Showing papers by "Michigan State University published in 1983"

An Experimental Test of the Effects of Predation Risk on Habitat Use in Fish

Abstract: We present an experiment designed to test the hypothesis that fish respond to both relative predation risk and habitat profitability in choosing habitats in which to feed. Identical populations of three size—classes of bluegill sunfish (Lepomis macrochirus) were stocked on both sides of a divided pond (29 m in diameter), and eight piscivorous largemouth bass (Micropterus salmoides) were introduced to one side. Sizes of both species were chosen such that the small class of bluegills was very vulnerable to the bass, whereas the largest class was invulnerable to bass predation. We then compared mortality, habitat use, and growth of each size—class in the presence and absence of the bass. Only the small size—class suffered significant mortality from the bass (each bass consumed on average about one small bluegill every 3.8 d); the two larger size—classes exhibited similar mortality rates on both sides of the pond. In the absence of the bass, we found that habitat use of all size—classes was similar and that the pattern of habitat use maximized foraging return rates (Werner et al. 1983). In the presence of the bass the two larger size—classes chose habitats to maximize return rates, but the small size—class obtained a greater fraction of its diet from the vegetation habitat, where foraging return rates were only one—third of those in the more open habitats. The small size—class further exhibited a significant depression in individual growth in the presence of the bass; the growth increment during the experiment was 27% less than that for small bluegills in the absence of the bass. Because of the reduced utilization of more open habitats by the small fish in the presence of bass, resources in these habitats were released to the larger size—classes, which showed greater growth in the presence of the bass than in its absence. We develop methods to predict the additional mortality expected on a cohort due to a reduction in growth rate (because individuals are spending a longer time in vunerable sizes), and discuss and potential for predation risk to enforce size—class segregation, which leads de facto to resource partitioning.

Markov Random Field Texture Models

Abstract: We consider a texture to be a stochastic, possibly periodic, two-dimensional image field. A texture model is a mathematical procedure capable of producing and describing a textured image. We explore the use of Markov random fields as texture models. The binomial model, where each point in the texture has a binomial distribution with parameter controlled by its neighbors and ``number of tries'' equal to the number of gray levels, was taken to be the basic model for the analysis. A method of generating samples from the binomial model is given, followed by a theoretical and practical analysis of the method's convergence. Examples show how the parameters of the Markov random field control the strength and direction of the clustering in the image. The power of the binomial model to produce blurry, sharp, line-like, and blob-like textures is demonstrated. Natural texture samples were digitized and their parameters were estimated under the Markov random field model. A hypothesis test was used for an objective assessment of goodness-of-fit under the Markov random field model. Overall, microtextures fit the model well. The estimated parameters of the natural textures were used as input to the generation procedure. The synthetic microtextures closely resembled their real counterparts, while the regular and inhomogeneous textures did not.

Intercalated Clay Catalysts

Abstract: Recent advances in the intercalation of metal complex cations in smectite clay minerals are leading to the development of new classes of selective heterogeneous catalysts. The selectivity of both metal-catalyzed and proton-catalyzed chemical conversions in clay intercalates can often be regulated by controlling surface chemical equilibria, interlamellar swelling, or reactant pair proximity in the interlayer regions. Also, the intercalation of polynuclear hydroxy metal cations and metal cluster cations in smectites affords new pillared clay catalysts with pore sizes that can be made larger than those of conventional zeolite catalysts.

Classroom Organization and Management.

Abstract: tunately, many of the theory-based ideas were incorrect or impractical for classroom use, and the experience-based advice was unsystematic and often contradictory. As a result, teachers were often left with the impression that classroom management is purely an art rather than partly an applied science and that "teachers have to find out what works best for them." Classroom research conducted in the

The effects of mental practice on motor skill learning and performance: A meta-analysis.

Abstract: A longstanding research question in the sport psychology literature has been whether a given amount of mental practice prior to performing a motor skill will enhance one's subsequent performance. The research literature, however, has not provided any clear-cut answers to this question and this has prompted the present, more comprehensive review of existing research using the meta-analytic strategy proposed by Glass (1977). From the 60 studies yielding 146 effect sizes the overall average effect size was .48, which suggests, as did Richardson (1967a), that mentally practicing a motor skill influences performance somewhat better than no practice at all. Effect sizes were also compared on a number of variables thought to moderate the effects of mental practice. Results from these comparisons indicated that studies employing cognitive tasks had larger average effect sizes than motor or strength tasks and that published studies had larger average effect sizes than unpublished studies. These findings are discus...

