Showing papers by "University of Illinois at Urbana–Champaign published in 1978"

Computational Geometry: An Introduction

Abstract: From the reviews: "This book offers a coherent treatment, at the graduate textbook level, of the field that has come to be known in the last decade or so as computational geometry...The book is well organized and lucidly written; a timely contribution by two founders of the field. It clearly demonstrates that computational geometry in the plane is now a fairly well-understood branch of computer science and mathematics. It also points the way to the solution of the more challenging problems in dimensions higher than two."

The Case Study Method in Social Inquiry

Abstract: It is widely believed that case studies are useful in the study of human affairs because they are down-to-earth and attention-holding but that they are not a suitable basis for generalization. In this paper, I claim that case studies will often be the preferred method of research because they may be epistemologically in harmony with the reader’s experience and thus to that person a natural basis for generalization.

The Simulation of Three-Dimensional Convective Storm Dynamics

Abstract: A new three-dimensional cloud model has been developed for investigating the dynamic character of convective storms. This model solves the compressible equations of motion using a splitting procedure which provides numerical efficiency by treating the sound wave modes separately. For the subgrid turbulence processes, a time-dependent turbulence energy equation is solved which depends on local buoyancy, shear and dissipation. First-order closure is applied to nearly conservative variables with eddy coefficients based on the computed turbulence energy. Open lateral boundaries are incorporated in the model that respond to internal forcing and permit gravity waves to propagate out of the integration domain with little apparent reflection. Microphysical processes are included in the model using a Kessler-type parameterization. Simulations conducted for an unsheared environment reveal that the updraft temperatures follow a moist adiabatic lapse rate and that the convection is dissipated by water loadin...

Pupils and Paradigms: a Review of Literature Related to Concept Development in Adolescent Science Students

Abstract: (1978). Pupils and Paradigms: a Review of Literature Related to Concept Development in Adolescent Science Students. Studies in Science Education: Vol. 5, No. 1, pp. 61-84.

On a Real-Time Scheduling Problem

Abstract: We study the problem of scheduling periodic-time-critical tasks on multiprocessor computing systems. A periodic-time-critical task consists of an infinite number of requests, each of which has a prescribed deadline. The scheduling problem is to specify an order in which the requests of a set of tasks are to be executed and the processor to be used, with the goal of meeting all the deadlines with a minimum number of processors. Since the problem of determining the minimum number of processors is difficult, we consider two heuristic algorithms. These are easy to implement and yield a number of processors that is reasonably close to the minimum number. We also analyze the worst-case behavior of these heuristics.

On the Importance of Self-Determination for Intrinsically-Motivated Behavior:

Abstract: Yoked pairs of subjects solved puzzles such that one member of each pair was given choice about what puzzles to work on and how much time to allot to each, while the yoked subject was assigned the same puzzles and time allotments as those chosen by the first subject. It was predicted and found that subjects who chose the activities and time allotments -in other words, who had additional self-determination--would be more intrinsically motivated than subjects doing the same activity without choice.

Critical evaluation of the potential error in pharmacokinetic studies of using the linear trapezoidal rule method for the calculation of the area under the plasma level--time curve.

Abstract: The linear trapezoidal rule method is commonly used for the estimation of the area under the plasma level-time curve. Error analyses are performed when the method is used in first-order absorption and first-order elimination kinetics in the one-compartment system. It is found that significant underestimations and overestimations in area during the absorption phase and postabsorption phase, respectively, can occur when the method is improperly used. During the exponential postabsorption phase the relative error is only a function of the ratio (n) of the time interval over the half-life of the two plasma data points in the interval. The error from the linear trapezoidal rule method at n = 0.5 is about 1%. The error increases to 15.5% and 57.1% when n is increased to 2 and 4, respectively. It is recommended that for most absorption studies the linear trapezoidal method be used for prepeak and plateau plasma data and the logarithmic trapezoidal method for postpeak plasma data.

