Showing papers by "University of California, Santa Cruz published in 1988"
TL;DR: It is concluded that bafilomycin A1 is a valuable tool for distinguishing among the three different types of ATPases and represents the first relatively specific potent inhibitor of vacuolar ATPases.
Abstract: Various membrane ATPases have been tested for their sensitivity to bafilomycin A1, a macrolide antibiotic F1F0 ATPases from bacteria and mitochondria are not affected by this antibiotic In contrast, E1E2 ATPases--eg, the K+-dependent (Kdp) ATPase from Escherichia coli, the Na+,K+-ATPase from ox brain, and the Ca2+-ATPase from sarcoplasmic reticulum--are moderately sensitive to this inhibitor Finally, membrane ATPases from Neurospora vacuoles, chromaffin granules, and plant vacuoles are extremely sensitive From this we conclude that bafilomycin A1 is a valuable tool for distinguishing among the three different types of ATPases and represents the first relatively specific potent inhibitor of vacuolar ATPases
1,715 citations
TL;DR: This work presents one such algorithm that learns disjunctive Boolean functions, along with variants for learning other classes of Boolean functions.
Abstract: Valiant (1984) and others have studied the problem of learning various classes of Boolean functions from examples. Here we discuss incremental learning of these functions. We consider a setting in which the learner responds to each example according to a current hypothesis. Then the learner updates the hypothesis, if necessary, based on the correct classification of the example. One natural measure of the quality of learning in this setting is the number of mistakes the learner makes. For suitable classes of functions, learning algorithms are available that make a bounded number of mistakes, with the bound independent of the number of examples seen by the learner. We present one such algorithm that learns disjunctive Boolean functions, along with variants for learning other classes of Boolean functions. The basic method can be expressed as a linear-threshold algorithm. A primary advantage of this algorithm is that the number of mistakes grows only logarithmically with the number of irrelevant attributes in the examples. At the same time, the algorithm is computationally efficient in both time and space.
1,669 citations
01 Jan 1988
TL;DR: It is shown that if m O(W/ ∊ log N/∊) random examples can be loaded on a feedforward network of linear threshold functions with N nodes and W weights, so that at least a fraction 1 ∊/2 of the examples are correctly classified, then one has confidence approaching certainty that the network will correctly classify a fraction 2 ∊ of future test examples drawn from the same distribution.
Abstract: We address the question of when a network can be expected to generalize from m random training examples chosen from some arbitrary probability distribution, assuming that future test examples are drawn from the same distribution. Among our results are the following bounds on appropriate sample vs. network size. Assume 0 < e ≤ 1/8. We show that if m ≥ O(W/e log N/e) random examples can be loaded on a feedforward network of linear threshold functions with N nodes and W weights, so that at least a fraction 1 - e/2 of the examples are correctly classified, then one has confidence approaching certainty that the network will correctly classify a fraction 1 - e of future test examples drawn from the same distribution. Conversely, for fully-connected feedforward nets with one hidden layer, any learning algorithm using fewer than Ω(W/e) random training examples will, for some distributions of examples consistent with an appropriate weight choice, fail at least some fixed fraction of the time to find a weight choice that will correctly classify more than a 1 - e fraction of the future test examples.
1,649 citations
TL;DR: Diatom flocculation is a poorly understood source of marine snow of potential global significance and rates of snow production and breakdown are critical to predicting flux and to understanding biological community structure and transformations of matter and energy in the water column.
1,319 citations
01 Jun 1988
TL;DR: This paper discusses collision detection and response in general, presents two collision detection algorithms, describes modeling collisions of arbitrary bodies using springs, and presents an analytical collision response algorithm for articulated rigid bodies that conserves linear and angular momentum.
