Showing papers by "University of Colorado Boulder published in 1996"

A practical guide to pseudospectral methods

Abstract: 1. Introduction 2. Introduction to spectral methods via orthogonal functions 3. Introduction to PS methods via finite differences 4. Key properties of PS approximations 5. PS variations/enhancements 6. PS methods in polar and spherical geometries 7. Comparisons of computational cost - FD vs. PS methods 8. Some application areas for spectral methods Appendices.

PKD2, a Gene for Polycystic Kidney Disease That Encodes an Integral Membrane Protein

Abstract: A second gene for autosomal dominant polycystic kidney disease was identified by positional cloning. Nonsense mutations in this gene (PKD2) segregated with the disease in three PKD2 families. The predicted 968-amino acid sequence of the PKD2 gene product has six transmembrane spans with intracellular amino- and carboxyl-termini. The PKD2 protein has amino acid similarity with PKD1, the Caenorhabditis elegans homolog of PKD1, and the family of voltage-activated calcium (and sodium) channels, and it contains a potential calcium-binding domain.

Carvedilol Produces Dose-Related Improvements in Left Ventricular Function and Survival in Subjects With Chronic Heart Failure

Abstract: Background We conducted a multicenter, placebo-controlled trial designed to establish the efficacy and safety of carvedilol, a “third-generation” β-blocking agent with vasodilator properties, in chronic heart failure. Methods and Results Three hundred forty-five subjects with mild to moderate, stable chronic heart failure were randomized to receive treatment with placebo, 6.25 mg BID carvedilol (low-dose group), 12.5 mg BID carvedilol (medium-dose group), or 25 mg BID carvedilol (high-dose group). After a 2- to 4-week up-titration period, subjects remained on study medication for a period of 6 months. The primary efficacy parameter was submaximal exercise measured by two different techniques, the 6-minute corridor walk test and the 9-minute self-powered treadmill test. Carvedilol had no detectable effect on submaximal exercise as measured by either technique. However, carvedilol was associated with dose-related improvements in LV function (by 5, 6, and 8 ejection fraction [EF] units in the low-, medium-, ...

Are Good Texts Always Better? Interactions of Text Coherence, Background Knowledge, and Levels of Understanding in Learning From Text

Abstract: Two experiments, theoretically motivated by the construction-integration model of text comprehension (W. Kintsch, 1988), investigated the role of text coherence in the comprehension of science texts. In Experiment 1, junior high school students' comprehension of one of three versions of a biology text was examined via free recall, written questions, and a key-word sorting task. This study demonstrates advantages for globally coherent text and for more explanatory text. In Experiment 2, interactions among local and global text coherence, readers' background knowledge, and levels of understanding were examined. Using the same methods as in Experiment 1, we examined students' comprehension of one of four versions of a text, orthogonally varying local and global coherence. We found that readers who know little about the domain of the text benefit from a coherent text, whereas high-knowledge readers benefit from a minimally coherent text. We argue that the poorly written text forces the knowledgeable readers t...

Reflective Teaching: An Introduction

Abstract: CONTENTS SERIES PREFACE Introduction Examining the Social Conditions of Schooling Understanding and Examining Personal Beliefs about Teaching and Schooling About the Books in this Series Series Acknowledgments PREFACE Acknowledgements 1. UNDERSTANDING REFLECTIVE TEACHING An Initial Distinction: Reflective Teaching and Technical Teaching On Reflective Teaching The Bandwagon of Reflective Teaching 2. HISTORICAL ROOTS OF REFLECTIVE TEACHING Introduction Dewey's Contribution: What is Reflective Teaching? Openmindedness Responsibility Wholeheartedness Reflection and the Pressures of Teaching Schon: "Reflection-on-Action" and "Reflection-in-Action" Framing and Reframing Problems Criticisms of Schon's Conception Reflection: A Singular or Dialogical Activity Reflection as Contextual Summary 3. TEACHERS' PRACTICAL THEORIES Introduction Handal and Lauvas' Framework for Understanding the Source of Teachers' Practical Theories Personal Experience Transmitted Knowledge Values Summary 4. THE STUFF OF REFLECTION Introduction Teaching as emotional labor Thinking and Feeling Metaphors and Images in Teacher Enabling Reflection on Teaching Conclusion 5. REFLECTIVE TEACHING AND EDUCATIONAL TRADITIONS Introduction Teachers, Traditions, and Teaching The Progressive Tradition The Conservative Tradition Core Knowledge - E. D. Hirsch Higher Learning The Social Justice Tradition The Spiritual-Contemplative Tradition Conclusion 6. SELF, STUDENT, AND CONTEXT IN REFLECTIVE TEACHING Introduction The Teaching Self Attending to Students The Context of Schooling The Social Conditions of Schooling Engaging Community and Difference One Last Vignette Concluding Thoughts... Appendix A References

