Showing papers by "University of Rochester published in 1994"

Proportional hazards tests and diagnostics based on weighted residuals

Abstract: SUMMARY Nonproportional hazards can often be expressed by extending the Cox model to include time varying coefficients; e.g., for a single covariate, the hazard function for subject i is modelled as exp { fl(t)Zi(t)}. A common example is a treatment effect that decreases with time. We show that the function /3(t) can be directly visualized by smoothing an appropriate residual plot. Also, many tests of proportional hazards, including those of Cox (1972), Gill & Schumacher (1987), Harrell (1986), Lin (1991), Moreau, O'Quigley & Mesbah (1985), Nagelkerke, Oosting & Hart (1984), O'Quigley & Pessione (1989), Schoenfeld (1980) and Wei (1984) are related to time-weighted score tests of the proportional hazards hypothesis, and can be visualized as a weighted least-squares line fitted to the residual plot.

Hierarchical mixtures of experts and the EM algorithm

Abstract: We present a tree-structured architecture for supervised learning. The statistical model underlying the architecture is a hierarchical mixture model in which both the mixture coefficients and the mixture components are generalized linear models (GLIM's). Learning is treated as a maximum likelihood problem; in particular, we present an Expectation-Maximization (EM) algorithm for adjusting the parameters of the architecture. We also develop an on-line learning algorithm in which the parameters are updated incrementally. Comparative simulation results are presented in the robot dynamics domain.

Facilitating internalization: the self-determination theory perspective.

Abstract: Self-determination theory (Deci & Ryan, 1985) posits that (a) people are inherently motivated to internalize the regulation of uninteresting though important activities; (b) there are two different processes through which such internalization can occur, resulting in qualitatively different styles of self-regulation; and (c) the social context influences which internalization process and regulatory style occur. The two types of internalization are introjection, which entails taking in a value or regulatory process but not accepting it as one's own, and integration, through which the regulation is assimilated with one's core sense of self. Introjection results in internally controlling regulation, whereas integration results in self-determination. An experiment supported our hypothesis that three facilitating contextual factors--namely, providing a meaningful rationale, acknowledging the behaver's feelings, and conveying choice--promote internalization, as evidenced by the subsequent self-regulation of behavior. This experiment also supported our expectation that when the social context supports self-determination, integration tends to occur, whereas when the context does not support self-determination, introjection tends to occur.

Pain and its treatment in outpatients with metastatic cancer.

Abstract: Background and Methods Pain is often inadequately treated in patients with cancer. A total of 1308 outpatients with metastatic cancer from 54 treatment locations affiliated with the Eastern Cooperative Oncology Group rated the severity of their pain during the preceding week, as well as the degree of pain-related functional impairment and the degree of relief provided by analgesic drugs. Their physicians attributed the pain to various factors, described its treatment, and estimated the impact of pain on the patients' ability to function. We assessed the adequacy of prescribed analgesic drugs using guidelines developed by the World Health Organization, studied the factors that influenced whether analgesia was adequate, and determined the effects of inadequate analgesia on the patients' perception of pain relief and functional status. Results Sixty-seven percent of the patients (871 of 1308) reported that they had had pain or had taken analgesic drugs daily during the week preceding the study, and 36 percen...

Excimers and Exciplexes of Conjugated Polymers

Abstract: Observations of intermolecular excimers in several pi-conjugated polymers and exciplexes of these polymers with tris(p-tolyl) amine are reported. It is shown that the luminescence of conjugated polymer thin films originates from excimer emission and that the generally low quantum yield is the result of self-quenching. Thus, in sufficiently dilute solution, the "single-chain" emission has a quantum yield of unity. Exciplex luminescence and exciplex-mediated charge photogeneration have much higher quantum yields than the excimer-mediated photophysical processes. These results provide a basis for understanding and controlling the photophysics of conjugated polymers in terms of supramolecular structure and morphology.

On the motivational nature of cognitive dissonance: Dissonance as psychological discomfort.

