Showing papers by "McMaster University published in 1994"
Book•
01 Jan 1994TL;DR: A Course in Game Theory as discussed by the authors presents the main ideas of game theory at a level suitable for graduate students and advanced undergraduates, emphasizing the theory's foundations and interpretations of its basic concepts.
Abstract: A Course in Game Theory presents the main ideas of game theory at a level suitable for graduate students and advanced undergraduates, emphasizing the theory's foundations and interpretations of its basic concepts. The authors provide precise definitions and full proofs of results, sacrificing generalities and limiting the scope of the material in order to do so. The text is organized in four parts: strategic games, extensive games with perfect information, extensive games with imperfect information, and coalitional games. It includes over 100 exercises.
7,018 citations
TL;DR: The patient is a 28-year-old man whose acute onset of shortness of breath and vague chest pain began shortly after completing a 10-hour auto trip, and the physician is very apprehensive about his symptoms.
Abstract: CLINICAL SCENARIO You are back where we put you in the previous article1on diagnostic tests in this series on how to use the medical literature: in the library studying an article that will guide you in interpreting ventilation-perfusion (V/Q) lung scans. Using the criteria in Table 1, you have decided that the Prospective Investigation of Pulmonary Diagnosis (PIOPED) study2will provide you with valid information. Just then, another physician comes looking for an article to help with the interpretation of V/Q scanning. Her patient is a 28-year-old man whose acute onset of shortness of breath and vague chest pain began shortly after completing a 10-hour auto trip. He experienced several episodes of similar discomfort in the past, but none this severe, and is very apprehensive about his symptoms. After a normal physical examination, electrocardiogram and chest radiograph, and blood gas measurements that show a Pco2of
2,084 citations
TL;DR: A strategy of initial CABG surgery is associated with lower mortality than one of medical management with delayed surgery if necessary, especially in high-risk and medium- risk patients with stable coronary heart disease, and in low-risk patients, the limited data show a non-significant trend towards greater mortality with CABGs.
1,984 citations
TL;DR: You are back where you were in the previous article1 on diagnostic tests: in the library studying an article that will guide you in interpreting ventilation-perfusion (V/Q) lung scans.
Abstract: You are back where we put you in the previous article1 on diagnostic tests in this series on how to use the medical literature: in the library studying an article that will guide you in interpreting ventilation-perfusion (V/Q) lung scans. Using the criteria in Table 1, you have decided that the Prospective Investigation of Pulmonary Diagnosis (PIOPED) study2 will provide you with valid information. Just then, another physician
1,963 citations
TL;DR: The approach is contrasted with other approaches which use theoretical or knowledge-based models, and its potential is illustrated using a detailed simulation study of a semibatch reactor for the production of styrene-butadiene latex.
Abstract: Multivariate statistical procedures for monitoring the progress of batch processes are developed. The only information needed to exploit the procedures is a historical database of past successful batches. Multiway principal component analysis is used to extract the information in the multivariate trajectory data by projecting them onto low-dimensional spaces defined by the latent variables or principal components. This leads to simple monitoring charts, consistent with the philosophy of statistical process control, which are capable of tracking the progress of new batch runs and detecting the occurrence of observable upsets. The approach is contrasted with other approaches which use theoretical or knowledge-based models, and its potential is illustrated using a detailed simulation study of a semibatch reactor for the production of styrene-butadiene latex.
1,435 citations
TL;DR: An overview of multivariate statistical methods use for the statistical process control of both continuous and batch multivariate processes and examples are provided of their use for analysing the operations of a mineral processing plant, for on-line monitoring and fault diagnosis of a continuous polymerization process and for the on- line monitoring of an industrial batch polymerization reactor.
1,174 citations
TL;DR: It is shown that the first problem is NP-complete and the second is MAX SNP-hard; the complexity of tree alignment with a given phylogeny is also considered.
