Showing papers by "North Carolina State University published in 1984"

Estimating F-statistics for the analysis of population structure.

Abstract: This journal frequently contains papers that report values of F-statistics estimated from genetic data collected from several populations. These parameters, FST, FIT, and FIS, were introduced by Wright (1951), and offer a convenient means of summarizing population structure. While there is some disagreement about the interpretation of the quantities, there is considerably more disagreement on the method of evaluating them. Different authors make different assumptions about sample sizes or numbers of populations and handle the difficulties of multiple alleles and unequal sample sizes in different ways. Wright himself, for example, did not consider the effects of finite sample size. The purpose of this discussion is to offer some unity to various estimation formulae and to point out that correlations of genes in structured populations, with which F-statistics are concerned, are expressed very conveniently with a set of parameters treated by Cockerham (1 969, 1973). We start with the parameters and construct appropriate estimators for them, rather than beginning the discussion with various data functions. The extension of Cockerham's work to multiple alleles and loci will be made explicit, and the use of jackknife procedures for estimating variances will be advocated. All of this may be regarded as an extension of a recent treatment of estimating the coancestry coefficient to serve as a mea-

Testing for unit roots in autoregressive-moving average models of unknown order

Abstract: SUMMARY Recently, methods for detecting unit roots in autoregressive and autoregressivemoving average time series have been proposed. The presence of a unit root indicates that the time series is not stationary but that differencing will reduce it to stationarity. The tests proposed to date require specification of the number of autoregressive and moving average coefficients in the model. In this paper we develop a test for unit roots which is based on an approximation of an autoregressive-moving average model by an autoregression. The test statistic is standard output from most regression programs and has a limit distribution whose percentiles have been tabulated. An example is provided.

Genre as social action

Abstract: This essay proposes a conception of genre based on conventionalized social motives which are found in recurrent situation‐types. The thesis is that genre must be conceived in terms of rhetorical action rather than substance or form.

Generalized Hypercube and Hyperbus Structures for a Computer Network

Abstract: A general class of hypercube structures is presented in this paper for interconnecting a network of microcomputers in parallel and distributed environments. The interconnection is based on a mixed radix number system and the technique results in a variety of hypercube structures for a given number of processors N, depending on the desired diameter of the network. A cost optimal realization is obtained through a process of discrete optimization. The performance of such a structure is compared to that of other existing hypercube structures such as Boolean n-cube and nearest neighbor mesh computers.

Testing for Unit Roots in Seasonal Time Series

Abstract: Regression estimators of coefficients in seasonal autoregressive models are described. The percentiles of the distributions for time series that have unit roots at the seasonal lag are computed by Monte Carlo integration for finite samples and by analytic techniques and Monte Carlo integration for the limit case. The tabled distributions may be used to test the hypothesis that a time series has a seasonal unit root.

Primary productivity and particle fluxes on a transect of the equator at 153°W in the Pacific Ocean

Abstract: Primary productivity (14C) and mass flux measurements using a free-drifting sediment trap deployed at 900 m were made at four stations in the Pacific Ocean between 12°N and 6°S at 153°W. The latitudinal variations in productivity were consistent with historical patterns showing the equator as a zone of high production and the oligotrophic waters north of the equatorial region as an area of low productivity. The correlation coefficient between the two sets of independent measurements was 0.999, indicating that in this oceanic area the activity of the primary producers was closely related to the total mass flux. A re-examination of historical data suggests that the downward flux of particulate organic carbon varies in direct proportion to the quotient of surface primary production raised to the 1.4 power and depth raised to the 0.63 power.

Cyclic Pricing by a Durable Goods Monopolist

Abstract: In the model of this paper a monopoly seller of a durable good holds periodic sales as a means of price discrimination. A new cohort of consumers enters the market in each period, interested in purchasing the good either immediately or after a delay. Within each cohort, consumers vary in their tastes for the good. Under broad conditions, the seller will vary the price over time. In most periods, he will charge a price just low enough to sell immediately to consumers with a high willingness to pay. Periodically, however, he will drop the price far enough to sell to an accumulated group of consumers with a low willingness to pay.

