Showing papers by "University of Toronto published in 1975"

Depth of processing and the retention of words in episodic memory.

Abstract: SUMMARY Ten experiments were designed to explore the levels of processing framework for human memory research proposed by Craik and Lockhart (1972). The basic notions are that the episodic memory trace may be thought of as a rather automatic by-product of operations carried out by the cognitive system and that the durability of the trace is a positive function of "depth" of processing, where depth refers to greater degrees of semantic involvement. Subjects were induced to process words to different depths by answering various questions about the words. For example, shallow encodings were achieved by asking questions about typescript; intermediate levels of encoding were accomplished by asking questions about rhymes; deep levels were induced by asking whether the word would fit into a given category or sentence frame. After the encoding phase was completed, subjects were unexpectedly given a recall or recognition test for the words. In general, deeper encodings took longer to accomplish and were associated with higher levels of performance on the subsequent memory test. Also, questions leading to positive responses were associated with higher retention levels than questions leading to negative responses, at least at deeper levels of encoding. Further experiments examined this pattern of effects in greater analytic detail. It was established that the original results did not simply reflect differential encoding times; an experiment was designed in which a complex but shallow task took longer to carry out but yielded lower levels of recognition than an easy, deeper task. Other studies explored reasons for the superior retention of words associated with positive responses on the initial task. Negative responses were remembered as well as positive responses when the questions led to an equally elaborate encoding in the two cases. The idea that elaboration or "spread" of encoding provides a better description of the results was given a further boost by the finding of the typical pattern of results under intentional learning conditions, and where each word was exposed for 6 sec in the initial phase. While spread and elaboration may indeed be better descriptive terms for the present findings, retention depends critically on the qualitative nature of the encoding operations performed; a minimal semantic analysis is more beneficial than an extensive structural analysis. Finally, Schulman's (1974) principle of congruity appears necessary for a complete description of the effects obtained. Memory performance is enhanced to the extent that the context, or encoding question, forms an integrated unit with the word presented. A congruous encoding yields superior memory performance because a more elaborate trace is laid down and because in such cases the structure of semantic memory can be utilized more effectively to facilitate retrieval. The article concludes with a discussion of the broader implications of these data and ideas for the study of human learning and memory,

The internal model principle for linear multivariable regulators

Abstract: Necessary structural criteria are obtained for linear multivariable regulators which retain loop stability and output regulation in the presence of small perturbations, of specified types, in system parameters. It is shown that structural stability thus defined requires feedback of the regulated variable, together with a suitably reduplicated model, internal to the feedback loop, of the dynamic structure of the exogenous reference and disturbance signals which the regulator is required to process. Necessity of these structural features constitutes the ‘internal model principle’.

Antipsychotic drugs: direct correlation between clinical potency and presynaptic action on dopamine neurons

Abstract: Neuroleptic (antipsychotic) drugs inhibited the electrically stimulated release of [3-H] dopamine from rat striatal slices. The concentrations for 50 percent inhibition (ranging from 11.5 nanomolar for spiroperidol to 800 nanomolar for thioridazine) correlated closely with the average daily dosages of 25 neuroleptic drugs used clinically for schizophrenia. The correlation includes butyrophenones, phenothiazines, reserpine, pimozide, clozapine, and (plus)- butaclamol. Clinically inactive isomers [trans-thiothixene, trans-flupenthixol, and (minus)-butaclamol] required 20 to 1000 times higher concentrations than the active isomers to inhibit release. Compared to the inhibition of [3-H] dopamine release, much higher neuroleptic concentrations were needed to inhibit the electrically stimulated release of other neurotransmitters--[3-H] acetylcholine, [3-H-a1 (gamma-aminobutyric acid). The neuroleptic drugs may block the presynaptic coupling between impulse and neurosecretion.

On the flexibility offered by state feedback in multivariable systems beyond closed loop eigenvalue assignment

Abstract: A characterization is given for the class of all closed loop eigenvector sets which can be obtained with a given set of distinct closed loop eigenvalues using state feedback. It is shown, furthermore, that the freedom one has in addition to specifying the closed loop eigenvalues is precisely this: to choose one set of closed loop eigenvectors from this class. Included in the proof of this result is an algorithm for computing the matrix of feedback gains which gives the chosen closed loop eigenvalues and eigenvectors. A design scheme based on these results is presented which gives the designer considerable freedom to choose the distribution of the modes among the output components. One interesting feature is that the distribution of a mode among the output components can be varied even if the mode is not controllable.

