Showing papers by "California Institute of Technology published in 1985"
TL;DR: In this paper, the electron transfer reactions between ions and molecules in solution have been the subject of considerable experimental study during the past three decades, including charge transfer, photoelectric emission spectra, chemiluminescent electron transfer, and electron transfer through frozen media.
7,155 citations
TL;DR: Results of computer simulations of a network designed to solve a difficult but well-defined optimization problem-the Traveling-Salesman Problem-are presented and used to illustrate the computational power of the networks.
Abstract: Highly-interconnected networks of nonlinear analog neurons are shown to be extremely effective in computing. The networks can rapidly provide a collectively-computed solution (a digital output) to a problem on the basis of analog input information. The problems to be solved must be formulated in terms of desired optima, often subject to constraints. The general principles involved in constructing networks to solve specific problems are discussed. Results of computer simulations of a network designed to solve a difficult but well-defined optimization problem-the Traveling-Salesman Problem-are presented and used to illustrate the computational power of the networks. Good solutions to this problem are collectively computed within an elapsed time of only a few neural time constants. The effectiveness of the computation involves both the nonlinear analog response of the neurons and the large connectivity among them. Dedicated networks of biological or microelectronic neurons could provide the computational capabilities described for a wide class of problems having combinatorial complexity. The power and speed naturally displayed by such collective networks may contribute to the effectiveness of biological information processing.
5,328 citations
TL;DR: This study addresses the question of how simple networks of neuron-like elements can account for a variety of phenomena associated with this shift of selective visual attention and suggests a possible role for the extensive back-projection from the visual cortex to the LGN.
Abstract: Psychophysical and physiological evidence indicates that the visual system of primates and humans has evolved a specialized processing focus moving across the visual scene. This study addresses the question of how simple networks of neuron-like elements can account for a variety of phenomena associated with this shift of selective visual attention. Specifically, we propose the following: (1) A number of elementary features, such as color, orientation, direction of movement, disparity etc. are represented in parallel in different topographical maps, called the early representation. (2) There exists a selective mapping from the early topographic representation into a more central non-topographic representation, such that at any instant the central representation contains the properties of only a single location in the visual scene, the selected location. We suggest that this mapping is the principal expression of early selective visual attention. One function of selective attention is to fuse information from different maps into one coherent whole. (3) Certain selection rules determine which locations will be mapped into the central representation. The major rule, using the conspicuity of locations in the early representation, is implemented using a so-called Winner-Take-All network. Inhibiting the selected location in this network causes an automatic shift towards the next most conspicious location. Additional rules are proximity and similarity preferences. We discuss how these rules can be implemented in neuron-like networks and suggest a possible role for the extensive back-projection from the visual cortex to the LGN.
3,930 citations
TL;DR: The initial results show that remote, direct identification of surface materials on a picture-element basis can be accomplished by proper sampling of absorption features in the reflectance spectrum.
Abstract: Imaging spectrometry, a new technique for the remote sensing of the earth, is now technically feasible from aircraft and spacecraft. The initial results show that remote, direct identification of surface materials on a picture-element basis can be accomplished by proper sampling of absorption features in the reflectance spectrum. The airborne and spaceborne sensors are capable of acquiring images simultaneously in 100 to 200 contiguous spectral bands. The ability to acquire laboratory-like spectra remotely is a major advance in remote sensing capability. Concomitant advances in computer technology for the reduction and storage of such potentially massive data sets are at hand, and new analytic techniques are being developed to extract the full information content of the data. The emphasis on the deterministic approach to multispectral data analysis as opposed to the statistical approaches used in the past should stimulate the development of new digital image-processing methodologies.
1,750 citations
TL;DR: A clone encoding PrP 27-30, the major protein in purified preparations of scrapie agent, was selected from a scrapie-infected hamster brain cDNA library by oligonucleotide probes corresponding to the N terminus of the protein.
1,514 citations
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TL;DR: Cosmic Cube as discussed by the authors is a hardware simulation of a future VLSI implementation that will consist of single-chip nodes, which offers high degrees of concurrency in applications and suggests that future machines with thousands of nodes are both feasible and attractive.
