Showing papers by "University of Notre Dame published in 1999"

Emergence of Scaling in Random Networks

Abstract: Systems as diverse as genetic networks or the World Wide Web are best described as networks with complex topology. A common property of many large networks is that the vertex connectivities follow a scale-free power-law distribution. This feature was found to be a consequence of two generic mechanisms: (i) networks expand continuously by the addition of new vertices, and (ii) new vertices attach preferentially to sites that are already well connected. A model based on these two ingredients reproduces the observed stationary scale-free distributions, which indicates that the development of large networks is governed by robust self-organizing phenomena that go beyond the particulars of the individual systems.

Diameter of the World-Wide Web

Abstract: Despite its increasing role in communication, the World-Wide Web remains uncontrolled: any individual or institution can create a website with any number of documents and links. This unregulated growth leads to a huge and complex web, which becomes a large directed graph whose vertices are documents and whose edges are links (URLs) that point from one document to another. The topology of this graph determines the web's connectivity and consequently how effectively we can locate information on it. But its enormous size (estimated to be at least 8×108 documents1) and the continual changing of documents and links make it impossible to catalogue all the vertices and edges.

The diameter of the world wide web

Abstract: Despite its increasing role in communication, the world wide web remains the least controlled medium: any individual or institution can create websites with unrestricted number of documents and links. While great efforts are made to map and characterize the Internet's infrastructure, little is known about the topology of the web. Here we take a first step to fill this gap: we use local connectivity measurements to construct a topological model of the world wide web, allowing us to explore and characterize its large scale properties.

Mean-field theory for scale-free random networks

Abstract: Random networks with complex topology are common in Nature, describing systems as diverse as the world wide web or social and business networks. Recently, it has been demonstrated that most large networks for which topological information is available display scale-free features. Here we study the scaling properties of the recently introduced scale-free model, that can account for the observed power-law distribution of the connectivities. We develop a mean-eld method to predict the growth dynamics of the individual vertices, and use this to calculate analytically the connectivity distribution and the scaling exponents. The mean-eld method can be used to address the properties of two variants of the scale-free model, that do not display power-law scaling. c 1999 Elsevier Science B.V. All rights reserved.

Green processing using ionic liquids and CO2

Abstract: Many organic solvents evaporate into the atmosphere with detrimental effects on the environment and human health. But room-temperature ionic liquids, with low viscosity and no measurable vapour pressure1, can be used as environmentally benign media for a range of industrially important chemical processes2,3,4,5,6, despite uncertainties about thermal stability and sensitivity to oxygen and water. It is difficult to recover products, however, as extraction with water7 works only for hydrophilic products, distillation is not suitable for poorly volatile or thermally labile products, and liquid-liquid extraction using organic solvents results in cross-contamination. We find that non-volatile organic compounds can be extracted from ionic liquids using supercritical carbon dioxide, which is widely used to extract large organic compounds with minimal pollution8. Carbon dioxide dissolves in the liquid to facilitate extraction, but the ionic liquid does not dissolve in carbon dioxide, so pure product can be recovered.

Proactive personality and career success.

Abstract: This study examined the relationship between proactive personality and career success by surveying a sample of 496 employees (320 men and 176 women) from a diverse set of occupations and organizations. Proactive personality was positively associated with both self-reported objective (salary and promotions) and subjective (career satisfaction) indicators of career success. Hierarchical regression analyses showed that proactive personality explained additional variance in both objective and subjective career success even after controlling for several relevant variables (demographic, human capital, motivational, organizational, and industry) that have previously been found to be predictive of career outcomes. These findings were consistent using both self-report and significant--other ratings of proactive personality.

The Fluid Mechanics of Microdevices—The Freeman Scholar Lecture

Abstract: Manufacturing processes that can create extremely small machines have been developed in recent years. Microelectromechanical systems (MEMS) refer to devices that have characteristic length of less than 1 mm but more than 1 micron, that combine electrical and mechanical components and that are fabricated using integrated circuit batch-processing techniques. Electrostatic, magnetic, pneumatic and thermal actuators, motors, valves, gears, and tweezers of less than 100-μm size have been fabricated. These have been used as sensors for pressure, temperature, mass flow, velocity and sound, as actuators for linear and angular motion and as simple components for complex systems such as micro-heat-engines and micro-heat-pumps The technology is progressing at a rate that fa r exceeds that of our understanding of the unconventional physics involved in the operation as well as the manufacturing of those minute devices. The primary objective of this article is to critically review the status of our understanding of fluid flow phenomena particular to microdevices. In terms of applications, the paper emphasizes the use of MEMS as sensors and actuators for flow diagnosis and control.

