Showing papers by "Iowa State University published in 1994"

Review of particle properties.

Abstract: This biennial Review summarizes much of Particle Physics. Using data from previous editions, plus 2205 new measurements from 667 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. This edition features expanded coverage of CP violation in B mesons and of neutrino oscillations. For the first time we cover searches for evidence of extra dimensions (both in the particle listings and in a new review). Another new review is on Grand Unified Theories. A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review. All tables, listings, and reviews (and errata) are also available on the Particle Data Group website: http://pdg.lbl.gov.

Teaching by Principles: An Interactive Approach to Language Pedagogy

Abstract: Teaching by Principles: An Interactive Approach to Language Pedagogy, Third Edition, by H. Douglas Brown, is a widely acclaimed methodology text used in teacher education programs around the world. This user-friendly textbook offers a comprehensive survey of practical language teaching options, all firmly anchored in accepted principles of language learning and teaching. End-of-chapter exercises give readers opportunities to process material interactively. Suggested readings direct readers to important books and articles in the field.

Economic Stress, Coercive Family Process, and Developmental Problems of Adolescents

Abstract: We propose a model of family conflict and coercion that links economic stress in family life to adolescent symptoms of internalizing and externalizing emotions and behaviors. The 180 boys and 198 girls in the study were living in intact families in the rural Midwest, an area characterized by economic decline and uncertainty. Theoretical constructs in the model were measured using both trained observer and family member reports. These adolescents and their parents were interviewed each year for 3 years during the seventh, eighth, and ninth grades. Our theoretical model proposes that economic pressure experienced by parents increases parental dysphoria and marital conflict as well as conflicts between parents and children over money. High levels of spousal irritability, coupled with coercive exchanges over money matters, were expected to be associated with greater hostility in general by parents toward their children. These hostile/coercive exchanges were expected to increase the likelihood of adolescent emotional and behavioral problems. Overall, results were consistent with the proposed model. Moreover, the hypothesized processes applied equally well to the behavior of mothers and fathers, as well as sons and daughters.

Glutamate-mediated astrocyte-neuron signalling.

Abstract: NEUROTRANSMITTER released from neurons is known to signal to neighbouring neurons and glia1–3 Here we demonstrate an additional signalling pathway in which glutamate is released from astrocytes and causes an NMDA (N-methyl-d-aspartate) receptor-mediated increase in neuronal calcium. Internal calcium was elevated and glutamate release stimulated by application of the neuro-ligand bradykinin to cultured astrocytes. Elevation of astrocyte internal calcium was also sufficient to induce glutamate release. To determine whether this released glutamate signals to neurons, we studied astrocyte–neuron co-cultures. Bradykinin significantly increased calcium levels in neurons co-cultured with astrocytes, but not in solitary neurons. The glutamate receptor antagonists d-2-amino-5-phosphonopentanoic acid and d-glutamylglycine prevented bradykinin-induced neuronal calcium elevation. When single astrocytes were directly stimulated to increase internal calcium and release glutamate, calcium levels of adjacent neurons were increased; this increase could be blocked by d-glutamylglycine. Thus, astrocytes regulate neuronal calcium levels through the calcium-dependent release of glutamate.

Evidence for Chilling-Induced Oxidative Stress in Maize Seedlings and a Regulatory Role for Hydrogen Peroxide.