Crystal Structure of a Group I Ribozyme Domain: Principles of RNA Packing

Abstract: Group I self-splicing introns catalyze their own excision from precursor RNAs by way of a two-step transesterification reaction. The catalytic core of these ribozymes is formed by two structural domains. The 2.8-angstrom crystal structure of one of these, the P4-P6 domain of the Tetrahymena thermophila intron, is described. In the 160-nucleotide domain, a sharp bend allows stacked helices of the conserved core to pack alongside helices of an adjacent region. Two specific long-range interactions clamp the two halves of the domain together: a two-Mg2+-coordinated adenosine-rich corkscrew plugs into the minor groove of a helix, and a GAAA hairpin loop binds to a conserved 11-nucleotide internal loop. Metal- and ribose-mediated backbone contacts further stabilize the close side-by-side helical packing. The structure indicates the extent of RNA packing required for the function of large ribozymes, the spliceosome, and the ribosome.

Implementing Service Learning in Higher Education

Abstract: (1996). Implementing Service Learning in Higher Education. The Journal of Higher Education: Vol. 67, No. 2, pp. 221-239.

Coherent Population Trapping in Laser Spectroscopy

Abstract: Publisher Summary This chapter describes the coherent population trapping in laser spectroscopy. Coherent population trapping may be also described as the pumping of the atomic system in a particular state, the coherent superposition of the atomic states, which is a nonabsorbing state. The exciting radiation creates an atomic coherence, such that the atom's evolution is prepared exactly out of phase with the incoming radiation and no absorption takes place. The chapter discusses the basic properties of an atomic system prepared with the coherent population-trapping superposition of states and outlines experimental observations concerned with the establishment of coherent trapping in different discrete systems. The chapter also discusses the theoretical and experimental aspects of trapping that involve states of the continuum and reviews the theoretical and experimental features associated with coherent population trapping in laser cooling, adiabatic transfer, lasing without inversion, pulse matching, and photon statistics. The theoretical aspect of coherent population trapping created by spontaneous emission is also discussed in the chapter.

Role of the subducted slab, mantle wedge and continental crust in the generation of adakites from the Andean Austral Volcanic Zone

Abstract: All six Holocene volcanic centers of the Andean Austral Volcanic Zone (AVZ; 49–54°S) have erupted exclusively adakitic andesites and dacites characterized by low Yb and Y concentrations and high Sr/Y ratios, suggesting a source with residual garnet, amphibole and pyroxene, but little or no olivine and plagioclase. Melting of mafic lower crust may be the source for adakites in some arcs, but such a source is inconsistent with the high Mg# of AVZ adakites. Also, the AVZ occurs in a region of relatively thin crust ( 1), followed by limited interaction of this melt with the overlying mantle (≥90% MORB melt, ≤10% mantle), but only very little (≤1%) or no participation of either subducted sediment or crust. In contrast, models for the magmatic evolution of Burney (52°S), Reclus (51°S) and northernmost AVZ (49–50°S) andesites and dacites require melting of a mixture of MORB and subducted sediment, followed by interaction of this melt not only with the overlying mantle, but the crust as well. Crustal assimilation and fractional crystallization (AFC) processes and the mass contribution from the crust become more significant northwards in the AVZ as the angle of convergence becomes more orthogonal.

The separability of working memory resources for spatial thinking and language processing: an individual differences approach.

Abstract: The current study demonstrates the separability of spatial and verbal working memory resources among college students. In Experiment 1, we developed a spatial span task that taxes both the processing and storage components of spatial working memory. This measure correlates with spatial ability (spatial visualization) measures, but not with verbal ability measures. In contrast, the reading span test, a common test of verbal working memory, correlates with verbal ability measures, but not with spatial ability measures. Experiment 2, which uses an interference paradigm to cross the processing and storage demands of span tasks, replicates this dissociation and further demonstrates that both the processing and storage components of working memory tasks are important for predicting performance on spatial thinking and language processing tasks.