Abstract: Most empirical research investigating the motivational properties of cognitive dissonance has focused on the arousal component of dissonance rather than on the psychological component explicitly delineated by L. Festinger (1957) . In 2 induced-compliance experiments, a self-report measure of affect was used to demostrate that dissonance is experienced as psychological discomfort and that this psychological discomfort is alleviated on implementation of a dissonance-reduction strategy, attitude change. Experiment 1 yielded supporting evidence for both of these propositions. Experiment 2 replicated the 1st experiment and ruled out a self-perception-based alternative explanation for the dissonance-reduction findings in Experiment 1. Results from the 2 experiments strongly support Festinger's conceptualization of cognitive dissonance as a fundamentally motivational state.

Structure of the autoinducer required for expression of Pseudomonas aeruginosa virulence genes

Abstract: In Pseudomonas aeruginosa the LasR protein is required for activation of lasB and several other virulence genes. A diffusible signal molecule, the P. aeruginosa autoinducer (PAI), produced by the bacterial cell and released into the growth medium, is required for activity of LasR. By cloning a lasB::lacZ fusion and a lasR gene under control of the lac promoter in Escherichia coli, we have developed a quantitative bioassay for PAI. We have used this assay to follow the purification of PAI from cell-free culture supernatant fluids in which P. aeruginosa or E. coli containing the P. aeruginosa gene required for autoinducer synthesis, lasI, had been grown. Chemical analyses indicated the purified material was 3-oxo-N-(tetrahydro-2-oxo-3-furanyl)dodecanamide. To confirm this assignment, the compound was synthesized and the synthetic compound was shown to have chemical and biological properties identical to those of PAI purified from culture supernatant fluids. The elucidation of the PAI structure suggests therapeutic approaches toward control of P. aeruginosa infections.

Representations of Relationships to Teachers, Parents, and Friends as Predictors of Academic Motivation and Self-Esteem:

Abstract: In this study early adolescents' (N = 606) representations of relationships to teachers, parents, andfriends are examined in relation to each other and to various measures of school adjustment, motivation and self-esteem. The relationship dimensions tapped included felt security, emotional and school utilization, and emulation with respect to each targetfigure. It was hypothesized that parent representations would predict those of both teachers and friends, whereas friend and teacher variables would not be significantly associated. It was predicted also that more positive representations of relationships to parents and teachers would each uniquely predict school functioning indices, whereas representations offriends would be largely unrelated to school-related outcomes. Representations of teachers, parents andfriends all were expected to correlate with self-esteem relevant outcomes. These hypotheses were generally confirmed. The findings are discussed in terms of the significance of relatednessformotivati...

Correlation between particle size, in vivo particle persistence, and lung injury

Abstract: Dosimetry parameters such as deposition, clearance, retention, and translocation and dissolution of inhaled particles in and to different lung compartments may be important for the persistence of particles in the lung and may correlate with adverse pulmonary effects. We investigated such correlations using a model involving TiO2 particles of two particle sizes (20 nm diameter, ultrafine; 250 nm diameter, fine) of the same crystalline structure (anatase). A 12-week inhalation experiment in rats resulted in a similar mass deposition of the two particle types in the lower respiratory tract. The ultrafine particles elicited a persistently high inflammatory reaction in the lungs of the animals compared to the larger-sized particles. In the postexposure period (up to 1 year) retention in the alveolar space per se was not different between fine and ultrafine TiO2. However, the following differences between the particle types were noted: a significantly different total pulmonary retention, both quantitatively (significantly prolonged retention of the ultrafine TiO2) and qualitatively (increased translocation to the pulmonary interstitium and persistence there of the ultrafine TiO2); greater epithelial effects (Type II cell proliferation; occlusion of pores of Kohn) and the beginning of interstitial fibrotic foci with ultrafine TiO2; significant sustained impairment of alveolar macrophage function after ultrafine TiO2 exposure as measured by the clearance of test particles. A correlation between particle surface area and effects was observed. A comparison of the adverse reactions with dosimetric parameters of TiO2 in different lung compartments in the postexposure period showed a correlation of the persistence of effects in both the alveolar and interstitial space with the persistence of particles in the respective compartment.

