scispace - formally typeset
Search or ask a question

Showing papers by "Colorado State University published in 1997"


Journal ArticleDOI
TL;DR: In this article, Naiman et al. pointed out that harnessing of streams and rivers comes at great cost: Many rivers no longer support socially valued native species or sustain healthy ecosystems that provide important goods and services.
Abstract: H umans have long been fascinated by the dynamism of free-flowing waters. Yet we have expended great effort to tame rivers for transportation, water supply, flood control, agriculture, and power generation. It is now recognized that harnessing of streams and rivers comes at great cost: Many rivers no longer support socially valued native species or sustain healthy ecosystems that provide important goods and services (Naiman et al. 1995, NRC 1992).

5,799 citations


Journal ArticleDOI
TL;DR: In this paper, the authors consider the problem of accounting for model uncertainty in linear regression models and propose two alternative approaches: the Occam's window approach and the Markov chain Monte Carlo approach.
Abstract: We consider the problem of accounting for model uncertainty in linear regression models. Conditioning on a single selected model ignores model uncertainty, and thus leads to the underestimation of uncertainty when making inferences about quantities of interest. A Bayesian solution to this problem involves averaging over all possible models (i.e., combinations of predictors) when making inferences about quantities of interest. This approach is often not practical. In this article we offer two alternative approaches. First, we describe an ad hoc procedure, “Occam's window,” which indicates a small set of models over which a model average can be computed. Second, we describe a Markov chain Monte Carlo approach that directly approximates the exact solution. In the presence of model uncertainty, both of these model averaging procedures provide better predictive performance than any single model that might reasonably have been selected. In the extreme case where there are many candidate predictors but ...

1,804 citations


Journal ArticleDOI
24 Jan 1997-Science
TL;DR: Modern schemes incorporate biogeochemical and ecological knowledge and, when coupled with advanced climate and ocean models, will be capable of modeling the biological and physical responses of the Earth system to global change, for example, increasing atmospheric carbon dioxide.
Abstract: Atmospheric general circulation models used for climate simulation and weather forecasting require the fluxes of radiation, heat, water vapor, and momentum across the land-atmosphere interface to be specified. These fluxes are calculated by submodels called land surface parameterizations. Over the last 20 years, these parameterizations have evolved from simple, unrealistic schemes into credible representations of the global soil-vegetation-atmosphere transfer system as advances in plant physiological and hydrological research, advances in satellite data interpretation, and the results of large-scale field experiments have been exploited. Some modern schemes incorporate biogeochemical and ecological knowledge and, when coupled with advanced climate and ocean models, will be capable of modeling the biological and physical responses of the Earth system to global change, for example, increasing atmospheric carbon dioxide.

1,390 citations


Journal ArticleDOI
01 Dec 1997-Geoderma
TL;DR: In this article, nine soil organic models were evaluated using twelve datasets from seven long-term experiments and the performance of the models was compared both qualitatively and quantitatively, and possible reasons for differences in model performance were discussed in detail.

1,064 citations


Journal ArticleDOI
TL;DR: In this article, the consequences of organizational politics and organizational support on two separate samples of employees were investigated, and it was found that support is related to negative work outcomes while politics is associated with positive ones.
Abstract: The purpose of this paper is to report two studies that investigated the consequences of organizational politics and organizational support on two separate samples of employees. Study 1 surveys 69 full-time employees, while Study 2's sample includes 185 part-time workers. Four major findings were observed. First, the present studies replicated prior findings concerning the relationships of politics and support to such variables as withdrawal behaviors, turnover intentions, job satisfaction and organizational commitment. In general, politics is related to negative work outcomes while support is related to positive ones. Consistent results were obtained within both the full- and part-time samples. Second, we elaborated upon previous work concerning the relationship of politics and support to job involvement. Third, we found in both samples that politics and support did predict above and beyond each other, suggesting that they should be viewed as separate constructs rather than opposite ends of a single continuum. Lastly, Study 2 extended the research on politics and support by analyzing their relationships to four work stress variables: job tension, somatic tension, general fatigue, and burnout. Each of these four variables was predicted by both politics and support. © 1997 by John Wiley & Sons, Ltd.

