Two independent Fe³⁺ species have been simultaneously introduced into Linde L zeolite. One is an exchanged Fe³⁺ species while the other is the molecular species FeCI₃, By simpIe outgassing at 573°K, the exchanged Fe³⁺ is reduced to Fe²⁺. By sweeping the system at 523°K with H₂, both species are converted to ferrous and, at 573°K, the exchanged species is reduced to Feº and the FeCI₃ is reduced to FeCI₂. Outgassing the latter system at 573°K oxidizes the Feº to Fe₂O₃ while the FeCI₂ remains intact. These valency changes were examined using Mössbauer Spectroscopy and, using this technique, a Morin transition appears to have been detected in the Feº species. / Science, Faculty of / Chemistry, Department of / Graduate

The structure in the collapse stage of a linear Z-pinch discharge in helium has been studied by optical methods. Observations with a framing camera, rotating mirror spectrograph, and monochromator have been correlated with magnetic field and current distributions determined by Tam (1967). The luminous regions in a helium pinch are very faint. Therefore, up to twenty exposures have to be superimposed on the same framing camera or rotating mirror record. This requires a high degree of reproducibility in the initiation of the discharge. At high initial pressures, a non-luminous shock wave at the inner edge of the collapsing current shell precedes the luminous plasma layer towards the centre of the discharge vessel. This shock front is followed by a region of predominantly Hel emission, while most of the Hell radiation occurs in the outer regions of the collapsing plasma shell. The separation into Hel and Hell radiating regions is consistent with spectroscopic measurements of temperature: higher temperatures occur at larger radii. Pressure and density in the non-radiating shock wave region are determined by calculations based on a simple model. At low filling pressures, the Hel and Hell regions coincide. The position of maximum luminosity is observed to correspond with the position of maximum current density. The luminosity and current shells coincide with no shock wave preceding the luminous front. Strong continuum radiation is emitted from the centre of the discharge tube as soon as the leading edge of the current shell reaches the axis. This leading edge is luminous at low initial pressures, but becomes a non-radiating shock front at higher filling pressures. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The primary objective of this study was to investigate the radiosensitivity of Pseudotsuga menziesli (Mirb.) Franco, Douglas-fir, from two different provenances representing the coastal and interior regions in British Columbia, Picea sitchensls (Bong.) Carr., Sitka spruce, and Tsuga heterophylla (Raf.) Sarg., Western hemlock. A secondary objective was to correlate the radiosensitivity with some cytogenetical and biochemical characteristics. Induction of mutations and radiostimulation of seed germination and seedling growth were also sought. Filled seeds of the above mentioned species were given five different dosages of gamma-irradiation from a cobalt-60-source control, 500, 2,000, 5,000, and 10,000 R. Stratification for 14 days at 0°-2°C as post-irradiation treatment was tested. Germination values were evaluated and germinants were transplanted. Survival and growth under controlled environmental conditions were recorded for 182 days. The species exhibited differential responses to seed irradiation. All showed drastic reduction in germination and survival at the higher dosages, (5,000-10,000 R). There was some stimulation of Interior Douglas-fir seed germination and seedling survival at 500 and 2,000 R irradiation dosages over the control. The same exposures stimulated the height growth of Coastal Douglas-Fir. Stratification after irradiation reduced seed germination and seedling growth and survival in all the species. The tolerance to gamma-irradiation decreased in the following Order: Interior Douglas-fir, Coastal Douglas-fir, Western hemlock and Sitka spruce. Sitka spruce had a significantly larger nuclear volume than Western hemlock and Douglas-fir. No correlation was found between nuclear volume, or interphase chromosome volume, and LD₅₀ (germination). The amount of DNA per cell and per chromosome differed significantly among the three species with Sitka spruce having the highest DNA content followed by Western hemlock, Coastal Douglas-fir and Interior Douglas-fir. Significant negative correlations were found between DNA content per cell and per chromosome, and LD₅₀ (germination). This indicated that DNA content plays a more important role than nuclear volume in determining the radiosensitivity of the species. The differences in radiosensitivity, nuclear volume and DNA content between the Coastal and Interior forms of Douglas-fir are discussed in relation to their ecogeographical distribution and taxonomy. Chromosome breaks, micro-nuclei and chromosome erosion were detected in irradiated seeds of Douglas-fir. Intraspecific hybridization was carried out in Douglas-fir using gamma-irradiated pollen grains. Pollen irradiation up to 5,000 R increased the number of filled seeds/cone. Seedlings from pollen irradiated at 500 R, exhibited some increase in height growth. Similar effects were obtained for pollen germination in vitro. The possibilities of utilizing seed and pollen irradiation in forest tree improvement are discussed' and recommendations are made for future mutation breeding work. / Forestry, Faculty of / Graduate

