Showing papers by "Arizona State University published in 2002"

A comparison of methods to test mediation and other intervening variable effects.

Abstract: A Monte Carlo study compared 14 methods to test the statistical significance of the intervening variable effect. An intervening variable (mediator) transmits the effect of an independent variable to a dependent variable. The commonly used R. M. Baron and D. A. Kenny (1986) approach has low statistical power. Two methods based on the distribution of the product and 2 difference-in-coefficients methods have the most accurate Type I error rates and greatest statistical power except in 1 important case in which Type I error rates are too high. The best balance of Type I error and statistical power across all cases is the test of the joint significance of the two effects comprising the intervening variable effect.

Systematic Design of Pore Size and Functionality in Isoreticular MOFs and Their Application in Methane Storage

Abstract: A strategy based on reticulating metal ions and organic carboxylate links into extended networks has been advanced to a point that allowed the design of porous structures in which pore size and functionality could be varied systematically. Metal-organic framework (MOF-5), a prototype of a new class of porous materials and one that is constructed from octahedral Zn-O-C clusters and benzene links, was used to demonstrate that its three-dimensional porous system can be functionalized with the organic groups –Br, –NH2, –OC3H7, –OC5H11, –C2H4, and –C4H4 and that its pore size can be expanded with the long molecular struts biphenyl, tetrahydropyrene, pyrene, and terphenyl. We synthesized an isoreticular series (one that has the same framework topology) of 16 highly crystalline materials whose open space represented up to 91.1% of the crystal volume, as well as homogeneous periodic pores that can be incrementally varied from 3.8 to 28.8 angstroms. One member of this series exhibited a high capacity for methane storage (240 cubic centimeters at standard temperature and pressure per gram at 36 atmospheres and ambient temperature), and others the lowest densities (0.41 to 0.21 gram per cubic centimeter) for a crystalline material at room temperature.

Generalized estimating equations

Abstract: Correlated datasets develop when multiple observations are collected from a sampling unit (e.g., repeated measures of a bank over time, or hormone levels in a breast cancer patient over time), or from clustered data where observations are grouped based on a shared characteristic (e.g., observations on different banks grouped by zip code, or on cancer patients from a specific clinic). The generalized linear model framework for independent data is extended to model correlated data via the introduction of second-order variance components directly into the independent data model's estimating equation. This generalization of the estimating equation from the independence model is thus referred to as a Generalized Estimating Equation (GEE). This article discusses the foundation of GEEs as well as how user-specified correlation structures are accommodated in the model-building process. This article also discusses the relationship and similarity to the underlying generalized linear model framework and we point out alternative approaches to GEEs for modeling correlated data such as fixed-effects models and random-effects models. Keywords: working correlation matrix; sandwich estimate of variance; generalized linear models; subject-specific models; population-averaged models

The Comparative RNA Web (CRW) Site: an online database of comparative sequence and structure information for ribosomal, intron, and other RNAs

Abstract: Background: Comparative analysis of RNA sequences is the basis for the detailed and accurate predictions of RNA structure and the determination of phylogenetic relationships for organisms that span the entire phylogenetic tree. Underlying these accomplishments are very large, wellorganized, and processed collections of RNA sequences. This data, starting with the sequences organized into a database management system and aligned to reveal their higher-order structure, and patterns of conservation and variation for organisms that span the phylogenetic tree, has been collected and analyzed. This type of information can be fundamental for and have an influence on the study of phylogenetic relationships, RNA structure, and the melding of these two fields. Results: We have prepared a large web site that disseminates our comparative sequence and structure models and data. The four major types of comparative information and systems available for the three ribosomal RNAs (5S, 16S, and 23S rRNA), transfer RNA (tRNA), and two of the catalytic intron RNAs (group I and group II) are: (1) Current Comparative Structure Models; (2) Nucleotide Frequency and Conservation Information; (3) Sequence and Structure Data; and (4) Data Access Systems. Conclusions: This online RNA sequence and structure information, the result of extensive analysis, interpretation, data collection, and computer program and web development, is accessible at our Comparative RNA Web (CRW) Site [http://www.rna.icmb.utexas.edu] . In the future, more data and information will be added to these existing categories, new categories will be developed, and additional RNAs will be studied and presented at the CRW Site.

