Showing papers by "University of Illinois at Urbana–Champaign published in 1995"

The art of case study research

Abstract: Introduction An Intensive Study of Case Study Research Methods The Unique Case Research Questions The Nature of Qualitative Research Data Gathering Analysis and Interpretation Case Researcher Roles Triangulation Writing the Report Reflections Harper School

Discrete-Event System Simulation

Abstract: Beleska o autorima: str. XV-XVI. - Bibliografija uz svako poglavlje. - Registar. - Summaries.

Relational aggression, gender, and social-psychological adjustment.

Abstract: Prior studies of childhood aggression have demonstrated that, as a group, boys are more aggressive than girls. We hypothesized that this finding reflects a lack of research on forms of aggression that are relevant to young females rather than an actual gender difference in levels of overall aggressiveness. In the present study, a form of aggression hypothesized to be typical of girls, relational aggression, was assessed with a peer nomination instrument for a sample of 491 third-through sixth-grade children. Overt aggression (i.e., physical and verbal aggression as assessed in past research) and social-psychological adjustment were also assessed. Results provide evidence for the validity and distinctiveness of relational aggression. Further, they indicated that, as predicted, girls were significantly more relationally aggressive than were boys. Results also indicated that relationally aggressive children may be at risk for serious adjustment difficulties (e.g., they were significantly more rejected and reported significantly higher levels of loneliness, depression, and isolation relative to their nonrelationally aggressive peers).

Funnels, pathways, and the energy landscape of protein folding: A synthesis

Abstract: The understanding, and even the description of protein folding is impeded by the complexity of the process. Much of this complexity can be described and understood by taking a statistical approach to the energetics of protein conformation, that is, to the energy landscape. The statistical energy landscape approach explains when and why unique behaviors, such as specific folding pathways, occur in some proteins and more generally explains the distinction between folding processes common to all sequences and those peculiar to individual sequences. This approach also gives new, quantitative insights into the interpretation of experiments and simulations of protein folding thermodynamics and kinetics. Specifically, the picture provides simple explanations for folding as a two-state first-order phase transition, for the origin of metastable collapsed unfolded states and for the curved Arrhenius plots observed in both laboratory experiments and discrete lattice simulations. The relation of these quantitative ideas to folding pathways, to uniexponential vs. multiexponential behavior in protein folding experiments and to the effect of mutations on folding is also discussed. The success of energy landscape ideas in protein structure prediction is also described. The use of the energy landscape approach for analyzing data is illustrated with a quantitative analysis of some recent simulations, and a qualitative analysis of experiments on the folding of three proteins. The work unifies several previously proposed ideas concerning the mechanism protein folding and delimits the regions of validity of these ideas under different thermodynamic conditions. © 1995 Wiley-Liss, Inc.

Who Is Happy

Abstract: A flood of new studies explores people's subjective well-being (SWB) Frequent positive affect, infrequent negative affect, and a global sense of satisfaction with life define high SWB These studies reveal that happiness and life satisfaction are similarly available to the young and the old, women and men, blacks and whites, the rich and the working-class Better clues to well-being come from knowing about a person's traits, close relationships, work experiences, culture, and religiosity We present the elements of an appraisal-based theory of happiness that recognizes the importance of adaptation, cultural world-view, and personal goals

1H, 13C and 15N chemical shift referencing in biomolecular NMR

Abstract: A considerable degree of variability exists in the way that 1H, 13C and 15N chemical shifts are reported and referenced for biomolecules. In this article we explore some of the reasons for this situation and propose guidelines for future chemical shift referencing and for conversion from many common 1H, 13C and 15N chemical shift standards, now used in biomolecular NMR, to those proposed here.

