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Showing papers by "University of California, Santa Cruz published in 1987"


Book ChapterDOI
TL;DR: A manifesto for Cyborgs: Science, technology, and socialist feminism in the 1980s as mentioned in this paper is a seminal work in Australian Feminist Studies: Vol. 2, No. 4, pp. 1-42.
Abstract: (1987). A manifesto for Cyborgs: Science, technology, and socialist feminism in the 1980s. Australian Feminist Studies: Vol. 2, No. 4, pp. 1-42.

1,327 citations


Journal ArticleDOI
04 Jun 1987-Nature
TL;DR: Chemical footprinting shows that several classes of antibiotics protect concise sets of highly conserved nucleotides in 16S ribosomal RNA when bound to ribosomes, having strong implications for the mechanism of action of these antibiotics and for the assignment of functions to specific structural features of 16S rRNA.
Abstract: Chemical footprinting shows that several classes of antibiotics (streptomycin, tetracycline, spectinomycin, edeine, hygromycin and the neomycins) protect concise sets of highly conserved nucleotides in 16S ribosomal RNA when bound to ribosomes These findings have strong implications for the mechanism of action of these antibiotics and for the assignment of functions to specific structural features of 16S rRNA

1,116 citations


Journal ArticleDOI
TL;DR: It is shown that a polynomial learning algorithm, as defined by Valiant (1984), is obtained whenever there exists aPolynomial-time method of producing, for any sequence of observations, a nearly minimum hypothesis that is consistent with these observations.

972 citations


Journal ArticleDOI
TL;DR: The concept of an ɛ-net of a set of points for an abstract set of ranges is introduced and sufficient conditions that a random sample is an Â-net with any desired probability are given.
Abstract: We demonstrate the existence of data structures for half-space and simplex range queries on finite point sets ind-dimensional space,dÂ?2, with linear storage andO(nÂ?) query time, $$\alpha = \frac{{d(d - 1)}}{{d(d - 1) + 1}} + \gamma for all \gamma > 0$$ . These bounds are better than those previously published for alldÂ?2. Based on ideas due to Vapnik and Chervonenkis, we introduce the concept of an Â?-net of a set of points for an abstract set of ranges and give sufficient conditions that a random sample is an Â?-net with any desired probability. Using these results, we demonstrate how random samples can be used to build a partition-tree structure that achieves the above query time.

799 citations


Journal ArticleDOI
TL;DR: In this article, the vertical and horizontal distributions of dissolved and suspended particulate Fe and Mn, and vertical fluxes of these metals (obtained with sediment traps) were determined throughout the Pacific Ocean.

