Showing papers by "Mississippi State University published in 2002"

Past, present, and future of decision support technology

Abstract: Since the early 1970s, decision support systems (DSS) technology and applications have evolved significantly. Many technological and organizational developments have exerted an impact on this evolution. DSS once utilized more limited database, modeling, and user interface functionality, but technological innovations have enabled far more powerful DSS functionality. DSS once supported individual decision-makers, but later DSS technologies were applied to workgroups or teams, especially virtual teams. The advent of the Web has enabled inter-organizational decision support systems, and has given rise to numerous new applications of existing technology as well as many new decision support technologies themselves. It seems likely that mobile tools, mobile e-services, and wireless Internet protocols will mark the next major set of developments in DSS. This paper discusses the evolution of DSS technologies and issues related to DSS definition, application, and impact. It then presents four powerful decision support tools, including data warehouses, OLAP, data mining, and Web-based DSS. Issues in the field of collaborative support systems and virtual teams are presented. This paper also describes the state of the art of optimization-based decision support and active decision support for the next millennium. Finally, some implications for the future of the field are discussed.

The Link Between Corporate Social and Financial Performance: Evidence from the Banking Industry

Abstract: The purpose of this investigation is to extend earlier research on the relationship between corporate social and financial performance. The unique contribution of the study is the empirical analysis of a sample of companies from the banking industry and the use of Community Reinvestment Act ratings as a social performance measure. The empirical analysis solidly supports the hypothesis that the link between social and financial performance is positive.

Encouraging Citizen Adoption of E-Government by Building Trust

Abstract: The growing interest in e-Government raises the question of how governments can increase citizen adoption and usage of their online government services. e-Government becomes especially important given its potential to reduce costs and improve service compared with alternative traditional modes. Citizen trust is proposed to be an important catalyst of e-Government adoption. By investigating online tax services, already available and used extensively in the West, we propose several ways in which governments can increase citizen trust and thus encourage the adoption of this new and potentially significant mode of government service. The proposed e-Government adoption model also takes in account issues of cultural variables, risk, control and technology acceptance.Institution-based trust, such as an independent judicial system with appropriate legal powers, is proposed to be the major tactic to build trust in e-Government. In addition, among new users of online government services, characteristic-based and cognitive-based antecedents should be crucial; general psychological dispositions and knowledge of the process should also engender trust. Among experienced users, on the other hand, it is suggested that the nature of previous interactions with the e-Government system should be the major predictor of trust, and hence of continued use. These propositions are elucidated, as they apply to different cultures and to high-intrusive versus low-intrusive government services. This study has practical implications for the design of mechanisms for the adoption of e-Government.

Dimensionality reduction of hyperspectral data using discrete wavelet transform feature extraction

Abstract: In this paper, the dyadic discrete wavelet transform is proposed for feature extraction from a high-dimensional data space. The wavelet's inherent multiresolutional properties are discussed in terms related to multispectral and hyperspectral remote sensing. Furthermore, various wavelet-based features are applied to the problem of automatic classification of specific ground vegetations from hyperspectral signatures. The wavelet transform features are evaluated using an automated statistical classifier. The system is tested using hyperspectral data for various agricultural applications. The experimental results demonstrate the promising discriminant capability of the wavelet-based features. The automated classification system consistently provides over 95% and 80% classification accuracy for endmember and mixed-signature applications, respectively. When compared to conventional feature extraction methods, the wavelet transform approach is shown to significantly increase the overall classification accuracy.

Optimizing learning from examples using animated pedagogical agents.