Queueing networks with blocking: a bibliography

Abstract: In recent years, queueing networks with blocking have been studied by researchers from various research communities such as Computer Performance Modelling, Operations Research, and Industrial Engineering. In view of this, related results are scattered throughout various journals. The bibliography given below is the result of a first attempt to compile an exhaustive list of related papers in which analytic investigations (exact or approximate) or numerical investigations of queueing networks with blocking have been reported.

Analysis of variants affecting the catalase developmental program in maize scutellum

Abstract: The catalase of maize scutella is coded for by two loci, Cat1 and Cat2, which are differentially expressed in this tissue during early seedling growth. Two variant lines have been previously identified in which the developmental program for the expression of the Cat2 structural gene in the scutellum has been altered. Line R6–67 exhibits higher than normal levels of CAT-2 catalase in this tissue after four days of postgerminative growth. This phenotype is controlled by a temporal regulatory gene designated Car1. Line A16 exhibits a CAT-2 null phenotype. Further analysis of Car1 verifies the initial indication that it is trans-acting and exhibits strict tissue (scutellum) specificity. A screen of other available inbred lines uncovered eight additional catalase high-activity lines. All eight lines exhibit significantly higher than normal levels of CAT-2 protein. Two of these lines have been shown to be regulated by Car1 as in R6–67. Another line (A338) uncovered during the screen exhibits a null phenotype for CAT-2 protein and resembles A16. Catalase activity levels are low in the scutellum and no CAT-2 CRM (cross-reacting material) is present in the tissues of this line. Also, unlike most maize lines, CAT-2 cannot be induced in the leaf tissue of A338 upon exposure to light. Finally, a single line (A337), demonstrating a novel catalase developmental program, was identified.

The feasible solution in signal restoration

Abstract: The feasible solution to the signal restoration problem is defined as the one which satisfies all constraints which can be imposed on the true solution. A very important set of constraints can be obtained by examining the statistics of the noise. These and other constraints can be described as closed convex sets. Thus, projection onto closed convex sets is the numerical method used to obtain a feasible solution. Examples of this method demonstrate its usefulness in one-and two-dimensional signal restoration. The limitations of the method are discussed.

Monte Carlo Comparison of ANOVA, MIVQUE, REML, and ML Estimators of Variance Components

Abstract: For the one-way classification random model with unbalanced data, we compare five estimators of σ2 a and σ2 e , the among- and within-treatments variance components: analysis of variance (ANOVA), maximum likelihood (ML), restricted maximum likelihood (REML), and two minimum variance quadratic unbiased (MIVQUE) estimators. MIVQUE(0) is MIVQUE with a priori values = 0 and = 1; MIVQUE(A) is MIVQUE with the ANOVA estimates used as a priori's, We enforce nonnegativity for all estimators, setting any negative estimate to zero in accord with usual practice. The estimators are compared through their biases and MSE's, estimated by Monte Carlo simulation. Our results indicate that the ANOVA estimators perform well, except with seriously unbalanced data when σ2 a /σ2 e > 1; ML is excellent when σ2 a /σ2 e < 0.5, and MIVQUE(A) is adequate; further iteration to the REML estimates is unnecessary. When σ2 a /σ2 e ≥ 1, MIVQUE(0) (the default for SASS PROCEDURE VARCOMP) is poor for estimating σ2 a and very poor for σ2 e ,...

Optimal Estimation Of Voltage Phasors And Frequency Deviation Using Linear And Non-Linear Kalman Filtering: Theory And Limitations

Abstract: This paper presents two techniques for optimal tracking of power system voltage phasors and frequency deviation. The first technique is based on a two-state linear Kalman filter model. The second technique is based on a three-state extended Kalman filter model. In the latter the frequency deviation is considered a third state variable and is recursively computed on-line. It is shown that the Kalman filter models are well suited for noisy measurements. The effect of sampling rate, computer burden and overall accuracy are also investigated. Finally comparison with other techniques is presented.

Covariances of relatives stemming from a population undergoing mixed self and random mating.

