Showing papers by "University of California, Santa Cruz published in 1996"

The conscious mind: in search of a fundamental theory

Abstract: I. PRELIMINARIES 1. Two Concepts of Mind 2. Supervenience and Explanation II. THE IRREDUCIBILITY OF CONSCIOUSNESS 3. Can Consciousness be Reductively Explained? 4. Naturalistic Dualism 5. The Paradox of Phenomenal Judgment III. TOWARD A THEORY OF CONSCIOUSNESS 6. The Coherence between Consciousness and Cognition 7. Absent Qualia, Fading Qualia, Dancing Qualia 8. Consciousness and Information: Some Speculation IV. APPLICATIONS 9. Strong Artificial Intelligence 10. The Interpretation of Quantum Mechanics Notes Bibliography

Challenges in the Quest for Keystones

Abstract: Mary E. Power is a professor in the Department of Integrative Biology, University of California, Berkeley, CA 94720. David Tilman is a professor in the Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN 55108. James A. Estes is a wildlife biologist in the National Biological Service, Institute of Marine Science, University of California, Santa Cruz, CA 95064. Bruce A. Menge is a professor in the Department of Zoology, Oregon State University, Corvallis, OR 97331. William J. Bond is a professor doctor in the Department of Botany, University of Cape Town, Rondebosch 7700 South Africa. L. Scott Mills is an assistant professor in the Wildlife Biology Program, School of Forestry, University of Montana, Missoula, MT 59812. Gretchen Daily is Bing Interdisciplinary Research Scientist, Department of Biological Science, Stanford University, Stanford, CA 94305. Juan Carlos Castilla is a full professor and marine biology head in Facultad de Ciencias Biologicas, Pontificia Universidad Catolica de Chile, Casilla 114-D, Santiago, Chile. Jane Lubchenco is a distinguished professor in the Department of Zoology, Oregon State University, Corvallis, OR 97331. Robert T. Paine is a professor in the Department of Zoology, NJ-15, University of Washington, Seattle, WA 98195. ? 1996 American Institute of Biological Sciences. A keystone species is

An efficient routing protocol for wireless networks

Abstract: We present the Wireless Routing Protocol (WRP). In WRP, routing nodes communicate the distance and second-to-last hop for each destination. WRP reduces the number of cases in which a temporary routing loop can occur, which accounts for its fast convergence properties. A detailed proof of correctness is presented and its performance is compared by simulation with the performance of the distributed Bellman-Ford Algorithm (DBF), DUAL (a loop-free distance-vector algorithm) and an Ideal Link-state Algorithm (ILS), which represent the state of the art of internet routing. The simulation results indicate that WRP is the most efficient of the alternatives analyzed.

Transformations of Galaxies. II. Gasdynamics in Merging Disk Galaxies

Abstract: In mergers of disk galaxies, gas plays a role quite out of proportion to its relatively modest contribution to the total mass. To study this behavior, we have included gasdynamics in self-consistent simulations of collisions between equal-mass disk galaxies. The large-scale dynamics of bridge- and tail-making, orbit decay, and merging are not much altered by the inclusion of a gaseous component. However, tidal forces during encounters cause otherwise stable disks to develop bars, and the gas in such barred disks, subjected to strong gravitational torques, flows toward the central regions where it may fuel the kiloparsec-scale starbursts seen in some interacting disk systems. Similar torques on the gas during the final stages of a collision yield massive gas concentrations in the cores of merger remnants, which may be plausibly identified with the molecular complexes seen in objects such as NGC 520 and Arp 220. This result appears insensitive to the detailed microphysics of the gas, provided that radiative cooling is permitted. The inflowing gas can dramatically alter the stellar morphology of a merger remnant, apparently by deepening the potential well and thereby changing the boundaries between the major orbital families.

