Showing papers by "University of North Carolina at Chapel Hill published in 1986"

Robust statistics: the approach based on influence functions

Abstract: 1. Introduction and Motivation. 2. One-Dimensional Estimators. 3. One-Dimensional Tests. 4. Multidimensional Estimators. 5. Estimation of Covariance Matrices and Multivariate Location. 6. Linear Models: Robust Estimation. 7. Linear Models: Robust Testing. 8. Complements and Outlook. References. Index.

The Role of Self-Efficacy in Achieving Health Behavior Change

Abstract: The concept of self-efficacy is receiving increasing recognition as a predictor of health behavior change and maintenance. The purpose of this article is to facilitate a clearer understanding of both the concept and its relevance for health education research and practice. Self-efficacy is first defined and distinguished from other related concepts. Next, studies of the self-efficacy concept as it relates to health practices are examined. This review focuses on cigarette smoking, weight control, contraception, alcohol abuse and exercise behaviors. The studies reviewed suggest strong relationships between self-efficacy and health behavior change and maintenance. Experimental manipulations of self-efficacy suggest that efficacy can be enhanced and that this enhancement is related to subsequent health behavior change. The findings from these studies also suggest methods for modifying health practices. These methods diverge from many of the current, traditional methods for changing health practices. Recommend...

Interaction of plasma membrane fibronectin receptor with talin—a transmembrane linkage

Abstract: Many observations suggest the presence of transmembrane linkages between the cytoskeleton and the extracellular matrix. In fibroblasts both light and electron microscopic observations reveal a co-alignment between actin filaments at the cell surface and extracellular fibronectin1–3. These associations are seen at sites of cell matrix interaction, frequently along stress fibres and sometimes where these bundles of microfilaments terminate at adhesion plaques (focal contacts). Non-morphological evidence also indicates a functional linkage between the cytoskeleton and extracellular matrix. Addition of fibronectin to transformed cells induces flattening of the cells and a reorganization of the actin cytoskeleton, with the concomitant appearance of arrays of stress fibres4–6. Conversely, disruption of the actin cytoskeleton by treatment with cytochalasin B leads to release of fibronectin from the cell surface7. As yet, there is no detailed knowledge of the molecules involved in this transmembrane linkage, although several proteins have been suggested as candidates in the chain of attachment between bundles of actin filaments and the cytoplasmic face of the plasma membrane: these include vinculin8, α-actinin9 and talin10, each one having been identified at regions where bundles of actin filaments interact with the plasma membrane and underlying cell-surface fibronectin10–13. Recently, the cell-substrate attachment (CSAT) antigen14 has been identified as a plasma membrane receptor for fibronectin15, raising the possibility that this glycoprotein complex may serve as a bridge between fibronectin and one or more of the underlying cytoskeletal components mentioned. Here we have investigated the interaction of the purified CSAT antigen with these cytoskeletal components, and we demonstrate an interaction specifically between the CSAT antigen and talin.

Central Projections of Identified, Unmyelinated (C) Afferent Fibers Innervating Mammalian Skin

Abstract: Unmyelinated (C) fibers are the most numerous sensory elements of mammalian peripheral nerve and comprise many of those responsible for initiating pain and temperature reactions; however, direct evidence has been lacking as to where and how these fibers terminate in the central nervous system. A plant lectin (Phaseolus vulgaris leukoagglutinin) was applied intracellularly by iontophoresis as an immunocytochemical marker. This permitted visualization of the central terminations of cutaneous C sensory fibers that had been identified by the nature of stimuli that excited them. The central branch of C-fiber units arborized and terminated mainly in the superficial layers of the spinal dorsal horn in defined patterns that related to their functional attributes. Thus, the superficial dorsal horn seems to act as a processing station for signals from fine sensory fibers.

Black-hole thermodynamics and the Euclidean Einstein action

Abstract: Using the approach to black-hole thermodynamics initiated by Gibbons and Hawking, in terms of the Euclidean Einstein action, I show that the canonical ensemble with elements of radius r and temperature T(r) for hot gravity with black holes is well defined. This follows from the double valuedness of solutions of the Euclidean Einstein equation with canonical boundary conditions. One of the solutions is a locally stable hole. Its partition function is well defined and implies the entropy S=4\ensuremath{\pi}${M}^{2}$ as well as a generalized version of black-hole thermodynamics that reduces to the usual form if ${\mathrm{rM}}^{\mathrm{\ensuremath{-}}1}$\ensuremath{\rightarrow}\ensuremath{\infty}. The density of states of the locally stable hole is real and nonpathological. The free energy of this hole can be negative, while that of the other (unstable) solution is always positive. Consequently, the direct nucleation of black holes from hot flat space, as proposed by Gross, Perry, and Yaffe, can be given a thermodynamically consistent description. The scaling laws for hot gravity are obtained and applied to phase transitions between hot flat space and locally stable holes. The free energy of the unstable solution forms the effective potential barrier between these phases. The ground state of the canonical ensemble is always locally stable in the semiclassical approximation. If N is the effective number of massless fields of helicity zero in hot flat space, then when either r\ensuremath{\lesssim}${N}^{1/2}$ or T\ensuremath{\gtrsim}${N}^{\mathrm{\ensuremath{-}}1/2}$, hot flat space is the most probable ground state. Independently of N, if rT${l(27)}^{1/2}$(8\ensuremath{\pi}${)}^{\mathrm{\ensuremath{-}}1}$ there can be no real black hole in the canonical ensemble.

