Showing papers by "Florida Atlantic University published in 1998"

Understanding the Influence of National Culture on the Development of Trust

Abstract: Increasingly, researchers from a variety of business disciplines are finding that trust can lower transaction costs, facilitate interorganizational relationships, and enhance manager-subordinate relationships. At the same time, we see a growing trend toward globalization—in establishing alliances, managing and hiring employees, and entering new markets. These trends suggest a need to view the concept of trust from the perspective of national culture. Drawing on theories from several disciplines, we develop a framework that identifies and describes five cognitive trust-building processes that help explain how trust develops in business contexts. We include a series of research propositions demonstrating how societal norms and values influence application of the trust-building processes, and we discuss implications for theory and practice.

Reconsidering Changes in Parent-Child Conflict across Adolescence: A Meta-Analysis

Abstract: A series of meta-analyses addresses whether and how parent-child conflict changes during adolescence and factors that moderate patterns of change The meta-analyses summarize results from studies of change in parent-child conflict as a function of either adolescent age or pubertal maturation Three types of parent-adolescent conflict are examined: conflict rate, conflict affect, and total conflict (rate and affect combined) The results provide little support for the commonly held view that parent-child conflict rises and then falls across adolescence, although conclusions regarding pubertal change as well as conflict affect are qualified by the limited number of studies available Two diverging sets of linear effects emerged, one indicating a decline in conflict rate and total conflict with age and the other indicating an increase in conflict affect with both age and pubertal maturation In age meta-analyses, conflict rate and total conflict decline from early adolescence to mid-adolescence and from mid-adolescence to late adolescence; conflict affect increases from early adolescence to mid-adolescence Puberty meta-analyses revealed only a positive linear association between conflict affect and pubertal maturation Effect-size patterns varied little in follow-up analyses of potential moderating variables, implying similarities in the direction (although not the magnitude) of conflict across parent-adolescent dyads, reporters, and measurement procedures

Does low self-regard invite victimization?

Abstract: Two hypotheses were tested. The first was that low self-regard contributes over time to victimization by peers. The second was that behavioral vulnerabilities (e.g., physical weakness, manifest anxiety, poor social skills) are more likely to lead to victimization over time when children have low self-regard than when they are "self-protected" by healthy self-regard. Participants were 189 third-through 7th-grade boys and girls; data were collected in the fall and the spring of the school year. Both hypotheses were supported, especially when self-regard was assessed in terms of self-perceived peer social competence. In addition, the experience of being victimized led to diminished self-regard over time. Poor self-concept may play a central role in a vicious cycle that perpetuates and solidifies a child's status as a victim of peer abuse.

Relationships of leaf dark respiration to leaf nitrogen, specific leaf area and leaf life-span: a test across biomes and functional groups.

Abstract: Based on prior evidence of coordinated multiple leaf trait scaling, we hypothesized that variation among species in leaf dark respiration rate (Rd) should scale with variation in traits such as leaf nitrogen (N), leaf life-span, specific leaf area (SLA), and net photosynthetic capacity (/4max)- However, it is not known whether such scaling, if it exists, is similar among disparate biomes and plant functional types. We tested this idea by examining the interspecific relationships between Rd measured at a standard temperature and leaf life-span, N, SLA and ^max for 69 species from four functional groups (forbs, broad-leafed trees and shrubs, and needle-leafed coni- fers) in six biomes traversing the Americas: alpine tun- dra/subalpine forest, was positively related to area-based leaf N within functional groups and for all species pooled, but not when comparing among species within any site. At all sites, mass-based Rd (Rd.mass) de- creased sharply with increasing leaf life-span and was positively related to SLA and mass-based Amax and leaf

Board Composition, Managerial Ownership, and Firm Performance: An Empirical Analysis

Abstract: Simultaneous-equations techniques are being used more often in corporate governance research. However, when no formal theoretical model is present, misspecification in one or more of the first or second stage regression is likely, causing empirical results to be seriously biased. This paper investigates the combined effect of ownership structure and board composition on corporate performance, using an instrumental-variables approach that allows for sensitivity analysis. The results indicate that managerial ownership, board composition, and Tobin's Q are jointly determined. More importantly, final results are very sensitive to reasonable changes in both the overall model specification and to the set of instruments. The results strongly suggest that in corporate governance research, sensitivity analysis is essential, results should be interpreted cautiously, and ordinary least squares results should not be casually dismissed.

