Showing papers by "University of Massachusetts Amherst published in 1983"

Neuronlike adaptive elements that can solve difficult learning control problems

Abstract: It is shown how a system consisting of two neuronlike adaptive elements can solve a difficult learning control problem. The task is to balance a pole that is hinged to a movable cart by applying forces to the cart's base. It is argued that the learning problems faced by adaptive elements that are components of adaptive networks are at least as difficult as this version of the pole-balancing problem. The learning system consists of a single associative search element (ASE) and a single adaptive critic element (ACE). In the course of learning to balance the pole, the ASE constructs associations between input and output by searching under the influence of reinforcement feedback, and the ACE constructs a more informative evaluation function than reinforcement feedback alone can provide. The differences between this approach and other attempts to solve problems using neurolike elements are discussed, as is the relation of this work to classical and instrumental conditioning in animal learning studies and its possible implications for research in the neurosciences.

Liposomes containing modified cholesterol for organ targeting

Abstract: Phospholipid liposomes are provided having an outer layer including a cholesterol derivative such as a cholesterol ester and an aqueous medium confined by the layer which includes a tracer agent, a cytoxic agent or a therapeutic agent. The liposomes are adapted for specific organ targeting.

A Theoretical Perspective for Understanding Reactions to Victimization

Abstract: Although specific victimizations may differ, there appear to be common psychological responses across a wide variety of victims. It is proposed that victims' psychological distress is largely due to the shattering of basic assumptions held about themselves and their world. Three assumptions that change as a result of victimization are: 1) the belief in personal invulnerability; 2) the perception of the world as meaningful; and 3) the view of the self as positive. Coping with victimization is presented as a process that involves rebuilding one's assumptive world. Introductions to the papers that follow in this issue are incorporated into a discussion of specific coping strategies adopted by victims.

Aggregation and beyond: Some basic issues on the prediction of behavior.

Abstract: Failure to appreciate the role that aggregation plays in increasing reliability and validity and in establishing the range of generalization of findings has resulted in misunderstandings about the stability of behavior across time and situations, and in the conduct of experiments that produce results that tend to be neither generalizable nor replicable. Appropriate aggregation can reduce error variance associated with the unrepresentativeness of individual stimuli, situations, occasions, judges, items of behavior, and subjects. Inappropriate aggregation can result not only in a loss of information but also in a reduction in reliability as well as validity. Different approaches to prediction with single items of behavior are discussed, and it is concluded that single items tend to be too unreliable and too narrow in scope to measure broad dispositions such as traits. A major emphasis is that behavior is often so highly situationally specific that unless this is taken into account by procedures such as aggregation over situations and/or occasions, or by the investigation of events that are so highly ego-involving that experimental effects dominate situation-ally unique effects, results will tend to be unreplicable or ungeneralizable, no matter what their level of statistical significance.

Anatomical Data for Analyzing Human Motion

Abstract: Anatomical data necessary for the analysis of human motion are presented on the total living body segmented into sixteen parts. Cadaver data from Dempster (1955) are applied to water displacement data obtained on 135 living subjects (35 men and 100 women) to obtain the weight, center of gravity, and radius of gyration for the segmented extremities. Thirty-three of these subjects (15 men and 18 women) were used to obtain the weight of the segments of the trunk, using the water displacement method, and sixteen of these subjects (7 men and 9 women) were used to locate the center of gravity of each trunk segment. A lead model was constructed using the trunk data to obtain the radii of gyration in both the sagittal and frontal planes. A single male cadaver was dissected to compare the trunk measurements with the lead model results.

Considerations for millimeter wave printed antennas

Abstract: Calculated data are presented on the performance of printed antenna elements on substrates which may be electrically thick, as would be the case for printed antennas at millimeter wave frequencies. Printed dipoles and microstrip patch antennas on polytetrafluoroethylene (PTFE), quartz, and gallium arsenide substrates are considered. Data are given for resonant length, resonant resistance, bandwidth, loss due to surface waves, loss due to dielectric heating, and mutual coupling. Also presented is an optimization procedure for maximizing or minimizing power launched into surface waves from a multielement printed antenna array. The data are calculated by a moment method solution.

Radioactive labeling of antibody: a simple and efficient method

Abstract: A simple and efficient method of covalently coupling the strong chelator diethylenetriaminepentaacetic acid to proteins was developed for radiolabeling immunoglobulin G antibodies. After being coupled and labeled with indium-111, a monoclonal antibody to carcinoembryonic antigen retained its ability to bind to its antigen in vitro and in vivo. In nude mice with a human colorectal xenograft, 41 percent of the injected radioactivity became localized in each gram of xenograft at 24 hours compared with 9 percent for control antibody and 19 percent for radioiodinated antibody to carcinoembryonic antigen.

Evaluating With Sense The Theory-Driven Approach

Abstract: Arguing for more serious theorizing in connection with evaluation, this article shows that although the randomized controlled experiment conceptualized as a "black box" approach has dominated the d...