523 citations


MonographDOI
01 Oct 1987
TL;DR: The work of Kolmogorov, Arnold, and Moser and its application to Laplace's question of stability of the solar system remains one of the goals of the exposition.
Abstract: Preface to the Second Edition. Since the first edition of this book appeared in 1967, there has been a great deal of activity in the field of symplectic geometry and Hamiltonian systems. In addition to the recent textbooks of Arnold, Arnold-Avez, Godbillon, Guillemin-Sternberg, Siegel-Moser, and Souriau, there have been many research articles published. Two good collections are "Symposia Mathematica," vol. XIV, and "Geometrie Symplectique el Physique Mathematique," CNRS, Colloque Internationaux, no. 237. There are also important survey articles, such as Weinstein [1977b]. The text and bibliography contain many of the important new references we are aware of. We have continued to find the classic works, especially Whittaker [1959], invaluable. The basic audience for the book remains the same: mathematicians, physicists, and engineers interested in geometrical methods in mechanics, assuming a background in calculus, linear algebra, some classical analysis, and point set topology. We include most of the basic results in manifold theory, as well as some key facts from point set topology and Lie group theory. Other things used without proof are clearly noted. We have updated the material on symmetry groups and qualitative theory, added new sections on the rigid body, topology and mechanics, and quantization, and other topics, and have made numerous corrections and additions. In fact, some of the results in this edition are new. We have made two major changes in notation: we now use f^* for pull-back (the first edition used f[sub]*), in accordance with standard usage, and have adopted the "Bourbaki" convention for wedge product. The latter eliminates many annoying factors of 2. A. N. Kolmogorov's address at the 1954 International Congress of Mathematicians marked an important historical point in the development of the theory, and is reproduced as an appendix. The work of Kolmogorov, Arnold, and Moser and its application to Laplace's question of stability of the solar system remains one of the goals of the exposition. For complete details of all tbe theorems needed in this direction, outside references will have to be consulted, such as Siegel-Moser [1971] and Moser [1973a]. We are pleased to acknowledge valuable assistance from Paul Chernoff, Wlodek Tulczyjew, Morris Hirsh, Alan Weinstein, and our invaluable assistant authors, Richard Cushman and Tudor Ratiu, who all contributed some of their original material for incorporation into the text. Also, we are grateful to Ethan Akin, Kentaro Mikami, Judy Arms, Harold Naparst, Michael Buchner, Ed Nelson, Robert Cahn, Sheldon Newhouse, Emil Chorosoff, George Oster, Andre Deprit, Jean-Paul Penot, Bob Devaney, Joel Robbin, Hans Duistermaat, Clark Robinson, John Guckenheimer, David Rod, Martin Gutzwiller, William Satzer, Richard Hansen, Dieter Schmidt, Morris Kirsch, Mike Shub, Michael Hoffman, Steve Smale, Andrei Iacob, Rich Spencer, Robert Jantzen, Mike Spivak, Therese Langer, Dan Sunday, Ken Meyer, Floris Takens, [and] Randy Wohl for contributions, remarks, and corrections which we have included in this edition. Further, we express our gratitude to Chris Shaw, who made exceptional efforts to transfom our sketches into the graphics which illustrate the text, to Peter Coha for his assistance in organizing the Museum and Bibliography, and to Ruthie Cephas, Jody Hilbun, Marnie McElhiney, Ruth (Bionic Fingers) Suzuki, and Ikuko Workman for their superb typing job. Theoretical mechanics is an ever-expanding subject. We will appreciate comments from readers regarding new results and shortcomings in this edition. RALPH ABRAHAM, JERROLD E. MARSDEN

469 citations


Journal ArticleDOI
17 Jul 1987-Science
TL;DR: Under the conditions of these experiments, TGF-beta displayed many of the characteristics expected of a physiologically active growth-regulatory molecule and the inhibitory effect was fully reversible.
Abstract: Transforming growth factor-beta (TGF-beta) can stimulate or inhibit growth of cells in vitro, as well as induce the transformed phenotype. Although widely distributed in animal tissue, the effects of TGF-beta in vivo are largely unknown, and a physiological role for the peptide hormone has not been demonstrated. The effect of TGF-beta on developing epithelial tissue in situ was studied by using slow-release plastic pellets containing TGF-beta to treat developing mouse mammary gland. Powerful inhibition of mammary growth and morphogenesis was observed. This growth-inhibited mammary tissue was histologically normal, and the inhibitory effect was fully reversible. Under the conditions of these experiments, TGF-beta displayed many of the characteristics expected of a physiologically active growth-regulatory molecule.

428 citations


Journal ArticleDOI
TL;DR: A new role is proposed for phospholipase A 2 in protecting membranes from oxidative injury by reducing and detoxifying fatty acid hydroperoxides in membranes.

427 citations


Journal ArticleDOI
01 May 1987-Nature
Abstract: The eastern half of China is dominated by the North China Block (NCB) and South China Block (SCB), separated by a complex fold system that trends roughly east-west. Interpretation of the geology of this fold belt has led to a variety of estimates of the age of amalgamation of these two blocks1–7. Palaeomagnetic results are few and have also been subject to conflicting interpretations8–11. Here we present our own palaeomagnetic results for late Permian rocks for both the SCB and NCB and summarize other relevant palaeomagnetic data. By reinterpreting the polarity given in some previous studies we are able to synthesize the results for the widespread Emeishan basalts of the SCB and to suggest a new model for the collision and relative rotation of the two blocks.