An English language question answering system for a large relational database

Abstract: By typing requests in English, casual users will be able to obtain explicit answers from a large relational database of aircraft flight and maintenance data using a system called PLANES. The design and implementation of this system is described and illustrated with detailed examples of the operation of system components and examples of overall system operation. The language processing portion of the system uses a number of augmented transition networks, each of which matches phrases with a specific meaning, along with context registers (history keepers) and concept case frames; these are used for judging meaningfulness of questions, generating dialogue for clarifying partially understood questions, and resolving ellipsis and pronoun reference problems. Other system components construct a formal query for the relational database, and optimize the order of searching relations. Methods are discussed for handling vague or complex questions and for providing browsing ability. Also included are discussions of important issues in programming natural language systems for limited domains, and the relationship of this system to others.

Neural organization and evolution of thermal regulation in mammals.

Abstract: This article proposes a modification of the currently accepted view of the central neural integration of body temperature In place of a single integrator with multiple inputs and outputs, the new model includes as many integrators as there are thermoregulatory responses Futhermore, these integrators are postulated to be represented at many levels of the nervous system, with each level facilitated or inhibited by levels above and below The purpose of such a complicated arrangement is to achieve finer and finer control over body temperature A consideration of how endothermy might have evolved, with originally nonthermally related responses gradually coming under thermal control, makes such a brain organization highly reasonable

3'-terminal labelling of RNA with T4 RNA ligase.

Abstract: T4 RNA LIGASE catalyses the formation of an internucleotide phosphodiester bond between an oligonucleotide donor molecule with a 5′-terminal phosphate and an oligonucleotide acceptor molecule with a 3′-terminal hydroxyl1–3. Although the minimal acceptor must be a trinucleoside diphosphate, dinucleoside pyrophosphates and mononucleoside 3′,5′-bisphosphates (pNps) are effective donors in the intermolecular reaction4–6. We demonstrate here that various high molecular weight RNA molecules are acceptors in the RNA ligase reaction even when present in very low concentrations in the reaction mixture. One immediate consequence of this observation is that a convenient method for labelling the 3′ end of RNA molecules in vitro becomes available. By using a [5′-32P]pNp as a donor and RNA as an acceptor, the product of the reaction is an RNA molecule one nucleotide longer, with a 3′-terminal phosphate and a 32P-phosphate in the last internucleotide linkage. This reaction is therefore analogous to the in vitro labelling of the 5′ termini of RNA chains with polynucleotide kinase and [γ-32P]ATP and can be used in situations where 5′ labelling is not possible. In addition, the ability to add various donors to an RNA molecule should allow the function of the 3′ terminus of the molecule to be investigated.

Community Structure and Collaborative Consumption: A Routine Activity Approach:

Abstract: More than a quarter of a century has passed since Hawley (1950) first presented his human ecological theory of community structure, a theory emphasizing the structure of sustenance activities. Yet we know of no effort to apply that theory to consumption even though it is clearly a human sustenance activity. We believe that Hawley's framework offers much more than an opportunity to translate old theories into new terms, since it also provides a means of thinking about consumer activities as they related to one another and to other activities in social life. This paper is concerned specifically with acts of collaborative consumpt ion , namely, those events in which one or more persons consume economic goods or services in the process of engaging in joint activities with one or more others.' For example, drinking beer with friends, eating meals with relatives, driving to visit someone or using a washing machine for family laundry are acts of collaborative consumption. Thus our present concern goes beyond the discrete preferences and resources of individual consumers. Rather, we take these considerations as given and proceed to examine how the structure of daily activities creates the circumstances in which collaborative consumption occurs, hence al-

Water resources and the land-water interface.

Abstract: Development and implementation of local and regional plans to control nonpoint sources of pollution from agricultural land are major mandates of section 208 of Public Law 92-500. Many planners tend to equate erosion control as measured by the universal soil loss equation with improvements in water quality. Others implement channel management practices which degrade rather than improve water quality and thereby decrease the effectiveness of other efforts to control nonpoint sources. Planners rarely recognize the importance of the land-water interface in regulating water quality in agricultural watersheds. More effective planning can result from the development of "best management systems" which incorporate theory from all relevant disciplines.

