Showing papers by "University of California, Santa Cruz published in 1976"

Hierarchical geometric models for visible surface algorithms

Abstract: The geometric structure inherent in the definition of the shapes of three-dimensional objects and environments is used not just to define their relative motion and placement, but also to assist in solving many other problems of systems for producing pictures by computer. By using an extension of traditional structure information, or a geometric hierarchy, five significant improvements to current techniques are possible. First, the range of complexity of an environment is greatly increased while the visible complexity of any given scene is kept within a fixed upper limit. Second, a meaningful way is provided to vary the amount of detail presented in a scene. Third, “clipping” becomes a very fast logarithmic search for the resolvable parts of the environment within the field of view. Fourth, frame to frame coherence and clipping define a graphical “working set,” or fraction of the total structure that should be present in primary store for immediate access by the visible surface algorithm. Finally, the geometric structure suggests a recursive descent, visible surface algorithm in which the computation time potentially grows linearly with the visible complexity of the scene.

γ-ray bursts from thermonuclear explosions on neutron stars

Abstract: It is proposed that γ-ray bursts originate from carbon detonations initiated by the accretion of matter on to the surface of a neutron star. The observations are interpreted in terms of this theory. Possible implications for the nuclear powered model of giant X-ray pulses are discussed briefly.

Women and Power: Toward a Theory of Effectiveness

Abstract: This paper develops a theory of sex-role stereotyping and power use in terms of how people interact in daily life situations. Power use is proposed to be affected by sex-role stereotypes on three major dimensions: direct-indirect, concrete-personal, and competent-helpless. It is demonstrated that women have less access, in reality and in expectations, to concrete resources and competence, leaving them with indirect, personal, and helpless modes of influence. Power use is examined in terms of sex-role stereotypes, and data are presented which support the hypothesis that people expect males and females to use different bases of power.

Mare basalts: Crystal chemistry, mineralogy, and petrology

Abstract: The paper attempts a synthesis of the major-element chemistry, petrography, mineral chemistry, and crystal chemistry of the mare basalts returned by Apollo and Luna missions A classification of the mare basalts based on major-element chemistry is given, and textural sequences within each major-element group are identified The mineral chemistry and crystal chemistry of each mineral group are considered within the framework of the major-element groups and the textural sequences The various classes of models for the origin of the mare basalts and the nature of their source regions are discussed in the context of the major- and trace-element chemistries and experimental investigations

Composition and age of Lau Basin and Ridge volcanic rocks: Implications for evolution of an interarc basin and remnant arc

Abstract: The Tonga-Kermadec Ridge, Lau Basin, and Lau-Colville Ridge are, respectively, a frontal arc, interarc basin, and remnant arc at the Australian-Pacific plate boundary. Basement rocks of the Lau-Colville Ridge (Lau Volcanics) are 9- to 6-m.y.-old basaltic andesites to dacites with 55 to 66 percent SiO 2 , K 60 = 1.0 to 1.5 percent, little Fe enrichment, Sr 87 /Sr 86 = 0.7030 to 0.7034, and enrichment in light rare-earth elements. Westward increases in K, Rb, Th, and U suggest that subducted lithosphere was un-derthrust from the east. Variations in rock composition are consistent qualitatively with derivation from basalt by low-pressure crystal-liquid fractionation involving removal of phenocryst phases: plagioclase + clinopyroxene + orthopyroxene + magnetite. Volcaniclastic turbidites of the same age and derived from western sources are found in Tonga. These andesitic vol-canogenic recks are overlain on both ridges by Pliocene limestones, which are capped on the Lau-Colville Ridge by 3.9- to 3.5-m.y.-old olivine + hypersthene normative tholeiites (Korombasanga Volcanics) having minor 56 to 60 percent SiO 2 andesitic differentiates. Lau Basin basalts are transitional between ocean-floor and island-arc tholeiites, sharing with the latter their higher Rb, Ba, light rare-earth element, and Sr 87 contents and lower Ti, Zr, and Hf contents. These data support Karig9s idea that the Lau and Tonga Ridges represent a once-united island arc now dismembered by rifting, which has formed the intervening Lau Basin. This rifting began about 5 m.y. B.P. The change in volcanism on the Lau-Colville Ridge reflects its removal from a subduction site.

