Showing papers by "University of Georgia published in 2001"
TL;DR: The most consistent and pervasive effect is an increase in impervious surface cover within urban catchments, which alters the hydrology and geomorphology of streams as discussed by the authors, which results in predictable changes in stream habitat.
Abstract: The world’s population is concentrated in urban areas. This change in demography has brought landscape transformations that have a number of documented effects on stream ecosystems. The most consistent and pervasive effect is an increase in impervious surface cover within urban catchments, which alters the hydrology and geomorphology of streams. This results in predictable changes in stream habitat. In addition to imperviousness, runoff from urbanized surfaces as well as municipal and industrial discharges result in increased loading of nutrients, metals, pesticides, and other contaminants to streams. These changes result in consistent declines in the richness of algal, invertebrate, and fish communities in urban streams. Although understudied in urban streams, ecosystem processes are also affected by urbanization. Urban streams represent opportunities for ecologists interested in studying disturbance and contributing to more effective landscape management.
3,007 citations
TL;DR: A new Monte Carlo algorithm is presented that permits us to directly access the free energy and entropy, is independent of temperature, and is efficient for the study of both 1st order and 2nd order phase transitions.
Abstract: We present a new Monte Carlo algorithm that produces results of high accuracy with reduced simulational effort. Independent random walks are performed (concurrently or serially) in different, restricted ranges of energy, and the resultant density of states is modified continuously to produce locally flat histograms. This method permits us to directly access the free energy and entropy, is independent of temperature, and is efficient for the study of both 1st order and 2nd order phase transitions. It should also be useful for the study of complex systems with a rough energy landscape.
2,639 citations
TL;DR: The view of critical questions regarding pectin structure, biosynthesis, and function that need to be addressed in the coming decade are presented and new methods that may be useful to study localized pectins in the plant cell wall are described.
1,795 citations
TL;DR: A hardy, versatile, fast-growing plant that helps to remove arsenic from contaminated soils.
Abstract: A hardy, versatile, fast-growing plant helps to remove arsenic from contaminated soils.
1,704 citations
TL;DR: It was found that management support and resources help to address organizational issues that arise during warehouse implementations; resources, user participation, and highly-skilled project team members increase the likelihood that warehousing projects will finish on-time, on-budget, with the right functionality; and diverse, unstandardized source systems and poor development technology will increase the technical issues that project teams must overcome.
Abstract: The IT implementation literature suggests that various implementation factors play critical roles in the success of an information system; however, there is little empirical research about the implementation of data warehousing projects. Data warehousing has unique characteristics that may impact the importance of factors that apply to it. In this study, a cross-sectional survey investigated a model of data warehousing success. Data warehousing managers and data suppliers from 111 organizations completed paired mail questionnaires on implementation factors and the success of the warehouse. The results from a Partial Least Squares analysis of the data identified significant relationships between the system quality and data quality factors and perceived net benefits. It was found that management support and resources help to address organizational issues that arise during warehouse implementations; resources, user participation, and highly-skilled project team members increase the likelihood that warehousing projects will finish on-time, on-budget, with the right functionality; and diverse, unstandardized source systems and poor development technology will increase the technical issues that project teams must overcome. The implementation's success with organizational and project issues, in turn, influence the system quality of the data warehouse; however, data quality is best explained by factors not included in the research model.
1,579 citations
TL;DR: Andragogy and self-directed learning continue to be important to our present-day understanding of adult learning as mentioned in this paper, however, they are not always easy to be applied in practice.
Abstract: Andragogy and self-directed learning continue to be important to our present-day understanding of adult learning.
1,480 citations
Marine Biological Laboratory1, Oak Ridge National Laboratory2, Virginia Tech3, University of Georgia4, University of Illinois at Urbana–Champaign5, Landcare Research6, University of North Carolina at Greensboro7, University of New Hampshire8, Kansas State University9, Michigan State University10, Oregon State University11, Procter & Gamble12
TL;DR: A comparative 15N-tracer study of nitrogen dynamics in headwater streams from biomes throughout North America demonstrates that streams exert control over nutrient exports to rivers, lakes, and estuaries.