Abstract: Sixty-four small computers are connected by a network of point-to-point communication channels in the plan of a binary 6-cube. This “Cosmic Cube” computer is a hardware simulation of a future VLSI implementation that will consist of single-chip nodes. The machine offers high degrees of concurrency in applications and suggests that future machines with thousands of nodes are both feasible and attractive.
1,232 citations
TL;DR: The historical development of the evidence of response selectivity for visual stimuli presented beyond the CRF is traced; the anatomical pathways that sub serve these far-reaching surround mechanisms are examined; and the possible relationships between these mechanisms and perception are explored.
Abstract: We perceive the visual world as a unitary whole, yet one of the guiding principles of nearly a half century of neurophysiological research since the early recordings by Hartline (1938) has been that the visual system consists of neurons that are driven by stimulation within small discrete portions of the total visual field. These classical receptive fields (CRFs) have been mapped with the excitatory responses evoked by a flashed or moving stimulus, usually a spot or bar of light. Most of the visual neurons, in turn, are organized in a series of maps of the visual field, at least 10 of which exist in the visual cortex in primates as well as additional topographic representations in the lateral geniculate body, pulvinar and optic tectum (Allman 1977, Newsome & Allman 1980, Allman & Kaas 1984). It has been widely assumed that perceptual functions that require the integration of inputs over large portions of the visual field must be either collective properties of arrays of neurons representing the visual field, or features of those neurons at the highest processing levels in the visual system, such as the cells in inferotemporal or posterior parietal cortex that typically possess very large receptive fields and do not appear to be organized in visuotopic maps. These assumptions have been based on the results of the many studies in which receptive fields were mapped with conventional stimuli, presented one at a time, against a featureless background. However, unlike the neurophysiologist's tangent screen, the natural visual scene is rich in features, and there is a growing body of evidence that in many visual neurons stimuli presented outside the CRF strongly and selectively influence neural responses to stimuli presented within the CRF. These results suggest obvious mechanisms for local-global comparisons within visuotopically organized structures. Such broad and specific surround mechanisms could participate in many functions that require the integration of inputs over wide regions of the visual space such as the perceptual constancies, the segregation of figure from ground, and depth perception through motion parallax. In the first section of this paper, we trace the historical development of the evidence of response selectivity for visual stimuli presented beyond the CRF; in the second, examine the anatomical pathways that sub serve these far-reaching surround mechanisms; and in the third, explore the possible relationships between these mechanisms and perception.
1,079 citations
TL;DR: The sequence of the entire RNA genome of the type flavivirus, yellow fever virus, has been obtained and implies that mature viral proteins are produced by posttranslational cleavage of a polyprotein precursor and has implications for flaviv virus RNA replication and for the evolutionary relation of this virus family to other RNA viruses.
Abstract: The sequence of the entire RNA genome of the type flavivirus, yellow fever virus, has been obtained. Inspection of this sequence reveals a single long open reading frame of 10,233 nucleotides, which could encode a polypeptide of 3411 amino acids. The structural proteins are found within the amino-terminal 780 residues of this polyprotein; the remainder of the open reading frame consists of nonstructural viral polypeptides. This genome organization implies that mature viral proteins are produced by posttranslational cleavage of a polyprotein precursor and has implications for flavivirus RNA replication and for the evolutionary relation of this virus family to other RNA viruses.
933 citations
TL;DR: In this paper, a linear correlation was established between the far-infrared flux measured by IRAS and the nonthermal radio flux density (at 1.4 GHz) from disks of spiral galaxies.
Abstract: A tight, linear correlation is established between the far-infrared flux measured by IRAS and the nonthermal radio flux density (at 1.4 GHz) from disks of spiral galaxies. This correlation defines a ratio of infrared to radio fluxes that is characteristic of star formation activity. Galaxies with nuclear starbursts seem to follow the correlation. If the far-infrared is reradiated luminosity from young massive stars, then the supernova remnants alone account for less than 10 percent of the radio emission. These results indicate a close coupling between dust heating and cosmic-ray generation and confinement in a wide range of conditions.
