Showing papers by "North Carolina State University published in 1993"

Co-integration, Error Correction, and the Econometric Analysis of Non-Stationary Data

Abstract: This book provides a wide-ranging account of the literature on co-integration and the modelling of integrated processes (those which accumulate the effects of past shocks). Data series which display integrated behaviour are common in economics, although techniques appropriate to analysing such data are of recent origin and there are few existing expositions of the literature. This book focuses on the exploration of relationships among integrated data series and the exploitation of these relationships in dynamic econometric modelling. The concepts of co-integration and error-correction models are fundamental components of the modelling strategy. This area of time-series econometrics has grown in importance over the past decade and is of interest to econometric theorists and applied econometricians alike. By explaining the important concepts informally, but also presenting them formally, the book bridges the gap between purely descriptive and purely theoretical accounts of the literature. The asymptotic theory of integrated processes is described and the tools provided by this theory are used to develop the distributions of estimators and test statistics. Practical modelling advice, and the use of techniques for systems estimation, are also emphasized. A knowledge of econometrics, statistics, and matrix algebra at the level of a final-year undergraduate or first-year undergraduate course in econometrics is sufficient for most of the book. Other mathematical tools are described as they occur.

Genetics of bacteriocins produced by lactic acid bacteria

Abstract: Lactic acid bacteria produce a variety of bacteriocins that have recently come under detailed investigation. The biochemical and genetic characteristics of these antimicrobial proteins are reviewed and common elements are discussed between the different classes of bacteriocins produced by these Gram-positive bacteria.

Co-integration, Error Correction and the Econometric Analysis of Non-stationary Data

Abstract: This book provides a wide-ranging account of the literature on co-integration and the modelling of integrated processes (those which accumulate the effects of past shocks). Data series which display integrated behaviour are common in economics, although techniques appropriate to analysing such data are of recent origin and there are few existing expositions of the literature. This book focuses on the exploration of relationships among integrated data series and the exploitation of these relationships in dynamic econometric modelling. The concepts of co-integration and error-correction models are fundamental components of the modelling strategy. This area of time-series econometrics has grown in importance over the past decade and is of interest to econometric theorists and applied econometricians alike. By explaining the important concepts informally, but also presenting them formally, the book bridges the gap between purely descriptive and purely theoretical accounts of the literature. The asymptotic theory of integrated processes is described and the tools provided by this theory are used to develop the distributions of estimators and test statistics. Practical modelling advice, and the use of techniques for systems estimation, are also emphasized. A knowledge of econometrics, statistics, and matrix algebra at the level of a final-year undergraduate or first-year undergraduate course in econometrics is sufficient for most of the book. Other mathematical tools are described as they occur.

Oxygen Stress and Superoxide Dismutases

Abstract: The accumulation of dioxygen in Earth's atmosphere allowed for the evolution of aerobic organisms that use O2 as the terminal electron acceptor, thus providing a higher yield of energy compared with fermentation and anaerobic respiration. For example, in aerobic metabolism, the complete breakdown of one molecule of glucose yields a total of 38 molecules of ATP, whereas the anaerobic breakdown of this same glucose molecule to ethanol and CO, yields only 8 ATPs. In its ground state, molecular O2 (dioxygen) is relatively unreactive, yet it is capable of giving rise to lethal reactive ,excited states as free radicals and derivatives. Utilization of O2 proceeds most readily via a complete stepwise, fourelectron reduction to water during which partially reduced reactive intermediates are generated (Fig. 1). The reactive species of reduced dioxygen include the superoxide radical (. 02-), hydrogen peroxide (H202), and the hydroxyl radical (. OH). These and the physiologically energized form of dioxygen, singlet oxygen ('O2), are the biologically most important O2 species. An activation energy of approximately 22 kcal/mol is required to raise molecular O2 from its ground state to its first singlet state. In higher plants, this energy is readily obtained from light quanta via such transfer molecules as Chl (Foote, 1976). A11 of these activated oxygen species are extremely reactive and cytotoxic in a11 organisms. These highly reactive species can react with unsaturated fatty acids to cause peroxidation of essential membrane lipids in the plasmalemma or intracellular organelles. Peroxidation damage of the plasmalemma leads to leakage of cellular contents, rapid desiccation, and cell death. Intracellular membrane damage can affect respiratory activity in mitochondria, cause pigment breakdown, and cause loss of carbon-fixing ability in chloroplasts. Severa1 Calvin-cycle enzymes within chloroplasts are extremely sensitive to H202, and high levels of H202 (the product of superoxide dismutation) directly inhibit C02 fixation (Kaiser, 1979). H202 has also been shown to be active with mixed function oxidases in marking severa1 types of enzymes for proteolytic degradation (Fucci et al., 1983). Superoxide and H202 can react in a \"Haber-Weiss\" reaction to generate the hydroxyl radical ( + OH), which is the most potent oxidant known. The hydroxyl radical indiscriminately and rapidly attacks virtually a11 macromolecules, leading to seri-