Skeletal Effects of Estrogen

Abstract: BONE differs from reproductive tissues in that many aspects of skeletal growth, turnover, and function occur in the absence of gonadal hormones. Nevertheless, sex steroids have an important impact on bone physiology: they participate in the sexual dimorphism of the skeleton, play a role in maintenance of mineral homeostasis during reproduction, and are essential to maintaining bone balance in adults. Insufficient levels of certain sex steroids predispose the human skeleton to bone loss and to osteoporotic fractures. Estrogen appears to be the most important sex steroid in preventing osteoporosis in women and is the subject of this review. Serious difficulties must be overcome to understand the action of estrogen on mineralized tissues. The skeleton is heterogeneous and contains many cell types. The cells that synthesize (osteoblasts), lie within (osteocytes), and degrade (osteoclasts) bone matrix are present in small numbers, are difficult to isolate as pure populations, and probably do not proliferate.

The Doctor-Patient Relationship and Malpractice: Lessons From Plaintiff Depositions

Abstract: Background: The current literature does not provide an answer to the question, "What prompts patients to sue doctors or hospitals?" Not all adverse outcomes result in suits, and threatened suits do not always involve adverse outcomes. The exploration of other factors has been hampered by the lack of a methodology to contact plaintiffs and elicit their views about their experience in delivered health care. This study employed the transcripts of discovery depositions of plaintiffs as a source of insight into the issues that prompted individuals to file a malpractice claim. Methods: This study is a descriptive series review of a convenience sample of 45 plaintiffs' depositions selected randomly from 67 depositions made available from settled malpractice suits filed between 1985 and 1987 against a large metropolitan medical center. Information extracted from each deposition included the alleged injury; the presence of the question, "Why are you suing?" and, if present, the answer; the presence of problematic relationship issues between providers and patients and/or families and, if present, the discourse supporting it; the presence of the question, "Did a health professional suggest maloccurrence?" and, if yes, who. Using a process of consensual validation, relationship issues were organized into groups of more generalized categories suggested by the data. Answers to the questions, "Why are you suing?" and "Who suggested maloccurrence?" are described. Results: Problematic relationship issues were identified in 71% of the depositions with an interrater reliability of 93.3%. Four themes emerged from the descriptive review of the 3787 pages of transcript: deserting the patient (32%), devaluing patient and/or family views (29%), delivering information poorly (26%), and failing to understand the patient and/or family perspective (13%). Thirty-one plaintiffs were asked if health professionals suggested maloccurrence. Fifty-four percent (n=17) responded affirmatively. The postoutcome-consulting specialist was named in 71% (n=12) of the depositions in which maloccurrence was allegedly suggested. Conclusions: In our sample, the decision to litigate was often associated with a perceived lack of caring and/or collaboration in the delivery of health care. The issues identified included perceived unavailability, discounting patient and/or family concerns, poor delivery of information, and lack of understanding the patient and/or family perspective. Particular attention should be paid to the postadverse-event consultant-patient interaction. (Arch Intern Med. 1994;154:1365-1370)

Mitochondrial calcium transport: physiological and pathological relevance

Abstract: Since the initiation of work on mitochondrial Ca2+ transport in the early 1960s, the relationship between experimental observations and physiological function has often seemed enigmatic. Why, for example, should an organelle dedicated to the crucial task of producing approximately 95% of the cell's ATP sequester Ca2+, sometimes in preference to phosphorylating ADP? Why should there be two separate efflux mechanisms, the Na+ independent and the Na+ dependent, both thought until recently to be driven exclusively either directly or indirectly by the energy of the pH gradient? Does intramitochondrial free Ca2+ concentration control metabolism? Is there evidence for any separate function of the mitochondrial Ca2+ transport mechanisms under pathological conditions? What is the relationship between mitochondrial Ca2+ transport, the mitochondrial membrane permeability transition, and irreversible cell damage under pathological conditions? First, we review what is known about control of metabolism, evidence for a role for intramitochondrial Ca2+ in control of metabolism, the cellular conditions under which mitochondria are exposed to Ca2+, characteristics of the mitochondrial Ca2+ transport mechanisms including the permeability transition, and evidence for and against mitochondrial Ca2+ uptake in vivo. Then the questions listed above and others are addressed from the perspective of the characteristics of the mechanisms of mitochondrial Ca2+ transport.