Orbital migration of the planetary companion of 51 Pegasi to its present location

Abstract: THE recent discovery1 and confirmation2 of a possible planetary companion orbiting the solar-type star 51 Pegasi represent a breakthrough in the search for extrasolar planetary systems. Analysis of systematic variations in the velocity of the star indicate that the mass of the companion is approximately that of Jupiter, and that it is travelling in a nearly circular orbit at a distance from the star of 0.05 AU (about seven stellar radii). Here we show that, if the companion is indeed a gas-giant planet, it is extremely unlikely to have formed at its present location. We suggest instead that the planet probably formed by gradual accretion of solids and capture of gas at a much larger distance from the star (∼5 AU), and that it subsequently migrated inwards through interactions with the remnants of the circumstellar disk. The planet's migration may have stopped in its present orbit as a result of tidal interactions with the star, or through truncation of the inner circumstellar disk by the stellar magnetosphere.

On orthogonal and symplectic matrix ensembles

Abstract: The focus of this paper is on the probability,Eβ(O;J), that a setJ consisting of a finite union of intervals contains no eigenvalues for the finiteN Gaussian Orthogonal (β=1) and Gaussian Symplectic (β=4) Ensembles and their respective scaling limits both in the bulk and at the edge of the spectrum. We show how these probabilities can be expressed in terms of quantities arising in the corresponding unitary (β=2) ensembles. Our most explicit new results concern the distribution of the largest eigenvalue in each of these ensembles. In the edge scaling limit we show that these largest eigenvalue distributions are given in terms of a particular Painleve II function.

Bedrock incision, rock uplift and threshold hillslopes in the northwestern Himalayas

Abstract: The topography of tectonically active mountain ranges reflects a poorly understood competition between bedrock uplift and erosion. Dating of abandoned river-cut surfaces in the northwestern Himalayas reveals that the Indus river incises through the bedrock at extremely high rates (2–12 mm yr-1). In the surrounding mountains, the average angles of hillslopes are steep and essentially independent of erosion rate, suggesting control by a common threshold process. In this rapidly deforming region, an equilibrium is maintained between bedrock uplift and river incision, with landsliding allowing hillslopes to adjust efficiently to rapid river down-cutting.

Sexually antagonistic male adaptation triggered by experimental arrest of female evolution

Abstract: EACH sex is part of the environment of the other sex. This may lead to perpetual coevolution between the sexes, when adaptation by one sex reduces fitness of the other. Indirect evidence comes from experiments with Drosophila melanogaster indicating that seminal fluid reduces the competitive ability of sperm from other males, thereby increasing male fitness1,2. It also reduces a female's propensity to remate and increases her egg-laying rate3. In contrast to these benefits to males, seminal fluid has substantial toxic side effects in females, with increasing quantity leading to decreasing female survival4,5. Here I show that when female D. melanogaster are experimentally prevented from coevolving with males, males rapidly adapt to the static female phenotype. This male adaptation leads to a reduction in female survivorship, which is mediated by an increased rate of remating and increased toxicity of seminal fluid.

Experimental queueing analysis with long-range dependent packet traffic

Abstract: Traffic measurement studies from a wide range of working packet networks have convincingly established the presence of significant statistical features that are characteristic of fractal traffic processes, in the sense that these features span many time scales. Of particular interest in packet traffic modeling is a property called long-range dependence (LRD), which is marked by the presence of correlations that can extend over many time scales. We demonstrate empirically that, beyond its statistical significance in traffic measurements, long-range dependence has considerable impact on queueing performance, and is a dominant characteristic for a number of packet traffic engineering problems. In addition, we give conditions under which the use of compact and simple traffic models that incorporate long-range dependence in a parsimonious manner (e.g., fractional Brownian motion) is justified and can lead to new insights into the traffic management of high speed networks.

Structure of the A Site of Escherichia coli 16S Ribosomal RNA Complexed with an Aminoglycoside Antibiotic

Abstract: Aminoglycoside antibiotics that bind to 30S ribosomal A-site RNA cause misreading of the genetic code and inhibit translocation. The aminoglycoside antibiotic paromomycin binds specifically to an RNA oligonucleotide that contains the 30S subunit A site, and the solution structure of the RNA-paromomycin complex was determined by nuclear magnetic resonance spectroscopy. The antibiotic binds in the major groove of the model A-site RNA within a pocket created by an A-A base pair and a single bulged adenine. Specific interactions occur between aminoglycoside chemical groups important for antibiotic activity and conserved nucleotides in the RNA. The structure explains binding of diverse aminoglycosides to the ribosome, their specific activity against prokaryotic organisms, and various resistance mechanisms, and provides insight into ribosome function.