Partial-Response Signaling

Abstract: This paper presents a unified study of partial-response signaling (PRS) systems and extends previous work on the comparison of PRS schemes. A PRS system model is introduced which enables the investigation of PRS schemes from the viewpoint of spectral properties such as bandwidth, nulls, and continuity of derivatives. Several desirable properties of PRS systems and their relation to system functions are indicated and a number of useful schemes, some of them not previously analyzed, are presented. These systems are then compared using as figures of merit speed tolerance, minimum eye width, and signal-to-noise ratio (SNR) degradation over ideal binary transmission. A new definition of speed tolerance, which takes into account multilevel outputs and the effect of sampling time, is introduced and used in the calculation of speedtolerance figures. It is shown that eye width, a performance measure that has not been used previously in comparing PRS systems, can be calculated analytically in many cases. Exact values as well as bounds on the SNR degradation for the systems under consideration are presented. The effect of precoding on system performance is also analyzed.

Economic Order Quantities with Inflation

Abstract: The classical EOQ formula assumes that all relevant costs and prices are constant. In this paper it is shown that with inflation the choice of the inventory carrying charge used in the EOQ formula ...

Fast and accurate switching transient calculations on transmission lines with ground return using recursive convolutions

Abstract: The paper presents a new approach to the calculation of transients on transmission lines with frequency-dependent parameters. Its purpose is to obtain significant computer-time savings by avoiding convolutions. This is achieved by approximating all line and ground distortions and also time variable characteristic admittances by exponential functions, i.e. solutions of linear differential equations. The method produces a simple Norton-type line equivalent which permits its incorporation into an existing system representation like the B.P.A. program for the calculation of transients. The program has been tested on systems of different degrees of complexity and proved to be superior, in terms of speed and accuracy, to other advanced methods.

Multivariable tuning regulators: The feedforward and robust control of a general servomechanism problem

Abstract: A new notion of compensator identification, as opposed to the conventional plant identification problem, is introduced in this paper. It is assumed that it is desired to synthesize a robust feedforward-feedback controller for an unknown plant so that asymptotic tracking, in the presence of disturbances, occurs. The only assumptions made regarding the description of the plant model are that 1) the plant is linear and time-invariant and 2) the uncontrolled plant is stable. Note that it is assumed that the order of the plant model is unknown. It is assumed that the control inputs to the plant can be excited, that the outputs of the plant which are desired to be regulated can be measured, and that the class of disturbance inputs and reference inputs is known. In addition, it is also assumed in the feedforward controller case, that the disturbance inputs can be measured and be excited; this assumption is not required in the robust feedback controller case. Necessary and sufficient conditions which allow the robust feedforward-feedback compensator to be synthesized so that the controlled system is stable and so that asymptotic tracking, in the presence of both measurable and unmeasurable disturbances, occurs are obtained. An algorithm which allows the controllers to be synthesized is given. Some numerical examples are included to illustrate the results.

Estradiol-17beta biosynthesis in cultured granulosa cells from hypophysectomized immature rats; stimulation by follicle-stimulating hormone.

Abstract: Granulosa cells isolated from the ovaries of hypophysectomized immature rats synthesize and secrete estradiol-17² and estrone when grown for 2 days in monolayer culture in a synthetic medium containing testosterone (0.5 μM) and a highly purified folliclestimulating hormone (FSH) preparation (0.25 μg/ml). Secretion is negligible in the absence of either testosterone or FSH, and a highly purified luteinizing hormone (LH) preparation (0.25 μg/ml) was without significant stimulatory effect. It is concluded that FSH regulates estrogen biosynthesis in granulosa cells of hypophysectomized rats by a specific stimulation of the aromatizing enzyme system.

COMPARING NUMERICAL METHODS FOR STIFF SYSTEMS OF O.D.E :s

Abstract: This paper describes a technique for comparing numerical methods that have been designed to solve stiff systems of ordinary differential equations. The basis of a fair comparison is discussed in detail. Measurements of cost and reliability are made over a collection of 25 carefully selected problems. The problems have been designed to show how certain major factors affect the performance of a method. The technique is applied to five methods, of which three turn out to be quite good, including one based on backward differentiation formulas, another on second derivative formulas, and a third on extrapolation. However, each of the three has a weakness of its own, which can be identified with particular problem characteristics.

A simplified scoring system for the post-operative recovery room.

Abstract: A new and very simple scoring system for recording post-anaesthetic recovery is described. When numerical values are assigned to factors indicating recovery progress or lack of it is obvious. The records may have medico-legal value. It can be incorporated into the Recovery Room Record.

Charge densities and interionic potentials in simple metals: Nonlinear effects. II

Abstract: We present nonlinear self-consistent calculations of the charge density induced by isolated ${\mathrm{Li}}^{+}$, ${\mathrm{K}}^{+}$, ${\mathrm{Mg}}^{++}$, ${\mathrm{Al}}^{+++}$, and ${\mathrm{Ca}}^{++}$ ions when placed in an electron gas of the appropriate metallic density. By comparison with linear-response theory we show that in the first four metals nonlinear effects in the response of the conduction electrons to the ionic perturbations play an important role in determining the charge density and the interionic potential. However as in the case of Na studied in the previous paper these nonlinear effects can be simulated by using a suitably adjusted model potential. The calculated phonon dispersion curves for Li, K, and Al agree very well with experiment. Nonlinear effects are also very likely to be important in Ca but further work is necessary before conclusions can be drawn.