Abstract: This study attempted to optimize a computer-based learning environment designed to teach learners how to solve word problems by incorporating an animated pedagogical agent. The agent was programmed to deliver instructional explanations either textually or aurally, while simultaneously using gaze and gesture to direct the learners to focus their attention on the relevant part of the example. In Experiment 1, learners presented with an agent delivering explanations aurally (voice plus agent) outperformed their control peers on measures of transfer. In Experiment 2, learners in the voice-plus-agent condition outperformed their peers presented with textual explanations on a variety of measures, including far transfer. In sum, an animated agent programmed to deliver instructions aurally can help optimize learning from examples. A worked example is an instructional device that provides a model for solving a particular type of problem by presenting the solution in a step-by-step fashion. It is intended to provide the learner with an expert’s solution, which the learner can use as a model for his or her own problem solving. To date, in most experiments, worked examples have been visually fixed; that is, the examples simultaneously presented a problem and an expert’s solution steps. As such, these worked examples are similar to those found in traditional mathematics and science texts; however, instructional materials delivered on multimedia computer systems need not be limited in this way. For example, Stark (1999) and Renkl (1997) suggested that example processing can be enhanced by sequentially presenting problem states. According to Stark and Renkl, this type of presentation encourages learners to explain the examples to themselves by anticipating the next step in an example solution, then checking to determine whether the predicted step corresponded to the actual step—a phenomenon Renkl termed anticipative reasoning. According to Catrambone (1994, 1996, 1998), worked examples should be structured so they emphasize conceptually related solution steps (i.e., subgoals) by visually isolating them, by labeling them, or both. With regard to presenting examples that require learners to reference multiple sources of information, Mousavi and his colleagues (Mousavi, Low, & Sweller, 1995) offer a simple solution: Some segments of instructional information should be presented visually, whereas other segments should be presented aurally (i.e., mixed-mode format). One advantage of using the computer to deliver instruction is that it enables instructional designers to combine multiple instructional principles or components in a worked example, which may prove to enhance its efficacy. According to Mayer’s (1997) generative theory of multimedia learning, computers—in contrast to a book-based medium—also provide a more favorable environment in which to implement some forms of effective instruction, such as the coordination of the visual presentation of sequential problem states with an auditory description of each of those states. For example, in Atkinson and Derry (2000), one way to structure an example within a computer-based multimedia environment so that learning can be maximized was to create a multicomponent worked example that (a) was sequential, in that it consisted of a sequential presentation of problem states; (b) was constructed to emphasize problem subgoals (i.e., it is subgoal oriented); and (c) incorporated a second modality that is coordinated with the sequential presentation of problem states (i.e., visually presented steps coupled with verbal instructional explanations). Learners exposed to these sequential, subgoal-oriented (SE–SO) examples with dual modes outperformed learners who were exposed to more traditional, simultaneous, non-subgoal-oriented examples on conceptually based measures of problem-solving transfer. Moreover, this difference occurred despite the fact that the examples in the latter condition were also dual mode.

Potential use of chitosan as a cell scaffold material for cartilage tissue engineering.

Abstract: One of the most important factors in any tissue-engineering application is the cell substrate. The purpose of this study was the initial evaluation of chitosan, a derivative of the abundant, naturally occurring biopolymer chitin, as a cell scaffold for cartilage tissue engineering. Chitosan scaffolds having an interconnecting porous structure were easily fabricated by simple freezing and lyophilization of a chitosan solution. After rehydration of scaffolds, porcine chondrocytes were seeded onto scaffolds and cultured for up to 28 days in a rotating-wall bioreactor. Chitosan scaffolds supported cell attachment and maintenance of a rounded cell morphology. After 18 days, cells within the scaffolds had synthesized extracellular matrix in which proteoglycan and type II collagen were detected by toluidine blue staining and immunohistochemistry, respectively. Abundant extracellular matrix was found almost exclusively in the periphery of the scaffolds, as scaffold microstructure prevented cells from penetrating to interior regions. Nonetheless, the results suggest that chitosan scaffolds may be a useful alternative to synthetic cell scaffolds for cartilage tissue engineering.

From Example Study to Problem Solving: Smooth Transitions Help Learning

Abstract: Research has shown that it is effective to combine example study and problem solving in the initial acquisition of cognitive skills. Present methods for com bining these learning modes are static, however, and do not support a transition from example study in early stages of skill acquisition to later problem solving. Against this background, the authors proposed a successive integration of problem-solving elements into example study until the learners solved problems on their own (i.e., complete example -? increasingly more incomplete examples ?> problem to-be solved). The authors tested the effectiveness of such a fading procedure against the traditional method of using example-problem pairs. In a field experiment and in 2 more controlled laboratory experiments, the authors found that (a) the fading pro cedure fosters learning, at least when near transfer performance is considered; (b) the number of problem-solving errors during learning plays a role in mediating this effect; and (c) it is more favorable to fade out worked-out solution steps in a back ward manner (omitting the last solution steps first) as compared with a forward manner (omitting the first solution steps first).