915 citations
TL;DR: In this paper, the authors consider a market in which one firm is the current incumbent, while the remaining firms are challengers, and derive the equivalent of the Schumpeterian process of creative destruction.
Abstract: The theoretical literature on innovation has been concerned with a single innovation produced by a number of identical agents. By contrast, we consider a market in which one firm is the current incumbent, while the remaining firms are challengers. Moreover, we consider a sequence of innovations, so that success does not imply that the successful firm reaps monopoly profits forever after, but only until the next, better innovation is developed. We begin with a fully optimizing behavioral model and derive the equivalent of the Schumpeterian “process of creative destruction.” That is, a firm enjoys temporary monopoly power but is soon overthrown by a more inventive challenger.
The essential point to grasp is that in dealing with capitalism we are dealing with an evolutionary process…The fundamental impulse that sets and keeps the capitalist engine in motion comes from the new consumers' goods, the new methods of production or transportation, the new markets, the new forms of industrial organization that capitalist enterprise creates [Schumpeter, 1942, pp. 82–83].
787 citations
TL;DR: In this paper, the total gravity field due to interior density contrasts and dynamic boundary topography predicts the longest-wavelength components of the geoid remarkably well, and neglecting dynamic surface deformation leads to geoid anomalies of opposite sign to those observed.
Abstract: Density contrasts in the lower mantle, inferred using seismic tomography, drive viscous flow; this results in kilometres of dynamically maintained topography at the core–mantle boundary and at the Earth's surface. The total gravity field due to interior density contrasts and dynamic boundary topography predicts the longest-wavelength components of the geoid remarkably well. Neglecting dynamic surface deformation leads to geoid anomalies of opposite sign to those observed.
TL;DR: In this paper, a simple, fully quantum mechanical model for electron transfer using a one mode treatment which incorporates this coupling is studied, and the limits of the moderate and the high friction are analyzed in detail.
Abstract: In biological and chemical electron transfer, a nuclear reaction coordinate is coupled to other nuclear and/or ‘‘solvent’’ coordinates. This coupling, or friction, if strong enough, may substantially slow down motion along the reaction coordinate, and thus vitiate the assumption of electron transfer being nonadiabatic with respect to the nuclei. Here, a simple, fully quantum mechanical model for electron transfer using a one mode treatment which incorporates this coupling is studied. Path integral methods are used to study the dependence of the reaction rate on friction, and the limits of the moderate and the high friction are analyzed in detail. The first limit will prevail if the reaction coordinate is, e.g., an underdamped nuclear vibration, whereas the second limit will prevail if it corresponds to a slow or diffusive degree of freedom. In the high‐friction limit, the reaction rate is explicitly shown to vary between the nonadiabatic and adiabatic expressions as the tunneling matrix element and/or the friction are varied. Starting from a path integral expression for the time evolution of the reduced density matrix for the electron and reaction coordinate, a Fokker–Planck equation is obtained which reduces in the high‐friction limit to a Smoluchowski equation similar to one solved by Zusman.
TL;DR: The true receptive field of more than 90% of neurons in the middle temporal visual area (MT) extends well beyond the classical receptive field (crf), as mapped with conventional bar or spot stimuli, and includes a surrounding region that is 50 to 100 times the area of the crf.
Abstract: The true receptive field of more than 90% of neurons in the middle temporal visual area (MT) extends well beyond the classical receptive field (crf), as mapped with conventional bar or spot stimuli, and includes a surrounding region that is 50 to 100 times the area of the crf. These extensive surrounds are demonstrated by simultaneously stimulating the crf and the surround with moving stimuli. The surrounds commonly have directional and velocity-selective influences that are antagonistic to the response from the crf. The crfs of MT neurons are organized in a topographic representation of the visual field. Thus MT neurons are embedded in an orderly visuotopic array, but are capable of integrating local stimulus conditions within a global context. The extensive surrounds of MT neurons may be involved in figure–ground discrimination, preattentive vision, perceptual constancies, and depth perception through motion cues.
