Showing papers by "University of North Carolina at Charlotte published in 2002"

Ecosystem Decay of Amazonian Forest Fragments: a 22-Year Investigation

Abstract: We synthesized key findings from the Biological Dynamics of Forest Fragments Project, the world's largest and longest-running experimental study of habitat fragmentation. Although initially designed to assess the influence of fragment area on Amazonian biotas, the project has yielded insights that go far beyond the orig- inal scope of the study. Results suggest that edge effects play a key role in fragment dynamics, that the matrix has a major influence on fragment connectivity and functioning, and that many Amazonian species avoid even small ( � 100-m-wide) clearings. The effects of fragmentation are highly eclectic, altering species richness and abundances, species invasions, forest dynamics, the trophic structure of communities, and a variety of ecological and ecosystem processes. Moreover, forest fragmentation appears to interact synergistically with ecological changes such as hunting, fires, and logging, collectively posing an even greater threat to the rainforest biota. Descomposicion del Ecosistema en Fragmentos de Bosque Amazonico, Una Investigacion de 22 Anos Resumen: Sintetizamos resultados clave del proyecto sobre Dinamicas Biologicas de Fragmentos de bosque, el estudio experimental sobre fragmentacion del habitat mas largo y de mayor trayectoria del mundo. A pesar de que inicialmente el proyecto se diseno para evaluar la influencia del area de fragmentos en biotas del Amazo- nas, ha proporcionado un entendimiento que va mas alla del proposito original del estudio. Los resultados sugieren que los efectos de borde juegan un papel clave en las dinamicas de los fragmentos, que la matriz tiene una influencia mayor sobre la conectividad y el funcionamiento del fragmento y que muchas de las especies del Amazonas evitan areas taladas pequenas (de hasta � 100 m de ancho). Los efectos de la fragmentacion son al- tamente eclecticos, alterando la riqueza y abundancia de especies, las invasiones de especies, las dinamicas del bosque, la estructura trofica comunitaria y una variedad de procesos ecologicos y del ecosistema. Mas aun, la fragmentacion del bosque aparentemente interactua sinergisticamente con cambios ecologicos como lo son la caza, los incendios y la tala, representando colectivamente una gran amenaza sobre la biota del bosque lluvioso.

Intimate partner violence and physical health consequences

Abstract: Background: Domestic violence results in long-term and immediate health problems. This study compared selected physical health problems of abused and never abused women with similar access to health care. Methods: A case-control study of enrollees in a multisite metropolitan health maintenance organization sampled 2535 women enrollees aged 21 to 55 years who responded to an invitation to participate; 447 (18%) could not be contacted, 7 (0.3%) were ineligible, and 76 (3%) refused, yielding a sample of 2005. The Abuse Assessment Screen identified women physically and/or sexually abused between January 1, 1989, and December 31, 1997, resulting in 201 cases. The 240 controls were a random sample of never abused women. The general health perceptions subscale of the Medical Outcomes Study 36Item Short-Form Health Survey measured general health. The Miller Abuse Physical Symptom and Injury Scale measured abuse-specific health problems. tal status, educational level, and income. Direct weights were used to standardize for comparisons. Significance was tested using logistic and negative binomial regressions. Abused women had more (P.05) headaches, back pain, sexually transmitted diseases, vaginal bleeding, vaginal infections, pelvic pain, painful intercourse, urinary tract infections, appetite loss, abdominal pain, and digestive problems. Abused women also had more (P.001) gynecological, chronic stress–related, central nervous system, and total health problems. Conclusions: Abused women have a 50% to 70% increase in gynecological, central nervous system, and stressrelated problems, with women sexually and physically abused most likely to report problems. Routine universal screening and sensitive in-depth assessment of women presenting with frequent gynecological, chronic stress– related, or central nervous system complaints are needed to support disclosure of domestic violence. Arch Intern Med. 2002;162:1157-1163

Handbook of Data Mining and Knowledge Discovery

Abstract: Part A: Data mining and knowledge discovery Part B: Fundamental Concepts Part C: The process of knowledge discovery in databases Part D: Discovery Systems Part E: Interdisciplinary links of KDD Part F: Business problems Part G: Industry sectors Part H: KDD in practice: case studies

