Showing papers by "Florida Atlantic University published in 1999"

Generality of leaf trait relationships: a test across six biomes

Abstract: Convergence in interspecific leaf trait relationships across diverse taxonomic groups and biomes would have important evolutionary and ecological implications. Such convergence has been hypothesized to result from trade-offs that limit the combination of plant traits for any species. Here we address this issue by testing for biome differences in the slope and intercept of interspecific relationships among leaf traits: longevity, net pho- tosynthetic capacity (Amax), leaf diffusive conductance (Gs), specific leaf area (SLA), and nitrogen (N) status, for more than 100 species in six distinct biomes of the Americas. The six biomes were: alpine tundra-subalpine forest ecotone, cold temperate forest-prairie ecotone, montane cool temperate forest, desert shrubland, subtropical forest, and tropical rain forest. Despite large differences in climate and evolutionary history, in all biomes mass-based leaf N (Nmass), SLA, Gs, and Amax were positively related to one another and decreased with increasing leaf life span. The relationships between pairs of leaf traits exhibited similar slopes among biomes, suggesting a predictable set of scaling relationships among key leaf morphological, chemical, and metabolic traits that are replicated globally among terrestrial ecosystems regardless of biome or vegetation type. However, the intercept (i.e., the overall elevation of regression lines) of relationships between pairs of leaf traits usually differed among biomes. With increasing aridity across sites, species had greater Amax for a given level of Gs and lower SLA for any given leaf life span. Using principal components analysis, most variation among species was explained by an axis related to mass-based leaf traits (Amax, N, and SLA) while a second axis reflected climate, Gs, and other area-based leaf traits.

On calculating connected dominating set for efficient routing in ad hoc wireless networks

Abstract: Efficient routing among a set of mobile hosts (also called nodes) is one of the most important functions in ad-hoc wireless networks. Routing based on a connected dominating set is a frequently used approach, where the searching space for a route is reduced to nodes in the set. A set is dominating if all the nodes in the system are either in the set or neighbors of nodes in the set. In this paper, we propose a simple and efficient distributed algorithm for calculating connected dominating set in ad-hoc wireless networks, where connections of nodes are determined by their geographical distances. Our simulation results show that the proposed approach outperforms a classical algorithm. Our approach can be potentially used in designing efficient routing algorithms based on a connected dominating set.

Extending the technology acceptance model to account for social influence: theoretical bases and empirical validation

Abstract: The Technology Acceptance Model (TAM) represents an important theoretical contribution toward understanding IS usage and IS acceptance behaviors. However, as noted by several IS researchers, TAM is incomplete in one important respect: it doesn't account for social influence in the adoption and utilization of new information systems. Davis (1986) and Davis et al. (1989) noted that it is important to account for subjective norm (SN), the construct denoting social influence. However, they observed that the conceptualization of SN based on TRA (Theory of Reasoned Action) has theoretical and psychometric problems. Specifically, they observed that it is difficult to distinguish if usage behavior is caused by the influence of referents on one's intent or by one's own attitude. They suggested that this problem may be circumvented by using an alternative theoretical basis for conceptualizing SN, specifically in terms of Kelman's (1958, 1961) processes of social influence (compliance, identification and internalization). Within the context of organizational enterprisewide implementation and adoption of collaboration and communication technologies, this study establishes theoretical and empirical bases for the above conceptualization originally suggested by Davis and his colleagues. The construct of social influence is operationalized in terms of Kelman's processes of internalization, identification and compliance. Analyses of field study data provide evidence of the reliability and validity of the proposed constructs, factor structures and measures. The findings enable future researchers to account for social influence in further investigating TAM.

Photovoltaic Systems Engineering

Abstract: Background.- The Sun.- Introduction to PV Systems.- PV System Examples.- Cost Considerations.- Mechanical Considerations.- Stand-Alone PV Systems.- Utility Interactive PV Systems.- Externalities and Photovoltaics.- The Physics of Photovoltaic Cells.- Present and Proposed PV Cells.

Projections of the median raphe nucleus in the rat.

