Showing papers by "Dalhousie University published in 1971"

Particulate Organic Matter in Sea Water

Abstract: Publisher Summary The non-living organic matter in sea water is derived from a variety of plant sources, including phytoplankton, attached aquatic vegetation in shallow waters, macroscopic pelagic algae, and waterborne and windborne materials of terrestrial origin. The relative importance of these various sources cannot be stated precisely, but there is little doubt that phytoplankton is the most important source. Phytoplankton production, as determined by C14 fixation, falls within the range of 50-15Og of carbon per m2 in a year in the major ocean basins; however, some regions, notably the high arctic, are less productive than this and higher levels are attained in some coastal and estuarine waters and probably in oceanic areas of intense upwelling.

The annual cycle in quantity and composition of the zooplankton of the sargasso sea off bermuda. i. the upper 500 m1

Abstract: Zooplankton samples were collected at station “S” ( 32” 1.0’ N, 64” 30’ W), 24 km SE of Bermuda in 3,200 m of water, at monthly intervals from July 1968 to June 1969, over four depth intervals from the surface to 2,000 m. In the upper 500 m highest numbers were found in October and April; bctwccn 500 and 1,000 m the highest numbers were prcscnt in July, March, and May; from 1,000 to 1,500 m the numbers were highest in August, January, and March, In the deepest waters sampled numbers were highest in July, October, March, and May. The displacement volumes for the upper 500 m showed a pronounced April maximum; the October maximum in numbers, consisting of small copepods, was not reflected in the volumes. Larger organisms were more common in the dccpcr waters. In going down the water column, volumes were approximately halved over each lower depth interval, but mean numbers decreased greatly between the upper waters and those of the 500-1,000-m interval, indicating an increase in size of organisms between these two depth ranges. depth Crustacea increased in importance and in diversity below 500 m. Copepods comprised 707~ of the plankton of the upper 500 m and 85.2% in the deepest waters sampled, Pelagic ostracods were next in importance, but wcrc relatively less numerous below 1,500 m. IIighest numbers of Calanoid genera and ostracod spccics were noted between 500 and 1,500 m. Euphausiids were most mm~erous between 1,500 and 2,000 m with a November maximum. Tunicates, coelenterates, chaetognaths, Foraminifera, ptcropods, and various larval forms were most abundant in nunlbers and species in the upper waters, but occurred in small numbers below 500 m.

An analysis of overshadowing and blocking

Abstract: In classical aversive conditioning experiments, rats do not always learn about all aspects of a compound stimulus predicting shock. A strong stimulus may overshadow a weaker one; and pretraining on one component may block learning about a second component. These results have been explained either by appealing to a notion of selective attention, or by assuming that learning about one component is a function of prior response strength to the entire compound of which it forms a part. In Experiment I, overshadowing was demonstrated on the first trial of conditioning, i.e. before either component had acquired any response strength. In Experiment II, pretraining on one component resulted in complete failure to learn about a second component during compound training, but did not prevent additional learning about the first component. Both results were interpreted as supporting an attentional analysis of blocking and overshadowing.

Quartz: synthesis at Earth-surface conditions.

Abstract: Quartz has been crystallized directly from seawater at room temperature. This is the first time that identifiable quartz has been synthesized in aqueous solution at earth-surface conditions without the aging of an original amorphous precipitate. The concentration of dissolved silica in equilibrium with quartz at 20°C and 1 atmosphere is 4.4±0.3 parts per million, a value in agreement with the theoretical value obtained by a constant heat capacity fit of higher temperature equilibrium data. This experiment confirms the results of petrologic investigations which suggest that quartz precipitates directly from aqueous solution during chemical weathering and early diagenesis.

Isolation of cadmium-binding proteins.

Abstract: Un procede pour l'isolation des proteines combinees au Cd radioactif (109Cd) a ete mis au point. La methode ne detruit pas les proteines. D'autres proteines ayant des affinites pour les metaux lourds pourront ainsi etre isolees.

