Showing papers by "University of Notre Dame published in 1994"

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.

Secularization as Declining Religious Authority

Abstract: On entend generalement par secularisation, le declin de l'autorite religieuse. L'article propose de souligner trois points : l'autorite religieuse mise en rapport avec les recents developpements en theorie sociale, l'etat actuel de la litterature relatant la secularisation, et une approche Weberienne de l'analyse sociologique de la religion. De nouvelles hypotheses concernant les relations entre la religion et les mouvements sociaux sont a etablir, afin de mieux saisir de maniere conceptuelle et empirique la secularisation au sein de societes, d'organisations et d'individus

A Bayesian approach to image expansion for improved definition

Abstract: Accurate image expansion is important in many areas of image analysis. Common methods of expansion, such as linear and spline techniques, tend to smooth the image data at edge regions. This paper introduces a method for nonlinear image expansion which preserves the discontinuities of the original image, producing an expanded image with improved definition. The maximum a posteriori (MAP) estimation techniques that are proposed for noise-free and noisy images result in the optimization of convex functionals. The expanded images produced from these methods will be shown to be aesthetically and quantitatively superior to images expanded by the standard methods of replication, linear interpolation, and cubic B-spline expansion. >

Feedback control of Petri nets based on place invariants

Abstract: This paper describes a method for constructing a Petri net feedback controller for a discrete event system modeled by a Petri net. The controller enforces a set of linear constraints on the plant and consists of places and arcs. It is computed using the concept of Petri net place invariants. The size of the controller is proportional to the number of constraints which must be satisfied. The method is very attractive computationally, and it makes possible the systematic design of Petri net controllers for complex industrial systems. >

Host fidelity is an effective premating barrier between sympatric races of the apple maggot fly

Abstract: Models of sympatric speciation for phytophagous insects posit a central role for host plant-associated mating as a premating isolating mechanism in lieu of geographic barriers to gene flow. Here, by means of three mark-and-recapture studies, we confirm that host fidelity (i.e., the tendency of an insect to reproduce on the same host species that it used in earlier life-history stages) restricts gene flow between sympatric apple- and hawthorn-infesting races of Rhagoletis pomonella (Diptera: Tephritidae) to approximately 6% per generation. Genetically based differences in host preference, adult eclosion under the "correct" host species, and allochronic isolation contribute to host fidelity in various degrees in the races. The results verify that host-associated adaptation can produce reproductive isolation as a correlated character (a key premise of sympatric speciation). The study also represents one of the few or perhaps only example in animals where the intra-specific isolating effects of specific phenotypes have been quantified in nature.

Housework, paid work, and depression among husbands and wives.

Abstract: The National Survey of Households and Families was used to test competing explanations of how the distribution of housework and paid work among couples affects depressive symptomatology. Considerations of equity predict that the fair distribution of labor across spouses will alleviate depression, while role theory predicts that the performance of multiple, engaging roles will inhibit depression, irrespective of equity across spouses. Results confirm that paid employment is associated with reduced depression among both husbands and wives until work hours exceed an upper threshold. However, time spent in housework is universally associated with increased depression, no matter what other role constellations exist. Little evidence supports the notion that equity in the division of labor (either paid or unpaid) inhibits depression, but perceptions of equity are significantly associated with lower levels of depression. In particular, husbands are strongly affected by perceived equity in the performance of paid work, while wives are strongly affected by perceived equity in the performance of housework.

Why do people say nasty things about self-reports?

Abstract: paper, I would have offered a paradoxical analysis, 'Accept as is - in spite of the author's sensitive appreciation of the strengths and liabilities of self-report measures'. The remainder of this comment will attempt to flesh-out the logic and the paradox behind my hypothetical assessment. Paradox rarely rears its ugly head in science, yet in spite of careful analyses like Spector's, and growing evidence of the validity of self-reports, it seems as if self-report-bashing might be an article of faith of some Scientific Apostle's Creed, 'I believe in good science; the empirical determination of theory choice, the control of extraneous variables, and the fallibility of self-report measures . . .' Spector (1994) acknowledges that cross-sectional self-report studies are sometimes inadequate. At times the problems are due to the studies' passive observational nature (and might be equally problematic had non-self-report measures been employed) and sometimes due to the self-report measurement strategy itself. The former cluster of problems should not be heard as a critique of self-reports per se, so I will instead direct my attention to the latter group of problems. There are known contaminations to self-report measures (e.g. social desirability, selective memory, etc.) that need to be considered. However, Donald Campbell's famous aphorism that good scientists are ontological realists but epistemological fallibalists - suggests that the fallibility of self-reports is not in itself a cogent critique. The immediate question arises: What measurement strategy do you propose to use instead of a self-report (e.g. behavioral, physiological, significant-other, expert judge, archival), and what are the grounds for believing that your alternative measurement strategy is less fallible than a self-report?