Abstract: We study the computational complexity of two popular problems in multiple sequence alignment: multiple alignment with SP-score and multiple tree alignment. It is shown that the first problem is NP-complete and the second is MAX SNP-hard. The complexity of tree alignment with a given phylogeny is also considered.
956 citations
TL;DR: A 78-year-old woman, now 10 days after abdominal surgery, who has become increasingly short of breath over the last 24 hours, is seen by a medical consultant asked by a surgical colleague to see her.
Abstract: CLINICAL SCENARIO You are a medical consultant asked by a surgical colleague to see a 78-year-old woman, now 10 days after abdominal surgery, who has become increasingly short of breath over the last 24 hours. She has also been experiencing what she describes as chest discomfort, which is sometimes made worse by taking a deep breath (but sometimes not). Abnormal findings on physical examination are restricted to residual tenderness in the abdomen and scattered crackles at both lung bases. Chest roentgenogram reveals a small right pleural effusion, but this is the first roentgenogram since the operation. Arterial blood gases show a Po 2 of 70 mm Hg, with a saturation of 92%. The electrocardiogram shows only nonspecific changes. You suspect that the patient, despite receiving 5000 U of heparin twice a day,
929 citations
TL;DR: A prospective multicenter cohort study in which potential risk factors for stress ulceration in patients admitted to intensive care units and the occurrence of clinically important gastrointestinal bleeding were evaluated.
Abstract: Background The efficacy of prophylaxis against stress ulcers in preventing gastrointestinal bleeding in critically ill patients has led to its widespread use. The side effects and cost of prophylaxis, however, necessitate targeting preventive therapy to those patients most likely to benefit. Methods We conducted a prospective multicenter cohort study in which we evaluated potential risk factors for stress ulceration in patients admitted to intensive care units and documented the occurrence of clinically important gastrointestinal bleeding (defined as overt bleeding in association with hemodynamic compromise or the need for blood transfusion). Results Of 2252 patients, 33 (1.5 percent; 95 percent confidence interval, 1.0 to 2.1 percent) had clinically important bleeding. Two strong independent risk factors for bleeding were identified: respiratory failure (odds ratio, 15.6) and coagulopathy (odds ratio, 4.3). Of 847 patients who had one or both of these risk factors, 31 (3.7 percent; 95 percent confidence ...
882 citations
TL;DR: A 55-year-old man has had his serum cholesterol level measured at a shopping mall 2 months ago and his cholesterol level was elevated, but before deciding on a treatment recommendation, you elect to find out just how big a reduction in the risk of CHD this patient could expect from a cholesterollowering diet or drug therapy.
Abstract: CLINICAL SCENARIO A 55-year-old man had his serum cholesterol level measured at a shopping mall 2 months ago. His cholesterol level was elevated and he comes to you, his primary care physician, for advice. He does not smoke, is not obese, and does not have hypertension, diabetes mellitus, or any first-order relatives with premature coronary heart disease (CHD). You repeat his cholesterol test and schedule a follow-up appointment. The test confirms an elevated cholesterol level (7.9 mmol/L [305 mg/dL]), but before deciding on a treatment recommendation, you elect to find out just how big a reduction in the risk of CHD this patient could expect from a cholesterollowering diet or drug therapy. THE SEARCH There are a number of cholesterol-lowering trials, and instead of trying to find and review all of the original studies yourself, you use Grateful Med to find a recent overview. On the first subject line you
816 citations
TL;DR: This work has developed a vector system based on use of Ad5 DNA sequences cloned in bacterial plasmids based on maximum flexibility, efficiency, and cloning capacity, and introduced a wild-type early region 3 into the vectors.