The electronic emission spectra of the OH and CH molecules in applied electric fields up to 68,000 v/cm have been observed. These spectra show Stark splittings, broadenings and field-induced, parity-forbidden lines. The electric dipole moment of the molecules has been determined for OH in the ²π electronic state and CH in both the ²π and ²∆ electronic states from Stark effects on transitions to the following levels: [formula omitted] Electric fields were determined from Stark splittings in hydrogen Balmer lines. The Stark spectra were produced in the high field region of a low pressure glow discharge. This technique is well suited for the study of short lived and chemically reactive molecules in both their ground and excited, electronic states. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Effects of day/night temperature regimes ranging from 45/40 to 90/75°F on growth and development of Dark Skin Perfection peas were studied in controlled-environment cabinets. Light intensity was about 1500 foot-candles and the photoperiod was 16 hours. Rate of plant development, in terms of nodes produced per day, increased steadily as the average temperature increased. Rate of stem elongation, however, was most rapid at 70/55°F; and plant height was greatest at 60/50°F. On a dry matter accumulation per day basis, vine growth decreased above and below a temperature optimum which shifted from 70/60 to 60/50°F in the course of plant development. Tillering was most prolific at the lower temperatures and was absent at 90°F. Pea yield decreased as temperature increased above 60/50°F, due mainly to a reduction in the number of pods per plant. The number of peas per pod was decreased by high day/high night-temperature treatments and by high day temperature treatments imposed prior to full bloom. The combination of high day and high night temperatures caused an increase in the number of nodes to the first flower, whereas number of nodes to the first flower was decreased at the very low temperatures. Percent dry matter of plants was markedly increased at 45/40°F. / Land and Food Systems, Faculty of / Graduate

The formative phase of a 40 kV Z-pinch has been investigated in the pressure range from 10 mtorr to 80 mtorr in hydrogen. The energy spectrum of the electrons on the axis of the vessel, the spatial distribution of the current at the face of the anode, the total discharge current and the voltage across the discharge have all been monitored. For the pressures examined, the formative phase lasts a few hundred nanoseconds. At the initiation of the discharge, a current of electrons with energies in excess of 20 keV is observed on the axis. As time progresses, the average energy of the electrons decreases to a few keV and the current density increases to about 300 amps/cm². At pressures of 30 and 50 mtorr-H(2), the electron velocity distribution appears to relax to a Maxwellian [formula omitted]. This result is in agreement with the theoretical description of a weakly ionized gas in a strong electric field. However, it should be noted that the influence of plasma-turbulence has been neglected. The current to the central region of the electrode initially carries more than 50% of the total current through the discharge. This observation indicates that ionization initially occurs throughout the entire discharge vessel. However, shortly after the current of energetic electrons reaches its maximum value, the current to the central region of the electrode disappears. Simultaneously, a transient voltage of up to 20 kV appears across the discharge and the rate of increase of the current exhibits a sharp drop in value. The combination of these phenomena has been interpreted as the formation of the boundary layer. The boundary layer or current sheet is not completely formed until the end of the formative phase. Measurements of the pinch time support this conclusion. At low pressures, the time of formation of the boundary layer is considerably shortened by the enhancement of ionization at the wall. This is caused by the presence of the magnetic field of the current flowing in the central region of the vessel. The experiment has led to better comprehension of the mechanism of boundary layer formation in low pressure Z-pinches. The overall understanding of ionization in Z-pinch discharges has been improved and can be extrapolated to higher pressures. In addition, the observations indicate that the detailed nature of the current sheet collapse can be strongly affected by the formative phase. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A study was undertaken to investigate the solid-state structure of about 25 triphenyltin carboxylates, Ø₃SnOCOR. The compounds were synthesized and then analyzed by Mössbauer and infrared spectroscopy. The compounds were divided into three series on the basis of the nature of the R group. The first series of compounds had R groups which were "linear" chain hydrocarbons ranging in length from one carbon atom (triphenyltin formate) to eighteen carbon atoms (triphenyltin stearate). In the second series several compounds had methyl branches at various positions along the hydrocarbon chain, some had longer alkyl groups and a few had a methylene group bonded to the a-carbon atom. The third series contained mono-, di-, and tri- substituted haloacetates. These compounds were prepared in order to test the assumption that bulky R groups would prevent (by steric interaction) polymer formation in the solid. The polymeric structure which is commonly found for triorganotin carboxylates consists of pentacoordinate Sn atoms. Each carboxylate group bridges between two different Sn atoms and this occurs indefinitely to form a polymer. Steric interaction of the R group with neighbouring phenyl groups (bonding to Sn) could prevent polymer formation. The resulting structure would be monomeric and have a tetracoordinate Sn atom and a terminal carboxylate group like that for an organic ester. The majority of compounds were found to be polymeric solids. Structural changes (polymeric to monomeric) were observed for a few compounds and this could be attributed to steric interaction. The Mössbauer and infrared data were complimentary and conclusive when used to differentiate between the two possible structural types. In a polymeric structure the Sn atom can be visualized as being in a trigonal bipyramidal environment in which the oxygen atoms are axial and the phenyl groups equatorial. Using the above idealized structural type it was possible to test a point-charge model which had been used to predict quadrupole splitting values, Δ. The model was tested for the triphenyltin haloacetates and found to give fairly good agreement with the observed quadrupole splitting values. / Science, Faculty of / Chemistry, Department of / Graduate

