Ferroelectricity in ultrathin perovskite films

Understanding the suppression of ferroelectricity in perovskite thin films is a fundamental issue that has remained unresolved for decades. We report a synchrotron x-ray study of lead titanate as a function of temperature and film thickness for films as thin as a single unit cell. At room temperature, the ferroelectric phase is stable for thicknesses down to 3 unit cells (1.2 nanometers). Our results imply that no thickness limit is imposed on practical devices by an intrinsic ferroelectric size effect.     

Modelling hydrology and sulphate concentration in small catchments in Central Ontario

The Birkenes-Storgama model of hydrology and streamwater chemistry which was modified by Seipet al. (1985) to simulate data for the Harp Lake #4 sub-catchment was applied to the Harp Lake #3, #4, and #6 sub-catchments for the 1980 to 1984 period. The model was roughly calibrated using a readily available optimization procedure on a relatively limited suite of model parameters. The calibration period was much shorter (8 mo for the hydrology sub-model and 12 mo for the sulphate sub-model) and the confirmation period longer (about 3 yr) than used previously. A statistical assessment indicates that the hydrology sub-model performs with good reliability over the confirmation period, and the sulphate sub-model performs fairly well. The need for modification to the sulphate sub-model may be indicated. An important result is that the Birkenes-Storgama model can be applied at new temporal and spatial locations without extensive calibration, and produce useful simulations.     

Modelling the hydrological regimes in acidified watersheds

Application of a hydrological model to three Canadian watersheds forms part of a verification package to test its accuracy and portability. Agreement of model results with observed data on hydrograph, groundwater flow and snowpack is reasonably good. The model results are consistent with the observed pH and with many of the episodic events that have occurred in these acidified watersheds. Contrasts have also been made on the different calibrated coefficients at several locations in these watersheds. An attempt to relate them to the geology and soil characteristics at the site has led to realistic estimation of the soil contact times.     

The use of calibrated lakes and watersheds for estimating atmospheric deposition near a large point source

We have measured the input and output rates of substances to and from both lakes and watersheds in the Sudbury and Muskoka-Haliburton areas of Ontario. At the former location, we have conducted mass balance studies on 5 lakes and their watersheds for 2½ yrs. At the latter site, we have measured mass balances for 6 lakes and about 30 individual watersheds for the past 5 yrs. Substances studied included SO₄ ^2?, NO₃ ^?, NH₄ ⁺, H⁺, major cations (Ca²⁺, Mg²⁺, Na⁺, K⁺) and HCO₃ ^?. During the course of the investigation at Sudbury we have made several observations that indicate that the inputs of some substances, specifically SO₄ ^2? or SO₄ ^2?-precursors and strong acids, to lakes and watersheds are underestimated when measured as bulk deposition (i.e. by collection in a continuously open container): (a) The output of SO₄ ^2? from the calibrated watersheds was substantially greater than the input measured as bulk deposition. (b) The SO₄ ^2? concentrations of the lakes could not be explained on the basis of the measured inputs. An additional input directly to the lake surface was needed to obtain a mass balance. (c) The net input of acids measured as bulk deposition to the watersheds was much less than the acid consumed, which was estimated by the net output of Ca²⁺, Mg²⁺, Na⁺, K⁺, Al³⁺, and the net retention of NO₃ ^?. (d) The major cation content of the study lakes could be explained on the basis of weathering reactions in the lakes' watersheds only if the input of strong acid had been underestimated. When these observations were quantified, they indicated a major portion of the total input of SO₄ ^2?-precursors and of strong acid was not included in our bulk deposition measurements. Deposition of SO₂ is the most likely explanation for these observations.     

Transmission studies with the contagious equine metritis bacterium in albino Swiss mice

Aspects of experimental transmission of the causal bacterium of contagious equine metritis (CEM) to albino Swiss mice were investigated. Whereas infection was established in the majority of female mice, the organism was recovered from only a limited number of male mice after challenge. No clinical evidence of infection was observed in the experimental mice. There was only one instance of presumptive venereal transmission of the CEM bacterium. One third of infected females conceived and had normal litters.     