Abstract: Human adenoviruses (Ads) are attracting considerable attention because of their potential utility for gene transfer and gene therapy, for development of live viral vectored vaccines, and for protein expression in mammalian cells. Engineering Ad vectors for these applications requires a variety of reagents in the form of Ads and bacterial plasmids containing viral DNA sequences and requires different strategies for construction of vectors for different purposes. To simplify Ad vector construction and develop a procedure with maximum flexibility, efficiency, and cloning capacity, we have developed a vector system based on use of Ad5 DNA sequences cloned in bacterial plasmids. Expanded deletions in early region 1 (3180 bp) and early region 3 (2690 or 3132 bp) can be combined in a single vector that should have a capacity for inserts of up to 8.3 kb, enough to accommodate the majority of cDNAs encoding proteins with regulatory elements. Genes can be inserted into either early region 1 or 3 or both and mutations or deletions can be readily introduced elsewhere in the viral genome. To illustrate the flexibility of the system, we have introduced a wild-type early region 3 into the vectors, and to illustrate the high capacity for inserts, we have isolated a vector with two genes totaling 7.8 kb.
TL;DR: The recommendations for monitoring and selection of patients for liver biopsy identify patients at potential risk for CSLD, and thus significantly reduce the number or patients who would be exposed to this procedure.
Abstract: Methotrexate (MTX) has become an important drug in the treatment of rheumatoid arthritis (RA). The American College of Rheumatology convened a committee to assess the risks of development of clinically significant liver disease (CSLD) during MTX treatment, to evaluate the risk and role of surveillance liver biopsies, and to provide recommendations about monitoring patients for liver toxicity. The committee recommends obtaining liver blood tests (alanine aminotransferase [ALT], aspartate aminotransferase [AST], alkaline phosphatase, albumin, bilirubin), hepatitis B and C serologic studies, and other standard tests including complete blood cell count and serum creatinine tests prior to starting treatment with MTX. A pretreatment liver biopsy should be considered only for patients with a history of prior excessive alcohol consumption, persistently abnormal baseline AST values, or chronic hepatitis B or C infection. At intervals of every 4-8 weeks the AST, ALT, and albumin levels should be monitored. Routine surveillance liver biopsies are not recommended for RA patients receiving traditional doses of MTX. However, a biopsy should be performed if a patient develops persistent abnormalities on liver blood tests. These are defined as elevations (above the upper limit of laboratory normal) in the AST in 5 of 9 determinations within a given 12-month interval (6 of 12 if tests are performed monthly) or a decrease in serum albumin below the normal range. The recommendations for monitoring and selection of patients for liver biopsy identify patients at potential risk for CSLD, and thus significantly reduce the number or patients who would be exposed to this procedure. Close monitoring is essential to reduce the risk of unrecognized serious liver disease. These recommendations should be revised as necessary to reflect new and compelling information.
TL;DR: More detailed diagnostic methods based on interrogating the underlying PCA /PLS models are developed, which show those process variables which are the main contributors to any deviations that have occurred, thereby allowing one to diagnose the cause of the event more easily.
Abstract: Schemes for monitoring the operating performance of large continuous processes using multivariate statistical projection methods such as principal component analysis (PCA ) and projection to latent structures (PLS) are extended to situations where the processes can be naturally blocked into subsections. The multiblock projection methods allow one to establish monitoring charts for the individual process subsections as well as for the entire process. When a special event or fault occurs in a subsection of the process, these multiblock methods can generally detect the event earlier and reveal the subsection within which the event has occurred. More detailed diagnostic methods based on interrogating the underlying PCA /PLS models are also developed. These methods show those process variables which are the main contributors to any deviations that have occurred, thereby allowing one to diagnose the cause of the event more easily. These ideas are demonstrated using detailed simulation studies on a multisection tubular reactor for the production of lowdensity polyethylene.
TL;DR: It is reported that extremely short telomeres are maintained in metastatic cells of epithelial ovarian carcinoma and that tumor cells, but not isogenic nonmalignant cells, express telomerase, suggesting that progression of malignancy is ultimately dependent upon activation of telomersase and that telomerases inhibitors may be effective antitumor drugs.
