Teachers’ subjective understandings of their students’ cognitive abilities have important implications for classroom interactions, children’s access to resources and opportunities, and educational equity more broadly. Using nationally representative data and three-level hierarchical linear models, this study explored the links between teacher perceptions and children’s sociodemographic backgrounds. The authors find that teachers perceive substantial racial-ethnic, socioeconomic, and gender differences in children’s literacy skills. Roughly half of these disparities are explained by actual between-group differences. The remaining perceptual inaccuracies flow more from classroom characteristics than from teachers’ professional or personal backgrounds (e.g., their own race or ethnicity). Specifically, holding students’ social and academic backgrounds constant, the authors find that teachers in lower-socioeconomic-status and lower-achieving contexts more often underestimate their students’ abilities. These results highlight the importance of recent policy efforts to avoid isolating traditionally disadvantaged children.

Foliar fungicides are often applied to wheat in Florida to decrease foliar diseases and increase yield of wheat. The variable, usually warm and wet, winter weather during the grain growing season in Florida creates an environment conducive to a number of foliar diseases of wheat. Septoria nodorum, Puccinia recondita, Erysiphe graminis tritici, and Helminthosporium sativum commonly attack winter wheat in Florida. With the present low crop value of wheat, growers often question whether it is economical to apply a fungicide. Fungicide treatments were found to influence grain yields and test weight in a study by Mascagni et. al. (1997) although there were significant cultivar X fungicide interactions. Seed treatments of fungicides have shown some lessening of wheat infection although, foliar fungicides used in conjunction with seed treatment may be necessary for a significant reduction in plant disease (Milus and Chalkley, 1997). New seed fungicide treatments like Gaucho and Dividend would be of interest to producers if seed treatments could effectively protect wheat from early season foliar infection and subsequent disease progression. Emergence of winter wheat when the seed was treated with a fungicide such as Dividend, improved seedling emergence significantly (Smiley et. al., 1996a,b) A recent study on various seed treatments had been conducted at the University of Georgia (Cumfer, 1998), with no effect on yield of wheat with seed treatments. Foliar fungicide applications did significantly affect wheat yields but was influenced by fungicide and timing of application. Only fungicide applications of Quadris, Folicur and Tilt had some influence on yield but was dependant on stage of growth and time of application. Little information on comparisons of seed treatments and foliar applications have been ascertained under North Florida growing conditions. Therefore, the objectives of the trial reported herein were i) to assess a fall seed treatment (Dividend) on wheat for control of diseases, ii) to compare foliar fungicide treatments for management of foliar diseases, and iii) to measure the interaction of nitrogen fertilization with fungicides and subsequent foliar diseases of wheat.

A new aerosol microphysical module MATRIX, the Multiconfiguration Aerosol TRacker of mIXing state, and its application in the Goddard Institute for Space Studies (GISS) climate model (ModelE) are described. This module, which is based on the quadrature method of moments (QMOM), represents nucleation, condensation, coagulation, internal and external mixing, and cloud-drop activation and provides aerosol particle mass and number concentration and particle size information for up to 16 mixed-mode aerosol populations. Internal and external mixing among aerosol components sulfate, nitrate, ammonium, carbonaceous aerosols, dust and sea-salt particles are represented. The solubility of each aerosol population, which is explicitly calculated based on its soluble and insoluble components, enables calculation of the dependence of cloud drop activation on the microphysical characterization of multiple soluble aerosol populations.A detailed model description and results of box-model simulations of various aerosol population configurations are presented. The box model experiments demonstrate the dependence of cloud activating aerosol number concentration on the aerosol population configuration; comparisons to sectional models are quite favorable. MATRIX is incorporated into the GISS climate model and simulations are carried out primarily to assess its performance/efficiency for global-scale atmospheric model application. Simulation results were compared with aircraft and station measurements of aerosol mass and number concentration and particle size to assess the ability of the new method to yield data suitable for such comparison. The model accurately captures the observed size distributions in the Aitken and accumulation modes up to particle diameter 1 μm, in which sulfate, nitrate, black and organic carbon are predominantly located; however the model underestimates coarse-mode number concentration and size, especially in the marine environment. This is more likely due to oversimplifications of the representation of sea salt emissions – sea salt emissions are only calculated for two size classes – than to inherent limitations of MATRIX.

