Showing papers by "Queen's University published in 1991"

Rigor in qualitative research: the assessment of trustworthiness.

Abstract: Despite a growing interest in qualitative research in occupational therapy, little attention has been placed on establishing its rigor. This article presents one model that can be used for the assessment of trustworthiness or merit of qualitative inquiry. Guba's (1981) model describes four general criteria for evaluation of research and then defines each from both a quantitative and a qualitative perspective. Several strategies for the achievement of rigor in qualitative research useful for both researchers and consumers of research are described.

Origins of the Modern Mind: Three Stages in the Evolution of Culture and Cognition

Abstract: Prologue PART 1: The Need for a Theory of Cognitive Evolution Mental Architecture as an Emergent Phenomenon Culture as Evidence for Cognitive Structure The Organization of This Book PART 2:

A New Look at Electron Localization

Abstract: two-particle density for electrons of parallel spin, a function of two electrons’ coordinates (x, y , z and x’, y‘ , z‘) which gives the joint probability of finding one electron at position x , y , z and another electron of the same spin at position x’, y’ , z‘. The analysis showed that electrons of parallel spin restrict themselves to separate regions of space, and hence follows the notion of localized electron pairs. A well-known application of these concepts are the Gillespie and Nyholm

The epidemiology of pain in children and adolescents: a review.

Abstract: Epidemiology is the branch of health science that focuses on investigations of the distribution and determinants of disease or illness in defined populations. Epidemiological studies provide data crucial to the understanding of the etiology, natural history and impact, as well as the aggregation and transmission of a disease or condition. Such studies also document the interrelationships among risk factors associated with the syndrome being investigated. Understanding disorders in these terms is a prerequisite to their prevention and may be invaluable to their treatment. In chronic pain, as in most other chronic disorders, a major aspect of the burden of pain is the resultant changes in lifestyle that often accompany pain. The World Health Organization [65] has developed a model for the impact of diseases that has recently been applied to pain [36]. According to this model, four planes of experience can be described. The first plane is the underlying disease or disorder. The second plane, termed impairment, refers to symptoms including pain. The third plane is disability, which describes those activities that are curtailed as a result of the problem. The fourth plane, handicap, is the restriction of social roles. The relationship between planes of experience is not linear and the different factors influencing pain, disability and handicap are not well understood. Because pain, regardless of etiology, may be associated with extensive disability and handicap, the epidemiology of pain, disability and handicap merits considerable attention. Epidemiological studies of disability

Effects of inorganic n availability on algal photosynthesis and carbon metabolism

Abstract: The purpose of this contribution is to assess the effects of N-limitation on algal photosynthesis and address the key physiological and biochemical interactions that occur between the assimilation of inorganic nitrogen and algal photosynthesis and carbon metabolism

Option pricing with v. g. martingale components

Abstract: European call options are priced when the uncertainty driving the stock price follows the V. G. stochastic process (Madan and Seneta 1990). The incomplete markets equilibrium change of measure is approximated and identified using the log return mean. variance, and kurtosis. An exact equilibrium interpretation is also provided, allowing inference about relative risk aversion coefficients from option prices. Relative to Black-Scholes, V. G. option values are higher, particularly so for out of the money options with long maturity on stocks with high means. low variances, and high kurtosis.

Statistical process control procedures for correlated observations

Abstract: Measurements from industrial processes are often serially correlated. The impact of this correlation on the performance of the cumulative sum and exponentially weighted moving average charting techniques is investigated in this paper. It is shown that serious errors concerning the “state of statistical process control” may result if the correlation structure of the observations is not taken into account. The use of time series methods for coping with serially correlated observations is outlined. Paper basis weight measurements are used to illustrate the time series methodology.

An assessment of Chironomidae as quantitative indicators of past climatic change

Abstract: The distribution among Labrador (Canada) lakes of remains from 21 chironomid taxa was analysed by means of canonical correspondence analysis (CCA). Tests with partial CCA of three hypotheses revealed that the distributions of chironomid taxa were significantly correlated with summer surface-water temperature and maximum lake depth, but not sediment organic content. In addition, an exploratory CCA revealed possible relationships of chironomid fauna with residual longitude and Fe concentration. A weighted-averaging-regression/calibration model of the chironomid–temperature relationship (derived from a temperature-constrained CCA) allowed the summer surface-water temperature of lakes to be inferred from chironomid remains. Accurate quantitative reconstructions of late glacial and Holocene temperature variations should be possible from fossil Chironomidae.

