Showing papers by "North Carolina State University published in 1998"

The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis

Abstract: A new method for analysing nonlinear and non-stationary data has been developed. The key part of the method is the empirical mode decomposition method with which any complicated data set can be dec...

An Empirical Analysis of the Relation between Board of Director Composition and Financial Statement Fraud

Abstract: This study empirically tests the prediction that the inclusion of larger proportions of outside members on the board of directors significantly reduces the likelihood of financial statement fraud. Results from logit regression analysis of 75 fraud and 75 no-fraud firms indicate that no- fraud firms have boards with significantly higher percentages of outside members than fraud firms. Results are not sensitive to the definition of outside directors used, given that no-fraud firms have significantly higher percentages of both "grey" and "independent" directors than fraud firms. Interestingly, the presence of an audit committee does not significantly affect the likelihood of financial statement fraud. Additionally, as outside director ownership in the firm and outside director tenure on the board increase and as the number of outside directorships in other firms held by outside directors decreases, the likelihood of financial statement fraud decreases.

Resident enteric bacteria are necessary for development of spontaneous colitis and immune system activation in interleukin-10-deficient mice.

Abstract: Mice with targeted deletion of the gene for interleukin-10 (IL-10) spontaneously develop enterocolitis when maintained in conventional conditions but develop only colitis when kept in specific-pathogen-free (SPF) environments. This study tested the hypothesis that enteric bacteria are necessary for the development of spontaneous colitis and immune system activation in IL-10-deficient mice. IL-10-deficient mice were maintained in either SPF conditions or germfree conditions or were populated with bacteria known to cause colitis in other rodent models. IL-10-deficient mice kept in SPF conditions developed colitis in all segments of the colon (cecum and proximal and distal colon). These mice exhibited immune system activation as evidenced by increased expression of CD44 on CD4+ T cells; increased mesenteric lymph node cell numbers; and increased production of immunoglobulin A (IgA), IgG1, and IL-12 p40 from colon fragment cultures. Mice populated with bacterial strains, including Bacteroides vulgatus, known to induce colitis in other rodent models had minimal colitis. Germfree IL-10-deficient mice had no evidence of colitis or immune system activation. We conclude therefore that resident enteric bacteria are necessary for the development of spontaneous colitis and immune system activation in IL-10-deficient mice.

BRASSINOSTEROIDS: Essential Regulators of Plant Growth and Development

Abstract: Brassinosteroids (BRs) are growth-promoting natural products found at low levels in pollen, seeds, and young vegetative tissues throughout the plant kingdom. Detailed studies of BR biosynthesis and metabolism, coupled with the recent identification of BR-insensitive and BR-deficient mutants, has greatly expanded our view of steroids as signals controlling plant growth and development. This review examines the microchemical and molecular genetic analyses that have provided convincing evidence for an essential role of BRs in diverse developmental programs, including cell expansion, vascular differentiation, etiolation, and reproductive development. Recent advances relevant to the molecular mechanisms of BR-regulated gene expression and BR signal transduction are also discussed.

Sustainability of Transgenic Insecticidal Cultivars: Integrating Pest Genetics and Ecology

Abstract: ▪ Abstract This review examines potential impacts of transgenic cultivars on insect population dynamics and evolution. Experience with classically bred, insecticidal cultivars has demonstrated that a solid understanding of both the target insect's ecology and the cultivar's performance under varied field conditions will be essential for predicting area-wide effects of transgenic cultivars on pest and natural enemy dynamics. This experience has also demonstrated the evolutionary capacity of pests for adaptive response to insecticidal traits in crops. Biochemical and genetic studies of insect adaptation to the Bacillus thuringiensis (Bt) toxins expressed by currently marketed transgenic cultivars indicate a high risk for rapid adaptation if these cultivars are misused. Theoretical and practical issues involved in implementing strategies to delay pest adaptation to insecticidal cultivars are reviewed. Emphasis is placed on examining the “high dose”/refuge strategy that has become the goal of industry and reg...

Estimating the rate of evolution of the rate of molecular evolution.

Abstract: A simple model for the evolution of the rate of molecular evolution is presented. With a Bayesian approach, this model can serve as the basis for estimating dates of important evolutionary events even in the absence of the assumption of constant rates among evolutionary lineages. The method can be used in conjunction with any of the widely used models for nucleotide substitution or amino acid replacement. It is illustrated by analyzing a data set of rbcL protein sequences.