Review of chemical-kinetic problems of future NASA missions, II: Mars entries

Abstract: A number of chemical-kinetic problems related to phenomena occurring behind a shock wave surrounding an object flying in the earth atmosphere are discussed, including the nonequilibrium thermochemical relaxation phenomena occurring behind a shock wave surrounding the flying object, problems related to aerobraking maneuver, the radiation phenomena for shock velocities of up to 12 km/sec, and the determination of rate coefficients for ionization reactions and associated electron-impact ionization reactions. Results of experiments are presented in form of graphs and tables, giving data on the reaction rate coefficients for air, the ionization distances, thermodynamic properties behind a shock wave, radiative heat flux calculations, Damkoehler numbers for the ablation-product layer, together with conclusions.

Theoretical basis for separation of multiple linked gene effects in mapping quantitative trait loci

Abstract: It is now possible to use complete genetic linkage maps to locate major quantitative trait loci (QTLs) on chromosome regions. The current methods of QTL mapping (e.g., interval mapping, which uses a pair or two pairs of flanking markers at a time for mapping) can be subject to the effects of other linked QTLs on a chromosome because the genetic background is not controlled. As a result, mapping of QTLs can be biased, and the resolution of mapping is not very high. Ideally when we test a marker interval for a QTL, we would like our test statistic to be independent of the effects of possible QTLs at other regions of the chromosome so that the effects of QTLs can be separated. This test statistic can be constructed by using a pair of markers to locate the testing position and at the same time using other markers to control the genetic background through a multiple regression analysis. Theory is developed in this paper to explore the idea of a conditional test via multiple regression analysis. Various properties of multiple regression analysis in relation to QTL mapping are examined. Theoretical analysis indicates that it is advantageous to construct such a testing procedure for mapping QTLs and that such a test can potentially increase the precision of QTL mapping substantially.

Comparison of 6H-SiC, 3C-SiC, and Si for power devices

Abstract: The drift region properties of 6H- and 3C-SiC-based Schottky rectifiers and power MOSFETs that result in breakdown voltages from 50 to 5000 V are defined. Using these values, the output characteristics of the devices are calculated and compared with those of Si devices. It is found that due to very low drift region resistance, 5000-V SiC Schottky rectifiers and power MOSFETs can deliver on-state current density of 100 A/cm/sup 2/ at room temperature with a forward drop of only 3.85 and 2.95 V, respectively. Both devices are expected to have excellent switching characteristics and ruggedness due to the absence of minority-carrier injection. A thermal analysis shows that 5000-V, 6H-, and 3C-SiC MOSFETs and Schottky rectifiers would be approximately 20 and 18 times smaller than corresponding Si devices, and that operation at higher temperatures and at higher breakdown voltages than conventional Si devices is possible. Also, a significant reduction in the die size is expected. >