What is the Sapir-Whorf hypothesis?

Abstract: Experimental evidence from the domain of color perception is presented for a version of the Sapir-Whorf hypothesis that is considerably weaker than the version usually proposed.

Correcting for Bias in Log-Transformed Allometric Equations

Abstract: mals: their productivity and population dynamics, IBP. Volume 5. Cambridge University Press, London, England. Mahmud, F. S. 1980. Alary polymorphism in the small brown planthopper Laodelphax striatellus (Homoptera: Delphacidae). Entomologia Experimentalis et Applicata 28: 47-53. McCoy, E. D., and J. R. Rey. 1981. Alary polymorphism among the salt marsh Delphacidae (Homoptera: Fulgoroidea) of northwest Florida. Ecological Entomology 6:285291. Rey, J. R. 1981. Ecological biogeography of arthropods on Spartina islands in northwest Florida. Ecological Monographs 51:237-265. Stiling, P. D., and D. R. Strong. 1982. The parasitoids of the planthopper Prokelisia marginate (Homoptera: Delphacidae). Florida Entomologist 65:191-192. Varley, G. C., G. R. Gradwell, and M. P. Hassell. 1973. Insect population ecology. Blackwell, Oxford, England. Watt, A. D., and A. F. G. Dixon. 1981. The role of cereal growth stages and crowding in the induction of alatae in Sitobion a'enae and its consequences for population growth. Ecological Entomology 6:441-447.

Dispensability of member effort and group motivation losses: Free-rider effects

Abstract: Three experiments tested the hypothesis that group members exert less effort as the perceived dispensability of their efforts for group success increases. The resultant motivation losses were termed "free-rider effects." In Exp I, 189 undergraduates of high or low ability performed in 2-, 4-, or 8-person groups at tasks with additive, conjunctive, or disjunctive demands. As predicted, member ability had opposite effects on effort under disjunctive and conjunctive task demands. The failure to obtain a relationship between group size and member effort in Exp I was attributed to a procedural artifact eliminated in Exp II (73 Ss). As predicted, as groups performing conjunctive and disjunctive tasks increased in size, member motivation declined. This was not a social loafing effect; group members were fully identifiable at every group size. Exp III (108 Ss) explored the role that performance feedback plays in informing group members of the dispensability of their efforts and encouraging free riding. Results are generally consistent with those of Exps I and II.

Motivation losses in small groups: a social dilemma analysis

Abstract: Theory developed to account for behavior in social dilemmas—situations in which - the rational pursuit of self-interest can lead to collective disaster—was applied to the analysis of group motivation losses. Two group motivation loss effects demonstrated in previous research, the social-loafing effect and the free-rider effect, were shown to follow from social dilemma theories. An experiment was performed to empirically demonstrate a third motivation loss effect, termed the sucker effect. It was hypothesized that group members would reduce their efforts if they had a capable partner.who free rode on their efforts, that is, who was capable of contributing to the group but would not. This prediction was confirmed. The effect was particularly strong in males. Potential remedies for such motivation losses were discussed.

Denitrification: ecological niches, competition and survival

Abstract: Organisms with the denitrification capacity are widely distributed and in high density in nature. It is not well understood why they are so successful. A survey of denitrifying enzyme content of various habitats is presented which indicates a role of carbon and oxygen, but not nitrate, in affecting denitrifier populations. It is suggested that organic carbon is more important than oxygen status in determining denitrifying enzyme content of habitats. In low oxygen environments, denitrifiers compete with organisms that dissimilate nitrate to ammonium, a process which conserves nitrogen. The energetic and kinetic parameters that affect this competition are evaluated. The latter is examined using Michaelis-Menten theoretical models by varying Vmax, Km, and So (substrate concentration) for the two competing populations. The outcome predicted by these models is presented and discussed in relation to previous data on population densities and Km values for representatives of these competing groups. These models suggest the conditions required to achieve changes in partitioning between the two fates of nitrate. These considerations are important if one is to be able to evaluate and successfully “manage” the fate of nitrate in any habitat.

