Showing papers by "University of Washington published in 1992"

Risk and protective factors for alcohol and other drug problems in adolescence and early adulthood: Implications for substance abuse prevention.

Abstract: The authors suggest that the most promising route to effective strategies for the prevention of adolescent alcohol and other drug problems is through a risk-focused approach. This approach requires the identification of risk factors for drug abuse, identification of methods by which risk factors have been effectively addressed, and application of these methods to appropriate high-risk and general population samples in controlled studies. The authors review risk and protective factors for drug abuse, assess a number of approaches for drug abuse prevention potential with high-risk groups, and make recommendations for research and practice.

Performing the exact test of Hardy-Weinberg proportion for multiple alleles.

Abstract: SUMMARY The Hardy-Weinberg law plays an important role in the field of population genetics and often serves as a basis for genetic inference. Because of its importance, much attention has been devoted to tests of Hardy-Weinberg proportions (HWP) over the decades. It has long been recognized that largesample goodness-of-fit tests can sometimes lead to spurious results when the sample size and/or some genotypic frequencies are small. Although a complete enumeration algorithm for the exact test has been proposed, it is not of practical use for loci with more than a few alleles due to the amount of computation required. We propose two algorithms to estimate the significance level for a test of HWP. The algorithms are easily applicable to loci with multiple alleles. Both are remarkably simple and computationally fast. Relative efficiency and merits of the two algorithms are compared. Guidelines regarding their usage are given. Numerical examples are given to illustrate the practicality of the algorithms.

Quantized Hall conductance in a two-dimensional periodic potential

Abstract: The Hall conductance of a two-dimensional electron gas has been studied in a uniform magnetic field and a periodic substrate potential $U$. The Kubo formula is written in a form that makes apparent the quantization when the Fermi energy lies in a gap. Explicit expressions have been obtained for the Hall conductance for both large and small $\frac{U}{\ensuremath{\hbar}{\ensuremath{\omega}}_{c}}$.

Climate Forcing by Anthropogenic Aerosols

Abstract: Although long considered to be of marginal importance to global climate change, tropospheric aerosol contributes substantially to radiative forcing, and anthropogenic sulfate aerosol in particular has imposed a major perturbation to this forcing. Both the direct scattering of shortwavelength solar radiation and the modification of the shortwave reflective properties of clouds by sulfate aerosol particles increase planetary albedo, thereby exerting a cooling influence on the planet. Current climate forcing due to anthropogenic sulfate is estimated to be –1 to –2 watts per square meter, globally averaged. This perturbation is comparable in magnitude to current anthropogenic greenhouse gas forcing but opposite in sign. Thus, the aerosol forcing has likely offset global greenhouse warming to a substantial degree. However, differences in geographical and seasonal distributions of these forcings preclude any simple compensation. Aerosol effects must be taken into account in evaluating anthropogenic influences on past, current, and projected future climate and in formulating policy regarding controls on emission of greenhouse gases and sulfur dioxide. Resolution of such policy issues requires integrated research on the magnitude and geographical distribution of aerosol climate forcing and on the controlling chemical and physical processes.

Self-Efficacy: A Theoretical Analysis of Its Determinants and Malleability

Abstract: The construct of self-efficacy has received increasing empirical attention in the organizational behavior literature. People who think they can perform well on a task do better than those who think they will fail. Differences in self-efficacy are associated with bona fide differences in skill level; however, efficacy perceptions also may be influenced by differences in personality, motivation, and the task itself. This article reviews theoretically the antecedent processes and information cues involved in the formation of self-efficacy. A model of the determinants of self-efficacy is proposed that enhances understanding of both the complexity and malleability of the construct. Determinants that facilitate the most immediate change in self-efficacy are identified, and appropriate change strategies are highlighted. Implications and propositions pertaining to future research are discussed at the end of the article.

