Showing papers by "Iowa State University published in 1997"

Giant Magnetocaloric Effect in Gd 5 \(Si 2 Ge 2 \)

Abstract: An extremely large magnetic entropy change has been discovered in $\mathrm{Gd}{}_{5}(\mathrm{Si}{}_{2}\mathrm{Ge}{}_{2})$ when subjected to a change in the magnetic field. It exceeds the reversible (with respect to an alternating magnetic field) magnetocaloric effect in any known magnetic material by at least a factor of 2, and it is due to a first order $[\mathrm{ferromagnetic}(\mathrm{I})\ensuremath{\leftrightarrow}\mathrm{ferromagnetic}(\mathrm{II})]$ phase transition at 276 K and its unique magnetic field dependence.

Models of the Self: Self-Construals and Gender

Abstract: The authors first describe individual differences in the structure of the self. In the independent self-construal, representations of others are separate from the self. In the interdependent self-construal, others are considered part of the self (H. Markus & S. Kitayama, 1991). In general, men in the United States are thought to construct and maintain an independent self-construal, whereas women are thought to construct and maintain an interdependent self-construal. The authors review the psychological literature to demonstrate that many gender differences in cognition, motivation, emotion, and social behavior may be explained in terms of men's and women's different self-construals. Recognition of the interdependent self-construal as a possible alternative conception of the self may stimulate new investigations into the ways the self influences a person's thinking, feeling, and behaving.

Rethinking Genre in School and Society: An Activity Theory Analysis.

Abstract: This article attempts to expand and elaborate theories of social "context" and formal schooling, to understand the stakes involved in writing. It first sketches ways Russian activity theory in the tradition of A. N. Leont'ev may expand Bakhtinian dialogism, then elaborates the theory in terms of North American genre research, with examples drawn from research on writing in the disciplines in higher education. By tracing the relations of disciplinary genre systems to educational genre systems, through the boundary of the classroom genre system, the analyst/reformer can construct a model of the interactions of classroom practices with wider social practices. Activity theory analysis of genre systems may offer a theoretical bridge between the sociology of education and Vygotskian social psychology of classroom interaction, and contribute toward resolving the knotty problem of the relation of macro- and microstructure in literacy research based on various social theories of "context." ***** What makes one conversation more meaningful than another? For either an individual, a dyad, a collective, or even a culture? When three African American students who hope to be doctors some day sit down on one particular day to write a laboratory report in a college cell biology course, what are the stakes involved in those marks on a screen? For the students and their families and their neighborhoods and churches? For the instructor and his university and his profession of biology? For the profession of medicine and its patients and its government regulators? How can a student or teacher or researcher understand the meaningfulnessthe stakesof some (act of) writing. Vygotsky and his immediate successors did not use genre as a category of analysis. But in the last decade, a number of Vygotskian theorists have incorporated into their work various theories of genre. I will propose a synthesis of a number of elements from these theories, drawing most heavily on Charles Bazerman's (1994) analysis of genre as systems of speech acts within an overarching framework of Vygotskian activity theory (Leont'ev, 1981; Engestrom, 1987, 1993). The goal is to move toward a theory of writing useful in analyzing how students and teachers within individual classrooms use the discursive tools of classroom genres to interact (and not interact) with social practices beyond individual classroomsthose of schools, families, peers, disciplines, professions, political movements, unions, corporations, and so on. In other words, I am attempting to expand and elaborate theories of social "context" and formal schooling, to understand the stakes involved in writing. Literacy, Brandt (1990) persuasively argues, is "not the narrow ability to deal with texts but the broader ability to deal with other

Sources of nitrous oxide in soils

Abstract: Research to identify sources of nitrous oxide (N2O) in soils has indicated that most, if not all, of the N2O evolved from soils is produced by biological processes and that little, if any, is produced by chemical processes such as chemodenitrification. Early workers assumed that denitrification was the only biological process responsible for N2O production in soils and that essentially all of the N2O evolved from soils was produced through reduction of nitrate by denitrifying microorganisms under anaerobic conditions. It is now well established, however, that nitrifying microorganisms contribute significantly to emissions of N2O from soils and that most of the N2O evolved from aerobic soils treated with ammonium or ammonium-yielding fertilizers such as urea is produced during oxidation of ammonium to nitrate by these microorganisms. Support for the conclusion that chemoautotrophic nitrifiers such as Nitrosomonas europaea contribute significantly to production of N2O in soils treated with N fertilizers has been provided by studies showing that N2O emissions from such soils can be greatly reduced through addition of nitrification inhibitors such as nitrapyrin, which retard oxidation of ammonium by chemoautotrophic nitrifiers but do not retard reduction of nitrate by denitrifying microorganisms.