Cotton (Gossypium hirsutum) fiber is sometimes affected by hardlock, which is characterized by a failure of the fiber to expand outward from the boll at maturity. Because affected fiber is inaccessible to mechanical harvesters, yield loss can be considerable. Hardlock has been linked to infection by Fusarium verticillioides. The involvement of flower thrips (Frankliniella spp.), which are commonly found in cotton flowers, was explored. At 1100 h, approximately 10% of cotton flowers contained thrips that were carrying F. verticillioides. The effect of thrips and/or Fusarium in flowers and bolls was explored under greenhouse conditions. Exposing flowers to Fusarium and thrips resulted in bolls with the most severe symptoms. Exposure to either Fusarium or thrips alone resulted in more hardlock than was noted in the control group. The impact of thrips was also evaluated under field conditions. Field plots were treated with insecticides, a fungicide, both, or left untreated. Insecticides reduced thrips numbers and reduced hardlock severity. The fungicide had no impact on thrips numbers and was less effective at reducing hardlock. Combining insecticide and fungicide applications was no more effective than using insecticides alone, although it more frequently increased yield. The untreated control plots generally had the most severe hardlock and lowest yields. Reducing hardlock severity resulted in higher yields, although not consistently. These studies suggest that thrips increase the severity of hardlock, and reducing their numbers may diminish hardlock severity.

Contemporary thinking encourages diversified cropping systems as a way to sustain crop yields, protect the environment, and increase wildlife habitat. This paper reviews the benefits of diversifying the traditional peanut ( Arachis hypogea L.) and cotton ( Gossypium hirsutum L.) production system to include perennial grasses such as bahiagrass ( Paspalum notatum Fluegge) and bermudagrass [ Cynodon dactylon (L.) Pers.] and incorporating cattle ( Bos taurus ) into the system. Perennial grasses improve soil quality by reducing soil erosion and nitrate (NO 3 ) leaching, increasing organic matter (OM) content, water infiltration rates, and the abundance and diversity of micro and macro flora and fauna. Cotton and peanut grown after perennial grasses are deeper rooted, have more vigorous growth, can better withstand pest pressure and environmental stresses, and often have higher yields. Including livestock in the cropping system makes more efficient use of climate and farm resources by extending the period of productive plant growth, improving economic returns, and reducing risk by diversifying the products available for sale.

An application of nitrogen (N) late in the season has the potential to increase yield and/or quality of wheat. The objective of this study was to use remote sensing data to quantify N stress in wheat and to monitor growth through an entire growing season. The circular, center-pivot study site was divided into four equal quarters. Each quarter was subdivided into four plots; each having a different N rate (0, 40, 100, and 130% of the farmer recommended N rate) applied to Westbred 936 hard red spring wheat. Two quarters of the pivot containing eight plots received no additional N, and the other two quarters received additional N estimated with remote sensing. Five randomly selected points in each plot were randomly selected for sampling. An empirical equation relating the Normalized Difference Vegetation Index (NDVI) values to the midseason nitrogen content of the wheat (flagleaf N) was used to quantify N deficiency for a midseason application. Supplemental N was applied at heading. Water was limiting during the growing season because of an Idaho power company buyback program. Harvest results showed significant differences in the yield between plots with N applied at midseason and those without any supplemental N, however, stress due most likely to lack of water linked to topography was the greatest source of yield variation. Yield was highly correlated with topography (R2 =0.92). Remote sensing can be an effective tool to quantify in-season N applications in hard red spring wheat.