Hudson Geotraverse: Geology of the Mid-Atlantic Ridge at 45 degrees N

Abstract: A strip across the Crest Mountains and High-Fractured Plateau of the Mid-Atlantic Ridge has been surveyed systematically between latitudes 45 and 46° N. Continuous bathymetric, magnetic and gravimetric data have been obtained. Seismic refraction experiments have revealed a complex structure lineated parallel to the axis of the Ridge. Seismic reflexion studies have revealed a picture of the sediment cover, and have shown the possible existence of block faulting of the underlying rocks, with faults alined both parallel and at right angles to the axis of the Ridge. The major rock types found in 46 dredge stations can be grouped as follows: (1) Ubiquitous basalts and tuffs (ranging from theoleiites to alkali basalts, with a few ferro-basalts and high-Al basalts). Basalts rich in resorbed high-calcic plagioclase xenocrysts are common; these occur both on the slopes of shield volcanoes and in the deepest hole of the Median Valley. A nearby fault scarp yielded coarse-grained gabbros. (2) Serpentinized mafic and ultramafic rocks are not restricted to elongated, presumably blockfaulted seamounts, but are also common on the slopes of what had been interpreted on morphological grounds as shield volcanoes; they are absent, however, on the Median alley floor and its immediate scarp slopes. The pre-serpentinization rock types include dunites, harzburgites, gabbros, troctolitic gabbros and amphibolitic peridotites showing crude cumulate textures. (3) The lower parts of the steep inner walls of the Median Valley have yielded metabasalts and metadiabases showing alteration within the greenschist facies of etamorphism, whilst still retaining original igneous characteristics. (4) Restricted to the fault scarps of elongated seamounts further removed from the Median Valley are higher grade metamorphic rocks of the almandine amphibolite facies of metamorphism. These rocks have lost all igneous textures and exhibit a strong gneissic fabric. (5) Three localities yielded dioritic rocks in association with serpentinized ultramafics. The diorites vary in character from hornblende-rich quartz diorites to more siliceous, almost hornblende-free trondhjemites. The latter show considerable albitization. The whole suite of rocks shows great affinities with similar suites found as late stage intrusives in alpine-type ultramafic complexes. About 23% of the specimens collected included gneissic, granitic and sedimentary rock types of erratic origin, ice rafted into the area in the Pleistocene. A study of their distribution indicates that there are no erratics in the Median Valley, that they are scarce on the mountain ranges immediately flanking the Valley, but beyond these areas they are abundant and are randomly distributed over the whole area. Such a distribution may be a result of ocean-floor spreading, indicating that the Median Valley is younger than the last ice age, or that extrusions subsequent to the last ice age have engulfed any erratics present in the Median Valley. The thickness of manganese coating on extrusive rocks and their K/Ar and fission track ages increase systematically with distance on either side of the axis of the M.A.R., strongly supporting the ocean-floor spreading hypothesis. The ages and coatings both show a marked change in their rate of increase beyond a distance of 50 to 60 km on either side of the axis. The position at which this occurs coincides with the thickening in these areas of sediments found in the inter-volcanic valleys, and the morphological changes between the Crest Mountains and the High-Fractured Plateau. The combined data strongly suggest that there was either a quiescent period sometime in the Pliocene during which ocean-floor spreading was inactive, or that the rate of spreading had accelerated during the Pliocene from less than 1 cm a -1 to a computed 2.5 cm a -1 in Pleistocene times.

Calcium: Is It Required for Transmitter Secretion?

Abstract: Ethanol multiplies miniature end-plate potential frequency independently of calcium ion concentrations and also multiplies calcium-dependent depolarization-evoked quantal release, to the same extent. This result implies a final common pathway, requiring little or no calcium, for both kinds of transmitter secretion. Chlorpromazine and hypertonicity act similarly to ethanol, but also depress depolarization-secretion coupling.

Blocking as a function of novelty of CS and predictability of UCS

Abstract: Kamin (1969) reported that after rats had been trained with one CS predicting shock, they learned virtually nothing about a second CS added to the first to form a compound–-provided that the shock remained unchanged. If, however, the shock was either increased or omitted at the same time that the new CS was added, it acquired significant excitatory or inhibitory strength. Both these results were confirmed in the present experiment. In addition, however, it was found that this excitatory or inhibitory conditioning to the added element could itself be blocked if the shock remained unchanged for the first four trials after the addition of the new element. This finding implies that blocking is not due to any limitation on attentional or associative capacity, but rather occurs when subjects learn that a particular stimulus is redundant, i.e. that it predicts no change in reinforcement.

The american species of eubosmina seligo (crustacea, cladocera)

Abstract: Eubosmina is representeNd in the Americas by at least four species, of which two, E. coregoni ( Baird ) and E. Zongkpina ( Leydig ) , are Holarctic; E. hagmanni ( Stingelin ) and E. tubn the more widespread, E. hagmanni, is known from Tierra de1 Fuego and may occur in the Canaclian Arctic. The two can bc difficult to separate unless males arc present, as they rarely are. In typical summer populations, however, the female rostrum shows positive allometry in E. hagmanni but negative allometry in E. tubicen; the mucro shows zero or weakly negative allometry in E. hagmanni but positive allometry in E. tubicen. In no known locality do these two species occur together, but in a few New England and Canadian lakes, where E. longispina is present, populations that otherwise resemble E. tubicen show negative allometry of the mucro. This situation is provisionally attributed to character displacement.