Hyporesponsiveness to vaccination with Borrelia burgdorferi OspA in humans and in TLR1- and TLR2-deficient mice

Abstract: The Lyme disease vaccine is based on the outer-surface lipoprotein (OspA) of the pathogen Borrelia burgdorferi, and 95% of vaccine recipients develop substantial titers of antibodies against OspA. Here, we identified seven individuals with very low antibody titers after vaccination (low responders). The macrophages of low responders produced less tumor necrosis factor-alpha and interleukin-6 after OspA stimulation and had lower cell-surface expression of Toll-like receptor (TLR) 1 as compared to normal cells, but normal expression of TLR2. TLRs activate innate responses to pathogens, and TLR2 recognizes lipoproteins and peptidoglycan (PGN). After OspA immunization, mice genetically deficient in either TLR2 (TLR2(-/-)) or TLR1 (TLR1(-/-)) produced low titers of antibodies against OspA. Notably, macrophages from TLR2(-/-) mice were unresponsive to OspA and PGN, whereas those from TLR1(-/-) mice responded normally to PGN but not to OspA. These data indicate that TLR1 and TLR2 are required for lipoprotein recognition and that defects in the TLR1/2 signaling pathway may account for human hyporesponsiveness to OspA vaccination.

A directionality based location discovery scheme for wireless sensor networks

Abstract: A sensor network is a large ad hoc network of densely distributed sensors that are equipped with low power wireless transceivers. Such networks can be applied for cooperative signal detection, monitoring, and tracking, and are especially useful for applications in remote or hazardous locations. This paper addresses the problem of location discovery at the sensor nodes, which is one of the central design challenges in sensor networks. We present a new method by which a sensor node can determine its location by listening to wireless transmissions from three or more fixed beacon nodes. The proposed method is based on an angle-of-arrival estimation technique that does not increase the complexity or cost of construction of the sensor nodes. We present the performance of the proposed method obtained from computer simulations.

Recent advances in separation of roughness, waviness and form

Abstract: Engineering surfaces are comprised of a range of spatial wavelengths. Filtering techniques are commonly adopted to separate the different wavelength components into well-defined bandwidths. Filtering is done prior to numerical characterization and it is also essential for extracting information needed to provide process feedback and establish functional correlation. This paper reviews commonly used filters in surface metrology like the 2RC, Gaussian and several new ones currently under research such as the spline, morphological, wavelets, regression filters and robust regression filters. The need for these new filters and examples illustrating the features of these filters are also presented.

Bit-error rate for free-space adaptive optics laser communications.

Abstract: An analysis of adaptive optics compensation for atmospheric-turbulence-induced scintillation is presented with the figure of merit being the laser communications bit-error rate. The formulation covers weak, moderate, and strong turbulence; on-off keying; and amplitude-shift keying, over horizontal propagation paths or on a ground-to-space uplink or downlink. The theory shows that under some circumstances the bit-error rate can be improved by a few orders of magnitude with the addition of adaptive optics to compensate for the scintillation. Low-order compensation (less than 40 Zernike modes) appears to be feasible as well as beneficial for reducing the bit-error rate and increasing the throughput of the communication link.

Does colorspace transformation make any difference on skin detection

Abstract: Skin detection is an important process in many of computer vision algorithms. It usually is a process that starts at a pixel-level, and that involves a pre-process of colorspace transformation followed by a classification process. A colorspace transformation is assumed to increase separability between skin and non-skin classes, to increase similarity among different skin tones, and to bring a robust performance under varying illumination conditions, without any sound reasonings. In this work, we examine if the colorspace transformation does bring those benefits by measuring four separability measurements on a large dataset of 805 images with different skin tones and illumination. Surprising results indicate that most of the colorspace transformations do not bring the benefits which have been assumed.

