Showing papers by "University of Massachusetts Amherst published in 1980"

Goodness of fit tests for the multiple logistic regression model

Abstract: Several test statistics are proposed for the purpose of assessing the goodness of fit of the multiple logistic regression model. The test statistics are obtained by applying a chi-square test for a contingency table in which the expected frequencies are determined using two different grouping strategies and two different sets of distributional assumptions. The null distributions of these statistics are examined by applying the theory for chi-square tests of Moore Spruill (1975) and through computer simulations. All statistics are shown to have a chi-square distribution or a distribution which can be well approximated by a chi-square. The degrees of freedom are shown to depend on the particular statistic and the distributional assumptions. The power of each of the proposed statistics is examined for the normal, linear, and exponential alternative models using computer simulations.

The Hearsay-II Speech-Understanding System: Integrating Knowledge to Resolve Uncertainty

Abstract: The Hearsay-II system, developed during the DARPA-sponsored five-year speech-understanding research program, represents both a specific solution to the speech-understanding problem and a general framework for coordinating independent processes to achieve cooperative problem-solving behavior. As a computational problem, speech understanding reflects a large number of intrinsically interesting issues. Spoken sounds are achieved by a long chain of successive transformations, from intentions, through semantic and syntactic structuring, to the eventually resulting audible acoustic waves. As a consequence, interpreting speech means effectively inverting these transformations to recover the speaker's intention from the sound. At each step in the interpretive process, ambiguity and uncertainty arise. The Hearsay-II problem-solving framework reconstructs an intention from hypothetical interpretations formulated at various levels of abstraction. In addition, it allocates limited processing resources first to the most promising incremental actions. The final configuration of the Hearsay-II system comprises problem-solving components to generate and evaluate speech hypotheses, and a focus-of-control mechanism to identify potential actions of greatest value. Many of these specific procedures reveal novel approaches to speech problems. Most important, the system successfully integrates and coordinates all of these independent activities to resolve uncertainty and control combinatorics. Several adaptations of the Hearsay-II framework have already been undertaken in other problem domains, and it is anticipated that this trend will continue; many future systems necessarily will integrate diverse sources of knowledge to solve complex problems cooperatively. Discussed in this paper are the characteristics of the speech problem in particular, the special kinds of problem-solving uncertainty in that domain, the structure of the Hearsay-II system developed to cope with that uncertainty, and the relationship between Hearsay-II's structure and those of other speech-understanding systems. The paper is intended for the general computer science audience and presupposes no speech or artificial intelligence background.

Asymmetry of the effective visual field in reading.

Abstract: In three experiments, subjects’ eye movements were recorded as they read from a computer-controlled CRT. The amount of information available to the left and right of the fixation point was varied in order to determine the characteristics of the effective visual field in reading. Experiments 1 and 2 demonstrated that readers do not obtain useful information during a fixation more than 3 or 4 letters to the left of their fixation point. The results of Experiment 3 indicated that the effective visual field does not extend any further to the left than the beginning of the word currently fixated, independent of the number of letters available to the left of fixation. When combined with the results of other research on the perceptual span in reading, the results of these experiments indicate that the effective visual field extends from the beginning of the currently fixated word (but no further than 4 characters to the left of fixation) up to about 15 characters to the right of fixation.

Carrier and Bit Synchronization in Data Communication--A Tutorial Review

Abstract: This paper examines the problems of carrier phase estimation and symbol timing estimation for carrier-type synchronous digital data signals, with tutorial objectives foremost. Carrier phase recovery for suppressed-carrier versions of double sideband (DSB), vestigial sideband (VSB), and quadrature amplitude modulation (QAM) signal formats is considered first. Then the problem of symbol timing recovery for a baseband pulse-amplitude modulation (PAM) signal is examined. Timing recovery circuits based on elementary statistical properties are discussed as well as timing recovery based on maximum-likelihood estimation theory. A relatively simple approach to evaluation of timing recovery circuit performance in terms of rms jitter of the timing parameters is presented.

The Multi-Goal, Theory-Driven Approach to Evaluation: A Model Linking Basic and Applied Social Science

Abstract: A source of one of the more serious problems of evaluation research is the typical finding that evaluated programs have little or no effectiveness. Recently, claims have been made that the problem of no effect may be attributed to the inadequacy of current evaluation methodology. In this paper, the reasons for no effect in current program evaluation are analyzed theoretically. In order to cope with this problem, an alternative evaluation method, the "multi-goal, theory-driven" approach, is proposed. The principles, procedures, and justification of this new evaluation approach are discussed. Finally, the advantages of applying the multi-goal, theory-driven approach to program evaluation are illustrated.