Form, genesis, and deformation of central California wave-cut platforms

Abstract: Modern and ancient wave-cut platforms on Ben Lomond Mountain in central California are broadly similar in shape. They have a seaward slope composed of two segments: a steeper, slightly concave inshore segment, with gradients of generally 0.02 to 0.04 (20 to 40 m/km), and a flatter, planar offshore segment with gradients of 0.007 to 0.017 (7 to 17 m/km). The flattest inshore and offshore gradients measured were, respectively, 0.015 (15 m/km) and 0.005 (5 m/km), suggesting that these are close to minimum gradients for erosional platforms in central California. The inshore segments are generally 300 to 600 m wide and extend to a depth of 8 to 13 m. Platforms are widest in areas where soft sandstone crops out and where there has been least uplift. Major storm waves now break in water 7 to 12 m deep. We conclude that inshore platform segments were associated with storm-wave surf zones and that offshore segments were associated with the zone of deep-water wave transformation. A gradient of 0.005 for the offshore segment would keep wave energy at the bottom constant (Zenkovich, 1967). A steeper gradient for the inshore segment would enable backwash undertow to counteract the strong onshore movement of surf, so that available coarse sediment could be moved laterally. Slopes less than the minimum would so dissipate wave energy in offshore areas that the surf zone would not be able to provide the needed longshore transport for coarse sediment, and beach progradation would result. Thus, platforms have a shape that allows efficient conversion of wave energy into erosion and longshore transport; their seaward gradient is not used for the downhill transport of sediment. Platform gradients decrease with time, at least until the minimum is achieved. Whether the offshore segments were eroded at their existing depths or were eroded by surf zones as sea level rose remains a matter of controversy. Ben Lomond platforms have been uplifted and progressively tilted in a seaward direction, indicating that late Tertiary domical uplift has continued into Quaternary time. Uplift rates have ranged from 0.16 m/1,000 yr near Santa Cruz to 0.26 m/1,000 yr near Greyhound Rock. Tilts have varied from 0.001 (1 m/km) for the lowest prominent platform to 0.009 (9 m/km) for the highest platform (which may be as old as 10 6 yr). Because of uplift, platforms must have been cut at times of eustatically high sea level.

A model of visuomotor mechanisms in the frog optic tectum

Abstract: This paper describes a model of information-processing mechanisms in the frog visual system. The model delimits a class of specific mechanisms. One of these mechanisms, which utilizes cells like the “sameness” and “newness” cells reported in the frog optic tectum, is presented. Results of a computer simulation demonstrate the mechanism's performance.

Pattern Recognition in Humans: Correlations Which Cannot be Perceived

Abstract: Random-dot Moire patterns are manipulated to destroy our ability to perceive the spatial correlations which remain present in the patterns.

Designing surfaces in 3-D

Abstract: An experimental system for computer-aided design of free-form surfaces in three dimensions is described. The surfaces are represented in the system as parametric basis splines. The principal features of the system are: (1) the surfaces are rendered as isoparametric line drawings on a head-mounted display, and they are designed with the aid of a three-dimensional “wand,” which allows 3-D movements of the points controlling the shapes of the surfaces, (2) all of the interactions with the surfaces are in real-time, and (3) the mathematical formulations used assume no knowledge of them by the user of the system. Also examined are some of the features that should be part of a practical 3-D system for designing space-forms.

Protein Bodies of Castor Bean Endosperm Isolation, Fractionation, and the Characterization of Protein Components