Cascade-based attacks on complex networks.

Abstract: We live in a modern world supported by large, complex networks. Examples range from financial markets to communication and transportation systems. In many realistic situations the flow of physical quantities in the network, as characterized by the loads on nodes, is important. We show that for such networks where loads can redistribute among the nodes, intentional attacks can lead to a cascade of overload failures, which can in turn cause the entire or a substantial part of the network to collapse. This is relevant for real-world networks that possess a highly heterogeneous distribution of loads, such as the Internet and power grids. We demonstrate that the heterogeneity of these networks makes them particularly vulnerable to attacks in that a large-scale cascade may be triggered by disabling a single key node. This brings obvious concerns on the security of such systems.

Strategic alliances as social capital: a multidimensional view

Abstract: Defining social capital in terms of the information benefits available to a firm due to its strategic alliances we present a theory of social capital that conceptualizes it as a multidimensional construct. We draw from the literature to argue that social capital yields three distinctly different kinds of information benefits in the form of information volume, information diversity, and information richness. This extends current theoretical and empirical research by specifying and empirically demonstrating three interrelated yet distinct dimensions of social capital. Firms vary in their levels of social capital not just on their structural position in an alliance network but also in the dynamics that underlie alliance formation and maintenance. More importantly, the different dimensions of social capital theoretically provide differential benefits. We establish the construct validity of our proposed three-dimensional conceptualization of social capital using longitudinal data on the population of strategic alliances formed during the period 1980–94 by firms in the global steel industry. In addition, we establish predictive validity by demonstrating that the information dimensions have differential effects on firm performance, using firm nationality as a contingency. Copyright © 2002 John Wiley & Sons, Ltd.

A gradient analysis of urban landscape pattern: a case study from the Phoenix metropolitan region, Arizona, USA

Abstract: Urbanization is arguably the most dramatic form of land transformation that profoundly influences biological diversity and human life. Quantifying landscape pattern and its change is essential for the monitoring and assessment of ecological consequences of urbanization. Combining gradient analysis with landscape metrics, we attempted to quantify the spatial pattern of urbanization in the Phoenix metropolitan area, Arizona, USA. Several landscape metrics were computed along a 165 km long and 15 km wide transect with a moving window. The research was designed to address four research questions: How do different land use types change with distance away from the urban center? Do different land use types have their own unique spatial signatures? Can urbanization gradients be detected using landscape pattern analysis? How do the urban gradients differ among landscape metrics? The answers to these questions were generally affirmative and informative. The results showed that the spatial pattern of urbanization could be reliably quantified using landscape metrics with a gradient analysis approach, and the location of the urbanization center could be identified precisely and consistently with multiple indices. Different land use types exhibited distinctive, but not necessarily unique, spatial signatures that were dependent on specific landscape metrics. The changes in landscape pattern along the transect have important ecological implications, and quantifying the urbanization gradient, as illustrated in this paper, is an important first step to linking pattern with processes in urban ecological studies.

Towards an ecological understanding of biological nitrogen fixation

Abstract: N limitation to primary production and other ecosystem processes is widespread. To understand the causes and distribution of N limitation, we must understand the controls of biological N fixation. The physiology of this process is reasonably well characterized, but our understanding of ecological controls is sparse, except in a few cultivated ecosystems. We review information on the ecological controls of N fixation in free-living cyanobacteria, vascular plant symbioses, and heterotrophic bacteria, with a view toward developing improved conceptual and simulation models of ecological controls of biological N fixation.