Induction of NFATc2 Expression by Interleukin 6 Promotes T Helper Type 2 Differentiation

Abstract: Interleukin (IL)-6 is produced by professional antigen-presenting cells (APCs) such as B cells, macrophages, and dendritic cells. It has been previously shown that APC-derived IL-6 promotes the differentiation of naive CD4+ T cells into effector T helper type 2 (Th2) cells. Here, we have studied the molecular mechanism for IL-6–mediated Th2 differentiation. During the activation of CD4+ T cells, IL-6 induces the production of IL-4, which promotes the differentiation of these cells into effector Th2 cells. Regulation of IL-4 gene expression by IL-6 is mediated by nuclear factor of activated T cells (NFAT), as inhibition of NFAT prevents IL-6–driven IL-4 production and Th2 differentiation. IL-6 upregulates NFAT transcriptional activity by increasing the levels of NFATc2. The ability of IL-6 to promote Th2 differentiation is impaired in CD4+ T cells that lack NFATc2, demonstrating that NFATc2 is required for regulation of IL-4 gene expression by IL-6. Regulation of NFATc2 expression and NFAT transcriptional activity represents a novel pathway by which IL-6 can modulate gene expression.

Regression quantiles for time series

Abstract: In this paper we study nonparametric estimation of regression quantiles for time series data by inverting a weighted Nadaraya–Watson (WNW) estimator of conditional distribution function, which was first used by Hall, Wolff, and Yao (1999, Journal of the American Statistical Association 94, 154–163). First, under some regularity conditions, we establish the asymptotic normality and weak consistency of the WNW conditional distribution estimator for α-mixing time series at both boundary and interior points, and we show that the WNW conditional distribution estimator not only preserves the bias, variance, and, more important, automatic good boundary behavior properties of local linear “double-kernel” estimators introduced by Yu and Jones (1998, Journal of the American Statistical Association 93, 228–237), but also has the additional advantage of always being a distribution itself. Second, it is shown that under some regularity conditions, the WNW conditional quantile estimator is weakly consistent and normally distributed and that it inherits all good properties from the WNW conditional distribution estimator. A small simulation study is carried out to illustrate the performance of the estimates, and a real example is also used to demonstrate the methodology.

Formal Proofs for the Security of Signcryption

Abstract: Signcryption is a public key or asymmetric cryptographic method that provides simultaneously both message confidentiality and unforgeability at a lower computational and communication overhead. In this paper, we propose a sound security model for signcryption that admits rigorous formal proofs for the confidentiality and unforgeablity of signcryption. A conclusion that comes out naturally from this work is that, as an asymmetric encryption scheme, signcryption is secure against adaptive chosen ciphertext attack in the random oracle model relative to, quite interestingly, the Gap Diffie-Hellman problem, and as a digital signature scheme, signcryption is existentially unforgeable against adaptive chosen message attack in the random oracle model relative to the discrete logarithm problem.

The predictive value of transcutaneous oxygen tension measurement in diabetic lower extremity ulcers treated with hyperbaric oxygen therapy: a retrospective analysis of 1144 patients

Abstract: The objective of this retrospective analysis was to determine the reliability of transcutaneous oxygen tension measurement (TcPO2) in predicting outcomes of diabetics who underwent hyperbaric oxygen therapy for lower extremity wounds. Six hyperbaric facilities provided TcPO2 data under several possible conditions: breathing air, breathing oxygen at sea level, and breathing oxygen in the chamber. Overall, 75.6% of the patients improved after hyperbaric oxygen therapy. Baseline sea-level air TcPO2 identified the degree of tissue hypoxia but had little statistical relationship with outcome prediction because some patients healed after hyperbaric oxygen therapy despite very low prehyperbaric TcPO2 values. Breathing oxygen at sea level was unreliable for predicting failure, but 68% reliable for predicting success after hyperbaric oxygen therapy. TcPO2 measured in chamber provides the best single discriminator between success and failure of hyperbaric oxygen therapy using a cutoff score of 200 mmHg. The reliability of in-chamber TcPO2 as an isolated measure was 74% with a positive predictive value of 58%. Better results can be obtained by combining information about sea-level air and in-chamber oxygen. A sea-level air TcPO2 < 15 mmHg combined with an in-chamber TcPO2 < 400 mmHg predicts failure of hyperbaric oxygen therapy with a reliability of 75.8% and a positive predictive value of 73.3%.