External Validity of “Trivial” Experiments: The Case of Laboratory Aggression:

Abstract: The external validity of artificial "trivial" laboratory settings is examined. Past views emphasizing generalizability of relations among conceptual variables are reviewed and affirmed. One major implication of typical challenges to the external validity of laboratory research is tested with aggression research: If laboratory research is low in external validity, then laboratory studies should fail to detect relations among variables that are correlated with aggression in "real-world" studies. Meta-analysis was used to examine 5 situational variables (provocation, violent media, alcohol, anonymity, hot temperature) and 3 individual difference variables (sex, Type A personality, trait aggressiveness) in real-world and laboratory aggression studies. Results strongly supported the extemal validity of trivial laboratory studies. Advice is given on how scholars might handle occasional descrepancies between laboratory and real-world findings.

Determinants of EDI adoption in the transportation industry

Abstract: This study examines the impact of various environmental, organizational, and technological factors on the adoption of innovation in the context of electronic data interchange (EDI) Based on research in information technology (IT) adoption, organizational studies and marketing a comprehensive research model is developed The model identifies eleven variables, under three broad categories (environmental, organizational, and innovation characteristics), that could potentially influence the adoption of EDI The research variables are operationalised using multi-item indicators and data collected from a large scale field survey of 950 firms in the trucking industry A total of 181 firms responded to the survey with near equal number of adopters and non-adopters Multivariate discriminant analysis is used to determine the impact of each of these variables on EDI adoption The results of data analysis indicate that four factors are important to discriminate adopters from non-adopters of EDI in the transportation industry They are: size of the firm, competitive pressure, customer support, and top management support

Commercial production of avidin from transgenic maize: characterization of transformant, production, processing, extraction and purification

Abstract: We have produced in transgenic maize seed the glycoprotein, avidin, which is native to avian, reptilian, and amphibian egg white. A transformant showing high-level expression of avidin was selected. Southern blot data revealed that four copies of the gene are present in this transformant. The foreign protein represents >2% of aqueous soluble extracted protein from populations of dry seed, a level higher than any heterologous protein previously reported for maize. In seed, greater than 55% of the extractable transgenic protein is present in the embryo, an organ representing only 12% of the dry weight of the seed. This indicates that the ubiquitin promoter which is generally considered to be constitutive, in this case may be showing a strong tissue preference in the seed. The mature protein is primarily localized to the intercellular spaces. An interesting trait of the transgenic plants expressing avidin is that the presence of the gene correlates with partial or total male sterility. Seed populations from transgenic plants were maintained by outcrossing and segregate 1:1 for the trait. In generations T2–T4, avidin expression remained high at 2.3% (230 mg/kg seed) of extractable protein from seed, though it varied from 1.5 to 3.0%. However, levels of expression did not appear to depend on pollen parent or growing location. Cracked and flaked kernels stored at −29°C or 10 °C for up to three months showed no significant loss of avidin activity. Commercial processing of harvested seed also generated no apparent loss of activity. The protein was purified to greater than 90% purity by affinity chromatography after extraction from ground mature maize seed. Physical characterization of purified maize-derived avidin demonstrated that the N-terminal amino acid sequence and biotin binding characteristics are identical to the native protein with near identical molecular weight and glycosylation. This study shows that producing avidin from maize is not only possible but has practical advantages over current methods.