Sulfate Reducers Can Outcompete Methanogens at Freshwater Sulfate Concentrations

Abstract: Acetate and hydrogen metabolism by sulfate reducers and methanogens in the profundal sediments of an oligotrophic lake were examined. Inhibition of sulfate reduction with molybdate stimulated methane production from both hydrogen and acetate. Molybdate did not stimulate methane production in sediments that were preincubated to deplete the sulfate pool. Sulfate reduction accounted for 30 to 81% of the total of terminal metabolism proceeding through sulfate reduction and methane production in Eckman grab samples of surface sediments. The ability of sulfate reducers to effectively compete with methanogens for acetate was related to the sulfate reducers' lower half-saturation constant for acetate metabolism at in situ sulfate concentrations. Processes other than sulfate reduction and methanogenesis consumed hydrogen at elevated hydrogen partial pressures and prevented a kinetic analysis of hydrogen uptake by sulfate reducers and methanogens. The demonstration that sulfate reducers can successfully compete with methanogens for hydrogen and acetate in sediments at in situ sulfate concentrations of 60 to 105 μM extends the known range of sediment habitats in which sulfate reduction can be a dominant terminal process.

Molecular Basis of Herbicide Resistance in Amaranthus hybridus.

Abstract: Resistance of different species of weeds to s-triazines, a commonly used class of herbicides, has been shown to involve a change in the binding affinity of the herbicide to a chloroplast polypeptide of 32,000 daltons. A single amino acid difference in this 32,000-dalton protein appears to be responsible for resistance to the herbicide in Amaranthus hybridus.

Experimental Tests of Optimal Habitat Use in Fish: The Role of Relative Habitat Profitability

Abstract: Utilizing optimal foraging theory and laboratory estimates of foraging costs, we predict the choice of foods and use of habitats by fish in the field. These predictions are tested with the bluegill sunfish (Lepomis macrochirus) foraging in three habitats (open water, sediments, and vege- tation) in a pond. Relations describing prey encounter rates in each habitat as a function of prey size, prey density, and fish size were derived from laboratory experiments. These relations permitted us to estimate prey encounter rates based on weekly prey samples in each habitat of the pond. We then determined the optimal diet and profitability (net energy return) for each habitat through time. Predictions of optimal diet exhibited good qualitative correspondence to the actual diet of the fish in the open water and vegetation, although we consistently predicted a slightly narrower diet than the fish were choosing. The model correctly predicted the magnitude of the change in size selection on Daphnia pulex with fish size and with decline in prey density. Predictions of optimal diet in the sediments were considerably in error apparently due to a tendency for late-instar midges to burrow deep in the sediments, thereby becoming unavailable to the fish. In this case habitat profitabilities were computed simply on the basis of the actual observed diet. Predictions of optimal habitat use, i.e., when the fish should switch habitats to maximize feeding rates, showed striking correspondence to the actual habitat use of the fish; the bluegills switched from feeding in the open water column to feeding from the sediments within a few days of our predictions. The actual habitat use pattern differs dramatically from a null model of random habitat use. We indicate how this approach may be useful in studying intra- and interspecific exploitative interactions.

Damping of nuclear excitations

Abstract: The authors review the theory and the empirical evidence of damping of simple nuclear excitations. The excitations considered are the particle states and vibrational states. The particle damping phenomena include the fragmentation of single-particle levels, the systematics of neutron strength functions, and the optical absorption of elastic scattering. Information on the known collective vibrational states is summarized and compared with theory. A theoretical model that has found considerable success is based on a damping mechanism in which the simple excitations mix with the surface vibrations. This implies that the surface damping dominates for excitation energies below about 15 MeV. There is a close relation between the single-particle damping and the damping of collective vibrations. However, the vibrational damping is strongly suppressed by the coherence between the particle and the hole. While the model reproduces many of the observed features of the data rather well, it tends to underpredict the spreading width by as much as a factor of 2. Thus other degrees of freedom, not well understood at present, may play a role in the damping.

Recent Developments Concerning Saint-Venant's Principle

Abstract: This chapter provides an overview of the recent developments concerning Saint-Venant's principle The task of determining, within the framework of the linear theory of elasticity, the stresses and displacements in an elastic cylinder in equilibrium, under the action of loads that arise solely from tractions applied to its plane ends has come to be called Saint- Venant's problem Saint-Venant's construction does not permit the arbitrary preassignment of the point-by-point variation of the end tractions giving rise to these forces and moments; indeed, this variation is essentially determined as a consequence of the special assumptions made in connection with his so-called semi-inverse procedure The early work of Saint-Venant and Boussinesq furnished the seeds from which grew a large number of more general assertions, most referring to elastic solids of arbitrary shape and many being rather imprecise, concerning the effect on stresses within the body of replacing the tractions acting over a portion of its surface by statically equivalent ones Such propositions usually went by the name of Saint-Venunt's principle, despite the fact that Saint-Venant's original conjecture was intended to apply only to cylinders This chapter discusses in detail about flow in a cylinder, a representation for the exact solution, and energy decay for other linear elliptic second-order problem Linear elastostatic problems are also stated in the chapter

Equivalence of competitors in plant communities: a null hypothesis and a field experimental approach.