Culture of pig embryos

Abstract: Pig embryos can be cultured using a number of different strategies including complex approaches like culture in vivo in a surrogate oviduct (rabbit, sheep, mouse), culture in mouse oviducts in organ culture, and co-culture of embryos with cells in addition to simple approaches like culture in defined media or salt solutions. Addition of serum to medium has been of particular importance where blastocyst development and hatching are required. Pig conceptuses (day 10-15), embryonic discs or cell lines derived from conceptuses can be cultured in complex media like Eagle's minimal essential medium or Dulbecco's modified Eagle's medium with serum, although embryonic discs can be cultured in the absence of serum. In contrast, early stage pig embryos (one-cell to blastocyst) are best cultured in simpler media such as those used for mouse embryos. The media that have been used are all relatively similar in composition. They contain salts and one or more energy sources such as glucose, lactate, or pyruvate with BSA as a macromolecular component. Early attempts to culture pig embryos were not very successful, but some embryos did develop to the blastocyst stage. More recent reports indicate a much higher rate of development with relatively little or no change in media composition. Some workers have reported improved development in medium lacking glucose, which is consistent with findings with laboratory animals such as hamsters. Glutamine can serve as the sole exogenous energy source in medium lacking glucose, lactate and pyruvate. Addition of taurine and hypotaurine to culture medium enhances development of pig embryos in vitro. We suggest, where possible, adoption of a standard medium that could be used by different laboratories and, perhaps, with different species. Use of one medium for different species would simplify experimental protocols, enhance studies of comparative embryonic physiology and metabolism, and expedite transfer of information obtained in different species.

Introduction to SH Lie algebras for physicists

Abstract: UNC-MATH-92/2originally April 27, 1990, revised September 24, 1992INTRODUCTION TO SH LIE ALGEBRAS FOR PHYSICISTSTom LadaJim StasheffMuch of point particle physics can be described in terms of Lie algebras andtheir representations. Closed string field theory, on the other hand, leads to ageneralization of Lie algebra which arose naturally within mathematics in the studyof deformations of algebraic structures [SS]. It also appeared in work on higherspin particles [BBvD]. Representation theoretic analogs arose in the mathematicalanalysis of the Batalin-Fradkin-Vilkovisky approach to constrained Hamiltonians[S6].The sh Lie algebra of closed string field theory [SZ], [KKS], [K], [Wies], [WZ],[Z] is defined on the full Fock complex of the theory, with the BRST differential Q.Following Zwiebach [Z], we stipulate that the string fields B

The concurrency workbench: a semantics-based tool for the verification of concurrent systems

Abstract: The Concurrency Workbench is an automated tool for analyzing networks of finite-state processes expressed in Milner's Calculus of Communicating Systems. Its key feature is its breadth: a variety of different verification methods, including equivalence checking, preorder checking, and model checking, are supported for several different process semantics. One experience from our work is that a large number of interesting verification methods can be formulated as combinations of a small number of primitive algorithms. The Workbench has been applied to the verification of communications protocols and mutual exclusion algorithms and has proven a valuable aid in teaching and research.

Decorrelating decision-feedback multiuser detector for synchronous code-division multiple-access channel

Abstract: A decorrelating decision-feedback detector (DF) for synchronous code-division multiple-access (CDMA) that uses decisions of the stronger users when forming decisions for the weaker ones is described. The complexity of the DF is linear in the number of users, and it requires only one decision per user. It is shown that performance gains with respect to the linear decorrelating detector are more significant for relatively weak users and that the error probability of the weakest user approaches the single-user bound as interferers grow stronger. The error rate of the DF is compared to those of the decorrelator and the two-stage detector. >

Rapid Mini-Prep Isolation of High-Quality Plasmid DNA from Lactococcus and Lactobacillus spp.

Abstract: A simple, rapid plasmid mini-prep procedure for lactococci and lactobacilli which gives high yields and can be performed on overnight broth cultures is presented. Large plasmids were isolated from both lactococci and lactobacilli, including a 70-kb plasmid from Lactobacillus acidophilus C7. The purity of the resulting plasmid DNA makes it suitable for subsequent molecular manipulations. The convenience of the technique makes this rapid mini-prep procedure suitable for routine plasmid isolation from lactic acid bacteria.

Quantitative trait locus effects and environmental interaction in a sample of North American barley germ plasm.