Digital Video: An introduction to MPEG-2

Abstract: From the Publisher: This book offers comprehensive coverage of the MPEG-2 audio / visual digital compression standard. The treatment includes the specifics needed to implement an MPEG-2 Decoder, including the syntax and semantics of the coded bitstreams. Since the MPEG-2 Encoders are not specified by the standard, and are actually closely held secrets of many vendors, the book only outlines the fundamentals of encoder design and algorithm optimization.

Nucleosynthesis in Neutrino-Driven Winds. I. The Physical Conditions

Abstract: During the first 20 s of its life, the enormous neutrino luminosity of a neutron star drives appreciable mass loss from its surface. Previous investigations have shown that this neutrino-driven wind could be the site where the r-process occurs. The nucleosynthesis is sensitive to four physical parameters that characterize the wind: its mass-loss rate, the entropy per baryon, the electron fraction, and the dynamic timescale. Different authors, using numerical models for supernovae, have arrived at qualitatively different values for these key parameters. Here we derive their values analytically and test our analytic results by numerical calculations using an implicit hydrodynamic code. Employing our analytic and numerical methods, we also investigate how various factors can affect our results. The derived entropy typically falls short, by a factor of 2?3, of the value required to produce a strong r-process. Various factors that might give a higher entropy or a more rapid expansion in the wind are discussed.

Approaches to uncertainty visualization

Abstract: Visualized data often have dubious origins and quality. Different forms of uncertainty and errors are also introduced as the data are derived, transformed, interpolated, and finally rendered. In the absence of integrated presentation of data and uncertainty, the analysis of the visualization is incomplete at best and often leads to inaccurate or incorrect conclusions. This paper surveys techniques for presenting data together with uncertainty. These uncertainty visualization techniques present data in such a manner that users are made aware of the locations and degree of uncertainties in their data so as to make more informed analyses and decisions. The techniques include adding glyphs, adding geometry, modifying geometry, modifying attributes, animation, sonification, and psycho-visual approaches. We present our results in uncertainty visualization for environmental visualization, surface interpolation, global illumination with radiosity, flow visualization, and figure animation. We also present a classification of the possibilities in uncertainty visualization, and locate our contributions within this classification.

Seismic Evidence for Partial Melt at the Base of Earth's Mantle

Abstract: The presence of an intermittent layer at the base of Earth9s mantle with a maximum thickness near 40 kilometers and a compressional wave velocity depressed by ∼10 percent compared with that of the overlying mantle is most simply explained as the result of partial melt at this depth. Both the sharp upper boundary of this layer (

Ethnic and Racial Self-Employment Differences and Possible Explanations

Abstract: The significant differences in self-employment rates across a large number of ethnic/racial groups are documented, and possible explanations for these differences are considered. Data from the 1990 U.S. Census of Population were used to examine 60 different ethnic/racial groups in the United States - this specificity allows identification of patterns not previously noted. Findings show that the self-employment rates differ enormously by ethnic/racial group for both men and women. All of the European groups have self-employment rates near or above the overall U.S. rates, for both genders. However, since the range across these groups is large, the broad categories of European or white would hide important differences across the ancestry groups. Ethnic/racial groups with origins in the Middle East or neighboring countries tend to have high self-employment rates. Asian self-employment rates differ substantially across ancestry groups. For example, the self-employment rates of Filipinos and Laotians are at or near the bottom of the distribution of self-employment rates, while the Koreans are at or near the top. The self-employment rates for Hispanic men and women are typically below the average U.S. rates. Black ethnic/racial groups--which include African Americans, Blacks from Central America, South America, Africa, and the Caribbean--have the lowest self-employment rates of any broad group. Black Africans and Blacks from the Caribbean have low self-employment rates compared to U.S. rates, but have notably higher rates of self-employment than African Americans. The only ethnic/racial group with higher estimated self-employment rates for women than men is the Vietnamese. In addition to ethnic/racial group and gender differences, it was found that each higher level of education is associated with a higher probability of self-employment. Explanations and theories for self-employment patterns and determinants have been offered in previous sociological and economics literature. Some of these theories are presented and their limitations discussed. One theory, regarding sojourners, suggests that self-employment is more frequent among immigrant groups who expect to spend a short time in the United States. However, results from the current study demonstrate that immigrants who have been in the U.S. for more than 30 years have higher self-employment rates than immigrants who have been in the country fewer than 10 years. Another theory argues that disadvantages such as poor English, poverty, or discrimination would compel certain groups to favor self-employment. However, this study found evidence contrary to this theory. The more advantaged groups, measured by earnings and other income, have the highest self-employment rates. Additional theoretical explanations for self-employment are examined, and often found to be applicable only for certain ethnic groups. (SFL)