The Role of Agriculture in Development

Abstract: A longstanding question in economics is why some countries are so much richer than others. Today, for example, income per capita in the world's richest countries is roughly thirty-five times greater than it is in the world's poorest countries. Recent work argues that the proximate cause of the disparity is that today's poor countries began the process of industrialization much later and that this process is slow. In this paper we argue that a model of structural transformation provides a useful theory of both why industrialization occurs at different dates, and why it proceeds slowly. A key implication of this model is that growth in agricultural productivity is central to development, a message that also appears prominently in the traditional development literature.

Conflicting Voices: The Effects of Institutional Ownership Heterogeneity and Internal Governance on Corporate Innovation Strategies

Abstract: Examining the relationship between governance and corporate innovation strategies, we found, in opposition to the assumption that owners have a unified voice, differences among governance constitue

The necessities and luxuries of mate preferences: testing the tradeoffs.

Abstract: Social exchange and evolutionary models of mate selection incorporate economic assumptions but have not considered a key distinction between necessities and luxuries. This distinction can clarify an apparent paradox: Status and attractiveness, though emphasized by many researchers, are not typically rated highly by research participants. Three studies supported the hypothesis that women and men first ensure sufficient levels of necessities in potential mates before considering many other characteristics rated as more important in prior surveys. In Studies 1 and 2, participants designed ideal long-term mates, purchasing various characteristics with 3 different budgets. Study 3 used a mate-screening paradigm and showed that people inquire 1st about hypothesized necessities. Physical attractiveness was a necessity to men, status and resources were necessities to women, and kindness and intelligence were necessities to both.

Hormone replacement therapy and incidence of Alzheimer disease in older women: the Cache County Study.

Abstract: ContextPrevious studies have shown a sex-specific increased risk of Alzheimer disease (AD) in women older than 80 years. Basic neuroscience findings suggest that hormone replacement therapy (HRT) could reduce a woman's risk of AD. Epidemiologic findings on AD and HRT are mixed.ObjectiveTo examine the relationship between use of HRT and risk of AD among elderly women.Design, Setting, and ParticipantsProspective study of incident dementia among 1357 men (mean age, 73.2 years) and 1889 women (mean age, 74.5 years) residing in a single county in Utah. Participants were first assessed in 1995-1997, with follow-up conducted in 1998-2000. History of women's current and former use of HRT, as well as of calcium and multivitamin supplements, was ascertained at the initial contact.Main Outcome MeasureDiagnosis of incident AD.ResultsThirty-five men (2.6%) and 88 women (4.7%) developed AD between the initial interview and time of the follow-up (3 years). Incidence among women increased after age 80 years and exceeded the risk among men of similar age (adjusted hazard ratio [HR], 2.11; 95% confidence interval [CI], 1.22-3.86). Women who used HRT had a reduced risk of AD (26 cases among 1066 women) compared with non-HRT users (58 cases among 800 women) (adjusted HR, 0.59; 95% CI, 0.36-0.96). Risk varied with duration of HRT use, so that a woman's sex-specific increase in risk disappeared entirely with more than 10 years of treatment (7 cases among 427 women). Adjusted HRs were 0.41 (95% CI, 0.17-0.86) for HRT users compared with nonusers and 0.77 (95% CI, 0.31-1.67) compared with men. No similar effect was seen with calcium or multivitamin use. Almost all of the HRT-related reduction in incidence reflected former use of HRT (9 cases among 490 women; adjusted HR, 0.33 [95% CI, 0.15-0.65]). There was no effect with current HRT use (17 cases among 576 women; adjusted HR, 1.08 [95% CI, 0.59-1.91]) unless duration of treatment exceeded 10 years (6 cases among 344 women; adjusted HR, 0.55 [95% CI, 0.21-1.23]).ConclusionsPrior HRT use is associated with reduced risk of AD, but there is no apparent benefit with current HRT use unless such use has exceeded 10 years.