Abstract: Protein bodies in the endosperm of castor bean seeds (Ricinus communis L.) contain phytin globoids and protein crystalloids embedded in an amorphous proteinaceous matrix. The protein bodies are apparently surrounded by a single membrane. The protein bodies were isolated by grinding and centrifuging in glycerol. Such isolated protein bodies were almost identical (after cytological fixation) to those observed in situ, except that the globoids were lost. However, membrane-like structures appear to have surrounded the globoids. Histochemical analysis of the isolated protein bodies showed that carbohydrates (glycoproteins) are localized only in the matrix region.Addition of water to protein bodies in glycerol caused dissolution of the matrix, and release of the globoids and crystalloids. When the crystalloids were centrifuged on sucrose density gradients, they were recovered at an equilibrium density of 1.29 to 1.30 g/ml. The crystalloids were only slightly soluble in most aqueous buffers but were very soluble in sodium dodecyl sulfate, urea, or NaOH solutions.Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and chromatography on ion exchange celluloses show that the protein bodies are composed of one major and several minor anodic proteins. The major protein, along with a few of the minor proteins, is localized in the crystalloids.The major protein (molecular weight 65,000) was converted by mercaptoethanol into subunits with molecular weights of 32,000 and 15,800. It is proposed that the protein is made up of two of the smaller subunits and one of the larger, linked by disulfide bridges. None of the crystalloid proteins appear to be glycosylated.The water-soluble matrix fraction is composed mainly of two proteins, with molecular weights of 12,500 and 10,300 on the gels. Neither is a glycoprotein, and neither can be reduced with mercaptoethanol to give subunits. The soluble fraction also contains other lesser components among which are several glycoprotein lectins. One of these is ricin D, which is the main glycoprotein in the protein bodies.

Sedimentology, structural geology, and tectonics of the Shikoku subduction zone, southwestern Japan

Abstract: The Shikoku subduction zone is developed along the Nankai Trough where the Philippine plate is underthrust beneath the Asian plate. The landward wall of the Nankai Trough consists of horizontal parallel ridges and basins that trend northeastward. A Deep Sea Drilling Project site (Leg 31, site 298) on the landward flank of the deepest ridge penetrated 525 m of beds in normal stratigraphic position and 86 m of overturned beds (all of Quaternary age), indicating an overturned anticline. The tight, overturned anticline, which trends parallel to the Nankai Trough, has an inter-limb angle of 9°, an axial surface inclined 9° to 14° landward, and a convergently fanning axial plane fracture cleavage. A coarsening-upward turbidite sequence defines a trench facies and demonstrates direct accretion of deposits from this environment. The convergence rate in the Shikoku subduction zone is estimated to be from 1 to 2 cm/yr, with a strain rate of about 10 −13 /sec. Tectonic consolidation has reduced the volume of the subducted and accreted rocks at least one-third. Olistrostromes form as a direct consequence of fold evolution in the submarine environment and can be immediately underthrust, thereby developing a structural fabric.

Organizational Concepts in the Central Motor Networks of Invertebrates

Abstract: Motor behavior is produced by central networks of neurons that can operate without the aid of sensory feedback. Such networks contain at least four classes of nerve cells; command, oscillator, coordinating and motor neurons. The properties of each of these classes are reviewed briefly.

Production of cell wall hydrolyzing enzymes by barley aleurone layers in response to gibberellic Acid.

Abstract: The cell walls of barley ( Hordeum vulgare var. Himalaya) aleurone layers undergo extensive degradation during the tissue9s response to gibberellic acid. Previous work had shown that these cell walls consist almost entirely of arabinoxylan. In this study we show that gibberellic acid stimulates endo-β-1,4-xylanase activity in isolated aleurone layers. In addition, gibberellic acid enhances the activity of two glycosidases: β-xylopyranosidase and α-arabinofuranosidase. No gibberellic acid-stimulated cellulase activity was detected. Germination studies showed a similar pattern of enzyme development in intact seeds.

Hierarchical geometric models for visible-surface algorithms

Abstract: The research described in this paper addresses the problems associated with the design of systems for efficiently producing computer-generated pictures and picture sequences of very complex, three-dimensional environments. The thesis of the research is that the geometric structure inherent in the definition of the shapes of three-dimensional objects and environments must be used not just to define their relative motion and placement but also to assist in solving many other problems of systems for producing pictures by computer.The implications are that by using an extension of traditional structure information, or a geometric hierarchy, five significant improvements to current techniques are possible. First, the range of complexity of an environment is greatly increased while the visible complexity of any given scene is kept within a fixed upper limit. Second, a meaningful way is provided to vary the amount of detail presented in a scene both according to the screen area occupied by the objects in the scene and according to camera and object motions. Third, by using the geometric hierarchy, "clipping" becomes a very fast logarithmic search for the resolvable parts of the environment within the field-of-view. Fourth, by using this positional hierarchy in conjunction with a storage hierarchy of the sort used in virtual memory computing systems, frame-to-frame coherence and clipping define a graphical "working set", or fraction of the total structure that should be present in primary store for immediate access by the visible-surface algorithms. Finally, the proposed structural framework suggests a new recursive descent visible-surface algorithm in which the computation time grows almost linearly with a scene's visible complexity rather than as a worse than linear function of its object-space complexity.