TL;DR: In this paper, the quadrature-phase amplitudes and two-mode squeezed states were introduced for analyzing two-photon devices, in which photons in the output modes are created or destroyed two at a time.
Abstract: This paper introduces a new formalism for analyzing two-photon devices (e.g., parametric amplifiers and phase-conjugate mirrors), in which photons in the output modes are created or destroyed two at a time. The key property of a two-photon device is that it excites pairs of output modes independently. Thus our new formalism deals with two modes at a time; a continuum multimode description can be built by integrating over independently excited pairs of modes. For a pair of modes at frequencies \ensuremath{\Omega}\ifmmode\pm\else\textpm\fi{}\ensuremath{\epsilon}, we define (i) quadrature-phase amplitudes, which are complex-amplitude operators for modulation at frequency \ensuremath{\epsilon} of waves ``cos[\ensuremath{\Omega}(t-x/c)]'' and ``sin[\ensuremath{\Omega}(t-x/c)]'' and (ii) two-mode squeezed states, which are the output states of an ideal two-photon device. The quadrature-phase amplitudes and the two-mode squeezed states serve as the building blocks for our formalism; their properties and their physical interpretation are extensively investigated.
TL;DR: The behavior of the glacier in surge has many remarkable features, which can provide clues to a detailed theory of the surging process and is akin to a proposed mechanism of overthrust faulting.
Abstract: The hundredfold speedup in glacier motion in a surge of the kind the kind that took place in Variegated Glacier in 1982-1983 is caused by the buildup of high water pressure in the basal passageway system, which is made possible by a fundamental and pervasive change in the geometry and water-transport characteristics of this system. The behavior of the glacier in surge has many remarkable features, which can provide clues to a detailed theory of the surging process. The surge mechanism is akin to a proposed mechanism of overthrust faulting.
TL;DR: The problem of public goods provision has been central to many areas of economics, and public goods serve as a classic model of market failure and exist as the foundation for many modern theories of government as mentioned in this paper.
TL;DR: It is shown that the conformal diffeomorphisms, which remain after imposing certain covariant gauge conditions for the general coordinate invariance, can be used to gauge away twice as many modes as there are gauge parameters.
Abstract: We discuss the spontaneous compactification of chiral N = 2 ten-dimensional supergravity from ten to five dimensions on S/sup 5/. Harmonic analysis on S/sup 5/ is used to compute the complete mass spectrum. Our results indicate that scalars and spinors in different SO(6) multiplets have different masses, even within the ''massless'' supermultiplet. We show that the conformal diffeomorphisms, which remain after imposing certain covariant gauge conditions for the general coordinate invariance, can be used to gauge away twice as many modes as there are gauge parameters. A doubleton multiplet of pure gauge modes is identified, and all modes in the massless supermultiplet lie at the beginning of infinite towers of modes.
TL;DR: Numerical and experimental results presented show that the approach is capable of introducing accuracy and robustness to optical processing while maintaining the traditional advantages of optics, namely, parallelism and massive interconnection capability.
Abstract: Optical implementation of content addressable associative memory based on the Hopfield model for neural networks and on the addition of nonlinear iterative feedback to a vector–matrix multiplier is described. Numerical and experimental results presented show that the approach is capable of introducing accuracy and robustness to optical processing while maintaining the traditional advantages of optics, namely, parallelism and massive interconnection capability. Moreover a potentially useful link between neural processing and optics that can be of interest in pattern recognition and machine vision is established.
TL;DR: The physical limitations due to quantum mechanics on the functioning of computers are analyzed in this article, where the physical limitations of quantum mechanics are discussed and the physical limits of quantum computing are analyzed.
Abstract: The physical limitations, due to quantum mechanics, on the functioning of computers are analyzed.
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26 Apr 1985TL;DR: This book gives the reader access to the mathematical techniques involved and goes on to apply fixed point theorems to proving the existence of equilibria for economics and for co-operative and noncooperative games.