Abstract: No previous report in any species has examined comprehensively the projections of the median raphe (MR) nucleus with modern tracing techniques. The present report represents an in depth analysis of the projections of MR by use of the anterograde anatomical tracer Phaseolus vulgaris-leucoagglutinin. MR fibers descend along the midline within the brainstem and mainly ascend within the medial forebrain bundle in the forebrain. MR fibers distribute densely to the following brainstem/forebrain sites: caudal raphe nuclei, laterodorsal tegmental nucleus, dorsal raphe nucleus, interpeduncular nucleus, medial mammillary body, supramammillary nucleus, posterior nucleus and perifornical region of the hypothalamus, midline and intralaminar nuclei of thalamus, dopamine-containing cell region of medial zona incerta, lateral habenula, horizontal and vertical limbs of the diagonal band nuclei, medial septum, and hippocampal formation. Virtually all of these structures lie on or close to the midline, indicating that the MR represents a midline/para-midline system of projections. Overall, MR projections to the cortex are light. MR projects moderately to the perirhinal, entorhinal and frontal cortices, but sparingly to remaining regions of cortex. A comparison of MR with dorsal raphe (DR) projections (Vertes RP. 1991. J Comp Neurol 313:643-668) shows that these two major serotonin-containing cell groups of the midbrain distribute to essentially nonoverlapping regions of the forebrain; that is, the MR and DR project to complementary sites in the forebrain. A direct role for the MR in the desynchronization of the electroencephalographic activity of the hippocampus and its possible consequences for memory-associated functions of the hippocampus is discussed.

Prenatal depression effects on neonates

Abstract: Sixty-three pregnant women (36 with depression symptoms) were recruited during their last trimester of pregnancy. The depressed mothers had higher cortisol and norepinephrine levels and lower dopamine levels. Their infants subsequently had higher cortisol and norepinephrine levels and lower dopamine levels at the neonatal stage. The neonates of depressed mothers also showed inferior performance on the orientation, reflex, excitability, and withdrawal clusters of the Brazelton Neonatal Behavioral Assessment. Stepwise regression analyses revealed that the depressed mothers' prenatal norepinephrine and dopamine levels significantly predicted the newborns' norepinephrine and dopamine levels and their Brazelton scores, highlighting an early biochemical influence on neonatal outcome.

Jealousy and the nature of beliefs about infidelity: Tests of competing hypotheses about sex differences in the United States, Korea, and Japan

Abstract: The different adaptive problems faced by men and women over evolutionary history led evolutionary psychologists to hypothesize and discover sex differences in jealousy as a function of infidelity type. An alternative hypothesis proposes that beliefs about the conditional probabilities of sexual and emotional infidelity account for these sex differences. Four studies tested these hypotheses. Study 1 tested the hypotheses in an American sample (N = 1,122) by rendering the types of infidelity mutually exclusive. Study 2 tested the hypotheses in an American sample (N = 234) by asking participants to identify which aspect of infidelity was more upsetting when both forms occurred, and by using regression to identify the unique contributions of sex and beliefs. Study 3 replicated Study 2 in a Korean sample (N = 190). Study 4 replicated Study 2 in a Japanese sample (N = 316). Across the studies, the evolutionary hypothesis, but not the belief hypothesis, accounted for sex differences in jealousy when the types of infidelity are rendered mutually exclusive; sex differences in which aspect of infidelity is more upsetting when both occur; significant variance attributable to sex, after controlling for beliefs; sex-differentiated patterns of beliefs; and the cross-cultural prevalence of all these sex differences.

The Impact of Trader Type on the Futures Volatility-Volume Relation

Abstract: We examine the volatility-volume relation in futures markets using volume data categorized by type of trader. We find that the positive volatility-volume relation is driven by the general public, a group of traders who are distant from the trading floor and therefore without precise information on order flow. Clearing members and floor traders who observe order flow often decrease volatility. Our findings are consistent with Shalen's (1993) hypothesis that uninformed traders who cannot differentiate liquidity demand from fundamental value change increase volatility. IN THEIR 1993 STUDY, Bessembinder and Seguin suggest that the volatilityvolume relation in financial markets may depend on the type of trader. We investigate whether specific types of futures market traders, which we distinguish by the information they possess, actually have different effects on the positive volatility-volume relation. We use the Liquidity Data Bank (LDB) to test this information effect. The LDB is a database that separates futures volume by four types of traders: market makers, clearing members (such as financial institutions) trading for their own accounts, floor traders trading for other exchange members, and the general public (individual speculators, managed funds, and small

NEUROPSI: a brief neuropsychological test battery in Spanish with norms by age and educational level.