Production of recombinant proteins in transgenic plants: practical considerations

Abstract: This review is based on our recent experience in producing the first commercial recombinant proteins in transgenic plants. We bring forward the issues that have to be considered in the process of selecting and developing a winning transgenic plant production system. From the production point of view, transcription, posttranscription, translation, and posttranslation are important events that can affect the quality and quantity of the final product. Understanding the rules of gene expression is required to develop sound strategies for optimization of recombinant protein production in plants. The level of recombinant protein accumulation is critical, but other factors such as crop selection, handling and processing of transgenic plant material, and downstream processing are equally important when considering commercial production. In some instances, the cost of downstream processing alone may determine the economic viability of a particular plant system. Some of the potential advantages of a plant production system such as the high levels of accumulation of recombinant proteins, glycosylation, compartmentalization within the cell, and natural storage stability in certain organs are incentives for aggressively pursuing recombinant protein production in plants. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 473-484, 1997.

CALL in the Year 2000: Still in Search of Research Paradigms?

Abstract: Advancements in the design and use of computer-assisted language learning (CALL) activities require that key questions about CALL be identified and effective research methods be used to answer them. In this paper, I suggest looking to research on other types of second language (L2) classroom learning activities for guidance in framing CALL research questions and in discovering relevant research methods. I begin with examples from the CALL literature demonstrating the diverse perspectives (e.g., cognitive psychology, constructivism, psycholinguistics) which have been suggested as ways of approaching CALL research. I then summarize the research questions and methods of L2 classroom research with emphasis on the "interactionist" approach and discourse analysis. Using three examples --computermediated communication, a microworld, and vocabulary in reading-I will illustrate how similar discourse analysis methods can address essential descriptive and evaluative questions about CALL activities. Finally, I will outline some implications of this perspective for design and investigation of CALL activities. A glance through the computer-assisted language learning (CALL) literature of the 1990s reveals the profession's quest for principled means of designing and evaluating CALL. Like researchers in other facets of applied linguistics, CALL researchers look to cross-disciplinary sources for perspectives and research methods. A recent example of the breadth of this quest is an article entitled "A theoretical foundation for the development of pedagogical tasks in computer mediated communication," in which the author seeks to "address the pedagogical merits [for second language teaching] of this new medium of communication in relation to current research in Anthropology, Cognitive Psychology, Communication Theory, Linguistics, and Second Language Acquisition (SLA)" (Salaberry, 1996, p. 6). Similarly, in the commentary on a recent collection of papers about intelligent tutoring systems for foreign language learning, the authors draw their comments from perspectives in learning theory, psycholinguistics, human-computer interaction, psychology (MacWhinney, 1995), "a computationally oriented theory of language use" (Bailin, 1995), psycholinguistic theory (Garrett, 1995), theory of novice vs. expert learning, constructivism, and individual differences theory (Oxford, 1995). These diverse perspectives are directed at general questions of how CALL research can increase our understanding of CALL activities. At the same time, there is a need to specify the particularly relevant questions about CALL and to identify ways that they can be investigated through empirical research. In this paper, I suggest that our understanding of CALL would benefit from addressing questions similar to those posed about other L2 classroom learning and from applying the methods used to study L2 learning in other types of classroom activities. I will CALL in the Year 2000: Still in Search of Research Paradigms? http://llt.msu.edu/vol1num1/chapelle/default.html 1 of 13 10/30/2015 11:09 AM begin with some examples from the CALL literature which demonstrate the need to look to empirical research methods for investigating instructed SLA. I will then turn to a brief explanation of the research questions and methods of L2 classroom research with emphasis on discourse analysis methods for investigating learners use of L2 tasks. Illustrations are provided of how analogous research questions can be posed for CALL activities and how similar discourse analysis methods can help to investigate CALL use. Finally, I note examples of how classroom research perspectives might inform CALL design. THE NEED FOR EMPIRAL RESEARCH METHODS FOR CALL Because CALL practice draws on cross-disciplinary work, CALL researchers and developers find themselves at the crossroads among disciplines that appear to offer insights for work in CALL. For example, it is evident from the following report of an intelligent tutoring system (ITS) project that some CALL developers see computational linguistics as a foundation for CALL:

Effect of tillage and residue management on enzyme activities in soils: III. Phosphatases and arylsulfatase