Latency-rate servers: a general model for analysis of traffic scheduling algorithms

Abstract: In this paper, we develop a general model, called latency-rate servers (LR-servers), for the analysis of traffic scheduling algorithms in broadband packet networks. The behavior of an LR scheduler is determined by two parameters-the latency and the allocated rate. We show that several well-known scheduling algorithms, such as weighted fair queueing, virtualclock, self-clocked fair queueing, weighted round robin, and deficit round robin, belong to the class of LR-servers. We derive tight upper bounds on the end-to-end delay, internal burstiness, and buffer requirements of individual sessions in an arbitrary network of LR-servers in terms of the latencies of the individual schedulers in the network, when the session traffic is shaped by a leaky bucket. Thus, the theory of LR-servers enables computation of tight upper-bounds on end-to-end delay and buffer requirements in a network of servers in which the servers on a path may not all use the same scheduling algorithm. We also define a self-contained approach to evaluate the fairness of LR-servers and use it to compare the fairness of many well-known scheduling algorithms.

Hidden Markov models for sequence analysis: extension and analysis of the basic method

Abstract: Hidden Markov models (HMMs) are a highly effective means of modeling a family of unaligned sequences or a common motif within a set of unaligned sequences. The trained HMM can then be used for discrimination or multiple alignment. The basic mathematical description of an HMM and its expectation-maximization training procedure is relatively straightforward. In this paper, we review the mathematical extensions and heuristics that move the method from the theoretical to the practical. We then experimentally analyze the effectiveness of model regularization, dynamic model modification and optimization strategies. Finally it is demonstrated on the SH2 domain how a domain can be found from unaligned sequences using a special model type. The experimental work was completed with the aid of the Sequence Alignment and Modeling software suite.

The Lyman alpha forest in the cold dark matter model

Abstract: Cosmological simulations with gas provide a detailed description of the intergalactic medium, which makes possible predictions of neutral hydrogen absorption in the spectra of background QSOs. We present results from a high-resolution calculation of an Ω = 1 cold dark matter model. Our simulation reproduces many of the observed properties of the Lyα forest surprisingly well. The distribution of H I column densities agrees with existing data to within a factor of ~2 over most of the range from 1014 cm-2 to 1022 cm-2; i.e., from unsaturated Lyα forest lines to damped Lyα systems. The equivalent width distribution matches the observed exponential form with a characteristic width W* ≈ 0.3 A. The distribution of b-parameters appears consistent with that derived from QSO spectra. Most of the low column density absorption arises in large, flattened structures of moderate or even relatively low overdensity, so there is no sharp distinction between the Lyα forest and the "Gunn-Peterson" absorption produced by the smooth intergalactic medium. Our results demonstrate that a Lyα forest like that observed develops naturally in a hierarchical clustering scenario with a photoionizing background. Comparison between simulations and high-resolution QSO spectra should open a new regime for testing theories of cosmic structure formation.

Pore fluid constraints on the temperature and oxygen isotopic composition of the glacial ocean

Abstract: Pore fluids from the upper 60 meters of sediment 3000 meters below the surface of the tropical Atlantic indicate that the oxygen isotopic composition (δ 18 O) of seawater at this site during the last glacial maximum was 0.8 ± 0.1 per mil higher than it is today. Combined with the δ 18 O change in benthic foraminifera from this region, the elevated ratio indicates that the temperature of deep water in the tropical Atlantic Ocean was 4°C colder during the last glacial maximum. Extrapolation from this site to a global average suggests that the ice volume contribution to the change in δ 18 O of foraminifera is 1.0 per mil, which partially reconciles the foraminiferal oxygen isotope record of tropical sea surface temperatures with estimates from Barbados corals and terrestrial climate proxies.