Abstract: When several objects are moved about by computer animation, there is the chance that they will interpenetrate. This is often an undesired state, particularly if the animation is seeking to model a realistic world. Two issues are involved: detecting that a collision has occurred, and responding to it. The former is fundamentally a kinematic problem, involving the positional relationship of objects in the world. The latter is a dynamic problem, in that it involves predicting behavior according to physical laws. This paper discusses collision detection and response in general, presents two collision detection algorithms, describes modeling collisions of arbitrary bodies using springs, and presents an analytical collision response algorithm for articulated rigid bodies that conserves linear and angular momentum.
672 citations
01 Apr 1988
TL;DR: The model indicates that generalist grazers, zooplankton that consume a broad size spectrum of prey (including pico-and nanoplankton), play a critical role in exporting particles, which could control the average, long-term exports from surface oceanic communities.
Abstract: The size distribution of pelagic producers and the size and trophic position of consumers determine the composition and magnitude of sinking fluxes from the surface communities in a simple model of oceanic food webs. Picoplankton, the dominant producers in the model, contribute little to the sinking material, due primarily to the large number of trophic steps between picoplankton and the consumers that produce the sinking particles. Net phytoplankton are important contributors to the sinking materials, despite accounting for a small fraction of the total primary production. These net phytoplankton, especially those capable of nitrogen fixation, also dominate the fraction of the new production that is exported on its first pass through the food chain. The sinking flux is strongly determined by the community structure of the consumers and varies by an order of magnitude for different food webs. The model indicates that generalist grazers, zooplankton that consume a broad size spectrum of prey (including pico-and nanoplankton), play a critical role in exporting particles. The role of generalists that occasionally form swarms, such as thaliaceans (salps and doliolids), can be particularly difficult to assess. Short-term studies probably miss the relatively infrequent population blooms of these grazers, events that could control the average, long-term exports from surface oceanic communities.
573 citations
TL;DR: In this article, it was shown that the requirement that the government's budget be balanced in present value terms is equivalent to the condition that government expenditures inclusive of interest, tax receipts and seignorage be cointegrated.
521 citations
TL;DR: In this paper, the authors expound the traditional Marxist theory of the contradiction between forces and relations of production, over-production of capital and economic crisis, and the process of crisis-induced restructuring of productive forces and production relations into more transparently social, hence potentially socialist, forms.
Abstract: Summary This article expounds the traditional Marxist theory of the contradiction between forces and relations of production, over‐production of capital and economic crisis, and the process of crisis‐induced restructuring of productive forces and production relations into more transparently social, hence potentially socialist, forms. This exposition provides a point of departure for an “ecological Marxist”; theory of the contradiction between capitalist production relations and forces and the conditions of production, under‐production of capital and economic crisis, and the process of crisis‐induced restructuring of production conditions and the social relations thereof also into more transparently social, hence potentially socialist, forms. In short, there may be not one but two paths to socialism in late capitalist society. While the two processes of capital over‐production and underproduction are by no means mutually exclusive, they may offset or compensate for one another in ways which create the appe...
517 citations
TL;DR: It is shown that the notion of inductive bias in concept learning can be quantified in a way that directly relates to learning performance in the framework recently introduced by Valiant.
496 citations
TL;DR: Copper titrations were conducted at sea with differential pulse anodic stripping voltammetry to examine the degree to which copper was associated with organic ligands as discussed by the authors, finding that approximately 50-70% of the total dissolved copper was in the organically complexed form.
Abstract: Copper titrations were conducted at sea with differential pulse anodic stripping voltammetry to examine the degree to which copper was associated with organic ligands. Greater than 99.7% of the total dissolved copper in surface waters of the central Northeast Pacific shallower than 200 m was estimated to be associated with strong organic complexes. Below 200 m, increasing proportions of inorganic or labile copper spccics were observed. At middepths (1,000 m), about 50-70% of the total dissolved copper was in the organically complexed form. Whereas total copper varies by a factor of only three from the surface to middepths (0.6-I .8 nM), copper complexation gives rise to extremely low cupric ion activities in surface waters ({Cu!‘} = 1.4 x lo-l4 M) and higher values at middepth ({Cuz-I} = lo- I1 M)-a variation of three orders of magnitude. Two classes of copperbinding ligands were found to be responsible for this complexation: an extremely strong ligand class [log K’cond (cu,j = 11.5 J at low concentrations (- 1.8 nM) -which dominated copper complexation in the surface waters and decreased with depth, and a weaker class of ligands [log K’cond(Cu3 = 8.51 at higher concentrations (8-10 nM) which was observed throughout the water column and showed no apparent structure in its vertical distribution. These findings have significant implications concerning the toxicity and bioavailability of copper in open ocean systems.