Industrial age anthropogenic inputs of heavy metals into the pedosphere

Abstract: Heavy metals have been increasingly released into our environment. We present here, for the first time, the global industrial age production of Cd, Cu, Cr, Hg, Ni, Pb, and Zn, and their potential accumulation and environmental effects in the pedosphere. World soils have been seriously polluted by Pb and Cd and slightly by Zn. The potential industrial age anthropogenic Pb, Hg, and Cd inputs in the pedosphere are 9.6, 6.1, and 5.2 times those in the lithosphere, respectively. The potential anthropogenic heavy metal inputs in the pedosphere increased tremendously after the 1950s, especially for Cr and Ni. In 2000, the cumulative industrial age anthropogenic global production of Cd, Cr, Cu, Hg, Ni, Pb, and Zn was 1.1, 105, 451, 0.64, 36, 235, and 354 million tonnes, respectively. The global industrial age metal burdens per capita (in 2000) were 0.18, 17.3, 74.2, 0.10, 5.9, 38.6, and 58.2 kg for Cd, Cr, Cu, Hg, Ni, Pb, and Zn, respectively. Acidification may increase the bioavailability and toxicity of heavy metals in the pedosphere. The improvement of industrial processing technology reducing the metal dispersion rate, the recycling of metal-containing outdated products, by-products and wastes, and the development of new substitute materials for heavy metals are possible strategies to minimize the effects of heavy metals on our environment.

The Only Child and Educational Opportunity for Girls in Urban China

Abstract: Using data from the authors' 1998-99 survey of 1,040 eighth graders in Wuhan, China, this study explores the differences between single-girl and single-boy families with regard to parental expectation and investment in children's education, children's own educational aspirations, and mathematics performance. The authors found that contrary to the known intrafamily discrimination against girls common among families of pre-one-child generations and still common among contemporary rural families with more than one child, there are no gender differences related to education between single-girl and single-boy families in modern urban China. The authors found equally high educational aspirations and similar mathematical performance for male and female only children. They suggest that this gender equality in education is an unintended consequence of the one-child-per-family policy and that under China's current social and economic conditions, girls are better off living in one-child families in the big cities of...

Fuzzy data mining and genetic algorithms applied to intrusion detection

Abstract: We are developing a prototype intelligent intrusion detection system (IIDS) to demonstrate the effectiveness of data mining techniques that utilize fuzzy logic and genetic algorithms. This system combines both anomaly based intrusion detection using fuzzy data mining techniques and misuse detection using traditional rule-based expert system techniques. The anomaly-based components are developed using fuzzy data mining techniques. They look for deviations from stored patterns of normal behavior. Genetic algorithms are used to tune the fuzzy membership functions and to select an appropriate set of features. The misuse detection components look for previously described patterns of behavior that are likely to indicate an intrusion. Both network traffic and system audit data are used as inputs for both components.

Molecular structures and associations of humic substances in the terrestrial environment

Abstract: Here we show, for the first time, evidence of the primary molecular structures in humic substances (HS), the most abundant naturally occurring organic molecules on Earth, and their associations as mixtures in terrestrial systems. Multi-dimensional nuclear magnetic resonance (NMR) experiments show us that the major molecular structural components in the mixtures operationally defined as HS are aliphatic acids, ethers, esters and alcohols; aromatic lignin derived fragments; polysaccharides and polypeptides. By means of diffusion ordered spectroscopy, distinct diffusion coefficients consistent with relatively low molecular weight molecules were observed for all the components in the mixtures, and saccharides were the largest single class of component present. Liquid chromatography NMR confirmed that HS components can be easily separated and nuclear Overhauser effect (NOE) enhancements support the finding that the components are of relatively low molecular weight <~2,000 Da. The widely recognized properties of HS, i.e., characteristics indicative of crosslinked, macromolecular networks, can now be explained as aggregation of mixtures, most likely instigated by complexation with metal cations.