Surface reconstruction from unorganized points

Abstract: This thesis describes a general method for automatic reconstruction of accurate, concise, piecewise smooth surfaces from unorganized 3D points. Instances of surface reconstruction arise in numerous scientific and engineering applications, including reverse-engineering--the automatic generation of CAD models from physical objects. Previous surface reconstruction methods have typically required additional knowledge, such as structure in the data, known surface genus, or orientation information. In contrast, the method outlined in this thesis requires only the 3D coordinates of the data points. From the data, the method is able to automatically infer the topological type of the surface, its geometry, and the presence and location of features such as boundaries, creases, and corners. The reconstruction method has three major phases: (1) initial surface estimation, (2) mesh optimization, and (3) piecewise smooth surface optimization. A key ingredient in phase 3, and another principal contribution of this thesis, is the introduction of a new class of piecewise smooth representations based on subdivision. The effectiveness of the three-phase reconstruction method is demonstrated on a number of examples using both simulated and real data. Phases 2 and 3 of the surface reconstruction method can also be used to approximate existing surface models. By casting surface approximation as a global optimization problem with an energy function that directly measures deviation of the approximation from the original surface, models are obtained that exhibit excellent accuracy to conciseness trade-offs. Examples of piecewise linear and piecewise smooth approximations are generated for various surfaces, including meshes, NURBS surfaces, CSG models, and implicit surfaces.

Grading the severity of chronic pain.

Abstract: This research develops and evaluates a simple method of grading the severity of chronic pain for use in general population surveys and studies of primary care pain patients Measures of pain intensity, disability, persistence and recency of onset were tested for their ability to grade chronic pain severity in a longitudinal study of primary care back pain (n = 1213), headache (n = 779) and temporomandibular disorder pain (n = 397) patients A Guttman scale analysis showed that pain intensity and disability measures formed a reliable hierarchical scale Pain intensity measures appeared to scale the lower range of global severity while disability measures appeared to scale the upper range of global severity Recency of onset and days in pain in the prior 6 months did not scale with pain intensity or disability Using simple scoring rules, pain severity was graded into 4 hierarchical classes: Grade I, low disability--low intensity; Grade II, low disability--high intensity; Grade III, high disability--moderately limiting; and Grade IV, high disability--severely limiting For each pain site, Chronic Pain Grade measured at baseline showed a highly statistically significant and monotonically increasing relationship with unemployment rate, pain-related functional limitations, depression, fair to poor self-rated health, frequent use of opioid analgesics, and frequent pain-related doctor visits both at baseline and at 1-year follow-up Days in Pain was related to these variables, but not as strongly as Chronic Pain Grade Recent onset cases (first onset within the prior 3 months) did not show differences in psychological and behavioral dysfunction when compared to persons with less recent onset Using longitudinal data from a population-based study (n = 803), Chronic Pain Grade at baseline predicted the presence of pain in the prior 2 weeks Chronic Pain Grade and pain-related functional limitations at 3-year follow-up Grading chronic pain as a function of pain intensity and pain-related disability may be useful when a brief ordinal measure of global pain severity is required Pain persistence, measured by days in pain in a fixed time period, provides useful additional information

Stakeholder‐agency theory

Abstract: Taking agency theory and stakeholder theory as points of departure, this article proposes a paradigm that helps explain the following: (1) certain aspects of a firm's strategic behaviour; (2) the structure of management-stakeholder contracts; (3) the form taken by the institutional structures that monitor and enforce contracts between managers and other stakeholders; and (4) the evolutionary process that shapes both management-stakeholder contracts and the institutional structures that police those contracts.

Guidelines for the diagnosis and management of asthma.

Abstract: Guidelines for the Diagnosis and Management of Asthma were produced by the Expert Panel on the Management of Asthma convened by the National Asthma Education Program under the auspices of the National Heart, Lung, and Blood Institute of the National Institutes of Health. The full report (PHS publication no. 91-3042) and executive summary (pHS publication no. 91-3042A) were released in August and June of 1991, respectively, and mailed directly to family physicians and other practitioners under sponsorship of several pharmaceutical firms whose products are often used in treatment of asthma. Additionally, special issues of the Journal of Allergy and Clinical Immunowgy and Pediatric Allergy reprinted the entire report for their subscribers. In the Foreword to the report, Claude Lenfant, M.D., Director of the National Heart, Lung, and Blood Institute, presents the charge of the panel: \"To develop guidelines to improve the detection and treatment of asthma. \" He goes on to state that the guidelines \" ... are likely to have a profound effect on the way asthma is treated.\" Dr. Albert Sheffer, chair of the expert panel, states in the Preface his hope that with use of these guidelines, \"Patients with asthma can expect to control their symptoms, prevent most acute asthma exacerbations, maintain the activity levels they desire, and attain near normal lung function.\" Clinicians caring for patients with asthma are the intended audience for the guidelines. Dr. Lenfant comments in the Foreword that the report is designed to provide clinicians with new insights into asthma management, but whether

Linguistic experience alters phonetic perception in infants by 6 months of age

Abstract: Linguistic experience affects phonetic perception. However, the critical period during which experience affects perception and the mechanism responsible for these effects are unknown. This study of 6-month-old infants from two countries, the United States and Sweden, shows that exposure to a specific language in the first half year of life alters infants' phonetic perception.