937 citations


Journal ArticleDOI
TL;DR: To accurately assess an animal's reaction, a combination of behavioral and physiological measurements will provide the best overall measurement of animal discomfort.
Abstract: Fear is a very strong stressor, and the highly variable results of handling and transportation studies are likely to be due to different levels of psychological stress. Psychological stress is fear stress. Some examples are restraint, contact with people, or exposure to novelty. In many different animals, stimulation of the amygdala with an implanted electrode triggers a complex pattern of behavior and autonomic responses that resemble fear in humans. Both previous experience and genetic factors affecting temperament will interact in complex ways to determine how fearful an animal may become when it is handled or transported. Cattle trained and habituated to a squeeze chute may have baseline cortisol levels and be behaviorally calm, whereas extensively reared animals may have elevated cortisol levels in the same squeeze chute. The squeeze chute is perceived as neutral and non-threatening to one animal; to another animal, the novelty of it may trigger intense fear. Novelty is a strong stressor when an animal is suddenly confronted with it. To accurately assess an animal's reaction, a combination of behavioral and physiological measurements will provide the best overall measurement of animal discomfort.

928 citations



Journal ArticleDOI
TL;DR: In this article, the P2W15Nb3O629 polyoxoanion and Bu4N+- stabilized Ir∼190-450 (hereafter, Ir(0)∼300) nanoclusters are presented.
Abstract: Following an overview of the primitive state of mechanistic studies of the formation of nanoclusters, with a focus on LaMer's classic work on the formation of sulfur sols, kinetic and mechanistic studies of the formation of our recently reported novel P2W15Nb3O629- polyoxoanion- and Bu4N+- stabilized Ir∼190-450 (hereafter, Ir(0)∼300) nanoclusters are presented. The work reported consists of the full experimental and other details of the following eight major components: (i) development of an indirectbut easy, continuous, highly quantitative and thus powerfulmethod to monitor the formation of the Ir(0) nanoclusters via their catalytic hydrogenation activity and through the concept of pseudoelementary reaction steps; (ii) application of the appropriate kinetic equations for nucleation and autocatalysis, and then demonstration that these equations fit the observed, sigmoidal-shaped kinetic curves quantitatively with resultant rate constants k1 and k2; (iii) confirmation by a more direct, GLC method that the...

790 citations


Journal ArticleDOI
TL;DR: IL-12 is essential to the generation of a protective immune response to M. tuberculosis, with its main functions being the induction of the expression of IFN-γ and the activation of antigen-specific lymphocytes capable of creating a protective granuloma.
Abstract: Immunity to Mycobacterium tuberculosis infection is associated with the emergence of protective CD4 T cells that secrete cytokines, resulting in activation of macrophages and the recruitment of monocytes to initiate granuloma formation. The cytokine-mediating macrophage activation is interferon-gamma (IFN-gamma), which is largely dependent on interleukin-12 (IL-12) for its induction. To address the role of IL-12 in immunity to tuberculosis, IL-12 p40(-/-) mice were infected with M. tuberculosis and their capacity to control bacterial growth and other characteristics of their immune response were determined. The IL-12 p40(-/-) mice were unable to control bacterial growth and this appeared to be linked to the absence of both innate and acquired sources of IFN-gamma. T cell activation as measured by delayed type hypersensitivity and lymphocyte accumulation at the site of infection were both markedly reduced in the IL-12 p40(-/-) mice. Therefore, IL-12 is essential to the generation of a protective immune response to M. tuberculosis, with its main functions being the induction of the expression of IFN-gamma and the activation of antigen-specific lymphocytes capable of creating a protective granuloma.