Phase-based disparity measurement

Abstract: The measurement of image disparity is a fundamental precursor to binocular depth estimation. Recently, Jenkin and Jepson (in Computational Processes in Human Vision (V. Pylyshyn, Ed.), Ablex, New Jersey, 1988) and Sanger (Biol. Cybernet, 59, 1988 , 405–418) described promising methods based on the output phase behavior of bandpass Gabor filters. Here we discuss further justification for such techniques based on the stability of bandpass phase behavior as a function of typical distortions that exist between left and right views. In addition, despite this general stability, we show that phase signals are occasionally very sensitive to spatial position and to variations in scale, in which cases incorrect measurements occur. We find that the primary cause for this instability is the existence of singularities in phase signals. With the aid of the local frequency of the filter output (provided by the phase derivative) and the local amplitude information, the regions of phase instability near the singularities are detected so that potentially incorrect measurements can be identified. In addition, we show how the local frequency can be used away from the singularity neighbourhoods to improve the accuracy of the disparity estimates. Some experimental results are reported.

Psychological Adaptation of Chinese Sojourners in Canada

Abstract: Psychological adaptation during acculturation was studied among 68 Chinese sojourners (students and visiting scholars from China and Hong Kong), 28 Chinese immigrant and Chinese-Canadian students, 30 Chinese students and scholars in China, and 33 non-Chinese Canadian students. Each participant completed questionnaires pertaining to various aspects of their lives and personalities, including: health beliefs and behaviours; problems and ways of coping; social contact and acculturation attitudes; psychological and physical health; and subjective adaptation. The Chinese sojourners reported lower English fluency, lower ease of making friendships, more adaptation and communication problems, and lower subjective adaptation than non-Chinese Canadian, or Chinese-Canadian students. The Chinese sojourners experienced less desired and actual contact, more contact incongruity, more separation and less assimilation than Chinese-Canadian students. The Chinese sojourners reacted to their problems with less wishf...

Feedback gains for correcting small perturbations to standing posture

Abstract: A dynamical model of the neuro-musculo-skeletal mechanics of a cat hindlimb is developed to investigate the feedback regulation of standing posture under small perturbations. The model is a three-joint limb, moving only in the sagittal plane, driven by 10 musculotendon actuators, each with response dynamics dependent on activation kinetics and muscle kinematics. Under small perturbations, the nonlinear postural regulation mechanism is approximately linear. Sensors exist which could provide state feedback. Thus, the linear quadratic regulator is proposed as a model for the structure of the feedback controller for regulation of small perturbations. System states are chosen to correspond to the known outputs of physiological sensors: muscle forces (sensed by tendon organs), a combination of muscle lengths and velocities (sensed by spindle organs), joint angles and velocities (sensed by joint receptors), and motoneuron activities (sensed by Renshaw cells). Thus, the feedback gain matrices computed can be related to the spinal neural circuits. Several proposals for control strategy have been tested under this formulation. It is shown that a strategy of regulating all the states leads to controllers that best mimic the externally measured behavior of real cats. >

Solvent selection strategies for extractive biocatalysis.

Abstract: This report follows the development of systematic solvent screening strategies for the identification of superior pure solvents and introduces techniques for the identification of effective coextractants. Specifically, methods to predict the biocompatibility and extractant capability of solvents are discussed. Biocompatibility is predicted by using heuristic data or the correlations between bioactivity and the logarithm of the partition coefficient of the solvent or the concentration of solvent in the cell membrane. A computer program, known as the extractant screening program or ESP, has been developed to effectively predict the behavior of virtually any product in any solvent/aqueous system. It is demonstrated that a biocompatible yet poor solvent can be mixed with a toxic solvent that has better extractant properties to yield a mixture with improved solvent characteristics that is still biocompatible. The fact that solvents do not mix in an ideal manner is exploited by using ESP to identify solvent mixtures that are still biocompatible at relatively high concentrations of toxic solvent.