Abstract: A comparative 15 N-tracer study of nitrogen dynamics in headwater streams from biomes throughout North America demonstrates that streams exert control over nutrient exports to rivers, lakes, and estuaries. The most rapid uptake and transformation of inorganic nitrogen occurred in the smallest streams. Ammonium entering these streams was removed from the water within a few tens to hundreds of meters. Nitrate was also removed from stream water but traveled a distance 5 to 10 times as long, on average, as ammonium. Despite low ammonium concentration in stream water, nitrification rates were high, indicating that small streams are potentially important sources of atmospheric nitrous oxide. During seasons of high biological activity, the reaches of headwater streams typically export downstream less than half of the input of dissolved inorganic nitrogen from their watersheds.
1,407 citations
TL;DR: This work aims to provide a systematic literature review and meta-analyses of the determinants of blood clotting disorders and their Kessler’s disease progression as well as some of the mechanisms behind these reactions.
1,230 citations
TL;DR: In this article, the authors developed and tested a sequential extraction procedure (SEP) for As by choosing extraction reagents commonly used for sequential extraction of metals, Se and P, including NH 4 NO 3, NaOAc, NH 2 OH·HCl, EDTA, NH 4 OH and NH 4 F, were shown to either have only low extraction efficiency for As, or to be insufficiently selective or specific for the phases targeted.
1,137 citations
TL;DR: This chapter provides a theory of informal and incidental learning and updates this theory based on recent research.
Abstract: This chapter provides a theory of informal and incidental learning and updates this theory based on recent research.
1,118 citations
TL;DR: An efficient Monte Carlo algorithm using a random walk in energy space to obtain a very accurate estimate of the density of states for classical statistical models that overcomes the tunneling barrier between coexisting phases at first-order phase transitions.
Abstract: We describe an efficient Monte Carlo algorithm using a random walk in energy space to obtain a very accurate estimate of the density of states for classical statistical models. The density of states is modified at each step when the energy level is visited to produce a flat histogram. By carefully controlling the modification factor, we allow the density of states to converge to the true value very quickly, even for large systems. From the density of states at the end of the random walk, we can estimate thermodynamic quantities such as internal energy and specific heat capacity by calculating canonical averages at any temperature. Using this method, we not only can avoid repeating simulations at multiple temperatures, but we can also estimate the free energy and entropy, quantities that are not directly accessible by conventional Monte Carlo simulations. This algorithm is especially useful for complex systems with a rough landscape since all possible energy levels are visited with the same probability. As with the multicanonical Monte Carlo technique, our method overcomes the tunneling barrier between coexisting phases at first-order phase transitions. In this paper, we apply our algorithm to both first- and second-order phase transitions to demonstrate its efficiency and accuracy. We obtained direct simulational estimates for the density of states for two-dimensional ten-state Potts models on lattices up to 200 x 200 and Ising models on lattices up to 256 x 256. Our simulational results are compared to both exact solutions and existing numerical data obtained using other methods. Applying this approach to a three-dimensional +/-J spin-glass model, we estimate the internal energy and entropy at zero temperature; and, using a two-dimensional random walk in energy and order-parameter space, we obtain the (rough) canonical distribution and energy landscape in order-parameter space. Preliminary data suggest that the glass transition temperature is about 1.2 and that better estimates can be obtained with more extensive application of the method. This simulational method is not restricted to energy space and can be used to calculate the density of states for any parameter by a random walk in the corresponding space.
TL;DR: The results of this study indicate that marker-assisted selection for SIR QTLs is needed to introgress these loci into elite genetic backgrounds.