A Review of Multiple-Choice Item-Writing Guidelines for Classroom Assessment

Abstract: A taxonomy of 31 multiple-choice item-writing guidelines was validated through a logical process that included two sources of evidence: the consensus achieved from reviewing what was found in 27 textbooks on educational testing and the results of 27 research studies and reviews published since 1990. This taxonomy is mainly intended for classroom assessment. Because textbooks have potential to educate teachers and future teachers, textbook writers are encouraged to consider these findings in future editions of their textbooks. This taxonomy may also have usefulness for developing test items for large-scale assessments. Finally, research on multiple-choice item writing is discussed both from substantive and methodological viewpoints.

A sensitive period for the development of the central auditory system in children with cochlear implants: implications for age of implantation.

Abstract: ObjectiveThe aim of the present experiment was to assess the consequences of cochlear implantation at different ages on the development of the human central auditory system.DesignOur measure of the maturity of central auditory pathways was the latency of the P1 cortical auditory evoked potential. Be

Key issues and research priorities in landscape ecology: An idiosyncratic synthesis

Abstract: Landscape ecology has made tremendous progress in recent decades, but as a rapidly developing discipline it is faced with new problems and challenges. To identify the key issues and research priorities in landscape ecology, a special session entitled “Top 10 List for Landscape Ecology in the 21st Century” was organized at the 16th Annual Symposium of the US Regional Association of International Association of Landscape Ecology, held at Arizona State University (Tempe, Arizona, USA) during April 25–29, 2001. A group of leading landscape ecologists were invited to present their views. This paper is intended to be a synthesis, but not necessarily a consensus, of the special session. We have organized the diverse and wide-ranging perspectives into six general key issues and 10 priority research topics. The key issues are: (1) interdisciplinarity or transdisciplinarity, (2) integration between basic research and applications,(3) Conceptual and theoretical development, (4) education and training, (5)international scholarly communication and collaborations, and (6) outreach and communication with the public and decision makers. The top 10 research topics are: (1) ecological flows in landscape mosaics, (2) causes, processes, and consequences of land use and land cover change, (3) nonlinear dynamics and landscape complexity, (4) scaling, (5) methodological development, (6) relating landscape metrics to ecological processes, (7) integrating humans and their activities into landscape ecology, (8) optimization of landscape pattern, (9)landscape sustainability, and (10) data acquisition and accuracy assessment. We emphasize that, although this synthesis was based on the presentations at the“Top 10 List” session, it is not a document that has been agreed upon by each and every participant. Rather, we believe that it is reflective of the broad-scale vision of the collective as to where landscape ecology is now and where it may be going in future.

Binge drinking trajectories from adolescence to emerging adulthood in a high-risk sample: predictors and substance abuse outcomes.

Abstract: This study describes binge drinking trajectories from adolescence to emerging adulthood in 238 children of alcoholics and 208 controls. Mixture modeling identified three trajectory groups: early-heavy (early onset, high frequency), late-moderate (later onset, moderate frequency), and infrequent (early onset, low frequency). Nonbingers were defined a priori. The early-heavy group was characterized by parental alcoholism and antisociality, peer drinking, drug use, and (for boys) high levels of externalizing behavior, but low depression. The infrequent group was elevated in parent alcoholism and (for girls) adolescent depression, whereas the nonbinger and late-moderate groups showed the most favorable adolescent psychosocial variables. All 3 drinking trajectory groups raised risk for later substance abuse or dependence compared with the nonbingers, with the early-heavy group at highest risk.

Connectivity, fragmentation, and extinction risk in dendritic metapopulations

Abstract: Neither linear nor two-dimensional frameworks may be the most appropriate for fish and other species constrained to disperse within river-creek systems. In particular, the hierarchical, dendritic structures of riverine networks are not well captured by existing spatial models. Here I use a simple geometric model and metapopulation modeling to make three points concerning the ecological consequences of dendritic landscapes. First, con- nectivity patterns of river-creek networks differ from linear landscapes, and these differ- ences in connectivity can either enhance or reduce metapopulation persistence compared to linear systems, depending on the details of dispersal. Second, habitat fragmentation in dendritic landscapes has different (and arguably more severe) consequences on fragment size than in either linear or two-dimensional systems, resulting in both smaller fragments and higher variance in fragment size. Third, dendritic landscapes can induce striking mis- matches between the geometry of dispersal and the geometry of disturbance, and as is the case for arid-lands fishes, such mismatches can be important for population persistence.

