Showing papers by "University of Windsor published in 1989"

On measures of flexibility in manufacturing systems

Abstract: SUMMARY This paper presents measures which quantify the notion of how well manufacturing systems, in which machines are assigned to participate in tasks, can absorb changes in the environment. Several measures are proposed and their properties discussed. This paper takes the viewpoint that such measures are relative to reference task-sets.

A Childhood Learning Disability that Predisposes Those Afflicted to Adolescent and Adult Depression and Suicide Risk

Abstract: A particular subtype of learning disability (nonverbal learning disability) is described. This subtype of individuals with learning disability is seen to be at particular risk for depression and suicide. The origins of the study of this subtype of learning disability, its incidence in various forms of neurological disease, disorder, and dysfunction, and its behavioral and socioemotional manifestations (including its association with significant internalized forms of psychopathology) are described. A case history of a young woman who manifests this disability and who has attempted suicide on three occasions is also presented.

Patterns of benthic invertebrate assemblages in rivers of northwestern North America

Abstract: SUMMARY. 1. Biogeographical and on-site. hydrological variables were evaluated to determine spatial distribution of benthic invertebrate assemblages at 100 river sites in northwestern North America. 2. Results of cluster analysis suggested that the river sites comprised sixgroups (A-F), each supporting a characteristic invertebrate assemblage.Distinct groups were best represented by abundant Tricorythidae (C), Amphipoda (F), Rhyacophilidae and Systellognatha (E), and Elmidae and Hydroptilidae (A). Brachycentridae (B) and Oligochaeta (D) were widespread throughout the study area. 2. Both biogeographical and hydrological features contributed to the correct classification of site groupings characterized by distinctive fauna. However, biogeographical features were more useful than variables measured at the river site in discriminating among the site groupings.Groups C and F were most prevalent within the Hudson Bay drainage.Groups A, C and F were typically located within plains; group E sites were in mountainous regions. 4. The hydrological variables most useful in delineating site groupings were mean current velocity and mean depth. Slow, deep waters characterized amphipod sites; shallow, fast flowing waters occurred at Rhyacophilidae Sysellognatha sites. 5. Results substantiate previous views of a strong association between benthic invertebrates in small rivers and the terrestrial biome through which the river flows.

Polyphyletic origins of asexuality in daphnia pulex. i. breeding-system variation and levels of clonal diversity.

Abstract: There is growing evidence that transitions from sexual to asexual reproduction are often provoked by internal genetic factors rather than extrinsic selection pressures. In the cladoceran crustacean Daphnia pulex, the shift to asexuality has been linked to sex-limited meiosis suppression. Most populations of this species reproduce by obligate parthenogenesis, but cyclically parthenogenetic populations persist in the southern portion of its range. The meiosis-suppressor model predicts that asexuality in D. pulex has polyphyletic origins and that the coexistence of cyclically parthenogenetic lines with male-producing obligately asexual clones should be unstable. For the present study, we examined the genotypic structure of D. pulex populations from a region in which there is an abrupt microgeographical shift in breeding system. Populations in Michigan largely reproduce by cyclic parthenogenesis, while those in Ontario are obligately asexual. Allozyme studies on 77 populations from this area revealed 50 obligately asexual clones, divisible into two groups: one derived from a single parent species and the other derived via interspecific hybridization. Although nearly 50% of the clones retained male production, there was, as predicted, no evidence of coexistence between cyclically parthenogenetic populations and male-producing obligately asexual clones. The survey did, however, reveal a low incidence of cyclically parthenogenetic populations in Ontario. The high genotypic diversity of these populations suggests that they are not only resistant to meiosis suppression, but able to rework genetic variation gained from asexual clones into a sexual breeding system.

Plant reproductive strategies and resource allocation

Abstract: A major theme in plant evolutionary ecology concerns the allocation of resources to fitness-enhancing activities. Patterns of allocation have been regarded as reflecting evolved reproductive strategies. Here I review recent studies that focus on problems of resource allocation. These studies concern resource currencies, plant ontogeny and bud dynamics, reproductive costs, and clonal growth. While there is a certain amount of tension between the descriptive utility and the evolutionary validity of the reproductive strategy concept, the idea of strategy remains a robust one.

Polyphyletic origins of asexuality in daphnia pulex. ii. mitochondrial-dna variation.

