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Showing papers by "University of Illinois at Urbana–Champaign published in 1977"


Journal ArticleDOI
TL;DR: An analysis of an asynchronous phase-coded spread-spectrum multiple-access communication system reveals which code parameters have the greatest impact on communication performance and provides analytical tools for use in preliminary system design.
Abstract: An analysis of an asynchronous phase-coded spread-spectrum multiple-access communication system is presented. The results of this analysis reveal which code parameters have the greatest impact on communication performance and provide analytical tools for use in preliminary system design. Emphasis is placed on average performance rather than worst-case performance and on code parameters which can be computed easily.

1,723 citations


Journal ArticleDOI
19 Aug 1977-Science
TL;DR: The data support the proposition that the latency of P300 corresponds to stimulus evaluation time and is independent of response selection.
Abstract: A technique for measuring the latency of the P300 component of event-related brain potentials on individual trials is described. Choice reaction times and the latency of the P300 were compared under speed-maximizing and under accuracy-mazimising instructions. The choice stimuli required different levels of semantic categorization. The data support the proposition that the latency of P300 corresponds to stimulus evaluation time and is independent of response selection.

1,671 citations


Journal ArticleDOI
TL;DR: A priori probability and sequential structure appear to be independent determinants of the P300 complex, which was assessed to determine the waveform of event-related potentials elicited by task-relevant stimuli.
Abstract: Two factors are known to determine the waveform of event-related potentials (ERP) elicited by task-relevant stimuli: the a priori probability of the stimuli and the sequence of immediately preceding stimuli. The relative contribution of these factors to the ERP waveform was assessed at nine levels of a priori probability (from .10 to .90). Random sequences of high (1500 Hz) and low (1000 Hz) tones were presented to 10 male subjects at each level of probability, both when the events were task-relevant and when the subjects were performing an alternate task to which the tones were irrelevant. The EEG was recorded from five midline electrode sites referred to linked mastoids. The amplitude of the P300 and Slow Wave components was inversely proportional to the a priori probability of task-relevant events. At every level of a priori probability, the magnitude of the P300 complex (N200-P300-Slow Wave) was diminished when the eliciting tone repeated the preceding tone, and was enhanced when it was preceded by the other tone. Thus, a priori probability and sequential structure appear to be independent determinants of the P300 complex.

1,216 citations




Journal ArticleDOI
TL;DR: The presented algorithms use the “divide and conquer” technique and recursively apply a merge procedure for two nonintersecting convex hulls to ensure optimal time complexity within a multiplicative constant.
Abstract: The convex hulls of sets of n points in two and three dimensions can be determined with O(n log n) operations. The presented algorithms use the “divide and conquer” technique and recursively apply a merge procedure for two nonintersecting convex hulls. Since any convex hull algorithm requires at least O(n log n) operations, the time complexity of the proposed algorithms is optimal within a multiplicative constant.

731 citations


Journal ArticleDOI
TL;DR: The ultimate goal is to correlate the biological properties of these peptides with their effects on the physical properties of membranes and to rationalize these events in terms of lipid-peptide interactions.
Abstract: The general mechanism for the antibiotic activities of the polymyxins and octapeptins has been elucidated by research using a broad range of experimental techniques. However, this phenomenon has not been described in detailed molecular terms, and this must be one of the major goals for future research in this area. Since 1947, when polymyxin was first isolated, there have been tremendous advances in our knowledge of membrane structure. The application of biophysical technology such as NMR, ESR, fluorescence spectroscopy, differential scanning calorimetry, and electron microscopy has been particularly valuable for studying model and biological membrane structures. It is these techniques which will provide a detailed molecular mechanism for the effects of these peptide antibiotics on membrane structure. In addition, the large number of antibiotic derivatives available should be exploited more extensively for structure-function correlations. The ultimate goal is to correlate the biological properties of these peptides with their effects on the physical properties of membranes and to rationalize these events in terms of lipid-peptide interactions.