The relation of birth order and socioeconomic status to children's language experience and language development

Abstract: Variation in mothers' child-directed speech and in their children's rates of language development were examined as a function of child birth order and family socioeconomic status (SES). A total of 63 children between 18 and 29 months were recorded in dyadic interaction with their mothers on two separate occasions, 10 weeks apart. The children included first and later boms who came from high-SES and mid-SES backgrounds. Analyses of the children's speech at the second visit showed that the first-bom children were more advanced in lexical and grammatical development than the later-bom children, and that the later-bom children were more advanced in the development of conversational skill. High-SES children showed more advanced lexical development than mid-SES children. These differences are interpreted as the result of differences in language learning experience associated with birth order and SES, some of which were in evidence in the mothers' speech recorded at the first visit. With respect to theories of language acquisition, these findings suggest that language experience plays a nontrivial role in language development, and that the nature of that role is different for different components of language development. With respect to general developmental consequences of birth order and SES, the findings indicate that differences in early language experience may set the stage for later developmental differences, but that when long-term and pervasive differences are observed, as is the case for SES-related differences in achievement, it is likely that there are pervasive and continuing differences in experience.

Why are some verbs learned before other verbs? Effects of input frequency and structure on children's early verb use

Abstract: This study investigated the extent to which the nature of verb input accounts for the order in which children acquire verbs We assessed the nature of verb input using a combined sample of the speech of 57 mothers addressing their Stage I children We assessed the order of verb acquisition using as our database a combined sample of those children's speech 10 weeks later and using as our measure of order of acquisition the frequency of verb occurrence The first set of analyses established the validity of this measure of acquisition order by comparing it with order of acquisition data obtained from checklist and diary data The second set of analyses revealed that three properties of the input were significant predictors of the order of acquisition of the 25 verbs that were the focus of this study The predictive properties of input were the total frequency, final position frequency, and diversity of syntactic environments in which the verbs appeared These findings suggest that the way verbs appear in input influences their ease of acquisition More specifically, the effect of syntactic diversity in input provides support for the syntactic bootstrapping account of how children use structural information to learn the meaning of new verbs

Board Composition, Managerial Ownership, and Firm Performance: An Empirical Analysis

Abstract: Our objective is to examine the sensitivity of simultaneous equations techniques in corporate governance research. We model Tobin's Q, board composition, and managerial ownership using a three-equation instrumental variables approach, with two specifications and four instruments. We find that the variables are jointly determined. However, results depend strongly on the specification of the model and the instruments. We conclude that results using simultaneous equations methods must be interpreted cautiously, OLS estimates should not be casually dismissed, and that sensitivity analysis is essential when estimating an empirical model whose structure is uncertain.

Software engineering as seen through its research literature: a study in co-word analysis

Abstract: This empirical research demonstrates the effectiveness of content analysis to map the research literature of the software engineering discipline. The results suggest that certain research themes in software engineering have remained constant, but with changing thrusts. Other themes have arisen, matured, and then faded as major research topics, while still others seem transient or immature. Co-word analysis is the specific technique used. This methodology identifies associations among publication descriptors (indexing terms) from the ACM Computing Classification System and produces networks of descriptors that reveal these underlying patterns. This methodology is applicable to other domains with a supporting corpus of textual data. While this study utilizes index terms from a fixed taxonomy, that restriction is not inherent; the descriptors can be generated from the corpus. Hence, co-word analysis and the supporting software tools employed here can provide unique insights into any discipline's evolution.

An Investigation of Neutrino-driven Convection and the Core Collapse Supernova Mechanism Using Multigroup Neutrino Transport