Social ties and mortality in evans county, georgia

Abstract: In an attempt to replicate Berkman and Syme's study of social networks and mortality in Alameda County, California, the authors investigated the relationship between a social network index and survivorship from 1967 to 1980 in the Evans County, Georgia, cohort. They constructed an index modeled after the Berkman Social Network Index and tested it in race- and sex-specific proportional hazards models for 2,059 subjects who were examined in 1967-1969 during the Evans County Cardiovascular Epidemiologic Study. The present study emphasized a priori specification of the social network index and statistical hypothesis test. Descriptive analyses were consistent with a modest social networks effect (e.g., hazard ratio (95 per cent confidence interval) of 1.6 (1.2-2.2) ). Among white males, the age-adjusted hazard ratio comparing the lowest to the highest value of our six-level index was 2.0 (1.2-3.4), but control for potential confounders (principally cardiovascular disease risk factors) reduced this value to 1.5 (0.8-2.6). The social networks effect among white females, black males, and black females was weaker and clearly nonsignificant. Exploratory analyses suggested that marital status, church activities, and an alternate social network index predicted survivorship, but not in a dose-response fashion. Reduced survivorship among older subjects with few social ties was the most important feature of the data.

Noncommutative Harmonic Analysis

Abstract: Some basic concepts of Lie group representation theory The Heisenberg group The unitary group Compact Lie groups Harmonic analysis on spheres Induced representations, systems of imprimitivity, and semidirect products Nilpotent Lie groups Harmonic analysis on cones $\mathrm {SL}(2,R)$ $\mathrm {SL}(2, \mathbf C)$, and more general Lorentz groups Groups of conformal transformations The symplectic group and the metaplectic group Spinors Semisimple Lie groups.

Technical Note---Nonlinear Least Squares Estimation of New Product Diffusion Models

Abstract: Schmittlein and Mahajan Schmittlein, D. C., V. Mahajan. 1982. Maximum likelihood estimation for an innovation diffusion model of new product acceptance. Marketing Sci.1 Winter 57--78. made an important improvement in the estimation of the Bass Bass, F. M. 1969. A new product growth model for consumer durables. Management Sci.15 January 215--227. diffusion model by appropriately aggregating the continuous time model over the time intervals represented by the data. However, by restricting consideration to only sampling errors and ignoring all other errors such as the effects of excluded marketing variables, their Maximum Likelihood Estimation MLE seriously underestimates the standard errors of the estimated parameters. This note uses an additive error term to model sampling and other errors in the Schmittlein and Mahajan formulation. The proposed Nonlinear Least Squares NLS approach produces valid standard error estimates. The fit and the predictive validity are roughly comparable for the two approaches. Although the empirical applications reported in this paper are in the context of the Bass diffusion model, the NLS approach is also applicable to other diffusion models for which cumulative adoption can be expressed as an explicit function of time.

Kinetics of Rapid Ca2+ Release by Sarcoplasmic Reticulum. Effects of Ca2+, Mg2+, and Adenine Nucleotides