729 citations


Journal ArticleDOI
TL;DR: The most appropriate management practices to increase soil carbon sink capacity vary regionally, dependent on both environmental and socioeconomic factors as discussed by the authors. But, effective mitigation policies will not be based on any single ‘magic bullet’ solutions, but rather on many modest reductions which are economically efficient and which confer additional benefits to society.
Abstract: . Agricultural soils, having been depleted of much of their native carbon stocks, have a significant CO2 sink capacity. Global estimates of this sink capacity are in the order of 20-30 Pg C over the next 50-100 years. Management practices to build up soil C must increase the input of organic matter to soil and/or decrease soil organic matter decomposition rates. The most appropriate management practices to increase soil C vary regionally, dependent on both environmental and socioeconomic factors. In temperate regions, key strategies involve increasing cropping frequency and reducing bare fallow, increasing the use of perennial forages (including N-fixing species) in crop rotations, retaining crop residues and reducing or eliminating tillage (i.e. no-till). In North America and Europe, conversion of marginal arable land to permanent perennial vegetation, to protect fragile soils and landscapes and/or reduce agricultural surpluses, provides additional opportunities for C sequestration. In the tropics, increasing C inputs to soil through improving the fertility and productivity of cropland and pastures is essential. In extensive systems with vegetated fallow periods (e.g. shifting cultivation), planted fallows and cover crops can increase C levels over the cropping cycle. Use of no-till, green manures and agroforestry are other beneficial practices. Overall, improving the productivity and sustainability of existing agricultural lands is crucial to help reduce the rate of new land clearing, from which large amounts of CO2 from biomass and soil are emitted to the atmosphere. Some regional analyses of soil C sequestration and sequestration potential have been performed, mainly for temperate industrialized countries. More are needed, especially for the tropics, to capture region-specific interactions between climate, soil and management resources that are lost in global level assessments. By itself, C sequestration in agricultural soils can make only modest contributions (e.g. 3-6% of total fossil C emissions) to mitigating greenhouse gas emissions. However, effective mitigation policies will not be based on any single ‘magic bullet’ solutions, but rather on many modest reductions which are economically efficient and which confer additional benefits to society. In this context, soil C sequestration is a significant mitigation option. Additional advantages of pursuing strategies to increase soil C are the added benefits of improved soil quality for improving agricultural productivity and sustainability.

720 citations


Journal ArticleDOI
30 May 1997-Science
TL;DR: A carboxylesterase domain was found within the amino acid sequences of Ag85A, B, and C, and each protein acted as a mycolyltransferase involved in the final stages of mycobacterial cell wall assembly, as shown by direct enzyme assay and site-directed mutagenesis.
Abstract: The dominant exported proteins and protective antigens of Mycobacterium tuberculosis are a triad of related gene products called the antigen 85 (Ag85) complex Each has also been implicated in disease pathogenesis through its fibronectin-binding capacities A carboxylesterase domain was found within the amino acid sequences of Ag85A, B, and C, and each protein acted as a mycolyltransferase involved in the final stages of mycobacterial cell wall assembly, as shown by direct enzyme assay and site-directed mutagenesis Furthermore, the use of an antagonist (6-azido-6-deoxy-α,α′-trehalose) of this activity demonstrates that these proteins are essential and potential targets for new antimycobacterial drugs

Journal ArticleDOI
TL;DR: In this paper, the performance of four open-top chambers for altering temperature at six sites in the Arctic and Antarctica was examined, and the effect of chambers on snow accumulation was variable with the Alexandra Fjord site showing an increased accumulation in chambers but no difference in the date of snowmelt.
Abstract: Passive open-top devices have been proposed as a method to experimentally increase temperature in high-latitude ecosystems. There is, however, little documentation on the efficacy of these devices. This paper examines the performance of four open-top chambers for altering temperature at six sites in the Arctic and Antarctica. Most of the heating effect was due to daytime warming above ambient; occasional night-time cooling below ambient, especially of air temperatures, depressed mean daily temperature. The mean daily temperatures at four arctic sites were generally increased by 1.2–1.8 °C; but occasionally, temperature depressions also occurred. Under optimal conditions at the antarctic site (dry soils, no vegetation, high radiation) mean daily soil temperatures were increased by +2.2 °C (–10 cm) to +5.2 °C (0 cm). Protection from wind may play a more important role than temperature per se in providing a favourable environment for plant growth within open-top devices. Wind speed had a generally negative impact on mean daily temperature. Daily global radiation was both positively and negatively related to chamber temperature response. The effect of chambers on snow accumulation was variable with the Alexandra Fjord site showing an increased accumulation in chambers but no difference in the date of snowmelt, while at Latnjajaure in a deep snowfall site, snowmelt occurred 1–2 weeks earlier in chambers, potentially increasing the growing season. Selection of a passive temperature-enhancing system requires balancing the temperature enhancement desired against potential unwanted ecological effects such as chamber overheating and altered light, moisture, and wind. In general, the more closed the temperature-enhancing system, the higher is the temperature enhancement, but the larger are the unwanted ecological effects. Open-top chambers alter temperature significantly and minimize most unwanted ecological effects; as a consequence, these chambers are a useful tool for studying the response of high-latitude ecosystems to warming.