Abstract: Allozyme studies of the cladoceran Daphnia pulex have shown that most populations reproduce by obligate parthenogenesis, although some cyclically parthenogenetic populations remain throughout the southern portion of its range. Clonal diversity within the obligate parthenogens is extremely high and has been attributed to the polyphyletic origin of asexuality. Specifically, it has been proposed that the clonal diversity in the obligate parthenogens was generated via the spread of a sex-limited meiosis suppressor through populations of a cyclically parthenogenetic ancestor. In this study, analysis of polymorphism of restriction-endonuclease sites in the mitochondrial genome, in conjunction with allozyme analysis, was used to determine whether obligate parthenogenesis has a monophyletic or polyphyletic origin in D. pulex. An allozyme survey of 77 populations from Ontario and Michigan was first conducted to determine breeding systems and levels of clonal diversity (Hebert et al., 1989). Mitochondrial-DNA variation was then surveyed in one isolate of each clone from each population reproducing by obligate parthenogenesis and in 2-4 isolates from each population reproducing by cyclic parthenogenesis. Seventeen restriction enzymes were used in this analysis. Thirty-five mitochondrial genotypes were found among the 36 obligate clones (as identified by allozyme analysis), while 17 mitochondrial genotypes were identified among 40 cyclic isolates from 14 populations. Five mitochondrial genotypes were found in both groups. Parsimony and phenetic-clustering methods were used to construct trees showing the genetic relationship among mitochondrial genotypes. The results clearly show that obligate parthenogenesis had a polyphyletic origin in this species. The close relationship between cyclic and obligate parthenogens in the Great Lakes region suggests that many obligate clones have recently been derived from cyclic populations and that the generation of clones is still occurring in this area. Patterns of clonal diversity based on the joint consideration of allozyme and mitochondrial-DNA data are discussed.

New transmission planning model

Abstract: A model for optimal long-range transmission planning is proposed. The model is capable of dealing with both static and dynamic modes of transmission planning. Given the existing network and anticipating a requirement for future facilities and loads, an accurate nonlinear cost function for the system is formulated. It includes both the fixed and the variable costs for all planned lines, in addition to the cost of the power losses. The cost function is minimized subject to demand satisfaction and overloading constraints. The model includes security constraints on bus voltage magnitudes and swing angles. The AC load flow solution is included in the optimization model. The results of applying the model to a previously reported power system from the literature are discussed. >

Volume-loss model for trace-element enrichments in mylonites

Abstract: Mylonites from three widely separated localities along the Fries ductile deformation zone in the Blue Ridge province show substantial enrichments in trace and minor elements (TiO{sub 2}, P{sub 2}O{sub 5}, Zr, Y, and V) and depletions in Rb and Sr relative to the protolith. Two end-member hypotheses can explain the enrichments: one involves partitioning to and from an infiltrating fluid and assumes that all the elements were mobile. The second hypothesis assumes the high-field-strength cations were largely immobile and that their enrichment is due to large volume losses in the mylonites. Modeling indicates that Ti is immobile for fluid/rock ratios as high as 10{sup 4}, and petrographic and modal data support a volume-loss mechanism. Volume loss was accommodated by loss of SiO{sub 2} and alkalies during feldspar dissolution. Calculated fluid/rock volume ratios required to produce the observed SiO{sub 2} losses (assuming Ti mobility) range from 70 to 600. Variable enrichments in P, Zr, Y, and V are attributed to selective mobility of these elements during fluid infiltration.

Machine grouping problem in cellular manufacturing systems ― an integer programming approach

Abstract: In this paper a methodology is proposed to group the machines in cellular manufacturing systems based on the tooling requirements of the parts, toolings available on the machines and the processing times. Two 0-1 integer programming formulations are proposed. These formulations assume that the part families are known. The first formulation groups the machines based on the compatibility of parts with machines. The second formulation groups the machines in order to minimise the cost of allocating the machines and the cost of intercell movement. These formulations take into account the limitations on the number of machines in a group and the number of machines available of a particular type. The application of these formulations is illustrated using an example.

Diffusion of organic penetrants through low density polyethylene (LDPE) films: Effect of size and shape of the penetrant molecules

Abstract: The diffusion coefficient at zero penetrant concentration D0 of dichloromethane, chloroform, carbon tetrachloride, cyclohexane, benzene, o-xylene, m-xylene, and p-xylene, and n-hexane in LDPE were measured at 25°C, using the desorption method. The D0 values obtained in this way are correlated with the size, shape, and chemical nature of the penetrant molecules. The temperature dependence of the diffusion coefficients of toluene and n-hexane in LDPE are also reported in the limited temperature range of 25–45°C. It indicates that, in spite of a size larger than that of toluene, n-hexane has a lower activation energy of diffusion.

Comparisons of Cutoff and Regression-Based Definitions of Reading Disabilities

Abstract: This study addressed the issue of specificity in reading disability by comparing two approaches to defining and selecting children with reading disabilities. One approach defined reading disability according to cutoff scores representing appropriate levels of intelligence and reading deficiency, whereas the other approach adjusted these scores for their intercorrelation through regression procedures. Results revealed clear differences in which children were identified as reading disabled according to the two definitions. However, differences in neuropsychological performance between children whose reading scores were discrepant or not discrepant with IQ were small and nonspecific for both definitions. The results of this study show that children identified as reading disabled vary according to the definition employed; at this point, there is little evidence suggesting any specificity of reading disability according to definition.