Abstract: Telomeres fulfill the dual function of protecting eukaryotic chromosomes from illegitimate recombination and degradation and may aid in chromosome attachment to the nuclear membrane. We have previously shown that telomerase, the enzyme which synthesizes telomeric DNA, is not detected in normal somatic cells and that telomeres shorten with replicative age. In cells immortalized in vitro, activation of telomerase apparently stabilizes telomere length, preventing a critical destabilization of chromosomes, and cell proliferation continues even when telomeres are short. In vivo, telomeres of most tumors are shorter than telomeres of control tissues, suggesting an analogous role for the enzyme. To assess the relevance of telomerase and telomere stability in the development and progression of tumors, we have measured enzyme activity and telomere length in metastatic cells of epithelial ovarian carcinoma. We report that extremely short telomeres are maintained in these cells and that tumor cells, but not isogenic nonmalignant cells, express telomerase. Our findings suggest that progression of malignancy is ultimately dependent upon activation of telomerase and that telomerase inhibitors may be effective antitumor drugs.
TL;DR: This overview focuses on studies of the final and most clinically important stages of evaluation and examines controlled trials designed to measure the effects of CDSSs on clinician performance and patient outcomes.
Abstract: Objective: To review the evidence from controlled trials of the effects of computer-based clinical decision support systems (CDSSs) on clinician performance and patient outcomes. Data Sources: The ...
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TL;DR: A sign that the software engineering profession has matured will be that we lose our preoccupation with the first release and focus on the long-term health of our products as mentioned in this paper.
Abstract: Programs, like people, get old. We can't prevent aging, but we can understand its causes, take steps to limits its effects, temporarily reverse some of the damage it has caused, and prepare for the day when the software is no longer viable. A sign that the software engineering profession has matured will be that we lose our preoccupation with the first release and focus on the long-term health of our products. Researchers and practitioners must change their perception of the problems of software development. Only then will software engineering deserve to be called "engineering". >
TL;DR: The retrieval of studies of important clinical topics cited in MEDLINE can be substantially enhanced by selected combinations of indexing terms and textwords.
TL;DR: The construct validity of J. P. Meyer and N. J. Allen's (1991) 3-component model of organizational commitment was assessed by a confirmatory factor analysis of data from 2,301 nurses.
Abstract: The construct validity of J. P. Meyer and N. J. Allen's (1991) 3-component model of organizational commitment was assessed. Despite the large error components associated with some of the items from Meyer and Allen's scales, the existence of 3 facets of commitment (affective, continuance, and normative) was generally supported by a confirmatory factor analysis of data from 2,301 nurses. Moreover, some of the expected differential relationships of these facets to antecedents and outcomes of commitment were observed in both the nurse sample and a sample comprising 80 bus operators. However, the facets generally did not relate strongly or differentially to a set of rating and nonrating measures of job performance
TL;DR: A general internist is asked to see a 65-year-old man with controlled hypertension and a 6-month history of atrial fibrillation resistant to cardioversion, who has no evidence for valvular or coronary heart disease, and who shares concerns about the benefits of long-term anticoagulant therapy.
Abstract: CLINICAL SCENARIO You are a general internist who is asked to see a 65-year-old man with controlled hypertension and a 6-month history of atrial fibrillation resistant to cardioversion. Although he has no evidence for valvular or coronary heart disease, the family physician who referred him to you wants your advice on whether the benefits of long-term anticoagulants (to reduce the risk of embolic stroke) outweigh their risks (of hemorrhage from anticoagulant therapy). The patient shares these concerns and doesn't want to receive a treatment that would do more harm than good. You know that there have been randomized trials of warfarin for nonvalvular atrial fibrillation and decide that you'd better review one of them.
TL;DR: The Inflammatory Bowel Disease Questionnaire is a valid reliable assessment tool that reflects important changes in the health status of patients with IBD and should be used in future clinical trials in IBD.
TL;DR: This paper will explain the basics of factor analysis and provide some guidelines relating to how the results should be reported and how to interpret the results.