The Roles of Price, Performance, and Expectations in Determining Satisfaction in Service Exchanges:

Abstract: In this article, the authors examine the roles that price, performance, and expectations play in determining satisfaction in a discrete service exchange. The authors maintain that the price fluctua...

PhotochemCAD‡: A Computer‐Aided Design and Research Tool in Photochemistry

Abstract: A database of absorption and fluorescence spectra, including molar absorption coefficients and fluorescence quantum yields, has been compiled for 125 photochemically relevant compounds. An accompanying program enables calculation of oscillator strengths, natural radiative lifetimes, transition dipole moments, Forster energy-transfer rates, multicomponent analysis, simulations of fluorescence spectra upon energy transfer among linear arrays of pigments, calculations of blackbody radiator curves at different temperatures and Lorentzian and Gaussian peak distributions. The program runs under Windows 95 and is equipped with extensive literature references and help features.

Model choice: A minimum posterior predictive loss approach

Abstract: SUMMARY Model choice is a fundamental and much discussed activity in the analysis of datasets. Nonnested hierarchical models introducing random effects may not be handled by classical methods. Bayesian approaches using predictive distributions can be used though the formal solution, which includes Bayes factors as a special case, can be criticised. We propose a predictive criterion where the goal is good prediction of a replicate of the observed data but tempered by fidelity to the observed values. We obtain this criterion by minimising posterior loss for a given model and then, for models under consideration, selecting the one which minimises this criterion. For a broad range of losses, the criterion emerges as a form partitioned into a goodness-of-fit term and a penalty term. We illustrate its performance with an application to a large dataset involving residential property transactions.

Solar fusion cross sections

Abstract: We review and analyze the available information on the nuclear-fusion cross sections that are most important for solar energy generation and solar neutrino production. We provide best values for the low-energy cross-section factors and, wherever possible, estimates of the uncertainties. We also describe the most important experiments and calculations that are required in order to improve our knowledge of solar fusion rates.

Contributions of Microbes in Vertebrate Gastrointestinal Tract to Production and Conservation of Nutrients

Abstract: Stevens, C. Edward, and Ian D. Hume. Contributions of Microbes in Vertebrate Gastrointestinal Tract to Production and Conservation of Nutrients. Physiol. Rev. 78: 393–427, 1998. — The vertebrate ga...

Competitive Priorities in Operations Management

Abstract: Identifying manufacturers' competitive priorities has long been considered a key element in manufacturing strategy research However, relatively little effort has been devoted to measurement of these constructs in published research In this study we develop scales for commonly accepted competitive priorities, cost importance, quality importance, delivery-time importance, and flexibility importance We assess how well the scales capture the constructs that they represent using data collected from 114 manufacturing plants in the United States The findings suggest that the instrument developed can provide reliable data and that the constructs measured are valid In addition, comparisons between pairs of informants representing the same business indicate that the perceptual measures of competitive priorities are as reliable as point estimates of routine, seemingly objective information

Estimating species richness: the importance of heterogeneity in species detectability

Abstract: Estimating species richness (i.e., the actual number of species present in a given area) is a basic objective of many field studies carried out in community ecology and is also of crucial concern when dealing with the conservation and management of biodiversity. In most studies, the total number of species recorded in an area at a given time is taken as a measure of species richness. Here we use a capture–recapture approach to species richness estimation with North American Breeding Bird Survey (BBS) data in order to estimate species detectability and thus gain insight about its importance. In particular, competing models making different assumptions about species detectability are available. We carried out analyses on all survey routes of four states, Arizona, Maryland, North Dakota, and Wisconsin, in two years, 1970 and 1990. These states were chosen to provide contrasting habitats, bird species composition, and survey quality. We investigated the effect of state, year, and observer ability on the propo...

The effects of image misregistration on the accuracy of remotely sensed change detection

Abstract: Image misregistration has become one of the significant bottlenecks for improving the accuracy of multisource data analysis, such as data fusion and change detection. In this paper, the effects of misregistration on the accuracy of remotely sensed change detection were systematically investigated and quantitatively evaluated. This simulation research focused on two interconnected components. In the first component, the statistical properties of the multispectral difference images were evaluated using semivariograms when multitemporal images were progressively misregistered against themselves and each other to investigate the band, temporal, and spatial frequency sensitivities of change detection to image misregistration. In the second component, the ellipsoidal change detection technique, based on the Mahalanobis distance of multispectral difference images, was proposed and used to progressively detect the land cover transitions at each misregistration stage for each pair of multitemporal images. The impact of misregistration on change detection was then evaluated in terms of the accuracy of change detection using the output from the ellipsoidal change detector. The experimental results using Landsat Thematic Mapper (TM) imagery are presented. It is interesting to notice that, among the seven TM bands, band 4 (near-infrared channel) is the most sensitive to misregistration when change detection is concerned. The results from false change analysis indicate a substantial degradation in the accuracy of remotely sensed change detection due to misregistration. It is shown that a registration accuracy of less than one-fifth of a pixel is required to achieve a change detection error of less than 10%.