Spectroscopy Made Easy: A New Tool for Fitting Observations with Synthetic Spectra

Abstract: We describe a new software package that may be used to determine stellar and atomic parameters by matching observed spectra with synthetic spectra generated from parameterized atmospheres. A nonlinear least squares algorithm is used to solve for any subset of allowed parameters, which include atomic data (loggf and van der Waals damping constants), model atmosphere specications (Te ,l og g), elemental abundances, and radial, turbulent, and rotational velocities. LTE synthesis software handles discontiguous spectral intervals and complex atomic blends. As a demonstration, we t 26 Fe I lines in the NSO Solar Atlas (Kurucz et al. 1984), determining various solar and atomic parameters.

Fibre beam–column model for non‐linear analysis of r/c frames: part i. formulation

Abstract: A companion paper presents the formulation of a fibre beam-column element for the non-linear static and dynamic analysis of R/C frames. This paper illustrates the application of the proposed element in the simulation of the hysteretic behaviour of several R/C beam and column specimens. The specimens are subjected to uniaxial and biaxial loading histories with varying axial load. The proposed element shows computationally stable and robust numerical behaviour, while being able to describe very well the hysteretic behaviour of the reinforced concrete members under the imposed complex loading histories.

A hierarchical internet object cache

Abstract: This paper discusses the design and performance of a hierarchical proxy-cache designed to make Internet information systems scale better. The design was motivated by our earlier trace-driven simulation study of Internet traffic. We challenge the conventional wisdom that the benefits of hierarchical file caching do not merit the costs, and believe the issue merits reconsideration in the Internet environment. The cache implementation supports a highly concurrent stream of requests. We present performance measurements that show that our cache outperforms other popular Internet cache implementations by an order of magnitude under concurrent load. These measurements indicate that hierarchy does not measurably increase access latency. Our software can also be configured as a Web-server accelerator; we present data that our httpd-accelerator is ten times faster than Netscape's Netsite and NCSA 1.4 servers. Finally, we relate our experience fitting the cache into the increasingly complex and operational world of Internet information systems, including issues related to security, transparency to cache-unaware clients, and the role of file systems in support of ubiquitous wide-area information systems.

Surface Chemistry for Atomic Layer Growth

Abstract: Atomic layer controlled film growth is an important technological and scientific goal that is closely tied to many issues in surface chemistry. This article first reviews the basic concepts of atomic layer growth using molecular precursors and binary reaction sequence chemistry. Many examples are given for the various films that have been grown using this atomic layer growth technique. The paradigms for atomic layer epitaxy (ALE) and atomic layer processing (ALP) are then discussed in terms of self-limiting surface reactions. Recent investigations of the surface chemistry of SiO2 and Al2O3 ALP and GaAs ALE are examined and used to illustrate the possible mechanisms of atomic layer growth. Subsequently, the characteristics of film deposition using atomic layer growth techniques are explored using recent examples for Al2O3 ALP. The structure of the deposited films is also reviewed using results from previous Al2O3 deposition investigations. This article then concludes by discussing possible complications to...

Overview of Arctic Cloud and Radiation Characteristics

Abstract: To provide a background for ARM's activities at the North Slope of Alaska/Adjacent Arctic Ocean sites, an overview is given of our current state of knowledge of Arctic cloud and radiation properties and processes. The authors describe the Arctic temperature and humidity characteristics, cloud properties and processes, radiative characteristics of the atmosphere and surface, direct and indirect radiative effects of aerosols, and the modeling and satellite remote sensing of cloud and radiative characteristics. An assessment is given of the current performance of satellite remote sensing and climate modeling in the Arctic as related to cloud and radiation issues. Radiation-climate feedback processes are discussed, and estimates are made of the sign and magnitude of the individual feedback components. Future plans to address these issues are described.

Key issues in information systems management: 1994–95 SIM Delphi results

Abstract: Over the past 15 years, the Society for Information Management (SIM) has periodically 1 Sirkka Jarvenpaa was the accepting senior editor for this paper. 2 Dr. Wetherbe is also FedEx Professor of Excellence at the University of Memphis. surveyed its members to determine the most critical issues in IS management. Again in 1994-95, SIM institutional and board members were asked to consider what they felt were the most critical issues facing IS executives over the next three to five years. Signaling an evolutionary shift in IS management, this study shows that business relationship issues have declined in importance compared to technology infrastructure issues. For IS executives and general managers, the key issue framework suggests some general directions for emphasis and provides a coarse measure for benchmarking their own concerns against those of their peers. The results of this study also impact educational missions in teaching and research to the extent that they need to be sensitive to the views of practicing fS executives.