373 citations


Journal ArticleDOI
TL;DR: In this article, a social psychological analysis is presented that emphasizes the biases introduced by the "triple jeopardy" these new workers often endure: negative racial stereotypes, the solo role, and the token role.
Abstract: Recent gains in black occupational status, importantly aided by such programs as affirmative action, have created new interracial job situations throughout American society. This paper reviews the problems that arise at the recruitment, entry, and promotional stages for black Americans. The problems arise from two interrelated sources: the structure of the situations themselves and the operation of antiblack prejudice in both its traditional and modern forms. A social psychological analysis is advanced that emphasizes the biases introduced by the “triple jeopardy” these new workers often endure: (1) negative racial stereotypes, (2) the solo role—when the worker is the only black in the work group, and (3) the token role—when new black workers are viewed by white co-workers as incompetent simply because they received their jobs through affirmative action. The barriers to black inclusion created by this triple jeopardy are discussed at several levels: biased and stressful recruitment practices; assumed dissimilarity and exaggerated expectations on entry; and later polarized, biased evaluations of performance. These processes often deny the new black employee needed realistic feedback and informal social support. The results, then, can involve not only biased evaluations but actual decrements in black job performance. The analysis is illustrated by several suggested micro-remedies. But these micro-remedies alone are unlikely to be sufficient unless administered in the larger context of structural, macro-remedies. Two illustrative macro-remedies are advanced, both of which aim to prevent solo situations and enlarge the black pool of qualified workers.

343 citations


Journal ArticleDOI
TL;DR: In this article, a model for treating the transfer of angular momentum within a gaseous differentially rotating disc subject to gravitational instability is discussed in terms of an effective kinematic viscosity.
Abstract: A model for treating the transfer of angular momentum within a gaseous differentially rotating disc subject to gravitational instability is discussed in terms of an effective kinematic viscosity. It is assumed that even when matter in the disc is subject to self-gravitation, the instability does not necessarily lead directly to condensation of parts of the disc into self-gravitating bodies. Conditions under which the present model permits a similarity solution are discussed, and it is shown that the general solution tends to the similarity solution at large times.

Journal ArticleDOI
TL;DR: Using dimethyl sulfate and kethoxal, antibiotic-ribosome complexes are probed, and sites of interaction of chloramphenicol, erythromycin, carbomycin, vernamycin B and viomycin with 23S rRNA are identified, inferring that peptidyl transferase is inhibited as a result of binding antibiotics proximal to A-2451, whereas antibiotics bound proximalto A-2058 interfere with growth of the nascent poly

Journal ArticleDOI
24 Jul 1987-Science
TL;DR: A theoretical description of the shape of a random object is presented that is analytically simple in application but quantitatively accurate, and can be extended to yield an approximate, but extremely accurate, expression for the probability distribution function directly.
Abstract: A theoretical description of the shape of a random object is presented that is analytically simple in application but quantitatively accurate. The asymmetry of the object is characterized in terms of the invariants of a tensor, analogous to the moment-of-inertia tensor, whose eigenvalues are the squares of the principal radii of gyration. The complications accompanying ensemble averaging because of random processes are greatly reduced when the object is embedded in a space of high dimensionality, d. Exact analytical expressions are presented in the case of infinite spatial dimensions, and a procedure for developing an expansion in powers of l/d is discussed for linear chain and ring-type random walks. The first two terms in such an expansion lead to results for various shape parameters that agree remarkably well with those calculated by computer simulation. The method can be extended to yield an approximate, but extremely accurate, expression for the probability distribution function directly. The theoretical approach discussed here can, in principle, be used to describe the shape of other random fractal objects as well.