Abstract: Factor analysis is a technique which is designed to reveal whether or not the pattern of responses on a number of tests can be explained by a smaller number of underlying traits or factors. Similarly, it can be used to indicate whether or not the various items on a questionnaire can be grouped into a few clusters with each cluster reflecting a different construct. As with all multivariate statistical tests, it is quite powerful and can provide much information about the instruments being used. Similarly, there are many ways it can be abused and misinterpreted. This paper will explain the basics of factor analysis and provide some guidelines relating to how the results should be reported.
TL;DR: In this article, the authors propose space mapping (SM) for circuit optimization utilizing a parameter space transformation, which is demonstrated by the optimization of a microstrip structure for which a convenient analytical/empirical model is assumed to be unavailable.
Abstract: We offer space mapping (SM), a fundamental new theory to circuit optimization utilizing a parameter space transformation. This technique is demonstrated by the optimization of a microstrip structure for which a convenient analytical/empirical model is assumed to be unavailable. For illustration, we focus upon a three-section microstrip impedance transformer and a double folded stub microstrip filter and explore various design characteristics utilizing an electromagnetic (EM) field simulator. We propose two distinct EM models: coarse for fast computations, and the corresponding fine for a few more accurate and well-targeted simulations. The coarse model, useful when circuit-theoretic models are not readily available, permits rapid exploration of different starting points, solution robustness, local minima, parameter sensitivities, yield-driven design and other design characteristics within a practical time frame. The computationally intensive fine model is used to verify the space-mapped designs obtained exploiting the coarse model, as well as in the SM process itself. >
TL;DR: By expressing ICP47, HSV can evade detection by CD8+ T lymphocytes, perhaps explaining the predominance of CD4+ rather thanCD8+ HSV-specific CTLs in vivo.
TL;DR: Improvements in exercise tolerance and quality of life can be achieved and sustained for 6 months in patients undergoing respiratory rehabilitation compared with those receiving conventional care.
TL;DR: The quality of reports about drug and food interactions with warfarin was evaluated to address the fine points of therapy such as drug interactions, and it was essential to evaluate the quality of these studies.
Abstract: • Purpose: To evaluate the quality of studies about drugs and food interactions with warfarin and their clinical relevance. • Data Sources: MEDLINE and TOXLINE databases from 1966 to October 1993 using the Medical Subject Headings warfarin, drug interactions, and English only. • Study Selection: All articles reporting original data on drug and food interactions with warfarin. • Data Extraction: Each report, rated independently by at least two investigators (using causality assessment), received a summary score indicating the level of assur ance (level 1 = highly probable, level 2 = probable, level 3 = possible, and level 4 = doubtful) that a clini cally important interaction had or had not occurred. Inter-rater agreement was assessed using a weighted kappa statistic. • Results: Of 793 retrieved citations, 120 contained original reports on 186 interactions. The weighted kappa statistic was 0.67, representing substantial agreement. Of 86 different drugs and foods appraised, 43 had level 1 evidence. Of these, 26 drugs and foods did interact with warfarin. Warfarin's anticoagulant ef fect was potentiated by 6 antibiotics (cotrimoxazole, erythromycin, fluconazole, isoniazid, metronidazole, and miconazole); 5 cardiac drugs (amiodarone, clofibrate, propafenone, propranolol, and sulfinpyrazone); phenylbutazone; piroxicam; alcohol (only with concom itant liver disease); cimetidine; and omeprazole. Three patients had a hemorrhage at the time of a potentiating interaction (caused by alcohol, isoniazid, and phenyl butazone). Warfarin's anticoagulant effect was inhibited by 3 antibiotics (griseofulvin, rifampin, and nafcillin); 3 drugs active on the central nervous system (barbitu
TL;DR: A 76-year-old retired schoolteacher who has lived with her son since her husband died 6 years ago has become increasingly agitated and paranoid during the last year and you feel she has probable Alzheimer's disease.