Journal ArticleDOI
TL;DR: The template method for synthesizing nanostructures involves the synthesis of the desired material within the pores of a nanoporous membrane or other solid as discussed by the authors, which involves using porous alumina and polymeric filter membranes as the templates.
Abstract: The template method for synthesizing nanostructures involves the synthesis of the desired material within the pores of a nanoporous membrane or other solid. Our work has involved using porous alumina and polymeric filter membranes as the templates. Fibrils or tubules of the desired material are formed within each pore of the template membrane. A number of synthetic methods have been used to synthesize these nanostructures. This paper reviews sol−gel template synthesis: the use of sol−gel chemistry to synthesize semiconductor oxide micro- and nanostructures within the pores of micro- and nanoporous membranes. For example, TiO2 nanotubules and nanofibers of the anatase form have been synthesized. The high surface area offered by these TiO2 nanostructures has been used for photodecomposition of salicylic acid in sunlight. Enzyme immobilization by stannous bridges inside the TiO2 tubes has also been studied. In addition, V2O5 fibrous electrode materials have been prepared by this method and Li intercalation ...

Journal ArticleDOI
TL;DR: Faster RAS produced significant improvement in mean gait velocity, cadence, and stride length in all groups, and close synchronisation between rhythm and step frequency in the controls and both Parkinson's disease groups suggest evidence for rhythmic entrainment mechanisms even in the presence of basal ganglia dysfunction.
Abstract: OBJECTIVES: The effect of rhythmic auditory stimulation (RAS) on gait velocity, cadence, stride length, and symmetry was studied in 31 patients with idiopathic Parkinson's disease, 21 of them on (ON) and 10 off medication (OFF), and 10 healthy elderly subjects. METHOD: Patients walked under four conditions: (1) their own maximal speed without external rhythm; (2) with the RAS beat frequency matching the baseline cadence; (3) with RAS 10% faster than the baseline cadence; (4) without rhythm to check for carry over from RAS. Gait data were recorded via a computerised foot switch system. The RAS was delivered via a 50 ms square wave tone embedded in instrumental music (Renaissance style) in 2/4 metre prerecorded digitally on a sequencer for variable tempo reproduction. Patients on medication were tested in the morning 60-90 minutes after medication. Patients off medication were tested at the same time of day 24 hours after the last dose. Healthy elderly subjects were tested during the same time of day. RESULTS: Faster RAS produced significant improvement (P < 0.05) in mean gait velocity, cadence, and stride length in all groups. Close synchronisation between rhythm and step frequency in the controls and both Parkinson's disease groups suggest evidence for rhythmic entrainment mechanisms even in the presence of basal ganglia dysfunction. CONCLUSIONS: The results are consistent with and extend prior reports of rhythmic auditory facilitation in Parkinson's disease gait when there is mild to moderate impairment, and suggest a technique for gait rehabilitation in Parkinson's disease.

Journal ArticleDOI
TL;DR: In this paper, the first use of sol−gel chemistry to prepare semiconductor nanofibrils and tubules within the pores of an alumina template membrane was described, and 200 nm diameter TiO2 fibrils were used as photocatalysts for the decomposition of salicylic acid.
Abstract: The template method for preparing nanostructures entails synthesis of the desired material within the pores of a nanoporous membrane or other solid. A nanofibril or tubule of the desired material is obtained within each pore. Methods used previously to deposit materials within the pores of such membranes include electrochemical and electroless deposition and in situ polymerization. This paper describes the first use of sol−gel chemistry to prepare semiconductor nanofibrils and tubules within the pores of an alumina template membrane. TiO2, WO3, and ZnO nanostructures have been prepared. TiO2 nanofibrils with diameters of 22 nm were found to be single crystals of anatase with the c-axis oriented along the fibril axis. Bundles of these fibrils were also found to be single crystalline, suggesting that the indiviual fibrils are arranged in a highly organized fashion within the bundle. Finally, 200 nm diameter TiO2 fibrils were used as photocatalysts for the decomposition of salicylic acid.