724 citations


Book
01 Jan 1977
TL;DR: In this paper, the authors introduce the concepts of chemical Bonding Theories and Chemical Equilibrium, Chemical Thermodynamics, and Chemical Intermolecular Forces, Liquids, and Solids.
Abstract: 1. Introduction: Matter and Measurement. 2. Atoms, Molecules, and Ions. 3. Stoichiometry: Calculations with Chemical Formulas and Equations. 4. Aqueous Reactions and Solution Stoichiometry. 5. Thermochemistry. 6. Electronic Structure of Atoms. 7. Periodic Properties of the Elements. 8. Basic Concepts of Chemical Bonding. 9. Molecular Geometry and Bonding Theories. 10. Gases. 11. Intermolecular Forces, Liquids, and Solids. 12. Modern Materials. 13. Properties of Solutions. 14. Chemical Kinetics. 15. Chemical Equilibrium. 16. Acid-Base Equilibria. 17. Additional Aspects of Equilibria. 18. Chemistry of the Environment. 19. Chemical Thermodynamics. 20. Electrochemistry. 21. Nuclear Chemistry. 22. Chemistry of the Nonmetals. 23. Metals and Metallurgy. 24. Chemistry of Coordination Compounds. 25. The Chemistry of Life: Organic and Biological Chemistry.

634 citations


Journal ArticleDOI
TL;DR: In this article, the EulerLagrange equations for the stat ionary points of an energy integral which has an intrinsic definition on maps between two Riemannian manifolds are studied.
Abstract: where ~ is a smooth positive function satisfying the ellipticity condition o(Q) + 2~'(Q)q > 0, V denotes the gradient, and [Vs[2 = ~ = 1 ]Vskl 2. This type of system arises as the EulerLagrange equations for the stat ionary points of an energy integral which has an intrinsic definition on maps between two Riemannian manifolds; the equations are therefore of geometric interest. However, the method of proof also applies to the equations of non-linear Hodge theory, which have been studied by L. M. and R. B. Sibner 19]. These are systems of equations for a closed p-form so, deo = 0 and

591 citations


Journal ArticleDOI
TL;DR: In this article, it is shown that the relationship between time compressibility and effective stress compressibility holds true at any time effective stress, and void ratio during consolidation for a variety of natural soils, including highly sensitive clays, organic silts and peats, are in the range of 0.025 to 0.10.
Abstract: For any natural soil a unique relationship exists between secondary compression index C sub a and compression index C sub c. It is postulated that the relation between time compressibility and effective stress compressibility holds true at any time effective stress, and void ratio during consolidation. The observed values of C sub a/C sub c for a variety of natural soils, including highly sensitive clays, organic silts, and peats, are in the range of 0.025 to 0.10. The shape of the settlement curve in the secondary range can be predicted from the shape of the void ratio-logarithm of effective stress curve and the relationship between C sub a and C sub c. The predicted results are completely consistent with laboratory observations and with the existing field case records. The magnitude of C sub a/C sub c can be used to predict the shape of the volume change-logarithm of time curve in the transition from primary to secondary. The procedure provides a quantitative explanation for the observed shapes of the settlement curve. /Author/

468 citations


Journal ArticleDOI
TL;DR: The results with known mixtures of bacteria suggest that hydrogenase-forming, sulfate-reducing bacteria could be active in some methanogenic ecosystems that are low in sulfate, and it is suggested that lack of availability of H(2) for growth of methanogens is a major factor in suppression of meetinghanogenesis by sulfate in natural ecosystems.
Abstract: In the analysis of an ethanol-CO2 enrichment of bacteria from an anaerobic sewage digestor, a strain tentatively identified as Desulfovibrio vulgaris and an H2-utilizing methanogen resembling Methanobacterium formicicum were isolated, and they were shown to represent a synergistic association of two bacterial species similar to that previously found between S organism and Methanobacterium strain MOH isolated from Methanobacillus omelianskii. In lowsulfate media, the desulfovibrio produced acetate and H2 from ethanol and acetate, H2, and, presumably, CO2 from lactate; but growth was slight and little of the energy source was catabolized unless the organism was combined with an H2-utilizing methanogenic bacterium. The type strains of D. vulgaris and Desulfovibrio desulfuricans carried out the same type of synergistic growth with methanogens. In mixtures of desulfovibrio and strain MOH growing on ethanol, lactate, or pyruvate, diminution of methane produced was stoichiometric with the moles of sulfate added, and the desulfovibrios grew better with sulfate addition. The energetics of the synergistic associations and of the competition between the methanogenic system and sulfate-reducing system as sinks for electrons generated in the oxidation of organic materials such as ethanol, lactate, and acetate are discussed. It is suggested that lack of availability of H2 for growth of methanogens is a major factor in suppression of methanogenesis by sulfate in natural ecosystems. The results with these known mixtures of bacteria suggest that hydrogenase-forming, sulfate-reducing bacteria could be active in some methanogenic ecosystems that are low in sulfate.