Agent communication languages: rethinking the principles

Abstract: Agent communication languages have been used for years in proprietary multiagent systems. Yet agents from different vendors-or even different research projects-cannot communicate with each other. The author looks at the underlying reasons and proposes a conceptual shift from individual agent representations to social interaction.

Recent advances in understanding lignin biosynthesis

Abstract: After a long period of little change, the basic concepts of lignin biosynthesis have been challenged by new results from genetic modification of lignin content and composition. New techniques for making directed genetic changes in plants, as well as improvements in the analytical techniques used to determine lignin content and composition in plant cell walls, have been used in experimental tests of the accepted lignin biosynthetic pathway. The lignins obtained from genetically modified plants have shown unexpected properties, and these findings have extended the known range of variation in lignin content and composition. These results argue that the accepted lignin biosynthetic pathway is either incomplete or incorrect, or both; and also suggest that plants may have a high level of metabolic plasticity in the formation of lignins. If this is so, the properties of novel lignins could be of significant scientific and practical interest.

Brittle and Ductile Behavior in Carbon Nanotubes

Abstract: Large-scale molecular dynamics simulations were used to study the response of carbon nanotubes to a tensile load. Plastic or brittle behaviors can occur depending upon the external conditions and tube symmetry. All tubes are brittle at high strain and low temperature, while at low strain and high temperature armchair $(n,n)$ nanotubes can be completely or partially ductile. In zigzag $(n,0)$ tubes ductile behavior is expected for tubes with $nl14$, while larger tubes are completely brittle. In both cases the curvature determines the mechanical response.

The how and why of electronic noses

Abstract: Witnessing the swift advances in the electronic means of seeing and hearing, scientists and engineers scent a market for systems mimicking the human nose. Already commercial systems from several companies are targeting applications, present and potential, that range from quality assurance of food and drugs to medical diagnosis, environmental monitoring, safety and security and military use. Here, the authors outline the major transducer technologies-in one sense, the key component of an electronic nose.

A Flexible, Multipurpose Method for Recording Vegetation Composition and Structure

Abstract: We present a flexible protocol for recording vegetation composition and structure that is appropriate for diverse applications, is scale transgressive, yields data compatible with those from commonly used methods, and is applicable across a broad range of terrestrial vegetation. The protocol is intended to be flexible in the intensity of use and commitment of time, and sufficiently open in architecture as to be adaptable to unanticipated applications. The standard observation unit is a 10 x 10 m (0.01 ha) quadrat or "module." Where the extent of homogeneous vegetation is sufficient, multiple modules are combined to form a larger, more representative sample-unit. All vascular species are recorded by cover class and in intensively sampled modules as present or absent in sets of nested quadrats. For each module, tree stems are tallied by diameter class; species with exceptionally high or low stem density can be sub- or supersampled to allow efficient collection of data and assessment of population structure. The most common plot configuration consists of 10 modules arranged in a 2 x 5 array with four modules sampled intensively; this size is often necessary to capture the complexity of a forest community. For rapid reconnaissance or inventory purposes, fewer modules are typically employed, and less information is collected.

Utility of SSRs for Determining Genetic Similarities an Relationships in Maize Using an Agarose Gel System