Visual cortical neurons as localized spatial frequency filters

Abstract: This paper relates to the receptive field properties of neurons in the primary visual cortex, i.e. the striate cortex, to current issues in spatial visual information processing. Particular attention is given to the fact that receptive field profiles of simple cells in the visual cortex often resemble even-symmetric or odd-symmetric Gabor filters; i.e. their receptive field profiles can be described by the product of a Gaussian and either a cosine or sine function. Their spatial frequency tuning is of medium bandwidth (~one octave) which is narrow enough for a cell to distinguish the third harmonic from the fundamental frequency for square-wave gratings of low spatial frequency. The responses of adjacent simple cells, tuned to the same spatial frequency, orientation, and direction, differ in their phase response to drifting sine-wave gratings by approximately either 90° or 180°. This latter result makes it possible to consider two adjacent simple cell pairs as operating like paired Gaussian-attenuated sine and cosine filters of Gabor filters for restricted regions of visual space. The entire set of simple cells provides a complete representation of the visual scene, yet each simple cell is unique in its response properties. At the complex cell stage, the cell's mean firing rate appears to represent the amplitude of a local Fourier coefficient, but phase information is seldom conveyed with much precision in the action potential code.

Cognitive strategies and looping constructs: an empirical study

Abstract: Authors' Present Addresses: Elliot Soloway and Kate Ehrlich, Department of Computer Science, Yale University, P.O. Box 2158, New Haven, CT 06520; Jeffrey Bonar, Learning Research and Development Center, Univ. of Pittsburgh, Pittsburgh, PA 15260. This work was supported by the Army Research Institute for the Behavioral and Social Sciences. under ARI Grant No. MDA903-80-C-0508. This work was also supported by the National Science Foundation under NSF Grant SED-81-12403. Any opinions, findings, conclusions or recommendations expressed in this report are those of the authors, and do not necessarily reflect the views of the U.S. Government. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. © 1983 ACM 0001-0782/83/1100-0853 75¢ ELLIOT SOLOWA Y Yale University JEFFREY BONAR University of Massachusetts

Bias and error in human judgment

Abstract: Currently prevalent views of human inference are contrasted with an integrated theory of the epistemic process. The prevailing views are characterized by the following orienting assumptions: (1) There exist reliable criteria of inferential validity based on objectively veridical or optimal modes of information processing. (2) Motivational and cognitive factors bias inferences away from these criteria and thus enhance the likelihood of judgmental error. (3) The layperson's epistemic process is pluralistic; it consists of a diverse repertory of information-processing strategies (heuristics, schemas) selectively invoked under various circumstances. By contrast, the present analysis yields the following conclusions: (1) There exist no secure criteria of validity. (2) Psychological factors that bias inferences away from any currently accepted criteria need not enhance the likelihood of error. (3) The inference process may be considered unitary rather than pluralistic. The various strategies and biases discussed in the literature typically confound universal epistemic process with specific examples (or contents) of such processes. Empirical support for the present analysis is presented, including evidence refuting proposals that specific contents of inference are of universal applicability; evidence suggesting that people do not, because of a reliance on subnormative heuristics, underutilize nonnative statistical information—rather, people seem unlikely to utilize any information if it is nonsalient or (subjectively) irrelevant; and evidence demonstrating that the tendency of beliefs to persevere despite discrediting information can be heightened or lowered by introducting appropriate motivational orientations.

Meaning of “Percent Parasitism” in Studies of Insect Parasitoids

Abstract: In simulation models, host and parasitoid phenologies influenced values seen in percent parasitism samples, making them poor indicators of total parasitoid impact per host generation. Key factors were relative entry and exit rates of hosts and parasitoids and degree of overlap between entry and exit of either parasitoids or hosts. Parasitism of tissue-feeding-stage larvae of the apple blotch leafminer, Phyllonorycter crataegella (Clemens), exemplified distortion of sample percent parasitism values by one of the processes examined in the simulation models, namely, differential emergence rates of parasitized and nonparasitized hosts. Recommended practices for strengthening future studies of parasitoid impact include: (1) rigorous definition of the susceptible stage, (2) delineation of phenologies of the susceptible host stage and the immature parasitoid stage, (3) assessment of the behavior of parasitized hosts, (4) avoidance of sampling before completion of parasitoid attack, and (5) avoidance of summation across samples or equating of peak and generational levels of parasitism.

Lipisomes containing gas for ultrasound detection

Abstract: Phospholipid liposomes are provided having a lipid bilayer surrounding a confined composition which includes a gas or a gas precursor. The liposomes can be administered to a patient and can be detected in vivo by ultrasound techniques which permit organ imaging.

Close Friendship in Adulthood: Conversational Content Between Same-Sex Friends.