Horizontal and Vertical Dimensions of Individualism and Collectivism: A Theoretical and Measurement Refinement

Abstract: In developing a new scale, this article makes theoretical and measurement distinctions between vertical and horizontal individualism and collectivism. Vertical collectivism includes perceiving the selfas a part (or an aspect) of a collective and accepting inequalities within the collective. Horizontal collectivism includes perceiving the self as a part of the collective, but seeing all members of the collective as the same; thus equality is stressed. Vertical individualism includes the conception of an autonomous individual and acceptance of inequality. Horizontal individualism includes the conception of an autonomous individual and emphasis on equality. Measurement of these constructs is preferable theoretically and empirically (better internal consistency) to either of the more general constructs of individualism and collectivism or the constituent elements of these constructs, such as self-reliance, hedonism, family integrity, and so on. The usefulness of these theoretical distinctions is demonstrated ...

Path integrals in the theory of condensed helium

Abstract: One of Feynman's early applications of path integrals was to superfluid $^{4}\mathrm{He}$. He showed that the thermodynamic properties of Bose systems are exactly equivalent to those of a peculiar type of interacting classical "ring polymer." Using this mapping, one can generalize Monte Carlo simulation techniques commonly used for classical systems to simulate boson systems. In this review, the author introduces this picture of a boson superfluid and shows how superfluidity and Bose condensation manifest themselves. He shows the excellent agreement between simulations and experimental measurements on liquid and solid helium for such quantities as pair correlations, the superfluid density, the energy, and the momentum distribution. Major aspects of computational techniques developed for a boson superfluid are discussed: the construction of more accurate approximate density matrices to reduce the number of points on the path integral, sampling techniques to move through the space of exchanges and paths quickly, and the construction of estimators for various properties such as the energy, the momentum distribution, the superfluid density, and the exchange frequency in a quantum crystal. Finally the path-integral Monte Carlo method is compared to other quantum Monte Carlo methods.

Cross-Cultural Correlates of Life Satisfaction and Self-Esteem

Abstract: College students in 31 nations (N = 13,118) completed measures of self-esteem, life satisfaction, and satisfaction with specific domains (friends, family, and finances). The authors assessed whether cross-cultural variations in the strength of associations were related to societal dimensions including income and individualism. At the national level, individualism correlated −0.24 (ns) with heterogeneity and 0.71 (p<0.001) with wealth. At the individual level, self-esteem and life satisfaction were correlated 0.47 for the entire sample. This relation, however, was moderated by the individualism of the society. The associations of financial, friend, and family satisfactions with life satisfaction and with self-esteem also varied across nations. Financial satisfaction was a stronger correlate of life satisfaction in poorer countries. It was found that life satisfaction and self-esteem were clearly discriminable constructs. Satisfaction ratings, except for financial satisfaction, varied between slightly positive and fairly positive.

Factors Predicting the Subjective Well-Being of Nations

Abstract: Subjective well-being (SWB) in 55 nations, reported in probability surveys and a large college student sample, was correlated with social, economic, and cultural characteristics of the nations. The SWB surveys, representing nations that include three fourths of the earth's population, showed strong convergence. Separate measures of the predictor variables also converged and formed scales with high reliability, with the exception of the comparison variables. High income, individualism, human rights, and societal equality correlated strongly with each other, and with SWB across surveys. Income correlated with SWB even after basic need fulfillment was controlled. Only individualism persistently correlated with SWB when other predictors were controlled. Cultural homogeneity, income growth, and income comparison showed either low or inconsistent relations with SWB.

Strategic flexibility in product competition

Abstract: This paper investigates competition in dynamic product markets from combined resource base and strategic flexibility perspectives. A concept of strategic flexibility in product competition is developed in which flexibility depends jointly on (1) the resource flexibility of the product creation resources avaialble to a firm and (2) the coordination flexibility of the firm in using its available resources in product markets. Two recent technological innovations affecting product creation processes—CADD/CIM systems and modular product design—are argued to have greatly increased the potential flexibilities of key product creation resources. Managerial innovations in the use of these technologies have also led to important new coordination flexibilities. The combination of recently achievable resource and coordination flexibilities is argued to have transformed the competitive environments of many product markets, leading to new kinds of product strategies, new organizational forms, and a new dominant logic for competing in dynamic product markets.