Abstract: We have taken advantage of an acclimation phenomenon in a chilling-sensitive maize inbred to investigate the molecular, biochemical, and physiological responses to chilling in preemergent maize seedlings. Three-day-old seedlings were exposed to 4[deg]C for 7 days and did not survive chilling stress unless they were preexposed to 14[deg]C for 3 days. cDNAs representing three chilling acclimation-responsive (CAR) genes were isolated by subtraction hybridization and differential screening and found to be differentially expressed during acclimation. Identification of one of these CAR genes as cat3, which encodes the mitochondrial catalase3 isozyme, led us to hypothesize that chilling imposes oxidative stress in the seedlings. Hydrogen peroxide levels were elevated during both acclimation and chilling of nonacclimated seedlings. Further molecular and biochemical analyses indicated that whereas superoxide dismutase activity was not affected, the levels of cat3 transcripts and the activities of catalase3 and guaiacol peroxidase were elevated in mesocotyls during acclimation. Accumulation of H2O2 following a short treatment with aminotriazole, a catalase inhibitor, indicated that catalase3 seems to be an important H2O2-scavenging enzyme in the seedlings. Control 3-day-old seedlings pretreated with H2O2 or menadione, a superoxide-generating compound, at 27[deg]C induced chilling tolerance. Both of these chemical treatments also increased cat3 transcripts and catalase3 and guaiacol peroxidase activities. We suggest that peroxide has dual effects at low temperatures. During acclimation, its early accumulation signals the production of antioxidant enzymes such as catalase3 and guaiacol peroxidase. At 4[deg]C, in nonacclimated seedlings, it accumulates to damaging levels in the tissues due to low levels of these, and perhaps other, antioxidant enzymes.

Trajectories of Stressful Life Events and Depressive Symptoms during Adolescence.

Abstract: This 4-year longitudinal study of 191 girls and 185 boys living in intact Camilies in the rural Midwest examines the trajectories of life events and depressive symptoms in adolescence. The trajectories of depressive symptoms differ between boys and girls. Compared with boys, girls experienced a greater number of depressive symptoms after age 13. Changes in uncontrollable events are associated with the increases in girls' but not boys' depressive symptoms. Latent growth curve analyses show that, over 4 years, (a) depressive symptoms for girls changed according to a curvilinear pattern that is associated with changes in stressful events; (b) the level of depressive symptoms is related to the level of life events for both boys and girls; and (c) change in depressive symptoms is significantly related to change in stressful events only for girls. Girls living with less supportive mothers are more vulnerable to negative life changes

Expectations as a Comparison Standard in Measuring Service Quality: An Assessment of a Reassessment:

Abstract: The author responds to issues raised by Parasuraman, Zeithaml, and Berry (1994) concerning his 1993 article that outlines theoretical and operational problems associated with the SERVQUAL model of ...

Anthology of Starch Granule Morphology by Scanning Electron Microscopy

Abstract: Scanning electron micrographs of the granules of 54 starches obtained from a wide variety of plant sources, consisting of roots and tubers, grains, maize, peas and beans, fruits and nuts, and small granule starches, are presented as a comparative study of their sizes and morphologies. All micrographs are presented at a magnification of 1500X with the addition of micrographs of 600X for the very large granules and micrographs of 10,000X for the very small granules.

Resolving Differences in Willingness to Pay and Willingness to Accept: Reply

Abstract: Gwendolyn C. Morrison (1997) raises a logical point regarding our experimental test of the divergence between willingness to pay (WTP) and willingness to accept (WTA) measures of economic value (Shogren et al., 1994). She argues that our design does not provide a true test of the existence of a fundamental endowment effect since we did not control for the potential of a pivoting indifference map (Daniel Kahneman et al., 1990). She concludes that even though our ev- idence shows that the mean WTP and WTA bids for market goods with close substitutes (e.g., candy bars and coffee mugs) converge after market experience, the endowment effect might still be alive and well, albeit at statisti- cally insignificant levels

Unit commitment literature synopsis

Abstract: Several optimization techniques have been applied to the solution of the thermal unit commitment problem. They range from heuristics such as complete enumeration to the more sophisticated ones such as Augmented LaGrangian. The heuristics have even reappeared as expert systems. The problem to solve is the optimal scheduling of generating units over a short-term horizon, typically 168 hours. This paper is an overview of the literature in the unit commitment field over the past twenty five years. >

Daidzein Is a More Bioavailable Soymilk Isoflavone than Is Genistein in Adult Women