Spectroscopic Studies of Specifically Deuterium Labeled Membrane Systems. Nuclear Magnetic Resonance Investigation of the Effects of Cholesterol in Model Systems

Abstract: Deuterium nuclear magnetic resonance spectra of dimyristoylphosphatidylcholines specifically labeled in positions 2', 3', 4', 6', 8', 10', 12', and 14', of the 2 chain, of an N-deuteriomethylphosphatidylcholine, and of cholesterol-3alpha-d1, have been obtained by the Fourier transform method at 5.46 and 3.52 T on two "home-built" widebore superconducting magnet spectrometers, as a function of temperature and composition. Data on the specifically deuterium-labeled cholesterol molecule (in nonsonicated membrane systems) permits an estimate of the most probable angle of tilt of the sterol in the membrane, and evaluation of the order parameter (Salpha) describing rigid body motions in the bilayer. Segmental order parameters derived from the data presented allow calculation of individual chain segment projections onto the director axis and, consequently, estimation of effective chain length. It is shown that mathematical models which include chain tilt as well as those which neglect this type of rigid body motion give essentially identical results when applied to the dimyristoylphosphatidylcholine and dimyristoylphosphatidylcholine-cholesterol bilayer systems (in excess water, between 23 and 60 degrees C). Results of calculations of chain length and membrane thickness of a dimyristoylphosphatidylcholine-30 mol % cholesterol membrane system at 23 degrees C give excellent agreement when compared with recent high-resolution neutron diffraction data obtained on specifically deuterium labeled lecithin-cholesterol systems. No evidence for formation of lecithin-cholesterol complexes having lifetimes of approximately 30 ms has been found. Below the pure-lipid gel-liquid crystal phase transition temperature Tc but in the presence of cholesterol, we have obtained further evidence for 1-chain/2-chain nonequivalence. At 10 degrees C, the 2' segment of the 2 chain, but not the 2' segment of the 1 chain or the 3', 6', or 12' segments of the 2 chain, is broadened almost beyond detection. These results are in agreement with similar effects reported recently for the dipalmitoylphosphatidylcholine-cholesterol system and may indicate a bent configuration for the 2 chain, in the lecithin-cholesterol system. Further cooling below Tc results in loss of the 1-chain 2'-position signal intensity plus 2-chain 3', 6', and 12' signals simultaneously. The increase in length of the 2 chain of dimyristoylphosphatidylcholine upon addition of 30 mol % cholesterol of 23 degrees C is about 2.3 A. Addition of cholesterol to a choline-labeled lecithin results in complex behavior of the head group deuterium quadrupole splitting as a function of temperature, and cholesterol mole fraction. Above approximately 20 mol % cholesterol, the main effect is a decrease in quadrupole splitting as cholesterol content increases, the opposite effect to that observed with hydrocarbon chains.

Disk accretion by magnetic neutron stars.

Abstract: A model for disk accretion by a rotating magnetic neutron star is proposed which includes a detailed description of matter flow in the transition region between the disk and the magnetosphere. It is shown that the disk plasma cannot be completely screened from the stellar magnetic field and that the resulting magnetic coupling between the star and the disk exerts a significant torque on the star. On the assumption that the distortion of the residual stellar field lines threading the disk is limited by reconnection, the total accretion torque on the star is calculated. The calculated torque gives period changes in agreement with those observed in the pulsating X-ray sources and provides a natural explanation of why a fast rotator like Her X-1 has a spin-up rate much below the conventional estimate for slow rotators. It is shown that for such fast rotators, fluctuations in the mass-accretion rate can produce fluctuations in the accretion torque about 100 times larger. For sufficiently fast rotators or, equivalently, for sufficiently low accretion rates, the star experiences a braking torque even while accretion continues and without any mass ejection from its vicinity.