Journal ArticleDOI
TL;DR: In this article, the authors used a two-layer model for stratified oceanic euphotic zones, in which nutrient-limited phytoplankton populations overlie light-limited populations.
Abstract: Profiles of dissolved and particulate 234Th were determined at the VERTEX 2 and 3 stations off Manzanillo, Mexico, and at the VERTEX 4 station about 900 km north of Hawaii. By modeling the disequilibria between 234Th and 238U in the dissolved and particulate form, estimates of scavenging rates for Th from the dissolved to particulate phases, particle residence times, and the flux of Th via particle removal can be obtained. 234Th: 238U activity ratio profiles indicate that the euphotic zone can be separated into two layers: An upper oligotrophic layer characterized by low new production values, low net scavenging, and long dissolved 234Th residence times; and a subsurface eutrophic layer with higher new production values, more intense scavenging, and shorter dissolved 234Th residence times. New production, rather than total primary production may determine net scavenging rates of reactive elements from oceanic surface waters. These results contribute to the emerging descriptions of the layered structure of oligotrophic euphotic zones and support the notion that this may be a general and ubiquitous feature of global stratified oligotrophic regimes. These layered systems can be structured not only in biological and nutrient parameters, but also in terms of the rates of chemical scavenging and elemental transport. The layered structure of biological processes within stratified oceanic euphotic zones has been recognized for quite some time. Since Steele and Yentsch’s (1960) paper on the vertical distribution of chlorophyll, the subsurface chlorophyll maximum has received a great deal of attention and is now a well known oceanographic feature. Dugdale (1967) proposed a two-layer model, for oceanic euphotic zones, in which nutrient-limited phytoplankton populations overlie light-limited populations. Venrick (1982) reported two distinct floral assemblages associated with each of these layers, which also seem to be differentiated ecologically in terms of competition and predation. Herbland et al. (1985) showed a strong stratification in size classes of photosynthetic organisms (especially < 1 pm) of the equatorial Atlantic, with the major shift in size spectra occurring at or near the base of the mixed layer. Recently, the presence of stratified systems in meso- and oligotrophic regimes has been further interpreted in terms of the concepts of Dugdale and Goering (1967) and Eppley and Peterson (1979) regarding “new” and “regenerated” pro

Journal Article
TL;DR: It is concluded that estrogen, perhaps acting on nonepithelial target cells and probably in conjunction with extramammary factors, directly stimulates mammary ductal growth.
Abstract: 17β-Estradiol is a recognized mammary mitogen, but uncertainty exists as to whether its normal action is mediated exclusively through the pituitary or whether in addition direct effects of estradiol on mammary tissue may play a role in mammary growth and development. To further investigate the action of estradiol on the developing mammary ductal system of young mice, implants of biocompatible ethylene vinyl acetate copolymer, which deliver small amounts of steroid locally to the target tissue, were implanted into the mammary glands of castrated females in which the ductal system was static and end buds had regressed. Within 3 days end buds appeared in the vicinity of the implants but not elsewhere in the gland and not in other glands of the animal, indicating direct stimulation. The new end buds were histologically normal, displaying a visible cap (stem) cell layer with high levels of DNA synthesis. The antiestrogen keoxifene, which competes with estrogen for its receptors, inhibited end bud formation in the estradiol-implanted gland but failed to inhibit growth when implanted into the glands of intact, 5-week-old females. Time course and dose-response studies of estradiol stimulation were carried out in ovariectomized animals and were consistent with a direct action for estrogen. Steroid autoradiography revealed estrogen receptors in the lumenal cells of the end bud, in ductal epithelium, and in stroma adjacent to ducts, but none was detected in the rapidly proliferating cap cells. We conclude that estrogen, perhaps acting on nonepithelial target cells and probably in conjunction with extrammary factors, directly stimulates mammary ductal growth.

