Showing papers by "University of Central Florida published in 2001"

The Science of Training: A Decade of Progress

Abstract: ▪ Abstract This chapter reviews the training research literature reported over the past decade. We describe the progress in five areas of research including training theory, training needs analysis, antecedent training conditions, training methods and strategies, and posttraining conditions. Our review suggests that advancements have been made that help us understand better the design and delivery of training in organizations, with respect to theory development as well as the quality and quantity of empirical research. We have new tools for analyzing requisite knowledge and skills, and for evaluating training. We know more about factors that influence training effectiveness and transfer of training. Finally, we challenge researchers to find better ways to translate the results of training research into practice.

Mathematical model for the irradiance probability density function of a laser beam propagating through turbulent media

Abstract: We develop a model for the probability density function (pdf) of the irradiance fluctuations of an optical wave propagating through a turbulent medium. The model is a two-parameter distribution that is based on a doubly stochastic theory of scintillation that assumes that small-scale irradiance fluctuations are modulated by large-scale irradi- ance fluctuations of the propagating wave, both governed by indepen- dent gamma distributions. The resulting irradiance pdf takes the form of a generalized K distribution that we term the gamma-gamma distribution. The two parameters of the gamma-gamma pdf are determined using a recently published theory of scintillation, using only values of the refractive-index structure parameter C n (or Rytov variance) and inner scale l 0 provided with the simulation data. This enables us to directly calculate various log-irradiance moments that are necessary in the scaled plots. We make a number of comparisons with published plane wave and spherical wave simulation data over a wide range of turbu- lence conditions (weak to strong) that includes inner scale effects. The gamma-gamma pdf is found to generally provide a good fit to the simu- lation data in nearly all cases tested. © 2001 Society of Photo-Optical Instrumen-

Reflections on shared cognition

Abstract: The purpose of this paper is to highlight several fundamental questions that remain regarding shared cognition: (1) What must be ‘shared’? (2) What does ‘shared’ mean? (3) How should ‘shared’ be measured? and (4) What outcomes do we expect shared cognition to affect? A general and integrative description of these questions is provided. In addition, the value of shared cognition is discussed along with recommendations for future research. Copyright © 2001 John Wiley & Sons, Ltd.

Asian Dust Events of April 1998

Abstract: On April 15 and 19, 1998, two intense dust storms were generated over the Gobi desert by springtime low-pressure systems descending from the northwest. The windblown dust was detected and its evolution followed by its yellow color on SeaWiFS satellite images, routine surface-based monitoring, and through serendipitous observations. The April 15 dust cloud was recirculating, and it was removed by a precipitating weather system over east Asia. The April 19 dust cloud crossed the Pacific Ocean in 5 days, subsided to the surface along the mountain ranges between British Columbia and California, and impacted severely the optical and the concentration environments of the region. In east Asia the dust clouds increased the albedo over the cloudless ocean and land by up to 10–20%, but it reduced the near-UV cloud reflectance, causing a yellow coloration of all surfaces. The yellow colored backscattering by the dust eludes a plausible explanation using simple Mie theory with constant refractive index. Over the West Coast the dust layer has increased the spectrally uniform optical depth to about 0.4, reduced the direct solar radiation by 30–40%, doubled the diffuse radiation, and caused a whitish discoloration of the blue sky. On April 29 the average excess surface-level dust aerosol concentration over the valleys of the West Coast was about 20–50 μg/m3 with local peaks >100 μg/m3. The dust mass mean diameter was 2–3 μm, and the dust chemical fingerprints were evident throughout the West Coast and extended to Minnesota. The April 1998 dust event has impacted the surface aerosol concentration 2–4 times more than any other dust event since 1988. The dust events were observed and interpreted by an ad hoc international web-based virtual community. It would be useful to set up a community-supported web-based infrastructure to monitor the global aerosol pattern for such extreme aerosol events, to alert and to inform the interested communities, and to facilitate collaborative analysis for improved air quality and disaster management.