On the motion of heavy quarks inside hadrons: universal distributions and inclusive decays

Abstract: In previous papers we have pointed out that there exists a QCD analog of the phenomenological concept of the so-called Fermi motion for the heavy quark inside a hadron. Here we show in a more detailed way how this comes about and we analyze the limitations of this concept. Nonperturbative as well as perturbative aspects are included. We emphasize both similarities and differences to the well-known treatment of deep inelastic lepton-nucleon scattering. We derive a model-independent lower bound on the kinetic energy of the heavy quark inside the hadron.

sine oculis is a homeobox gene required for Drosophila visual system development.

Abstract: The somda (sine oculis-medusa) mutant is the result of a P element insertion at position 43C on the second chromosome. somda causes aberrant development of the larval photoreceptor (Bolwig's) organ and the optic lobe primordium in the embryo. Later in development, adult photoreceptors fail to project axons into the optic ganglion. Consequently optic lobe development is aborted and photoreceptor cells show age-dependent retinal degeneration. The so gene was isolated and characterized. The gene encodes a homeodomain protein expressed in the optic lobe primordium and Bolwig's organ of embryos, in the developing adult visual system of larvae, and in photoreceptor cells and optic lobes of adults. In addition, the SO product is found at invagination sites during embryonic development: at the stomadeal invagination, the cephalic furrow, and at segmental boundaries. The mutant somda allele causes severe reduction of SO embryonic expression but maintains adult visual system expression. Ubiquitous expression of the SO gene product in 4-8-hr embryos rescues all somda mutant abnormalities, including the adult phenotypes. Thus, all deficits in adult visual system development and function results from failure to properly express the so gene during embryonic development. This analysis shows that the homeodomain containing SO gene product is involved in the specification of the larval and adult visual system development during embryogenesis.

Influences on the quality of supervisor–subordinate relations: The role of time‐pressure, organizational commitment, and locus of control

Abstract: Despite a growing literature devoted to the study of differences in the quality of leader–member exchange, little empirical evidence is available concerning factors that influence the degree of differentiation among leader–member dyads on the dimension of quality of working relationships. As time-pressure has been suggested as one potential influence, the impact of time-based stress on leader–member exchange was examined with a sample of 138 loan officers representing 24 bank branches. Results indicated that unit-level variability on leader–member exchange was inversely related with time-based stress, while unit-level mean on leader–member exchange was positively related with time-based stress. Additionally, leader–member exchange acted as a mediator of the relation between employee locus of control (a suspected antecedent of dyadic quality) and organizational commitment (a suspected outcome), while employee locus of control correlated with leader–member exchange, and leader–member exchange correlated with employee organizational commitment. The results suggest the usefulness of considering time-based stress in conjunction with current models of leadership.

Reynolds Number Effects in Wall-Bounded Turbulent Flows

Abstract: This paper reviews the state of the art of Reynolds number effects in wall-bounded shear-flow turbulence, with particular emphasis on the canonical zero-pressure-gradient boundary layer and two-dimensional channel flow problems. The Reynolds numbers encountered in many practical situations are typically orders of magnitude higher than those studied computationally or even experimentally. High-Reynolds number research facilities are expensive to build and operate and the few existing are heavily scheduled with mostly developmental work. For wind tunnels, additional complications due to compressibility effects are introduced at high speeds. Full computational simulation of high-Reynolds number flows is beyond the reach of current capabilities. Understanding of turbulence and modeling will continue to play vital roles in the computation of high-Reynolds number practical flows using the Reynolds-averaged Navier-Stokes equations. Since the existing knowledge base, accumulated mostly through physical as well as numerical experiments, is skewed towards the low Reynolds numbers, the key question in such high-Reynolds number modeling as well as in devising novel flow control strategies is: what are the Reynolds number effects on the mean and statistical turbulence quantities and on the organized motions? Since the mean flow review of Coles (1962), the coherent structures, in low-Reynolds number wall-bounded flows, have been reviewed several times. However, the Reynolds number effects on the higher-order statistical turbulence quantities and on the coherent structures have not been reviewed thus far, and there are some unresolved aspects of the effects on even the mean flow at very high Reynolds numbers. Furthermore, a considerable volume of experimental and full-simulation data have been accumulated since 1962. The present article aims at further assimilation of those data, pointing to obvious gaps in the present state of knowledge and highlighting the misunderstood as well as the ill-understood aspects of Reynolds number effects.