Journal ArticleDOI
TL;DR: In this article, an unusually low delta N-15 found in early to middle Cretaceous beds rich in marine organic matter from two separate eastern Atlantic Ocean basins is reported, which constitutes unambiguous evidence that the N contained in these strata is the end result of biogeochemical processes that differed substantially from those that operated on the contained in intervening organic carbonpoor strata and younger marine sediments.

Journal ArticleDOI
TL;DR: This paper examined the effect of two linguistic factors on children's understanding of idioms and found that younger children (kindergarten and first graders) understood idioms that were syntactically frozen better than they did idioms which can be seen in a variety of syntactic forms (e.g. turn back the clock) in short story contexts.
Abstract: This study examined the effect of two linguistic factors on children's understanding of idioms. Kindergarten, first, third and fourth graders listened to idiomatic expressions either alone or at the end of short story contexts. Their task was to explain verbally the intended meanings of these idioms and then to choose the correct idiomatic interpretations of these phrases. The results showed that in the presence of supporting context younger children (kindergarten and first graders) understood idioms that were syntactically frozen (e.g. turn back the clock) better than they did idioms which can be seen in a variety of syntactic forms (e.g. lay down the law). Older children (third and fourth graders) comprehended both kinds of idiom equally well. Moreover, with context, children at all grade levels were better at explaining the figurative meanings of idioms whose literal and idiomatic interpretations were closely related (e.g. hold your tongues) than they were at explaining idioms whose literal and figurative meanings were not closely related (e.g. beat around the bush). Without context there were few significant differences noted in children's understanding of the different kinds of idiom. The significance of these findings for developmental models of idiom comprehension is discussed.

Journal ArticleDOI
13 Jul 1987
TL;DR: It is shown that heuristic methods for learning from larger scenes are likely to give an accurate hypothesis if they produce a simple hypothesis consistent with a large enough random sample and that this class of concepts is polynomiaIIy learnable from random examples in the sense of Valiant.
Abstract: We study the problem of learning conjunctive concepts from examples on structural domains like the blocks world. nus class of concepts is formally defined and it is shown that even for samples in which each example (positive or negative) is a two-object scene it is NP-complete to determine if there is any concept in this class that is consistent with the sample. We demonstrate how this result affects the feasibility of Mitchell's version space approach and how it shows that it is unlikely that this class of concepts is polynomiaIIy learnable from random examples in the sense of Valiant. On the other hand, we show that this class is polynomially learnable if we allow a larger hypothesis space. This result holds for any fixed number of objects per scene, but the algorithm is not practical unless the number of objects per scene is very small. We also show that heuristic methods for learning from larger scenes are likely to give an accurate hypothesis if they produce a simple hypothesis consistent with a large enough random sample.

Journal ArticleDOI
01 May 1987-Geology
TL;DR: In this article, detailed analyses of cogenetic methane-rich and water-rich fluid inclusions in syntectonic quartz veins indicate that fluid pressures dropped by 20% to 45% during crystal growth, and probably represent the local effect of fluid escaping to shallow levels in the subduction complex during melange deformation, possibly along an interconnected fracture network.
Abstract: Sandstone and chert boudins that have syntectonic extensional veins are dominant structural elements in melanges of the Kodiak accretionary complex, Alaska. Detailed analyses of cogenetic methane-rich and water-rich fluid inclusions in syntectonic quartz veins indicate that fluid pressures dropped by 20% to 45% during crystal growth. This drop occurred faster than uplift of the rock and probably represents the local effect of fluid escaping to shallow levels in the subduction complex during melange deformation, possibly along an interconnected fracture network. An important implication of channelized fracture flow to higher levels in a subduction complex is that fluids may transport heat and solutes, thereby generating thermal and chemical anomalies along shallow faults.

Journal ArticleDOI
TL;DR: In this article, the field theoretic equation of motion of string is interpreted as the exact renormalization group equation, and the generators of string gauge invariance are the redundant operators of the RG; gauge equivalence is related to universality.