Abstract: This study was carried out to investigate the effect of tillage and residue management on activities of phosphatases (acid phosphatase, alkaline phosphatase, phosphodiesterase, and inorganic pyrophosphatase) and arylsulfatase. The land treatments included three tillage systems (no-till, chisel plow, and moldboard plow) in combination with corn residue placements in four replications. The activities of these enzymes in no-till/double mulch were significantly greater than those in the other treatments studied, including no-till/bare, no-till/normal, chisel/normal, chisel/mulch, moldboard/normal, and moldboard/mulch. The effect of mulching on activities of phosphatases was not as significant as on activities of arylsulfatase. The lowest enzyme activities were found in soil samples form no-till/bare and moldboard/normal treatments, with the exception of inorganic pyrophosphatase, which showed the lowest activity in no-till/bare only. Among the same residue placements, no-till and chisel plow showed comparable arylsulfatase activity, whereas the use of moldboard plow resulted in much lower arylsulfatase activity. The activities of phosphatases and arylsulfatase were significantly correlated with organic C in the 40 soil samples studies, with r values ranging from 0.71*** to 0.92***. The activities of alkaline phosphatase, phosphodiesterase, and arylsulfatase were significantly correlated with soil pH, with r values of 0.85***, 0.78***, and 0.77***, respectively, in the 28 surface soil samples studied, but acid phosphatase and inorganic pyrophosphatase activities were not significantly correlated with soil pH. The activities of phosphatases and arylsulfatase decreased markedly with increasing soil depth and this decrease was associated with a decrease in organic C content. The activities of these enzymes were also significantly intercorrelated, with r values ranging from 0.50*** to 0.92***.

Search for neutral heavy leptons produced in Z decays

Abstract: Weak isosinglet Neutral Heavy Leptons (m) have been searched for using data collected by the DELPHI detector corresponding to 3:3 106 hadronic Z0 decays at LEP1. Four separate searches have been performed, for short-lived m production giving monojet or acollinear jet topologies, and for long-lived m giving detectable secondary vertices or calorimeter clusters. No indication of the existence of these particles has been found, leading to an upper limit for the branching ratio BR(Z0 ! m) of about 1:310−6 at 95% confidence level for m masses between 3.5 and 50 GeV/c2. Outside this range the limit weakens rapidly with the m mass. The results are also interpreted in terms of limits for the single production of excited neutrinos.

LiV 2 O 4 : A Heavy Fermion Transition Metal Oxide

Abstract: A crossover with decreasing temperature $T$ from localized moment magnetism to heavy Fermi liquid behavior is reported for the metallic compound ${\mathrm{LiV}}_{2}{\mathrm{O}}_{4}$ with the fcc normal-spinel structure. At $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1\mathrm{K}$, the electronic heat capacity coefficient $\ensuremath{\gamma}\ensuremath{\approx}0.42\mathrm{J}/\mathrm{mol}{\mathrm{K}}^{2}$ is exceptionally large for a transition metal compound, the Wilson ratio $\ensuremath{\approx}1.7$, and the Korringa ratio $\ensuremath{\approx}0.7$. Our sample with the lowest level of paramagnetic defects showed no static magnetic order above 0.02 K. Superconductivity was not observed above 0.01 K.

Low-Frequency Stimulation of Afferent Aδ-Fibers Induces Long-Term Depression at Primary Afferent Synapses with Substantia Gelatinosa Neurons in the Rat

Abstract: Impulses in primary afferent nerve fibers may produce short- or long-lasting modifications in spinal nociception. Here we have identified a robust long-term depression (LTD) of synaptic transmission in substantia gelatinosa neurons that can be induced by low-frequency stimulation of primary afferent Adelta-fibers. Synaptic transmission between dorsal root afferents and neurons in the substantia gelatinosa of the spinal cord dorsal horn was examined by intracellular recording in a transverse slice dorsal root preparation of rat spinal cord. Conditioning stimulation of dorsal roots with 900 pulses given at 1 Hz (10 V, 0.1 msec) produced LTD of EPSP amplitudes in substantia gelatinosa neurons to 41 +/- 10% of control that lasted for at least 2 hr. When A- and C-fibers were recruited, conditioning stimulation was as effective as A-fiber stimulation alone. After LTD, synaptic strength could be increased to its original level by applying a second, high-frequency tetanic stimulus to the dorsal root, indicating that LTD is reversible and not attributable to damage of individual synapses. Bath application of the GABAA receptor antagonist bicuculline and glycine receptor antagonist strychnine did not affect LTD. When NMDA receptors were blocked by bath application of D-2-amino-5-phosphonovaleric acid, LTD was abolished or strongly reduced. Loading substantia gelatinosa neurons with Ca2+ chelator BAPTA also blocked or reduced LTD. After incubation of slices with calyculin A, a selective and membrane permeable inhibitor of protein phosphatases 1 and 2A, LTD was not attenuated. We propose that this form of LTD may be relevant for long-lasting segmental antinociception after afferent stimulation.