The c2 domain calcium-binding motif : structural and functional diversity

Abstract: The C2 domain is a Ca(2+)-binding motif of approximately 130 residues in length originally identified in the Ca(2+)-dependent isoforms of protein kinase C. Single and multiple copies of C2 domains have been identified in a growing number of eukaryotic signalling proteins that interact with cellular membranes and mediate a broad array of critical intracellular processes, including membrane trafficking, the generation of lipid-second messengers, activation of GTPases, and the control of protein phosphorylation. As a group, C2 domains display the remarkable property of binding a variety of different ligands and substrates, including Ca2+, phospholipids, inositol polyphosphates, and intracellular proteins. Expanding this functional diversity is the fact that not all proteins containing C2 domains are regulated by Ca2+, suggesting that some C2 domains may play a purely structural role or may have lost the ability to bind Ca2+. The present review summarizes the information currently available regarding the structure and function of the C2 domain and provides a novel sequence alignment of 65 C2 domain primary structures. This alignment predicts that C2 domains form two distinct topological folds, illustrated by the recent crystal structures of C2 domains from synaptotagmin 1 and phosphoinositide-specific phospholipase C-delta 1, respectively. The alignment highlights residues that may be critical to the C2 domain fold or required for Ca2+ binding and regulation.

An atmospheric tape recorder: The imprint of tropical tropopause temperatures on stratospheric water vapor

Abstract: We describe observations of tropical stratospheric water vapor q that show clear evidence of large-scale upward advection of the signal from annual fluctuations in the effective "entry mixing ratio" qE of air entering the tropical stratosphere. In other words, air is "marked," on emergence above the highest cloud tops, like a signal recorded on an upward moving magnetic tape. We define qE as the mean water vapor mixing ratio, at the tropical tropopause, of air that will subsequently rise and enter the stratospheric "overworld" at about 400 K. The observations show a systematic phase lag, increasing with altitude, between the annual cycle in qE and the annual cycle in q at higher altitudes. The observed phase lag agrees with the phase lag calculated assuming advection by the transformed Eulerian-mean vertical velocity of a qE crudely estimated from 100-hPa temperatures, which we use as a convenient proxy for tropopause temperatures. The phase agreement confirms the overall robustness of the calculation and strongly supports the tape recorder hypothesis. Establishing a quantitative link between qE and observed tropopause temperatures, however, proves difficult because the process of marking the tape depends subtly on both small- and large-scale processes. The tape speed, or large-scale upward advection speed, has a substantial annual variation and a smaller variation due to the quasi-biennial oscillation, which delays or accelerates the arrival of the signal by a month or two in the middle stratosphere. As the tape moves upward, the signal is attenuated with an e-folding time of about 7 to 9 months between 100 and 50 hPa and about 15 to 18 months between 50 and 20 hPa, constraining possible orders of magnitude both of vertica.1 diffusion Kand of ra.tes of mixing in from the extratropics. For instance, if there were no mixing in, then Kwould be in the range 0.03-0.09 ms-; this is an upper bound on Ifs.

Carotenoids 3: in vivo function of carotenoids in higher plants.

Abstract: The function of the long-chain, highly unsaturated carotenoids of higher plants in photoprotection is becoming increasingly well understood, while at the same time their function in other processes, such as light collection, needs to be reexamined. Recent progress in this area has been fueled by more accurate determinations of the photophysical properties of these molecules, as well as extensive characterization of the physiology and ecology of a particular group of carotenoids, those of the xanthophyll cycle, that play a key role in the photoprotection of photosynthesis under environmental stress. The deepoxidized xanthophylls zeaxanthin and antheraxanthin, together with a low pH within the photosynthetic membrane, facilitate the harmless dissipation of excess excitation energy directly within the light-collecting chlorophyll antennae. Evidence for this function as well as current contrasting hypotheses concerning its molecular mechanism are reviewed. In addition, the acclimation of the xanthophyll cycle content and composition of leaves to contrasting environments with different demands for photoprotection is summarized.

Learning from texts: Effects of prior knowledge and text coherence

Abstract: Two experiments, theoretically motivated by the construction‐integration model of comprehension (W. Kintsch, 1988), investigated effects of prior knowledge on learning from high‐ and low‐coherence history texts. In Experiment 1, participants’ comprehension was examined through free recall, multiple‐choice questions, and a keyword sorting task. An advantage was found for the high‐coherence text on recall and multiple‐choice questions. However, high‐knowledge readers performed better on the sorting task after reading the low‐coherence text. In Experiment 2, participants’ comprehension was examined through open‐ended questions and the sorting task both immediately and after a 1‐week delay. Little effect of delay was found, and the previous sorting task results failed to replicate. As predicted, high‐knowledge readers performed better on the open‐ended questions after reading the low‐coherence text. Reading times from both experiments indicated that the low‐coherence text requires more inference processes. Th...