Asymptotic Theory for the Garch(1,1) Quasi-Maximum Likelihood Estimator

Abstract: This paper investigates the sampling behavior of the quasi-maximum likelihood estimator of the Gaussian GARCH(1, 1) model. The rescaled variable (the ratio of the disturbance to the conditional standard deviation) is not required to be Gaussian nor independent over time, in contrast to the current literature. The GARCH process may be integrated (a + a = 1), or even mildly explosive (a + f > 1). A bounded conditional fourth moment of the rescaled variable is sufficient for the results. Consistent estimation and asymptotic normality are demonstrated, as well as consistent estimation of the asymptotic covariance matrix.

Human Herpesvirus-6 Infection in Children -- A Prospective Study of Complications and Reactivation

Abstract: Background Infection with human herpesvirus-6 (HHV-6) is nearly universal in infancy or early childhood. However, the course of this infection, its complications, and its potential for persistence or reactivation remain unclear. Methods We studied infants and children under the age of three years who presented to our emergency department with acute illnesses. Infants and young children without acute illness were studied as controls. HHV-6 infection was identified by blood-mononuclear-cell culture, serologic testing, and the polymerase chain reaction (PCR). Results No primary HHV-6 infection was found among 582 infants and young children with acute nonfebrile illnesses or among 352 controls without acute illness. Of 1653 infants and young children with acute febrile illnesses, 160 (9.7 percent) had primary HHV-6 infection, as documented by viremia and seroconversion. They ranged in age from 2 weeks to 25 months; 23 percent were under the age of 6 months. HHV-6 infections accounted for 20 percent of 365 vis...

Time Is of the Essence: A Conjecture that Hemispheric Specialization Arises from Interhemispheric Conduction Delay

Abstract: Tomasch (1954) and Aboitiz et al. (1992) found the majority of the fibers of the human corpus callosum are under 1 micron in diameter. Electron microscopic studies of Swadlow et al. (1980) and the detailed study of LaMantia and Rakic (1990a) on macaques show the average size of the myelinated callosal axons also to be less than 1 micron. In man, the average-sized myelinated fiber interconnecting the temporal lobes would have a one-way, interhemispheric delay of over 25 msec. Thus, finely detailed, time-critical neuronal computations (i.e., tasks that strain the capacity of the callosum and hence could not be handled by just the larger fibers) would be performed more quickly via shorter and faster intrahemispheric circuits. While one transit across the commissural system might yield tolerable delays, multiple passes as in a system involving "setting" would seem prohibitively slow. We suggest that these temporal limits will be avoided if the neural apparatus necessary to perform each high-resolution, time-critical task is gathered in one hemisphere. If the, presumably overlapping, neural assemblies needed to handle overlapping tasks are clustered together, this would lead to hemispheric specialization. The prediction follows that the large brains of mammals such as elephants and cetaceans will also manifest a high degree of hemispheric specialization.

The nature of man

Abstract: Understanding human behavior is fundamental to understanding how organizations function, whether they are profit-making firms, non-profit enterprises, or government agencies. Much disagreement among managers, scientists, policy makers, and citizens arises from substantial differences in the way we think about human nature—about their strengths, frailties, intelligence, ignorance, honesty, selfishness, and generosity. In this paper we discuss five alternative models of human behavior that are commonly used (though usually implicitly). They are the Resourceful, Evaluative, Maximizing Model (REMM), Economic (or Money Maximizing) Model, Psychological (or Hierarchy of Needs) Model, Sociological (or Social Victim) Model, and the Political (or Perfect Agent) Model. We argue that REMM best describes the systematically rational part of human behavior. It serves as the foundation for the agency model of financial, organizational, and governance structure of firms. The growing body of social science research on human behavior has a common message: Whether they are politicians, managers, academics, professionals, philanthropists, or factory workers, individuals are resourceful, evaluative maximizers. They respond creatively to the opportunities the environment presents, and they work to loosen constraints that prevent them from doing what they wish. They care about not only money, but about almost everything—respect, honor, power, love, and the welfare of others. The challenge for our society, and for all organizations in it, is to establish rules of the game that tap and direct human energy in ways that increase rather than reduce the effective use of our scarce resources.