Abstract: There has been limited success over the past 30 yr in the development of superior soybean cultivars [Glycine max (L.) Merr] with insect resistance. Success may be hampered by the quantitative nature of resistance and by linkage drag from resistant plant introduction (Pl) donor parents. Soybean insect resistance quantitative trait loci (SIR QTLs) have been identified from PI 229358 and PI 171451 by restriction fragment length polymorphism (RFLP) analysis. The objective of this study was to tag the SIR QTLs from PI 229358 with simple sequence repeat (SSR) markers and to determine the extent to which the SIR QTLs have been introgressed in registered cultivars, germplasm releases, or breeding lines that have resistance derived from this PI or from PI 171451. Marker analysis defined intervals by 5 centimorgans (cM) or less for a SIR QTL on linkage group D1b (SIR-D1b), and for SIR-G, SIR-H, and SIR-M. SIR QTLs were tracked through pedigrees by evaluating the inheritance of PI alleles at marker loci tightly linked to the QTLs during the phenotypic selection for insect resistance. It was inferred that at least 13 of the 15 SIR genotypes studied had introgressed SIR-M. PI genome introgression around SIR-M was measured to assess linkage drag. Some genotypes exhibited a dramatic reduction in the amount of linked PI genome, which likely occurred in response to phenotypic selection for agronomic performance as a means of reducing linkage drag. Only a few genotypes were inferred to possess SIR-G or SIR-H, and no genotypes possessed SIR-D1b. The results of this study indicate that marker-assisted selection for SIR QTLs is needed to introgress these loci into elite genetic backgrounds.
TL;DR: In this paper, the authors present an opacity sampling model for brown dwarfs and very low mass stars in the following two limiting cases of dust grain formation: (1) Inefficient gravitational settling (i.e., the dust is distributed according to the chemical equilibrium predictions) and (2) efficient gravitational settling, where the dust forms and depletes refractory elements from the gas, but their opacity does not affect the thermal structure).
Abstract: We present opacity sampling model atmospheres, synthetic spectra, and colors for brown dwarfs and very low mass stars in the following two limiting cases of dust grain formation: (1) Inefficient gravitational settling (i.e., the dust is distributed according to the chemical equilibrium predictions) and (2) efficient gravitational settling (i.e., the dust forms and depletes refractory elements from the gas, but their opacity does not affect the thermal structure). The models include the formation of over 600 gas-phase species and 1000 liquids and crystals and the opacities of 30 different types of grains including corundum (Al2O3), the magnesium aluminum spinel MgAl2O4, iron, enstatite (MgSiO3), forsterite (Mg2SiO4), amorphous carbon, SiC, and a number of calcium silicates. The models extend from the beginning of the grain formation regime well into the condensation regime of water ice (Teff = 3000-100 K) and encompass the range of log g = 2.5-6.0 at solar metallicity. We find that silicate dust grains can form abundantly in the outer atmospheric layers of red and brown dwarfs with a spectral type later than M8. The greenhouse effects of dust opacities provide a natural explanation for the peculiarly red spectroscopic distribution of the latest M dwarfs and young brown dwarfs. The grainless (cond) models, on the other hand, correspond closely to methane brown dwarfs such as Gliese 229B. We also discover that the λλ5891, 5897 Na I D and λλ7687, 7701 K I resonance doublets play a critical role in T dwarfs, in which their red wings define the pseudocontinuum from the I to the Z bandpass.
TL;DR: If and how the field has advanced in instrument validation is determined, and approaches are suggested for reinvigorating the quest for validation in IS research via content/construct validity, reliability, and manipulation validity.
Abstract: Over 10 years ago, the issue of whether IS researchers were rigorously validating their quantitative, positivist instruments was raised (Straub 1989). In the years that have passed since that time, the profession has undergone many changes. Novel technologies and management trends have come and gone. New professional societies have been formed and grown in prominence and new demands have been placed on the field's research and teaching obligations. But the issue of rigor in IS research has persisted throughout all such changes. Without solid validation of the instruments that are used to gather data upon which findings and interpretations are based, the very scientific basis of positivist, quantitative research is threatened.
As a retrospective on the Straub article, this research seeks to determine if and how the field has advanced in instrument validation. As evidence of the change, we coded positivist, quantitative research articles in five major journals over a recent three year period for use of validation techniques. Findings suggest that the field has advanced in many areas, but, overall, it appears that a majority of published studies are still not sufficiently validating their instruments. Based on these findings, approaches are suggested for reinvigorating the quest for validation in IS research via content/construct validity, reliability, and manipulation validity.
TL;DR: The demonstration that tobacco plants release temporally different volatile blends and that lepidopteran herbivores use induced plant signals released during the dark phase to choose sites for oviposition adds a new dimension to the understanding of the role of chemical cues in mediating tritrophic interactions.