Eogenetic karst from the perspective of an equivalent porous medium

Abstract: The porosity of young limestones experiencing meteoric diagenesis in the vicinity of their deposition (eogenetic karst) is mainly a double porosity consisting of touching-vug channels and preferred passageways lacing through a matrix of interparticle porosity. In contrast, the porosity of limestones experiencing subaerial erosion following burial diagenesis and uplift (telogenetic karst) is mainly a double porosity consisting of conduits within a network of fractures. The stark contrast between these two kinds of karst is illustrated by their position on a graph showing the hydraulic characteristics of an equivalent porous medium consisting of straight, cylindrical tubes (n-D space, where n is porosity,D is the diameter of the tubes, and logn is plotted against logD). Studies of the hydrology of small carbonate islands show that large-scale, horizontal hydraulic conductivity (K) increases by orders of magnitude during the evolution of eogenetic karst. Earlier petrologic studies have shown there is little if any change in the total porosity of the limestone during eogenetic diagenesis. The limestone of eogenetic karst, therefore, tracks horizontally inn-D space. In contrast, the path from initial sedimentary material to telogenetic karst comprises a descent on the graph with reduction ofn during burial diagenesis, then a sideways shift with increasingD due to opening of fractures during uplift and exposure, and finally an increase inD andn during development of the conduits along the fractures. Eogenetic caves are mainly limited to boundaries between geologic units and hydrologic zones: stream caves at the contact between carbonates and underlying impermeable rocks (and collapse-origin caves derived therefrom); vertical caves along platform-margin fractures; epikarst; phreatic pockets (banana holes) along the water table; and flank margin caves that form as mixing chambers at the coastal freshwater-saltwater “interface”. In contrast, the caverns of telogenetic karst are part of a system of interconnected conduits that drain an entire region. The eogenetic caves of small carbonate islands are, for the most part, not significantly involved in the drainage of the island.

A simple confidence interval for meta-analysis

Abstract: In the context of a random effects model for meta-analysis, a number of methods are available to estimate confidence limits for the overall mean effect. A simple and commonly used method is the DerSimonian and Laird approach. This paper discusses an alternative simple approach for constructing the confidence interval, based on the t-distribution. This approach has improved coverage probability compared to the DerSimonian and Laird method. Moreover, it is easy to calculate, and unlike some methods suggested in the statistical literature, no iterative computation is required.

Insect feeding mobilizes a unique plant defense protease that disrupts the peritrophic matrix of caterpillars

Abstract: Plants frequently respond to herbivorous insect attack by synthesizing defense proteins that deter insect feeding and prevent additional herbivory. Maize (Zea mays L.) lines, resistant to feeding by a number of lepidopteran species, rapidly mobilize a unique 33-kDa cysteine protease in response to caterpillar feeding. The accumulation of the 33-kDa cysteine protease in the maize mid-whorl was correlated with a significant reduction in caterpillar growth that resulted from impaired nutrient utilization. Black Mexican Sweetcorn callus transformed with mir1, the gene encoding the 33-kDa cysteine protease, expressed the protease and growth of caterpillars reared on the transgenic callus was reduced 60-80%. Scanning electron microscopy was used to examine the effect of plant material expressing the 33-kDa cysteine protease on the structure of the caterpillar peritrophic matrix. Because the peritrophic matrix surrounds the food bolus, assists in digestive processes, and protects the caterpillar midgut from physical and chemical damage, disruption of peritrophic matrix may reduce caterpillar growth. The results indicated that the peritrophic matrix was severely damaged when caterpillars fed on resistant maize plants or transgenic Black Mexican Sweetcorn. The accumulation of the 33-kDa cysteine protease in response to caterpillar feeding, and its ability to damage the insect peritrophic matrix, represents an unusual host-plant resistance mechanism that may have applications in agricultural biotechnology.

Dietary Oligofructose and Inulin Protect Mice from Enteric and Systemic Pathogens and Tumor Inducers

Abstract: Prebiotics induce changes in the population and metabolic characteristics of the gastrointestinal bacteria, modulate enteric and systemic immune functions, and provide laboratory rodents with resistance to carcinogens that promote colorectal cancer. There is less known about protection from other challenges. Therefore, mice of the B6C3F1 strain were fed for 6 wk a control diet with 100 g/kg cellulose or one of two experimental diets with the cellulose replaced entirely by the nondigestible oligosaccharides (NDO) oligofructose and inulin. From each diet, 25 mice were challenged by a promoter of colorectal cancer (1,2-dimethylhydrazine), B16F10 tumor cells, the enteric pathogen Candida albicans (enterically), or were infected systemically with Listeria monocytogenes or Salmonella typhimurium. The incidences of aberrant crypt foci in the distal colon after exposure to dimethylhdrazine for mice fed inulin (53%) and oligofructose (54%) were lower than in control mice (76%; P 80% for control mice), but fewer of the mice fed inulin died (60%; P < 0.05), with mice fed oligofructose again intermediate. The mechanistic basis for the increased resistance provided by dietary NDO was not elucidated, but the findings are consistent with enhanced immune functions in response to changes in the composition and metabolic characteristics of the bacteria resident in the gastrointestinal tract.