Journal ArticleDOI
24 Oct 1997-Science
TL;DR: In this article, a simple membrane permeation experiment was performed to cleanly separate small molecules on the basis of molecular size using a collection of monodisperse gold nanotubules with inside diameters of molecular dimensions (less than 1 nanometer).
Abstract: Polymeric membranes that contain a collection of monodisperse gold nanotubules, with inside diameters of molecular dimensions (less than 1 nanometer), were used in a simple membrane-permeation experiment to cleanly separate small molecules on the basis of molecular size. For example, when such a membrane was presented with an aqueous feed solution containing pyridine (molecular weight 79) and quinine (molecular weight 324), only the smaller pyridine molecule was transported through the nanotubules and into a receiver solution on the other side of the membrane.

Journal ArticleDOI
TL;DR: In this article, the physics of vortex axisymmetrization was examined further, with the goal of elucidating the dynamics of outward-propagating spiral bands in hurricanes.
Abstract: In this paper we examine further the physics of vortex axisymmetrization, with the goal of elucidating the dynamics of outward-propagating spiral bands in hurricanes. the basic shysics is illustrated most simply for stable vorticity monopoles on an f-plane. Unlike the dynamics of sheared disturbances in rectilinear shear flow, axisymmetrizing disturbances on a vortex are accompanied by outward-propagating vortex Rossby-waves whose restoring mechanism is associated with the radial gradient of storm vorticity. Expressions for both phase and group velocities are derived and verified; they confirm earlier speculations on the existence of vortex Rossbywaves in hurricanes. Effects of radially propagating vortex Rossby-waves on the mean vortex are also analysed. In conjunction with sustained injection of vorticity near the radius of maximum winds, these results reveal a new mechanism of vortex intensification. the basic theory is then applied to a hurricane-like vortex in a shallow-water asymmetric-balance model. the wave mechanics developed here shows promise in elucidating basic mechanisms of hurricane evolution and structure changes, such as the formation of secondary eye-walls. Radar observations possessing adequate temporal resolution are consistent with the predictions of this work, though more refined observations are needed to quantify further the impact of mesoscale banded disturbances on the evolution of the hurricane vortex.

Journal ArticleDOI
01 Apr 1997-Ecology
TL;DR: In this paper, a 4-yr average of the ingegral of the NDVI (NDVI-J) using spatially aggregated values of ANPP was calibrated for temperate perennial grasslands, and a positive and statistically significant relationship between NDVI-I and ANPP for grassland areas with mean annual precipitation between 280 and 1150 mm, and mean annual temperature between 40 and 20'C.
Abstract: Several studies have suggested the existence of a positive relationship be- tween the Normalized Difference Vegetation Index (NDVI) derived from AVHRR/NOAA satellite data and either biomass or annual aboveground net primary production (ANPP) for different geographic areas and ecosystems. We calibrated a 4-yr average of the ingegral of the NDVI (NDVI-J) using spatially aggregated values of ANPP. We also provided an estimate of the energy conversion efficiency coefficient (?) of Monteith's equation. This is the first attempt to calibrate a standard NDVI product for temperate perennial grasslands. We found a positive and statistically significant relationship between NDVI-I and ANPP for grassland areas with mean annual precipitation between 280 and 1150 mm, and mean annual temperature between 40 and 20'C. Depending on the method used to estimate the fraction of photosynthetic active radiation, the energy conversion officency coefficient was constant (0.24 g C/MJ), or varied across the precipitation gradient, from 0.10 g C/MJ for the least productive to 0.20 g C/MJ for the most productive sites.

Journal ArticleDOI
TL;DR: In this paper, a catalytic asymmetric epoxidation method for olefins using potassium peroxomonosulfate (Oxone, Dupont) as oxidant and a fructose-derived ketone (1) as catalyst is described.
Abstract: This article describes a highly effective catalytic asymmetric epoxidation method for olefins using potassium peroxomonosulfate (Oxone, Dupont) as oxidant and a fructose-derived ketone (1) as catalyst. High enantioselectivies have been obtained for trans-disubstituted and trisubstituted olefins which can bear functional groups such as tributylsilyl ether, acetal, chloride, and ester. The enantiomeric excesses for cis-olefins and terminal olefins are not high yet. The current epoxidation shows that the catalyst efficiency is enhanced dramatically upon raising the pH. Mechanistic studies show that the epoxidation mainly proceeds via a spiro transition state, which provides a model for predicting the stereochemical outcome of the reaction. The planar transition state is likely to be the main competing pathway. The extent of the involvement of the planar mode is subject to the steric effect of the alkyl groups on the olefins.