Efficient Distribution of Resources Through Three Levels of Government

Abstract: This paper presents a model for determining how a central government can most efficiently allocate resources among other levels of government. The model explicitly includes the fact that lower levels of government can make independent decisions once they have been given resources by the central government. A key feature of the model is the mathematical formulation of the central government's objective of distributing resources efficiently, while at the same time being as fair as possible to all those receiving allocations. An algorithm for solving the model is presented along with a numerical example.

Absolute and relative measures of concentration reconsidered ‐ reply

Abstract: SUMMARY Frequent controversies on the mathematical consistency and the economic significance of measures of concentration suggest an analysis of the principles of concentration measurement. The well-known division in concentration measures and inequality measures is formalized with a catalogue of desirable properties of these measures. This way, a qualifying concentration measure corresponds to an inequality measure, and vice versa. The discussion of some concentration measures shows the superiority of the entropy measure because of its axiomatic foundation. However, antitrust authorities may prefer simpler measures such as the recently proposed ‘comprehensive concentration index’ and the ‘concentration ratios’ to observe concentrated industries. On the other hand, the entropy measure should be applied for a more detailed analysis of the dynamics of economic concentration.

Punishment: Method and Theory.

Abstract: A methodological framework for the analysis of punishment is outlined. The methodology, which is called a multiple-response base-line procedure, serves two purposes. First, it raises a number of new questions about the properties of punishment. Second, it permits the examination of some untested assumptions found in traditional punishment theory. Initial evidence obtained with the multiple-response methodology questions the validity of traditional theoretical assumptions and suggests two simple rules for predicting the properties of various punishment operations.

Anoxia-recovery cycle in ventricular muscle: action potential duration, contractility and ATP content.

Abstract: The action potential duration, tension, time to peak tension, mean rate of tension development, and ATP content of guinea pig ventricular muscle declined during 60 min of anoxic incubation. The decline in tension was closecorrelated with the decline in mean rate of tension development, whereas time to peak tension decreased in an S-shaped relationship with action potential duration decrease. When muscles were incubated under anoxic conditions for 5, 30, or 60 min then under control conditions for 30 min, the action potential duration and time to peak tension returned to control level; tension, mean rate of development, and ATP content did not recover to control level when the period of anoxia exceeded 5 min. During the first 10 min of re-oxygenation a transient overshoot of control value was noted in action potential duration and time to peak tension. The transient increase in time to peak tension was accompanied by a transient increase in tension. It was not dependent on the occurrence, or degree, of overshoot in action potential duration. Transient changes did not occur in mean rate of tension development. It has been concluded that the anoxia-induced decrease in tension is due to a decrease in the rate of tension development as a result of a decreased ATP suppl. Time to peak tension seems related to action potential duration and both are independent oftotal muscle ATP content.

Adenosinetriphosphate partition in cardiac muscle with respect to transmembrane electrical activity.

Abstract: The sensitivity of guinea-pig papillary muscle transmembrane electrical activity to alterations in medium glucose concentration increased with time of incubation under anoxic conditions. DNP at a concentration of 10−4 M produced a decrease in fresh papillary muscle action potential duration comparable to that produced by low medium glucose in muscle after prolonged anoxic incubation. 10−6 M DNP did not increase the decline in action potential duration of fresh papillary muscle caused by anoxic incubation in medium containing 5 mM glucose. The ATP content of ventricular strips fell to about 30% control during 60 min of anoxia but was maintained at a significantly higher level when the medium contained 50 mM rather than 5 mM glucose. In the presence of 10−4 M DNP the ATP content of strips fell to 25% control in 10 min and the increased loss was maintained throughout 60 min. During 120 min incubation in medium containing 5 mM glucose and oxygen, the ATP of strips was maintained but the action potential duration declined to 50% control. The results support the proposal that a close association exists between glycolytically produced ATP and transmembrane electrical activity. The effects of DNP on transmembrane electrical activity may be explained by an active depletion of ATP in addition to its uncoupling activity.

Perturbation theory for the radial distribution function

Abstract: Perturbation theory is used to consider expansions for the radial distribution function, g 2(r), of a fluid with a soft core. We consider the Lennard-Jones (12, 6) potential and divide it into repulsive and attractive regions. In the repulsive region we expand the function exp (β u(r))g 2(r) about a hard sphere value. For the first-order contribution of the attractive region we consider a simple approximation to the exact analytical expression. The resulting g 2(r) is accurate at densities below about ρσ 3=0·5.

Ecological energetics of Nerita (Archaeogastropoda, Neritacea) populations on Barbados, West Indies

Abstract: Population energy budgets estimated on the assumption of steady state conditions for Nerita tessellataGmelin, N. versicolorGmelin, and N. peloronta L. on Barbados, W. Indies, are presented. Large differences in population structure, and hence energetics, occurred at different localities along the beach. Relatively high proportions (81 to 88%) of the assimilated energy were lost via metabolism. Assimilation efficiencies ranged from 39 to 43%, net growth efficiencies from 5 to 13%, and ecological efficiencies from 3 to 7%. For each species, production (P), energy flow (A) and total energy consumption (C) were expressed as functions of animal size, in order to facilitate gross estimations of the energy components for other populations for which data on size-frequency and density are available. Respiration studies of all three species in the laboratory failed to detect differences between respiration rates in air or under seawater.