Developmental differences in cognitive diatheses for child depression.

Abstract: We studied developmental changes in the relation between cognitive style (i.e., attributional style and cognitive errors) and depression in children. Subjects included 409 fourth-, sixth-, and eighth-grade school children. We hypothesized (1) that evidence congruent with a cognitive diathesis model of depression would emerge with development across middle childhood, (2) that Event × Cognitive Style × Age interactions would be specific to some domains of stressful events but not others, and (3) that interactions would be especially prominent in domains that children regarded as personally important. Hierarchical multiple regressions indicated that cognitive style moderated the relation between events and self-reported depressive symptoms only in later childhood, and that such interactions were specific to certain domains of stressful events and cognitions. The importance of distinguishing among types of stress and cognitions in future tests of diathesis-stress models of childhood depression are discussed. Implications of developmental differences in the psychopathology of child depression also emerge.

Job search activities: an examination of changes over time

Abstract: Existing job search research has been criticized for ignoring the dynamic nature of search. This study examined three models of changes in search behavior over time: sequential, learned change, and emotional response. Data on search behaviors were collected from a sample of 186 college and vocational-technical school graduates early in their search, at graduation, and again 3 months following graduation for individuals who remained unemployed. Job searchers decreased the intensity of their search, increased their use of informal sources, and reduced their emphasis on information related to the availability of jobs between early search and graduation. These changes were reversed following graduation. This pattern is most consistent with the sequential model, which suggests that individuals first search broadly to develop a pool of potential jobs, then examine jobs within that pool in detail, reopening the search only if the initial pool does not lead to an acceptable job offer.

Frequency domain optimal control strategies for aseismic protection

Abstract: The application of frequency domain techniques for optimal control of civil engineering structures under seismic loading is described in this paper. The H2 and H gamma control techniques are described in terms of a general block diagram problem formulation. Numerical examples illustrate the application and delineate the advantages of the methodology. It is shown that frequency domain design methods can be effectively used to optimally control a structure using output feedback of acceleration measurements, and to selectively shape the output structural response in a desirable manner.

Relativistic all-order many-body calculations of the n=1 and n=2 states of heliumlike ions

Abstract: An all-order procedure is used to determine the energies of the n=1 and n=2 states of heliumlike ions with nuclear charges in the range Z=3--100. The Coulomb energies and wave functions are obtained from a no-pair Hamiltonian by an iterative scheme that sums all orders of many-body perturbation theory. The Breit energy is determined by taking the expectation value of the instantaneous Breit Hamiltonian between the Coulomb wave functions. Corrections for the frequency dependence of the Breit interaction and for two Breit interactions are included. Quantum-electrodynamic and mass-polarization corrections are taken from Drake's unified method [Can. J. Phys. 66, 586 (1988)]. The resulting energies are complete through order (Z\ensuremath{\alpha}${)}^{3}$ a.u. and include new terms of order (Z\ensuremath{\alpha}${)}^{4}$ a.u. Comparisons are made with experiment and with recent configuration-interaction calculations.

Quantum cellular automata: the physics of computing with arrays of quantum dot molecules

Abstract: We discuss the fundamental limits of computing using a new paradigm for quantum computation, cellular automata composed of arrays of coulombically coupled quantum dot molecules, which we term quantum cellular automata (QCA). Any logical or arithmetic operation can be performed in this scheme. QCA's provide a valuable concrete example of quantum computation in which a number of fundamental issues come to light. We examine the physics of the computing process in this paradigm. We show to what extent thermodynamic considerations impose limits on the ultimate size of individual QCA arrays. Adiabatic operation of the QCA is examined and the implications for dissipationless computing are explored. >

Object recognition contributions to figure-ground organization: Operations on outlines and subjective contours

Abstract: In previous research, replicated here, we found that some object recognition processes influence figure-ground organization. We have proposed that these object recognition processes operate on edges (or contours)detected early in visual processing, rather than on regions. Consistent with this proposal, influences from object recognition on figure-ground organization were previously observed in both pictures and stereograms depicting regions of different luminance, but not in randomdot stereograms, where edges arise late in processing (Peterson & Gibson, 1993). In the present experiments, we examined whether or not two other types of contours—outlines and subjective contours—enable object recognition influences on figure-ground organization. For both types of contours we observed a pattern of effects similar to that originally obtained with luminance edges. The results of these experiments are valuable for distinguishing between alternative views of the mechanisms mediating object recognition influences on figure-ground organization. In addition, in both Experiments 1 and 2, fixated regions were seen as figure longer than nonfixated regions, suggesting that fixation location must be included among the variables relevant to figure-ground organization.