Abstract: Soybean isoflavones are proposed to be anticarcinogenic, but their effective doses have not been established. To study the bioavailability of soybean isoflavones for humans, 12 young adult women received single doses of 0.7, 1.3 and 2.0 mg isoflavones/kg body wt in soybean milk as part of a liquid diet. Plasma, urine and fecal isoflavones were measured by reverse-phase HPLC. Average 24-h urinary recoveries of daidzein and genistein were approximately 21% and 9%, respectively, at all three doses. Urinary recovery of daidzein was significantly greater than that of genistein (P < 0.001). Total fecal excretion of isoflavones was only 1-2% of the ingested amount. Plasma total isoflavone concentration was significantly increased to 4.4 +/- 2.5 mumol/L at 6.5 h after a dose of 2.0 mg/kg. The plasma concentrations of daidzein and genisten were approximately equal. Twenty-four hours after dosing, both plasma and urine isoflavone concentrations were nearly nil. Although soybean milk isoflavones seem to be 85% degraded in the intestine, the bioavailability, especially of daidzein, may be sufficient to exert some health-protective effects.

A comparison of unit root test criteria

Abstract: During the past 15 years, the ordinary least squares estimator and the corresponding pivotal statistic have been widely used for testing the unit-root hypothesis in autoregressive processes. Recently, several new criteria, based on maximum likelihood estimators and weighted symmetric estimators, have been proposed. In this article, we describe several different test criteria. Results from a Monte Carlo study that compares the power of the different criteria indicate that the new tests are more powerful against the stationary alternative. Of the procedures studied, the weighted symmetric estimator and the unconditional maximum likelihood estimator provide the most powerful tests against the stationary alternative. As an illustration, the weekly series of one-month treasury-bill rates is analyzed.

Magnetization and transport currents in thin superconducting films.

Abstract: The critical-state behavior of an infinitely long type-II superconducting thin-film strip is theoretically analyzed for an arbitrary sequence of applied transport currents and perpendicular magnetic fields. Included are solutions for applied field only, transport current only, transport current applied to a sample initially in the remanent critical state, ac applied field, ac transport current, and simultaneously applied field and transport current. The results are compared side by side with corresponding solutions for the more famililar slab geometry; there are striking differences in behavior.

Gender Differences in Coping with Stress: When Stressor and Appraisals Do Not Differ

Abstract: In an attempt to control for the effects of event type on sex differences in coping, men and women responded to an identical achievement-related stressor under controlled laboratory conditions. Although men and women were similar in their cognitive appraisal of the situation, they nonetheless reported differences in preparatory coping. Women reported seeking social support and using emotion-focused coping to a greater extent than men, whereas men reported using relatively more problem-focused coping than women. The masculinity and femininity of respondents failed to moderate the relation between sex and coping. These results are inconsistent with a purely situational explanation of sex differences in coping but are consistent with the notion that men and women are socialized to cope with stress in different ways.

Perceived parental social support and academic achievement: An attachment theory perspective.

Abstract: The study tested the extent to which parental social support predicted college grade point average among undergraduate students. A sample of 418 undergraduates completed the Social Provisions Scale--Parent Form (C.E. Cutrona, 1989) and measures of family conflict and achievement orientation. American College Testing Assessment Program college entrance exam scores (ACT; American College Testing Program, 1986) and grade point average were obtained from the university registrar. Parental social support, especially reassurance of worth, predicted college grade point average when controlling for academic aptitude (ACT scores), family achievement orientation, and family conflict. Support from parents, but not from friends or romantic partners, significantly predicted grade point average. Results are interpreted in the context of adult attachment theory.

N Demand and the Regulation of Nitrate Uptake

Abstract: Uptake of nitrate by root cells followed by reduction and assimilation in plant tissues is the main route by which mineral N is converted into organic N by living organisms. Like photosynthesis, these are life-dependent processes that members of the animal kingdom are unable to perform for themselves. Nitrate and other mineral nutrients required for optimal plant growth and development frequently exist at relatively low concentrations in soil. To thrive on these dilute nutrients, plants have developed high-performance uptake systems in their root cells. To cope with wide variations in mineral concentrations in soil, plants have evolved mechanisms to regulate the activity of uptake systems so that net intake of a nutrient depends on the plant's need for this element rather than its concentration in the rooting medium. Indeed, uptake rates of most ions are seemingly controlled by specific demand-driven regulatory mechanisms. Such processes set the uptake rate of a given element to match the plant's current growth rate and developmental stage. Nitrate uptake is of special interest because nitrate is absorbed at a relatively high rate and because compounds that function as uptake sensors may have been identified. This paper focuses on whole-plant signaling processes involved in the regulation of nitrate uptake by N demand.