Abstract: Plants respond to insect herbivory by synthesizing and releasing complex blends of volatile compounds, which provide important host-location cues for insects that are natural enemies of herbivores1,2,3. The effects of these volatile blends on herbivore behaviour have been investigated to only a limited extent4,5, in part because of the assumption that herbivore-induced volatile emissions occur mainly during the light phase of the photoperiod6,7. Because many moths—whose larvae are some of the most important insect herbivores—are nocturnal, herbivore-induced plant volatiles have not hitherto been considered to be temporally available as host-location cues for ovipositing females. Here we present chemical and behavioural assays showing that tobacco plants (Nicotiana tabacum) release herbivore-induced volatiles during both night and day. Moreover, several volatile compounds are released exclusively at night and are highly repellent to female moths (Heliothis virescens). The demonstration that tobacco plants release temporally different volatile blends and that lepidopteran herbivores use induced plant signals released during the dark phase to choose sites for oviposition adds a new dimension to our understanding of the role of chemical cues in mediating tritrophic interactions.
Duke University1, University of Wisconsin-Madison2, Ecological Society of America3, Kansas State University4, Princeton University5, University of Notre Dame6, University of Michigan7, National Center for Atmospheric Research8, University of Georgia9, Louisiana State University10, University of Buenos Aires11, Colorado State University12, United States Department of Agriculture13
TL;DR: Access to reliable forecasts of ecosystem state, ecosystem services, and natural capital will increase the ability to forecast ecosystem change and create a capacity to produce, evaluate, and communicate forecasts of critical ecosystem services.
Abstract: Planning and decision-making can be improved by access to reliable forecasts of ecosystem state, ecosystem services, and natural capital. Availability of new data sets, together with progress in computation and statistics, will increase our ability to forecast ecosystem change. An agenda that would lead toward a capacity to produce, evaluate, and communicate forecasts of critical ecosystem services requires a process that engages scientists and decision-makers. Interdisciplinary linkages are necessary because of the climate and societal controls on ecosystems, the feedbacks involving social change, and the decision-making relevance of forecasts.
TL;DR: In this article, the authors survey the literature examining the privatization of state-owned enterprises (SOEs) in both non-transition and transition countries, how investors in privatizations have fared, and the impact of privatization on the development of capital markets and corporate governance.
Abstract: This study surveys the literature examining the privatization of state-owned enterprises(SOEs). We overview the history of privatization, the theoretical and empirical evidence on the relative performance of state owned and privately owned firms, the types of privatization, if and by how much has privatization improved the performance of former SOEs in both non-transition and transition countries, how investors in privatizations have fared, the impact of privatization on the development of capital markets and corporate governance. We concentrate on the empirical evidence on the effects of privatization on firm performance. In most setting privatization "works" in that the firms become more efficient, more profitable, financially healthier, and reward investors. While this holds in both transition and non-transition economies, there is more variation in transition economies. Especially in transition economies, the identity of the new owners and managers is important in determining post-privatization performance.
TL;DR: This review highlights an important series of wildlife EIDs: amphibian chytridiomycosis; diseases of marine invertebrates and vertebrates and two recently-emerged viral zoonoses, Nipah virus disease and West Nile virus disease, and comments on the need for greater medical and microbiological input into the study of wildlife diseases.
TL;DR: A thorough understanding of the organismal responses occurring during bleaching will help explain changes in coral populations and in the coral reef community, and perhaps assist in predicting the future of reef corals and coral reefs during the next century of global climate change.
Abstract: 'It should be clear that the upper temperature limit for life cannot be accurately defined' (Schmidt-Nielsen 1996). The thermal physiology of zooxanthellate reef corals is reviewed in this paper in the context of organismal and biochemical responses occurring during coral bleaching, with emphasis on methods of detection and interpretation of animal and algal symbiont stress. Coral bleaching, as presently defined in the literature, is a highly subjective term used to describe a variety of conditions pertaining to low symbiont densities in the coral–algal complex, including response to thermal stress. Three general types of high-temperature bleaching are defined: physiological bleaching, which may or may not include higher-than-normal temperature responses; algal-stress bleaching, involving dysfunction of symbiotic algae at high light and/or high temperatures; and animal-stress bleaching, where coral cells containing symbiotic algae are shed from the gastrodermal layer of cells. Since none of these methods of bleaching is mutually exclusive, a combination of intrusive and non-intrusive techniques is necessary to determine which mechanisms of symbiont loss are occurring. While quantification of symbiont densities, algal pigments, and coral tissue biomass provide unambiguous evidence of bleaching severity, measurements of physiological and biochemical degradation offer additional correlative evidence of temperature stress. Pulse-amplitude-modulated (PAM) fluorometry has emerged as an easy and relatively inexpensive non-invasive technique for monitoring symbiotic algal function both in situ and in the laboratory, when proper assumptions and interpretations are made. The roles of global warming, water quality, acclimation/adaptation processes, and relation to coral disease and reef heterogeneity are also discussed. A thorough understanding of the organismal responses occurring during bleaching will help explain changes in coral populations and in the coral reef community, and perhaps assist in predicting the future of reef corals and coral reefs during the next century of global climate change.