Functional morphology and homology in the odontocete nasal complex: implications for sound generation

Abstract: The site and physiologic mechanism(s) responsible for the generation of odontocete biosonar signals have eluded investigators for decades. To address these issues we subjected postmortem toothed whale heads to interrogation using medical imaging techniques. Most of the 40 specimens (from 19 species) were examined using x-ray computed tomography (CT) and/or magnetic resonance imaging (MR). Interpretation of scan images was aided by subsequent dissection of the specimens or, in one case, by cryosectioning. In all specimens we described a similar tissue complex and identified it as the hypothetical biosonar signal generator. This complex includes a small pair of fatty bursae embedded in a pair of connective tissue lips, a cartilaginous blade, a stout ligament, and an array of soft tissue air sacs. Comparing and contrasting the morphologic patterns of nasal structures across species representing every extant odontocete superfamily reveals probable homologous relationships, which suggests that all toothed whales may be making their biosonar signals by a similar mechanism.

A Generalized Hidden Markov Model for the Recognition of Human Genes in DNA

Abstract: We present a statistical model of genes in DNA A Generalized Hidden Markov Model (GHMM) provides the framework for describing the grammar of a legal parse of a DNA sequence (Stormo & Haussler 1994) Probabilities are assigned to transitions between states in the GHMM and to the generation of each nucleotide base given a particular state Machine learning techniques are applied to optimize these probabilities using a standardized training set Given a new candidate sequence, the best parse is deduced from the model using a dynamic programming algorithm to identify the path through the model with maximum probability The GHMM is flexible and modular, so new sensors and additional states can be inserted easily In addition, it provides simple solutions for integrating cardinality constraints, reading frame constraints, "indels", and homology searching The description and results of an implementation of such a gene-finding model, called Genie, is presented The exon sensor is a codon frequency model conditioned on windowed nucleotide frequency and the preceding codon Two neural networks are used, as in (Brunak, Engelbrecht, & Knudsen 1991), for splice site prediction We show that this simple model performs quite well For a cross-validated standard test set of 304 genes [ftp:@www-hgclblgov/pub/genesets] in human DNA, our gene-finding system identified up to 85% of protein-coding bases correctly with a specificity of 80% 58% of exons were exactly identified with a specificity of 51% Genie is shown to perform favorably compared with several other gene-finding systems

Abundances at High Redshifts: The Chemical Enrichment History of Damped Lyα Galaxies

Abstract: We study the elemental abundances of C, N, O, Al, Si, S, Cr, Mn, Fe, Ni, and Zn in a sample of 14 damped Lyα systems (galaxies) with H I column density N(H I) ≥ 1020 cm−2, using high-quality spectra quasars obtained with the 10 m Keck telescope To ensure accuracy, only weak, unsaturated absorption lines are used to derive ion column densities and elemental abundances Combining these abundance measurements with similar measurements in the literature, we investigate the chemical evolution of damped Lyα galaxies based on a sample of 23 systems in the redshift range 07 3 in our sample have (Fe/H) around 1/100 solar or less In comparison, a large fraction of the damped Lyα galaxies at z < 3 have reached 10 times higher metallicity This suggests that the time around z = 3 may be the epoch of galaxy formation in the sense that galaxies are beginning to form the bulk of their stars Several other lines of evidence appear to point to the same conclusion, including the evolution of the neutral baryon content of damped Lyα galaxies, the evolution in the quasar space density, and the morphology of z < 3 galaxies 4 The relative abundance patterns of the elements studied here clearly indicate that the bulk of heavy elements in these high-redshift galaxies were produced by Type II supernovae; there is little evidence for significant contributions from stellar mass loss of low- to intermediate-mass stars or from Type Ia supernovae 5 Although earlier studies have attributed the overabundance of Zn relative to Cr or Fe found in damped Lyα galaxies to selective depletion of Cr and Fe by dust grains, such an interpretation is inconsistent with many of the other elemental abundance ratios seen in these galaxies, most notably N/O and Mn/Fe Several other tests also indicate that thereis no significant evidence for dust depletion in these galaxies We suggest that the overabundance of Zn relative to Cr in damped Lyα galaxies may be intrinsic to their stellar nucleosynthesis If this interpretation is correct, it will provide important new information to the theory of stellar nucleosynthesis 6 The absorption profiles of Al III in damped Lyα galaxies are found to resemble those of the low ionization lines The profiles of Si IV and C IV absorption, while resembling each other in general, are almost always different from those of the low-ionization absorption lines These results suggest that Al III is probably produced in the same physical region as the low-ionization species in the absorbing galaxies, while the high-ionization species (Si IV and C IV) mostly likely come from distinct physical regions 7 We discuss possible ways to obtain information on the history of star formation (ie, continuous or episodic) in damped Lyα galaxies and on the shapes of the stellar initial mass functions 8 We review the evidence for, and against, the hypothesis that damped Lyα galaxies are disks or protodisks at high redshifts and discuss the implications 9 We determine upper limits on the temperature of the cosmic microwave background radiation at several redshifts using absorption from the fine-structure level of the C II ion These upper limits are consistent with the predicted increase of TCMBwith redshift