An Experimental Investigation of the Impact of Computer Based Decision Aids on Decision Making Strategies

Abstract: Although Decision Support Systems DSSs have been in use since the early seventies, there is as yet no strong theoretical base for predicting how a DSS will influence decision making Furthermore, the findings of various empirical studies on the outcomes of DSS use are often contradictory Consequently, there is a need in the Decision Support Systems field for theories or explanatory models to formulate hypotheses, to conduct research in a directed, parsimonious manner and to interpret findings in a coherent way This will assist both academics and practitioners interested in the use of information systems to support managerial workers This paper proposes the use of a cognitive effort model of decision making to explain decision maker behavior when assisted by a DSS The central proposition is that specific features can be incorporated within a DSS that will alter the effort required to implement a particular strategy, and thus influence strategy selection by the decision maker This was investigated in a series of three experimental studies which examined the influence of computer based decision aids on decision making strategies In the three experiments, subjects were given different degrees of support to deal with various components of cognitive effort processing effort, memory effort and information tracking effort associated with the strategies applicable to preferential choice problems The results show that decision makers tend to adapt their strategy selection to the type of decision aids available in such a way as to reduce effort These results suggest that the assumption that decision makers use a DSS exclusively to maximize decision quality is open to question DSS studies which consider the joint effects of effort and quality, or control one while manipulating the other, are more likely to provide consistent and interpretable results

Incidence of awareness with recall during general anaesthesia.

Abstract: Summary One thousand patients who were anaesthetised between February and April 1990 at University Hospital, Nottingham were interviewed between 20 and 36 hours after their operation. Patients under 16 years of age, those who had undergone obstetric or intracranial surgery, those who were unable to communicate and patients who were discharged from hospital before the postoperative visit were not interviewed. A standard set of questions was used to determine the incidences of recall of events and dreams during the operation. These incidences were 0.2% and 0.9% respectively, considerably lower than reported in previous comparable studies.

Detecting small, moving objects in image sequences using sequential hypothesis testing

Abstract: An algorithm is proposed for the solution of the class of multidimensional detection problems concerning the detection of small, barely discernible, moving objects of unknown position and velocity in a sequence of digital images. A large number of candidate trajectories, organized into a tree structure, are hypothesized at each pixel in the sequence and tested sequentially for a shift in mean intensity. The practicality of the algorithm is facilitated by the use of multistage hypothesis testing (MHT) for simultaneous inference, as well as the existence of exact, closed-form expressions for MHT test performance in Gaussian white noise (GWN). These expressions predict the algorithm's computation and memory requirements, where it is shown theoretically that several orders of magnitude of processing are saved over a brute-force approach based on fixed sample-size tests. The algorithm is applied to real data by using a robust preprocessing procedure to eliminate background structure and transform the image sequence into a residual representation, modeled as GWN. Results are verified experimentally on a variety of video image sequences. >

Analysis of equal gain diversity on Nakagami fading channels

Abstract: An infinite series for the complementary probability distribution function (CDF) of the signal-to-noise ratio (SNR) at the output of L-branch equal-gain (EG) diversity combiners in Nakagami (1960) fading channels is derived. The bit error rate for a matched filter receiver is analyzed for the L-branch EG combiner and different fading parameters. Both coherent phase shift keying (CPSK) and differential coherent phase shift keying (DCPSK) are considered. The effects of gain unbalance between branches on the probability distribution of the SNR and on the bit error rates are investigated. Bit error rate results are also obtained for coherent and noncoherent reception of frequency shift keying (FSK). The effects of gain unbalances on FSK modulations are also investigated. Bit error rates for EG combining on Rayleigh fading channels are obtained for L>2. These results are presented as a special case of the more generalized Nakagami fading model. >

Similarity of tactual and visual picture recognition with limited field of view

Abstract: Subjects attempted to recognize simple line drawings of common objects using either touch or vision. In the touch condition, subjects explored raised line drawings using the distal pad of the index finger or the distal pads both of the index and of the middle fingers. In the visual condition, a computer-driven display was used to simulate tactual exploration. By moving an electronic pen over a digitizing tablet, the subject could explore a line drawing stored in memory; on the display screen a portion of the drawing appeared to move behind a stationary aperture, in concert with the movement of the pen. This aperture was varied in width, thus simulating the use of one or two fingers. In terms of average recognition accuracy and average response latency, recognition performance was virtually the same in the one-finger touch condition and the simulated one-finger vision condition. Visual recognition performance improved considerably when the visual field size was doubled (simulating two fingers), but tactual...

Parallel cascade identification and kernel estimation for nonlinear systems.