Taking stock of naturalistic decision making

Abstract: We review the progress of naturalistic decision making (NDM) in the decade since the first conference on the subject in 1989. After setting out a brief history of NDM we identify its essential characteristics and consider five of its main contributions: recognition-primed decisions, coping with uncertainty, team decision making, decision errors, and methodology. NDM helped identify important areas of inquiry previously neglected (e.g. the use of expertise in sizing up situations and generating options), it introduced new models, conceptualizations, and methods, and recruited applied investigators into the field. Above all, NDM contributed a new perspective on how decisions (broadly defined as committing oneself to a certain course of action) are made. NDM still faces significant challenges, including improvement of the quantity and rigor of its empirical research, and confirming the validity of its prescriptive models. Copyright © 2001 John Wiley & Sons, Ltd.

Leadership in complex organizations

Abstract: This paper asks how complexity theory informs the role of leadership in organizations. Complexity theory is a science of complexly interacting systems; it explores the nature of interaction and adaptation in such systems and how they influence such things as emergence, innovation, and fitness. We argue that complexity theory focuses leadership efforts on behaviors that enable organizational effectiveness, as opposed to determining or guiding effectiveness. Complexity science broadens conceptualizations of leadership from perspectives that are heavily invested in psychology and social psychology (e.g., human relations models) to include processes for managing dynamic systems and interconnectivity. We develop a definition of organizational complexity and apply it to leadership science, discuss strategies for enabling complexity and effectiveness, and delve into the relationship between complexity theory and other currently important leadership theories. The paper concludes with a discussion of possible implications for research strategies in the social sciences.

The influence of complementarity, compatibility, and relationship capital on alliance performance

Abstract: Value creation through alliances requires the simultaneous pursuit of partners with similar characteristics on certain dimensions and different characteristics on other dimensions. Partnering firms need to have different resource and capability profiles yet share similarities in their social institutions. In this article, the authors empirically examine the impact of partner characteristics on the performance of alliances. In particular, they test hypotheses related to both direct impact of partner characteristics on alliance performance and indirect effects through relational capital aspects of the alliance. Empirical results based on a sample of alliances in the global construction contracting industry suggest that complementarity in partner resources and compatibility in cultural and operational norms have different direct and indirect effects on alliance performance. Accordingly, organizational routines aimed at partner selection need to be complemented by relationship management routines to maximize the potential benefits from an alliance.

Moderators of stress in parents of children with autism.

Abstract: Parents of children with autism experience more stress and are more susceptible to negative outcomes than parents of children with other disabilities. The present work examines the relationship between stressors, social support, locus of control, coping styles, and negative outcomes (depression, social isolation, and spousal relationship problems) among parents of children with autism. Fifty-eight parents completed surveys. Results indicated that several coping styles corresponded to negative outcomes. Furthermore, the relationship between stressors and negative outcomes was moderated by social support and coping style. Results are discussed in relation to applications for clinical practice.

Overexpression of the Bt cry2Aa2 operon in chloroplasts leads to formation of insecticidal crystals

Abstract: In nuclear transgenic plants, expression of multiple genes requires introduction of individual genes and time-consuming subsequent backcrosses to reconstitute multi-subunit proteins or pathways, a problem that is compounded by variable expression levels. In order to accomplish expression of multiple genes in a single transformation event, we have introduced several genes into the chromoplast genome. We confirmed stable integration of the cry2Aa2 operon by PCR and Southern blot analyses in T0 and T1 transgenic plants. Foreign protein accumulated at 45.3% of the total soluble protein in mature leaves and remained stable even in old bleached leaves (46.1%), thereby increasing the efficacy and safety of transgenic plants throughout the growing season. This represents the highest level of foreign gene expression reported in transgenic plants to date. Insects that are normally difficult to control (10-day old cotton bollworm, beet armyworm) were killed 100% after consuming transgenic leaves. Electron micrographs showed the presence of the insecticidal protein folded into cuboidal crystals. Formation of crystals of foreign proteins (due to hyperexpression and folding by the putative chaperonin, ORF 2) provides a simple method of purification by centrifugation and enhances stability by protection from cellular proteases. Demonstration of expression of an operon in transgenic plants paves the way to engineering new pathways in plants in a single transformation event.