Abstract: One of the underlying assumptions of both theoretical and empirical community ecology is that the processes determining community composition and abundance of species are interactions specific to particular pairs of species. However, we argue that, in sessile plants at least, competitive interactions are not usually species-specific and that there exists a large degree of equivalence of the effect of species of similar growth form on the ability of any particular species to establish within a community. This null hypothesis of equivalence of competitive effects is based on three characteristics of plants: homogeneity of resource requirements among autotrophs; low encounter probabilities between individuals of any particular species pair; and the predominance of size asymmetries between competing individuals (e.g., seedling-adult interactions.) We present an experimental design to quantify competitive interactions among plant species under field conditions and therefore enable statistical comparisons of competitive abilities among species. The competitive effect of one "neighbor" species on one "target" species is measured as the slope of a regression of performance of target individuals on biomass (or other measure of amount) of its immediate neighbors. Use of the design to test for equivalence of competitive effects and other advantages are described.

Social Impact and Social Preference as Determinants of Children's Peer Group Status

Abstract: Three sociometric procedures, which utilize a two-dimensional social-impact and social-preference framework, were evaluated on three independent samples of fourthand fifth-grade children (N = 334, 173, 89). The stability and distribution of classification, the relationship between dimensions, the validation of dimensions, and the validation of classificatio n groups were considered. Overall, the Peery (1979) method appeared most problematic, due to both conceptual and practical drawbacks. The Coie, Dodge, and Coppotelli (1982) procedure was found to have nonexhaustive groups and had the potential of misrepresenting children's social networks when standardized scores were used. Furthermore, little support was found for the proposed controversial group in the Coie et al. classification system. An alternative two-dimensional sociometric model based on probability theory was proposed and was found to have excellent performance characteristics while still providing a constant frame of reference across social networks. The social reputational correlates of the impact and preference dimensions and the sociometric groups proposed by each model were also investigated. Although social impact and social preference are found to be reliable and valid determinants of peer group status, the need for alternative indicators of children's social standing in the peer group is discussed. The current empirical interest in children's friendships and peer relations has resulted in the increased use of sociometric classification schemes to categorize children both for nomothetic research and for clinical interventions. The further development of sociometric procedures and their appropriate use are important concerns for developmental and clinical psychologists because of the association between children's peer relations and subse

Magnetism in solid He-3

Abstract: The theory of magnetism in solid $^{3}\mathrm{He}$ is reviewed with emphasis on the multiple-spin-exchange theory of the magnetic interaction. Critical experiments are discussed briefly, and the most reliable present values for various quantities are chosen. Various theories of $^{3}\mathrm{He}$ magnetism are considered, with the conclusion that multiple particle exchange is the most likely mechanism. The microscopic theory of exchange is presented mainly from the standpoint of tunneling ducts. The spin Hamiltonian which results from two-, three-, and four-particle ring exchange is derived and studied in the high-temperature limit, in mean-field approximation, and with spin waves. Two reasonable parameter sets are selected which fit the experimental data, with the conclusion that the exchanges are mainly three- and four-particle rings. A discussion is given of remaining problems together with some conjectures.

Anaerobic biodegradation of phenolic compounds in digested sludge.

Abstract: We examined the anaerobic degradation of phenol and the ortho, meta, and para isomers of chlorophenol, methoxyphenol, methylphenol (cresol), and nitrophenol in anaerobic sewage sludge diluted to 10% in a mineral salts medium. Of the 12 monosubstituted phenols studied, only p-chlorophenol and o-cresol were not significantly degraded during an 8-week incubation period. The phenol compounds degraded and the time required for complete substrate disappearance (in weeks) were: phenol (2), o-chlorophenol (3), m-chlorophenol (7), o-methoxyphenol (2), m- and p-methoxyphenol (1), m-cresol (7), p-cresol (3), and o-, m-, and p-nitrophenol (1). Complete mineralization of phenol, o-chlorophenol, m-cresol, p-cresol, o-nitrophenol, p-nitrophenol, and o-, m-, and p-methoxyphenol was observed. In general, the presence of Cl and NO2 groups on phenols inhibited methane production. Elimination or transformation of these substituents was accompanied by increased methane production, o-Chlorophenol was metabolized to phenol, which indicated that dechlorination was the initial degradation step. The methoxyphenols were transformed to the corresponding dihydroxybenzene compounds, which were subsequently mineralized.