TL;DR: To the extent that habitat association reflects habitat specialization, the results suggest that local habitat specialization plays a limited role in the maintenance of species diversity in this forest.
Abstract: Summary 1 Tests of habitat association among species of tropical trees and shrubs often assume that individual stems can be treated as independent sample units, even though limited dispersal conflicts with this assumption by causing new recruits to occur near maternal parents and siblings. 2 We developed methods for assessing patterns of association between mapped plants and mapped habitat types that explicitly incorporate spatial structure, thereby eliminating the need to assume independence among stems. 3 We used these methods to determine habitat-association patterns for 171 species of trees and shrubs within the permanent 50-ha Forest Dynamics Project plot on Barro Colorado Island, Panama. 4 Many fewer significant habitat associations result from the new methods than from traditional, but inappropriate, chi-square tests. The low-lying plateau, the most extensive habitat on the 50-ha plot, had nine species positively associated with it and 19 species negatively associated, leaving 143 species whose distributions were not biased with respect to this habitat. A small swamp in the plot was the most distinct habitat, with 32 species positively and 20 species negatively associated, leaving more than two-thirds of the species neither positively nor negatively associated. 5 To the extent that habitat association reflects habitat specialization, our results suggest that local habitat specialization plays a limited role in the maintenance of species diversity in this forest.
TL;DR: Together, these multiple regulatory controls orchestrate overall and region‐specific adipose tissue cellularity responses associated with the development of hyperplastic obesity.
Abstract: Expanded adipose tissue mass increases the risk for many clinical conditions including diabetes, hypertension, coronary atherosclerotic heart disease, and some forms of cancer. Therefore, it is imperative that we understand the mechanisms by which fat pads expand. The enlargement of fat cells during the development of obesity has been previously hypothesized to be a triggering factor for the proliferation of new fat cells. There is now a preponderance of evidence that adipose tissue is a source of growth factors such as IGF-I, IGF binding proteins, TNF alpha, angiotensin II, and MCSF that are capable of stimulating proliferation. The relative importance of these autocrine/paracrine factors in the normal control of preadipocyte proliferation is unknown. In addition, the proliferative response of preadipocytes to the paracrine milieu is undoubtedly modulated by neural inputs to fat tissue and/or serum factors. Together, these multiple regulatory controls orchestrate overall and region-specific adipose tissue cellularity responses associated with the development of hyperplastic obesity. Both in vivo and in vitro studies are needed to understand the complex, interacting physiological mechanisms by which growth of this important organ is regulated.
TL;DR: It is proposed that research efforts so far have been hampered by the adoption of models and perspectives that are narrow and do not adequately capture the complexity associated with the adolescent sexual experience.
TL;DR: This method successfully distinguished rRNA gene sequence libraries from soil and bioreactors and correctly failed to find differences between libraries of the same composition.
Abstract: To determine the significance of differences between clonal libraries of environmental rRNA gene sequences, differences between homologous coverage curves, CX(D), and heterologous coverage curves, CXY(D), were calculated by a Cramer-von Mises-type statistic and compared by a Monte Carlo test procedure. This method successfully distinguished rRNA gene sequence libraries from soil and bioreactors and correctly failed to find differences between libraries of the same composition.
TL;DR: The reduced cross-linking of RG-II in dwarf mur1 plants indicates that plant growth depends on wall pectic polysaccharide organization.
