Showing papers by "Government of Canada published in 1988"

Disruption of the Nitrogen Cycle in Acidified Lakes

Abstract: Experimental acidification of two small soft-water lakes caused nitrification to cease at pH values of 5.4 to 5.7. The resulting blockage of the nitrogen cycle caused a progressive accumulation of amnonium. When the epermental acidification of one of the lakes was ended and the pH was raised to 5.4, nitrification resumed after a time lag of 1 year.

Morphological and physiological development of olfactory receptor cells in rainbow trout (Salmo gairdneri) embryos.

Abstract: The morphological and functional differentiation of the olfactory receptor cells were investigated in developing rainbow trout (Salmo gairdneri) embryos by means of light and electron (transmission and scanning) microscopy and electrophysiology. Ciliated receptor cells first appeared when the olfactory placode was folded to form a groovelike structure rostrad to the eye at stage 24 (day 18; 18 days postfertilization). Ciliated receptor cells predominated until immature microvillar receptor cells developed in stage 28 (day 26) embryos. At stage 29, the day of hatching, the anterior edge of the olfactory epithelium contained only ciliated receptor cells, and the midregion contained both ciliated and microvillar receptor cells. Spontaneous neural firing activity was recorded from the olfactory mucosa as early as stage 25. The neural responses to amino acids were initially recorded from stage 26 embryos, containing sparse ciliated receptor cells with a few short cilia. The D-enantiomers of amino acids were less effective. From these results we concluded that in rainbow trout the olfactory receptor cell has two separate morphological forms, ciliated and microvillar. These are ontogenetically distinct; the ciliated receptor cells preceded the microvillar. The ciliated receptor cells respond to amino acid stimulation.

Effects on ionic composition of blood and tissues of Anodonta grandis grandis (bivalvia) of an addition of aluminum and acid to a lake

Abstract: To test the hypothesis that summer low pH, episodic events cause stress and mortality in aquatic organisms including mussels, alum (aluminum sulfate) was added near the point of inflow to Lake 114 in the Experimental Lakes Area, northwestern Ontario from 3 to 5 July 1984. Lake 114 was at pH 5.9 before the alum addition. The alum produced measured extremes of pH 4.5 and [Al] of 2,237 μg/L near the point of addition. This study examined the effects of the alum addition on ionic concentrations of blood and tissue (gills, adductor muscle, foot and visceral mass) of the floater mussel,Anodonta grandis grandis. Mussels were collected from a second lake, 377, and introduced into Lake 114 at five locations five days before the alum addition. In response to transfer from the oligotrophic, unmanipulated Lake 377 to acidified Lake 114 (pH 5.9), blood of mussels showed a marked elevation of [Ca++], decline in [Mg++] and a temporary increase in [Cl−] but no change in [Na+], [K+] or [SO4 =]. During the alum addition, in mussels near the point source of the alum addition, blood [Na+] and [Cl−] declined and [Ca++] became still more elevated. Mussels suffered no mortality associated with the alum addition and almost no mortality during 26 days in Lake 114. Gill increased in [Al], [Ca], [Mn], declined in [Na] and showed no change in [Cd] in mussels near the alum addition. Visceral mass and adductor muscle also had lower [Na] in mussels near the point of alum addition. We attribute the increase in blood [Ca++] to the dissolution of the Ca stores in the shell and/or mantle of mussels. This would provide protection to the mussels during short-term declines in pH such as spring or summer episodic events. Never-theless, chronic exposure to small decreases in pH by mussels, already near the limits for obtaining sufficient Ca++, might be intolerable. It follows that acidification to the pH of 5.9 of soft water lakes containing mussels would be expected to lead to the loss of A.g. grandis from these waters.

A modified tape-peel technique for preparing permanent qualitative microfossil slides

Abstract: A method is described for the preparation of permanent microfossil mounts directly transferred from the surface of frozen lake sediment cores. Particulate material is transferred from the freeze dried vertical surfaces of frozen cores and on to microscope slides using transparent adhesive tape and contact cement. The contact cement and organic matter are then removed by combustion and chemical means and the isolated siliceous microfossils fixed in a permanent mounting resin. The technique produces slides with undisturbed sediment stratigraphy and excellent optical quality and permits the study of core microstratigraphy using high resolution phase or interference contrast microscopy.