Abstract: We consider covariances of all parent and first-generation relatives from outcrossing or self-fertilization in a parent population that is in equilibrium with respect to these processes. The results, which are for any number of alleles and loci with additive and dominance effects, are phrased in terms of six quadratic genetic components whose coefficients are given by descent measures for equilibrium populations. Because of the variation in the inbreeding coefficients for this system of mating, the expressions include joint contributions of loci to the variances and covariances of relatives. By inclusion of the full complement of relatives, all quadratic components can be estimated. The findings of Ghai (1982, Biometrics 38, 87-92) for compound functions of the covariances with two alleles at a single locus are analyzed in terms of the more general model.

Thermally Induced Gelation of Selected Comminuted Muscle Systems–Rheological Changes during Processing, Final Strengths and Microstructure

Abstract: Sols were prepared from comminuted fish (surimi), beef, pork and turkey muscles. Continuous evaluation of changes in structural rigidity and energy damping during heating of the sols from 3° to 95°C was performed in a nondestructive, temperature-controlled Thermal Scanning Rigidity Monitor. Surimi presented major rigidity transitions at 40°. 48° and 65°C; beef at 43°. 56° and 69°C; pork at 44°, 53° and 69°C; and turkey at 50°, 53° and 79°C. All materials exhibited rapid decrease in energy damping (i.e. increase in elasticity) over a short temperature span. Failure testing of gels indicated differences in strength and deformability. SEM micrographs provided an insight into structural features of the gels.

Molecular evolution of chloroplast DNA sequences.

Abstract: Comparative data on the evolution of chloroplast genes are reviewed. The chloroplast genome has maintained a similar structural organization over most plant taxa so far examined. Comparisons of nucleotide sequence divergence among chloroplast genes reveals marked similarity across the plant kingdom and beyond to the cyanobacteria (blue-green algae). Estimates of rates of nucleotide substitution indicate a synonymous rate of 1.1 x 10(-9) substitutions per site per year. Noncoding regions also appear to be constrained in their evolution, although addition/deletion events are common. There have also been evolutionary changes in the distribution of introns in chloroplast encoded genes. Relative to mammalian mitochondrial DNA, the chloroplast genome evolves at a conservative rate.

The Fourier Flexible Form

Abstract: One perspective on the recent work in flexible functional forms is that the use of such forms represents an attempt to remove the modelinduced augmenting hypothesis that is inevitably linked to parametric statistical inference. The Fourier flexible form is discussed from this perspective. The discussion relies on heuristic and graphical arguments rather than formal mathematics. The generality of parametric statistical inference is limited by the augmenting hypothesis induced by model specification. For instance, to conclude that rejection of the integrability conditions in a translog consumer demand system implies rejection of the theory of consumer demand requires the augmenting hypothesis that all possible consumer demand systems must belong to the translog family (Christensen, Jorgenson, and Lau). This reliance on an assumed parametric model is not only philosophically distasteful but is of practical importance in applications. Estimators can be seriously biased by specification error; a test can reject a null hypothesis with a probability that greatly exceeds its nominal rejection probability (Gallant 1981). One way to interpret the recent work in flexible functional forms is to see it as the use of richer parametric families of models in an attempt to reduce these two sorts of statistical biases--estimator bias and excess rejection probability. Most of the flexible forms that have appeared in the literature are second-order (or Diewert-flexible) forms. Technically, this means that if g(x) is to be approximated by g(xIO), then at any given point xo there is a corresponding choice of parameters 01 such that

Noise on Residential Power Distribution Circuits

Abstract: This paper presents electromagnetic noise measurements on power distribution circuits in the frequency range of 5-100 kHz. Since this noise is due primarily to appliances such as universal motors, light dimmers, television receivers, and certain switching power supplies located on the secondary side of the distribution transformer, the noise varies dramatically with time as these appliances are turned on and off. Measurements of the noise inserted into the distribution circuit by several representative appliances are presented. The noise measurement technique itself, as well as the resulting measurements, are described. Background noise which is present in the absence of such appliances was also measured. These noise measurements are important for the design of communications systems, such as distribution-line carrier, which operate in the 5-20 kHz region and use the distribution line as a communications medium.