Crop residue effects on soil quality following 10-years of no-till corn☆

Abstract: Numerous biological, chemical, and physical indicators of soil quality have been suggested, but few have been evaluated using data from long-term field studies. Our objective was to evaluate several proposed soil quality indicators to determine effects of removing, doubling, or maintaining crop residues for 10 years in a no-till, continuous corn (Zea mays L.) production study. Soil aggregate characteristics, penetration resistance, bulk density, volumetric water content, earthworm populations, respiration, microbial biomass, ergosterol concentrations, and several soil-test parameters (pH, P, K, Ca, Mg, Total-N, Total-C, NH4-N, and NO3-N) were measured on samples collected from Rozetta and Palsgrove silt loam (fine-silty, mixed, mesic Typic Hapludalfs) soils. Soil aggregates from double residue treatments were more stable in water than those from normal and removal treatments. The double and normal residue treatments had higher total carbon concentrations and higher levels of microbial activity as measured by CO2 evolution. Ergosterol concentrations where crop residues were removed were 8 to 10 times lower suggesting this biochemical measurement of fungal biomass may be a sensitive soil quality indicator. Earthworm populations where crop residues had been removed for 10 years were significantly lower than in either normal or double residue treatments. Measures of force and energy required to crush soil aggregates were extremely variable and showed significant differences only for aggregate size. Several parameters were used to develop a soil quality index that gave ratings of 0.45, 0.68, or 0.86 for removal, normal, or double residue treatments, respectively. This study demonstrates a framework for soil quality evaluation and shows how crop residue management can affect this rating.

Melting line of aluminum from simulations of coexisting phases.

Abstract: We have performed simulations of coexisting liquid and solid phases of aluminum as an efficient way of mapping out the coexistence line. This technique is convenient, as it does not require complicated free-energy calculations for the different phases, but simply allows the system to equilibrate to a co-existence point. By altering the simulation volume and/or energy, a new coexistence point is found. The calculated method temperature is lower than previous results for the identical model; we suspect that this difference is due to the difficulty of calculating the free energy of the liquid phase, leading to inaccuracies in the previous work. A thorough examination of several different system sizes, from 1024 to 65 536 particles, indicates that the results are only weakly dependent upon the system size.

Fine-scale structure of pheromone plumes modulates upwind orientation of flying moths

Abstract: IN studies of moths flying upwind to a pheromone source, attention has focused on the influence on flight orientation of the composition1,2 and concentration3,4 of the chemical message, and of changes in the visual environment5,6 and in wind speeds7–9. The chemical signal must be intermittent for moths to fly upwind10–12, when they usually follow a zigzag track, the evident expression of a self-steered counterturning programme13,14. The integration of counterturning and optomotor anemotaxis allows insects to polarize the zigzags upwind in odour plumes10,15. Not all moths, however, zigzag along a plume16,17. It has been suggested that the propensity to zigzag or to fly straight upwind is related to the frequency at which males encounter pheromone filaments that comprise the plume, as well as the male's latency of response, characteristic for each moth species, to both the onset and loss of contact with filaments18. Here we present evidence that flight manoeuvres are dictated by the interactions of the male with individual odour pulses. We use Cadra cautella, the almond moth, to show how the structure of an odour plume19,20 can greatly modify the flight track. Males following either turbulent or mechanically pulsed plumes fly faster and straighter upwind, and locate sources more frequently than males following continuous narrow plumes. Males also fly straighter upwind to fast-pulsed plumes than to slow-pulsed plumes. The temporally modulated interplay between counterturning and optomotor anemotaxis that is induced by the plume's structure therefore seems to explain the manoeuvres and resultant flight track shapes made by C. cautella males when flying upwind towards a pheromone source.