Antixenosis–A New Term Proposed to Define Painter's “Nonpreference” Modality of Resistance

Abstract: Much of the wide acceptance and popularity of Reginald Painter's classification of the mechanisms of plant resistance to insect pests stems not only from its simplicity and apparent generality, but also because it accurately describes insect and plant responses. Based on some of his own previous work (Painter 1936, 1941), Painter in his classical book “Insect Resistance in Crop Plants” (1951) proposed that plant resistance, as observed in the field, could be explained by three fundamental mechanisms which he named: (a) nonpreference, (b) antibiosis, and (c) tolerance. Painter and many subsequent workers have stressed the fact that these mechanisms are most frequently interrelated although they may also operate independently.

Subsynaptic Plate Perforations: Changes with Age and Experience in the Rat

Abstract: The relative frequency of appearance of discontinuities in the postsynaptic thickening, or perforations in the subsynaptic plate, increased with age and experience. Rats reared from weaning in complex or social environments had a significantly higher proportion of occipital cortical synapses with perforations than did rats reared in isolation. In addition, the relative frequency of these perforations more than tripled between 10 and 60 days of age. Shifts in the frequency of perforations can occur independently of changes in the size of synpases. This result suggests a new potential mechanism of synaptic plasticity.

Schema-Directed Processes in Language Comprehension

Abstract: This paper will attempt to develop the thesis that the knowledge a person already possesses has a potent influence on what he or she will learn and remember from exposure to discourse. It begins by outlining some assumptions about the characteristics of the structures in which existing knowledge is packaged. Next, based on these assumptions, it presents a speculative theoretical treatment of the processes involved in assimilating the information and ideas in discourse. This is the topic that will be given most attention in this paper. Data consistent with the theory will be summarized. It should be emphasized in advance, however, that the experiments to date show at most that the theoretical notions are interesting and plausible. The research has not advanced to the point where there is a firm basis for choosing between competing accounts. Finally, some observations will be made about the implications of this research for education.

Substantive Theory and Statistical Interaction: Five Models

Abstract: For a series of theoretical models involving two independent interval-scale variables acting together to produce a joint causal effect, different modes of analysis are described. In each case statistical interaction is involved, but the form of this interation differs with each model. Methods for deriving appropriate interaction terms are given. These models provide a flexibility for statistical analyses appropriate to a broader range of theories than can be treated well by conventional regression procedures. If, as seems likely, theoretical propositions are often stated in empirical research in a form appropriate to additive multiple regression, these methods suggest that such propositions might be reexamined and reformulated. It is possible that the methods have particular relevance for some aspects of functional, equilibrium, balance, and conflict theories.

Academic engaged time

Abstract: In issue 3.1 of the BJTE (January 1977) Ned Flanders discussed the question of knowledge about teacher effectiveness. He did this by examining what he saw to be the weaknesses of the analyses in the book by Rosenshine on the same subject. In the article which follows Rosenshine and Berliner take up the discussion of important teacher activities. In reply to Flanders Rosenshine writes: ’Ned has never forgiven me for an article I wrote in Phi Delta Kappan in 1970, and his attack in BJTE is his response to that article. Although the issue ‐‐ whether teacher “indirectness” is a positive significant correlate of student achievement gain and student attitudes ‐‐ was a burning issue in the early 1970s, it doesn't seem worth debating today. Much of my 1971 book is now out of date, and if I were ever to rewrite it, I'd do it a lot differently. The article which follows represents a summary of current thinking on teaching and the results of recent research?

Collective vs. Dyadic Representation in Congress

Abstract: Previous studies of legislative-constituency representation have focused almost exclusively on pairs of Congress members and their constituencies. It is possible, however, to think of representation collectively, i.e., to consider the extent to which Congress as an institution represents the American people. Our analysis delineates this concept of representation, analyzes its existence by use of probability theory and the Miller-Stokes data, and then considers the relationship between collective representation and electoral control. We conclude that citizens probably get better representation than is suggested by the Miller-Stokes analysis, that the amount of representation may be more a function of institutional arrangements than of electoral control, and that citizen indifference towards many aspects of legislative politics is quite reasonable, given the existence of collective representation.