Abstract: A radioisotope flux-rapid-quench-Millipore filtration method is described for determining the effects of Ca2+, adenine nucleotides, and Mg2+ on the Ca2+ release behaviour of "heavy" sarcoplasmic reticulum (SR) vesicles. Rapid 45Ca2+ efflux from passively loaded vesicles was blocked by the addition of Mg2+ and ruthenium red. At pH 7 and 10(-9) M Ca2+, vesicles released 45Ca2+ with a low rate (k = 0.1 s-1). An increase in external Ca2+ concentration to 4 microM or the addition of 5 mM ATP or the ATP analogue adenosine 5'-(beta,gamma-methylenetriphosphate) (AMP-PCP) resulted in intermediate 45Ca2+ release rates. The maximal release rate was observed in media containing 4 microM Ca2+ and 5 mM AMP-PCP and had a first-order rate constant of 30-100 s-1. Mg2+ partially inhibited Ca2+- and nucleotide-induced 45Ca2+ efflux. In the absence of AMP-PCP, 45Ca2+ release was fully inhibited at 5 mM Mg2+ or 5 mM Ca2+. The composition of the release media was systematically varied, and the flux data were expressed in the form of Hill equations. The apparent n values of activation of Ca2+ release by ATP and AMP-PCP were 1.6-1.9. The Hill coefficient of Ca2+ activation (n = 0.8-2.1) was dependent on nucleotide and Mg2+ concentrations, whereas the one of Mg2+ inhibition (n = 1.1-1.6) varied with external Ca2+ concentration. These results suggest that heavy SR vesicles contain a "Ca2+ release channel" which is capable of conducting Ca2+ at rates comparable with those found in intact muscle. Ca2+, AMP-PCP (ATP), and Mg2+ appear to act at noninteracting or interacting sites of the channel.

Single channel measurements of the calcium release channel from skeletal muscle sarcoplasmic reticulum. Activation by Ca2+ and ATP and modulation by Mg2+.

Abstract: A high-conductance (100 pS in 53 mM trans Ca2+) Ca2+ channel was incorporated from heavy-density skeletal muscle sarcoplasmic reticulum (SR) fractions into planar lipid bilayers of the Mueller-Rudin type. cis Ca2+ in the range of 2-950 microM increased open probability (Po) in single channel records without affecting open event lifetimes. Millimolar ATP was found to be as good as or better than Ca2+ in activation; however, both Ca2+ and ATP were required to fully activate the channel, i.e., to bring Po = 1. Exponential fits to open and closed single channel lifetimes suggested that the channel may exist in many distinct states. Two open and two closed states were identified when the channel was activated by either Ca2+ or ATP alone or by Ca2+ plus nucleotide. Mg2+ was found to permeate the SR Ca channel in a trans-to-cis direction such that iMg2+/iCa2+ = 0.40. cis Mg2+ was inhibitory and in single channel recordings produced an unresolvable flickering of Ca- and nucleotide-activated channels. At nanomolar cis Ca2+, 4 microM Mg2+ completely inhibited nucleotide-activated channels. In the presence of 2 microM cis Ca2+, the nucleotide-activated macroscopic Ba conductance was inhibited by cis Mg2+ with an IC50 equal to 1.5 mM.

Sample size and bentler and Bonett's nonnormed fit index

Abstract: Bentler and Bonett's nonnormed fit index is a widely used measure of goodness of fit for the analysis of covariance structures. This note shows that contrary to what has been claimed the nonnormed fit index is dependent on sample size. Specifically for a constant value of a fitting function, the nonnormed index is inversely related to sample size. A simple alternative fit measure is proposed that removes this dependency. In addition, it is shown that this new measure as well as the old nonnormed fit index can be applied to any fitting function that measures the deviation of the observed covariance matrix from the covariance matrix implied by the parameter estimates for a model.

The random collision model and a critical assessment of diffusion and collision in mitochondrial electron transport.

Abstract: This review focuses on our studies over the past ten years which reveal that the mitochondrial inner membrane is a fluid-state rather than a solid-state membrane and that all membrane proteins and redox components which catalyze electron transport and ATP synthesis are in constant and independent diffusional motion. The studies reviewed represent the experimental basis for the random collision model of electron transport. We present five fundamental postulates upon which the random collision model of mitochondrial electron transport is founded: All redox components are independent lateral diffusants; Cytochrome c diffuses primarily in three dimensions; Electron transport is a diffusion-coupled kinetic process; Electron transport is a multicollisional, obstructed, long-range diffusional process; The rates of diffusion of the redox components have a direct influence on the overall kinetic process of electron transport and can be rate limiting, as in diffusion control. The experimental rationales and the results obtained in testing each of the five postulates of the random collision model are presented. In addition, we offer the basic concepts, criteria and experimental strategies that we believe are essential in considering the significance of the relationship between diffusion and electron transport. Finally, we critically explore and assess other contemporary studies on the diffusion of inner membrane components related to electron transport including studies on: rotational diffusion, immobile fractions, complex formation, dynamic aggregates, and rates of diffusion. Review of all available data confirms the random collision model and no data appear to exist that contravene it. It is concluded that mitochondrial electron transport is a diffusion-based random collision process and that diffusion has an integral and controlling affect on electron transport.

Immunohistochemical analyses of estrogen receptor in endometrial adenocarcinoma using a monoclonal antibody.