Does Entry Size Matter? The Impact of the Life Cycle and Technology on Firm Survival

Abstract: A wave of empirical studies has recently emerged showing that smaller-scale entry is confronted with a lower likelihood of survival than their larger counterparts. The purpose of this paper is to examine whether the relationship between size of a firm when entering an industry and the likelihood of survival holds under different technological conditions and across the different stages of the industry life cycle. The empirical evidence suggests that the relationship between firm size and the likelihood of survival is shaped by technology and the stage of the industry life cycle. While the likelihood of survival confronting small entrants is generally less than that confronting their larger counterparts, the relationship does not hold for mature stages of the product life cycle, or in technologically intensive products. In mature industries that are still technologically intensive, entry may be less about radical innovation and possibly more about filling strategic niches, thus negating the impact of entry size on the likelihood of survival.

Break Point Estimation and Spurious Rejections With Endogenous Unit Root Tests

Abstract: This paper examines the accuracy of break point estimation using the endogenous break unit root tests of Zivot and Andrews (1992) and Perron (1997). We find that these tests tend to identify the break point incorrectly at one‐period behind (TB‐1) the true break point (TB), where bias in estimating the persistence parameter and spurious rejections are the greatest. In addition, this outcome occurs under the null and alternative hypotheses, and more so as the magnitude of the break increases. Consequences of utilizing these endogenous break tests are similar to (incorrectly) omitting the break term Bt in Perron's (1989) exogenous test.

Team Training in the Skies: Does Crew Resource Management (CRM) Training Work?:

Abstract: The aviation community has invested great amounts of money and effort into crew resource management (CRM) training. Using D. L. Kirkpatrick's (1976) framework for evaluating training, we reviewed 58 published accounts of CRM training to determine its effectiveness within aviation. Results indicated that CRM training generally produced positive reactions, enhanced learning, and promoted desired behavioral changes. However, we cannot ascertain whether CRM has an effect on an organization's bottom line (i.e., safety). We discuss the state of the literature with regard to evaluation of CRM training programs and, as a result, call for the need to conduct systematic, multilevel evaluation efforts that will show the true effectiveness of CRM training. As many evaluations do not collect data across levels (as suggested by D. L. Kirkpatrick, 1976, and by G. M. Alliger, S. I. Tannenbaum, W. Bennett, Jr., & H. Traver, 1997), the impact of CRM cannot be truly determined; thus more and better evaluations are needed and should be demanded.

Expression of an Antimicrobial Peptide via the Chloroplast Genome to Control Phytopathogenic Bacteria and Fungi

Abstract: The antimicrobial peptide MSI-99, an analog of magainin 2, was expressed via the chloroplast genome to obtain high levels of expression in transgenic tobacco (Nicotiana tabacum var. Petit Havana) plants. Polymerase chain reaction products and Southern blots confirmed integration of MSI-99 into the chloroplast genome and achievement of homoplasmy, whereas northern blots confirmed transcription. Contrary to previous predictions, accumulation of MSI-99 in transgenic chloroplasts did not affect normal growth and development of the transgenic plants. This may be due to differences in the lipid composition of plastid membranes compared with the membranes of susceptible target microbes. In vitro assays with protein extracts from T1 and T2 plants confirmed that MSI-99 was expressed at high levels to provide 88% (T1) and 96% (T2) inhibition of growth against Pseudomonas syringae pv tabaci, a major plant pathogen. When germinated in the absence of spectinomycin selection, leaf extracts from T2 generation plants showed 96% inhibition of growth against P. syringae pv tabaci. In addition, leaf extracts from transgenic plants (T1) inhibited the growth of pregerminated spores of three fungal species, Aspergillus flavus, Fusarium moniliforme, and Verticillium dahliae, by more than 95% compared with non-transformed control plant extracts. In planta assays with the bacterial pathogen P. syringae pv tabaci resulted in areas of necrosis around the point of inoculation in control leaves, whereas transformed leaves showed no signs of necrosis, demonstrating high-dose release of the peptide at the site of infection by chloroplast lysis. In planta assays with the fungal pathogen, Colletotrichum destructivum, showed necrotic anthracnose lesions in non-transformed control leaves, whereas transformed leaves showed no lesions. Genetically engineering crop plants for disease resistance via the chloroplast genome instead of the nuclear genome is desirable to achieve high levels of expression and to prevent pollen-mediated escape of transgenes.