Abstract: Preface 1. Introduction: models and mathematics 2. Convexity 3. Simplexes 4. Sperner's lemma 5. The Knaster-Kuratowski-Mazurkiewicz lemma 6. Brouwer's fixed point theorem 7. Maximization of binary relations 8. Variational inequalities, price equilibrium, and complementarity 9. Some interconnections 10. What good is a completely labelled subsimplex? 11. Continuity of correspondences 12. The maximum theorem 13. Approximation of correspondence 14. Selection theorems for correspondences 15. Fixed point theorems for correspondences 16. Sets with convex sections and a minimax theorem 17. The Fan-Browder theorem 18. Equilibrium of excess demand correspondences 19. Nash equilibrium of games and abstract economies 20. Walrasian equilibrium of an economy 21. More interconnections 22. The Knaster-Kuratowski-Mazurkiewicz-Shapley lemma 23. Cooperative equilibria of games References Index.
TL;DR: It is concluded that the six reading frames of human mitochondrial DNA encode components of the respiratory-chain NADH dehydrogenase.
Abstract: The products of six unidentified reading frames of human mitochondrial DNA are precipitated from a mitochondrial lysate by antibodies against highly purified native beef heart NADH-ubiqutnone oxidoreductase (complex I). These products are enriched greatly in a human submitochondrial fraction enriched in NADH-Q1 and NADH-K3Fe(CN)6 oxidoreductase activities. We conclude that the six reading frames encode components of the respiratory-chain NADH dehydrogenase.
TL;DR: In this paper, the authors discuss the possible gaugings, abelian and non-abelian, of a class of d = 5 Yang-Mills/Einstein supergravity theories for which the manifold of scalar fields is a symmetric coset space.
TL;DR: It is demonstrated that V2 cells projecting to two of its major target areas, MT and V4, are arranged in stripe-like clusters which are largely segregated from one another and which are closely related to the pattern of CO stripes.
Abstract: V2 is a visual area of the macaque monkey which is at the second level in a recently proposed hierarchy of cortical visual areas1. Histochemical staining for cytochrome oxidase (CO) in V2 reveals a pattern of alternate thick and thin CO-rich stripes separated by CO-sparse interstripes2,3. These subregions receive distinct inputs from neurones in CO-rich and CO-sparse zones arrayed within the superficial layers of V1 (refs 4,5). Are output projections from V2 to higher visual areas also segregated? Using an anatomical double-label paradigm, we have now demonstrated that V2 cells projecting to two of its major target areas, MT and V4 (refs 6, 7), are arranged in stripe-like clusters which are largely segregated from one another and which are closely related to the pattern of CO stripes. Concomitant electrophysiological recordings from V2 indicate that groups of cells having similar receptive field properties are clustered within the subregions defined by these anatomical techniques.
TL;DR: In this article, the authors compare alternative audit policies to the standard random audit policy and show that audit cutoff rules are the least-cost policies which induce truthful reporting of income for both lump-sum and proportional taxation.
TL;DR: In this paper, the mathematical foundation for the two-mode formalism is provided, and the fundamental unitary operators of the formalism are described and their properties examined; particular attention is paid to the twomode squeeze operator.
Abstract: This paper provides the mathematical foundation for the two-mode formalism introduced in the preceding paper. A vector notation is introduced; it allows two-mode properties to be written as compactly as the comparable properties for a single mode. The fundamental unitary operators of the formalism are described and their properties are examined; particular attention is paid to the two-mode squeeze operator. Special quantum states associated with the formalism are considered, with emphasis on the two-mode squeezed states.
TL;DR: In this paper, the authors considered the compactification of four dimensions on the manifold K 3 without requiring that the equations of motion be satisfied, leading to a large number of anomaly-free chiral supersymmetric six-dimensional theories.
TL;DR: In this article, a critical comparison and synthesis of data from the four Pioneer Venus Probes, the Pioneer Venus Orbiter, and the Venera 10, 12, and 13 landers is derived.