Aerosol properties such as the number of particles that activate to form cloud drops and the mass contained within specified size ranges (as in the PM 2.5 and PM 10 regulatory standards) require integration over only part of the full size range of the particle distribution function (PDF) and may be formally expressed as integrals over kernels involving the Heaviside step function. Determination of these properties requires essentially that the size spectrum be partitioned into two (or more) portions, and poses a special challenge for aerosol modeling with the method of moments. To assess the ability of moment-based methods to treat kernels involving step functions, several algorithms for the estimation of aerosol properties associated with cloud activation have been evaluated. For 240 measured continental distributions employed here as test cases, the full size spectrum of the PDF was partitioned into three distinct portions based upon characteristic critical radii for activation in cumulus and stratiform clouds, and mass- and number-concentration metrics were evaluated for each portion. The first six radial moments yielded results accurate to within about 10% or better, on average, and the numbers of particles activated as cloud drops and the aerosol mass taken into cloud water were estimated to an accuracy of 5% or better. Of the moment-based approaches evaluated, the multiple isomomental distribution aerosol surrogate (MIDAS) (Wright, J. Aerosol Sci. 31 (2000) 1) technique performed best. Accurate results were also obtained with the randomized minimization search technique (RMST) (Yue et al., Geophys. Res. Lett. 24 (1997) 651; Heintzenberg et al., Appl. Opt. 20 (1981) 1308).

The greatest economic value from a corn (Zea mays L.) crop is obtained when it can be used as silage rather than for grain only. The objectives were to study tropical corn silage yield and quality in relation to starter fertilizer, planting date, corn hybrid, and fall armyworm stress. This study was conducted in the field a t Quincy and Jay, Florida during 1991 and 1992. Results have shown the interaction of tropical corn silage to starter fertilizer and hybrids. Pioneer X304C was a positive changer, DeKalh DK 9101 was a nochanger, and Pioneer 3099 and Cargill X70lTR were negative changers. In 1992, the fall armyworm migrated to Quincy 1month earlier than usual. Some hybrids were not as tolerant to the fall armyworm as others. Late-planted tropical corn resulted in high yields of corn silage. Feed quality 1% CP and in vitro organic matter digestibility (IVOMD)] of tropical corn grain and silage varied in relation to planting date and hybrid.

The Southeast U. S. farming community has been a region in transition for the last 15 years and has seen a continuous cycle of crops with the highest potential return. Low crop prices, yields, and uncertain weather led growers to change from a wheat/ soybean and corn system to cotton to rotate with peanuts. This required the development of an entire infrastructure system to support cotton along with special­ ized harvesting equipment. During this transition period, many growers went out of business or much of the farm land was planted to trees for long term investments as jobs were secured off farm. The challenges to agriculture today is to cut production costs while increasing yield to bring profit back to the farm since crop prices for most commodities have fallen by 25% or more during the last 15 years. Good management is required to produce better yields. Research during the last half of the 20 century shows the value of rotating cash crops with sod. By starting out farming with a high proportion of the farm in sod, less initial capitalization is required for small tractors and tillage equipment and yield of crops grown behind sod is often 50% or higher than continuously grown row crops. Research from Auburn, Florida and Georgia has shown the impacts of bahiagrass on pests, water infiltration, rooting depth, and subsequent yield of crops grown after bahiagrass. The main objection from growers is that it can’t work in their farming operations. A recently developed business model by the University of Florida shows that it is easily adapted to southern farms with or without livestock and becomes more profitable each year with total profits being 3 or 4 times higher after the system is fully implemented in the 4 year.

The quadrature method of moments (QMOM), a promising new tool for aerosol dynamics simulation, is extended to multicomponent, internally mixed particle populations. A new moment closure method, the Jacobian matrix transformation (JMT), is introduced and shown to provide an efficient procedure for evolving quadrature abscissas and weights directly and in closed form. For special growth laws where analytic results are available for comparison, the QMOM is also found to be exact. The JMT implementation of the QMOM is used to explore the asymptotic behavior of coagulating aerosols at long time. Nondimensional reduced moments are constructed, and found to evolve to constant values in excellent agreement with estimates derived from ‘self-preserving’ distributions previously obtained by independent methods. Our findings support the QMOM as a new tool for rapid, accurate simulation of the dynamics of an evolving internally mixed aerosol population, including the approach to asymptotic behavior at long time, in terms of lower-order moments.