Comfort care for terminally ill patients. The appropriate use of nutrition and hydration

Abstract: Objective. —To determine the frequency of symptoms of hunger and thirst in a group of terminally ill patients and determine whether these symptoms could be palliated without forced feeding, forced hydration, or parenteral alimentation. Design. —Prospective evaluation of consecutively admitted terminally ill patients treated in a comfort care unit. Setting. —Ten-bed comfort care unit in a 471-bed long-term care facility. Participants.—Mentally aware, competent patients with terminal illnesses monitored from time of admission to time of death while residing in the comfort care unit. Main Outcome Measures. —Symptoms of hunger, thirst, and dry mouth were recorded, and the amounts and types of food and fluids necessary to relieve these symptoms were documented. The subjective level of comfort was assessed longitudinally in all patients. Results. —Of the 32 patients monitored during the 12 months of study, 20 patients (63%) never experienced any hunger, while 11 patients (34%) had symptoms only initially. Similarly, 20 patients (62%) experienced either no thirst or thirst only initially during their terminal illness. In all patients, symptoms of hunger, thirst, and dry mouth could be alleviated, usually with small amounts of food, fluids, and/or by the application of ice chips and lubrication to the lips. Comfort care included use of narcotics for relief of pain or shortness of breath in 94% of patients. Conclusions. —In this series, patients terminally ill with cancer generally did not experience hunger and those who did needed only small amounts of food for alleviation. Complaints of thirst and dry mouth were relieved with mouth care and sips of liquids far less than that needed to prevent dehydration. Food and fluid administration beyond the specific requests of patients may play a minimal role in providing comfort to terminally ill patients. (JAMA. 1994;272:1263-1266)

Coaxial Stacking of Helixes Enhances Binding of Oligoribonucleotides and Improves Predictions of RNA Folding

Abstract: An RNA model system consisting of an oligomer binding to a 4-nt overhang at the 59 end of a hairpin stem provides thermodynamic parameters for helix-helix interfaces. In a sequence-dependent manner, oligomers bind up to 1000-fold more tightly adjacent to the hairpin stem than predicted for binding to a free tetramer at 37 degrees C. For the interface (/) in [formula: see text] additional free energy change, delta delta G 37 degrees, for binding is roughly the nearest-neighbor delta G 37 degrees for propagation of an uninterrupted helix of equivalent sequence, CGGC. When X and Z are omitted, the delta delta 37 degrees is even more favorable by approximately 1 kcal/mol (1 cal = 4.184J). On average, predictions of 11 RNA secondary structures improve from 67 to 74% accuracy by inclusion of similar stacking contributions.

Congruence between Citizens and Policymakers in Two Visions of Liberal Democracy

Abstract: This paper explores two quite different visions of the democratic processes that can create congruence between citizen preferences and public policies. In the Majority Control vision, electoral competition and citizen choices result in the direct election of governments committed to policies corresponding to the preferences of the median voter. In the Proportionate Influence vision, election outcomes result in legislatures that reflect the preferences of all citizens; legislative bargaining results in policies linked to the position of the median voter. The authors give more explicit theoretical form to those visions and link them empirically to specific types of modern democracies. They then attempt to test the success of each vision in bringing about congruence between citizen self-placements and the estimated positions of governments and policymaker coalitions on the left-right scale in twelve nations in the late 1970s and early 1980s. Although the analysis reveals weaknesses in each approach, it suggests a consistent advantage for the Proportionate Influence vision.

The impact of subtype, frequency, chronicity, and severity of child maltreatment on social competence and behavior problems

Abstract: This investigation examined the impact of dimensions within maltreatment such as the severity, frequency, chronicity, and subtypes of maltreatment and their relationship with child outcome. Children between the ages of 5 and 11 who participated in a summer camp program were assessed on their social competence, behavior problems, and peers ratings of cooperation, disruption, and initiation of aggression. The 235 participants were all from low-socioeconomic status families; 145 children were from families with documented histories of child maltreatment, whereas 90 of the children had no record of maltreatment. The study found that severity of the maltreatment, the frequency of Child Protective Services reports, and the interaction between severity and frequency were significant predictors of children's functioning. Additionally, the chronicity of the maltreatment in the family significantly predicted peer ratings of aggression. Subtype differences emerged as well, with children in the sexual abuse group being more socially competent than other maltreated children, and children in the physical abuse group having more behavior problems than nonmaltreated children. Regression analyses with cooccurrence of multiple subtypes of maltreatment indicated that physical neglect, physical abuse, and sexual abuse made significant unique contributions in predicting child outcomes. The advantages of exploring multiple dimensions within maltreatment, the necessity of developing better operational definitions of these dimensions, and social policy implications of the findings are discussed.