496 citations
TL;DR: In this paper, the consequences of extended spacetime supersymmetry for classical superstring vacua with four dimensions uncompactified were examined, and it was shown that the effective field theories for classical vacua of superstring theories have no continuous global symmetries.
TL;DR: The authors used chemical probes to investigate the possible interaction of the elongation factors EF-Tu and EF-G with ribosomal RNA in E. coli ribosomes, and observed EFG-dependent footprints in vitro and in vivo around position 1,067 in domain II of 23S rRNA, and in the loop around position 2,660 in domain VI.
Abstract: The elongation factors EF-Tu and EF-G interact with ribosomes during protein synthesis: EF-Tu presents incoming aminoacyl transfer RNA to the programmed ribosome as an EF-Tu-GTP-tRNA ternary complex and EF-G promotes translocation of peptidyl-tRNA and its associated messenger RNA from the A to the P site after peptidyl transfer. Both events are accompanied by ribosome-dependent GTP hydrolysis. Here we use chemical probes to investigate the possible interaction of these factors with ribosomal RNA in E. coli ribosomes. We observe EF-G-dependent footprints in vitro and in vivo around position 1,067 in domain II of 23S rRNA, and in the loop around position 2,660 in domain VI.EF-Tu gives an overlapping footprint in vitro at positions 2,655 and 2,661, but shows no effect at position 1,067. The 1,067 region is the site of interaction of the antibiotic thiostrepton, which prevents formation of the EF-G-GTP-ribosome complex and is a site for interaction with the GTPase-related protein L11 (ref. 3). The universally conserved loop in the 2,660 region is the site of attack by the RNA-directed cytotoxins alpha-sarcin and ricin, whose effects abolish translation and include the loss of elongation factor-dependent functions in eukaryotic ribosomes.
Journal Article•
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TL;DR: The applications of digital data compression and the major components of compression systems are described and data modeling is discussed, and the role of entropy and data statistics is examined.
Abstract: The applications of digital data compression and the major components of compression systems are described. Data modeling is discussed, and the role of entropy and data statistics is examined. Gray-scale image modeling is used to illustrate some of these mechanisms. The coding mechanisms are examined, and prefix codes are explained. Arithmetic coding is considered. >
TL;DR: An extended random medium is modeled by a set of 2-D thin Gaussian phase-changing screens with phase power spectral densities appropriate to the natural medium being modeled, showing that under weak scattering the small-scale Fresnel length structure of the medium dominates the intensity scattering pattern.
Abstract: An extended random medium is modeled by a set of 2-D thin Gaussian phase-changing screens with phase power spectral densities appropriate to the natural medium being modeled. Details of the algorithm and limitations on its application to experimental conditions are discussed, concentrating on power-law spectra describing refractive-index fluctuations of the neutral atmosphere. Inner and outer scale effects on intensity scintillation spectra and intensity variance are also included. Images of single realizations of the intensity field at the observing plane are presented, showing that under weak scattering the small-scale Fresnel length structure of the medium dominates the intensity scattering pattern. As the strength of scattering increases, caustics and interference fringes around focal regions begin to form. Finally, in still stronger scatter, the clustering of bright regions begins to reflect the large-scale structure of the medium. For plane waves incident on the medium, physically reasonable inner scales do not produce the large values of intensity variance observed in the focusing region during laser propagation experiments over kilometer paths in the atmosphere. Values as large as experimental observations have been produced in the simulations, but they require inner scales of the order of 10 cm. Inclusion of an outer scale depresses the low-frequency end of the intensity spectrum and reduces the maximum of the intensity variance. Increasing the steepness of the power law also slightly increases the maximum value of intensity variance.