Development of artificial neural network models to predict driver injury severity in traffic accidents at signalized intersections

Abstract: The relationship between driver injury severity and driver, vehicle, roadway, and environment characteristics was examined. The use of two well-known neural network paradigms, the multilayer perceptron (MLP) and fuzzy adaptive resonance theory (ART) neural networks, was investigated. The use of artificial neural networks can lead to greater understanding of the relationship between the aforementioned factors and driver injury severity. Accident data for 1997 for the Central Florida area, which consists of Orange, Osceola, and Seminole Counties, were used. The analysis focuses on two-vehicle accidents that occurred at signalized intersections. The MLP neural network has a better generalization performance of 65.6 and 60.4 percent for the training and testing phases, respectively. The performance of the MLP was compared with that of an ordered logit model. The ordered logit model was able to correctly classify only 58.9 and 57.1 percent for the training and testing phases, respectively. A simulation experim...

A random nth-price auction

Abstract: Second-price auctions are designed to induce people to reveal their private preferences for a good. Laboratory evidence suggests that while these auctions do a reasonable job on aggregate, they fall short at the individual level, especially for bidders who are off-margin of the market-clearing price. Herein we introduce and explore whether a random nth-price auction can engage all bidders to bid sincerely. Our results first show that the random nth-price auction can induce sincere bidding in theory and practice. We then compare the random nth-price to the second-price auction. We find that the second-price auction works better on-margin, and the random nth-price auction works better off-margin. © 2001 Elsevier Science B.V. All rights reserved.

Infant feeding and weaning practices in Roman Egypt.

Abstract: Current knowledge of infant feeding and weaning practices during the Roman period in Egypt is limited to scanty documentary and iconographic evidence. Stable nitrogen and carbon isotope analysis provides another avenue to explore this question. A sample of 49 infant and juvenile human skeletal remains from the Kellis 2 cemetery in the Dakhleh Oasis, Egypt, was used to determine patterns of infant feeding and weaning. delta(15)N values indicate that supplementary foods were introduced at around 6 months of age, and that weaning was complete by 3 years of age. By 6 months of age, delta(13)C values become increasingly enriched over adult values, and reach peak enrichment at approximately 1.5 years of age. Beyond this age, delta(13)C gradually declines to approach adult values. This enrichment in infant delta(13)C values is indicative of consumption of (13)C-enriched supplementary foods. Based on isotopic study of faunal and botanical remains from the ancient village of Kellis, we conclude that at approximately 6 months of age, infants were fed milk of goat and/or cow.

Fast impulsive noise removal

Abstract: A generic n-dimensional filter with the primary purpose of eliminating impulsive-like noise is presented. This recursive nonlinear filter is composed of two conditional rules, which are applied independently, in any order, one after the other. It identifies noisy items by inspection of their surrounding neighborhood, and afterwards it replaces their values with the most "conservative" ones out of their neighbors' values. In this way, no new values are introduced and the histogram distribution range is conserved. This n-dimensional filter can be decomposed recursively to a lower dimensional space, each time generating two sets of n(n-1)-dimensional filters. This study, which focuses on the case of two-dimensional signals (gray scale images), explores one possible implementation of this new filter and orients the evaluation of its performance toward the median filter, as this filter is the basis of many more sophisticated filters for impulsive noise reduction. Tests were carried out using both real and artificial images. We found this new filter to be much faster than the median filter while performing comparably in terms of both image information conservation and noise reduction, which suggests that it could replace the median filter for the preliminary processing included in state-of-the-art noise removal filters. This new filter should either eliminate or attenuate most noisy pixels in synthetic and natural images not excessively contaminated. It has a slight smoothing effect on nonnoisy image regions. In addition, it is scalable, easily implemented, and adaptable to specific applications.

Focused ion beam milling: A method of site-specific sample extraction for microanalysis of Earth and planetary materials

Abstract: Argon ion milling is the conventional means by which mineral sections are thinned to electron transparency for transmission electron microscope (TEM) analysis, but this technique exhibits significant shortcomings. In particular, selective thinning and imaging of submicrometer inclusions during sample milling are highly problematic. We have achieved successful results using the focused ion beam (FIB) lift-out technique, which utilizes a 30 kV Ga + ion beam to extract electron transparent specimens with nanometer scale precision. Using this procedure, we have prepared a number of Earth materials representing a range of structures and compositions for TEM analysis. We believe that FIB milling will create major new opportunities in the field of Earth and planetary materials microanalysis, particularly with respect to ultraprecious mineral and rock samples.