Journal ArticleDOI
01 Mar 1977-Icarus
TL;DR: In this paper, it was suggested that the explosion of a Type II supernova triggered the collapse of a nearby interstellar cloud and led to the formation of the solar system, and the abundances resulting from nuclear processing of the supernova ejecta were presented.

Journal ArticleDOI
23 Dec 1977-Science
TL;DR: This study showed a peak enchancement of learning in children after being given a dose of 0.3 milligram per kilogram of body weight, and a decrement in learning in those given larger doses; social behavior showed the most improvement in children given 1.0 milligrams per kilograms.
Abstract: Methylphenidate (Ritalin) is widely prescribed for hyperkinetic children. This study showed a peak enchancement of learning in children after being given a dose of 0.3 milligram per kilogram of body weight, and a decrement in learning in those given larger doses; social behavior showed the most improvement in children given 1.0 milligram per kilogram. These results had been hypothesized from theoretical dose-response curves which indicate different target behaviors would improve at different doses.

Journal ArticleDOI
TL;DR: In this article, a relativistic quantum many-body theory is applied to the study of high-density matter, where baryons are described as interacting with each other via massive scalar and massive vector meson exchange.

Journal ArticleDOI
TL;DR: The core of a market in indivisible goods can be defined in terms of strong domination or weak domination as mentioned in this paper, and it is shown that there are always stable points in the core, and a characterization is obtained.

Journal ArticleDOI
TL;DR: It is concluded that the P350 component is enhanced whenever the eliciting stimulus is both rare and in some sense relevant to the subject's task and the degree of enhancement is greatest when the rare--relevant tone is loud.

Journal ArticleDOI
TL;DR: In this article, a singular perturbation approach is used to unify a class of classical and recent results on high-gain systems and to show their relationships with multivariable transmission zero analysis, cheap control problems, and sliding mode in variable structure systems.
Abstract: In this paper a singular perturbation approach is used to unify a class of classical and recent results on high-gain systems and to show their relationships with multivariable transmission zero analysis, cheap control problems, and sliding mode in variable structure systems. A new pole placement method and a decomposition of near optimal high-gain regulator problems are presented.

Journal ArticleDOI
TL;DR: Comparative analysis of methanogens to constitute a distinct phylogenetic group containing two major divisions, and these organisms appear to be only distantly related to typical bacteria.
Abstract: The 16S ribosomal RNAs from 10 species of methanogenic bacteria have been characterized in terms of the oligonucleotides produced by T(1) RNase digestion. Comparative analysis of these data reveals the methanogens to constitute a distinct phylogenetic group containing two major divisions. These organisms appear to be only distantly related to typical bacteria.

Journal ArticleDOI
TL;DR: This study centers on three sources of reproductive failure: failure of pod initiation, failure of fruit maturation, and failure to donate pollen, and focuses on intraspecific comparisons.
Abstract: A major feature of floral display in many species is the aggregation of individual flowers into inflorescences. Inflorescences containing different numbers of flowers are likely to be differentially successful as pollen donors and receivers, and thus inflorescence size may influence the fitness of the plant on which an inflorescence is borne. We begin with the premise that inflorescence size is fundamentally an evolved trait and attempt to show or suggest some of the selection pressures and environmental limitations that may influence inflorescence size. In particular, this study centers on three sources of reproductive failure: failure of pod initiation, failure of fruit maturation, and failure to donate pollen. We emphasize intraspecific comparisons, in view of our interest in possible adaptive consequences. Our interest in the question of the evolution of inflorescence (umbel) size in Asclepias was sparked by the general observation that the number of fruits matured per inflorescence was commonly far smaller than the number of flowers in the inflorescence, and often much smaller than the number of young pods initiated (see also Woodson, 1941; Stevens, 1945; Moore, 1946, 1947; Sparrow and Pearson, 1948; Stebbins, 1951). We then asked what might be the adaptive value of producing so many flowers with such a low probability of producing seeds.