The robust decentralized control of a general servomechanism problem

Abstract: The decentralized robust control of a completely general servomechanism problem is considered in this paper. Necessary and sufficient conditions, together with a characterization of all decentralized robust controllers which enables asymptotic tracking to occur, independent of disturbances in the plant and perturbations in the plant parameters and gains of the system, is obtained. A new type of compensator called a decentralized servo-compensator which is quite distinct from an observer is introduced. It is shown that this compensator, which corresponds to an integral controller in classical control theory, must be used in any decentralized servomechanism problem to assure that the controlled system is stablizable and achieves robust control; in particular, it is shown that a decentralized robust controller of a general servomechanism problem consists of two devices (i) a decentralized servo-compensator and (ii) a decentralized stabilizing compensator. It is then shown that, under certain mild conditions, there almost always is a solution to the robust decentralized servomechanism problem for any composite system consisting of a number of subsystems interconnected in any arbitrary manner. This last observation has important implications for process control.

On pole assignment in linear multivariable systems using output feedback

Abstract: The general problem of pole assignment in a linear, time-invariant multivariable system via output feedback is considered. It is shown that given a controllable-observable system ( C,A,B ) in which A \in R^{n \times n} , rank B = m , rank C = r , then for almost all ( B,C ) pairs, \min (n,m + r-1) poles can be assigned arbitrarily close to \min (n, m + r-1 ) specified symmetric values by using output feedback.

Thermodynamics of CuAlO2 and CuAl2O4 and Phase Equilibria in the System Cu2O-CuO-Al2O3

Abstract: The standard Gibbs free energies of formation of CuAlO2 and CuAl2O4 were determined in the range 700° to 1100°C, using emf measurements on the galvanic cells (1) Pt,CuO +] Cu2O/CaO-ZrO2/O2,Pt; (2) Pt,Cu +] CuAlO2+] Al2O3/CaO-ZrO2/ Cu +] Cu2O,Pt; and (3) Pt,CuAl2O4+] CuAlO2+]Al2O3/CaO-ZrO2/O2,Pt. The results are compared with published information on the stability of these compounds. The entropy of transformation of CuO from tenorite to the rock-salt structure is evaluated from the present results and from earlier studies on the entropy of formation of spinels from oxides of the rock-salt and corundum structures. The temperatures corresponding to 3-phase equilibria in the system Cu2O-CuO-Al2O3 at specified O2 pressures calculated from the present results are discussed in reference to available phase diagrams.

Freud and his followers

Abstract: In the late 1890s Sigmund Freud (1856–1939), who had been trained as a Viennese neurologist, created a new field, psychoanalysis, which was designed to understand and treat neurotic afflictions. Although not a political thinker per se, Freud contributed indirectly, and some of his followers directly, to modern political theory. Politically, Freud was something of a conservative liberal, sceptical in outlook and suspicious of utopian schemes. His followers did not always follow him faithfully down the trail he had blazed in the new discipline of psychoanalysis; nor did all agree with his political views. Some were conservative to the point of reaction, others radical Marxists and utopians. Some revised Freudian theory almost beyond recognition. All were alike, however, in finding in Freud the outline and essentials of a new and fruitful way of thinking about man and society. Freud’s thought An essential key to Freud’s thinking about psychopathology lies in the character of the last days of the Hapsburg Empire. A yawning gulf between reality and official ideology stimulated a general intellectual revolt and a search for the actualities beneath the pious formulae of public truth. This uprising was led by those ideally placed to see the discrepancy because they had nothing to gain from accepting the official view: the educated Jews. Mordant irony was their weapon for piercing the veil of the structure of formal beliefs. The cultural conflict between East and West that had its vortex in Vienna’s cosmopolitan intellectual life, and the sense that liberal culture was on the verge of being undermined, would be reflected throughout Freud’s mature thought (Zweig 1953; Roazen 1968; Johnston 1972; Schorske 1979).

Memorial Consequences of Automatized Encoding.

Abstract: The first experiment tracked the acquisition of skilled reading as college students read as many as 160 pages of geometrically inverted text. The logarithm of reading time decreased linearly as a function of the logarithm of amount of practice, and performance on inverted text approached performance on normal text remarkably rapidly. The second experiment assessed the consequence for memory of skill at reading. Students unpracticed at reading inverted text remembered for lengthy intervals the inverted sentences they read; when students acquired skill with the typography, their memory for inverted sentences was poorer. The results are interpreted in terms that emphasize an operational basis to memory—pattern-analyzing procedures rather than conscious contents. This view is contrasted with three other accounts of recognition.