Atmospheric aerosols, suspensions of solid or liquid particles, are an important multi-phase system. Aerosols scatter and absorb shortwave (solar) radiation, affecting climate (Charlson et al., 1992; Schwartz, 1996) and visibility; nucleate cloud droplet formation, modifying the reflectivity of clouds (Twomey et al., 1984; Schwartz and Slingo, 1996) as well as contributing to composition of cloudwater and to wet deposition (Seinfeld and Pandis, 1998); and affect human health through inhalation (NRC, 1998). Existing and prospective air quality regulations impose standards on concentrations of atmospheric aerosols to protect human health and welfare (EPA, 1998). Chemical transport and transformation models representing the loading and geographical distribution of aerosols and precursor gases are needed to permit development of effective and efficient strategies for meeting air quality standards, and for examining aerosol effects on climate retrospectively and prospectively for different emissions scenarios. Important aerosol properties and processes depend on their size distribution: light scattering, cloud nucleating properties, dry deposition, and penetration into airways of lungs. The evolution of the mass loading itself depends on particle size because of the size dependence of growth and removal processes. For these reasons it is increasingly recognized that chemical transport and transformation models must represent not just the mass loading of atmospheric particulate matter but also the aerosol microphysical properties and the evolution of these properties if aerosols are to be accurately represented in these models. If the size distribution of the aerosol is known, a given property can be evaluated as the integral of the appropriate kernel function over the size distribution. This has motivated the approach of determining aerosol size distribution, and of explicitly representing this distribution and its evolution in chemical transport models.

We extendthe application of moment methods to multivariate suspended particle population problems-those for which size alone is insufficient to specify the state of a particle in the population. Specifically, a bivariate extension of the quadrature method of moments (QMOM) (R. McGraw, Aerosol Sci. Technol. 27, 255 (1997)) is presented for efficiently modeling the dynamics of a population of inorganic nanoparticles undergoing simultaneous coagulation and particle sintering. Continuum regime calculations are presented for the Koch-Friedlander-Tandon-Rosner model, which includes coagulation by Brownian diffusion (evaluated for particle fractal dimensions, D(f), in the range 1.8-3) and simultaneous sintering of the resulting aggregates (P. Tandon and D. E. Rosner, J. Colloid Interface Sci. 213, 273 (1999)). For evaluation purposes, and to demonstrate the computational efficiency of the bivariate QMOM, benchmark calculations are carried out using a high-resolution discrete method to evolve the particle distribution function n(nu, a) for short to intermediate times (where nu and a are particle volume and surface area, respectively). Time evolution of a selected set of 36 low-order mixed moments is obtained by integration of the full bivariate distribution and compared with the corresponding moments obtained directly using two different extensions of the QMOM. With the more extensive treatment, errors of less than 1% are obtained over substantial aerosol evolution, while requiring only a few minutes (rather than days) of CPU time. Longer time QMOM simulations lend support to the earlier finding of a self-preserving limit for the dimensionless joint (nu, a) particle distribution function under simultaneous coagulation and sintering (Tandon and Rosner, 1999; D. E. Rosner and S. Yu, AIChE J., 47 (2001)). We demonstrate that, even in the bivariate case, it is possible to use the QMOM to rapidly model the approach to asymptotic behavior, allowing an immediate assessment of when previously established asymptotic results can be applied to dynamical situations of current/future interest. Copyright 2001 Academic Press.