Mycobacterium avium subsp. paratuberculosis as one cause of Crohn’s disease

Abstract: A number of theories regarding the aetiology of Crohn’s disease have been proposed. Diet, infections, other unidentified environmental factors and immune disregulation, all working under the influence of a genetic predisposition, have been viewed with suspicion. Many now believe that Crohn’s disease is a syndrome caused by several aetiologies. The two leading theories are the infectious and autoimmune theories. The leading infectious candidate is Mycobacterium avium subspecies paratuberculosis (Mycobacterium paratuberculosis), the causative agent of Johne’s disease, an inflammatory bowel disease in a variety of mammals including cattle, sheep, deer, bison, monkeys and chimpanzees. The evidence to support M. paratuberculosis infection as a cause of Crohn’s disease is mounting rapidly. Technical advances have allowed the identification and/or isolation of M. paratuberculosis from a significantly higher proportion of Crohn’s disease tissues than from controls. These methodologies include: (i) improved culture techniques; (ii) development of M. paratuberculosis-specific polymerase chain reaction assays; (iii) development of a novel in situ hybridization method; (iv) efficacy of macrolide and anti-mycobacterial drug therapies; and (v) discovery of Crohn’s disease-specific seroreactivity against two specific M. paratuberculosis recombinant antigens. The causal role for M. paratuberculosis in Crohn’s disease and correlation of infection with specific stratification(s) of the disorder need to be investigated. The data implicating Crohn’s as an autoimmune disorder may be viewed in a manner that supports the mycobacterial theory. The mycobacterial theory and the autoimmune theory are complementary; the first deals with the aetiology of the disorder, the second deals with its pathogenesis. Combined therapies directed against a mycobacterial aetiology and inflammation may be the optimal treatment of the disease.

A conceptual model of child psychopathology: implications for understanding attention deficit hyperactivity disorder and treatment efficacy.

Abstract: Highlights the desirability of using a theoretical framework for guiding the design and evaluation of therapeutic interventions for children with attention deficit hyperactivity disorder (ADHD). A general conceptual model is introduced and used to evaluate ADHD treatment outcome research. Treatments designed to target the substrate level (pharmacological interventions) result in broad, robust improvement in both core and peripheral areas of functioning. Those targeting hypothesized core features of the disorder (i.e., attention, impulsivity-hyperactivity) produce corresponding improvement in core and peripheral outcome measures with the exception of studies employing cognitive-behavior therapy. Those targeting peripheral features of the disorder effect change only in corresponding peripheral areas of functioning. Implications for clinical practice are discussed, and an alternative conceptual model of ADHD is introduced and compared with existing models.

Ancient drainage basin of the Tharsis region, Mars: Potential source for outflow channel systems and putative oceans or paleolakes

Abstract: Paleotopographic reconstructions based on a synthesis of published geologic information and high-resolution topography, including topographic profiles, reveal the potential existence of an enormous drainage basin/aquifer system in the eastern part of the Tharsis region during the Noachian Period. Large topographic highs formed the margin of the gigantic drainage basin. Subsequently, lavas, sediments, and volatiles partly infilled the basin, resulting in an enormous and productive regional aquifer. The stacked sequences of water-bearing strata were then deformed locally and, in places, exposed by magmatic-driven uplifts, tectonic deformation, and erosion. This basin model provides a potential source of water necessary to carve the large outflow channel systems of the Tharsis and surrounding regions and to contribute to the formation of putative northern-plains ocean(s) and/or paleolakes.

Object based segmentation of video using color, motion and spatial information

Abstract: Video segmentation is different from segmentation of a single image. While several correct solutions may exist for segmenting a single image, there needs to be a consistency among segmentations of each frame for video segmentation. Previous approaches of video segmentation concentrate on motion, or combine motion and color information in a batch fashion. We propose a maximum a posteriori probability (MAP) framework that uses multiple cues, like spatial location, color and motion, for segmentation. We assign weights to color and motion terms, which are adjusted at every pixel, based on a confidence measure of each feature. We also discuss the appropriate modeling of PDFs of each feature of a region. The correct modeling of the spatial PDF imposes temporal consistency among segments in consecutive frames. This approach unifies the strengths of both color segmentation and motion segmentation in one framework, and shows good results on videos that are not suited for either of these approaches.