Abstract: Among maize (Zea maize L.) breeders, there is a heightened awareness of the necessity for both maintaining genetic diversity for crop improvement and improving the quality of genetic resource management. Restriction fragment length polymorphisms (RFLPs) and isozymes can serve as genetic markers for estimating divergence or diversity ; however, the limited number of polymorphic isozyme loci available and the labor intensive and time consuming nature of RFLPs make their use for this purpose prohibitive. Simple sequence repeats (SSRs), when resolved using agarose gels, may be a viable and cost-effective alternative to RFLPs and isozymes. Ninety-four elite maize inbred lines, representative of the genetic diversity among lines derived from the Corn Belt Dent and Southern Dent maize races, were assayed for. polymorphism at 70 SSR marker loci using agarose gels. The 365 alleles identified served as raw data for estimating genetic similarities among these lines. The patterns of genetic divergence revealed by the SSR polymorphisms were consistent with known pedigrees. A cluster analysis placed the inbred lines in nine clusters that correspond to major heterotic groups or market classes for North American maize. A unique fingerprint for each inbred line could be obtained from as few as five SSR loci. The utility of polymerase chain reaction (PCR)-based markers such as SSRs for measuring genetic diversity, for assigning lines to heterotic groups and for genetic fingerprinting equals or exceeds that of RFLP markers, a property that may prove a valuable asset for a maize breeding program.

A Longitudinal Study of Engineering Student Performance and Retention. V. Comparisons with Traditionally‐Taught Students

Abstract: In a longitudinal study at North Carolina State University, a cohort of students took five chemical engineering courses taught by the same instructor in five consecutive semesters. The courses made extensive use of active and cooperative learning and a variety of other techniques designed to address a broad spectrum of learning styles. Previous reports on the study summarized the instructional methods used in the experimental course sequence, described the performance of the cohort in the introductory chemical engineering course, and examined performance and attitude differences between students from rural and urban backgrounds and between male and female students.1–4 This paper compares outcomes for the experimental cohort with outcomes for students in a traditionally-taught comparison group. The experimental group outperformed the comparison group on a number of measures, including retention and graduation in chemical engineering, and many more of the graduates in this group chose to pursue advanced study in the field. Since the experimental instructional model did not require small classes (the smallest of the experimental classes had 90 students) or specially equipped classrooms, it should be adaptable to any engineering curriculum at any institution.

Mechanism of strain release in carbon nanotubes

Abstract: Static and dynamical properties of carbon nanotubes under uniaxial tension have been investigated via quantum and classical simulations. In strained nanotubes at high temperatures we observe the spontaneous formation of double pentagon-heptagon defect pairs. Tubes containing these defects are energetically preferred to uniformly stretched tubes at strains greater than 5%. These topological defects act as nucleation centers for the formation of dislocations in the originally ideal graphite network, and they constitute the onset of a plastic deformation of the carbon nanotube. The mechanism of formation of such defects, their energetics, and transformations are described. @S0163-1829~98!50208-1# Since their discovery in 1991, 1 carbon nanotubes have attracted much interest due to their peculiar character at a crossroad between traditional carbon fibers and fullerenes. They hold substantial promise for use as superstrong fibers, catalysts, and as components of novel electronic devices. Despite the potential impact that new composites based on carbon nanotubes would have in many areas of science and industry, very little is known about the microscopic origin of their strength and a complete theoretical understanding of their behavior is desirable. The excellent resistance of carbon nanotubes to bending has already been observed experimentally and studied theoretically. 2‐4 The remarkable flexibility of the hexagonal network allows the system to sustain very high bending angles, kinks, and highly strained regions. In addition, nanotubes are observed to be extremely resilient, suggesting that even largely distorted configurations ~axial compression, twisting! can be due to elastic deformations with no atomic defects involved. 2,3,5,6

A review of 3-D packaging technology

Abstract: This paper reviews the state-of-the-art in three-dimensional (3-D) packaging technology for very large scale integration (VLSI). A number of bare dice and multichip module (MCM) stacking technologies are emerging to meet the ever increasing demands for low power consumption, low weight and compact portable systems. Vertical interconnect techniques are reviewed in detail. Technical issues such as silicon efficiency, complexity, thermal management, interconnection density, speed, power etc. are critical in the choice of 3-D stacking technology, depending on the target application, and are briefly discussed.

Design, Synthesis, and Photodynamics of Light-Harvesting Arrays Comprised of a Porphyrin and One, Two, or Eight Boron-Dipyrrin Accessory Pigments

Abstract: Light-harvesting arrays containing one, two, or eight boron-dipyrrin (BDPY) pigments and one porphyrin (free base or Zn chelate) have been synthesized using a modular building block approach. The reaction of pyrrole and 4-(BDPY)benzaldehyde or 3,5-bis(BDPY)benzaldehyde, prepared by Pd-mediated ethynylation with the corresponding iodo-benzaldehydes, affords the desired BDPY-porphyrin array in yields of 10−58%. The arrays are soluble in organic solvents and have been characterized by static and time-resolved absorption and fluorescence spectroscopy. The blue-green BDPY absorption complements spectral coverage of the porphyrin chromophores and rivals the intensity of the porphyrin Soret band when eight BDPY accessory pigments are present. Efficient energy transfer from the BDPY pigment(s) to the porphyrin (free base or Zn-chelate) is observed in arrays containing one or two (>90%) or eight (>85%) accessory pigments per porphyrin. Biphasic excited-state decay behavior is exhibited by the BDPY pigments in isol...