Epoxy‐water interactions

Abstract: It has been shown that sorbed moisture plasticizes epoxy resins with a resultant depression in the glass transition temperature of the polymer. The nature of the epoxy-water interaction still requires further investigation. The equilibrium sorption and diffusion of water in a high Tg epoxy is examined. Other analytical techniques including differential scanning calorimetry, infrared spectroscopy, electron microscopy and nuclear magnetic resonance are applied to the system. Experimental results suggest that the sorbed water at low concentrations is strongly localized at specific segments or groups in the polymer. Discussion is given relative to the structure-properties of the epoxy and its possible correlation to the experimental data obtained.

Solvent extraction of anthocyanins from wine pomace

Abstract: There is considerable interest in utilization of natural pigment as food colorants, particularly from raw materials in adequate supply, such as wine grape pomace. The rate and degree of extraction of anthocyanins from grape pomace depends upon a number of factors; this research concerned two: solvent (ethanol, methanol, water), and acid (HCl, citric, tartaric, formic, acetic, propionic). Methanol was the best extractant being 20% more effective than ethanol and 73% more effective than water. HCl was most effective with ethanol, but is also very corrosive. Of the organic acids, citric was most effective with methanol and acetic acid with water.

Erratum to: Formation of attentional-associative networks in real time: Role of the hippocampus and implications for conditioning

Abstract: The function of the hippocampus in conditioning is portrayed in terms of an extension of Mackintosh’s (1975) attention theory, which describes the evolution of the salience (associability) of each stimulus in the situation, including the context, and its predictive associative relationship to itself and all other stimuli In terms of the model, the hippocampus is essential for computations that reduce salience when a stimulus is presented in the context of other stimuli that are better predictors of events The model is applied to the phenomena of latent inhibition and blocking

Thermotropic Liquid Crystalline Polyesters with Rigid or Flexible Spacer Groups

Abstract: Several different series of rigid and flexible polyesters with main chain liquid crystalline units were prepared and their properties were examined in relation to their structures. The first group of polymers were rigid aromatic copolyesters with mesogenic groups based on either chloro or methyl hydroquinone terephthalate units combined with varying amounts of different types of bisphenol terephthalate units The bisphenol comonomers used contained the structure: in which X was none, C(CH3)2, CH2, O, S, and So2. It was observed that the bisphenols with the bulkier X group were more efficient in destroying thermotropic liquid crystallinity of the resulting copolymers. The second group of polymers studied were flexible polyesters consisting of various types of mesogenic units which were connected together by different lengths of polymethylene flexible spacers. The liquid crystalline behaviours of these polymers, particularly their transition temperatures, were correlated with their structures. A brief review of previous studies on the synthesis of thermotropic liquid crystalline polyesters is included.

Characterization of the lipopolysaccharide from Actinobacillus actinomycetemcomitans Y4 and N27.

Abstract: The lipopolysaccharide (LPS) from Actinobacillus actinomycetemcomitans strains Y4 and N27 was isolated by the phenol-water procedure. Morphologically, the molecule consisted of ribbon and branched filaments which comprised 3% of the cellular dry weight. Chemical analysis of the isolated and purified LPSs of both strains showed them to consist of carbohydrate, lipid, 2-keto-3-deoxyoctonate, heptose, hexosamine, and phosphate. The major fatty acids of the lipid A moiety were saturated C14 and beta-OH C14 compounds. Rhamnose, fucose, galactose, glucose, heptose, glucosamine, and galactosamine comprised the monosaccharide portion of the LPS. Biological activity studies revealed both LPS molecules to be active in the Schwartzman reaction and in in vitro 45Ca bone resorption, as well as in macrophage activation and lethality and in platelet aggregation.

System dynamics modeling

Abstract: The System Dynamics approach to modeling social systems appears to be gaining rapid acceptance as a legitimate tool of management science even as it still evokes controversy. Some of its basic assumptions, strategies and conventions are indicated. Modeling with this methodology is described. Primarily for pedagogical reasons, four approaches to starting a model are identified with some indications as to which of some of the published models might have used them. Finally, the issue of nonlinear relationships is raised. Some of the ways in which this matter can be dealt with are sketched.