A study of the relationship between student final exam performance and simulation game participation

Abstract: Despite the proliferation and widespread usage of simulation games in the field of business education, the pedagogical value of this instructional aid remains unclear. The present study, using a controlled setting, sought to determine whether incorporating a business simulation game in a principles of marketing course improves the acquisition of marketing knowledge. The results suggest that simulation games are an effective means by which to improve quantitative skills but are not an effective means by which to improve the acquisition of applied or theoretical knowledge.

A systolic realization for 2-D digital filters

Abstract: Systolic hardware realizations for two-dimensional finite-impulse-response (FIR) and infinite-impulse-response (IIR) digital filters are presented. The structure permits the 2-D input data to be scanned row-wise and broadcasted one value at a time to various processing elements. Shift registers are used to store the required data needed by the 2-D recursive equation. A processing element can be implemented in VLSI, and as many of these as are required to satisfy the order of the filter can be used to build the total structure. >

Relation between cytochrome P450IA1 expression and estrogen receptor content of human breast cancer cells.

Abstract: Multidrug resistance (MDR) in an MCF-7 human breast cancer cell line (MCF7/AdrR) is associated with decreased drug accumulation and overexpression of P-glycoprotein as well as alterations in the levels of specific drug-metabolizing enzymes, including decreased activity of the phase I drug-metabolizing enzyme aryl hydrocarbon hydroxylase (AHH) and increased expression of the anionic form of the phase II drug-metabolizing enzyme glutathione S-transferase. Since the development of MDR in this MCF-7 cell line is also associated with a loss of estrogen receptors (ER), we have examined the expression of cytochrome P450IA1, the gene encoding AHH activity, in other breast cancer cell lines not selected for drug resistance but expressing various levels of ER. These studies show that a relationship exists between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-inducible AHH activity and the ER content in a series of breast cancer cell lines. In these cell lines expression of AHH activity is regulated, at least in part, ...

A degenerate extreme point strategy for the classification of linear constraints as redundant or necessary

Abstract: This paper presents a degenerate extreme point strategy for active set algorithms which classify linear constraints as either redundant or necessary. The strategy makes use of an efficient method for classifying constraints active at degenerate extreme points. Numerical results indicate that significant savings in the computational effort required to classify the constraints can be achieved.

Oscillatory convection in a viscoelastic fluid through a porous layer heated from below

Abstract: The stability of a viscoelastic fluid in a densely packed horizontal porous layer heated from below is considered using an Oldroyd model. Critical Rayleigh number, wave number, and frequency for overstability are determined by applying the linear stability theory. It is shown that the critical Rayleigh number is invariant under all relevant boundary combinations. Also, it is found that the effect of elasticity of the fluid is to destabilize the system and that of porosity is to stabilize the same. The limiting case of very high Prandtl number and the degenerate case corresponding to the Maxwell model are analyzed in some detail.

Examples of Measurement of Flexibility and Adaptivity in Manufacturing Systems

Abstract: This paper presents examples of recently developed measures of flexibility and adaptivity for machines and groups of machines in a manufacturing setting The flexibility measures depend on the set of tasks to be done relative to a background task set, the relative importance of the tasks and the efficiency of machines in doing them The measures of adaptivity relate flexibility measures in different situations, usually at different points in time

Patterns of genotypic diversity in Czechoslovakian Daphnia

Abstract: Patterns of allozyme diversity were studied in Czechoslovakian populations of six Daphnia species to ascertain their mode of reproduction, the incidence of interspecific hybrids, and the relationship between genotypic diversity and habitat permanency. All six species were shown to reproduce by cyclic parthenogenesis. D. pulex and D. pulicaria, two closely related species whose taxonomic validity has been questioned, showed little polymorphism but diagnostic gene substitutions confirmed their distinctiveness. Populations of the pond species D. magna and D. longispina were commonly polymorphic but showed infrequent Hardy–Weinberg deviations. D. galeata from pond habitats showed a moderate incidence of deviations, but reservoir populations showed consistent heterozygote excesses and non-random multilocus associations. F1 hybrids and backcross progeny between D. longispina and D. galeata were detected in a third of the ponds and comprised, on average, 5 per cent of the local populations. In reservoirs, F1 hybrids between D. galeata and D. cucullata were common, with a genotypically diverse group of hybrids dominating one site.

A comparison of tests of homogeneity of odds ratios in K 2 x 2 tables.

Abstract: We conducted a simulation study to determine the performance of nine procedures for testing the homogeneity of odds ratios in K 2 × 2 contingency tables. We recommend Tarone's approximate score test, based on the Mantel—Haenszel estimator of the common odds ratio, for use in practice. We also recommend a non-iterative statistic developed by Gart and based on the modified Woolf estimator of the common odds ratio for very large samples in balanced or mildly unbalanced designs. We base our recommendation of a statistic on its performance in terms of size and power in comparison with the other statistics considered.