Ecology and natural history of iridaea cordata (rhodophyta; gigartinaceae): population structure1

Abstract: SUMMARY The population structure of 4 California Iridaea cordata (Turner) Bory populations was studied. Random sampling procedures were used to measure seasonal variations in standing crops, density and size-class distribution of life history stages. The results describe aspects of the in situ life history; a prerequisite to realistically considering the distribution, ecology or life history expressions of an alga. Seasonal fluctuations in density occur only in the juvenile stage, which is initiated during the winter (November to January) predominantly from the basal perennial crusts. Both the gametangial and tetrasporangial stages are present throughout the year. The tetrasporangial stage is dominant in relation to the sexual stages in both density and biomass during most of the year, except spring when the new crop in just maturing and all stages are abundant. Density in nearly constant and observable changes in the populations are due to biomass fluctuations. Seasonal lows in biomass occur during the winter with the majority of thalli in the smaller size-classes. Growth and maturation culminate in peak summer crops and dominance of the tetrasporangial stage, followed by autumnal senescence and die-back in winter. Carrageenans analyzed from immature thalli showed a predominance of lambda-type, previously determined as specific for tetrasporangial plants. This indirect evidence for the tetrasporangial nature of immature plants suggests that dominance of the diploid stage occurred prior to blade development and most likely at the spore level. Alternatively, field results indicate a major contribution and possible replacement of alternation of gametangial and tetrasporangial stage by thallus perennation and vegetative reproduction.

Phase transition from baryon to quark matter

Abstract: THE equation of state of matter compressed to supernuclear densities is of considerable interest in astrophysics. For example, pulsars are stars compressed to densities greater than the density of atomic nuclei and are thought to be composed primarily of neutrons, based on detailed calculations of the equation of state of baryonic matter assuming that interaction potentials for the baryons (nucleons and hyperons) are derived from low energy nuclear physics1. There is, however, considerable evidence from high energy physics that baryons have structure, and it is currently believed that this structure is due to the fact that all hadrons consist of quarks bound by vector gluons2. The fact that free, isolated quarks have not been observed has led to the speculation that quarks may be permanently bound inside hadrons3. Since the quarks inside the nucleon behave as free particles2, the forces confining the quarks apparently become strong only when the distance between quarks exceeds the radius of a nucleon, ∼ 10−13 cm. When the density of matter is increased beyond the point that the mean distance between quarks in different baryons is ≪ 10−13 cm the description of matter as interacting baryons becomes invalid, and instead, a description of matter composed of quarks becomes relevant. At sufficiently high densities matter will behave like a relativistic gas of free quarks4 with P ≃ ρ/3, where P is the pressure and ρ is the energy density of matter. The density at which the baryon to quark transition occurs is of crucial importance to the structure of pulsars. General relativity implies that for a given equation of state there is a maximum energy density for stable stars1. It is therefore of considerable interest to know whether the energy density of baryon matter at the baryon–quark phase transition is less than this maximum value. Indeed, it has recently been suggested5 that the existence of quark matter inside pulsars would allow larger masses for pulsars than was previously thought possible. We will show, however, that there are reasons to doubt this.

Role of the endoplasmic reticulum in glyoxysome formation in castor bean endosperm.

Abstract: Homogenates of the endosperm of castor bean ( Ricinus communis var. Hale) were prepared at intervals during germination and fractionated on sucrose gradients. Early in germination when glyoxysomes were being produced, a substantial proportion (50%) of the activities of malate synthetase and citrate synthetase was recovered in the membranes of the endoplasmic reticulum (mean density 1.12 grams per cubic centimeter). This proportion declined to less than 10% at 4 days when the glyoxysomes were fully developed. Gradient fractions challenged by antiglyoxysome-protein antiserum in double immunodiffusion assay revealed strong antigenic response in the endoplasmic reticulum membranes. The results support the view advanced earlier that glyoxysomes are derived directly from the endoplasmic reticulum.