Treponema bryantii sp. nov., a rumen spirochete that interacts with cellulolytic bacteria

Abstract: A saccharolytic spirochete that associated and interacted with cellulolytic bacteria was isolated from bovine rumen fluid. Isolation was accomplished by means of a procedure involving serial dilution of a sample of rumen fluid into a cellulose-containing agar medium. Clear zones appeared within the medium as a result of cellulose hydrolysis by rumen bacteria. The saccharolytic spirochete and a cellulolytic bacterium later identified as a strain of Bacteroides succinogenes were isolated from the clear zones. The spirochete did not utilize cellulose, but grew in coculture with the cellulolytic bacterium in cellulose-containing media. When cocultured in these media the spirochete used, as fermentable substrates, soluble sugars released from cellulose by the cellulolytic bacterium. In cellulosecontaining agar medium the spirochete enhanced cellulose breakdown by the B. succinogenes strain. Electron microscopy showed that the helical spirochete cells possessed an outer sheath, a protoplasmic cylinder, and two periplasmic fibrils. Under a CO2 atmosphere, in a reduced medium containing inorganic salts, rumen fluid, glucose, and NaHCO3, the spirochete grew to a final density of 1.9×109 cells/ml. Succinate, acetate, and formate were products of the fermentation of glucose by growing cells. CO2 (HCO3 -), branched short-chain fatty acids, folic acid, biotin, niacinamide, thiamine, pyridoxal, and a carbohydrate were required for growth of the spirochete. The results of this study indicated that the rumen spirochete represents a new species of Treponema. It is proposed that the new species be named Treponema bryantii.

Tetracycline-labeled human bone from ancient Sudanese Nubia (A.D. 350)

Abstract: Nubian bone recovered from an X-group cemetery (A.D. 350 to 550) exhibits a pattern of fluorescence identical to that of modern tetracycline-labeled bone. When it is viewed under ultraviolet light at 490 angstroms, fluorophors are visible as a characteristic yellow-green fluorescence on surfaces that were actively mineralizing at the time of exposure. Contamination of stored grains provided the proper environment for cultivation of tetracycline-producing Streptomycetes. Evidence for exposure to antibiotics in an archeological population is relevant to studies of the evolution of R factors and to the interpretation of health and disease within the population.

Rheology of concentrated solutions of helical polypeptides

Abstract: Rheological studies were carried out on concentrated m-cresol solutions of two helical synthetic polypeptides; poly-γ-benzyl-L-glutamate (PBLG; molecular weight, 150,000) and poly-ϵ-carbobenzyloxy-L-lysine (PCBZL; molecular weight, 200,000). Steady shear measurements were made over a range of 0.01–16,000 sec−1 to obtain steady shear viscosity and first normal stress difference. Dynamic viscosity and dynamic storage modulus were measured both by oscillatory shear between cone and plate and also by an eccentric rotating disk device over frequency ranges of 0.1–400 and 0.1–63 rad/sec, respectively. The concentration ranges were such that both liquid crystalline and isotropic solutions were investigated. The previously reported observations of an apparent negative first normal stress difference within a defined range of shear rate for liquid crystalline solutions were confirmed for the PBLG and PCBZL solutions. At high shear rates the peaks in plots of steady shear viscosity against concentration were profoundly suppressed but peaks in first normal stress difference versus concentration were not. The observation of liquid crystalline order in PCBZL/m-cresol solutions at room temperature constitutes evidence that the inverse coil-helix transition temperature is lower in concentrated solutions than in dilute solutions. The critical concentration for formation of the liquid crystalline phase was higher for PCBZL than for PBLG, despite a higher axial ratio, due to helix flexibility.

Industrial safety hazard reduction through performance feedback

Abstract: A "feedback package" system, designed to prevent occupational accidents and to fit directly into the normal operations of an industrial organization, was analyzed. Eighteen hazardous conditions in six production departments were assessed during seven observation sessions over a 12-week period, plus four follow-up observations over 4 months. The "feedback package" was presented in multiple baseline fashion, across subjects (department supervisors). It consisted of presenting the supervisor with copies of observational data, accompanied by a note which congratulated good practices and suggested ways for improving safety conditions, along with occasional comments from a senior executive. The results indicated that during the feedback phase, hazard rates were lower and less variable than during the baseline phase. Baseline data were highly variable with peaks ranging from 20 to 55 hazards per department. Following intervention, hazard frequencies dropped by 60%, averaged across departments, with decreases ranging from 29% to 88%. During treatment, data stabilized, with the highest frequency reaching 33. A modified feedback system was implemented by the organization following termination of the study, validating the assumption that such a system would tend to maintain.