TL;DR: The Q-Coder as mentioned in this paper is a new form of adaptive binary arithmetic coding, which is derived from the basic concepts introduced by Rissanen, Pasco, and Langdon, but extends the coding conventions to resolve a conflict between optimal software and hardware implementations.
Abstract: The Q-Coder is a new form of adaptive binary arithmetic coding. The binary arithmetic coding part of the technique is derived from the basic concepts introduced by Rissanen, Pasco, and Langdon, but extends the coding conventions to resolve a conflict between optimal software and hardware implementations. In addition, a robust form of probability estimation is used in which the probability estimate is derived solely from the interval renormalizations that are part of the arithmetic coding process. A brief tutorial of arithmetic coding concepts is presented, followed by a discussion of the compatible optimal hardware and software coding structures and the estimation of symbol probabilities from interval renormalization.
TL;DR: In this article, the authors present the basic argument and major results and lines of analysis of a doctoral dissertation on the constitution of a number of nations (much of Asia, Africa, and Latin America) as "Third World" or "underdeveloped", and their treatment as such thereafter (Escobar 1987).
Abstract: This article presents in a succinct manner the basic argument and the major results and lines of analysis of a doctoral dissertation on the constitution of a number of nations (much of Asia, Africa, and Latin America) as "Third World" or "underdeveloped," and their treatment as such thereafter (Escobar 1987). The study builds upon recent work in various fields on the dynamics of discourse and power in the representation of social reality, and examines (1) the conformation of a new mode of thinking about social and economic life in those countries in the early post-World War 11 period; (2) the anchoring of this new mode of thinking in Western economic practices; and (3) the institutional practices through which "development" functions, at the same time enacting the discourse and creating extended cultural and social relations. Some of these issues will be illustrated with the experience of one country, Colombia. Finally, some conclusions are offered in relation to anthropology.
TL;DR: In this paper, the authors derived a model for the three-dimensional folding of Escherichia coli 16 S ribosomal RNA, using interactive computer graphic methods, based on the secondary structure derived from comparative sequence analysis, and the threedimensional co-ordinates for the centers of mass of the 30 S subunit proteins, from footprinting and crosslinking studies.
TL;DR: There is definitive evidence that the vacuolar ATPase is closely related to the F0F1-type ATPases, and it is proposed that the two ATPases may have arisen from a common ancestor by the insertion or deletion of a large stretch of nonhomologous sequence near the amino-terminal end of the subunit.
TL;DR: In this paper, the weak mixing angle θ w is the same for continuously connected classical vacua of the heterotic string which have chiral fermions in their massless spectra.
TL;DR: Des simulations numeriques are realized pour determiner l'aimantation de sous-reseaux dans l'etat fondamental de l'antiferromagnetique a spin 1/2 sur le reseau carre avec des interactions de plus proches voisins.
Abstract: Avec la motivation d'une relation possible entre la supraconductivite dans les nouveaux oxydes supraconducteurs et le comportement magnetique de ces materiaux, on realise des simulations numeriques pour determiner l'aimantation de sous-reseaux dans l'etat fondamental de l'antiferromagnetique a spin 1/2 sur le reseau carre avec des interactions de plus proches voisins
12 Sep 1988
TL;DR: FXT is a software tool which implements inductive fault analysis for CMOS circuits and extracts a comprehensive list of circuit-level faults for any given CMOS circuit and ranks them according to their relative likelihood of occurrence.