Abstract: Quantitative trait locus (QTL) and QTL x environment (E) interaction effects for agronomic and malting quality traits were measured using a 123-point linkage map and multi-environment phenotype data from an F1-derived doubled haploid population of barley (Hordeum vulgare). The QTL × E interactions were due to differences in magnitude of QTL effects. Highly significant QTL effects were found for all traits at multiple sites in the genome. Yield QTL peaks and support intervals often coincided with plant height and lodging QTL peaks and support intervals. QTL were detected in the vicinity of a previously mapped Mendelian maturity locus and known function probes forα- andβ-amylase genes. The average map density (9.6 cM) should be adequate for molecular marker-assisted selection, particularly since there were few cases of alternative favorable alleles for different traits mapping to the same or adjacent intervals.

Action functionals for relativistic perfect fluids

Abstract: Action functionals describing relativistic perfect fluids are presented. Two of these actions apply to fluids whose equations of state are specified by giving the fluid energy density as a function of particle number density and entropy per particle. Other actions apply to fluids whose equations of state are specified in terms of other choices of dependent and independent fluid variables. Particular cases include actions for isentropic fluids and pressureless dust. The canonical Hamiltonian forms of these actions are derived, symmetries and conserved charges are identified, and the boundary value and initial value problems are discussed. As in previous works on perfect fluid actions, the action functionals considered depend on certain Lagrange multipliers and Lagrangian coordinate fields. Particular attention is paid to the interpretations of these variables and to their relationships to the physical properties of the fluid.

Controlled-release fertilizers to increase efficiency of nutrient use and minimize environmental degradation - a review

Abstract: Total world consumption of fertilizer N, P2O5, and K2O in 1990/1991 was 78, 37, and 26 million tons per annum, respectively, with a projected yearly increase of demand of about 2 to 3%. Trends in crop production (maize and wheat) in the last four decades show that N application rates increased about 15 times whereas its accumulation in grain increased only 3 to 4 times. At the same time nutrient recovery by crops remained relatively low (e.g. about 50% for N). This represents a potentially alarming situation from environmental, economic and resource conservation points of view and indicates an urgent need for improving efficiency of fertilizer use.

A Laccase Associated with Lignification in Loblolly Pine Xylem

Abstract: Peroxidase has been thought to be the only enzyme that oxidizes monolignol precursors to initiate lignin formation in plants. A laccase was purified from cell walls of differentiating xylem of loblolly pine and shown to coincide in time and place with lignin formation and to oxidize monolignols to dehydrogenation products in vitro. These results suggest that laccase participates in lignin biosynthesis and therefore could be an important target for genetic engineering to modify wood properties or to improve the digestibility of forage crops.

Estimation of gene flow from f-statistics.

Abstract: We present theory clarifying the general behavior of FST-based and GST-based estimators of gene flow, and confirm these predictions with simulations. In particular, we use the correlation of genes within groups within populations to define an estimator. The theoretical value of the correlation doe not depend on the number of groups in a population, and properties of the estimated correlation do not depend on the number of groups sampled or the number of individuals sampled per group. This invariance is in contrast to properties of GST. For a complete census of a population, bias and variance considerations would suggest the use of the GST-based estimator of gene flow, but lack of knowledge of population size or group number in practice suggests preference be given to the correlation-based estimator. We acknowledge that these estimators require that several conditions of a population-genetic model be met, since they do not make use of direct observations on the flow of genes. Our results differ from some of those based on simulation in a series of recent papers by M. Slatkin.

The Effect of Sample Size on Estimated Limits for and X Control Charts

Abstract: The results of this study indicate that charts with subgroups of size n require about 400/(n-1) samples, and X charts require about 300 values to estimate control limits that perform like known limits. The results also indicate that using estimated con..

Sensing atmospheric water vapor with the global positioning system

Abstract: Global Positioning System (GPS) receivers, water vapor radiometers (WVRs), and surface meteorological equip- ment were operated at both ends of a 50-kin baseline in Colorado to measure the precipitable water vapor (PWV) and wet delay in the line-of-sight to GPS satellites Using high pre- cision orbits, WVR-measured and GPS-inferred PWV differences between the two sites usually agreed to better than 1 min Using less precise on-line broadcast orbits increased the discrepancy by 30% Data simulations show that GPS mea- surements can provide ram-level separate PWV estimates for the two sites, as opposed to just their difference, if baselines exceed 500 km and the highest accuracy GPS orbits are used

The atmosphere during the younger dryas.