Exploitation of allelopathy for weed control in annual and perennial cropping systems.

Abstract: A variety of crops, cultivars, and accessions have been evaluated over the past six years for superior capability to suppress weed growth. The most successful of these approaches has been to grow cover crops of rye (Secale cereale), wheat (Triticum aestivum), sorghum (Sorghum bicolor), or barley (Hordeum vulgare) to a height of 40–50 cm, desiccate the crops by contact herbicides or freezing, and allow their residues to remain on the soil surface. Often, up to 95% control of important agroecosystem weed species was obtained for a 30- to 60-day period following desiccation of the cover crop. The plant residues on the soil surface exhibit numerous physical and chemical attributes that contribute to weed suppression. Physical aspects include shading and reduced soil temperatures which were similarly achieved using poplar (Populus) excelsior as a control mulch. Chemical aspects apparently include direct release of toxins, as well as production of phytotoxic microbial products. Numerous chemicals appear to work in concert or in an additive or synergistic manner to reduce weed germination and growth.

Bureaucrats, Legislators, and the Size of Government

Abstract: Some recent theories have blamed the growth of government on budget-maximizing bureaucrats who are assumedly capable of imposing their most preferred budget-output combination on legislatures, subject to cost and demand constraints. However, theoretical examination of the range of bargaining outcomes that might occur between bureau and legislature shows that budget-maximizing behavior does not necessarily lead to super-optimal levels of production, nor do the suggested reforms of competition and privatization necessarily improve the situation. In this bargaining model, the central determinants of governmental growth are not budget-maximizing bureaucrats, but the legislature's decisions regarding mode of oversight and form of internal organization.

The effects of size of opening in vegetation and litter cover on seedling establishment of goldenrods (Solidago spp.)

Abstract: We investigated the effects of size of opening in the vegetation and litter cover on seedling establishment of two species of goldenrods (Solidago spp.) in an abandoned field in southwestern Michigan, U.S.A. Seeds of S. canadensis and S. juncea were sown into clipped plots, ranging from 0 cm (control, unclipped) to 100 cm in diameter, with and without litter. Seedling emergence, survival and growth were followed for one year. Soil moisture was not significantly different among the opening sizes, but, within a size, tended to be lower when litter was removed. Light intensity at the soil surface was positively related to opening size early in the growing season, but later in the growing season reached a maximum in intermediate-sized openings and then leveled off.

Rye residues contribute weed suppression in no-tillage cropping systems.

Abstract: The use of allelopathic cover crops in reduced tillage cropping systems may provide an ecologically sound and environmentally safe management strategy for weed control. Growers often plant winter rye (Secale cereale L.) for increased soil organic matter and soil protection. Spring-planted living rye reduced weed biomass by 93% over plots without rye. Residues of fall-planted/spring-killed rye reduced total weed biomass over bare-ground controls. Rye residues also reduced total weed biomass by 63% when poplar excelsior was used as a control for the mulch effect, suggesting that allelopathy, in addition to the physical effects of the mulch, did contribute to weed control in these systems. In greenhouse studies, rye root leachates reduced tomato dry weight by 25–30%, which is additional evidence that rye is allelopathic to other plant species.

The Role of Ethylene in the Growth Response of Submerged Deep Water Rice

Abstract: We investigated the effect of partial submergence on internode elongation in a Bangladesh variety of floating or deep water rice (Oryza sativa L., cv. Habiganj Aman II). In plants which were at least 21 days old, 7 days of submergence led to a 3- to 5-fold increase in internodal length. During submergence, the ethylene concentration in the internodes increased from about 0.02 to 1 microliters per liter. Treatment of nonsubmerged plants with ethylene also stimulated internode elongation. When ethylene synthesis in partially submerged plants was blocked with aminooxyacetic acid and aminoethoxyvinylglycine, internode elongation was inhibited. This growth inhibition was reversed when ethylene biosynthesis was restored with 1-aminocyclopropane-1-carboxylic acid (ACC). Radio-labeling studies showed that ethylene in floating rice was synthesized from methionine via ACC. Internodal tissue from submerged plants had a much higher capacity to form ethylene than did internodal tissue from nonsubmerged plants. This increase in ethylene synthesis appeared to be due to enhanced ACC formation rather than to increased conversion of ACC to ethylene. Our results indicate that ethylene produced during submergence is required for the stimulation of growth in submerged floating rice plants.