Abstract: The purpose of this research was to develop, standardize, and test the reliability of a short neuropsychological test battery in the Spanish language. This neuropsychological battery was named “NEUROPSI,” and was developed to assess briefly a wide spectrum of cognitive functions, including orientation, attention, memory, language, visuoperceptual abilities, and executive functions. The NEUROPSI includes items that are relevant for Spanish-speaking communities. It can be applied to illiterates and low educational groups. Administration time is 25 to 30 min. Normative data were collected from 800 monolingual Spanish-speaking individuals, ages 16 to 85 years. Four age groups were used: (1) 16 to 30 years, (2) 31 to 50 years, (3) 51 to 65 years, and (4) 66 to 85 years. Data also are analyzed and presented within 4 different educational levels that were represented in this sample: (1) illiterates (zero years of school); (2) 1 to 4 years of school; (2) 5 to 9 years of school; and (3) 10 or more years of formal education. The effects of age and education, as well as the factor structure of the NEUROPSI are analyzed. The NEUROPSI may fulfill the need for brief, reliable, and objective evaluation of a broad range of cognitive functions in Spanish-speaking populations. ( JINS, 1999, 5, 413‐ 433.)

Notions of Input to Output Stability

Abstract: This paper deals with several related notions of output stability with respect to inputs. The inputs may be thought of as disturbances; when there are no inputs, one obtains generalizations of the classical concepts of partial stability. The main notion studied is called input to output stability (IOS), and it reduces to input to state stability (ISS) when the output equals the complete state. Several variants, which formalize in different manners the transient behavior, are introduced. The main results provide a comparison among these notions. A companion paper establishes necessary and sufficient Lyapunov-theoretic characterizations.

Prevalence of Attention-Deficit/Hyperactivity Disorder Symptoms in 4- to 17-Year-Old Children in the General Population

Abstract: The purposes of this study were (a) to estimate the prevalence of Attention-Deficit/Hyperactivity Disorder (AD/HD) symptoms in the general preschool and school population; and (b) to analyze the influence of gender, age, and socioeconomic status (SES) variables on AD/ HD symptoms. Out of the 80,000 preschool and schoolchildren living in Manizales, Colombia, a random sample of 540 children was selected. Two gender, three age (4- to 5-year olds, 6- to 11 -year olds, and 12- to 17-year olds), and three SES (low, middle, and high) groups were used. The 18 DSM-IV symptoms corresponding to AD/HD Criterion A were assessed on a scale of 0 (never) to 3 (almost always). All three demographic variables established statistically significant differences: AD/HD symptoms were more frequent in 6to 11-year-old, low-SES, male participants. DSM-IV Criterion A for AD/HD was fulfilled by 19.8% of the boys and 12.3% of the girls. However, this difference was marginally significant only in the AD/HD Subtype I: Combined. It was concluded that demographic variables are significant correlates of the AD/HD diagnosis. The prevalence found in this study was higher than usually reported, even though only the symptomatic DSM-IV AD/HD criterion was analyzed. We failed to confirm the assumed AD/HD gender ratio.

Lyapunov Characterizations of Input to Output Stability

Abstract: This paper presents necessary and sufficient characterizations of several notions of input to output stability. Similar Lyapunov characterizations have been found to play a key role in the analysis of the input to state stability property, and the results given here extend their validity to the case when the output, but not necessarily the entire internal state, is being regulated. The work is related to partial stability of differential equations (the particular case which arises when there are no external inputs).

Evaluating the Dimensionality and Invariance of ”Low Self-Control”

Abstract: According to Gottfredson and Hirschi's (1990) A General Theory ofCrime, all illegal activity is the manifestation of a single underlyingcause. The authors argue that inadequate child-rearing causes individualsto develop a similar type of propensity for criminal and analogousbehavior. Gottfredson and Hirschi label this characteristic“low self-control.” Six dimensions, which can be identified intheir theory, are suggested to comprise a final low self-controltrait. Further, low self-control is proposed to be an invariantcharacteristic (i.e., its form does not change with the age of theindividual or context in which the person resides). In this research, weevaluate these two propositions. First, the six dimensions are measured andused to determine if a multidimensional model can explain another commonfactor—low self-control—in two samples of individuals (fromdifferent locales) with dissimilar mean ages. Second, low self-control inboth samples is tested for invariance. We test the proposed invariance oflow self-control by examining if the parameter values in a model, which isreflective of Gottfredson and Hirschi's conceptualization of thecharacteristic, differ across the two samples of individuals. The resultssupport both of Gottfredson and Hirschi's propositions. Lowself-control does appear to be a multidimensional characteristic whosedimensions represent another common factor. Low self-control also appears tobe an invariant latent trait that members of these two samplespossess. These tests help to clarify Gottfredson and Hirschi'sconceptualization of low self-control.