The pigeon’s concept of pigeon

Abstract: Pigeons were trained to discriminate between the presence and absence of a pigeon in photographic displays projected on a response key Irrelevant cues were reduced as much as possible, while the differences between the objects were of sufficient variety and complexity to ensure that mastery of the discrimination would require the use of a concept The Ss learned this discrimination very rapidly On a test given following training, the Ss showed almost complete transfer to new displays containing fancy breeds of pigeons and showed significantly less transfer to new displays containing other species of birds These results indicate that discrimination was based on a concept of “pigeon”

A review of the family Schistosomatidae: excluding the genus Schistosoma from mammals

Abstract: Identification of members of the family Schistosomatidae presents problems not only because of the imperfect state of their taxonomy, but also because no attempt has been made to collect and organise the available data. There are only two general keys on the schistosomes (Price, 1929 ; Yamaguti, 1958) both of which are incomplete. The result of this is that many authors, too numerous to mention, list genera which are no longer valid and erect new species without comparing them with species to which they are obviously closely related.

Electrical Conductivity Structure by Geomagnetic Induction at the Continental Margin of Atlantic Canada

Abstract: Summary Geomagnetic variations measured at 10 stations in Atlantic Canada show significant laterally inhomogeneous induction. Transfer functions giving the systematic dip angle and direction of the variation field lines have been computed for periods from 20s to 120min and the results numerically modelled. High electrical conductivity exists starting at a depth of 15 km or less under the continental shelf off Nova Scotia and Newfoundland and perhaps under the Bay of Fundy. The apparent coast effect with a maximum at 30-min period results from the contrast between the highly conducting shelf structure and the more resistive inland rocks. The most likely explanation of the high conductivity is that there is highly saline interstitial water in the lower part of a 10km sedimentary section associated with evaporite, salt layers, or that part of the crust is hydrated in this area. Strong electric currents flow in the various arms of the Gulf of St Lawrence for short period (10 s to 10 min) inducing fields. Numerical models show that they can be explained by local induction in the shallow sea water. The details of the current flow indicate that significant conductive channelling must occur. One station on the north shore of the St Lawrence River has large long period (30 min) anomalous vertical fields. They probably result from a contrast in deep conductivity between the Appalachian and Canadian Shield geological provinces.

Conduction electron scattering and the resistance of the magnetic elements

Abstract: This article opens with a brief survey on the effect of conduction electron scattering on the electrical resistance of non-magnetic metals. It then deals at greater length with recent work on the temperature-dependence of resistance of the magnetic rare-earth elements and of some transition metals, and includes several interesting problems which still await solution.

The release in vivo of dopamine synthesized from labelled precursors in the caudate nucleus of the cat.

Abstract: — To study the release of dopamine (DA) evoked in vivo from the caudate nucleus, a push-pull cannula was inserted into the head of the caudate nucleus of cats anaesthetised with pentobarbitone sodium (Nembutal), and the tissue in the vicinity of the cannula tip was continuously irrigated with either l-[14C]tyrosine or DL-[14C]3,4-dihydroxyphenylala-nine (DOPA). The contents of [14C]DA and of the [14C]acidic metabolites in the perfusates were determined after separation from the labelled precursors by column chromatography, TLC and solvent partition. During perfusion with radioactive tyrosine, only small quantities of [14C]DA appeared in the effluent while the concentrations of the [14C]acidic metabolites gradually increased during the course of the experiment. When [14C]DOPA was substituted for [14C]tyrosine, the proportion of precursor that was converted to DA and released into the effluent as the amine or as its acidic metabolites was increased ten-fold. In an attempt to increase the resting release of [14C]DA, D-amphetamine, tropolone or pheniprazine were individually added to the perfusion fluid. Each drug increased the content of [14C]DA in the perfusate, but the enhanced release was maintained only when pheniprazine was added during perfusion with [14C]DOPA. Stimulation of the rostral substantia nigra (A5-5) and the medial forebrain bundle caused, in a majority of experiments, a two-to five-fold increase in the concentration of labelled DA in the effluent. Stimulation of the substantia nigra at A4-0 did not enhance the release of [14C]DA from the caudate nucleus but did enhance the release from the putamen. Since the increase in the output of [14C]DA was independent of changes in the output of labelled acidic metabolites, the evoked release was apparently not attributable to changes in extracellular fluid dynamics.