Abstract: We investigate neutrino-driven convection in core collapse supernovae and its ramifications for the explosion mechanism. We begin with a postbounce model that is optimistic in two important respects: (1) we begin with a 15 M☉ precollapse model, which is representative of the class of stars with compact iron cores; (2) we implement Newtonian gravity. Our precollapse model is evolved through core collapse and bounce in one dimension using multigroup (neutrino energy-dependent) flux-limited diffusion (MGFLD) neutrino transport and Newtonian Lagrangian hydrodynamics, providing realistic initial conditions for the postbounce convection and evolution. Our two-dimensional simulation begins at 12 ms after bounce and proceeds for 500 ms. We couple two-dimensional piecewise parabolic method (PPM) hydrodynamics to precalculated one-dimensional MGFLD neutrino transport. (The neutrino distributions used for matter heating and deleptonization in our two-dimensional run are obtained from an accompanying one-dimensional simulation. The accuracy of this approximation is assessed.) For the moment, we sacrifice dimensionality for realism in other aspects of our neutrino transport. MGFLD is an implementation of neutrino transport that simultaneously (1) is multigroup and (2) simulates with sufficient realism the transport of neutrinos in opaque, semitransparent, and transparent regions. Both are crucial to the accurate determination of postshock neutrino heating, which sensitively depends on the luminosities, spectra, and flux factors of the electron neutrinos and antineutrinos emerging from their respective neutrinospheres. By 137 ms after bounce, we see neutrino-driven convection rapidly developing beneath the shock. By 212 ms after bounce, this convection becomes large scale, characterized by higher entropy, expanding upflows and lower entropy, denser, finger-like downflows. The upflows reach the shock and distort it from sphericity. The radial convection velocities at this time become supersonic just below the shock, reaching magnitudes in excess of 109 cm s-1. Eventually, however, the shock recedes to smaller radii, and at ~500 ms after bounce there is no evidence in our simulation of an explosion or of a developing explosion. Our angle-averaged density, entropy, electron fraction, and radial velocity profiles in our two-dimensional model agree well with their counterparts in our accompanying one-dimensional MGFLD run above and below the neutrino-driven convection region. In the convection region, the one-dimensional and angle-averaged profiles differ somewhat because (1) convection tends to flatten the density, entropy, and electron fraction profiles, and (2) the shock radius is boosted somewhat by convection. However, the differences are not significant, indicating that, while vigorous, neutrino-driven convection in our model does not have a significant impact on the overall shock dynamics. The differences between our results and those of other groups are considered. These most likely result from differences in (1) numerical hydrodynamics methods; (2) initial postbounce models, and, most important; (3) neutrino transport approximations. We have compared our neutrino luminosities, rms energies, and inverse flux factors with those from the exploding models of other groups. Above all, we find that the neutrino rms energies computed by our multigroup (MGFLD) transport are significantly lower than the values obtained by Burrows and coworkers, who specified their neutrino spectra by tying the neutrino temperature to the matter temperature at the neutrinosphere and by choosing the neutrino degeneracy parameter arbitrarily, and by Herant and coworkers in their transport scheme, which (1) is gray and (2) patches together optically thick and thin regions. The most dramatic difference between our results and those of Janka and Muller is exhibited by the difference in the net cooling rate below the gain radii: Our rate is 2-3 times greater during the critical 50-100 ms after bounce. We have computed the mass and internal energy in the gain region as a function of time. Up to ~150 ms after bounce, we find that both increase as a result of the increasing gain region volume, as the gain and shock radii diverge. However, at all subsequent times, we find that the mass and internal energy in the gain region decrease with time in accordance with the density falloff in the preshock region and with the flow of matter into the gain region at the shock and out of the gain region at the gain radius. Therefore, we see no evidence in the simulations presented here that neutrino-driven convection leads to mass and energy accumulation in the gain region. We have compared our one- and two-dimensional densities, temperatures, and electron fractions in the region below the electron neutrino and antineutrino gain radii, above which the neutrino luminosities are essentially constant (i.e., the neutrino sources are entirely enclosed), in an effort to assess how spherically symmetric our neutrino sources remain during our two-dimensional evolution, and therefore, in an effort to assess our use of precalculated one-dimensional MGFLD neutrino distributions in calculating the matter heating and deleptonization. We find no difference below the neutrinosphere radii. Between the neutrinosphere and gain radii we find no differences with obvious ramifications for the supernova outcome. We note that the interplay between neutrino transport and convection below the neutrinospheres is a delicate matter and is discussed at greater length in another paper (Mezzacappa and coworkers). However, the results presented therein do support our use of precalculated one-dimensional MGFLD in the present context. Failure in our "optimistic" 15 M☉ Newtonian model leads us to conclude that it is unlikely, at least in our approximation, that neutrino-driven convection will lead to explosions for more massive stars with fatter iron cores or in cases in which general relativity is included.