Role of pollinators in the evolution of dioecy from distyly.

Abstract: Distylous flowering plant species are characterized by having two types of individuals that bear different forms of flowers: "pin" flowers with long styles and short stamens and "thrum" flowers with short styles and long stamens (Darwin, 1877; Frankel and Galun, 1977). In most cases this flower dimorphism is associated with a physiological self-incompatibility mechanism that prevents fertilization after self-pollination or pollen transfer between individuals of the same flower type, with the result that only pollination between forms results in fertilization (Frankel and Galun, 1977; de Nettancourt, 1977). In several angiosperm genera, distyly has evolved into dioecy (Baker, 1958, 1959; Bir Bahadur, 1968; Ornduff, 1966; Viulleumier, 1967; Opler et al., 1975), and in every case individuals bearing female flowers are evolutionarily derived from long-style individuals, while male plants are derived from the shortstyle form. The selective forces that may have brought about this transformation are not well understood (Lloyd, 1979). Here we propose a hypothesis to explain the evolution of distyly into dioecy.

On the Paucity of Positive Emotions

Abstract: The positive emotions have proved to be a source of embarrassment to psychologists. Discussions of fear, anxiety, depression, anger, grief, etc., are plentiful in the psychological literature. But when it comes to emotions such as joy, mirth, love, mystical experiences, and the like, psychologists are often at a loss for words. Thus, in a content analysis of psychological textbooks, Carlson (1967) found that approximately twice as much space was devoted to negative as to positive emotions. Although Carlson’s analysis is now somewhat out of date, I doubt that a survey of current textbooks would reveal a major change in emphasis (except perhaps for a recent upsurge of interest in issues related to sexual behavior, including romantic love).

Environmentally dependent sensitive periods for avian vocal learning

Abstract: Experience during brief periods of development can exert a profound influence on later life1. Among songbirds, experimental evidence for enhanced vocal learning during a relatively brief period early in life is well documented2,3. The timing of vocal learning with respect to dispersal is fundamental to our understanding of many population processes, yet the significance of the sensitive period remains unclear. We report here that in our study of the marsh wren (Cistothorus palustris), a North American songbird, we found that the sensitive period for song learning is not rigidly programmed with respect to dispersal and/or migration; two environmental factors, the photoperiod and the amount of adult song heard during the hatching year, influence the nature of the sensitive period during the hatching year, the ability to learn further the next spring, and the relative dates at which young males develop their adult songs.

Rheo-Optical Studies of Liquid Crystalline Solutions of Helical Polypeptides

Abstract: The shear dependence of structures of liquid crystalline solutions of Poly-γ-benzyl-l-glutamate PBLG in m-cresol was examined in a polarizing microscope using a specially constructed shearing stage and stroboscopic illumination. Three different textures were observed depending on shear rate. The shear rates at which the texture changes occurred correlated well with the changes in sign of the first normal stress difference reported earlier.1,2 The region of negative first normal stress difference corresponded to a texture consisting of striations perpendicular to shear. The transverse striations were also observed to develop over a period of seconds or minutes after cessation of shear at rates within the first positive region of N 1, These striations could be fixed in a dried film by using a volatile helicogenic solvent (1,4-dioxane). A speculative model is proposed to account for the rheological observations in Refs.1,2 and the rheo-optical observations reported herein.

Pollen Tube Growth Rates in Zea mays: Implications for Genetic Improvement of Crops.

Abstract: Speed of pollen tube growth is positively correlated with the quality of the resultant sporophytic generation. Therefore, gametophytic competition may be an important adaptive mechanism. Furthermore, pollen tube growth rates may be used to predict the quality of F1crosses in crop species.

Extracting and Labeling Boundary Segments in Natural Scenes

Abstract: This paper describes a set of algorithms used to perform segmentation of natural scenes through boundary analysis. The techniques include preprocessing, differentiation using a very simple operator, relaxation using case analysis, and postprocessing. The system extracts line segments as connected sets of edges, labels them, and computes features for them such as length and confidence.