Technology Integration: Closing the Gap Between What Preservice Teachers are Taught To Do and What They Can Do

Abstract: The digital divide exists not only between those who have technology and those who do not. A gap also exists between what we teach preservice teachers about technology and what we expect them to do with technology as classroom teachers. This gap is easily seen between the knowledge and skills preservice teachers have acquired through the required technology course, and the knowledge and skills they are expected to possess to successfully integrate technology in their elementary methods classes. This study was conducted with a group of 26 self-selected preservice teachers to examine this gap between teaching the use of technology and the use of technology in learning to teach. The study investigated whether the integration of technology practices into the elementary method courses for preservice teachers would positively influence their self-reported confidence levels in integrating specific technologies in elementary classrooms. Teaching preservice teachers how to integrate specific technologies into their teaching methods helped increase their level of confidence. The findings indicated that the opportunity for preservice teachers to be exposed to the technologies while learning teaching practices in their method courses and to see the technologies modeled by the faculty increased the preservice teachers' confidence level. TECHNOLOGY IN PRESERVICE EDUCATION The past three decades have brought an increased use of technology in many sectors of society. However, the integration of technology into the teaching methods and practices of elementary school teachers has not been fully implemented. Technology equipment and software have arrived in school districts across the nation through sources such as federal funding received through government sponsored grants and through partnerships with major corporations. The influx of technology into the schools has also created a challenge for many higher-education teacher preparation programs. By the year 2008, it has been projected that the K-12 schools will hire approximately two million new teachers (Gerald & Williams, 1998). This increase in the number of new teachers places a burden on colleges and universities to address the technological needs of these new preservice teachers. Colleges of Education must be proactive in implementing teacher education programs that integrate technology through the entire teacher education program by providing opportunities for preservice teachers to observe the modeling of effective uses of technology by faculty and to use this technology and software in a supportive environment (Hill & Somers, 1996). Yet, the Office of Technology Assessment (OTA, 1995) noted that most teachers who graduate from teacher education programs do so with an inadequate knowledge of how they can implement technology into their teaching practices. Although most teacher education graduates reported that they were prepared to use basic programs such as drill and practice, tutorials, or writing software, only 1 in 10 believed that they could use more advanced programs such as electronic presentations or problem-solving software. These teachers also reported that they developed lesson plans or teaching materials for technology use in the classroom on a very limited basis. The report issued by OTA revealed that, "Overall teacher education programs in the United States do not prepare graduates to use technology as a teaching tool" (p. 184). A study completed by the National Center for Education Statistics (1999) also found that educators reported technology was important to the educational system's reform. However, only 20% of the teachers believed they were prepared to integrate technology into classroom instructional practices. Trotter (1999) reported on another study conducted by the International Society for Technology in Education (ISTE) which surveyed 416 colleges of education and found that the future graduates of these programs were not receiving the experiences they needed to effectively integrate technology. …

Ablation, mechanical and thermal conductivity properties of vapor grown carbon fiber/phenolic matrix composites

Abstract: The ablation, mechanical and thermal properties of vapor grown carbon fiber (VGCF) (Pyrograf III™ Applied Sciences, Inc.)/phenolic resin (SC-1008, Borden Chemical, Inc.) composites were evaluated to determine the potential of using this material in solid rocket motor nozzles. Composite specimens with varying VGCF loadings (30–50% wt.) including one sample with ex-rayon carbon fiber plies were prepared and exposed to a plasma torch for 20 s with a heat flux of 16.5 MW/m 2 at approximately 1650°C. Low erosion rates and little char formation were observed, confirming that these materials were promising for rocket motor nozzle materials. When fiber loadings increased, mechanical properties and ablative properties improved. The VGCF composites had low thermal conductivities (approximately 0.56 W/m-K) indicating they were good insulating materials. If a 65% fiber loading in VGCF composite could be achieved, then ablative properties are projected to be comparable to or better than the composite material currently used on the Space Shuttle Reusable Solid Rocket Motor (RSRM).