Ethnic Entrepreneurial and Marketing Systems: Implications for the Global Economy:

Abstract: The role of immigrant ethnic entrepreneurs in the small business milieu of the developed world has been studied within sociology for the past three decades. This article attempts to generate intere...

Differences in Parental Investment Contribute to Important Differences Between Men and Women

Abstract: Parental investment theory addresses sex differences that result from the trade-off between parenting effort and mating effort. For example, relative to men, women spend more time caring for offspring, are more selective in assenting to sexual intercourse, are more upset by a partner's emotional infidelity than by a partner's sexual infidelity, and are better able to inhibit their behaviors in certain situations. These and other sex differences are attributable to evolved mechanisms that work in interaction with the physical and social environments.

Increasing Affective Organizational Commitment in Public Organizations: The Key Role of Interpersonal Trust

Abstract: Affective organizational commitment has been equated to the public service motivation of pubhc employees It is a valuable component of organizational effectiveness However, few management intervention strategies exist that specifically address increasing affective commitment Often successful interventions are designed around correlates of the intended attitudinal construct One hypothesized correlate of affective commitment m organization behavior hterature is trust Trust can be differentiated as interpersonal trust (between the employee and the manager) and systems trust (between the employee and the organization as a whole) This differentiation is significant for the public manager because the relationship between affective commitment and trust can prescnbe two different strategies for an intervention aimed at positively impacting affective commitment For example, if affective commitment is linked to systems trust, an intervention based on a top-down strategy would be the better choice This study tests t...

How Departments of Economics Evaluate Teaching

Abstract: Based on results from a 1999 national survey, William Becker and Michael Watts found that student evaluations of teaching were by far the most widely used, and often the only method used by economics departments, to evaluate teaching in undergraduate economics courses. To investigate whether departments of economics have moved beyond the use of student evaluations of teaching, in 2011 the current authors conducted a national survey of departments based largely on questions used in the 1999 survey. The surveys included items on how courses and teaching are evaluated, and on how that information is used in departmental promotion and salary decisions.

Logistic regression modeling of software quality

Abstract: Reliable software is mandatory for complex mission-critical systems. Classifying modules as fault-prone, or not, is a valuable technique for guiding development processes, so that resources can be focused on those parts of a system that are most likely to have faults. Logistic regression offers advantages over other classification modeling techniques, such as interpretable coefficients. There are few prior applications of logistic regression to software quality models in the literature, and none that we know of account for prior probabilities and costs of misclassification. A contribution of this paper is the application of prior probabilities and costs of misclassification to a logistic regression-based classification rule for a software quality model. This paper also contributes an integrated method for using logistic regression in software quality modeling, including examples of how to interpret coefficients, how to use prior probabilities, and how to use costs of misclassifications. A case study of a major subsystem of a military, real-time system illustrates the techniques.

Social sanction and threat explanations of gender effects on direct and indirect aggression

Abstract: The present study examined two explanations for gender differences in expression of direct and indirect aggression. The social sanction model suggests that aggressor and target gender effects may be accounted for in terms of social sanctions against behaving aggressively; indirect aggression is the likely outcome of inhibitions against expression of direct aggression. The threat argument suggests that high levels of direct aggression in male-male dyads as well as apparent inhibitions against harming females might be accounted for by the fact that males are more threatening targets than are females. Research participants completed a questionnaire measure of direct and indirect aggression twice, once with reference to their behavior toward a same-gender target and once with reference to their behavior toward an other-gender target. Although most direct aggression was reported by male aggressors toward male targets, gender of target did not relate to indirect aggression. Males reported approximately equal levels of indirect and direct aggression. Although females reported using more indirect than direct aggression, they did not differ from males in their reports of the frequency of use of indirect aggression. These results provided some support for both models of gender effects on human aggression and suggest the appropriateness of a relatively complex model of gender effects on aggression. Aggr. Behav. 25:425–434, 1999. © 1999 Wiley-Liss, Inc.

Persistence of self in advanced Alzheimer's disease.