Journal ArticleDOI
TL;DR: Findings from the dentate gyrus of epileptic kainate‐treated rats are strikingly similar to those reported for human temporal lobe epilepsy, and they suggest that neuron loss and axon reorganization in the temporal hippocampus may be important in epileptogenesis.
Abstract: We sought to describe quantitatively the morphological and functional changes that occur in the dentate gyrus of kainate-treated rats, an experimental model of temporal lobe epilepsy. Adult rats were treated systemically with kainic acid, and, months later, after displaying spontaneous recurrent motor seizures, their dentate gyri were examined. Histological, immunocytochemical, and quantitative stereological techniques were used to estimate numbers of neurons per dentate gyrus of various classes and to estimate the extent of granule cell axon reorganization along the septotemporal axis of the hippocampus in control rats and epileptic kainate-treated rats. Compared with control rats, epileptic kainate-treated rats had fewer Nissl-stained hilar neurons and fewer somatostatin-immunoreactive neurons. There was a correlation between the extent of hilar neuron loss and the extent of somatostatin-immunoreactive neuron loss. However, functional inhibition in the dentate gyrus, assessed with paired-pulse responses to perforant-pathway stimulation, revealed enhanced, and not the expected reduced, inhibition in epileptic kainate-treated rats. Numbers of parvalbumin- and cholecystokinin-immunoreactive neurons were similar in control rats and in most kainate-treated rats. A minority (36%) of the epileptic kainate-treated rats had fewer parvalbumin- and cholecystokinin-immunoreactive neurons than control rats, and those few (8%) with extreme loss in these interneuron classes showed markedly hyperexcitable dentate gyrus field-potential responses to orthodromic stimulation. Compared with control rats, epileptic kainate-treated rats had larger proportions of their granule cell and molecular layers infiltrated with Timm stain. There was a correlation between the extent of abnormal Timm staining and the extent of hilar neuron loss. Granule cell axon reorganization and dentate gyrus neuron loss were more severe in temporal vs. septal hippocampus. These findings from the dentate gyrus of epileptic kainate-treated rats are strikingly similar to those reported for human temporal lobe epilepsy, and they suggest that neuron loss and axon reorganization in the temporal hippocampus may be important in epileptogenesis.

Journal ArticleDOI
TL;DR: In this paper, a new two-moment microphysical parameterization is described, which predicts the mixing ratio and number concentration of rain, pristine ice crystals, snow, aggregates, graupel and hail.

Journal ArticleDOI
TL;DR: In this paper, the potential reduction of radiative forcing by the agricultural sector ranges from 115-33 Gt C equivalents per year of the total potential reduction, approximately 32% could result from reduction in CO2 emissions, 42% of carbon offsets by biofuel production on 15% of existing croplands, 16% from reduced CH4 emissions and 10% from reducing emissions of N2O Agriculture.
Abstract: Technologies to reduce net emissions of carbon dioxide, methane and nitrous oxide within the agriculture sector were reviewed to estimate the global potential for mitigation of these radiatively active greenhouse gases Our estimates of the potential reduction of radiative forcing by the agricultural sector range from 115-33 Gt C equivalents per year Of the total potential reduction, approximately 32% could result from reduction in CO2 emissions, 42% of carbon offsets by biofuel production on 15% of existing croplands, 16% from reduced CH4 emissions and 10% from reduced emissions of N2O Agriculture encompasses large regional differences in management practices and rates of potential adoption of mitigation practices Acceptability of mitigation options will depend on the extent to which sustainable production will be achieved or maintained and benefits will accrue to farmers Technologies such as no-till farming and strategic fertilizer placement and timing are now being adopted for reasons other than concern for climate change issues

