Showing papers by "North Carolina State University published in 1977"

Dimensions, Birefringences, and Force-Elongation Behavior of Major and Minor Ampullate Silk Fibers from Orb-Web-Spinning Spiders—The Effects of Wetting on these Properties:

Abstract: The effects of wetting by water were determined on the dimensions, birefringences, and force-elongation behavior of major and minor ampullate silk fibers from Araneus diadematus Clerck, and major only from Araneus sericatus Clerck and Araneus gemma (McCook) (all family Araneidae). The values obtained at room conditions (RC), in the wetted, restrained (WR) and wetted, axially unrestrained (WU) states, the ratios of these, between states, are reported upon. The unexpected supercontraction of major ampullate fibers, WU, is contrasted with the stabile behavior of those from the minor ampullate gland systems. When dried from the WR state, both types appear to recover their RC properties. But when dried slack from the WU state, the major ampullate fibers undergo the “drawing” phenomenon typical of many man-made protofibers. The techniques required in order to secure data on these fragile (diameters, 0.6–6.0 μm) fibers, are described in some detail.

A computer analysis of heterojunction and graded composition solar cells

Abstract: The development and application of a variable composition solar cell computer analysis program is discussed, The basic device equations as used in the computer analysis are derived and the techniques used to model material parameter variations described. Finally, the results of the computer analysis of several Al x Ga 1-x As and GaAs 1-x P x solar cell structures are presented along with a discussion of the effects of interface states and various composition and doping profiles on maximum solar cell efficiency. Interface states are found to be responsible for a severe reduction in the efficiency of GaAs 1-x P x cells, but do not significantly affect the behavior of Al x Ga 1-x As cells. The depth of the p-n junction below the wide bandgap window layer is a critical factor in determining the loss of minority carriers to interface recombination at the heterojunction.

Excretion of dissolved organic carbon by eelgrass (Zostera marina) and its epiphytes1

Abstract: The release of dissolved organic carbon (DOC) by eelgrass (Zostera marina) and its epiphytic community was examined in a shallow estuarine system near Beaufort, North Carolina. Excretion by eelgrass alone, by epiphytes alone, and by heavily epiphytized eelgrass was determined by radiocarbon techniques using carbon 14. The percent of total photosynthate excreted was small in all cases: 0.9 percent for heavily colonized plants, 1.5 percent for Zostera alone, and 2.0 percent for the epiphytic community. The amount released by the eelgrass and epiphytes was proportional to the total amount of carbon fixed. Excretion rates in the dark were much lower than in the light. The rate of excretion increased after the plant underwent desiccation. The annual primary production and DOC excretion by phytoplankton, cordgrass (Spartina alterniflora), and the eelgrass community was estimated: 47 percent of the total annual primary production and 14 percent of the total excreted material was contributed by eelgrass and its epiphytes. Thus the eelgrass and epiphytes can play an important role in carbon cycling in estuarine systems.

Quadratic analyses of reciprocal crosses.

Abstract: Three different models, a two-way factorial model for familiarity, an orthogonalizing transform of this model to a diallel model, and a bio model more representative of the biological situation, are interrelated in terms of their components of variance and covariance. It is clarified that there are five components that can be reckoned with in the analysis of reciprocal crosses, including distinct maternal and paternal variances. Estimation of the components and tests of hypotheses concerning them are outlined for two types of mating designs with reciprocals. One deisgn involves a factorial mating design between two distinct sets of parents or parental lines and the other a diallel of all crosses from a single set of parents or parental lines. Both designs provide the same types of information and similar tests of hypotheses. At least some parts of the analyses corresponding to the factorial model are required to separate the maternal and paternal variances. A least squares partitioning of the sums of squares according to the diallel model, but with expectations expressed in terms of the bio model, provides most of the tests of hypotheses of interest. Worked examples are given.

Inactivation of Representative Species of Entomopathogenic Viruses, a Bacterium, Fungus, and Protozoan by an Ultraviolet Light Source

Abstract: Four entomopathogenic viruses and one each of an entomopathogenic bacterium, fungus, and protozoan were inactivated when exposed to ultraviolet light; the half-life was less than 4 h in every instance. Relative ranking in stability of the entomopathogens was as follows: B. thuringiensis Berliner > Nomuraea rileyi (Farlow) Samson > entomopox Virus > nucleopolyhedrosis virus = cytoplasmic polyhedrosis virus > Vairimorpha (= Nosema ) necatrix (Kramer) > granulosis virus.