Abstract: FXT is a software tool which implements inductive fault analysis for CMOS circuits. It extracts a comprehensive list of circuit-level faults for any given CMOS circuit and ranks them according to their relative likelihood of occurrence. Five commercial CMOS circuits are analyzed using FXT. Of the extracted faults, approximately 50% can be modeled by single-line stuck-at 0/1 fault model. Faults extracted from two circuits are simulated with the switch-level fault simulator FMOSSIM. The test set provided by the circuits' manufacturer, which detects 100% of the single-line stuck-at 0/1 faults, detected between 73% and 89% of the simulated faults. >
TL;DR: It is shown that EGF reinitiated ductal growth and morphogenesis in growth-static glands of ovariectomized mice using slow-release plastic implants, and must be considered a strong candidate for a naturally occurring mammary tissue mitogen.
TL;DR: The spatial-frequency selectivity of the luminance-facilitates-color interaction is much broader than facilitatory interactions in either the color-color or Luminance-luminance conditions, which is consistent with models that invoke inhibitory or more elaborate excitatory masking interactions.
Abstract: The contrast dependence of simultaneous masking has been measured using isochromatic yellow–black luminance sinusoids and isoluminant red–green chrominance gratings. Masking functions for all four combinations of chromatic and luminance masks and tests are reported. In the two same-on-same conditions (luminance mask/luminance test and chromatic mask/chromatic test) these functions (increment threshold contrast versus mask contrast) have the typical dipper shape and are almost identical when test and mask contrasts are normalized to the unmasked contrast thresholds. The contrast dependence of the luminance mask/color test and color mask/luminance test functions are quite different. The luminance mask/color test shows facilitation over a broad range of both subthreshold and suprathreshold contrasts of the luminance mask. In the color mask/luminance test condition facilitation is never observed, but at suprathreshold contrasts a 2-cycle/degree (c/deg) chromatic grating masks a 2-c/deg luminance grating as strongly as does a luminance mask. The luminance mask/chromatic test results are invariant over the 0.25–2-c/deg spatial-frequency range, whereas the robust masking of luminance by color at 2 c/deg diminishes at lower spatial frequencies. The spatial-frequency selectivity of the luminance-facilitates-color interaction is much broader than facilitatory interactions in either the color–color or luminance–luminance conditions. Possible mechanisms of color–luminance interactions are considered. The lack of facilitation in the color mask/luminance test condition precludes a simple pedestal interpretation of this masking interaction. The data are, however, consistent with models that invoke inhibitory or more elaborate excitatory masking interactions.
TL;DR: The assumption of interactive activation of specific connectionist models is shown to be both unnecessary and inconsistent with empirical results, and other important properties of connectionism are to be found in existing process models of pattern recognition.
TL;DR: A new technique for proving lower bounds in the synchronous model is presented, based on a string-producing mechanism from formal language theory, first introduced by Thue to study square-free words.
Abstract: The computational capabilities of a system of n indistinguishable (anonymous) processors arranged on a ring in the synchronous and asynchronous models of distributed computation are analyzed. A precise characterization of the functions that can be computed in this setting is given. It is shown that any of these functions can be computed in O(n2) messages in the asynchronous model. This is also proved to be a lower bound for such elementary functions as AND, SUM, and Orientation. In the synchronous model any computable function can be computed in O(n log n) messages. A ring can be oriented and start synchronized within the same bounds.The main contribution of this paper is a new technique for proving lower bounds in the synchronous model. With this technique tight lower bounds of t(n log n) (for particular n) are proved for XOR, SUM, Orientation, and Start Synchronization. The technique is based on a string-producing mechanism from formal language theory, first introduced by Thue to study square-free words. Two methods for generalizing the synchronous lower bounds to arbitrary ring sizes are presented.
TL;DR: The hypothesis that the vacuolar ATPase is related to F0F1 ATPases is strongly supported by the finding of considerable homology between the 67-kDa subunit of the Neurospora vacu polar ATPase and both the alpha and beta subunits of F0f1 ATPase.