Sense of virtual community - maintaining the experience of belonging

Abstract: E-commerce strategists advise companies to create virtual communities for their customers, but what is involved in establishing and maintaining virtual communities? This paper addresses two questions: does a sense of community similar to that sometimes observed in physical communities also occur in virtual settings, and how is a sense of virtual community maintained? These questions are examined in an intensive study of an established virtual community called MSN (Microsoft Network). MSN members experienced a sense of community, but the dimensions of the sense of community differed somewhat from those reported for physical communities in ways plausibly related to the differences between electronic and face-to-face communication. The experienced sense of community in MSN was actively maintained through the social processes of exchanging support, creating identities and making identifications, and the production of trust. Again, these processes are similar to those in non-virtual communities, but related to the challenges of electronic communication. The findings suggest a process model of sense of virtual community creation and maintenance that is simpler and more powerful than previous theories.

Dimensions of work satisfaction as predictors of commitment type

Abstract: This study of hospital nurses (n = 154) examined the influence of dimensions of work satisfaction on types of organizational commitment. Significant results were found for the two affective commitment types tested but not for the instrumental type evaluated. The results indicate that satisfaction with professional status was a significant predictor of moral commitment. Dissatisfaction with organizational policies, autonomy, and professional status were significant predictors of alienative commitment. None of the dimensions of work satisfaction were predictors of calculative commitment. The results of this study suggest that understanding how various factors impact the nature and the form of an individual’s organizational commitment is worth the effort. If managers do not know what causes an attitude to take on a particular form, they cannot accurately predict what behavior might follow.

A Structural and Discriminant Analysis of the Work Addiction Risk Test

Abstract: The Work Addiction Risk Test (WART) was designed to measure “workaholism.” The present study examines the underlying dimensions of the WART and investigated the accuracy of the WART scores to discr...

A role-based delegation framework for healthcare information systems

Abstract: As organizations implement information strategies that call for sharing access to resources in the networked environment, mechanisms must be provided to protect the resources from adversaries. The proposed delegation framework addresses the issue of how to advocate selective information sharing in role-based systems while minimizing the risks of unauthorized access. We introduce a systematic approach to specify delegation and revocation policies using a set of rules. We demonstrate the feasibility of our framework through policy specification, enforcement, and a proof-of-concept implementation on specific domains, e.g. the healthcare environment. We believe that our work can be applied to organizations that rely heavily on collaborative tasks.

Learning style and training delivery mode preference

Abstract: An exploratory study investigated the relationship between learning style and preference for training delivery mode. It was expected that learning style would influence learners’ preference for receiving training through classroom‐, computer‐, TV‐, print‐, or audio‐based delivery modes. A total of 165 employees from a large US financial institution completed the Kolb Learning Style Instrument and a survey measuring training delivery mode preference. Results found support for the expected relationship between the two, with convergers showing a stronger preference for computer‐based delivery and assimilators showing a stronger preference for print‐based delivery. However, results also revealed an overall preference for classroom‐based delivery for adults in the study, regardless of their learning style. Implications of these results for training design and delivery are discussed.

Obstacles to Palliation and End-of-Life Care in a Long-Term Care Facility

Abstract: Purpose: This exploratory study used a set of four obstacle constructs derived from both the existing literature and our earlier work to describe the diverse end-of-life scenarios observed for a group of residents in a long-term care facility. Design and Methods: Data from a retrospective chart review and both quantitative and qualitative methods of data collection and analysis were used to examine in-depth the end-of-life experiences of all nursing home residents ( N 5 41) who died on the nursing care unit of a large continuing care retirement community during an 18month period. Results: A hierarchy of obstacles to palliation and end-of-life care seems to exist in long-term care settings that begins with the lack of recognition that restorative, rehabilitative, or curative treatment futility has commenced. The next three obstacles in sequence include lack of communication among decision makers, no agreement on a course of care, and failure to implement a timely plan of care. Implications: The findings highlight the importance of determining treatment futility as an initial step in the successful delivery of palliative and end-oflife care to residents in long-term care followed by the need for a deliberate and proactive series of actions and care planning processes.

Analysis of quantitative trait locus effects on the size and shape of mandibular molars in mice.