Abstract: One of the most dramatic climate change events observed in marine and ice core records is the Younger Dryas, a return to near-glacial conditions that punctuated the last deglaciation. High-resolution, continuous glaciochemical records, newly retrieved from central Greenland, record the chemical composition of the arctic atmosphere at this time. This record shows that both the onset and the termination of the Younger Dryas occurred within 10 to 20 years and that massive, frequent, and short-term (decadal or less) changes in atmospheric composition occurred throughout this event. Changes in atmospheric composition are attributable to changes in the size of the polar atmospheric cell and resultant changes in source regions and to the growth and decay of continental biogenic source regions.

Ca2+-Induced Gelation of Pre-heated Whey Protein Isolate

Abstract: Addition of CaCl2 to pre-heated whey protein isolate (WPI) suspensions caused an increase in turbidity when pre-heating temperatures were greater than or equal to 64 degrees C. Pre-heating to greater than or equal to 70 degrees C was required for gelation. WPI suspensions which contained CaCl2 became turbid at 45 degrees C and formed thermally induced gels at 66 degrees C. Thermally and Ca2+-induced gels showed significant time/temperature effects but the penetration force values in the Ca2+-induced gels were always lower. However, Ca2+-induced gels were higher in shear stress at fracture. The Ca2+-induced gels had a fine-stranded protein matrix that was more transparent than the thermally induced gels, which showed a particulate microstructure.

A linear-time model-checking algorithm for the alternation-free modal mu-calculus

Abstract: We develop a model-checking algorithm for a logic that permits propositions to be defined with greatest and least fixed points of mutually recursive systems of equations. This logic is as expressive as the alternation-free fragment of the modal mu-calculus identified by Emerson and Lei, and it may therefore be used to encode a number of temporal logics and behavioral preorders. Our algorithm determines whether a process satisfies a formula in time proportional to the product of the sizes of the process and the formula; this improves on the best known algorithm for similar fixed-point logics.

Child maltreatment and youthful problem behavior

Abstract: This paper adds to an accumulating body of research on the risk of delinquency among maltreated children. We use a prospective research design to address the following questions: (1) To what extent are maltreated children at risk of delinquency? (2) Is their rate of delinquency greater than that of two court-aged, nonmaltreated comparison samples: impoverished children and school children in general? (3) What is the effect of maltreatment net of age, race, gender, and family structure? (4) Is type of maltreatment associated with specific types of juvenile offenses? Maltreated children have higher rates of delinquency complaints than nonmaltreated school and impoverished children, but the effects diminish considerably when the demographic and family structure variables are controlled. In the maltreatment-school comparison, an overall maltreatment effect remains for complaints in general and status offenses, but not for property or violent offenses. Maltreated children are significantly different from nonmaltreated poor children for status offenses only. Specific forms of maltreatment are not especially predictive of any offense type. Generally, we conclude that the maltreatment-delinquency relationship has been exaggerated in previous research.

Linear Optimization and Extensions: Theory and Algorithms

Abstract: A solution to get the problem off, have you found it? Really? What kind of solution do you resolve the problem? From what sources? Well, there are so many questions that we utter every day. No matter how you will get the solution, it will mean better. You can take the reference from some books. And the linear optimization and extensions theory and algorithms is one book that we really recommend you to read, to get more solutions in solving this problem.

The nonlinear mixed effects model with a smooth random effects density

Abstract: SUMMARY The fixed parameters of the nonlinear mixed effects model and the density of the random effects are estimated jointly by maximum likelihood. The density of the random effects is assumed to be smooth but is otherwise unrestricted. The method uses a series expansion that follows from the smoothness assumption to represent the density and quadrature to compute the likelihood. Standard algorithms are used for optimization. Empirical Bayes estimates of random coefficients are obtained by computing posterior modes. The method is applied to data from pharmacokinetics, and properties of the method are investigated by application to simulated data.