Individual versus Social Optimization in Exponential Congestion Systems

Abstract: We consider a stochastic congestion system modeled as a birth-death process. Customers arrive from a Poisson process. The departure rate when i customers are in the system is non-decreasing, concave, and bounded above in i. The cost structure consists of a linear holding cost and a random reward received when a customer enters the system. The system can be controlled by deciding which customers will enter. Our main result extending those of Naor, Yechiali, and Knudsen is that, with or without discounting and for a finite or infinite time horizon, the individually optimal rule calls for the customer to enter the system whenever the socially optimal rule does. We also study the properties of the optimal congestion toll, which induces customers acting in their own interest to follow a socially optimal rule.

Inversion Clines in Populations of DROSOPHILA MELANOGASTER

Abstract: Twenty different natural populations of Drosophila melanogaster were sampled to determine the frequencies of inversions. Based on their frequencies and geographical distributions, the inversions could be classified as follows: (1) Common cosmopolitan inversions that are present in many populations in frequencies exceeding five percent and that may exhibit frequency clines over large geographical regions; (2) Rare cosmopolitan inversions that occur throughout the species range but usually at frequencies below five percent and that may be absent in many populations; (3) Recurrent endemic inversions that are found in several adjacent populations in frequencies usually not exceeding one or two percent; and (4) Unique endemic inversions that are found only among the progeny of a single individual and that may represent one aspect of the syndrome termed "hybrid dysgenesis". Four common cosmopolitan inversions that exhibit highly significant clines in populations in the eastern United States are In(2L)t, In(2R)NS, In(3L)P and In(3R)P.

Digenic descent measures for finite populations

Abstract: The development of a set of two-locus descent measures is reviewed The three digenic measures, inbreeding coefficient and parental and recombinant descent coefficients, are considered in detail The derivations of these three in pedigrees, fixed mating systems, and random mating in monoecious or dioecious populations are given General expressions for digenic frequencies and disequilibria functions at any time are found by applying the three digenic descent measures to two types of initial populations The final or equilibrium status of the population is also given As the inbreeding coefficient is the same as the recombinant descent coefficient in the case of complete linkage, avoidance or promotion of early inbreeding has similar effects on the two coefficients Estimable components of linkage disequilibrium and other measures of association within and among populations are elaborated

Circadian organization in lizards: the role of the pineal organ.

Abstract: After pinealectomy, the iguanid lizard Sceloporus olivaceus exhibits a "splitting" of the circadian activity rhythm into two components, marked changes in the period of the rhythm, or arrhythmicity. These effects are consistent with either of two hypotheses: (i) The pineal organ is a coupling device between circadian oscillators in a multioscillator system, or (ii) the pineal organ is itself a master oscillator, which entrains other circadian oscillators and imposes its frequency upon them.

A reactance theorem

Abstract: A formula is derived for the frequency derivative of the input reactance of any linear, passive, time-invariant electromagnetic system. It consists of five terms, each of which is identifiable uniquely with one of the following five physical attributes of the system: time-average stored magnetic energy, time-average stored electric energy, radiation, dispersion by the medium, and dissipation by the medium.

Tritium Diffusion in A12O3 and BeO

Abstract: Tritium diffusion in aluminum and beryllium oxides was studied by recoiling tritium into specimens and measuring the time rate of tritium release during postirradiation heating. Results were consistent with classical diffusion solutions and gave single values for the diffusion activation energy over the temperature range of measurement for single-crystal, sintered, and powdered specimens. Varying amounts of tritium were released as tritiated water even after attempts to remove most of the water absorbed by the specimens. Condensable amounts of tritium ranged from approximately 20% for single-crystal specimens to as high as 90% for some powders. Alumina containing 0.2% MgO gave tritium diffusion coefficients 4 to 5 orders of magnitude higher than those for undoped Al/sub 2/O/sub 3/, implying a significant impurity effect on tritium diffusion. Measured diffusion coefficients were many orders of magnitude lower than hydrogen diffusion coefficients in metals. When a simple equilibrium permeation model was used which neglected tritium partition effects at interfaces and enhanced diffusion along grain boundaries, it was shown that thin coatings of beryllium or aluminum oxides on metal substrates could markedly reduce tritium permeation rates through metals. The present results may be applied in the future to fusion reactors where tritium inventories will be highmore » and tritium diffusion within the blanket region undesirable.« less

The basis of color in muscle foods.