A case-control study of screening sigmoidoscopy and mortality from colorectal cancer.

Abstract: Background The efficacy of sigmoidoscopic screening in reducing mortality from colorectal cancer remains uncertain. A randomized trial would be ideal for clarifying this issue but is very difficult to conduct. Case–control studies provide an alternative method of estimating the efficacy of screening sigmoidoscopy. Methods Using data on the 261 members of the Kaiser Permanente Medical Care Program who died of cancer of the rectum or distal colon from 1971 to 1988, we examined the use of screening by rigid sigmoidoscopy during the 10 years before the diagnosis and compared it with the use of screening in 868 control subjects matched with the case subjects for age and sex. Results Only 8.8 percent of the case subjects had undergone screening by sigmoidoscopy, as compared with 24.2 percent of the controls (matched odds ratio, 0.30; 95 percent confidence interval, 0.19 to 0.48). Adjustment for potential confounding factors increased the odds ratio to 0.41 (95 percent confidence interval, 0.25 to 0.69)...

CD28-mediated signalling co-stimulates murine T cells and prevents induction of anergy in T-cell clones.

Abstract: Occupancy of the T-cell antigen receptor is insufficient to induce T-cell activation optimally; a second co-stimulatory signal is required. Exposure of T-cell clones to complexes of antigen with major histocompatibility complex molecules in the absence of the co-stimulatory signal induces a state of clonal anergy. This requirement for two stimuli for T-cell activation could have an important role in vivo in establishing peripheral tolerance to antigens not encountered in the thymus. The receptor on T cells required for the co-stimulatory stimulus involved in the prevention of anergy has not been identified. The human T-cell antigen CD28 provides a signal that can synergize with T-cell antigen receptor stimulation in activating T cells to proliferate and secrete lymphokines. Here we report that a monoclonal antibody against the murine homologue of CD28 (ref. 7; J.A.G. et al., manuscript in preparation) can provide a co-stimulatory signal to naive CD4+ T cells and to T-cell clones. Moreover, we demonstrate that this co-stimulatory signal can block the induction of anergy in T-cell clones.

Game theory for applied economists

Abstract: This book introduces one of the most powerful tools of modern economics to a wide audience: those who will later construct or consume game-theoretic models. Robert Gibbons addresses scholars in applied fields within economics who want a serious and thorough discussion of game theory but who may have found other works overly abstract. Gibbons emphasizes the economic applications of the theory at least as much as the pure theory itself; formal arguments about abstract games play a minor role. The applications illustrate the process of model building--of translating an informal description of a multi-person decision situation into a formal game-theoretic problem to be analyzed. Also, the variety of applications shows that similar issues arise in different areas of economics, and that the same game-theoretic tools can be applied in each setting. In order to emphasize the broad potential scope of the theory, conventional applications from industrial organization have been largely replaced by applications from labor, macro, and other applied fields in economics. The book covers four classes of games, and four corresponding notions of equilibrium: static games of complete information and Nash equilibrium, dynamic games of complete information and subgame-perfect Nash equilibrium, static games of incomplete information and Bayesian Nash equilibrium, and dynamic games of incomplete information and perfect Bayesian equilibrium.

An Intercomparison of Methods for Finding Coupled Patterns in Climate Data

Abstract: This paper introduces a conceptual framework for comparing methods that isolate important coupled modes of variability between time series of two fields. Four specific methods are compared: principal component analysis with the fields combined (CPCA), canonical correlation analysis (CCA) and a variant of CCA proposed by Barnett and Preisendorfer (BP), principal component analysis of one single field followed by correlation of its component amplitudes with the second field (SFPCA), and singular value decomposition of the covariance matrix between the two fields (SVD). SVD and CPCA are easier to implement than BP, and do not involve user-chosen parameters. All methods are applied to a simple but geophysically relevant model system and their ability to detect a coupled signal is compared as parameters such as the number of points in each field, the number of samples in the time domain, and the signal-to-noise ratio are varied. In datasets involving geophysical fields, the number of sampling times ma...