Book ChapterDOI
01 Jan 1997
TL;DR: This chapter explores the relationship between the emerging discipline of landscape ecology and the existing discipline of metapopulation dynamics, with a focus on the area of theory.
Abstract: Publisher Summary This chapter explores the relationship between the emerging discipline of landscape ecology and the existing discipline of metapopulation dynamics. Landscape structure may often be an important component of metapopulation dynamics. Variations in patch quality in space and time, the form and permeability of patch boundaries, the composition and characteristics of surrounding mosaic elements, and the connectivity among landscape components may all influence the dynamics of local populations, especially, the ways in which populations are linked by movements of organisms. Metapopulation dynamics may contribute to the development of landscape ecology by emphasizing the dynamics that occur in a landscape. The spatiotemporal patterns of local extinctions and patch recolonizations create a shifting distribution of populations among patches. The second way in which metapopulation dynamics can contribute to landscape ecology is in the area of theory. In contrast to many other areas of ecology, landscape ecology has developed rather little theory. The lack of theory may stem, in part, from the diverse historical roots of the discipline, but it may also reflect the complexity of landscapes and their linkages.

Journal ArticleDOI
TL;DR: Evidence is offered that RAS is an efficient tool to enhance efforts in gait rehabilitation with acute stroke patients as well as conventional physical therapy gait program with the addition of rhythmic auditory stimulation.

Journal ArticleDOI
TL;DR: Assessment of temperament of feedlot cattle in Colorado shows that cattle that were quieter and calmer during handling had greater average daily gains than cattle that became agitated during routine handling.
Abstract: This study was conducted to assess the effect of temperament on the average daily gains of feedlot cattle. Cattle (292 steers and 144 heifers) were transported to Colorado feedlot facilities. Breeds studied included Braford (n = 177), Simmental x Red Angus (n = 92), Red Brangus (n = 70), Simbrah (n = 65), Angus (n = 18), and Tarentaise x Angus (n = 14). Cattle were temperament rated on a numerical scale (chute score) during routine weighing and processing. Data were separated into two groups based on breed, Brahman cross (> or = 25% Brahman) and nonBrahman breeding. Animals that had Brahman breeding had a higher mean temperament rating (3.45 +/- .09) or were more excitable than animals that had no Brahman influence (1.80 +/- .10); (P < .001). These data also show that heifers have a higher mean temperament rating than steers (P < .05). Temperament scores evaluated for each breed group also showed that increased temperament score resulted in decreased average daily gains (P < .05). These data show that cattle that were quieter and calmer during handling had greater average daily gains than cattle that became agitated during routine handling.

Journal ArticleDOI
TL;DR: In this paper, the cumulative effects of land use change on wildlife habitat using Summit County, CO, USA as a case study was investigated. Butler et al. proposed a general approach based on a functional relationship between effect on habitat and distance from development, which is sensitive to both housing density and spatial pattern.

Journal ArticleDOI
Holly J. Stein1, R. J. Markey, John W. Morgan, A. Du, Y. Sun 
TL;DR: In this paper, an isotope dilution with a modified alkali fusion procedure and negative thermal ion mass spectrometry yields highly precise and accurate Re-Os ages for molybdenite.
Abstract: Isotope dilution with a modified alkali fusion procedure and negative thermal ion mass spectrometry yields highly precise and accurate Re-Os ages for molybdenite from two well-studied molybdenite deposits in the East Qinling molybdenum belt, China. Individual Re-Os ages carry a 2Sigma precision of + or - 0.40 to 0.57 percent which includes a 0.31 percent uncertainty in the 187 Re decay constant. For the unusual carbonatite-hosted Mo-Pb deposit at Huanglongpu, the weighted average of seven analyses yields an age of 221.5 + or - 0.3 (0.15%) Ma. The weighted average of two analyses of molybdenite from a porphyry Mo deposit at Jinduicheng, about 10 km to the southwest, yields an age of 138.4 + or - 0.5 (0.39%) Ma. These data provide uncertainties an order of magnitude less than previous Re-Os ages. Molybdenite Re-Os ages are slightly older than ages obtained by other isotopic methods for genetically related host-rock and vein material. It appears that the direct dating of sulfide, rather than altered host and vein material, may be critical to acquiring the correct age for mineralization.The East Qinling molybdenum belt is part of a larger east-west-trending zone that marks the suture between two major cratonic blocks. Consequently, the belt was a site for Early-Middle Triassic compression (Indosinian orogeny) followed by Jurassic-Cretaceous extension (Yenshanian orogeny). We suggest that the Huanglongpu and Jinduicheng deposits provide an analogue for processes that may have been important in generating major molybdenum deposits in the Colorado mineral belt. In Colorado, Late Cretaceous (Laramide) compression-related, alkalic magmatism was followed by Tertiary (Rio Grande) extension-related, granitic magmatism and the development of major Climax-type porphyry Mo deposits. In particular, the Jinduicheng deposit appears to be a nearly perfect match for Climax-type mineralization in Colorado. In contrast, the older Huanglongpu deposit may record a mechanism whereby molybdenum is concentrated in the lower crust. In both the Qinling molybdenum belt and the Colorado mineral belt, a time gap of about 50 to 80 m.y. separates alkalic magmatism and exceptionally evolved granitic magmatism.