Abstract: Turgor-driven plant cell growth depends on wall structure. Two allelic l-fucose-deficient Arabidopsis thaliana mutants (mur1-1 and 1-2) are dwarfed and their rosette leaves do not grow normally. mur1 leaf cell walls contain normal amounts of the cell wall pectic polysaccharide rhamnogalacturonan II (RG-II), but only half exists as a borate cross-linked dimer. The altered structure of mur1 RG-II reduces the rate of formation and stability of this cross-link. Exogenous aqueous borate rescues the defect. The reduced cross-linking of RG-II in dwarf mur1 plants indicates that plant growth depends on wall pectic polysaccharide organization.
TL;DR: In this article, the authors analyse pre-main sequence evolutionary tracks for low mass stars with masses $m \le 1.4 \msol$ based on the Baraffe et al. (1998) input physics.
Abstract: We analyse pre-Main Sequence evolutionary tracks for low mass stars with masses $m \le 1.4 \msol$ based on the Baraffe et al. (1998) input physics. We also extend the recent Chabrier et al. (2000) evolutionary models based on dusty atmosphere to young brown dwarfs down to one mass of Jupiter. We analyse current theoretical uncertainties due to molecular line lists, convection and initial conditions. Simple tests on initial conditions show the high uncertainties of models at ages $\simle$ 1 Myr. We find a significant sensitivity of atmosphere profiles to the treatment of convection at low gravity and $\te < 4000$ K, whereas it vanishes as gravity increases. This effect adds another source of uncertainty on evolutionary tracks at very early phases. We show that at low surface gravity ($\log g \simle 3.5$,) the common picture of vertical Hayashi lines with constant $\te$ is oversimplified. The effect of a variation of initial deuterium abundance is studied. We compare our models with evolutionary tracks available in the literature and discuss the main differences. We finally analyse to which extent current observations of young systems provide a good test for pre-Main Sequence tracks.
TL;DR: In this article, the authors use the term hydrologic connectivity to refer to water-mediated transfer of matter, energy, and/or organisms within or between elements of the hydrological cycle.
Abstract: Increasingly, biological reserves throughout the world are threatened by cumulative alterations in hydrologic connectivity within the greater landscape. Hydrologic connectivity is used here in an ecological sense to refer to water-mediated transfer of matter, energy, and/or organisms within or between elements of the hydrologic cycle. Obvious human influences that alter this property include dams, associated flow regulation, groundwater extraction, and water diversion, all of which can result in a cascade of events in both aquatic and terrestrial ecosystems. Even disturbances well outside the boundaries of reserves can have profound effects on the biological integrity of these “protected” areas. Factors such as nutrient and toxic pollution and the spread of nonnative species are perpetuated by hydrologic connectivity, and their effects can be exacerbated by changes in this property. Hydrological alterations are now affecting reserves through increasingly broad feedback loops, ranging from overdrawn aquife...
TL;DR: In this paper, the authors argue that more research is needed in the areas of teachers' beliefs, knowledge, and practices of inquiry-based science, as well as, student learning.
Abstract: In this article we assert a potential research agenda for the teaching and learning of science as inquiry as part of the JRST series on reform in science education. Drawing on the theoretical frameworks of cognitive and sociocultural constructivism, cultural models of meaning, the dialogic function of language, and transformational models of teacher education, we propose that more research is needed in the areas of teachers' beliefs, knowledge, and practices of inquiry-based science, as well as, student learning. Because the efficacy of reform efforts rest largely with teachers, their voices need to be included in the design and implementation of inquiry-based curriculum. As we review the literature and pose future research questions, we propose that particular attention be paid to research on inquiry in diverse classrooms, and to modes of inquiry-based instruction that are designed by teachers. fl 2001 John Wiley & Sons, Inc. J Res Sci Teach 38: 631 - 645, 2001 Today's reform rhetoric has revived the concept of inquiry as representing the essence of science education. Reform documents such as the National Science Education Standards are promoting inquiry as the ''central strategy for teaching science.'' The editors of the Journal of Research in Science Teaching have encouraged dialogue on the efficacy of programs, such as inquiry-based science, that are being initiated or implemented in our schools. The editors state, ''this reform effort represents unfinished business for the science education community. Despite the seeming efficacy of the goals and claims that underlie current reform, there has been little formal, scholarly effort on the part of the science education community to ground the reform carefully in research.'' As part of a series of articles in JRST that explore the relationship between research and reform, this article discusses the need for research on the topic of inquiry. The purpose of this article is to propose a direction for future research on inquiry that places teacher knowledge, actions, and meanings for inquiry-based science at the center of the reform process. The proposal of a research agenda for inquiry approaches that are centered on teacher beliefs and knowledge may accelerate the production of a research literature that bridges the theory - practice gap in this important area. In this article, we present the position that additional
TL;DR: In temperate ocean surface waters and estuarine waters, growth and respiration may be increased experimentally either by raising the temperature or by increasing organic substrate concentrations, providing indirect evidence that the lim- itation is an effect of temperature on substrate uptake or assimilation.