Two routes to delinquency: differences between early and late starters in the impact of parenting and deviant peers*

Abstract: This paper tests hypotheses concerning differences in the determinants of involvement with the criminal justice system for adolescents who show early versus late onset of delinquency. Four waves of data collected on 177 adolescent boys living in small towns in the midwest were used to test the hypotheses. For late starters, quality of parenting predicted affiliation with deviant peers, which was associated in turn with criminal justice system involvement. Oppositional/defiant behavior was unrelated both to affiliation with deviant peers and to involvement with the criminal justice system. For early starters, on the other hand, quality of parenting predicted oppositional/defiant behavior. This behavior pattern predicted affiliation with deviant peers, which in turn predicted criminal justice system involvement. Further, we found evidence of an interaction effect for early starters: criminal justice system involvement was highest for those youths who both were oppositional/defiant and had deviant friends. Overall the findings support the idea of different routes to criminal behavior and arrest for early versus late starters.

Long-term tillage effects on soil quality

Abstract: Public interest in soil quality is increasing, but assessment is difficult because soil quality evaluations are often purpose- and site-specific. Our objective was to use a systems engineering methodology to evaluate soil quality with data collected following a long-term tillage study on continuous corn (Zea mays L.). Aggregate characteristics, penetration resistance, bulk density, volumetric water content, earthworm populations, respiration, microbial biomass, ergosterol concentrations, and several soil-test parameters (pH, P, K, Ca, Mg, Total-N, Total-C, NH4-N, and NO3-N) were measured on Orthic Luvisol soil samples collected from Rozetta and Palsgrove silt loam (fine-silty, mixed, mesic Typic Hapludalfs) soils. Plots managed using no-till practices for 12 years before samples were collected for this study had surface soil aggregates that were more stable in water and had higher total carbon, microbial activity, ergosterol concentrations, and earthworm populations than either the chisel or plow treatments. Selected parameters were combined in the proposed soil quality index and gave ratings of 0.48, 0.49, or 0.68 for plow, chisel, or no-till treatments, respectively. This indicated that long-term no-till management had improved soil quality. The prediction was supported by using a sprinkler infiltration study to measure the amount of soil loss from plots that had been managed using no-till or mold-board plow tillage. We conclude that no-till practices on these soils can improve soil quality and that the systems engineering methodology may be useful for developing a more comprehensive soil quality index that includes factors such as pesticide and leaching potentials.

Structural and magnetic studies of Sr2IrO4.

Abstract: The discovery of high-temperature superconductivity in doped copper oxides, which in their insulating forms are nearly ideal two-dimensional spin-1/2 Heisenberg antiferromagnets, has stimulated great interest in finding additional examples of such magnetic systems. We find that ${\mathrm{Sr}}_{2}$${\mathrm{IrO}}_{4}$, which has the ${\mathrm{K}}_{2}$${\mathrm{NiF}}_{4}$ structure and should have a 5${\mathit{d}}^{5}$ low-spin (S=1/2) electronic configuration, develops a ferromagnetic moment near 250 K. The small size of the remanent moment (${10}^{\mathrm{\ensuremath{-}}2}$${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$), and our structural studies, however, imply that this is weak ferromagnetism which appears at the N\'eel temperature due to a Dzyaloshinsky-Moriya interaction, in a manner analogous to that seen in ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$.

Organizational Characteristics and Information Systems Planning: An Empirical Study

Abstract: Information Systems IS planning has gained considerable interest among researchers and practitioners in recent years because of the large investments that firms have made in IS and the increasingly strategic nature of the impact of information systems on organizational performance. Since IS planning is performed in an organizational context, characteristics of the organization may have a significant influence on the quality and effectiveness of the IS planning process. A research model is developed that links two major dimensions of IS planning-the quality of the planning process and planning effectiveness-with a set of eight organizational factors derived from contingency research in IS planning, strategic business planning, organizational studies, and technology innovation. The model is validated using data collected from a field survey of 249 senior IS executives. Canonical correlation analysis is used to test the research hypotheses and validate the model. The results of the study indicate that the two planning dimensions respectively reflecting the "means" and "ends" of IS planning are equally important. The results also indicate that planning resources, the intended strategic impact of IS on future business operations, the quality of facilitation mechanisms, the quality of implementation mechanisms, and the quality of strategic business planning are significantly associated with the quality and effectiveness of IS planning. The implications of the results to further research and to managerial practice are highlighted.