Factor Endowments: Institutions, and Differential Paths of Growth Among New World Economies: A View from Economic Historians of the United States

Abstract: Many scholars are concerned with why the U.S. and Canada have been so much more successful over time than other New World economies. Since all New World societies enjoyed high levels of product per capita early in their histories, the divergence in paths can be traced back to the achievement of sustained economic growth by the U.S. and Canada during the 18th to early 19th centuries. This paper highlights the relevance of differences in the degree of inequality in wealth, human capital, and political power in accounting for the variation in the records of growth, and suggest that the roots of inequality lay in differences in the initial factor endowments of the respective colonies The large concentration of Native Americans, and the suitability of cultiva- ting sugar and other crops were key in generating extreme inequality. This encouraged the evolution of societies where small elites of European descent held highly disproportionate shares of the wealth, human capital and political power, and dominated the population economically and politically. Absent from the nearly all-inclusive list of New World colonies with these conditions were the British settlements in the northern part of the North American continent. Next, we discuss the tendencies of government policies to maintain these conditions along the respective economy's path of development. Finally, we explore the effects of inequality on the evolution of institutions conducive to participation in the commercial economy, markets and technological change during this specific era, and suggest that their greater equality in wealth, human capital, and political capital and power may have predisposed the U.S. and Canada toward earlier realization of sustained economic growth.

A new questionnaire for gastroesophageal reflux disease

Abstract: for outpatients, 0.70 [interquartile range, 0.59 to 0.81]; median Œ for population sample, 0.70 [interquartile range, 0.60 to 0.81]) and validity (median Œ, 0.62 [interquartile range, 0.49 to 0.74]) were acceptable. • Conclusion: Our initial results suggest that this questionnaire is valid and should be applicable in population-based studies to assess gastroesophageal reflux disease. (Mayo Clin Proc 1994; 69:539-547)

The enhancement of psychological wellness: challenges and opportunities

Abstract: Developed the concept of psychological wellness and made the case that proportionally more resources should be directed to the pursuit of this goal. Five pathways to wellness are considered, implicating aspects of individual development and the impact of contexts, settings, and policies. The five pathways are: forming wholesome early attachments; acquiring age- and ability-appropriate competencies; engineering settings that promote adaptive outcomes; fostering empowerment; and acquiring skills needed to cope effectively with life stressors. Although these noncompeting pathways have differential salience at different ages and for different groups and life conditions, each is an essential element in any comprehensive social plan to advance wellness. Examples of effective programs are cited in all five areas, including recent comprehensive, long-term programs embodying multiple pathways to wellness.

A plasma exchange versus immune globulin infusion trial in chronic inflammatory demyelinating polyradiculoneuropathy

Abstract: Chronic inflammatory demyelinating polyradiculoneuropathy is a paralytic syndrome, causing considerable disability and even death. In controlled clinical trials, plasma exchange prevented or ameliorated neurological deficits, but the efficacy of immune globulin infusion remains unproved. Also unknown is whether immune globulin infusion is as effective, or more effective, than plasma exchange and what dosages and frequencies are best. In this observer-blinded study, using some objective end points not subject to bias (e.g., summated compound muscle action potential), 20 patients with progressive or static polyneuropathy were randomly assigned to receive either of the two treatments for 6 weeks, followed by a washout period, and then were assigned to receive the other treatment. Plasma exchange (twice a week for 3 weeks then once a week for 3 weeks) and immune globulin infusion (0.4 gm/kg once a week for 3 weeks, then 0.2 gm/kg once a week for the next 3 weeks) were used. End points assessed before and after treatment schedules were neurological disability score; muscle weakness of the neurological disability score; summated compound muscle action potentials of ulnar, median, and peroneal nerves; summated sensory nerve action potentials of ulnar and sural nerves; and vibratory detection threshold of the great toe using CASE IV. Observers were masked as to treatment used. Of 20 patients, 13 received both treatments whereas 4 did not worsen sufficiently to receive the second treatment--1 patient left the study during and 2 after the first treatment to receive unscheduled treatment elsewhere.(ABSTRACT TRUNCATED AT 250 WORDS)