Abstract: The theme of diminishing self is common in the popular and health care literature about the late stages of Alzheimer’s disease. In her narrative on the experience of having Alzheimer’s disease, Diana Friel McGowin wrote, there is “less and less of me every day” (1993, p. 33). Spouses say this is not the man or woman I married, or they describe the person as just a shell of what he or she once was (Jenkins & Price, 1996). Nursing home staff appear to believe the same thing, frequently avoiding all but task-oriented communication with people in the latest stages of the disease (Ekman, Norberg, Viitanen, & Winblad, 1991) on the assumption that the severely demented experience life as meaningless (Norberg & Asplund, 1990). Similar assumptions are found in the health care literature (Downs, 1997). A person’s attempts at speech in the later stages have been described as nonsensical and devoid of meaning or insight, contributing to the impression of a diminishing self (Bohling, 1991). Also noted is the lack of “reference to the speaker as ego” (Kertesz, 1994) leaving the same impression. The consciousness of the individual is described as gradually fading away (Lyman, 1989) or becoming “a continuously fading dream,” (Bayles, 1995, p. 362). The progressive decline associated with this disease is well known. Lyman (1989) used the term “self-deterioration” to characterize it and Cohen (1991) wrote of the death of the mind before physical death. Ronch (1996) adds, “The loss of self happens before the very eyes of the person whose self is vanishing.” (p. 25). In the last of the six phases of the subjective experience of Alzheimer’s disease proposed by Cohen, separation from self is said to occur. Humanness and a personal, subjective experience of the disease are maintained until this last stage in which the person is described as reacting only to sensory stimuli.

Some Reservations About Social Capital

Abstract: The article contains three commentaries on management research. Edwin A. Locke comments on Nahapiet and Ghoshal (1998), which suggests that organizational effectiveness is based on social capital and intellectual capital. Niels G. Noorderhaven refers to research on the influence of national culture on the development of trust. Joseph A. Cannon, Patricia M. Doney, and Michael R. Mullen respond to commentary concerning their article about national cultures, the development of trust, and the factors that affect attitudes. They also suggest three empirical methods for testing their concept.

Structure and Dynamics of Peptide−Amphiphiles Incorporating Triple-Helical Proteinlike Molecular Architecture†

Abstract: Organized polymeric assemblies that incorporate bioactive sequences and structures are finding important applications for the study of protein structure-function relationships. We have recently described a heteropolymeric peptide-amphiphile system that forms organized structures in solution and on surfaces. While the overall three-dimensional features of peptide-amphiphiles have been studied previously, the precise environment of specific residues, particularly those within biologically active regions, have not been examined in detail. In the present study, we have used heteronuclear single quantum coherence (HSQC) and inverse-detected 1H-15N NMR spectroscopy to examine the structure and dynamics of a peptide and peptide-amphiphile that incorporate the alpha1(IV)1263-1277 ([IV-H1]) amino acid sequence from type IV collagen. Three variants of the sequence (Gly-Pro-Hyp)4-[IV-H1]-(Gly-Pro-Hyp)4 were constructed with a single 15N-labeled Gly placed in the middle of the N-terminal (Gly-Pro-Hyp)4 region (residue Gly7), in the middle of the [IV-H1] sequence (residue Gly19), or in the middle of the C-terminal (Gly-Pro-Hyp)4 region (residue Gly34). These peptides were also N-terminally acylated with hexanoic acid to create an analogous series of 15N-labeled peptide-amphiphiles. HSQC spectra indicated that both the peptide and the peptide-amphiphile were in triple-helical conformation at low temperature, supporting prior circular dichroism (CD) spectroscopic results. The intensities of the triple-helical cross-peaks were stronger for the peptide-amphiphile, consistent with an enhanced triple-helical thermal stability within the peptide-amphiphile construct compared to that of the peptide alone. Relative relaxation values for the peptide-amphiphile monomeric and trimeric species were consistent with those reported previously for other triple-helical peptides. Relaxation measurements indicated that the triple-helical [IV-H1] region did not appear to be dramatically more flexible than the Gly-Pro-Hyp regions. The angle between Gly N-H bonds and the helix dyad axis, determined from the relaxation data, was within the range expected for triple helices. Overall, the peptide headgroup of the C6-(Gly-Pro-Hyp)4-[IV-H1]-(Gly-Pro-Hyp)4 peptide-amphiphile appears to form a continuous triple helix that behaves similarly, in a dynamic sense, to a triple-helical peptide. The enhanced thermal stability of the peptide-amphiphile compared to the analogous triple-helical peptide, along with the multitude of organized structures formed by lipidlike compounds, suggest that peptide-amphiphiles could be utilized as targeted liposomes, sensors, receptors, or enzymes.