Abstract: This study was designed to examine ongoing close friendships among same-sex adults. An analysis of frequency and depth of conversational topics was undertaken. The self-reports of female participants showed that they converse more frequently than the male participants about intimate topics and daily and shared activities. Sex differences on depth of topic discussion also emerged, with females reporting greater depth in topics involving personal and family matters. Sports was the only topic for which males, rather than females, reported both more frequent discussion and conversation in greater depth. The topic frequency data were factor analyzed for each sex group. The factor analyses indicated patterns for the males on “personal issues,” “sociocultural issues,” and “activity” and patterns for females on “domestic matters,” “personal issues,” and “worldly issues.” The results of the study generally support sex-stereotypical assumptions about the nature of male-male and female-female conversations.

The use of meta-level control for coordination in a distributed problem solving network

Abstract: Distributed problem solving networks provide an interesting application area for meta-level control through the use of organizational structuring. We describe a decentralized approach to network coordination that relies on each node making sophisticated local decisions that balance its own perceptions of appropriate problem solving activity with activities deemed important by other nodes. Each node is guided by a high-level strategic plan for cooperation among the nodes in the network. The high-level strategic plan, which is a form of meta-level control, is represented as a network organizational structure that specifies in a general way the information and control relationships among the nodes. An implementation of these ideas is briefly described along with the results of preliminary experiments with various network problem solving strategies specified via organizational structuring. In addition to its application to Distributed Artificial Intelligence, this research has implications for organizing and controlling complex knowledge-based systems that involve semi-autonomous problem solving agents.

Small‐angle X‐ray scattering studies of microdomain structure in segmented polyurethane elastomers

Abstract: The small-angle x-ray scattering (SAXS) technique has been used to characterize the detailed microphase structure of two crosslinked segmented polyurethane elastomers. Both copolymers contain trifunctional polypropylene ether triols in the rubbery elastomeric block, but are synthesized with different hard segments: a symmetric 4,4′-diphenylmethane diisocyanate (MDI) chain extended with butanediol (BD); and an 80/20 mixture of asymmetric 2,4-toluene diisocyanate (TDI) and symmetric 2,6-toluene diisocyanate (TDI) chain extended with ethylene glycol (EG). Calculations of SAXS invariants and determinations of deviations from Porod's law are used to examine the degree of phase segregation of the hard- and soft-segment domains. Results show that the overall degree of phase separation is poorer in the asymmetric TDI/EG-based copolymer than in the symmetric MDI/BD-based copolymer. Determination of diffuse phase boundary thicknesses, however, reveals that the domain boundaries are sharper in the asymmetric TDI/EG system. The contrasting morphologies found in the two systems are interpreted in terms of differences in hard-soft segment compatibility, diisocyanate symmetry, and diisocyanate length. Coupled with conformational considerations, this information is used to construct a new model for polyurethane hard-segment microdomain structure. Important features of the model are that it takes into account the effects of hard-segment sequence length distribution and allows for folding of the longer hard-segment sequences back into the hard-segment domain.

Redundancy, the Discrete Fourier Transform, and Impulse Noise Cancellation

Abstract: The relationship between the discrete Fourier transform and error-control codes is examined. Under certain conditions we show that discrete-time sequences carry redundant information which then allow for the detection and correction of errors. An application of this technique to impulse noise cancellation for pulse amplitude modulation transmission is described.

Passive transfer of diabetes in the BB/W rat.

Abstract: Severe diabetes with insulitis was produced in young diabetes-prone BB/W rats by passive transfer of concanavalin A-treated spleen cells from BB/W animals with acute diabetes. Spleen cells alone or in combination with lymph node cells were active in transferring disease.

Modeling of transport of small molecules in polymer blends: Application of effective medium theory

Abstract: This article concerns itself with the prediction of effective diffusion coefficients of small permeants in binary polymer blends of varying degrees of miscibility and microstructural order. Several models have been critically evaluated with the help of previously published experimental data and in terms of consistency of morphological information provided by small permeants serving as morphological probes. Completely random, two-phase media have been modeled in terms of Effective Medium Theory with the coordination number (z) describing the average morphology. A comprehensive analysis of experimental data has shown a correlation between z and various physical situations. Near the percolation threshold, z attains a maximum value while, above it, z tends to decrease with increasing content of the conductive component. Accurate predictions of effective diffusivity can be made for volume fractions between 0.3 and 0.8 by letting z = 6. Evidence for phase inversion was studied in terms of models with ordered microstructure and transport data.

Symptomatic shoulder instability due to lesions of the glenoid labrum.

Abstract: Lesions of the glenoid labrum can be associated with and cause shoulder instability and symptomatology by (1) allowing the shoulder to dislocate recurrently (anatomical instability); (2) allowing the shoulder to subluxate (anatomical instability); and (3) allowing the shoulder to click, catch, and lock secondary to partially attached fragments becoming interposed between the articular surfaces (functional instability). The latter two clinical entities are usually associated with "lesser" labral damage and diagnosis can be difficult. Six illustrative cases are presented and salient diagnostic and therapeutic points are discussed. The glenohumeral axillary arthrotomogram is presented as a sensitive diagnostic test for detecting labral lesions.