We describe and evaluate a six-moment aerosol microphysical module, 6M, designed for implementation in atmospheric chemical transport models (CTMs). The module 6M is based upon the quadrature method of moments (QMOM) [McGraw, 1997] and the multiple isomomental distribution aerosol surrogate (MIDAS) method [Wright, 2000]. The module 6M evolves the lowest six radial moments of H2SO4-H2O aerosols for a comprehensive set of dynamical processes including the formation of new particles via binary H2SO4-H2O nucleation, condensational growth, coagulation, evolution due to cloud processing, size-resolved dry deposition, and water uptake and release with changing relative humidity. Performance of the moment-based aerosol evolution is examined and evaluated by comparison with results obtained using a high-resolution discrete model of the particle dynamics for a range of conditions representative of the boundary layer and lower troposphere. Overall, the performance of 6M is good relative to uncertainties associated with other processes represented in CTMs for the 30 test cases evaluated. Differences between 6M and the discrete model in the mass/volume moment and in the partitioning of sulfur (VI) between the gas and aerosol phases remain under 1% whenever significant, aerosol is present, and differences in particle number rarely exceed 15%. Estimates of cloud droplet number from 6M are on average within 16% of those of the discrete model, with a significant part,of these differences attributable to limitations of the discrete dynamics. Multimodal lognormal (MIDAS) surrogates to the underlying size distributions derived from the 6M moments are in good agreement with the benchmark size distributions.

We describe new developments in the application of the Quadrature Method of Moments (QMOM) [1]. These include the first application of the QMOM in a 3-D chemical transformation and transport model on the sub-hemispheric scale [2]. The QMOM simultaneously tracks an arbitrary (even) number of moments of a particle size distribution directly in space and time without the need for explicitly representing the distribution itself. The present implementation evolves the six lowest-order radial moments for each of several externally-mixed aerosol populations. From these moments we report modeled geographic distributions of several aerosol properties, including a shortwave radiative forcing obtained using the Multiple Isomomental Distribution Aerosol Surrogate (MIDAS) technique [3]. These results demonstrate the capabilities of these moment-based techniques to simultaneously represent aerosol nucleation, condensation, coagulation, dry deposition, wet removal, cloud activation, and transport processes in a large-scale model, and to yield aerosol optical properties and radiative influence from the modeled aerosol moments. We report on recent extensions of the method for simulation of internal mixtures and generally-mixed aerosols, and on a bivariate extension of the QMOM for modeling simultaneous coagulation and sintering of particle populations [4].

This letter describes the first application of the Quadrature Method of Moments (QMOM) [McGraw, 1997] in a 3‐D chemical transformation and transport model. The QMOM simultaneously tracks an arbitrary (even) number of moments of a particle size distribution directly in space and time without the need for explicitly representing the distribution itself. The host 3‐D model, the Global Chemistry Model driven by Observation‐derived meteorological data (GChM‐O), has been previously described [Benkovitz et al., 1994]. The present implementation evolves the six lowest‐order radial moments for each of several externally‐mixed aerosol populations. From these moments we report modeled geographic distributions of several aerosol properties, including a shortwave radiative forcing obtained using the Multiple Isomomental Distribution Aerosol Surrogate (MIDAS) technique [Wright, 2000]. These results demonstrate the capabilities of these moment‐based techniques to simultaneously represent aerosol nucleation, condensation, coagulation, dry deposition, wet removal, cloud activation, and transport processes in a large scale model, and to yield aerosol optical properties and radiative influence from the modeled aerosol.

A technique is described for efficient retrieval of families of smooth model distributions, such as lognormals or modified gammas, from the lower moments of the particle size distribution from which aerosol optical properties can be accurately computed. The Multiple Isomomental Distribution Aerosol Surrogate (MIDAS) technique, along with the quadrature technique of McGraw et al. (1995 Geophys. Res. Lett. 22, 2929–2932), is evaluated by computing the extinction efficiency, asymmetry parameter, backscatter fraction, 180° backscattering cross section, upscatter fraction, mass scattering efficiency, and a direct shortwave forcing at 8 wavelengths for 28 test distributions derived from field observations of marine, continental, urban and stratospheric aerosols. For the 224 single wavelength evaluations with retrieved modified gammas the average magnitude of error for each of the computed optical properties was 2% or less, with the exception of the 180° backscattering cross section (4%), establishing the accuracy of the technique. It is concluded that this approach is useful for obtaining aerosol optical properties from the first 6 moments of the size distribution, permitting confident determination of these properties from models in which aerosol evolution is represented by evolution of the lower-order moments.