Self-assembly of single electron transistors and related devices

Abstract: For the past 40 years, since the invention of the integrated circuit, the number of transistors on a computer chip has doubled roughly every 18 months. As the limits of photolithography are rapidly approached, however, it is becoming clear that continued increases in circuit density will require fairly dramatic changes in the way transistors are designed and operated. This review summarizes current strategies for fabricating transistors which operate based on the flow of single electrons through nanometre-sized metal and semiconductor particles; i.e. single electron transistors (SETs). Because the room temperature operation of SETs requires nanoparticles <10 nm in diameter, we focus mainly on devices which have the potential for being assembled from the solution phase (non-lithographic systems). Several applications of SETs are discussed in addition to the major hurdles which must be overcome for their implementation in electronic device technology.

Detecting Marker-Disease Association by Testing for Hardy-Weinberg Disequilibrium at a Marker Locus

Abstract: We review and extend a recent suggestion that fine-scale localization of a disease-susceptibility locus for a complex disease be done on the basis of deviations from Hardy-Weinberg equilibrium among affected individuals. This deviation is driven by linkage disequilibrium between disease and marker loci in the whole population and requires a heterogeneous genetic basis for the disease. A finding of marker-locus Hardy-Weinberg disequilibrium therefore implies disease heterogeneity and marker-disease linkage disequilibrium. Although a lack of departure of Hardy-Weinberg disequilibrium at marker loci implies that disease susceptibilityweighted linkage disequilibria are zero, given disease heterogeneity, it does not follow that the usual measures of linkage disequilibrium are zero. For disease-susceptibility loci with more than two alleles, therefore, care is needed in the drawing of inferences from marker Hardy-Weinberg disequilibria.

Coordinated clearance of periciliary liquid and mucus from airway surfaces.

Abstract: Airway surface liquid is comprised of mucus and an underlying, watery periciliary liquid (PCL). In contrast to the well-described axial transport of mucus along airway surfaces via ciliary action, theoretical analyses predict that the PCL is nearly stationary. Conventional and confocal microscopy of fluorescent microspheres and photoactivated fluorescent dyes were used with well-differentiated human tracheobronchial epithelial cell cultures exhibiting spontaneous, radial mucociliary transport to study the movements of mucus and PCL. These studies showed that the entire PCL is transported at approximately the same rate as mucus, 39.2+/-4.7 and 39.8+/-4.2 micrometer/sec, respectively. Removing the mucus layer reduced PCL transport by > 80%, to 4.8+/-0.6 micrometer/sec, a value close to that predicted from theoretical analyses of the ciliary beat cycle. Hence, the rapid movement of PCL is dependent upon the transport of mucus. Mucus-dependent PCL transport was spatially uniform and exceeded the rate expected for pure frictional coupling with the overlying mucus layer; hence, ciliary mixing most likely accelerates the diffusion of momentum from mucus into the PCL. The cephalad movement of PCL along airway epithelial surfaces makes this mucus-driven transport an important component of salt and water physiology in the lung in health and disease.

Inverse Eigenvalue Problems

Abstract: A collection of inverse eigenvalue problems are identified and classified according to their characteristics. Current developments in both the theoretic and the algorithmic aspects are summarized and reviewed in this paper. This exposition also reveals many open questions that deserve further study. An extensive bibliography of pertinent literature is attached.

Economies of Scale and Scope at Large Commercial Banks: Evidence from the Fourier Flexible Functional Form

Abstract: This study contributes new evidence on bank cost efficiency by computing efficiency measures from estimated cost functions. It overcomes deficiencies of previous studies by restricting the sample to homogenous banks and by estimating Fourier Flexible cost functions. A Fourier Flexible cost function, which has the Translog nested within it, can potentially approximate an arbitrary cost function well over the function's entire range. Functions consistent with both the "intermediation" and "production" approaches are estimated using 1986 and 1990 Call Report data for large banks. The computed efficiency measures show little evidence of scale and scope economies. In addition, tests reveal Translog cost functions to be biased.