High‐resolution (104 years) deep‐sea foraminiferal stable isotope records of the Eocene‐Oligocene climate transition

Abstract: We have constructed high-resolution (104– 105 years) benthic foraminiferal δ13C and δ18O records for the upper Eocene through lower Oligocene of two pelagic sequences, Deep Sea Drilling Project (DSDP) Site 522 in the Angola Basin, South Atlantic Ocean, and Ocean Drilling Program (ODP) Site 744 in the southern Indian Ocean. These records provide improved constraints on both the timing and magnitude of marine oxygen and carbon isotope events from 30 to 35 Ma. The oxygen isotope records indicate that the ubiquitous δ18O increase (Oi-1), which marks the rapid expansion of continental ice sheets and a minimum of 3° to 4°C of cooling of bottom waters in the earliest Oligocene (33.6 Ma), occurred in <350 kyr. More than half the transition occurred over the final 40–50 kyr. This period of lower temperatures and widespread continental glaciation persisted for roughly 400 kyr (i.e., the duration of magnetochron C13n). These records also indicate that this interval was characterized by at least two ∼ 100-kyr waxing and waning cycles (Oi-1a and Oi-1b) and possibly several higher-frequency events. The benthic foraminiferal δ13C records show a positive 0.8‰ excursion that is nearly isochronous with the Oi-1 oxygen isotope increase. Similar magnitude δ13C increases at other sites indicate this was a global phenomenon suggestive of an unusually large perturbation to the carbon cycle. This excursion was followed by smaller amplitude δ13C oscillations with periods of roughly ∼400 kyr. We suspect that the ubiquitous Oi-1 δ13C excursion resulted from a brief but substantial increase in export production and carbon burial.

The environment of "E+A" galaxies

Abstract: The violent star formation history of ``E+A'' galaxies and their detection almost exclusively in distant clusters is frequently used to link them to the ``Butcher-Oemler effect'' and to argue that cluster environment influences galaxy evolution. From 11113 spectra in the Las Campanas Redshift Survey, we have obtained a unique sample of 21 nearby ``E+A\" galaxies. Surprisingly, a large fraction (about 75%) of these ``E+A''s lie in the field. Therefore, interactions with the cluster environment, in the form of the ICM or cluster potential, are not essential for ``E+A'' formation. If one mechanism is responsible for ``E+A''s, their existence in the field and the tidal features in at least 5 of the 21 argue that galaxy-galaxy interactions and mergers are that mechanism. The most likely environments for such interactions are poor groups, which have lower velocity dispersions than clusters and higher galaxy densities than the field. In hierarchical models, groups fall into clusters in greater numbers at intermediate redshifts than they do today. Thus, the Butcher-Oemler effect may reflect the typical evolution of galaxies in groups and in the field rather than the influence of clusters on star formation in galaxies. This abstract is abridged.