Blind adaptive multiuser detection

Abstract: The decorrelating detector and the linear minimum mean-square error (MMSE) detector are known to be effective strategies to counter the presence of multiuser interference in code-division multiple-access channels; in particular, those multiuser detectors provide optimum near-far resistance. When training data sequences are available, the MMSE multiuser detector can be implemented adaptively without knowledge of signature waveforms or received amplitudes. This paper introduces an adaptive multiuser detector which converges (for any initialization) to the MMSE detector without requiring training sequences. This blind multiuser detector requires no more knowledge than does the conventional single-user receiver: the desired user's signature waveform and its timing. The proposed blind multiuser detector is made robust with respect to imprecise knowledge of the received signature waveform of the user of interest. >

Thinking About Answers: The Application of Cognitive Processes to Survey Methodology

Abstract: Originally published in Contemporary Psychology: APA Review of Books, 1997, Vol 42(7), 652-652. For students and practitioners of survey research, Thinking About Answers: The Application of Cognitive Processes to Survey Methodology (see record 1995-98746-000) provides a broad theoretical discussion

POLYPHASIC CHLOROPHYLL a FLUORESCENCE TRANSIENT IN PLANTS AND CYANOBACTERIA

Abstract: The variable chlorophyll (Chl) a fluorescence yield is known to be related to the photochemical activity of photosystem I1 (PSII) of oxygen-evolving organisms. The kinetics of the fluorescence rise from the minimum yield, F,, to the maximum yield, F,, is a monitor of the accumulation of net reduced primary bound plastoquinone (QA) with time in all the PSII centers. Using a shutter-less system (Plant Efficiency Analyzer, Hansatech, UK), which allows data accumulation over several orders of magnitude of time (40 11s to 120 s), we have measured on a logarithmic time scale, for the first time, the complete polyphasic fluorescence rise for a variety of oxygenic plants and cyanobacteria at different light intensities. With increasing light intensity, the fluorescence rise is changed from a typical 0-I-P characteristic to curves with two intermediate levels J and I, both of which show saturation at high light intensity but different intensity dependence. Under physiological conditions, Chl a fluorescence transients of all the organisms examined follow the sequence of 0-J-I-P. The characteristics of the kinetics with respect to light intensity and temperature suggest that the 0-J phase is the photochemical phase, leading to the reduction of QA to QA-. The intermediate level I is suggested to be related to a heterogeneity in the filling up of the plastoquinone pool. The P is reached when all the plastoquinone (PQ) molecules are reduced to PQH2. The addition of 3-(3-4-dichIorophenyl)- 1,l -dimethylurea leads to a transformation of the 0-J-I-P rise into an 0-J rise. The kinetics of 0-J-I-P observed here was found to be similar to that of 0-1,-12-P, reported by Neubauer and Schreiber (2. Naturforsch. 42c, 1246-1254, 1987). The biochemical significance of the fluorescence steps 0-J-I-P with respect to the filling up of the plasto- quinone pool by PSII reactions is discussed.

Navigating the folding routes.

Abstract: To fold, a protein navigates with remarkable ease through a complicated energy landscape as it explores many possible physical configurations. This feat is beginning to be quantitatively understood by means of statistical mechanics and simplified computer models (1). Folded proteins are marvels of molecular engineering and it is hard to avoid thinking that all of their complex structural features play a role in their folding through an obligate En multistep mechanism. A unique folding pathway, if it exists, could be elucidated with classical chemical experiments. A newer view holds that in the earlier stages a protein possesses a large ensemble of structures. The problem is not to find a single route but to characterE ize the dynamics of the ensemble n through a statistical description of 2 the topography of the free-energy landscape. Folding is easy if the landscape resembles a many-dimensional funnel leading through a myriad of pathways to the native structure. Only a few parameters should be needed to characterize statistically the topography of and routes down the folding funnel. Using experimental data, Onuchic et al. have estimated the extent, ruggedness, and slope of the folding funnel (2). Similar parameters characterize the energy landscape Enat of simple computer models of pron teins. These models of self-interacting necklaces of beads, often on Fig. 1. lattices, lack most of the details of helical real proteins, but establishing a represE quantitative correspondence bethrougt tween the landscapes of computer emerg models and real proteins makes it Q, is in possible to use simulations to understand folding kinetics. The extent of a protein energy landscape is huge. Before folding, each residue can take on about 10 different conformations; thus, a 60-residue protein can be in any of 1060 states. An unguided search, like a

Observation of top quark production in p̄p collisions with the collider detector at fermilab

Abstract: We establish the existence of the top quark using a $67{\mathrm{pb}}^{\ensuremath{-}1}$ data sample of $\overline{p}p$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ collected with the Collider Detector at Fermilab (CDF). Employing techniques similar to those we previously published, we observe a signal consistent with $t\overline{t}$ decay to $\mathrm{WWb}\overline{b}$, but inconsistent with the background prediction by $4.8\ensuremath{\sigma}$. Additional evidence for the top quark is provided by a peak in the reconstructed mass distribution. We measure the top quark mass to be $176\ifmmode\pm\else\textpm\fi{}8(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}10(\mathrm{syst})\mathrm{GeV}{/c}^{2}$, and the $t\overline{t}$ production cross section to be ${6.8}_{\ensuremath{-}2.4}^{+3.6}\mathrm{pb}$.

The swing up control problem for the Acrobot

Abstract: Underactuated mechanical systems are those possessing fewer actuators than degrees of freedom. Examples of such systems abound, including flexible joint and flexible link robots, space robots, mobile robots, and robot models that include actuator dynamics and rigid body dynamics together. Complex internal dynamics, nonholonomic behavior, and lack of feedback linearizability are often exhibited by such systems, making the class a rich one from a control standpoint. In this article the author studies a particular underactuated system known as the Acrobot: a two-degree-of-freedom planar robot with a single actuator. The author considers the so-called swing up control problem using the method of partial feedback linearization. The author gives conditions under which the response of either degree of freedom may be globally decoupled from the response of the other and linearized. This result can be used as a starting point to design swing up control algorithms. Analysis of the resulting zero dynamics as well as analysis of the energy of the system provides an understanding of the swing up algorithms. Simulation results are presented showing the swing up motion resulting from partial feedback linearization designs. >

Multilevel fast-multipole algorithm for solving combined field integral equations of electromagnetic scattering

Abstract: The fast multipole method (FMM) has been implemented to speed up the matrix-vector multiply when an iterative method is used to solve the combined field integral equation (CFIE). FMM reduces the complexity from O(N2) to O(N1.5). With a multilevel fast multipole algorithm (MLFMA), it is further reduced to O(N log N). A 110, 592-unknown problem can be solved within 24 h on a SUN Sparc 10. © 1995 John Wiley & Sons, Inc.

Phase-sensitive tests of the symmetry of the pairing state in the high-temperature superconductors-Evidence for d x 2 -y 2 symmetry

Abstract: Understanding the mechanism responsible for superconductivity in the high-temperature cuprates has been one of the major goals of condensed-matter physicists since the discovery of these exciting materials in 1986. Experimental evidence suggests that the pairing state may be unconventional, featuring an anisotropic order parameter for which a wide range of theoretical models for the superconducting pairing have been proposed. Recently, a new class of experiments has been presented that are sensitive to the phase of the superconducting order parameter, allowing an unambiguous determination of the symmetry of the pairing state. These experiments, based on the interference of the quantum-mechanical phases in Josephson tunnel junctions and dc SQUID devices, give strong evidence for pairing in a channel with $d$--wave symmetry in the most widely studied cuprate, $Y{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}x}$. Confirmation of this pairing state will focus efforts to develop a microscopic theory for the high-temperature superconductors and to apply them in power transmission and electronic device technologies.

Monolayers in Three Dimensions: NMR, SAXS, Thermal, and Electron Hopping Studies of Alkanethiol Stabilized Gold Clusters

Abstract: Gold clusters stabilized by chemisorbed monolayers of octane-, dodecaneor hexadecanethiolate have been investigated in solution and in the solid phase. These materials can be pumped free of solvent to form a dark brown solid that can be re-dissolved in nonpolar solvents. Their exceptional stability suggests they be viewed as cluster compounds. The self-assembled alkanethiolate monolayers stabilizing the metal clusters can be investigated using techniques that are insufficiently sensitive for study of a monolayer on a flat surface, e.g., 'H and I3C NMR, elemental analysis, differential scanning calorimetry (DSC), thermogravimetry (TGA), and diffusion-ordered NMR spectroscopy (DOSY). Results from such measurements, combined with small-angle X-ray scattering (SAXS) data on solutions of the clusters and images from scanning tunneling (STM), and atomic force microscopy (AFM), are consistent with a small, monodisperse (12 8, radius) gold core, which modeled as a sphere contains -400 Au atoms and -126 alkanethiolate chains, or if modeled as a cuboctahedral structure contains 309 Au atoms and -95 alkanethiolate chains. High-resolution NMR spectra of cluster solutions display well-defined resonances except for methylenes nearest the gold interface; the absence of the latter resonances is attributed to a combination of broadening mechanisms based on the discontinuous change in magnetic susceptibility at the metal-hydrocarbon interface and residual dipolar interactions. Films of the dry, solid cluster compound on interdigitated array electrodes exhibit current-potential responses characteristic of electron hopping conductivity in which electrons tunnel from Au core to Au core. The electron hopping rate decreases and the activation barrier increases systematically at longer alkane chain length. The results are consistent with electron transport rate control being a combination of thermally activated electron transfer to create oppositely charged Au cores (cermet theory) and distance-dependent tunneling (8 = 1.2 A-1) through the oriented alkanethiolate layers separating them. The self-organization of alkanethiols chemisorbed on planar Au surfaces has generated intense interest in understanding its chemical basis.' The two-dimensional character of self-assembled monolayers places limits, however, on the experiments by which they can be probed when they are chemisorbed on planar Au surfaces, e.g.,I wetting, helium diffraction, scanning probe, interfacial electron transfers, FTIR spectroscopy, etc. An *Address correspondence to this author at the University of North +Department of Chemistry, University of Illinois, Urbana, IL. * W. R. Grace and Co, Washington Research Center, 7379 Route 32, 3 Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Department of Chemistry, University of Oregon, Eugene, OR97403II Oak Ridge National Laboratories. # Department of Physics and Astronomy. University of North Carolina. @ Abstract published in Advance ACS Abstracts, December 1, 1995. (1) (a) DuBois L. H.; Nuzzo, R. G. Annu. Rev. Chem. Phys. 1992, 43, 437. (b) Laibinis, P. E.; Whitesides, G. M.; Allara D. L.; Tao, Y.-T.; Parikh, A. N.; Nuzzo, R. G. J. Am. Chem. Soc. 1991,133, 7152. (c) Chidsey, C. E. D.; Liu, G.; Scoles, G.; Wang, J. Langmuir, 1990, 6, 1804. (d) Fenter, P.; Eisenberger, P.; Liang, K. S. Phys. Rev. Let?. 1993, 70, 2447. (e) Chidsey, C. E. D. Science 1991,251,919. (0 Chailapakul, 0.; Sun, L.; Xu C.; Crooks, R. M. J. Am. Chem. SOC. 1993, 115, 12439. (g) Nemetz, A; Fischer T.; Ulman, A,; Knoll, W. J. Chem. Phys. 1993, 987. (h) Schneider, T. W.; Buttry, D. A. J. Am. Chem. SOC. 1993,115, 12391. (i) Widrig, C. A,; Alves, C. A.; Porter, M. D. J. Am. Chem. Soc. 1991, 123, 2805. (j) Kim, Y.-T.; McCarley, R. L.; Bard A. J. J. Phys. Chem. 1992, 96, 7416. Carolina. Columbia, MD 2 1044-4098.

Spontaneous assembly of a hinged coordination network

Abstract: THE field of supramolecular chemistry has advanced to a stage at which it is possible to select building blocks that will self-assemble into structures with specific network topologies1–3. This makes possible the rational design and synthesis of molecular solids with potentially interesting properties. Here we report the construction of open, hinged networks from molecular building blocks. This class of materials has been predicted to exhibit unusual mechanical properties, including auxetic behaviour (negative Poisson's ratio) and negative coefficients of thermal expansion4–6. Our approach relies on the notion that rigid organic molecules of high symmetry will adopt one of only a few possible structures when linked via hydrogen bonds or coordination to metals7–9. We use trigonal lig-ands to make networks joined at the vertices by metal ions; the resulting networks are homeotypic10 with the honeycomb-like A1B2 and the hinge-like ThSi2 phases. The hinge-like network has channels of inner diameter 15 A, within which included molecules can be exchanged while the framework remains intact. We have not yet determined whether this material is auxetic.

Boards of directors and substitution effects of alternative governance mechanisms

Abstract: Research on the determinants and effects of various governance mechanisms typically assumes that these mechanisms operate independently. However, since a variety of mechanisms are used to achieve alignment of the interests of shareholders and managers, we propose that the level of a particular mechanism should be influenced by the levels of other mechanisms which simultaneously operate in the firm. We examine the substitution effects between alternative internal governance mechanisms for a sample of 81 bank holding companies in the postderegulation period. Specifically, we consider the relationship between monitoring by outside directors and the following mechanisms: monitoring by large outside shareholders, mutual monitoring by inside directors, and incentive effects of shareholdings by managers. Our results provide evidence consistent with the substitution hypothesis. We examine the implications of our findings for future research in the area of corporate governance.

Relational aggression: The role of intent attributions, feelings of distress, and provocation type

Abstract: In recent research a relationally oriented form of aggression has been identified that, in contrast to overt aggression that harms others through physical means (e.g., hitting), harms others through damage to their peer relationships (e.g., angrily retaliating against a peer by excluding her from one's play group). The goal this research was to assess the role of intent attributions, feelings of distress, and provocation type (relational vs. instrumental) in children's relationally aggressive behavior. A total of 252 third- through sixth-grade children participated as subjects. A hypothetical provocation instrument was used to assess children's intent attributions and feelings of distress for ambiguous relational and instrumental provocation situations. Results showed that, as hypothesized, relationally aggressive children exhibited a hostile attributional bias and reported significantly higher levels of distress than did their nonaggressive peers for relational provocation situations. In addition, girls reported significantly higher levels of distress than did boys for relational provocation situations. Further, a comorbid group of relationally plus overtly aggressive children also exhibited a hostile attributional bias; however, their bias was evident for instrumental provocation situations only.

Measuring Sexual Harassment: Theoretical and Psychometric Advances

Abstract: This article describes a program of research designed to yield a conceptually grounded, psychometrically sound instrument for assessing the incidence and prevalence of sexual harassment in the workplace. Following the specification of a theoretical framework that is consistent with both legal guidelines and psychological research, we review the development and evaluation of a three-dimensional model of sexual harassment (gender harassment, unwanted sexual attention, and sexual coercion). Based on this model, we describe the development of a revised version of the Sexual Experiences Questionnaire (SEQ; Fitzgerald et al., 1988). Following extensive pilot work, the instrument was field tested in a large regulated utility. Data from 448 employed women (professional, technical, clerical and blue collar workers) support the reliability of the scales, and confirmatory factor analysis in this new sample confirms the stability and generalizability of the theoretical model. Following a brief review of validity data...