TL;DR: This analysis shows that the traditional SSA fault model characterizes fewer than half of the faults extracted by FXT; graph-theoretic techniques provide little improvement in the percentage of realistic faults modeled.
Abstract: The inductive fault analysis (IFA) method is presented and a description is given of the CMOS fault extraction program FXT. The IFA philosophy is to consider the causes of faults (manufacturing defects) and then simulate these causes to find the faults that are likely to occur in a circuit. FXT automates IFA for a CMOS technology by generating a list of faults that are likely to occur in a CMOS circuit. The realistic faults generated by FXT are used to evaluate fault models, find the realistic fault coverage of test sets, and guide future testing research. How well various fault models characterize the realistic faults can be quantitatively measured because FXT's fault list includes the relative likelihood of occurrence (weight) of each extracted fault. The value of IFA and FXT is demonstrated by the analysis of five commercial CMOS circuits. This analysis shows that the traditional SSA fault model characterizes fewer than half of the faults extracted by FXT; graph-theoretic techniques provide little improvement in the percentage of realistic faults modeled. >
TL;DR: A numerical study of the motion of a long-chain macromolecule in a gel has shown unexpected features, and the application of a field appears to induce the chain to contract on itself.
Abstract: A numerical study of the motion of a long-chain macromolecule in a gel has shown unexpected features. The application of a field appears to induce the chain to contract on itself. This is followed by its "unwinding" into an extended configuration. For long chains, the mobility tends toward a constant, in accord with experiments. For the parameter range used, the observed molecular motion differs strongly from assumptions made in the present theory of electrophoresis.
University of California, Santa Cruz1, Institut Français2, Texas A&M University3, Columbia University4, Lille University of Science and Technology5, Pierre-and-Marie-Curie University6, Durham University7, University of South Alabama8, University of Miami9, Scripps Institution of Oceanography10, University of Sheffield11, Petro-Canada12, Bedford Institute of Oceanography13, Kyushu University14, Utsunomiya University15, Massachusetts Institute of Technology16
TL;DR: In this article, an accretionary prism consisting of imbricately thrusted Neogene hemipelagic sediments detached from little-deformed Oligocene to Campanian underthrust deposits by a decollement zone composed of lower Miocene to upper Oligian, scaly radiolarian claystone is described.
Abstract: Drilling near the deformation front of the northern Barbados Ridge cored an accretionary prism consisting of imbricately thrusted Neogene hemipelagic sediments detached from little-deformed Oligocene to Campanian underthrust deposits by a decollement zone composed of lower Miocene to upper Oligocene, scaly radiolarian claystone. Biostrati-graphically defined age inversions define thrust faults in the accretionary prism that correlate between sites and are apparent on the seismic reflection sections. Two sites located 12 and 17 km west of the deformation front document continuing deformation of the accreted sediments during their uplift. Deformational features include both large- and small-scale folding and continued thrust faulting with the development of stratal disruption, cataclastic shear zones, and the proliferation of scaly fabrics. These features, resembling structures of accretionary complexes exposed on land, have developed in sediments never buried more than 400 m and retaining 40% to 50% porosity. A single oceanic reference site, located 6 km east of the deformation front, shows incipient deformation at the stratigraphic level of the decollement and pore-water chemistry anomalies both at the decollement level and in a subjacent permeable sand interval. Pore-water chemistry data from all sites define two fluid realms: one characterized by methane and chloride anomalies and located within and below the decollement zone and a second marked solely by chloride anomalies and occurring within the accretionary prism. The thermogenic methane in the decollement zone requires fluid transport many tens of kilometers arcward of the deformation front along the shallowly inclined decollement surface, with minimal leakage into the overlying accretionary prism. Chloride anomalies along faults and a permeable sand layer in the underthrust sequence may be caused by membrane filtration or smectite dewatering at depth. Low matrix permeability requires that fluid flow along faults occurs through fracture permeability. Temperature and geochemical data suggest that episodic fluid flow occurs along faults, probably as a result of deformational pumping.