Proteinlike molecular architecture: Biomaterial applications for inducing cellular receptor binding and signal transduction

Abstract: The development of biomaterials with desirable biocompatibility has presented a difficult challenge for tissue engineering researchers. First and foremost, materials themselves tend to be hydrophobic and/or thrombogenic in nature, and face compatibility problems upon implantation. To mediate this problem, researchers have attempted to graft protein fragments onto biomaterial surfaces to promote endothelial cell attachment and minimize thrombosis. We envisioned a novel approach, based on the capability of biomolecules to self-assemble into well-defined and intricate structures, for creating biomimetic biomaterials that promote cell adhesion and proliferation. One of the most intriguing self-assembly processes is the folding of peptide chains into native protein structures. We have developed a method for building protein-like structural motifs that incorporate sequences of biological interest. A lipophilic moiety is attached onto a N alpha-amino group of peptide chain, resulting in a "peptide-amphiphile." The alignment of amphiphilic compounds at the lipid-solvent interface is used to facilitate peptide alignment and structure initiation and propagation, while the lipophilic region absorbs to hydrophobic surfaces. Peptide-amphiphiles containing potentially triple-helical or alpha-helical structural motifs have been synthesized. The resultant head group structures have been characterized by CD spectroscopy and found to be thermally stable over physiological temperature ranges. Triple-helical peptide-amphiphiles have been applied to studies of surface modification and cell receptor binding. Cell adhesion and spreading was promoted by triple-helical peptide-amphiphiles. Cellular interaction with the type IV collagen sequence alpha 1(IV) 1263-1277 increased signal transduction, with both the time and level of induction dependent upon triple-helical conformation. Collectively, these results suggest that peptide-amphiphiles may be used to form stable molecular structure on biomaterial surfaces that promote cellular activities and improve biocompatibility.

Minimal lipidation stabilizes protein-like molecular architecture

Abstract: Peptide-amphiphiles with collagen-model head groups and dialkyl chain tails have been shown previously to self-assemble into highly ordered polyPro II-like triple-helical structures when dissolved in aqueous subphases. In the present study, we have examined peptide-amphiphiles containing monoalkyl chain tails for similar self-assembly behaviors. The structure of a collagen-model peptide has been characterized with and without an N-terminal hexanoic acid (C6) modification. Evidence for a self-assembly process of both the peptide and peptide-amphiphile has been obtained from (a) circular dichroism spectra and melting curves characteristic of triple-helices, (b) one-dimensional NMR spectra indicative of stable triple-helical structure at low temperatures and melted triple helices at high temperatures, and (c) pulsed-field gradient NMR experiments demonstrating different self-diffusion coefficients between proposed triple-helical and non-triple-helical species. The peptide-amphiphile appeared to form monomeri...

Dynamic cortical activity in the human brain reveals motor equivalence

Abstract: That animals and humans can accomplish the same goal using different effectors and different goals using the same effectors attests to the remarkable flexibility of the central nervous system This phenomenon has been termed ‘motor equivalence’1,2, an example being the writing of a name with a pencil held between the toes or teeth The idea of motor equivalence has reappeared because single-cell studies in monkeys have shown that parameters of voluntary movement (such as direction) may be specified in the brain, relegating muscle activation to spinal interneuronal systems3,4 Using a novel experimental paradigm5 and a full-head SQUID (for superconducting quantum interference device) array to record magnetic fields corresponding to ongoing brain activity, we demonstrate: (1), a robust relationship between time-dependent activity in sensorimotor cortex and movement velocity, independent of explicit task requirements; and (2) neural activations that are specific to task demands alone It appears, therefore, that signatures of motor equivalence in humans may be found in dynamic patterns of cortical activity

Calibration of stewart platforms and other parallel manipulators by minimizing inverse kinematic residuals