Latin Hypercube Sampling and the Propagation of Uncertainty in Analyses of Complex Systems

Abstract: The following techniques for uncertainty and sensitivity analysis are briefly summarized: Monte Carlo analysis, differential analysis, response surface methodology, Fourier amplitude sensitivity test, Sobol’ variance decomposition, and fast probability integration. Desirable features of Monte Carlo analysis in conjunction with Latin hypercube sampling are described in discussions of the following topics: (i) properties of random, stratified and Latin hypercube sampling, (ii) comparisons of random and Latin hypercube sampling, (iii) operations involving Latin hypercube sampling (i.e. correlation control, reweighting of samples to incorporate changed distributions, replicated sampling to test reproducibility of results), (iv) uncertainty analysis (i.e. cumulative distribution functions, complementary cumulative distribution functions, box plots), (v) sensitivity analysis (i.e. scatterplots, regression analysis, correlation analysis, rank transformations, searches for nonrandom patterns), and (vi) analyses involving stochastic (i.e. aleatory) and subjective (i.e. epistemic) uncertainty. Published by Elsevier Science Ltd.

Utility of pedometers for assessing physical activity: convergent validity.

Abstract: Valid assessment of physical activity is important to researchers and practitioners interested in surveillance, screening, programme evaluation and intervention. The validity of an assessment instrument is commonly considered its most important attribute. Convergent validity is the extent to which an instrument’s output is associated with that of other instruments intended to measure the same exposure of interest. A systematic review of the literature produced 25 articles directly relevant to the question of convergent validity of pedometers against accelerometers, observation, and self-reported measures of physical activity. Reported correlations were pooled and a median r-value was computed. Pedometers correlate strongly (median r = 0.86) with different accelerometers (specifically uniaxial accelerometers) depending on the specific instruments used, monitoring frame and conditions implemented, and the manner in which the outputs are expressed. Pedometers also correlate strongly (median r = 0.82) with time in observed activity. Time in observed inactivity correlated negatively with pedometer outputs (median r = -0.44). The relationship with observed steps taken depended upon monitoring conditions and speed of walking. The highest agreement was apparent during ambulatory activity (running, walking) or during sitting (when both observation and pedometers would register few steps taken). There was consistent evidence of reduced accuracy during slow walking. Pedometers correlate moderately with different measures of energy expenditure (median r = 0.68). The relationship between pedometer outputs and energy expenditure is complicated by the use of many different direct and indirect measures of energy expenditure and population samples. Concordance with self-reported physical activity (median r = 0.33) varied depending upon the self-report instrument used, individuals assessed, and how pedometer outputs are expressed (e.g. steps, distance travelled, energy expenditure). Pedometer output has an inverse relationship with reported time spent sitting (r = -0.38). The accumulated evidence herein provides ample support that the simple and inexpensive pedometer is a valid option for assessing physical activity in research and practice.

An inverted continental Moho and serpentinization of the forearc mantle

Abstract: Volatiles that are transported by subducting lithospheric plates to depths greater than 100 km are thought to induce partial melting in the overlying mantle wedge, resulting in arc magmatism and the addition of significant quantities of material to the overlying lithosphere. Asthenospheric flow and upwelling within the wedge produce increased lithospheric temperatures in this back-arc region, but the forearc mantle (in the corner of the wedge) is thought to be significantly cooler. Here we explore the structure of the mantle wedge in the southern Cascadia subduction zone using scattered teleseismic waves recorded on a dense portable array of broadband seismometers. We find very low shear-wave velocities in the cold forearc mantle indicated by the exceptional occurrence of an 'inverted' continental Moho, which reverts to normal polarity seaward of the Cascade arc. This observation provides compelling evidence for a highly hydrated and serpentinized forearc region, consistent with thermal and petrological models of the forearc mantle wedge. This serpentinized material is thought to have low strength and may therefore control the down-dip rupture limit of great thrust earthquakes, as well as the nature of large-scale flow in the mantle wedge.

Cognitive theories of early gender development.

Abstract: How individuals develop a “gendered” self and gender-typed differentiation has intrigued researchers of human behavior for as long as social development has been a field of empirical study. Initially, observations of clear gender typing in children as young as 5 years old led researchers to examine how socialization processes in the home might contribute to this early acquisition of gender-linked behavior (e.g., Sears, Maccoby, & Levin, 1957). In 1966, several important theories of gender development, including Kohlberg’s cognitive– developmental approach and Mischel’s social learning approach, were outlined in Maccoby’s book on the development of sex differences. In the mid-1970s, a groundbreaking book by Maccoby and Jacklin (1974) broadened the discussion about the etiology of sex differences and gender typing and questioned the significance of socialization processes, thereby invigorating the field and generating considerable controversy. In the 1980s, Huston (1983, 1985) called for researchers to develop a more integrative, comprehensive approach to the study of gender development. This integration was to include consideration of the many facets of gender that needed investigation, such as concepts, identity, preferences, and behavior, as well as a wide variety of factors that influence the development of these facets, including biology, cognitions, and social influences. This idea resonated with gender researchers and has been a driving force in the field ever since, leading to an expansion of theoretical approaches and the inclusion of multiple measures in empirical studies. Recently, Bussey and Bandura (1999) presented a social– cognitive theory (SCT) of gender development and differentiation. This theory represents a particular view of how gender-related behavior is acquired and maintained, based on contemporary social learning theory (Bandura, 1986). Because the theory has now integrated cognitive constructs and makes reference to biological underpinnings and sociostructural factors, Bussey and Bandura described their theory as comprehensive and integrative, consistent with Huston’s (1983) proposal, and implied that other theories are invalid and/or no longer necessary. In particular, they were highly critical of previous cognitive approaches to early gender development and proposed that children’s cognitive structures, namely gender identity and stereotype knowledge, play a minor role relative to social forces. One goal of the present article is to rebut these claims. A second goal is to present a contemporary account of the role of cognitive structures in early gender development. We begin with a brief history of the debate between cognitive and social learning theories of gender development. We then examine the contributions and limitations of Bussey and Bandura’s (1999) recent account of gender development. Next, we review the current status of what have historically been the two major cognitive accounts of gender development: cognitive– developmental theory and gender schema theory. We then evaluate the empirical evidence relevant to the major controversies surrounding these views. Given the centrality of early gender development to the cognitive perspective, we then introduce the latest evidence on how infants and toddlers develop the abilities to discriminate the sexes and learn the attributes correlated with sex. Finally, we provide an overview of the essence of cognitive approaches and point to directions for future research.

Sources of variance in daily physical activity levels as measured by an accelerometer.

Abstract: MATTHEWS, C. E., B. E. AINSWORTH, R. W. THOMPSON, and D. R. BASSETT, JR. Sources of variance in daily physical activity levels as measured by an accelerometer. Med. Sci. Sports Exerc., Vol. 34, No. 8, pp. 1376–1381, 2002.PurposeTo examine sources of variance in objective measures of physical