Multifont character recognition for typeset documents

Abstract: An optical character reader for processing typeset documents must be able to handle proportional spacing, the presence of touching characters and a wide variety of type fonts. This paper describes the design of a multifont character recognizer which uses a binary decision tree to classify a character on the basis of 197 geometric features. The algorithm for designing the decision tree is based upon an entropy minimization procedure, and makes no assumptions on the distribution or independence of the binary features. The decision tree classifier provides confidence measures which may be used to reduce the substitution error rate at the expense of higher rejection rates. Methods of reducing the overall error rate by combining the decision tree classifier with other classifiers were examined. In particular, the paper evaluates the performance of a classifier using a combination of multiple decision trees, template matching and contextual post-processing. Error rates were highly sensitive to typeface and varied between 10 percent and 0.1 percent. Computer processing times for the various stages of the system are presented.

Identifying factors affecting plantation performance in boreal forests of Ontario

Abstract: Plantation data from northern Ontario were subjected to stepwise regression analysis to express survival and total height as functions of site factors, planting stock characteristics and age for each of black spruce (Picea mariana [Mill.] B.S.P.), white spruce (P. glauca [Moench] Voss) and jack pine (Pinus banksiana Lamb.).

The merit principle in the provincial governments of Atlantic Canada

Abstract: The merit principle is the primary means of restraining or avoiding political influence in civil service employment. It has received a good deal of attention at the national level of government but much less so at the provincial level. This article is designed to provide an assessment for Atlantic Canada. The author reviews the background in Britain and Canada and, after identifying the main elements of the principle, as developed at the national level of government in Canada, deals separately with each of the four Atlantic governments. He concludes that the merit principle has had its ups and downs throughout the region and that its current status varies considerably from province to province. Sommaire: Dans le secteur de I'emploi de la Fonction publique, le principe de la selection selon le merite est le meilleur moyen le limiter l'influence de la politique, voire de l'eviter. Ce principe a fait l'objet de beaucoup d'attention au niveau du gouvernement federal, ce qui n'a pas ete autant le cas au niveau provincial. Dans cet article, I'auteur Bvalue la situation B ce sujet dans les quatre provinces de l'Atlantique du Canada. Il commence par passer en revue les donnees en Grande-Bretagne et au Canada, puis met au jour les principaux aspects du principe, tel qu'il a eteelabore au niveau du gouvernement federal, pour en arriver enfin a traiter separement chaque gouvernement des provinces de l'Atlantique. En conclusion, l'auteur dit que le principe de la selection selon le merite a connu des hauts et des bas dans les quatre provinces et, qu'a l'heure actuelle, la situation varie beaucoup de l'une B l'autre.

Economic evaluation of forest drainage and fertilization in northern Ontario peatlands with an investment decision model

Abstract: Drainage and fertilization of an existing peatland black spruce (Picea mariana (Mill.) B.S.P.) stand and 24 possible methods of planting a clear-cut area near Cochrane, Ontario were evaluated by means of a recently developed forestry investment decision model, “FIDME”.

Comparing Vectors of Adjusted Means when Covariance Matrices are Unequal

Abstract: The ability to distinguish between stocks of fish is of vital importance in fisheries management programs. Morphometric measurements are commonly employed to separate biological populations. Unique role of multivariate analysis of covariance in separating fish stocks has been recognized recently. However, fish populations frequently differ in their covariance matrices and sometimes also in vectors of slope (on the covariate) coefficients. In this article the following are presented: (a) a procedure for comparing adjusted (for variations in body sizes of specimens) mean vectors of populations with unequal covariance matrices and slopes, and (b) a study to distinguish between beaked redfishes based on the analysis of a real data set by this procedure. This will also serve as a numerical example.