Abstract: This paper focuses on the accuracy enhancement of Stewart platforms through kinematic calibration The calibration problem is formulated in terms of a measurement residual, which is the discrepancy between the measured leg length and the computed leg length With this formulation, one is able to identify kinematic error parameters of the Stewart platform without the necessity of solving the forward kinematic problem; thus avoiding the numerical problems associated with any forward kinematic solution By this formulation, a concise differential error model with a well-structured identification Jacobian, which relates the pose measurement residual to the errors in the parameters of the platform, is derived Experimental studies confirmed the effectiveness of the method It is also shown in this paper that the proposed approach can be applied to other types of parallel manipulators, assuming that their inverse kinematic solution is simpler than its forward kinematic solution Because this condition is satisfied by almost all parallel manipulators, the method is very useful for kinematic calibration of such machines © 1998 John Wiley & Sons, Inc

Inpatient and Postdischarge Aggression in Mentally Disordered Offenders The Role of Psychopathy

Abstract: Previous research has indicated that psychopathy, as measured by the Hare Psychopathy Checklist is related to violent behavior, recidivism, and career criminality in nonpsychotic, correctional populations. However, the present study is among only a few to investigate the relationship between psychopathy and violence in mentally disordered offenders. Participants (N = 218) were administered the PCL following admission to an inpatient forensic hospital. Significant correlations between the PCL total scores and both nonphysical and physical aggression during the first 2 months of hospitalization were observed. The PCL total scores were also significantly correlated with postdischarge arrests for offenses against persons but not for offenses against property. Both age and PCL total score were significantly related to the total number of aggressive incidents during the first 2 months of hospitalization, but only the PCL total was significantly related to frequency of seclusion or restraint during this period. ...

Testing Gottfredson and Hirschi’s “low self-control” stability hypothesis: An exploratory study

Abstract: In Gottfredson and Hirschi’s (1990)A General Theory of Crime, criminal and analogous behaviors are argued to be the result of a stable individual psychological trait referred to as “low self-control.” In this article, we test the proposition that low self-control is a stable characteristic. We conduct a two-wave panel study that measures the self-reported self-control of college students at two relatively close time points. Our test of the stability hypothesis includes conducting four separate analyses of the data (t-tests, correlations, individual change scores, and HLM analyses). In general, we find that most of the dimensions of self-control, and the overall self-control construct, appear to be relatively stable across this short period of time. However, given that the measurements were taken closely together and that we do not find correlations as strong as might be expected, at points the strength of the stability is somewhat unclear.

The effect of weave pattern and crack propagation direction on mode I delamination resistance of woven glass and carbon composites

Abstract: The effect of weave structure on the interlaminar fracture behavior of orthogonal woven fabric composite laminates has been examined. Crack propagation along the fill and weft yarns, respectively, was considered for plain, twill and 8H-satin glass/epoxy composites, and a 5H-satin carbon/epoxy composite. Fracture testing employed the mode I fracture DCB test specimen. Microscopic details of crack growth in the interply region were considered after fracture testing. The delamination resistance and the difference in fracture toughness between the fill and weft directions increased with increased weave index. Partial debonding of transversely oriented yarns contributed to the delamination resistance. Fracture of debonded fibers referred to as `fiber bridging' was observed in the twill and satin weave glass/epoxy composites, but not in the plain weave glass/epoxy and the 5H-satin weave carbon/epoxy composites. The interlacing of the yarns limited the extent of fiber bridging.

Newborns of mothers with depressive symptoms are physiologically less developed

Abstract: Sixty-three infants of mothers with depressive symptoms were compared on physiology and behavior to infants of nonsymptomatic mothers. The newborns of depressive mothers had greater relative right frontal EEG asymmetry (due to reduced left hemisphere activation), lower vagal tone, and less optimal scores on the Brazelton, suggesting that maternal depressive symptoms during pregnancy may be contributing to newborn neurobehavioral functioning.

Connecting cortical and behavioral dynamics: bimanual coordination

Abstract: For the paradigmatic case of bimanual coordination, we review levels of organization of behavioral dynamics and present a description in terms of modes of behavior. We briefly review a recently developed model of spatiotemporal brain activity that is based on short- and long-range connectivity of neural ensembles. This model is specified for the case of motor and sensorimotor units embedded in the neural sheet. Focusing on the cortical left-right symmetry, we derive a bimodal description of the brain activity that is connected to behavioral dynamics. We make predictions of global features of brain dynamics during coordination tasks and test these against experimental magnetoencephalogram (MEG) results. A key feature of our approach is that phenomenological laws at the behavioral level can be connected to a field-theoretical description of cortical dynamics.