Abstract: While >50 genes have been found to influence the development of teeth in mice, we still know very little about the genetic basis for the adaptive characteristics of teeth, such as size and shape. We applied interval mapping procedures to Procrustes size and shape data obtained from 10 morphological landmarks on the mandibular molar row of the F(2) progeny from a cross between the LG/J and SM/J strains of mice. This revealed many more QTL for molar shape (18) than for molar centroid size (3), although levels of dominance effects were comparable among QTL for size and shape. Comparisons of patterns of Procrustes additive and dominance shape effects and ordination of QTL effects by principal components analysis suggested that the effects of the shape QTL were dispersed among the three molars and thus that none of these molars represents a genetically distinct developmental structure. The results of an analysis of co-occurrence of QTL for molar shape, mandible shape, and cranial dimensions in these mice suggested that many of the QTL for molar shape may be the same as those affecting these other sets of characters, although in some cases this could be due to effects of closely linked genes.

Interplay of order and disorder in the optical properties of opal photonic crystals

Abstract: It is shown that the polycrystalline structure of self-assembled synthetic opals leads to an interplay of properties determined by order and disorder in the vicinity of the optical stop band. We analyze the balance of photon fluxes by studying angle-resolved spectra of diffracted and scattered light for all directions in space. It is shown that the shape of the stop band features in different types of optical spectra ~diffraction, transmission, and scattering! is interlinked and must be studied jointly to understand optical phenomena in these materials. The principal effects are ~i! angular dispersion of the photonic stop bands in diffraction spectra, ~ii! inhomogeneous broadening of the stop band in zero-order transmission, and ~iii! appearance of very strong peaks in the spectra of scattered light, with resonant enhancements observed with intensity up to ;10 times greater than background scattering levels. It is shown that the resonant enhancements arise from multiple incoherent backward/forward reflections between the microcrystallites. It is shown that the spatial pattern and spectral form of the scattering spectra can be deduced from the analysis of angle-resolved zero-order transmission spectra under conditions where the attenuation length of light within the stop band is comparable to the thickness of the sample. The methodology of the studies developed in this paper is applicable to a wide class of disordered photonic crystal structures.

The application and robustness of the rational choice perspective in the study of intoxicated and angry intentions to aggress

Abstract: Using a rational choice framework, this study examines the effects of alcohol and anger on violent decision making. Male students of legal drinking age participated in a randomized experiment in which intoxication and anger levels were manipulated. Participants read a “bar fight” scenario and completed a series of questions measuring aggressive intentions and the perceived consequences of violence. Results indicate that alcohol and anger interacted to increase one measure of aggressivity, but the perceived costs and benefits of violence were unaffected. Exploratory analyses call into question the robustness of the rational choice model, suggesting that the perspective may not be the general explanation for crime it is proclaimed to be.

Power consumption and throughput in mobile ad hoc networks using directional antennas

Abstract: We present medium access control (MAC) protocols for mobile ad hoc networks that utilize directional antennas. The use of directional antennas in place of traditional omnidirectional antennas reduces interference and thereby improves the throughput performance of the network. An additional advantage of using directional antennas is due to its higher gain from its directivity, which can be utilized to reduce the transmission power during a directional transmission. In order to maximally utilize the savings in the average power consumption in the network, we propose a power control scheme that maintains a minimum transmission power level for effective transmission of packets using directional antennas. We present simulation results showing the throughput advantage and the savings in the average consumed power in the network using the proposed protocol. We also present results showing the maximum possible savings in power consumption in the same network when an ideal power control scheme is applied.

Guidelines for mechanical lung function measurements in psychophysiology

Abstract: Studies in psychophysiology and behavioral medicine have uncovered associations among psychological processes, behavior, and lung function. However, methodological issues specific to the measurement of mechanical lung function have rarely been discussed. This report presents an overview of the physiology, techniques, and experimental methods of mechanical lung function measurements relevant to this research context. Techniques to measure lung volumes, airflow, airway resistance, respiratory resistance, and airflow perception are introduced and discussed. Confounding factors such as ventilation, medication, environmental factors, physical activity, and instructional and experimenter effects are outlined, and issues specific to children and clinical groups are discussed. Recommendations are presented to increase the degree of standardization in the research application and publication of mechanical lung function measurements in psychophysiology.