Abstract: Active heterotrophic bacterial communities exist in all marine environments, and although their growth rates or respiratory rates may be limited by the interaction of low substrate concentrations with temperatures near their lower limit for growth, temperature and substrate con- centrations are rarely considered together as limiting factors. Moreover, attempts to evaluate meta- bolic limits by both temperature and substrate concentration have sometimes led to confusing con- clusions, because, while we can measure dissolved organic carbon (DOC) concentrations in natural waters, much of it is not readily available to heterotrophic bacteria. In spite of this procedural limita- tion, it can be helpful to regard temperature and substrate concentration as potential limiting factors that interact. In temperate ocean surface waters and estuarine waters, where bacterial growth is often reduced in winter, growth and respiration may be increased experimentally either by raising the tem- perature or by increasing organic substrate concentrations, providing indirect evidence that the lim- itation is an effect of temperature on substrate uptake or assimilation. Experimental work with bac- terial isolates also has shown a temperature-substrate interaction. In permanently cold polar waters, most heterotrophic bacteria appear to be living at temperatures well below their optima for growth. Nevertheless, bacteria in permanently cold surface waters can achieve activity rates in summer that are as high as those in temperate waters. In sea ice, rates of bacterial production are most often low, even though concentrations of substrates, including free amino acids, are sometimes much higher than they are in seawater. This suggests that at sea ice temperatures heterotrophic bacteria have low- ered ability to take up or utilize organic substrates.
TL;DR: A new model for interpreting GSS effects on performance (a Fit-Appropriation Model) is developed, which argues that GSS performance is affected by two factors: the fit between the task and the GSS structures selected for use and the appropriation support the group receives in the form of training, facilitation, and software restrictiveness.
Abstract: Many previous papers have lamented the fact that the findings of past GSS research have been inconsistent. This paper develops a new model for interpreting GSS effects on performance (a Fit-Appropriation Model), which argues that GSS performance is affected by two factors. The first is the fit between the task and the GSS structures selected for use (i.e., communication support and information processing support). The second is the appropriation support the group receives in the form of training, facilitation, and software restrictiveness to help them effectively incorporate the selected GSS structures into their meeting process. A meta-analysis using this model to organize and classify past research found that when used appropriately (i.e., there is a fit between the GSS structures and the task, and the group receives appropriation support), GSS use increased the number of ideas generated, took less time, and led to more satisfied participants than if the group worked without the GSS. Fitting the GSS to the task had the most impact on outcome effectiveness (decision quality and ideas), while appropriation support had the most impact on the process (time required and process satisfaction). We conclude that when using this theoretical lens, the results of GSS research do not appear inconsistent.
TL;DR: Nurturant/involved parenting and collective socialization processes were inversely associated, and harsh/inconsistent parenting was positively associated, with deviant peer affiliations.
Abstract: This study focused on hypotheses about the contributions of neighborhood disadvantage, collective socialization, and parenting to African American children's affiliation with deviant peers. A total of 867 families living in Georgia and Iowa, each with a 10- to 12-year-old child, participated. Unique contributions to deviant peer affiliation were examined using a hierarchical linear model. Community disadvantage derived from census data had a significant positive effect on deviant peer affiliations. Nurturant/involved parenting and collective socialization processes were inversely associated, and harsh/inconsistent parenting was positively associated, with deviant peer affiliations. The effects of nurturant/involved parenting and collective socialization were most pronounced for children residing in the most disadvantaged neighborhoods.