Abstract: Immunohistochemical localization of estrogen receptor (ER) using specific monoclonal anti-human estrogen receptor antibody, H222, with an immunoperoxidase technique was performed on fresh frozen tissue derived from 100 endometrial adenocarcinomas. Immunohistochemical evaluation incorporated both intensity and distribution of staining. In all cases, H222 localized in the nucleus of target cells. A significant quantitative relationship was shown between histological score (H-Score) and the biochemical analysis of ER content in tissue homogenates (r = 0.65, P = 0.00001). Excellent sensitivity (92%) and specificity (93%) were observed for the comparison of H-Score to the biochemical assay. Significant ER localization was present in stromal and myometrial elements, component H-Score of which correlated weakly with component H-Scores of malignant epithelial elements. Divergent receptor localization in stromal and myometrial versus malignant epithelial elements suggests that biochemical assays of endometrial carcinoma specimens may not reflect cancer-relevant receptor content. The data presented here suggest that the immunoassay of ER using H222 monoclonal antibody provides additional histochemical information to complement conventional analyses of endometrial adenocarcinomas.

Dysfunctional control by client verbal behavior: The context of reason-giving.

Abstract: Dysfunctional control exerted by reason-giving in adult psychopathology is interpreted from a radical behavioral perspective. Verbal-social contingencies which support the establishment of reason-giving and its control over maladaptive actions are reviewed. A contextual approach to psychotherapy, comprehensive distancing, which attempts to weaken dysfunctional verbal control is described briefly. Data relevant to therapeutic process are presented. The overall results suggest that comprehensive distancing facilitates therapeutic change through a process consistent with a behavioral analysis of reason-giving. Suggestions for further research and radical behavioral approaches to psychotherapy are discussed.

International human rights: a regime analysis

Abstract: After laying out a typology of international regimes, eight international and regional human rights regimes are analyzed in order to (1) examine the utility of regime analysis in noneconomic issue-areas, and (2) assess the nature, extent, and evolution of international cooperation on human rights. There has been a remarkable growth of international action since 1945, when human rights were not even widely accepted as a legitimate issue-area. This growth can be explained largely by expanding perceptions of moral interdependence and community, increased national commitment, the growing ideological appeal of human rights, and changes in the distributions of international power. These same factors, however, suggest only limited future growth. On a broader theoretical plane, the case of human rights suggests a significant, if limited and principally heuristic, utility for regime analysis, especially to the extent that international relations is becoming increasingly concerned with specific issues.

The sequence of a large L1Md element reveals a tandemly repeated 5' end and several features found in retrotransposons

Abstract: The complete nucleotide sequence of a 6,851-base pair (bp) member of the L1Md repetitive family from a selected random isolate of the BALB/c mouse genome is reported here. Five kilobases of the element contains two overlapping reading frames of 1,137 and 3,900 bp. The entire 3,900-bp frame and the 3' 600 bp of the 1,137-bp frame, when compared with a composite consensus primate L1 sequence, show a ratio of replacement to silent site differences characteristic of protein coding sequences. This more closely defines the protein coding capacity of this repetitive family, which was previously shown to possess a large open reading frame of undetermined extent. The relative organization of the 1,137- and 3,900-bp reading frames, which overlap by 14 bp, bears resemblance to protein-coding, mobile genetic elements. Homology can be found between the amino acid sequence of the 3,900-bp frame and selected domains of several reverse transcriptases. The 5' ends of the two L1Md elements described in this report have multiple copies, 4 2/3 copies and 1 2/3 copy, of a 208-bp direct tandem repeat. The sequence of this 208-bp element differs from the sequence of a previously defined 5' end for an L1Md element, indicating that there are at least two different 5' end motifs for L1Md.

Diversification Categories in Investment Real Estate

Abstract: This paper continues previous work evaluating the benefits of diversification and analyzes the various dimensions within the commercial real estate opportunity set. The database is large and extends through the 1982 downturn in property values. Due to the low levels of systematic risk, current distinctions by region and property type make little sense in a world of costly diversification. More exacting categories combining property type, SMSA growth rate and lease maturity offer promise for more efficient diversification within the real estate portfolio.

On the naturalness of stop consonant voicing

Abstract: A long recognized problem for linguistic theory has been to explain why certain sounds, sound oppositions, and sound sequences are statistically preferred over others among languages of the world. The formal theory of markedness, developed by Trubetzkoy and Jakobson in the early 1930's, and extended by Chomsky and Halle (1968), represents an attempt to deal with this problem. It is at least implicit in that theory that sounds are rare when (and because) they are marked, and common when (and because) they are not. Whether sounds are marked or unmarked depends – in the latter version of the theory, particularly – upon the ‘intrinsic content’ of acoustic and articulatory features which define them. There was, however, no substantive attempt among early proponents of the theory to show what it was about the content of particular features and feature combinations that caused them to be marked, and others not.