Achievement Motivation in Children of Three Ethnic Groups in the United States

Abstract: Children of three ethnic groups in the United States-Anglos, Blacks, and Mexican Americans-were asked to tell a story to each of seven line drawings depicting persons in a setting related to education. Stories were scored for n Achievement and family achievement (oriented toward achievement goals from which the family would benefit or that would gain recognition from family members). The results showed that Mexican-American and Black children scored higher on family achievement than did Anglo children. Anglos, however, scored higher on n Achievement. On those cards depicting parental figures, however, Mexican-American and Black children tended to score higher on n Achievement than Anglo children. Females in all three ethnic groups scored lower on n Achievement but higher on family achievement than males. It was concluded that contextual conditions are most important in expression of achievement motivation and that the particular form in which achievement is expressed is determined by the definition that c...

Colligative Properties of Simple Solutions

Abstract: Vapor pressure lowering, osmotic pressure, boiling point elevation, and freezing point depression are all related quantitatively to the decrease in µ1soln upon the addition of solute in forming a solution. In any equilibrium system, regardless of whether it is in a gravitational field or whether it contains walls, semipermeable membranes, phase transitions, or solutes, all equilibria are maintained locally, in the small region of the equilibrium, by the equality of µ1soln. If there are several subsystems in a gravitational field, at any fixed height, µi will have the same value in each subsystem into which substance i can get, and µi + Migh is constant throughout the entire system. In a solution, there is no mechanism by which solvent and solute molecules could sustain different pressures. Both the solvent and solute are always under identical pressures in a region of solution, namely, the pressure of the solution in that region. Since nature does not know which component we call the solvent and which the solute, equations should be symmetric in the two (acknowledging that the nonvolatile component, if any, is commonly chosen to be solute). Simple molecular pictures illustrate what is happening to cause pressure (positive or negative) in liquids, vapor pressure of liquids, and the various colligative properties of solutions. The only effect of solute involved in these properties is that it dilutes the solvent, with the resulting increase in S and decrease in µ1soln. Water can be driven passively up a tree to enormous heights by the difference between its chemical potential in the roots and the ambient air. There is nothing mysterious about the molecular bases for any of these phenomena. Biologists can use the well-understood pictures of these phenomena with confidence to study what is happening in the complicated living systems they consider.

The cellular DNA content of sharks, rays and some other fishes.

Abstract: 1. 1. The haploid amount of DNA was determined for 31 species of elasmobranchs and 8 other non-teleost fishes. 2. 2. The elasmobranchs have a modal DNA amount of about 4 pg, compared to 1 pg for the teleosts. 3. 3. The DNA content of the other non-teleosts ranges from 1.2 at the low end to 142 pg for lungfishes that have been assayed. 4. 4. Several characteristics that are common to DNA distributions in many different groups of organisms, such as a skewed distribution and the positive correlation between specialization and a low amount of DNA, are apparent here. The lungfishes appear to be an exception to the latter characteristic.

Formation of stable crystalline enzyme–substrate intermediates at sub-zero temperatures

Abstract: Sub-zero temperatures can be used to trap intermediates in enzyme-catalysed reactions using suitable cryosolvents. The feasibility of obtaining such intermediates in the crystalline state for X-ray diffraction studies has been demonstrated with several proteases, using specific substrates and optimal pH.

Complementation analysis of linked circadian clock mutants of Neurospora crassa.

Abstract: A fourth mutant of Neurospora crassa, designated frq-4, has been isolated in which the period length of the circadian conidiation rhythm is shortened to 19. +/- 0.3 hours. This mutant is tightly linked to the three previously isolated frq mutants, and all four map to the right arm of linkage group VII about 10 map units from the centromere. Complementation tests suggest, but do not prove, that all four mutations are allelic, since each of the four mutants is co-dominant with the frq+ allel--i.e., heterokaryons have period lengths intermediate between the mutant and wild-type--and since heterokaryons between pairs of mutants also have period lengths intermediate between those of the two mutants.