Insecticidal Properties of Several Monoterpenoids to the House Fly (Diptera: Muscidae), Red Flour Beetle (Coleoptera: Tenebrionidae), and Southern Corn Rootworm (Coleoptera: Chrysomelidae)

Abstract: House flies, Musca domestica (L.), and their eggs were treated with 22 monoterpenoids to determine the topical, fumigant, and ovicidal activity of each compound. Fumigant activity of 14 monoterpenoids were examined further using red flour beetles, Tribolium castaneum (Herbst). Third-instar southern corn rootworm, Diabrotica undecimpunctata howardi Barber, were treated with carvacrol, citral, citronellal, menthol, pulegone, verbenol, and verbenone to determine their activity on larvae. Structure-activity relationships were evaluated with the toxicity data. We made comparisons between monocyclic aromatic, acyclic aliphatic, monocyclic aliphatic, and bicyclic aliphatic alcohols, ketones, aldehydes, and acids to determine toxicity differences involving the skeletal structure, amount of saturation, and associated functional groups of monoterapenoids. Ketones were more effective than alcohols in the topical, fumigant (T. castaneum), and ovicidal bioassays and less toxic than an analogous aldehyde in the topical, fumigant (M. domestica), and ovicidal bioassays. Aldehydes were more toxic than alcohols in the topical and fumigant (M. domestica) bioassays. In the topical and ovicidal bioassays, aromatic or acyclic alcohols, or both, were more effective than monocyclic and bicyclic alcohols. Vapors of bicyclic ketones were more toxic than monocyclic ketones to adult M. domestica. Monoterpenoid alcohols containing three carbon-carbon double bonds were more effective than saturated alcohols in the topical and larval bioassays. A mono-unsaturated ketone was more toxic than a structurally similar saturated ketone and two di-unsaturated ketones when it was applied topically to adult M. domestica. A saturated monocyclic ketone inhibited egg hatch more effectively than unsaturated monocyclic ketones.

Decomposition of different organic materials in soils

Abstract: Laboratory experiments were conducted to evaluate organic C mineralization of various organic materials added to soils. A soil sample was mixed with organic material to approximate a field application of 9 g organic C kg-1 soil (0.9% or 50 Mg ha-1). The organic materials used were four crop residues [corn (Zea mays L.), soybean (Glycine max L. Merr.), sorghum (Sorghum vulgare Pers.), and alfalfa (Medicago sativa L.)], four animal manures [chicken (Gallus domesticus), pig (Sus scrofa), horse (Equus caballus), and cow (Bos taurus)] and four sewage sludges [Correctionville (Imhoff tank), Charles City (holding tank), Davenport (secondary digester), and Keokuk (primary digester)]. The soil-organic material mixture was incubated under aerobic conditions at room temperature (20±2°C) for 30 days. The CO2 evolved was collected in standard KOH solution by continuously passing CO2-free air over the soil. Results showed that, in general, the amounts of CO2-C released mereased rapidly initially, but the pattern differed among the organic materials used. More than 50% of the total CO2 produced in 30 days of incubation was evolved in the first 6 days. Expressed as percentages of organic C added, the amounts of CO2 evolved ranged from 27% with corn to 58% with alfalfa. The corresponding percentages for animal manures ranged from 21 to 62% with horse and pig manures, respectively, and for sewage sludges they ranged from 10 to 39% for Charles City and Keokuk sludges. All CO2 evolution data conformed well to a first-order kinetic model. Potentially, readily mineralizable organic C values and first-order rate constants (k) of the organic matter-treated soils ranged from 1.422 g C kg-1 soil with ak value of 0.0784 day-1 to 6.253 g C kg-1 soil with ak value of 0.0300 day-1. The half-lives of the C remaining in soils ranged from 39 to 54 days for plant materials. The corresponding half-lives for the C remaining from animal manures and sewage sludges ranged from 37 to 169 days and from 39 to 330 days, respectively.