Abstract: CLINICAL SCENARIO You are about to see a 76-year-old retired schoolteacher for the second time. You first saw her in the clinic a month ago because of cognitive problems. Your evaluation at that time included a Standardized Mini-Mental State Examination,1on which she scored 18 out of a possible 30 points, and a physical examination that was normal including no focal neurological signs. You arranged investigations for the treatable causes of dementia that were negative, and you thus feel she has probable Alzheimer's disease. The patient has lived with her son since her husband died 6 years ago. Her son thinks that she first developed significant problems with her memory about 3 years ago. However, she has become increasingly agitated and paranoid during the last year. She has refused to allow him to look after her financial affairs, despite the fact that she owns three pieces of property and
TL;DR: A new and important potential role for ACE inhibitors is suggested by the recent trials in patients with low ejection fraction, which documented a significant reduction in major ischemic events such as myocardial infarction, unstable angina, and the need for coronary revascularization procedures.
Abstract: A ngiotensin-converting enzyme (ACE) inhibitors are commonly used drugs in the management of a variety of cardiovascular diseases. They are effective antihypertensive agents.1-3 Early studies have demonstrated reductions in mortality and symptoms of heart failure in patients with severe congestive heart failure.4 More recently, clinical trials have demonstrated reductions in mortality and in hospitalizations for heart failure when these agents were used in patients with moderate left ventricular dysfunction, with and without overt heart failure, further expanding the clinical value of these drugs in the management of patients with cardiac diseases. These benefits have been observed consistently in several trials,5-7 in patients with ischemic and nonischemic causes for the left ventricular dysfunction and with or without recent myocardial infarction. The reductions in progressive heart failure and mortality in these patients are at least partly related to a beneficial effect on left ventricular remodeling and reductions in left ventricular enlargement.8-10 Other potential beneficial effects of these agents, such as regression of left ventricular hypertrophy and retardation of the rate of loss of renal function in patients with diabetic nephropathy, have been brought into focus by recent trials and also by experimental studies that explore their mechanisms of action. A new and important potential role for ACE inhibitors is suggested by the recent trials in patients with low ejection fraction, which documented a significant reduction in major ischemic events such as myocardial infarction, unstable angina, and the need for coronary revascularization procedures. In addition, parallel epidemiological, genetic, and experimental studies suggest that the renin-angiotensin-aldosterone system may have a role in the development of coronary artery disease
TL;DR: Large variation in WTP responses may compromise this measure's discriminant validity, but there is some evidence of convergent validity for WTP with preferences measured by standard gamble, and the test-retest reliability of WTP is comparable to those of other preference measures.
Abstract: The development of methods to measure willingness to pay (WTP) has renewed interest in cost-benefit analysis (CBA) for the economic evaluation of health care programs. The authors studied the construct validity and test-retest reliability of WTP as a measure of health state preferences in a survey of 102 persons (mean age 62 years; 54% male) who had chronic lung disease (forced expiratory volume < 70%). Interview measurements included self-reported symptoms, the oxygen-cost diagram for dyspnea, Short-Form 36 for general health status, rating scale and standard gamble for value and utility of current health state relative to death and healthy lung functioning, and WTP for a hypothetical intervention offering a 99% chance of healthy lung functioning and a 1% chance of death. WTP was elicited by a simple bidding game. To test for starting-point bias, the respondents were randomly assigned to one of five starting bids. All health status and preference measurements except WTP (controlling for income) showed significant (p < 0.05) difference between disease-severity groups (mild/moderate/severe). WTP was significantly (p = 0.01) associated with household income, but other health status and preference measure were not. The measure most highly correlated with WTP was standard gamble (r = -0.46). There was no association between starting bid and mean WTP adjusted for income and health status. The test-retest reliability of WTP was acceptable (r = 0.66) but lower than that for the standard gamble (r = 0.82).(ABSTRACT TRUNCATED AT 250 WORDS)