The National Resources Inventory: a long-term multi-resource monitoring programme

Abstract: Interest in natural resources and the environment has led to the development of new federal monitoring efforts, the expansion of existing federal inventory programmes, and discussions of inter-agency collaboration for natural resource assessment data collection. As federal programmes evolve, knowledge gained from existing long-term survey programmes can provide valuable contributions to statistical and operational aspects of survey efforts. This paper describes the National Resources Inventory (NRI), which has been conducted by the US Department of Agriculture's Natural Resources Conservation Service in cooperation with the Iowa State University Statistical Laboratory for several decades. The current NRI is a longitudinal survey of soil, water, and related environmental resources designed to assess conditions and trends every five years on non-federal US lands. An historical overview is provided highlighting the development of the survey programme. Sample design, data collection, and estimation procedures used in the 1992 NRI are described, and statistical issues related to long-term monitoring are discussed.

Preimaginal Development, Survival, and Field Abundance of Insect Predators on Transgenic Bacillus thuringiensis Corn

Abstract: Laboratory studies determined the effects of feeding corn, Zea mays L., pollen expressing a Cry1Ab protein derived from Bacillus thuringiensis (Berliner) subsp. kurstaki on 3 predatory species: Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae), Orius insidiosus Say (Heteroptera: Anthocoridae), and Chrysoperla carnea Stephens (Neuroptera: Chrysopidae). No acute detrimental effects of the transgenic B. thuringiensis pollen (Cry1Ab protein) on preimaginal development and survival were observed among these predators. The following percentage survival values (±SE) were observed: C. maculata , 89 ± 2.2% ( B. thuringiensis corn pollen), 69 ± 5.9% (non- B. thuringiensis corn pollen); O. insidiosus , 63 ± 12% ( B. thuringiensis corn pollen), 44 ± 10.2% (non- B. thuringiensis corn pollen); and C. carnea , 49 ± 3.5% ( B. thuringiensis and non- B. thuringiensis corn pollen). No detrimental effects were observed in the abundance of Ostrinia nubilalis (Hubner) (Lepidoptera: Pyralidae) predators (coccinellids, anthocorids, chrysopids) in B. thuringiensis corn compared with non- B. thuringiensis corn during 2 yr of field evaluations. Predator numbers observed before, during, and after pollen shed suggest that B. thuringiensis corn pollen will not affect natural enemy movement in corn. Additional studies are needed to test for chronic and reproductive effects over several generations before concluding that transgenic B. thuringiensis corn pollen has no effect on insect predators.

Psychological Distress and Help Seeking in Rural America

Abstract: The implications of exposure to acute and chronic stressors, and seeking mental health care, for increased psychological distress are examined. Research on economic stress, psychological distress, and rural agrarian values each point to increasing variability within rural areas. Using data from a panel study of 1,487 adults, a model predicting changes in depressive symptoms was specified and tested. Results show effects by size of place for men but not for women. Men living in rural villages of under 2,500 or in small towns of 2,500 to 9,999 people had significantly greater increases in depressive symptoms than men living in the country or in larger towns or cities. Size of place was also related to level of stigma toward mental health care. Persons living in the most rural environments were more likely to hold stigmatized attitudes toward mental health care and these views were strongly predictive of willingness to seek care. The combination of increased risk and less willingness to seek assistance places men living in small towns and villages in particular jeopardy for continuing problems involving depressed mood.

The Consensus Glossary of Temporal Database Concepts - February 1998 Version.

Abstract: This document1 contains definitions of a wide range of concepts specific to and widely used within temporal databases. In addition to providing definitions, the document also includes explanations of concepts as well as discussions of the adopted names.