Victimization by peers : Associations with children's reports of mother-child interaction

Abstract: Children who are chronically victimized by peers are at risk for personal difficulties. This study examined whether victimization is associated with mother-child interaction at home. Preadolescents (N = 184; mean age = 11.7 years) reported on their mother's child-rearing practices and on how they cope during conflicts with their mother. Peers reported on victimization at school. Sex-specific links between perceived family interaction and peer victimization were found. For boys, victimization was associated with perceived maternal overprotectiveness, especially when boys reported reacting with fear during mother-child conflict. For girls, victimization was associated with perceived maternal rejection and with girls' reports of aggressive coping during mother-child conflict. Results support the theory that parenting that hinders children's development of gender-salient competencies (autonomy for boys and communion for girls) places children at risk for peer victimization.

Elevated carbon dioxide ameliorates the effects of ozone on photosynthesis and growth: species respond similarly regardless of photosynthetic pathway or plant functional group

Abstract: Due to their different physiological effects, elevated carbon dioxide and elevated ozone might have interactive impacts on plants, and differentially so on plants differing in photosynthetic pathway and growth rate. To test several hypotheses related to these issues, we examined the physiological, morphological and growth responses of six perennial species grown at various atmospheric concentrations of carbon dioxide and ozone. The species involved (two C3 trees: Populus tremuloides Michx., Quercus rubra L.; two C3 grasses: Agropyron smithii Rybd., Koeleria cristata L.; two C4 grasses: Bouteloua curtipendula Michx., Schizachyrium scoparium Michx.) differed in growth form, stomatal conductance and photosynthetic pathway. In situ photosynthesis, relative growth rate (RGR) and its determinants (leaf area ratio, specific leaf area, leaf weight ratio and root weight ratio) were determined via sequential harvests of seedlings that were grown in all combinations of 366 or 672 μmol mol−1 CO2 and 3 or 95 nmol mol−1 O3 over a 101-d period. Elevated CO2 had minimal effect on either photosynthesis or RGR. By contrast, RGR for all six species was lower in high O3 concentrations at ambient CO2, significantly so in A. smithii and P. tremuloides. Five of the six species also exhibited reductions in in situ photosynthesis at ambient CO2 in high-O3-grown compared with low-O3-grown plants. For all species, these O3-induced reductions in RGR and photosynthesis were absent in the elevated CO2 environment. Root weight ratio was significantly reduced by elevated O3 in A. smithii and P. tremuloides in ambient but not elevated CO2. Species with high stomatal conductance were the most susceptible to oxidant injury, while those with low stomatal conductance, such as the C4 species and Q. rubra, were not as detrimentally affected by O3. Elevated levels of CO2 will reduce stomatal conductance and O3 uptake, and might therefore reduce the potential for oxidant damage. However, there was a stronger relationship of the percent reduction in whole-plant mass due to O3, related to the ratio of photosynthesis to stomatal conductance. In general, results of this study of six functionally diverse plant species suggest that O3 pollution effects on carbon balance and growth are likely to be ameliorated by elevated concentrations of atmospheric CO2.

Those “Gorgeous Incongruities”: Polite Politics and Public Space on the Streets of Nineteenth-Century New York City

Abstract: The streets of mid-nineteenth-century New York City were sites of complex social engagements and economic activity. The promenades along both Broadway and Fifth Avenue were highly scripted rituals, where social mores and upper-class values were enacted and embodied on a daily basis. Focusing on analyses of three images, I argue that these streets were also the sites of political activity, but a politics that I define as “micropolitics” of “tactical” transgressions made possible by the structure of these social rituals. By making such an argument, I show how the streets of nineteenth-century cities were neither completely democratic nor totally controlled public spaces. I also provide a broader alternative to thinking about politics, one that understands the complex and contextual nature of human agency, and suggest that our frameworks for thinking about contemporary public space may be blinding us to potential sites of transgression.

Physical Play and Cognitive Development: Integrating Activity, Cognition, and Education

Abstract: We propose that humans may have evolved a special sensitivity to certain types of social information during rough-and-tumble play that facilitates social cognition. The cognitive benefits of physical play are described as providing a break from demanding intellectual tasks, and are hypothesized to be related to gender differences in spatial cognition.