Optical properties of zinc-blende CdSe and ZnxCd1-xSe films grown on GaAs.

Abstract: We present room-temperature ellipsometric measurements of the dielectric function of ${\mathrm{Zn}}_{\mathit{x}}$${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$Se single-crystal films grown on (001)GaAs in the 1.5--6.0-eV energy region x ranging from 0 to 1. We identify the ${\mathit{E}}_{0}$, ${\mathit{E}}_{0}$+${\mathrm{\ensuremath{\Delta}}}_{0}$, ${\mathit{E}}_{1}$, ${\mathit{E}}_{1}$+${\mathrm{\ensuremath{\Delta}}}_{1}$, and ${\mathit{E}}_{2}$ threshold energies using the CdSe band structure calculated with a nonlocal empirical pseudopotential method. We find that the contact exciton effect has to be included in the calculated dielectric function of CdSe in order to obtain good agreement with our measurements. A compositon-dependent critical-point analysis of the ${\mathit{E}}_{1}$ and ${\mathit{E}}_{1}$+${\mathrm{\ensuremath{\Delta}}}_{1}$ structures has been performed. We also find that the spin-orbit-splitting band gap ${\mathrm{\ensuremath{\Delta}}}_{1}$(x), the linewidths, and the excitonic angles are about maximum at x=0.5, which we attribute to the statistical fluctuation of the alloy composition. Finally, the ${\mathit{E}}_{1}$ and ${\mathit{E}}_{1}$+${\mathrm{\ensuremath{\Delta}}}_{1}$ critical-point amplitudes cannot be understood by the one-electron approximation, confirming the existence of strong excitonic effects.

Modelling tides in the western North Atlantic using unstructured graded grids

Abstract: This paper describes grid convergence studies for a finite-element-based tidal model of the western North Atlantic, Gulf of Mexico and Caribbean. The very large computational domain used for this tidal model encompasses both the coastal and the deep ocean and facilitates the specification of boundary conditions. Due to the large variability in depths as well as scale content of the tides within the model domain, an optimal unstructured graded grid with highly variable finite element areas is developed which significantly reduces the size of the discrete problem while improving the accuracy of the computations. The convergence studies include computations for a sequence of regularly discretized grids ranging from a very coarse 1.6° × 1.6° mesh to a very fine 6′ × 6′ to 12′ × 12′ mesh as well as unstructured graded grids with resolutions varying between 1.6° and 5′ within each mesh. Resolution requirements are related to depth, gradients in topography as well as the resolution of the coastal boundary. The final optimal graded grid has a tidal response which is comparable to that of the finest regular grid in most regions. The optimal graded grid is then forced with Schwiderski's (1979, 1980, 1981a–g) global model on the open ocean boundary and tidal potential forcing functions within the interior domain. The structure of the tides is examined, computed co-tidal charts are presented and comparisons are made between the computed results and field data at 77 stations within the model domain. DOI: 10.1034/j.1600-0870.1994.00007.x

Shallow water modeling in spherical coordinates: equation formulation, numerical implementation, and application

Abstract: One class of surface water models is the shallow water models obtained by depth-averaging the microscale mass and momentum balances. Application of shallow water models to large scale problems (on the order of 1000's of km) requires the use of spherical coordinates. Traditionally, balance laws in spherical coordinates are derived by simply expanding the spatial operators in the standard depth-averaged equations. However, the equations themselves are based on an assumed planar surface so that an inconsistency exists between the derivation and the interpretation. In this article, a method is presented that properly accounts for the curvature of the Earth during the depth-averaging procedure. The derivation gives rise to new terms in both the continuity and momentum balances, terms that we refer to as curvature terms. A scaling analysis evaluates the magnitude of the terms. It is shown that the curvature term in the continuity balance is insignificant when the vertical velocity is small, i.e., at least four ...