Journal ArticleDOI
01 Nov 1987-Geology
TL;DR: In this article, the authors show that sediment accreted at subduction zones undergo stratal disruption and form a type of melange, and the thickness of the disrupted zones grows with progressive deformation.
Abstract: Sediments accreted at subduction zones undergo stratal disruption and form a type of melange. The thickness of the disrupted zones grows with progressive deformation. This suggests that initial fault surfaces are abandoned and deformation propagates into adjacent undeformed sediment. Factors causing the abandonment of fault surfaces during continuing deformation include (1) strengthening owing to porosity loss during consolidation, (2) localized drops in fluid pressure on fault surfaces that act as dewaterinig conduits, and (3) reorientation of fault surfaces. The disruptive processes occurring in accretionary prisms result principally from the deformation of a consolidating sediment mass.

Journal ArticleDOI
TL;DR: There is evidence that dynamics offers hope for more realistic, natural, and automatic motion control, particularly in such complex articulated bodies as humans and other animals.
Abstract: A major problem in computer animation is creating motion that appears natural and realistic, particularly in such complex articulated bodies as humans and other animals. At present, truly lifelike motion is produced mainly by copying recorded images, a tedious and lengthy process that requires considerable external equipment. An alternative is the use of dynamic analysis to predict realistic motion. Using dynamic motion control, bodies are treated as masses acting under the influence of external and internal forces and torques. Dynamic control is advantageous because motion is naturally restricted to physically realizable patterns, and many types of motion can be predicted automatically. Use of dynamics is computationally expensive and specifying controlling forces and torques can be difficult. However, there is evidence that dynamics offers hope for more realistic, natural, and automatic motion control. Because such motion simulates real world conditions, an animation system using dynamic analysis is also a useful tool in such related fields as robotics and biomechanics.

Journal ArticleDOI
TL;DR: The dominant structures of the Kodiak Formation are interpreted as developing during underthrusting, underplating, and intra-wedge shortening during latest Cretaceous time within an accretionary wedge as mentioned in this paper.
Abstract: The Kodiak Formation, composed of coherent Maastrichtian turbidites, is a slate belt whose dominant structures developed during underplating to an accretionary wedge in the latest Cretaceous. It consists of about 80% coherent landward-dipping thrust packets; zones of disrupted sandstone associated with a scaly argillite matrix constitute the remainder. About half of these disrupted sandstone zones are related to pre-accretion deformation, and the rest formed along late-stage, strike-slip faults that postdate development of slaty cleavage. The formation is divided into three structural belts. The landward and seaward belts include steeply dipping structures, and the central belt contains shallowly dipping structures and rocks that have experienced the highest strain. The central belt probably acted as a low-angle, southeast-verging, floor thrust zone beneath the landward belt. The structural history of the Kodiak Formation includes (1) early soft-sediment disruption; (2) tectonic stratal disruption; (3) thrust faulting, slaty cleavage (S 1 ) development, and folding (F 1 ); (4) intrusion of granodioritic plutons, dikes, and sills and associated normal faulting; (5) development of crenulations (F 2 ) and crenulation cleavage (S 2 ); (6) thrust faulting; and (7) development of right-lateral, strike-slip faults. Event 3 produced the dominant northwest-dipping structural grain and caused the greatest amount of shortening; the timing of event 7 relative to events 5 and 6 is not certain. The dominant structures of the Kodiak Formation are interpreted as developing during underthrusting, underplating, and intra-wedge shortening during latest Cretaceous time within an accretionary wedge. The maximum time from deposition to emplacement was about 12 m.y., and the timing is constrained by the maximum depositional age (74 m.y.) and the age of plutonic rocks (62 m.y.) that crosscut the dominant fabric. Pre-cleavage zones of stratal disruption reflect deformation on the lower plate during underthrusting. Slaty cleavage, thrusts, and F 1 folds developed during underplating that also resulted in the formation of duplexes. Crenulations are probably related to post-underplating subhorizontal shortening of sediments within the accretionary wedge. Syn-deformation dynamic recrystallization of quartz, minimum syn-accretion metamorphic temperatures between 205 and 250 °C, and pressures of at least 2.65 kb recorded during the earliest stages of deformation suggest underplating at >10 km.