Personal Selling and Sales Management: A Relationship Marketing Perspective

Abstract: The authors examine how the practice of personal selling and sales management is changing as a result of the increased attention on long-term, buyer-seller relationships and identify some implications of these changes. Changes in the traditional personal selling and sales management activities are needed to support the emergence of the part-nering role for salespeople. For salespeople in the part-nering role, the personal selling shifts from a focus on influencing buyer behavior to managing the conflict inherent in buyer-seller relationships. The emphasis on building relationships rather than making short-term sales and the use of sales teams dictates changes in the way firms select, train, evaluate, and compensate salespeople and members of sales teams. In this article, the authors have suggested some issues concerning the emerging partnering role for salespeople that deserve the attention of scholars interested in personal selling and sales management research.

Formation of Colloidal Silver Nanoparticles: Capping Action of Citrate

Abstract: Colloidal silver sols of long-time stability are formed in the γ-irradiation of 1.0 × 10-4 M AgClO4 solutions, which also contain 0.3 M 2-propanol, 2.5 × 10-2 M N2O, and sodium citrate in various concentrations. The reduction of Ag+ in these solutions is brought about by the 1-hydroxyalkyl radical generated in the radiolysis of 2-propanol; citrate does not act as a reductant but solely as a stabilizer of the colloidal particles formed. Its concentration is varied in the range from 5.0 × 10-5 to 1.5 × 10-3 M, and the size and size distribution of the silver particles are studied by electron microscopy. At low citrate concentration, partly agglomerated large particles are formed that have many imperfections. In an intermediate range (a few 10-4 M), well-separated particles with a rather narrow size distribution and little imperfections are formed, the size slightly decreasing with increasing citrate concentration. At high citrate concentrations, large lumps of coalesced silver particles are present, due to ...

The Performance Effects of Pay Dispersion on Individuals and Organizations

Abstract: Pay distribution research is relatively scarce in the compensation literature, yet pay distributions are viewed as critically important by organizational decision makers. This study is a direct tes...

Digital logic gate using quantum-Dot cellular automata

Abstract: A functioning logic gate based on quantum-dot cellular automata is presented, where digital data are encoded in the positions of only two electrons. The logic gate consists of a cell, composed of four dots connected in a ring by tunnel junctions, and two single-dot electrometers. The device is operated by applying inputs to the gates of the cell. The logic AND and OR operations are verified using the electrometer outputs. Theoretical simulations of the logic gate output characteristics are in excellent agreement with experiment.

Implications of Recent Developments in Structural Equation Modeling for Counseling Psychology

Abstract: We review recent developments in structural equation modeling (SEM) since Fassinger’s (1987) introductory article. We discuss issues critical to designing and evaluating SEM studies. Our review includes recent technological developments in SEM such as new approaches from hypothesis testing to determining statistical power and assessing model fit. Moreover, we discuss innovations in applying SEM to different research contexts and designs (e.g., experimental and longitudinal designs and interactions among latent variables). Finally, we discuss procedures for redressing common problems and misunderstandings in the application of SEM procedures to counseling research.

Dynamic range improvement through multiple exposures

Abstract: This paper presents an approach for improving the effective dynamic range of cameras by using multiple photographs of the same scene taken with different exposure times. Using this method enables the photographer to accurately capture scenes that contain a high dynamic range, i.e., scenes that have both very bright and very dark regions. The approach requires an initial calibration, where the camera response function is determined. Once the response function for a camera is known, high dynamic range images can be computed easily. The high dynamic range output image consists of a weighted average of the multiply-exposed input images, and thus contains information captured by each of the input images. From a computational standpoint, the proposed algorithm is very efficient, and requires little processing time to determine a solution.

Introduction — Secularization Theory: The Course of a Concept

Abstract: This essay provides an introduction to the secularization debate as it presents itself at the end of the 1990s. After a conceptual survey from the mid-1960s to the present, we focus on the empirical and historical elements that undergird both the claims of secularization theory and those of its principal critics. Secularization theory is placed in relationship both to the Religion of Reason of the Enlightenment and developments in European religious historiography during the nineteenth century. The underlying conflict to be resolved with respect to secularization is whether the term can be used in a relatively value-neutral analytic way or whether it inherently carries unsubstantiated value presuppositions

Effects of Market Reform on the Trading Costs and Depths of Nasdaq Stocks

Abstract: The relative merits of dealer versus auction markets have been a subject of significant and sometimes contentious debate. On January 20, 1997, the Securities and Exchange Commission began implementing reforms that would permit the public to compete directly with Nasdaq dealers by submitting binding limit orders. Additionally, superior quotes placed by Nasdaq dealers in private trading venues began to be displayed in the Nasdaq market. We measure the impact of these new rules on various measures of performance, including trading costs and depths. Our results indicate that quoted and effective spreads fell dramatically without adversely affecting market quality.