Low, non-freezing temperatures can cause both, harmful and beneficial effects on plants, and this research was carried out to survey some effects on starch and pigment accumulation. Four species were selected on the basis of photosynthetic biochemistry and major systematic grouping. Zea and Gomphrena possess the C₄-dicarboxylic acid pathway typical of certain families of tropical origin, while Triticum and Phaseolus contain the Calvin cycle alone which is typical of plants originating in temperate regions. Zea and Triticum are Monocotyledoneae while Gomphrena and Phaseolus are members of the Dicotyledoneae. Plants of each species were subjected to 10 days of cold treatment starting when they were 10, 21 or 35 days old (15, 26 and 40 days old for Gomphrena), and spectrophotometry measurements of starch, chlorophylls a and b, and carotenoids were carried out during the treatments. The effects of cold temperature depended on species, age, and duration of treatment. All of the species exhibited a significantly higher level of starch in the cold temperature for at least two of the three ages tested. The most dramatic effect of low temperature occurred in Gomphrena when the starch concentration increased to over 2000 per cent of the concentration attained at the warm temperature. Variations in the effect of cold treatment between the different ages tested were more pronounced in the monocots used than in the dicot species studied and variations due to the duration of cold treatment were observed in Gomphrena and Triticum. Cold treatment also caused significant reduction in total chlorophylls, chlorophyll a and chlorophyll b in all the species except Triticum. In Zea, the response to cold decreased as the plants aged, and the duration of cold treatment had a significant effect in Zea and Gomphrena. When the youngest plants only are considered, the response of starch and chlorophyll levels to cold treatment was well correlated with the typical photosynthetic pathway of the species tested. Low temperature had no significant effect on total carotenoid concentration .The effect of low temperature on light transmission by young Zea leaves during the first 48 hours of greening was also examined. Chlorophyll a concentration and leaf light transmission were highly correlated and the more convenient transmission measurements can therefore be used to predict leaf chlorophyll concentration. At the warm temperature used, there was a linear increase in chlorophyll concentration after a 2 hour lag period. Preceding cold treatment caused a longer lag period before chlorophyll began to accumulate at the warm temperature. Also, no chlorophyll accumulated, or there was net chlorophyll breakdown at low temperature. Kinetin treatment did not prevent the decrease in chlorophyll concentration at the low temperature. / Land and Food Systems, Faculty of / Graduate

It is shown that light emitted by mercury vapour at 253.7 nm can be polarized by passing the light through mercury absorption gas embedded in a magnetic field which is transverse to the direction of propagation of the light. The absorption lines of the mercury are split by the Zeeman effect, so that the absorber has an absorption coefficient which depends on both the polarization and wavelength of the transmitted light. A complete theory for the Hg²⁰² isotope is presented and the results are compared to measurements made with a natural mercury emitter and absorber. The observations are in qualitative agreement with the theory once isotope and hyperfine structure of the isotopes in natural mercury are included in the theory. Quantitative analysis was not possible because the emission line profiles could not be measured with the available equipment. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Batch cultures of the marine diatom, Thalassiosira pseudonana were grown in the defined medium Aquil without EDTA and with varying concentrations of added iron (Fe). The response of cultures to Fe depletion was more rapid and dramatic when in vivo fluorescence (a correlate of cellular chlorophyll a) was used as a measure of biomass instead of cell density. In vivo fluorescence and in vivo fluorescence per unit cell density were found to be more sensitive and reliable measures of Fe limitation than cell density alone. Because the physiology of nutrient-limited cells changes rapidly in batch culture, a chemostat was designed and constructed to grow axenic cultures of T. pseudonana under constant degrees of Fe limitation. Fe-limited chemostat cultures grown in Aquil without EDTA were also partly limited by silicate. Despite growing to higher cell densities, Fe-replete batch cultures were not silicate limited. It thus appears that Fe-stress contributes to increased silicate quotas in this organism. Doubling the silicate concentration of the medium alleviated silicate limitation and cells responded to Fe limitation by continuing cell division for a time while in vivo fluorescence remained constant. Measured quotas of cellular Fe were 370 attomoles⋅cell⁻¹ (1 attomole is 1 X 10⁻⁸ moles) for an Fe-replete culture and ranged from 50 to 100 attomoles⋅cell⁻¹ for Fe-deplete batch and chemostat cultures. Fe associated with the cell surface was not detected in cells grown in a batch culture which received no added Fe or in an Fe-limited chemostat culture. As a comparison, the dinoflagellate, Protogonyaulax tamarensis Clone D-255 grown in Fe-limited batch culture was found to have an Fe quota of 116 femtomoles⋅cell⁻¹ which, however, was in close agreement with T. pseudonana when Fe quotas were calculated on a per unit volume basis. A method for the measurement of Fe uptake by ⁵⁵Fe .labelling was developed which estimated an uptake rate of 90B attomoles⋅cell⁻¹⋅hr⁻¹ over a 10 min exposure to 450 nM Fe. Many of the methods developed and tested in this study should prove valuable in future study of the iron requirement of phytoplankton and their adaptations to low-Fe stress. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate