Showing papers by "University of Illinois at Urbana–Champaign published in 1994"

Design Patterns: Elements of Reusable Object-Oriented Software

Abstract: The book is an introduction to the idea of design patterns in software engineering, and a catalog of twenty-three common patterns. The nice thing is, most experienced OOP designers will find out they've known about patterns all along. It's just that they've never considered them as such, or tried to centralize the idea behind a given pattern so that it will be easily reusable.

Review of particle properties.

Abstract: This biennial Review summarizes much of Particle Physics. Using data from previous editions, plus 2205 new measurements from 667 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. This edition features expanded coverage of CP violation in B mesons and of neutrino oscillations. For the first time we cover searches for evidence of extra dimensions (both in the particle listings and in a new review). Another new review is on Grand Unified Theories. A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review. All tables, listings, and reviews (and errata) are also available on the Particle Data Group website: http://pdg.lbl.gov.

Carbon pools and flux of global forest ecosystems.

Abstract: Forest systems cover more than 4.1 x 109 hectares of the Earth9s land area. Globally, forest vegetation and soils contain about 1146 petagrams of carbon, with approximately 37 percent of this carbon in low-latitude forests, 14 percent in mid-latitudes, and 49 percent at high latitudes. Over two-thirds of the carbon in forest ecosystems is contained in soils and associated peat deposits. In 1990, deforestation in the low latitudes emitted 1.6 ± 0.4 petagrams of carbon per year, whereas forest area expansion and growth in mid- and high-latitude forest sequestered 0.7 ± 0.2 petagrams of carbon per year, for a net flux to the atmosphere of 0.9 ± 0.4 petagrams of carbon per year. Slowing deforestation, combined with an increase in forestation and other management measures to improve forest ecosystem productivity, could conserve or sequester significant quantities of carbon. Future forest carbon cycling trends attributable to losses and regrowth associated with global climate and land-use change are uncertain. Model projections and some results suggest that forests could be carbon sinks or sources in the future.

A niched Pareto genetic algorithm for multiobjective optimization

Abstract: Many, if not most, optimization problems have multiple objectives. Historically, multiple objectives have been combined ad hoc to form a scalar objective function, usually through a linear combination (weighted sum) of the multiple attributes, or by turning objectives into constraints. The genetic algorithm (GA), however, is readily modified to deal with multiple objectives by incorporating the concept of Pareto domination in its selection operator, and applying a niching pressure to spread its population out along the Pareto optimal tradeoff surface. We introduce the Niched Pareto GA as an algorithm for finding the Pareto optimal set. We demonstrate its ability to find and maintain a diverse "Pareto optimal population" on two artificial problems and an open problem in hydrosystems. >

Assessing Subjective Well-Being: Progress and Opportunities

Abstract: Subjective well-being (SWB) comprises people's longer-term levels of pleasant affect, lack of unpleasant affect, and life satisfaction. It displays moderately high levels of cross-situational consistency and temporal stability. Self-report measures of SWB show adequate validity, reliability, factor invariance, and sensitivity to change. Despite the success of the measures to date, more sophisticated approaches to defining and measuring SWB are now possible. Affect includes facial, physiological, motivational, behavioral, and cognitive components. Self-reports assess primarily the cognitive component of affect, and thus are unlikely to yield a complete picture of respondents' emotional lives. For example, denial may influence self-reports of SWB more than other components. Additionally, emotions are responses which vary on a number of dimensions such as intensity, suggesting that mean levels of affect as captured by existing measures do not give a complete account of SWB. Advances in cognitive psychology indicate that differences in memory retrieval, mood as information, and scaling processes can influence self-reports of SWB. Finally, theories of communication alert us to the types of information that are likely to be given in self-reports of SWB. These advances from psychology suggest that a multimethod approach to assessing SWB will create a more comprehensive depiction of the phenomenon. Not only will a multifaceted test battery yield more credible data, but inconsistencies between various measurement methods and between the various components of well-being will both help us better understand SWB indictors and group differences in well-being. Knowledge of cognition, personality, and emotion will also aid in the development of sophisticated theoretical definitions of subjective well-being. For example, life satisfaction is theorized to be a judgment that respondents construct based on currently salient information. Finally, it is concluded that measuring negative reactions such as depression or anxiety give an incomplete picture of people's well-being, and that it is imperative to measure life satisfaction and positive emotions as well.

Three-dimensional alpha shapes

Abstract: Frequently, data in scientific computing is in its abstract form a finite point set in space, and it is sometimes useful or required to compute what one might call the “shape” of the set. For that purpose, this article introduces the formal notion of the family of a-shapes of a finite point set in R3. Each shape is a well-defined polytope, derived from the Delaunay triangulation of the point set, with a parameter a e R controlling the desired level of detail. An algorithm is presented that constructs the entire family of shapes for a given set of size n in time 0(n2), worst case. A robust implementation of the algorithm is discussed, and several applications in the area of scientific computing are mentioned.

Culture and social behavior

Abstract: CHAPTER 1: Introduction: Our Culture Influences Who We Are and Our Understanding of Social BehaviorCHAPTER 2: Why Bother Study Culture-Social Behavior RelationshipsCHAPTER 3: How to Study CulturesCHAPTER 4: The Analysis of Subjective CulturesCHAPTER 5: Some Interesting Differences in Subjective CulturesCHAPTER 6: Cultures Differences in Patterns of Social BehaviorCHAPTER 7: Culture and CommunicationCHAPTER 8: Cultural Differences in Aggression, Helping, Dominance, Conformity, Obedience, and IntimacyCHAPTER 9: Dealing with Diversity and Intercultural RelationsCHAPTER 10: Intercultural Training

A 3D perfectly matched medium from modified maxwell's equations with stretched coordinates

Abstract: A modified set of Maxwell's equations is presented that includes complex coordinate stretching along the three Cartesian coordinates. The added degrees of freedom in the modified Maxwell's equations allow the specification of absorbing boundaries with zero reflection at all angles of incidence and all frequencies. The modified equations are also related to the perfectly matched layer that was presented recently for 2D wave propagation. Absorbing-material boundary conditions are of particular interest for finite-difference time-domain (FDTD) computations on a single-instruction multiple-data (SIMD) massively parallel supercomputer. A 3D FDTD algorithm has been developed on a connection machine CM-5 based on the modified Maxwell's equations and simulation results are presented to validate the approach. © 1994 John Wiley & Sons, Inc.

Hydrogen-enhanced localized plasticity—a mechanism for hydrogen-related fracture

Abstract: The mechanisms of hydrogen-related fracture are briefly reviewed and a few evaluative statements are made about the stress-induced hydride formation, decohesion, and hydrogen-enhanced localized plasticity mechanisms. A more complete discussion of the failure mechanism based on hydrogen-enhanced dislocation mobility is presented, and these observations are related to measurements of the macroscopic flow stress. The effects of hydrogen-induced slip localization on the measured flow stress is discussed. A theory of hydrogen shielding of the interaction of dislocations with elastic stress centres is outlined. It is shown that this shielding effect can account for the observed hydrogen-enhanced dislocation mobility.

An oscillation in the global climate system of period 65–70 years

Abstract: IN addition to the well-known warming of ∼0.5 °C since the middle of the nineteenth century, global-mean surface temperature records1–4display substantial variability on timescales of a century or less. Accurate prediction of future temperature change requires an understanding of the causes of this variability; possibilities include external factors, such as increasing greenhouse-gas concentrations5–7 and anthropogenic sulphate aerosols8–10, and internal factors, both predictable (such as El Nino11) and unpredictable (noise12,13). Here we apply singular spectrum analysis14–20 to four global-mean temperature records1–4, and identify a temperature oscillation with a period of 65–70 years. Singular spectrum analysis of the surface temperature records for 11 geographical regions shows that the 65–70-year oscillation is the statistical result of 50–88-year oscillations for the North Atlantic Ocean and its bounding Northern Hemisphere continents. These oscillations have obscured the greenhouse warming signal in the North Atlantic and North America. Comparison with previous observations and model simulations suggests that the oscillation arises from predictable internal variability of the ocean–atmosphere system.

Initial public offerings: International insights

Abstract: This paper discusses evidence on the short-run and long-run performance of companies going public in many countries. Differences in average initial returns are analyzed in terms of binding regulations, contractual mechanisms, and the characteristics of the firms going public. The evidence suggests that the move in recent years by most East Asian countries to reduce regulatory interference in the setting of offering prices should result in less short-run underpricing in the 1990s than in the 1980s. Evidence is presented that companies successfully time their offerings for periods when valuations are high, with investors receiving low returns in the long-run. Implications for investors, issuers, and regulators are discussed.

Interatomic Potentials from First-Principles Calculations: The Force-Matching Method

Abstract: We present a new scheme to extract numerically optimal interatomic potentials from large amounts of data produced by first-principles calculations. The method is based on fitting the potential to ab initio atomic forces of many atomic configurations, including surfaces, clusters, liquids and crystals at finite temperature. The extensive data set overcomes the difficulties encountered by traditional fitting approaches when using rich and complex analytic forms, allowing to construct potentials with a degree of accuracy comparable to that obtained by ab initio methods. A glue potential for aluminium obtained with this method is presented and discussed.

Over-time changes in adjustment and competence among adolescents from authoritative, authoritarian, indulgent, and neglectful families

Abstract: In a previous report, we demonstrated that adolescents' adjustment varies as a function of their parents' style (e.g., authoritative, authoritarian, indulgent, neglectful). This 1-year follow-up was conducted in order to examine whether the observed differences are maintained over time. In 1987, an ethnically and socioeconomically heterogeneous sample of approximately 2,300 14-18-year-olds provided information used to classify the adolescents' families into 1 of 4 parenting style groups. That year, and again 1 year later, the students completed a battery of standardized instruments tapping psychosocial development, school achievement, internalized distress, and behavior problems. Differences in adjustment associated with variations in parenting are either maintained or increase over time. However, whereas the benefits of authoritative parenting are largely in the maintenance of previous levels of high adjustment, the deleterious consequences of neglectful parenting continue to accumulate.

fastDNAml: a tool for construction of phylogenetic trees of DNA sequences using maximum likelihood

Abstract: We have developed a new tool, called fastDNAml, for constructing phylogenetic trees from DNA sequences. The program can be run on a wide variety of computers ranging from Unix workstations to massively parallel systems, and is available from the Ribosomal Database Project (RDP) by anonymous FTP. Our program uses a maximum likelihood approach and is based on version 3.3 of Felsenstein's dnaml program. Several enhancements, including algorithmic changes, significantly improve performance and reduce memory usage, making it feasible to construct even very large trees. Trees containing 40-100 taxa have been easily generated, and phylogenetic estimates are possible even when hundreds of sequences exist. We are currently using the tool to construct a phylogenetic tree based on 473 small subunit rRNA sequences from prokaryotes.

Rape Myths In Review

Abstract: Theories of sexual aggression and victimization have increasingly emphasized the role of rape myths in the perpetuation of sexual assault. Rape myths are attitudes and generally false beliefs about...

Two functional components of the hippocampal memory system

Abstract: There is considerable evidence that the hippocampal system contributes both to (1) the temporary maintenance of memories and to (2) the processing of a particular type of memory representation. The findings on amnesia suggest that these two distinguishing features of hippocampal memory processing are orthogonal. Together with anatomical and physiological data, the neuropsychological findings support a model of cortico-hippocampal interactions in which the temporal and representational properties of hippocampal memory processing are mediated separately. We propose that neocortical association areas maintain shortterm memories for specific items and events prior to hippocampal processing as well as providing the final repositories of long-term memory. The parahippocampal region supports intermediate-term storage of individual items, and the hippocampal formation itself mediates an organization of memories according to relevant relationships among items. Hippocampal-cortical interactions produce (i) strong and persistent memories for events, including their constituent elements and the relationships among them, and (ii) a capacity to express memories flexibly across a wide range of circumstances.

Group-specific 16S rRNA hybridization probes to describe natural communities of methanogens

Abstract: Eight oligonucleotides which are complementary to conserved tracts of 16S rRNA from phylogenetically defined groups of methanogens were designed and characterized for use as hybridization probes for studies in environmental and determinative microbiology. The target-group specificity and temperature of dissociation for each probe were characterized. In general, the probes were very specific for the target methanogens and did not hybridize to the rRNAs of nontarget methanogens. Together, the eight probes circumscribe methanogens now represented in pure culture (with the exception of members of the family Methanothermaceae). Three probes are order specific; two identify members of the order Methanobacteriales, and one is specific for the order Methanococcales. The fourth probe encompasses three families belonging to the order Methanomicrobiales, the third order within the current classification. The fifth probe is specific for the remaining family within this order (Methanosarcinaceae). Three additional probes encompass different genera within the Methanosarcinaceae.

Trust, self-confidence, and operators' adaptation to automation

Abstract: The increasing use of automation to supplant human intervention in controlling complex systems changes the operators' role from active controllers (directly involved with the system) to supervisory controllers (managing the use of different degrees of automatic and manual control). This paper examines the relationship between trust in automatic controllers, self-confidence in manual control abilities, and the use of automatic controllers in operating a simulated semi-automatic pasteurization plant. Trust, combined with self-confidence, predicted the operators' allocation strategy. A Multitrait-multimethod matrix and logit functions showed how trust and self-confidence relate to the use of automation. An ARMAV time series model of the dynamic interaction of trust and self-confidence, combined with individual biases, accounted for 60.9-86.5% of the variance in the use of the three automatic controllers. In general, automation is used when trust exceeds self-confidence, and manual control when the opposite is true. Since trust and self-confidence are two factors that guide operators' interactions with automation, the design of supervisory control systems should include provisions to ensure that operators' trust reflects the capabilities of the automation and operators' self-confidence reflects their abilities to control the system manually.

The winds of (evolutionary) change: breathing new life into microbiology.

Abstract: To date, over 1500 prokaryotes have been characterized by small subunit rRNA sequencing and molecular phylogeny has had an equally profound effect on our understanding of relationship among eukaryotic microorganisms. The universal phylogenetic tree readily shows however how artificial the strong distinction between the eukaryote and prokaryotes has become. The split between the Archaea and the Bacteria is now recognized as the primary phylogenetic division and that the Eucarya have branched from the same side of the tree as the Archaea. Both prokaryotic domains would seem to be of thermophilic origin suggesting that life arose in a very warm environment. Among the Archaea, all of the Crenarchaeota cultured to date are thermophiles, and the deepest euryarchaeal branchings are represented exclusively by thermophiles. Among the Bacteria, the deepest known branchings are again represented exclusively by thermophiles, and thermophilia is widely scattered throughout the domain. The Archaea comprise a small number of quite disparate phenotypes that grow in unusual niches. All are obligate or facultative anaerobes. All cultured crenarchaeotes are thermophilic, some even growing optimally above the normal boiling temperature of water. The Archaeoglobales are sulfate reducers growing at high temperatures. The extreme halophiles grow only in highly saline environments. The methanogensmore » are confined to a variety of anaerobic niches, often thermophilic. The Bacteria, on the other hand, are notable as being the source of life`s photosynthetic capacity. Five kingdoms of bacteria contain photosynthetic species; and each of the five manifests a distinct type of (chlorophyll-based) photosynthesis.« less

Parents' and Children's Adiposity and Eating Style

Abstract: Objective. To investigate children9s ability to self-regulate energy intake and to determine whether individual differences in the precision of food intake regulation are related to children9s anthropometric measures. We collected information pertaining to parental adiposity and dieting practices, as well as mothers9 child-feeding practices. Of special interest was the degree of control imposed by mothers over their children9s food intake. Our intent was to explore whether these variables might influence children9s regulation of energy intake. Subjects and setting. Seventy-seven 3-5-year-old children who attended a university preschool setting and their parents participated in this experiment. Measurements and main results. Children completed controlled, two-part meals used to estimate their ability to adjust food intake in response to changes in caloric density of the diet. An eating index, reflecting children9s precision in the ability to regulate energy intake, was correlated to children9s anthropometric measures. These correlations provided evidence for a relation between children9s body fat stores and their responsiveness to caloric density cues: Pearson correlation coefficients revealed that children with greater body fat stores were less able to regulate energy intake accurately. The best predictor of children9s ability to regulate energy intake was parental control in the feeding situation: mothers who were more controlling of their children9s food intake had children who showed less ability to self-regulate energy intake (r = -.67, P Conclusions. These findings suggest that the optimal environment for children9s development of self-control of energy intake is that in which parents provide healthy food choices but allow children to assume control of how much they consume.

Relative importance of photosynthetic traits and allocation patterns as correlates of seedling shade tolerance of 13 tropical trees.

Abstract: Among 13 tropical tree species on Barro Colorado Island, species with high seedling mortality rates during the first year in shade had higher reltive growth rates (RGR) from germination to 2 months in both sun (23% full sun) and shade [2%, with and without lowered red: far red (R:FR) ratio] than shade tolerant species. Species with higher RGR in sun also had higher RGR in shade. These interspecific trends could be explained by differences in morphological traits and allocation paterns among species. Within each light regime, seedlings of shade-intolerant species had lower root: shoot ratios, higher leaf mass per unit area, and higher leaf area ratios (LAR) than shade tolerant species. In contrast, leaf gas exchange characteristics, or acclimation potential in these traits, had no relationship with seedling mortality rates in shade. In both shade tolerant and intolerant species, light saturated photosynthesis rates, dark respiration, and light compensation points were higher for sungrown seedlings than for shade-grown seedlings. Differences in R:FR ratio in shade did not affect gas exchange, allocation patterns, or growth rates of any species. Survival of young tree seedlings in shade did not depend on higher net photosynthesis or biomass accumulation rates in shade. Rather, species with higher RGR died faster in shade than species with lower RGR. This trend could be explained if survival depends on morphological characteristics likely to enhance defense against herbivores and pathogens, such as dense and tough leaves, a well-established root system, and high wood density. High construction costs for these traits, and low LAR as a consequence of these traits, should result in lower rates of whole-plant carbon gain and RGR for shade tolerant species than shade-intolerant species in shade as well as in sun.

Fully developed turbulent pipe flow: a comparison between direct numerical simulation and experiment

Abstract: Direct numerical simulations (DNS) and experiments are carried out to study fully developed turbulent pipe flow at Reynolds number Rec ≈ 7000 based on centreline velocity and pipe diameter The agreement between numerical and experimental results is excellent for the lower-order statistics (mean flow and turbulence intensities) and reasonably good for the higher-order statistics (skewness and flatness factors) To investigate the differences between fully developed turbulent flow in an axisymmetric pipe and a plane channel geometry, the present DNS results are compared to those obtained from a channel flow simulation Beside the mean flow properties and turbulence statistics up to fourth order, the energy budgets of the Reynolds-stress components are computed and compared The present results show that the mean velocity profile in the pipe fails to conform to the accepted law of the wall, in contrast to the channel flow This confirms earlier observations reported in the literature The statistics on fluctuating velocities, including the energy budgets of the Reynolds stresses, appear to be less affected by the axisymmetric pipe geometry Only the skewness factor of the normal-to-the-wall velocity fluctuations differs in the pipe flow compared to the channel flow The energy budgets illustrate that the normal-to-the-wall velocity fluctuations in the pipe are altered owing to a different ‘impingement’ or ‘splatting’ mechanism close to the curved wall

Dendrimer‐based metal chelates: A new class of magnetic resonance imaging contrast agents

Abstract: We have developed a new class of magnetic resonance imaging contrast agents with large proton relaxation enhancements and high molecular relaxivities. The reagents are built from the polyamidoamine form of Starburst dendrimers in which free amines have been conjugated to the chelator 2-(4-isothiocyanatobenzyl)-6-methyl-diethylenetriaminepentaacetic acid. The dendrimer gadolinium poly-chelates have enhancement factors, i.e., the ratio of the relaxivity per Gd(III) ion to that of Gd(III)-diethylenetriaminepentaacetic acid, of up to 6. These factors are more than twice those observed for analogous metal-chelate conjugates formed with serum albumins, polylysine, or dextran. One of the dendrimer-metal chelate conjugates has 170 gadolinium ions bound, which greatly exceeds the number bound to other macromolecular agents reported in the literature, and has a molecular relaxivity of 5,800 (mM.s)-1, at 25 MHz, 20 degrees C, and pH of 7.4. We observed that these dendrimer-based agents enhance conventional MR images and 3D time of flight MR angiograms, and that those with molecular weights of 8,508 and 139,000 g/mole have enhancement half lives of 40 +/- 10 and 200 +/- 100 min, much longer than the 24 +/- 4 min measured for Gd(III)-diethylenetriaminepentaacetic acid. Our results suggest that this new and powerful class of contrast agents have the potential for diverse and extensive application in MR imaging.

A survey of power estimation techniques in VLSI circuits

Abstract: With the advent of portable and high-density microelectronic devices, the power dissipation of very large scale integrated (VLSI) circuits is becoming a critical concern. Accurate and efficient power estimation during the design phase is required in order to meet the power specifications without a costly redesign process. In this paper, we present a review of the power estimation techniques that have recently been proposed. >

Aging and Inhibition: Beyond a Unitary View of Inhibitory Processing in Attention

Abstract: The authors examined the question of whether a decrease in the efficiency of inhibitory processing with aging is a general phenomenon. Thirty elderly and 32 young adults performed a series of tasks from which the authors could extract measures of inhibitory function. The tasks and task components included response compatibility, negative priming, stopping, spatial precuing, Wisconsin Card Sorting Test (WCST), and the Cognitive Failures Questionnaire (CFQ). Only limited evidence for age-related differences in inhibitory function was obtained. Old adults had more difficulty than young adults in stopping an overt response and adopting new rules in a categorization task. However, elderly and young adults produced equivalent negative priming effects, response compatibility effects, spatial precuing effects, and self-reported cognitive failures. The findings are discussed in terms of the relationship between aging, inhibitory processes, and neuroanatomical and physiological function.