Effects of treatment with aspirin or aspirin/dipyridamole combination in heartworm-negative, heartworm-infected, and embolized heartworm-infected dogs.

To determine the drug dose required to inhibit platelet reactivity by at least 50%, 2 drug regimens were evaluated in heartworm-negative, heartworm-infected, and heartworm-infected dogs embolized with dead heartworms. Aspirin, or a combination of aspirin and dipyridamole, were administered to 2 groups of Beagles (n = 5 each) for 5 to 9 days; a third group of 5 Beagles served as nontreated controls. For heartworm-negative dogs, mean (+/- SD) aspirin dosage that inhibited collagen-induced platelet reactivity by at least 50% was 6 (+/- 2) mg/kg of body weight given once daily. The aspirin/diphridamole combination dosage was 1 mg of each drug/kg given every 12 hours. All dogs (n = 15) were implanted with 7 adult heartworms each and remedicated (or not treated) beginning at 21 days after heartworm implantation. In heartworm-infected dogs, mean aspirin dosage required to inhibit collagen-induced platelet reactivity greater than or equal to 50% was 10 (+/- 6) mg/kg. Mean dosage of aspirin/dipyridamole combination was 1.6 +/- (0.5) mg of each drug/kg given every 12 hours. When platelet reactivity in response to collagen was determined to be inhibited by at least 50% in all medicated dogs, each dog (n = 15) was embolized with 7 dead adult heartworms to mimic heartworm adulticidal treatment. Platelet reactivity was monitored for 21 days after treatment, and drug dose was adjusted to maintain platelet inhibition by at least 50%. In embolized dogs, mean aspirin dosage was 17 (+/- 14) mg/kg given once daily. Mean dosage of the aspirin/dipyridamole combination was 2.8 (+/- 1.3) mg of each drug/kg given every 12 hours. All dogs (n = 15) were euthanatized 21 days after heartworm embolization. Each lung lobe was evaluated for severity of lesions and presence of organized or fibrinous thrombi. Lesion severity in the aspirin- and aspirin/dipyridamole-treated dogs was not significantly different from that in control dogs.     

Identification of an Intrinsic Platelet Function Defect in Spitz Dogs

A recently identified intrinsic platelet function defect in 2 Spitz dogs is described. Both affected dogs had a history of chronic intermittent bleeding primarily from the nasal, oral, and gastrointestinal mucosa. Platelet aggregation in response to adenosine diphosphate (ADP), collagen, and platelet activating factor (PAF) was absent; however, platelet shape change did occur. Platelets aggregated in response to gamma thrombin, although a delayed onset and a reduced velocity of aggregation were present. Platelet ¹⁴C-serotonin release was diminished in response to collagen and PAF. Glycoprotein Illa was detected on the surface of platelets by flow cytometry. Platelets were morphologically normal under light and electron microscopy. Two male Spitz dogs, related to one of the affected dogs, did not have a bleeding diathesis. Collagen-induced platelet aggregation, however, was diminished in these 2 dogs. This platelet defect most closely resembles the defect described in Basset hounds.     

The economics of systems research

There are three broad aspects of Systems Research worthy of particular consideration by professional personnel earning their keep within or about the agricultural research system. I will discuss these three aspects seriatim. The first is the conjecture that the systems approach constitutes a technological change in our mode of thinking about the world of such magnitude as to imply that we are now moving from one sociotechnical age to another. The second aspect, a corollary of the first, is the use of the systems approach as a framework for the selection of research programmes. The third, which also follows from the first, is the efficiency of conducting research on a systems basis. Many would think of this last aspect of efficiency as constituting ‘the economics of systems research’, but I believe the systems approach, via the first two aspects I have mentioned, has far wider implications of economic import for agricultural research.