Restoration of viral immunity in immunodeficient humans by the adoptive transfer of T cell clones.

Abstract: The adoptive transfer of antigen-specific T cells to establish immunity is an effective therapy for viral infections and tumors in animal models. The application of this approach to human disease would require the isolation and in vitro expansion of human antigen-specific T cells and evidence that such T cells persist and function in vivo after transfer. Cytomegalovirus-specific CD8+ cytotoxic T cell (CTL) clones could be isolated from bone marrow donors, propagated in vitro, and adoptively transferred to immunodeficient bone marrow transplant recipients. No toxicity developed and the clones provided persistent reconstitution of CD8+ cytomegalovirus-specific CTL responses.

Molecular and biological characterization of a murine ligand for CD40

Abstract: THE CD40 surface molecule is a 277-amino-acid glycoprotein expressed on B lymphocytes, epithelial cells and some carcinoma cell lines. Monoclonal antibodies against CD40 mediate a variety of effects on B lymphocytes, including induction of intercellular adhesion1,2, short- and long-term proliferation3–5, differentiation6,7 and enhanced tyrosine phosphorylation of proteins8. In addition, germinal centre centrocytes are prevented from undergoing apop-tosis by activation through CD40 and receptor for antigen9. These data indicate that CD40 could be a receptor for an unknown ligand with important functions in B-cell development and activation. This hypothesis is strengthened by the homology of the extracellular region of the CD40 molecule10with a family of cell-surface glycoproteins11,12that includes the receptors for nerve growth factor13,14 and tumour necrosis factor11,15,16. Here we report the cloning of a ligand for CD40 that is expressed on the cell surface of activated T cells and mediates B-cell proliferation in the absence of co-stimulus, as well as IgE production in the presence of interIeukin-4.

A Controlled Trial of Fluconazole to Prevent Fungal Infections in Patients Undergoing Bone Marrow Transplantation

Abstract: Background and Methods. Superficial and systemic fungal infections are a major problem among severely immunocompromised patients who undergo bone marrow transplantation. We performed a doubleblind, randomized, multicenter trial in which patients receiving bone marrow transplants were randomly assigned to receive placebo or fluconazole (400 mg daily). Fluconazole or placebo was administered prophylactically from the start of the conditioning regimen until the neutrophil count returned to 1000 per microliter, toxicity was suspected, or a systemic fungal infection was suspected or proved. Results. By the end of the treatment period, 67.2 percent of the 177 patients assigned to placebo had a positive fungal culture of specimens from any site, as compared with 29.6 percent of the 179 patients assigned to fluconazole. Among these, superficial infections were diagnosed in 33.3 percent of the patients receiving placebo and in 8.4 percent of the patients receiving fluconazole (P<0.001). Systemic fungal in...

High-order multiple-scattering calculations of x-ray-absorption fine structure.

Abstract: High-order scattering is found to be essential for the convergence of the multiple-scattering (MS) theory of x-ray-absorption fine structure, both in the near-edge and the extended regimes. These contributions are calculated using an ab initio curved-wave scattering-matrix formalism. Convergence to full MS accuracy is demonstrated for fcc Cu, as well as for molecular ${\mathrm{O}}_{2}$ and ${\mathrm{N}}_{2}$, where our approach provides a high-order MS interpretation of the ${\mathrm{\ensuremath{\sigma}}}^{\mathrm{*}}$ shape resonances.

Coherent 25- to 35-Hz oscillations in the sensorimotor cortex of awake behaving monkeys.

Abstract: Synchronous 25- to 35-Hz oscillations were observed in local field potentials and unit activity in sensorimotor cortex of awake rhesus monkeys. The oscillatory episodes occurred often when the monkeys retrieved raisins from a Kluver board or from unseen locations using somatosensory feedback; they occurred less often during performance of repetitive wrist flexion and extension movements. The amplitude, duration, and frequency of oscillations were not directly related to movement parameters in behaviors studied so far. The occurrence of the oscillations was not consistently related to bursts of activity in forearm muscles, but cycle-triggered averages of electromyograms revealed synchronous modulation in flexor and extensor muscles. The phase of the oscillations changed continuously from the surface to the deeper layers of the cortex, reversing their polarity completely at depths exceeding 800 microns. The oscillations could become synchronized over a distance of 14 mm mediolaterally in precentral cortex. Coherent oscillations could also occur at pre- and postcentral sites separated by an estimated tangential intracortical distance of 20 mm. Activity of single units was commonly seen to burst in synchrony with field potential oscillations. These findings suggest that such oscillations may facilitate interactions between cells during exploratory and manipulative movements, requiring attention to sensorimotor integration.