Journal ArticleDOI
TL;DR: The cytotoxic extract of Psammaplysilla sp. collected from Tonga contains monobromo tyrosine derivatives, 3-bromo-4-hydroxyphenylacetonitrile (1), which is known and psammaplin A (2) which is the first disulfide to be isolated from a sponge.

Journal ArticleDOI
TL;DR: The deduced amino acid sequence of mPL-I is highly homologous to the known members of the PRL family in the mouse, and hybridization analysis indicates that the mouse genome contains several m PL-I genes.
Abstract: The mouse midpregnancy lactogen or placental lactogen I (mPL-I) is encoded by a 1.0-kilobase mRNA that appears transiently during gestation, with maximal amounts accumulating in the placenta at day 10 of pregnancy. Several cDNA clones for mPL-I have been isolated from a lambda gt11 expression library constructed from day 10-placental RNA. The cDNA sequence indicates that mPL-I is synthesized as a 224 amino acid precursor, and is secreted as a 194 amino acid glycosylated hormone. The deduced amino acid sequence of mPL-I is highly homologous to the known members of the PRL family in the mouse, and hybridization analysis indicates that the mouse genome contains several mPL-I genes. Introduction of the mPL-I cDNA in an expression vector into cultured mouse cells results in the synthesis and secretion of glycosylated mPL-I protein that is recognized by anti-mPL-I antiserum and is biologically active.

Proceedings ArticleDOI
12 Oct 1987
TL;DR: A primary advantage of this on-line learning algorithm is that the number of mistakes that it makes is relatively little affected by the presence of large numbers of irrelevant attributes in the examples.
Abstract: Valiant and others have studied the problem of learning various classes of Boolean functions from examples. Here we discuss on-line learning of these functions. In on-line learning, 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 the on-line setting is the number of mistakes the learner makes. For suitable classes of functions, on-line 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, which learns disjunctive Boolean functions, and variants of the algorithm for learning other classes of Boolean functions. The algorithm can be expressed as a linear-threshold algorithm. A primary advantage of this algorithm is that the number of mistakes that it makes is relatively little affected by the presence of large numbers of irrelevant attributes in the examples; we show that the number of mistakes grows only logarithmically with the number of irrelevant attributes. At the same time, the algorithm is computationaUy time and space efficient.

Journal ArticleDOI
TL;DR: The high incidence of toxicity in antarctic sponge indicates that the current hypothesis suggesting a simple inverse relationship between toxicity and latitude in marine sponges is invalid, and there was little correspondence between the energetic composition or spicule contents of the spongees and feeding patterns (electivity indices) of sponge-eating predators.
Abstract: The biochemical and energetic composition, spicule content, and toxicity of benthic sponges was investigated in McMurdo Sound, Antarctica from October through December 1984. The predominant organic constituent of sponges was soluble and insoluble protein. Levels of total protein ranged from 17.0 to 55.9% dr. wt. Levels of lipid and carbohydrate were low, ranging from 2.1 to 9.6 and 0.6 to 3.5% dr. wt, respectively. Levels of ash were high and variable (32 t0 79% dr. wt), reflecting species-specific differences in spicule contents. Calculated energy contents of sponges were low, with a mean of 9.8±3.5 kJ g-1 dr. wt; ranging from 5.1 kJ g-1 dr. wt in Sphaerotylus antarcticus to 17.4 kJ g-1 dr. wt in Dendrilla membranosa. Insoluble protein accounted for the greatest contribution to the energetic composition of the sponges, while lipid and carbohydrate combined contributed to less than 25% of the overall energy. Normalized spicule volumes of sponges ranged from 0.15 to 0.38 cm3 g-1 dr. wt. Ichthyotoxicity assays indicated that 9 (56%) of 16 antarctic sponge species were toxic. The most highly toxic species were Mycale acerata and Leucetta leptorhapsis. The high incidence of toxicity in antarctic sponges indicates that the current hypothesis suggesting a simple inverse relationship between toxicity and latitude in marine sponges is invalid. There was little correspondence between the energetic composition or spicule contents of the sponges and feeding patterns (electivity indices) of sponge-eating predators. Although the asteroid Perknaster fuscus antarcticus specializes on the highly toxic, fast-growing M. acerata, most antarctic sponge-eating predators appear to be generalists which feed on the more abundant, non- to mildly-toxic, sponge species. This feeding strategy is based on exploitation of low energy, sedentary prey, which require a minimal energy output to harvest.