Colony composition, protozoan transfer and some life history characteristics of the woodroach Cryptocercus punctulatus Scudder (Dictyoptera: Cryptocercidae)

Abstract: Adult pairs of the woodroach Cryptocercus punctulatus were reported to be incapable of founding colonies independently because the presence of a recently molted juvenile was required to transfer encysted symbiotic gut protozoa to newly hatched roaches. Field and laboratory evidence presented here shows that adult pairs of C. punctulatus do found colonies and that juveniles are generally not present to provide neonates with protozoan cysts. Newly hatched nymphs acquire their intestinal symbionts by feeding on the anal fluids of the adult roaches, i.e., by proctodeal trophallaxis. Conditions other than a symbiotic association with protozoans may have contributed to the evolution of eusociality in termites (Isoptera).

Patterns, Mechanisms and Approaches to the Study of Migrations of Estuarine-Dependent Fish Larvae and Juveniles

Abstract: Five species (<10%) contribute over 85% of the annual commercial catch of finfish off North Carolina. All five spawn in winter near the Gulf Stream and migrate about 100 km to major inlets in the barrier islands and then up to another 100 km to juvenile estuarine nursery areas. The vertical distribution of pelagic larvae of menhaden (Brevoortia tyrannus) differs significantly from that of more benthic-oriented larvae such as spot (Leiostomus xanthurus), croaker (Micropogonias undulatus) and flounder (Paralichthys lethostigma and P. dentatus). Analysis of the shelf current regime suggests that differences in vertical distribution and season will subject larvae to markedly different currents, and therefore, different mechanisms for migration are required. Calculations of water movements using Ekman’s original transport equations are probably wrong in relatively shallow shelf waters subject to cross-shelf winds and density currents. Major differences probably exist, therefore, between the pelagic larvae of the west coast (e.g. Pacific sardine, Sardinops sagax) and estuarine dependent species of the east coast—both with respect to the importance of microscale processes (e.g. food patchiness) and drift. Predator avoidance is likely to be a more important determinant of migration pattern than has been suggested to date. Problems of determining migration vectors and mechanisms from highly variable larval and juvenile fish distributions are discussed. A research strategy dealing with the above is outlined, and testable implications of hypotheses are presented.

Effects of Water Stress on Photosynthesis and Carbon Partitioning in Soybean (Glycine max [L.] Merr.) Plants Grown in the Field at Different CO2 Levels

Abstract: The effects of water stress and CO2 enrichment on photosynthesis, assimilate export, and sucrose-P synthase activity were examined in field grown soybean plants. In general, leaves of plants grown in CO2-enriched atmospheres (300 microliters per liter above unenriched control, which was 349 ± 12 microliters per liter between 0500 and 1900 hours EST over the entire season) had higher carbon exchange rates (CER) compared to plants grown at ambient CO2, but similar rates of export and similar activities of sucrose-P synthase. On most sample dates, essentially all of the extra carbon fixed as a result of CO2 enrichment was partitioned into starch. CO2-enriched plants had lower transpiration rates and therefore had a higher water use efficiency (milligrams CO2 fixed per gram H2O transpired) per unit leaf area compared to nonenriched plants. Water stress reduced CER in nonenriched plants to a greater extent than in CO2-enriched plants. As CER declined, stomatal resistance increased, but this was not the primary cause of the decrease in assimilation because internal CO2 concentration remained relatively constant. Export of assimilates was less affected by water stress than was CER. When CERs were low as a result of the imposed stress, export was supported by mobilization of reserves (mainly starch). Export rate and leaf sucrose concentration were related in a curvilinear manner. When sucrose concentration was above about 12 milligrams per square decimeter, obtained with nonstressed plants at high CO2, there was no significant increase in export rate. Assimilate export rate was also correlated positively with SPS activity and the quantitative relationship varied with CER. Thus, export rate was a function of both CER and carbon partitioning.

Career Decision Scale

Abstract: (1984). Career Decision Scale. Measurement and Evaluation in Counseling and Development: Vol. 17, No. 2, pp. 98-100.