Abstract: We consider the representation and identification of nonlinear systems through the use of parallel cascades of alternating dynamic linear and static nonlinear elements. Building on the work of Palm and others, we show that any discrete-time finite-memory nonlinear system having a finite-order Volterra series representation can be exactly represented by a finite number of parallel LN cascade paths. Each LN path consists of a dynamic linear system followed by a static nonlinearity (which can be a polynomial). In particular, we provide an upper bound for the number of parallel LN paths required to represent exactly a discrete-time finite-memory Volterra functional of a given order. Next, we show how to obtain a parallel cascade representation of a nonlinear system from a single input-output record. The input is not required to be Gaussian or white, nor to have special autocorrelation properties. Next, our parallel cascade identification is applied to measure accurately the kernels of nonlinear systems (even those with lengthy memory), and to discover the significant terms to include in a nonlinear difference equation model for a system. In addition, the kernel estimation is used as a means of studying individual signals to distinguish deterministic from random behaviour, in an alternative to the use of chaotic dynamics. Finally, an alternate kernel estimation scheme is presented.

Magnetic excitations in the heavy-fermion superconductor URu2Si2.

Abstract: Antiferromagnetic order and fluctuations in the heavy-fermion superconductor ${\mathrm{URu}}_{2}$${\mathrm{Si}}_{2}$ have been studied by magnetic neutron scattering. Below ${\mathit{T}}_{\mathit{N}}$=17.5 K, ${\mathrm{URu}}_{2}$${\mathrm{Si}}_{2}$ is a type-I antiferromagnet with an anomalously small ordered moment of (0.04\ifmmode\pm\else\textpm\fi{}0.01)${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$ polarized along the tetragonal c axis. Dispersive resonant excitations exist in the ordered state with a zone-center gap of 0.43 THz. The excitations are polarized along the ordered moment and have a large dipolar matrix element, which suggests that they are coupled transitions between singlet crystal-field-like states. For energy transfer above 3 THz, peaks have not been identified in the magnetic excitation spectra, but instead a continuous spectrum of scattering peaked around the ordering wave vector indicates the presence of overdamped antiferromagnetically correlated spin fluctuations. Upon heating above ${\mathit{T}}_{\mathit{N}}$, the resonant excitations abruptly become heavily damped but the magnetic scattering at higher energies does not change at ${\mathit{T}}_{\mathit{N}}$. Instead, the disappearance of the antiferromagnetic modulation of the higher-energy scattering coincides with the maximum in the resistivity of ${\mathrm{URu}}_{2}$${\mathrm{Si}}_{2}$.

The evaluation of error probabilities for intersymbol and cochannel interference

Abstract: An efficient series that can be used to calculate the probability of error in a binary symmetric channel with intersymbol interference and additive noise is derived. The series is derived by representing the noise complementary probability distribution function by an exact or approximate Fourier series. Bounds on the accuracy of the estimate are derived for Gaussian noise. Examples show that only a small numerical effort may be required to compute error probabilities of interest using the series. Applications to both finite and infinite intersymbol interference systems are discussed. A similar technique is used to derive series representations for the probability of error of additive noise channels with cochannel interference or with combined intersymbol and cochannel interferences. The accuracy of the results is bounded for Gaussian noise. >

Need the thumb be immobilised in scaphoid fractures? A randomised prospective trial

Abstract: Immobilisation of the thumb is widely believed to be important in the management of fractures of the carpal scaphoid. To assess the need for this, we randomly allocated 392 fresh fractures for treatment by either a forearm gauntlet (Colles') cast, leaving the thumb free, or by a conventional 'scaphoid' plaster incorporating the thumb as far as its interphalangeal joint. In the 292 fractures which were followed for six months, the incidence of nonunion was independent of the type of cast used.

The Behavior of Dense, Nonaqueous Phase Liquids in Fractured Clay and Rock

Abstract: This paper examines the behavior of dense, nonaqueous phase liquids (DNAPLs) in fractured clay and rock. The conditions under which a DNAPL will enter an initially water-saturated, rough-walled fracture are outlined and expressed in a number of ways, including the height to which a DNAPL pool can accumulate above a fracture prior to initial entry. To study the behavior of DNAPL in a rough-walled fracture following initial entry, numerical simulations are carried out both in the plane of a fracture using a discrete representation of fracture roughness, and at a larger scale of averaging using an equivalent homogeneous porous media approach. The simulations illustrate that DNAPL will migrate through the larger aperture regions of a fracture plane, and that the DNAPL has the potential to enter progressively smaller aperture fractures with depth as it migrates. Additional numerical simulations indicate that the time taken for a nonaqueous phase liquid to traverse a fractured aquitard is inversely proportional to the fracture aperture, the fracture dip from the horizontal, and the height of the pool collected above the aquitard. It is also demonstrated that upward hydraulic gradients across a fractured aquitard can significantly slow the downward rate of DNAPL migration while downward water gradients enhance the rate of DNAPL migration across the aquitard.