Parametric sensitivity in chemical systems

Abstract: Preface 1. Introduction 2. Introduction to sensitivity analysis 3. Thermal explosion in batch reactors 4. Runaway in tubular reactors 5. Parametric sensitivity in continuous-flow stirred tank reactors 6. Runaway in fixed-bed catalytic reactors 7. Parametric sensitivity and ignition phenomena in combustion systems 8. Sensitivity analysis in mechanistic study and model reduction 9. Sensitivity analysis in air pollution 10. Sensitivity analysis in metabolic processes Index.

Glycosylation of Pichia pastoris-derived proteins.

Abstract: The Pichia pastoris system for expression of heterologous recombinant proteins is being used increasingly because of the large yields of properly folded proteins that result and the ease of scaling preparations into large-biomass fermentors. Another advantage of this system centres on the type of glycosylation that results, generally yielding protein-bound oligosaccharides that are of much shorter chain length than found in Saccharomyces cerevisiae. This review is a summary of the current state of knowledge of glycosylation of proteins in this methylotrophic yeast.

Borate minerals. ii. a hierarchy of structures based upon the borate fundamental building block

Abstract: A hierarchical structural classification is developed for borate minerals, based on the linkage of (BQ) triangles and (BO+) tetrahedra to form FBBs (fundamental building blocks) that polymerize to form the structural unit, a tightly bonded anionic polyhedral array whose excess charge is baianced by the presence of large low-valence interstitial cations. Thirty-one minerals, with nineteen distinct structure-types, contain isolated borate polyhedra. Twenty-seven minerals, with twenty-five distinct structure-types, contain finite clusters of borate polyhedra. Ten minerals, with ten distinct structue-types, contain chains of borate polyhedra. Fifteen minerals, with thirteen distinct structue-types, contain sheets of borate polyhedra. Fifteen minerals, with thirteen distinct sEucture-types, contain frameworks of borate polyhedra. It is only the close-packed structures of the isolatedpolyhedra class that show significant isotypism

Zinc Phosphate with Gigantic Pores of 24 Tetrahedra

Abstract: Materials with open-framework structures are of great importance in many fields of today’s applied chemistry, such as ionexchange, molecular sieving, catalysis, etc. 1-3 The search for new phosphate and other materials with open-framework structures with increasingly larger cavities has been extremely intensive in recent years. 4,5 The number of new synthetically made compounds with extralarge pores, i.e., pores of more than 12 tetrahedra, has grown steadily since 1988, when VPI-5 with 18-membered rings was discovered. 4,6 The largest openings known so far among the silicates and phosphates are of 20-membered rings, for two synthetic phosphates, cloverite and JDF-20, 7,8 and one natural phosphate, cacoxenite. 9 Different approaches toward the synthesis of such materials have been suggested and studied in the past. Among those are, for example, the use of large or oligomeric templates as well as the selection of framework elements that can form three-membered rings such as the zincosilicates and the zincophosphates, 4 or synthesis of nonoxide-based materials. 5 Yet another approach, practiced primarily for the synthesis of mesoporous silicates and aluminosilicates such as MCM-41 and others, involves the use of cooperative templating by assemblies of templates, i.e., liquid crystal templating. 10-12 Capable of such mechanism are surfactant-type templates, i.e., templates that have relatively well separated hydrophobic and hydrophilic ends, where the latter are usually amino groups, phosphates, or sulfates. In the case of the mesoporous materials, the templates have long hydrocarbon chains that form aggregates (micelles), and the resulting frameworks are glassy-like. Here we report the synthesis and structure of a zinc phosphate, Zn 3(PO4)2(PO3OH)(H2DACH)‚ 2H2O (referred to as ND-1), with openings made of 24-membered rings, where an assembly of much smaller “surfactant” molecules, 1,2-diaminocyclohexane (DACH), acts as the template. ND-1 was initially obtained (as a pure solid phase) from a hydrothermal reaction designed to synthesize a templated zinc borophosphate analogous to a known ethylenediamine-templated cobalt borophosphate; 13 therefore, the synthetic mixture contained BPO4, zinc acetate, DACH, and water (molar ratio of 2:1:2.5:117, 210°C, 2 days in Teflon-lined autoclaves, pH ) 8). Later, BPO4 was replaced with H3PO4, and it was found that the synthesis can be carried out at lower temperature, 180 °C, and with either zinc acetate or nitrate. The template was deliberately chosen as the 1,2-isomer of diaminocyclohexane rather than the 1,3or 1,4-substituted isomers because of its well-defined hydrophobic and hydrophilic parts, and therefore the higher potential for liquid-crystal templating. Furthermore, a cyclic template was chosen because of the intrinsic rigidity of the cyclic hydrophobic part and its inability to twist and take different conformations. The only solid product from these reactions was ND-1 in nearly 100 % yield. It crystallizes as very fine, colorless needles, resembling strands of wool or cotton. Fortunately, some of the needles were thick enough for single-crystal X-ray diffraction. A data set was collected from such a crystal, and the structure was successfully refined. 14

Psychological Empowerment as a Multidimensional Construct: A Test of Construct Validity

Abstract: The construct validity of scores on Spreitzer’s Psychological Empowerment scale was examined. Confirmatory factor analysis (CFA) of data from a sample of 160 nurses showed substantial support for Spreitzer’s four empowerment dimensions: meaning, competence, self-determination, and impact. In contrast to Spreitzer’s findings, the results of this study indicated that self-determination is a precursor of impact. This finding was cross-validated with data from a subset of the same sample 1 year later, after implementation of a job redesign program. In addition, results from structural equation modeling (SEM) demonstrated job characteristics to relate differentially to the empowerment dimensions, providing evidence for both convergent and discriminant validity of scores on the four empowerment dimensions. Finally, this study found that the four empowerment dimensions differentially related to organizational commitment and career intentions, providing evidence for the predictive validity of the Empowerment scal...

EFA6, a sec7 domain-containing exchange factor for ARF6, coordinates membrane recycling and actin cytoskeleton organization

Abstract: We have identified a human cDNA encoding a novel protein, exchange factor for ARF6 (EFA6), which contains Sec7 and pleckstrin homology domains. EFA6 promotes efficient guanine nucleotide exchange on ARF6 and is distinct from the ARNO family of ARF1 exchange factors. The protein localizes to a dense matrix on the cytoplasmic face of plasma membrane invaginations, induced on its expression. We show that EFA6 regulates endosomal membrane recycling and promotes the redistribution of transferrin receptors to the cell surface. Furthermore, expression of EFA6 induces actin-based membrane ruffles that are inhibited by co-expression of dominant-inhibitory mutant forms of ARF6 or Rac1. Our results demonstrate that by catalyzing nucleotide exchange on ARF6 at the plasma membrane and by regulating Rac1 activation, EFA6 coordinates endocytosis with cytoskeletal rearrangements.

High-precision calculations of dispersion coefficients, static dipole polarizabilities, and atom-wall interaction constants for alkali-metal atoms

Abstract: The van der Waals coefficients for the alkali-metal atoms from Na to Fr interacting in their ground states are calculated using relativistic ab initio methods The accuracy of the calculations is estimated by also evaluating atomic static electric-dipole polarizabilities and coefficients for the interaction of the atoms with a perfectly conducting wall The results are in excellent agreement with the latest data from studies of magnetic field induced Feshbach resonances in ultracold collisions of Na and of Rb atoms For Cs we provide critically needed data for ultracold collision studies

Collective Motion of Self-Propelled Particles: Kinetic Phase Transition in One Dimension

Abstract: We demonstrate that a system of self-propelled particles exhibits spontaneous symmetry breaking and self-organization in one dimension, in contrast with previous analytical predictions. To explain this surprising result we derive a new continuum theory that can account for the development of the symmetry broken state and belongs to the same universality class as the discrete self-propelled particle model.

Marketing's Contributions to Society:

Abstract: At this unique point in time, it is appropriate to step back and deliberate on the scope of the marketing field and the contributions it offers to society. The authors adopt several perspectives to...

The UV visual world of fishes: a review

Abstract: Ultraviolet-A radiation (320-400 nm) is scattered rapidly in water. Despite this fact, UV is present in biologically useful amounts to at least 100 m deep in clear aquatic environments. Discovery of UV visual pigments with peak absorption at around 360 nm in teleost cone photoreceptors indicates that many teleost fishes may be adapted for vision in the UV range. Considering the characteristic absorption curve for visual pigments, about 18% of the downwelling light that illuminates objects at 30-m depth would be available to W-sensitive cones. Strong scattering of UV radiation should produce unique imaging conditions as a very bright UV background in the horizontal view and a marked veiling effect that, with distance, obscures an image. Many teleosts have three, or even four, classes of cone cells mediating colour vision in their retina and one can be sensitive to UV. These UV-sensitive cones contain a visual pigment based on a unique opsin which is highly conserved between fish species. Several powerful methods exist for demonstration of UV vision, but all are rather demanding in terms of technique and equipment. Demonstration that the eye lacks W-blocking compounds that are present in many fish eyes is a simpler method that can indicate the possibility of UV vision. The only experimental evidence for the use of UV vision by fishes is connected to planktivory: detection of UV-opaque objects at close range against a bright UV background is enhanced by the physical properties of UV light. Once present, perhaps for the function of detecting food, UV vision may well be co-opted through natural selection for other functions. Recent discovery that UV vision is critically important for mate choice in some birds and lizards is a strong object lesson for fish ecologists and behaviourists. Other possible functions amount to far more than merely adding a fourth dimension to the visible spectrum. Since UV is scattered so effectively in water, it may be useful for social signalling at short range and reduce the possibility of detection by other, illegitimate, receivers. Since humans are blind to UV light, we may be significantly in error, in many cases, in our attempts to understand and evaluate Visual aspects of fish behaviour. A survey of the reflectance properties of skin pigments in fishes reveals a rich array of pigments with reflectance peaks in the UV. For example, the same yellow to our eyes may comprise two perceptually different colours to fish, yellow and UV-yellow. It is clearly necessary for us to anticipate that many fishes may have some form of UV vision. (C) 1999 The Fisheries Society of the British Isles.

Radiolytic Preparation of Ultrafine Colloidal Gold Particles in Aqueous Solution: Optical Spectrum, Controlled Growth, and Some Chemical Reactions

Abstract: Orange− or yellow−orange-colored aqueous dispersions of ultrafine gold particles (∼2 nm) result from the γ-irradiation of deaerated solutions containing hydrolyzed AuCl4- and poly(vinyl alcohol) or poly(vinylpyrrolidone), respectively. The particles have a weak and very broad plasmon absorption band with maximum in the 490 to 500 nm range, i.e., at substantially shorter wavelengths than expected from classical Mie theory using bulk dielectric data; moreover, the specific UV absorption increases as the particles become smaller. The particles are used as seeds in the radiolytic reduction of added Au(CN)2- to yield larger particles of any desired size and improved monodispersity. The particles partially react with oxygen. Chemisorption of 3-mercapto propionic acid strongly affects the electronics of the particles, as indicated by the changes in optical absorption. The early stages of AuCl4- reduction are also investigated. The reduction occurs essentially in two steps: (1) formation, and (2) reduction of Au...

The Dynamic Effect of Discounting on Sales: Empirical Analysis and Normative Pricing Implications

Abstract: Baseline sales measure what retail sales would be in the absence of a promotion (Abraham and Lodish 1993), and models that measure baseline sales are widely used by managers to assess the profitability of promotions (Bucklin and Gupta 1999-this issue). Estimates of baseline sales and promotional response are typically independent of past promotional activity, even though there is evidence to suggest that increased discounting reduces off-promotion sales and increases the percentage of purchases made on deal (e.g., Krishna 1994). As a result, models that do not consider dynamic promotional effects can mislead managers to overpromote. Given the widespread use of "static" models to evaluate the efficacy of promotions, it is particularly desirable to calibrate a dynamic brand sales model and use it to establish an optimal course of action. Accordingly, we develop a descriptive dynamic brand sales model and use it to determine normative price promotion strategies. Our descriptive approach consists of estimating a varying-parameter sales response model. Letting model parameters vary with past discounting activity accommodates the possibility that market response changes with firms' discounting policies. In the normative model, we use the estimates obtained in the descriptive model to determine optimal retailer and manufacturer prices over time. The results of the descriptive model indicate that promotions have positive contemporaneous effects on sales accompanied by negative future effects on baseline sales. The results of the normative model suggest that the higher-share brands in our data tend to overpromote while the lower-share brands do not promote frequently enough. We project that the use of our model could improve manufacturers' profits by as much as 7% to 31%. More generally, the normative results indicate that i) if deals become more effective in the current period, i.e., if consumers are more price sensitive, promotions should be used more frequently; and ii) as the negative dynamic effect of discounts on sales increases, the optimal level of discounting should go down. Without our approach, it would be difficult to make this trade-off exact. Finally, we demonstrate that these dynamic effects provide another perspective to the marketing literature regarding the existence of promotions.