Genetic linkage evidence for a familial Alzheimer's disease locus on chromosome 14.

Abstract: Linkage analysis was used to search the genome for chromosomal regions harboring familial Alzheimer's disease genes. Markers on chromosome 14 gave highly significant positive lod scores in early-onset non-Volga German kindreds; a Zmax of 9.15 (theta = 0.01) was obtained with the marker D14S43 at 14q24.3. One early-onset family yielded a lod score of 4.89 (theta = 0.0). When no assumptions were made about age-dependent penetrance, significant results were still obtained (Zmax = 5.94, theta = 0.0), despite the loss of power to detect linkage under these conditions. Results for the Volga German families were either negative or nonsignificant for markers in this region. Thus, evidence indicates a familial Alzheimer's disease locus on chromosome 14.

Bulk chemical characteristics of dissolved organic matter in the ocean

Abstract: Dissolved organic matter (DOM) is the largest reservoir of reduced carbon in the oceans. The nature of DOM is poorly understood, in part, because it has been difficult to isolate sufficient amounts of representative material for analysis. Tangential-flow ultrafiltration was shown to recover milligram amounts of >1000 daltons of DOM from seawater collected at three depths in the North Pacific Ocean. These isolates represented 22 to 33 percent of the total DOM and included essentially all colloidal material. The elemental, carbohydrate, and carbon-type (by 13C nuclear magnetic resonance) compositions of the isolates indicated that the relative abundance of polysaccharides was high (∼50 percent) in surface water and decreased to ∼25 percent in deeper samples. Polysaccharides thus appear to be more abundant and reactive components of seawater DOM than has been recognized.

What can the history and physical examination tell us about low back pain

Abstract: BACK pain ranks second only to upper respiratory illness as a symptomatic reason for office visits to physicians.1About 70% of adults have low back pain at some time, but only 14% have an episode that lasts more than 2 weeks. About 1.5% have such episodes with features of sciatica.2,3Most causes of back pain respond to symptomatic and physical measures, but some are surgically remediable and some are systemic diseases (cancer or disseminated infection) requiring specific therapy, so careful diagnostic evaluation is important. Features of the clinical history and physical examination influence not only therapeutic choices but also decisions about diagnostic imaging, laboratory testing, and specialist referral. ANATOMIC/PHYSIOLOGIC ORIGINS OF FINDINGS IN THE LOW BACK Low back pain may arise from several structures in the lumbar spine, including the ligaments that interconnect vertebrae, outer fibers of the annulus fibrosus, facet joints, vertebral periosteum, paravertebral musculature and fascia,

A cohort study of the risk of cervical intraepithelial neoplasia grade 2 or 3 in relation to papillomavirus infection.

Abstract: Background. Human papillomavirus (HPV) has been associated with cervical intraepithelial neoplasia, but the temporal relation between the infection and the neoplasia remains unclear, as does the relative importance of the specific type of HPV, other sexually transmitted diseases, and other risk factors. Methods. We studied prospectively a cohort of 241 women who presented for evaluation of sexually transmitted disease and had negative cervical cytologic tests. The women were followed every four months with cytologic and colposcopic examinations of the uterine cervix and tests for HPV DNA and other sexually transmitted diseases. Results. Cervical intraepithelial neoplasia grade 2 or 3 was confirmed by biopsy in 28 women. On the basis of survival analysis, the cumulative incidence of cervical intraepithelial neoplasia at two years was 28 percent among women with a positive test for HPV and 3 percent among those without detectable HPV DNA. The risk was highest among those with HPV type 16 or 18 infe...

Constrained Monte Carlo Maximum Likelihood for Dependent Data

Abstract: Maximum likelihood estimates (MLEs) in autologistic models and other exponential family models for dependent data can be calculated with Markov chain Monte Carlo methods (the Metropolis algorithm or the Gibbs sampler), which simulate ergodic Markov chains having equilibrium distributions in the model. From one realization of such a Markov chain, a Monte Carlo approximant to the whole likelihood function can be constructed. The parameter value (if any) maximizing this function approximates the MLE