On the mechanism of unsteady shock oscillation in shock wave/turbulent boundary layer interactions

Abstract: An experimental investigation into the mechanism of shock wave oscillation in compression ramp-generated shock wave/turbulent boundary layer interactions is presented. Particular emphasis is focused upon documenting the respective roles played by both burst-sweep events in the turbulent boundary layer immediately upstream of the interaction and the downstream separated shear layer upon unsteady shock front motion. Unlike the majority of compression ramp experiments which involve bulk separation and large-scale shock motion, consideration is given here to comparatively “weak” interactions in which the streamwise spatial excursion of the shock front is always less than one boundary layer thickness. In this manner any shock motion due to upstream burst-sweep events should be more apparent in relation to that oscillation associated with the separated region. A discrete Hilbert transform-based conditional sampling technique is used to obtain wall pressure measurements conditioned to burst-sweep events. The conditional sampling technique forms the basis by which the instantaneous shock motion is conditioned to the occurrence of upstream bursting. The relationship between the separation bubble and shock motion is also explored in detail. The results of the experiments indicate that the separation bubble represents a first-order effect on shock oscillation. Although it is demonstrated theoretically that the burst-sweep cycle can also give rise to unsteady shock motion of much lower amplitude, the experiments clearly demonstrate that there is no discernible statistical relationship between burst events and spanwise coherent shock front motion.

Drop formation during coating of vertical fibres

Abstract: When the coating film around a vertical fibre exceeds a critical thickness hc, the interfacial disturbances triggered by Rayleigh instability can undergo accelerated growth such that localized drops much larger in dimension than the film thickness appear. We associate the initial period of this strongly nonlinear drop formation phenomenon with a self-similar intermediate asymptotic blow-up solution to the long-wave evolution equation which describes how static capillary forces drain fluid into the drop. Below hc, we show that strongly nonlinear coupling between the mean flow and axial curvature produces a finite-amplitude solitary wave solution which prevents local finite-time blow up and hence disallows further growth into drops. We thus estimate hc by determining the existence of solitary wave solutions. This is accomplished by a matched asymptotic analysis which joins the capillary outer region of a large solitary wave to the thin-film inner region. Our estimate of hc = 1.68R3H–2, where R is the fibre radius and H is the capillary length H = (σ/ρg)½, is favourably compared to experimental data.

Groups definable in local fields and pseudo-finite fields

Abstract: Using model-theoretic methods we prove: If G is a Nash group over the real or p-adic field, then there is a Nash isomorphism between neighbourhoods of the identity of G and of the set of F-rational points of an algebraic group defined over F. Let G be a connected affine Nash group over ℝ. Then G is Nash isogeneous with the (real) connected component of the set of real points of an algebraic group defined over ℝ. Let G be a group definable in a pseudo-finite field F. Then G is definably virtually isogeneous with the set of F-rational points of an algebraic group defined over F.

Cold Acclimation, Diapause, and Geographic Origin Affect Cold Hardiness in Eggs of Aedes albopictus (Diptera: Culicidae)

Abstract: Eggs of five strains of Aedes albopictus (Skuse) were obtained in both diapause and nondiapause conditions and exposed to various cold acclimation regimes in the laboratory, after which they were subjected to diverse chilling treatments. Larvae that survived chilling as eggs survived to the pupal stage. Eggs of Aedes aegypti (L.) and Aedes triseriatus (Say) were included as control species. Eggs of temperate Ae. albopictus were more cold-hardy than eggs of Ae. aegypti but less cold-hardy than the eggs of Ae. triseriatus . Cold acclimation and diapause enhanced cold hardiness of only temperate Ae. albopictus . Cold acclimation had a greater influence on cold hardiness than did diapause. Both the temperature and the duration of cold acclimation modulated cold hardiness. Cold hardiness induced in the laboratory was similar to cold hardiness induced in the field in northern Indiana. The cold hardiness of Ae. albopictus from central Florida was intermediate in comparison with temperate and tropical strains. Tropical Brazilian Ae. albopictus and tropical Asian Ae. albopictus were similar in cold hardiness.

Observation of multiple Andreev reflections in superconducting tunnel junctions.

Abstract: We describe measurements on high-current-density Nb-${\mathrm{AlO}}_{\mathit{x}}$-Nb tunnel junctions and demonstrate that the development of excess subgap current with increasing barrier transparency is the result of multiple Andreev reflections. We present a model for the barrier consistent with measured junction resistance, the high transparency required for multiple traversals, and the observed single-particle and Josephson characteristics. We argue that excess subgap current and subharmonic gap structure in superconducting tunnel junctions are generally likely to be due to pinhole defects in the barriers.