Journal ArticleDOI
TL;DR: In this article, the relevance of heavy quark fusion processes for production of both neutral and charged Higgs bosons was examined, and it was shown that gg fusion is generally larger than t t fusion for the neutral Higgs and even dominates WW/ZZ fusion in the region m H 0 ≤ 1 TeV for top masses above m t = 150 GeV.

Journal ArticleDOI
Abstract: Arenal volcano in Costa Rica has been erupting nearly continuously, but at a diminishing rate, since 1968, producing approximately 0.35 km3 of lavas and tephras that have shown consistent variations in chemistry and mineralogy. From the beginning of the eruption in July 1968 to early 1970 (stage 1, vol.=0.12 km3) tephras and lavas became richer in Ca, Mg, Ni, Cr, Fe, Ti, V, and Sc and poorer in Al2O3 and SiO2. Concentrations of incompatible trace elements (including Sr) decreased by 5%–20%. Phenocryst contents increased 20–50 vol%. During stage 2 (1970–1973, vol. = 0.13 km3) concentrations of compatible trace elements rose, and concentrations of incompatible trace elements either remained constant or also rose. Al2O3 contents decreased by 1 wt%. Phenocryst content increased slightly, principally due to increased orthopyroxene. During stage 3 (mid-1974 to the present, vol.= 0.10 km3) concentrations of SiO2 increased by 1 wt%, compatible trace elements decreased slightly, and incompatible trace element concentrations increased by 5% to 10%. Although crystals increased in size during stage 3, their overall abundance stayed roughly constant. Our modeling suggests that early stage-1 magmas were produced by boundary layer fractionation under high-p H2O conditions of an unseen basaltic andesitic magma that intruded into the Arenal system after approximately 500 B.P. Changes in composition during stage 2 resulted from mixing of this more mafic original magma with new magma that had a similar SiO2 content, but higher compatible and incompatible element concentrations. The changes during stage 3 resulted from continued influx of the same magma plus crystal removal. We conclude that the eruption proceeded in the following way. Before 1968 zoned stage-1 magma resided in the deep crust below Arenal. A new magma intruded into this chamber in July 1968 causing ejection of the stage-1 magmas. The intruding magma mixed with mafic portions of the original chamber producing the mixed lavas of stage 2. Continued mixing plus crystal fractionation along the chamber and conduit walls produced stage-3 lavas. The time scales of crustal level magmatic processes at Arenal range 100–103 years, which are 3–6 orders of magnitude shorter than those of larger, more silicic systems.

Journal ArticleDOI
TL;DR: More automic methods will allow the production of sophisticated animation with less user effort, including dynamic analysis, path planning and collision avoidance, stimulus-response control, and learning algorithms.
Abstract: Motion control for computer animation is a rich area for new research. The trend toward greater complexity in animation makes the development of more convenient and automatic methods of motion control important. Most commonly used motion control methods, such as keyframing and scripts, require a great deal of user effort to design acceptable animations. More automic methods will allow the production of sophisticated animation with less user effort. These methods include dynamic analysis, path planning and collision avoidance, stimulus-response control, and learning algorithms.