Heterogeneous dynamics in liquids: fluctuations in space and time

Abstract: The disordered nature of glass-forming melts gives rise to non-Arrhenius and non-exponential behaviour of their dynamics. With respect to the microscopic details involved in the structural relaxation, these materials have remained an unsolved puzzle for over a century. The observation of spatial heterogeneity regarding the dynamics provides an important step towards understanding the relation between the macroscopic properties of soft condensed matter and the molecular mechanisms involved. On the other hand, dynamic heterogeneity is the source of several new questions: What is the length scale and persistence time associated with such clusters of relaxation time? What is the signature of heterogeneity at high temperatures and in the glassy state? How do these features depend on the particular material and on the correlation function used for probing these heterogeneities? This work attempts to review the various approaches to heterogeneous dynamics and the generally accepted results, as well as some controversial issues. Undoubtedly, heterogeneity has provoked a number of novel experimental techniques targeted at studying glass-forming liquids at the molecular level. It will be emphasized that the picture of heterogeneity is a requirement for rationalizing an increasing number of experimental observations rather than just an alternative model for the dynamics of molecules.

When Web Pages Influence Choice: Effects of Visual Primes on Experts and Novices

Abstract: This article extends the idea that priming can influence preferences by making selected attributes focal. Our on-line experiments manipulate the background pictures and colors of a Web page, affecting consumer product choice. We demonstrate that these effects occur for both experts and novices, albeit by different mechanisms. For novices, priming drives differences in external search that, in turn, drive differences in choice. For experts, we observe differences in choice that are not mediated by changes in external search. These findings confirmed that on-line atmospherics in electronic environments could have a significant influence on consumer choice.

Liquid fragility and the glass transition in water and aqueous solutions.

Abstract: In a review of the present title, the first requirement is to ensure that the title words are understood. While the term “glass” is broadly familiar, and the origin of the “glass transition” in terms of the crossing of system and experimental time scales is generally agreed upon, there are at least three different definitions of the material property “glass transition temperature” (Tg) in current use.1,2 Furthermore, these may differ from each other by as much as 50 K in certain higher Tg cases. The difference is a consequence of the magnitude of the “glass transformation range” within which the Tg is variously defined. This magnitude, the “width of the glass transition”, can vary greatly from system to system, for reasons discussed below. Since the quantity Tg will recur frequently in this review, it is necessary to deal adequately with the definition problem, and this will be done by reference to Figures 1 and 2 below. Depending on the liquid in question, glass transitions may be observed occurring over an enormous range in temperature, from below 50 K to above 1500 K. The reason for this range is clearly to do with the strength of the interparticle interactions, i.e., the “bonds” that are being broken as the particles rearrange. However, the reason that some glass transitions are “sharp” (meaning narrow glass transformation range, or “transition width”) and others very spread out in temperature is not so clear. It is largely to do with the “fragility” of the glassformer, but may C. A. Angell was born in Canberra, Australia, and studied chemistry and metallurgy at the University of Melbourne. After working on molten salts with J. O’M Bockris at the University of Pennsylvania for two years, he became the Stanley Elmore Fellow at Imperial College of Science, London, where he completed his Ph.D. under the direction of John W. Tomlinson. There he was awarded the Armstrong medal for graduate research 1959− 1961. He returned to Australia as lecturer in chemical metallurgy but after two years came back to the U.S. as a post-doc with Dieter Gruen at Argonne National Laboratory. In 1966, he joined Purdue University as Assistant Professor, becoming full Professor in 1971. In 1989, he moved to Arizona State University where he is now Regents’ Professor of Chemistry and Biochemistry. He has enjoyed and profited from sabbatical leaves at the University of Amsterdam, the Australian National University, Institute Laue-Langevin, Grenoble, the Ecole de Physique et Chemie Industrielle, Paris, University of Rennes-Beaulieu, Sydney University, and the University of Rome. His research interests range from rechargeable lithium batteries and fuel cells, through the phenomenology of the glass transition and the origin of fragility in liquids, to the anomalous properties of water and geochemical fluids and their relation to polyamorphism. Currently, he is focusing on the annealing behavior of hyperquenched liquids and solutions, particularly denatured protein solutions, with a sideline on nanoporous network glasses as gas storage media. 2627 Chem. Rev. 2002, 102, 2627−2650