Journal ArticleDOI
TL;DR: The litter lignin:N ratio explained more of the variation in net N mineralization than climatic factors over a wide range of forest age classes, suggesting that litter quality may exert more than a proximal control over net N Mineralization by influencing soil organic matter quality throughout the soil profile independent of climate.
Abstract: The feedback between plant litterfall and nutrient cycling processes plays a major role in the regulation of nutrient availability and net primary production in terrestrial ecosystems. While several studies have examined site-specific feedbacks between litter chemistry and nitrogen (N) availability, little is known about the interaction between climate, litter chemistry, and N availability across different ecosystems. We assembled data from several studies spanning a wide range of vegetation, soils, and climatic regimes to examine the relationship between aboveground litter chemistry and annual net N mineralization. Net N mineralization declined strongly and non-linearly as the litter lignin:N ratio increased in forest ecosystems (r 2 = 0.74, P < 0.01). Net N mineralization decreased linearly as litter lignin concentration increased, but the relationship was significant (r 2 = 0.63, P < 0.01) only for tree species. Litterfall quantity, N concentration, and N content correlated poorly with net N mineralization across this range of sites (r 2 < 0.03, P = 0.17–0.26). The relationship between the litter lignin:N ratio and net N mineralization from forest floor and mineral soil was similar. The litter lignin:N ratio explained more of the variation in net N mineralization than climatic factors over a wide range of forest age classes, suggesting that litter quality (lignin:N ratio) may exert more than a proximal control over net N mineralization by influencing soil organic matter quality throughout the soil profile independent of climate.

Journal ArticleDOI
TL;DR: It is proposed that group I allergens facilitate invasion of the pollen tube into the maternal tissues by loosening the cell walls of the grass stigma and style.
Abstract: Group I allergens are the major allergens of grass pollen, but their biological function is unknown. These proteins are shown here to be structurally related to expansins, which are able to induce extension (creep) of plant cell walls. Extracts of maize pollen possess potent expansin-like activity, as measured in wall extension and wall stress-relaxation assays. This activity is selective for grass cell walls and is, at least partly, due to the action of maize group I allergens. We propose that group I allergens facilitate invasion of the pollen tube into the maternal tissues by loosening the cell walls of the grass stigma and style. Additionally, the presence of related mRNAs in vegetative tissues of rice, Arabidopsis, and soybean implies that allergen homologs may function to loosen walls in growing vegetative tissues as well.

Journal ArticleDOI
TL;DR: A set of generic metadata descriptors that could serve as the basis for a "metadata standard" for nongeospatial ecological data are presented and several recommendations related to future development and implementation of ecological metadata are concluded.
Abstract: Issues related to data preservation and sharing are receiving increased at- tention from scientific societies, funding agencies, and the broad scientific community. Ecologists, for example, are increasingly using data collected by other scientists to address questions at broader spatial, temporal, and thematic scales (e.g., global change, biodiversity, sustainability). No data set is perfect and self-explanatory. Ecologists must, therefore, rely upon a set of instructions or documentation to acquire a specific data set, determine its suitability for meeting specific research objectives, and accurately interpret results from subsequent processing, analysis, and modeling. "Metadata" represent the set of instructions or documentation that describe the content, context, quality, structure, and accessibility of a data set. Although geospatial metadata standards have been developed and widely endorsed by the geographical science community, such standards do not yet exist for the ecological sciences. In this paper, we examine potential benefits and costs associated with developing and implementing metadata for nongeospatial ecological data. We present a set of generic metadata descriptors that could serve as the basis for a "metadata standard" for nongeospatial ecological data. Alternative strategies for metadata implementation that meet differing organizational or investigator- specific objectives are presented. Finally, we conclude with several recommendations related to future development and implementation of ecological metadata.