Abstract: The basis of color in heme‐pigmented muscle food resides in the physicochemical/electromagnetic properties of the intracellular oxygen‐carrying heme protein, myoglobin. This critical review of pertinent recent literature explores and attempts to interrelate properties of this color‐imparting molecule in the context of the underlying nature of red meat color and factors promoting stability and instability.

Pheromonally Induced Sexual Maturation in Females: Regulation by the Social Environment of the Male

Abstract: Social subordination, which suppresses gonadal function in juvenile and adult male house mice, also suppresses the activity of an androgen-dependent urinary pheromone that accelerates the rate of sexual maturation in juvenile females. Pheromone production may also be suppressed by the presence of pregnant or lactating females. This suggests that the social environment may influence the fertility of population females by altering urinary pheromone activity in the male.

Voluntary Association Membership Trends and the Family Life Cycle

Abstract: Using a role perspective, expectations are derived about changes in voluntary association membership levels across the family life cycle. The expected curvilinear relationship was found in national survey data from 1967 to 1974. The relationship remained even with race, sex, and education levels held constant in a log-linear analysis of multiway contingency tables. The curvilinear pattern differed somewhat between the two samples, but the general pattern held regardless of the type of organization. Slight increases in membership rates were found over time, suggesting a continuance of trends noted in samples from previous years. An individual's position in the family life cycle affects his or her involvement in voluntary associations. Family role obligations at each life cycle stage can be conceptualized as promoting or inhibiting extra-familial activities. The expected changes required by marriage, parenthood, retirement, and marital dissolution can be systematically linked to expectations for involvement in limited-goal secondary associations. The result is an hypothesized curvilinear relationship between family life cycle and voluntary association membership. We test this hypothesis with national survey data, also noting the trends over time. Family Roles and the Life Cycle Most persons must account to their families for the time, energy, and money they spend on extra-familial activities. The family is a "role budget center" (Goode, 493) which influences people's attempts to manage their *Data used in the present article were provided by the Inter-University Consortium for Political Research and the Roper Public Opinion Research Center and were originally collected by the National Opinion Research Center, with support of the National Science Foundation for the 1974 General Social Survey. For their suggestions, and especially their encouragement, we are grateful to James R. Wood, Marilyn Lester, James A. Davis and Bruce Stephenson. None of them bears any onus for errors committed by the authors in analyzing and interpreting the data.

The Races of maize iv: tentative grouping of 219 Latin American races

Abstract: Using principal component and cluster analyses of 20 ear characters for 219 Latin American races and subraces of maize, 14 groups of races are delimited. The relationships among these groups are indicated, and some subdivisions of the 14 racial groups are described. Only two of the 14 groups of races have been widely used in breeding; several groups have only been slightly studied and a number of their component races verge upon extinction. There is a very small, but perhaps highly significant, amount of overlap between the groups to which the Mexican and indigenous South American races belong.

Performance limitations of silicon solar cells

Abstract: This paper discusses the performance limitations of silicon solar cells which have been identified and investigated using a detailed numerical analysis of solar cell operation. Efficiency limitations are discussed as related to doping densities, minority carrier lifetimes, widths of solar cell regions, surface recombination, antireflecting layers, and ohmic contact stripes. Areas in which improvements can be expected in performance are identified and discussed.

Genetic control and racial variation of beta-glucosidase isozymes in maize (Zea mays L.)

Abstract: β-Glucosidase (β-D-glucoside glucohydrolase, EC 32121, β-Glu) isozyme variants were studied in a large number of inbred lines, crosses, and races of maize (Zea mays L) The pattern of Mendelian inheritance demonstrated for β-GLU variants indicated that they are under nuclear gene control Twenty-two allelic forms at a single locus were identified in the materials studied by starch gel electrophoresis Genetic data indicate that β-GLU in maize is functionally a dimer Variation of β-GLU isozymes in 51 racial collections of maize from Mexico showed little correlation with morphological or geographical data In 39 collections from Central America, variation patterns appeared to have some association with altitude