indicates that bacteria and moulds require about 4 times as much energy as animal cells to generate the same weight of cell material. Possible explanations of this difference are discussed.

Hyperphagia in Rats with Cuts between the Ventromedial and Lateral Hypothalamus

Abstract: Bilateral cuts between the ventromedial and lateral hypothalamus in female rats consistently produced hyperphagia. Hyperphagia occurred slightly less reliably when one of the cuts entered the ventromedial hypothalamus and only infrequently if one entered the lateral hypothalamus. The results are consistent with other evidence that suggests that fibers originating medially stop eating by inhibiting cells in the lateral hypothalamus.

An extension to the method of Kryloff and Bogoliuboff

Abstract: An extension of the method of Kryloff and Bogoliuboff is presented which uses Jacobian elliptic functions to approximate the solutions to a class of second-order differential equations exhibiting a gross cubic non-linearity. The results obtained from an analysis of the error incurred by the approximation show that, provided certain conditions of smallness are satisfied, excellent solution accuracy can be obtained. Two examples are used to demonstrate application of the extension to systems of practical interest.