Cool-skin and warm-layer effects on sea surface temperature

Abstract: To obtain bulk surface flux estimates approaching the ±10 W m−2 accuracy desired for the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (COARE) program, bulk water temperature data from ships and buoys must be corrected for cool-skin and diurnal warm-layer effects. In this paper we describe two simple scaling models to estimate these corrections. The cool-skin model is based on the standard Saunders [1967] treatment, including the effects of solar radiation absorption, modified to include both shear-driven and convectively driven turbulence through their relative contributions to the near-surface turbulent kinetic energy dissipation rate. Shear and convective effects are comparable at a wind speed of about 2.5 m s−1. For the R/V Moana Wave COARE data collected in the tropical western Pacific, the model gives an average cool skin of 0.30 K at night and an average local noon value of 0.18 K. The warm-layer model is based on a single-layer scaling version of a model by Price et al. [1986]. In this model, once solar heating of the ocean exceeds the combined cooling by turbulent scalar heat transfer and net longwave radiation, then the main body of the mixed layer is cut off from its source of turbulence. Thereafter, surface inputs of heat and momentum are confined to a depth DT that is determined by the subsequent integrals of the heat and momentum. The model assumes linear profiles of temperature-induced and surface-stress-induced current in this “warm layer.” The model is shown to describe the peak afternoon warming and diurnal cycle of the warming quite accurately, on average, with a choice of a critical Richardson number of 0.65. For a clear day with a 10-m wind speed of 1 m s−1, the peak afternoon warming is about 3.8 K with a warm-layer depth of 0.7 m, decreasing to about 0.2 K and 19 m at a wind speed of 7 m s−1. For an average over 70 days sampled during COARE, the cool skin increases the average atmospheric heat input to the ocean by about 11 W m−2; the warm layer decreases it by about 4 W m−2 (but the effect can be 50 W m−2 at midday).

VIS: A System for Verification and Synthesis

Abstract: ion Manual abstraction can be performed by giving a file containing the names of variables to abstract. For each variable appearing in the file, a new primary input node is created to drive all the nodes that were previously driven by the variable. Abstracting a net effectively allows it to take any value in its range, at every clock cycle. Fair CTL model checking and language emptiness check VIS performs fair CTL model checking under Buchi fairness constraints. In addition, VIS can perform language emptiness checking by model checking the formula EG true. The language of a design is given by sequences over the set of reachable states that do not violate the fairness constraint. The language emptiness check can be used to perform language containment by expressing the set of bad behaviors as another component of the system. If model checking or language emptiness fail, VIS reports the failure with a counterexample, (i.e., behavior seen in the system that does not satisfy the property for model checking, or valid behavior seen in the system for language emptiness). This is called the “debug” trace. Debug traces list a set of states that are on a path to a fair cycle and fail the CTL formula. Equivalence checking VIS provides the capability to check the combinational equivalence of two designs. An important usage of combinational equivalence is to provide a sanity check when re-synthesizing portions of a network. VIS also provides the capability to test the sequential equivalence of two designs. Sequential verification is done by building the product finite state machine, and checking whether a state where the values of two corresponding outputs differ, can be reached from the set of initial states of the product machine. If this happens, a debug trace is provided. Both combinational and sequential verification are implemented using BDD-based routines. Simulation VIS also provides traditionaldesign verification in the form of a cycle-based simulator that uses BDD techniques. Since VIS performs both formal verification and simulation using the same data structures, consistency between them is ensured. VIS can generate random input patterns or accept user-specified input patterns. Any subtree of the specified hierarchy may be simulated.

Genetic analysis of ageing: Role of oxidative damage and environmental stresses

Abstract: Evolutionary theory predicts substantial interspecific and intraspecific differences in the proximal mechanisms of ageing. Our goal here is to seek evidence for common (‘public’) mechanisms among diverse organisms amenable to genetic analysis. Oxidative damage is a candidate for such a public mechanism of ageing. Long-lived strains are relatively resistant to different environmental stresses. The extent to which these stresses produce oxidative damage remains to be established.