Club theory: Thirty years later

Abstract: This paper presents a self-contained survey of club theory with an emphasis on the contributions of the last fifteen years. Club goods are contrasted with pure public goods, and equilibrium and optimality notions are contrasted. After presenting three basic representations of club theory, we focus on recent advances and generalizations that include heterogeneous memberships, transaction costs, uncertain utilization, asymmetric information, and noncompetitive influences. An agenda for research is indicated that includes further analysis of asymmetric information, institutional structure, and applications.

Implications of weed seedbank dynamics to weed management

Abstract: The species composition and density of weed seed in the soil vary greatly and are closely linked to the cropping history of the land. Altering tillage practices changes weed seed depth in the soil, which plays a role in weed species shifts and affects efficacy of control practices. Crop rotation and weed control practices also affect the weed seedbank. Information on the influence of cropping practices on the weed seedbank should be a useful tool for integrated weed management. Decision aid models use information on the weed seedbank to estimate weed populations, crop yield loss, and recommend weed control tactics. Understanding the light requirements of weed seed may provide new approaches to weed management. Improving and applying our understanding of weed seedbank dynamics is essential to developing improved weed management systems. The principles of plant ecology must be integrated with the science of weed management to develop strategies that take advantage of basic plant responses in weed management systems for agronomic crops.

Gender, prior knowledge, interest, and experience in electricity and conceptual change text manipulations in learning about direct current

Abstract: The present study investigated relationships between gender, interest and experience in electricity, and conceptual change text manipulations on learning fundamental direct current concepts. Conceptual change text has been shown to lead to better conceptual understanding of electrical concepts than traditional didactic text, but previous research suggested that the effect interacted with the gender of the participants. We hypothesized that interest moderated this interaction. In this study, men and women who had higher or lower interest in electricity and greater or lessor experience with electricity read conceptual change or traditional text. When interest level, experience, and prior knowledge were not included in the analysis, both gender and text type produced significant main effects. When interest level, experience, and prior knowledge were included in the analysis, conceptual change text led to better understanding of electricity concepts than did the traditional text, and the effect of gender was eliminated. This finding supports the hypothesis that prior interest level, experience, and knowledge mediate apparent gender differences in learning about electricity. It suggests that conceptual change text manipulations are likely to be effective for both men and women. © 1997 John Wiley & Sons, Inc. J Res Sci Teach 34: 107–123, 1997.

Entrepreneurial social infrastructure and locally initiated economic development in the nonmetropolitan united states

Abstract: A community embeddedness perspective hypothesizes that nonmetropolitan localities high on entrepreneurial social infrastructure (ESI) are more successful at implementing economic development projects than those lacking ESI. ESI is a format for converting social capital into organizational forms that facilitate collective action. Logistic regres- sion revealed that localities with projects were more likely to have an unbiased news- paper, multiple contributions by financial institutions to community projects, and more external linkages. Project communities place more emphasis on citizen involvement through civic organizations than through local government. Community-based patterns of interactions and organization are associated with successful collective economic development action. Building on ideas about community embeddedness and collective action, this article addresses the relationship between entrepreneurial social infrastructure (ESI) and eco- nomic development. The central hypothesis is that communities and counties with more ESI are more likely to have successfully implemented a recent economic development project than localities lacking in ESI. The analysis is based upon a national random sample of nonmetropolitan places and counties. The concept of entrepreneurial social infrastructure was developed by the senior researchers' in order to better understand why some communities remain economically vital while others do not. Location factors (John Batie, and Norris 1988) and theories of leadership have not provided adequate explanations of community vitality. For instance, one careful evaluation of leadership training programs in Montana and Pennsylvania, using a quasi-experimental design, showed an increase in organizational membership and leadership roles for program graduates compared to a matched sample of nonparticipants in such programs (Cook, Howell, and Weir 1985). However, we found no studies that

Barley yellow dwarf viruses.

Abstract: Barley yellow dwarf viruses represent one of the most economically important and ubiquitous groups of plant viruses. This review focuses primarily on four research areas in which progress has been most rapid. These include (a) evidence supporting reclassification of BYDVs into two genera; (b) elucidation of gene function and novel mechanisms controlling gene expression; (c) initial forays into understanding the complex interactions between BYDV virions and their aphid vectors; and (d ) replication of a BYDV satellite RNA. Economic losses, symptomatology, and means of control of BYD are also discussed.