Journal ArticleDOI
TL;DR: From the analysis of these spectra, the excitation spectrum was resolved into the 1La and 1La excitation bands, which can also be applied to the resolution of the emission spectrum in cases of dual emission.
Abstract: — The fluorescence excitation spectrum and the excitation polarization spectrum of indole in propylene glycol were measured at — 58°C, after selecting by optical filters the emission originating from the 1La electronic level From the analysis of these spectra, the excitation spectrum was resolved into the 1La and 1La excitation bands A similar resolution of the excitation spectrum of tryptophan is given This method can also be applied to the resolution of the emission spectrum in cases of dual emission

Journal ArticleDOI
TL;DR: It is argued on the basis of differences between their respective translation mechanisms that the two lines do represent separate phylogenetic trees in the sense that each line of descent independently evolved to a level of organization that could be called procaryotic.
Abstract: A central evolutionary question is whether the eucaryotic cytoplasm represents a line of descent that is separate from the typical bacterial line. It is argued on the basis of differences between their respective translation mechanisms that the two lines do represent separate phylogenetic trees in the sense that each line of descent independently evolved to a level of organization that could be called procaryotic. The two lines of descent, nevertheless shared a common ancestor, that was far simpler than the procaryote. This primitive entity is called a progenote, to recognize the possibility that it had not yet completed evolving the link between genotype and phenotype. This concept changes considerably the view one takes toward cellular evolution.

Journal ArticleDOI
TL;DR: In this paper, the authors examined the process of escalation over three points in time and under four experimental conditions, and found that personal responsibility, efficacy of resources, and time were the independent variables, and commitment of resources to a course of action was the dependent variable.
Abstract: Previous research has shown that individuals are most likely to escalate the amount of resources committed to a course of action when they have been personally responsible for negative consequences. The present study examined the process of escalation over three points in time and under four experimental conditions. A 2 X 2 X 3 factorial experiment was conducted in which personal responsibility, efficacy of resources, and time were the independent variables, and commitment of resources to a course of action was the dependent variable. The results replicated the escalation effect over an immediate time period, but showed that investment of resources in a course of action was not stable over time. Although there were immediate effects of personal responsibility and efficacy of resources upon escalation behavior, these two variables interacted with the time factor.

Journal ArticleDOI
TL;DR: The results indicate that neurons in both regions show auditory-visual interactions and that at least some of these interactions are due to convergence at the cortical cell.

Journal ArticleDOI
TL;DR: An analysis of the code sequence parameters that are most important to the communication performance of an asynchronous phase-coded spread-spectrum multiple-access communication system is presented.
Abstract: An analysis of the code sequence parameters that are most important to the communication performance of an asynchronous phase-coded spread-spectrum multiple-access communication system is presented. Previously known bounds and computational techniques for such parameters are surveyed. Some new results on mean-square correlation are included.


Journal ArticleDOI
TL;DR: Results suggest sex differences in the afferent inputs to neurons in the dorsomedial preoptic area which may be related to functional sexual dimorphism in physiology and behavior.

Journal ArticleDOI
TL;DR: The individual resonance Raman spectra of the PM568 and M412 forms of light-adapted purple membrane from Halobacterium halobium have been measured and indicate that the retinal chromophore is linked to the purple membrane protein via a protonated and unprotonated Schiff base.
Abstract: The individual resonance Raman spectra of the PM568 and M412 forms of light-adapted purple membrane from Halobacterium halobium have been measured using the newly developed flow technique. For comparison purposes, the Raman spectra of the model chromophores, all-trans- and 13-cis retinal n-butylamine, both as protonated and unprotonated Schiff bases, have also been obtained. In agreement with previous work, the Raman data indicate that the retinal chromophore is linked to the purple membrane protein via a protonated. Schiff base in the case of the PM568 and an unprotonated Schiff base for the M412 form. The basic mechanism for color regulation in both forms appears to be electron delocalization. The spectral features of the two forms are different from each other and different from the model compound spectra.

Book ChapterDOI
TL;DR: A general statement of the purpose and character of land suitability analysis, a taxonomy of existing methods for identifying homogeneous areas and rating them as to suitability for specific uses, and a comparative evaluation of these methods are developed.
Abstract: Land resource inventories to determine land suitabilities have become a standard part of planning analysis at many scales. Any attempt to review, compare, evaluate, or improve upon the myriad of case studies, many only partially documented and in limited circulation, suffers from the lack of reference to a common framework. This article develops a general statement of the purpose and character of land suitability analysis, a taxonomy of existing methods for identifying homogeneous areas and rating them as to suitability for specific uses, and a comparative evaluation of these methods.

Journal ArticleDOI
TL;DR: In this paper, the relative contribution of self-monitoring, criterion-setting, self-evaluation, and self-reinforcement components in the Kanfer self-regulation model were examined in a simple learning task.