Efficient adder circuits based on a conservative reversible logic gate

Abstract: Conservative and reversible logic gates are widely known to be compatible with revolutionary computing paradigms such as optical and quantum computing. A fundamental conservative reversible logic gate is the Fredkin gate. This paper presents efficient adder circuits based on the Fredkin gate. Novel full adder circuits using Fredkin gates air proposed which have lower hardware complexity than the current state-of-the-art, while generating the additional signals required for carry skip adder architectures. The traditional ripple carry adder and several carry skip adder topologies are compared. Theoretical performance of each adder is determined and compared. Although the variable sized block carry skip adder is determined to have shorter delay than the fixed block size carry skip adder, the performance gains are not sufficient to warrant the required additional hardware complexity.

Narrow-waveband reflectance ratios for remote estimation of nitrogen status in cotton.

Abstract: Tailoring nitrogen (N) fertilizer applications to cotton (Gossypium hirsutum L.) in response to leaf N status may optimize N use efficiency and reduce off-site effects of excessive fertilizer use. This study compared leaf and canopy reflectance within the 350 to 950 nm range in order to identify reflectance ratios sensitive to leaf chlorophyll (Chl), and hence N status, in cotton. Plants were grown outdoors in large pots using half-strength Hoagland's (control) solution until some three-row plots received a restricted supply of N. Treatments comprised control, 20% of control N at first flower bud (square) onward; 0 and 20% of control N at first flower onward; and 0% of control N at fruit-filling onward. Despite leaf N values ranging from 51 to 19 g kg-1 across treatments and sampling dates, a weak correlation was obtained between Chl and N (r2 = 0.32, df = 70). In general, N stress led to increased reflectance at 695 +/- 2.5 nm (R695) and decreased reflectance at R410, and changes in leaf N were best correlated with either R695 or R755 in leaves and either R410 or R700 in canopies. The strongest associations between leaf constituent and canopy reflectance ratio were Chl vs. R415/R695 (r2 = 0.72), carotenoids vs. R415/R685 (r2 = 0.79), and N vs. R415/R710 (r2 = 0.70). The R415 measure appears to be a more stable spectral feature under N stress, as compared with more pronounced changes along the reflectance red edge (690-730 nm). Multiple regression identified a three-waveband canopy reflectance model that explained 80% of the variability in leaf N. Results indicate that remote sensing of N status in cotton is feasible using narrow-waveband reflectance ratios that involve the violet or blue region of the spectrum (400 to 450 nm) and the more commonly featured red-edge region.

Robustness to Non-Normality of the Multivariate EWMA Control Chart

Abstract: The effects of non-normality on the statistical performance of the multivariate exponentially moving average (MEWMA) control chart, and the Hotelling chi-squared chart in particular, is investigated when used in individual observations to monitor the me..

Aflatoxin and fumonisin contamination of commercial corn (Zea mays) hybrids in Mississippi.

Abstract: Resistance to mycotoxin contamination was compared in field samples harvested from 45 commercial corn (maize) hybrids and 5 single-cross aflatoxin-resistant germplasm lines in years with high and moderate heat stress. In high heat stress, mycotoxin levels were (4.34 +/- 0.32) x 10(3) microg/kg [(0.95-10.5 x 10(3) microg/kg] aflatoxins and 11.2 +/- 1.2 mg/kg (0-35 mg/kg) fumonisins in commercial hybrids and 370 +/- 88 microg/kg (140-609 microg/kg) aflatoxins and 4.0 +/- 1.3 mg/kg (1.7-7.8 mg/kg) fumonisins in aflatoxin-resistant germplasm lines. Deoxynivalenol was detected (one-fourth of the samples, 0-1.5 mg/kg), but not zearalenone. In moderate heat stress, mycotoxin levels were 6.2 +/- 1.6 microg/kg (0-30.4 microg/kg) aflatoxins and 2.5 +/- 0.2 mg/kg (0.5-4.8 mg/kg) fumonisins in commercial hybrids and 1.6 +/- 0.7 microg/kg (0-7 microg/kg) aflatoxins and 1.2 +/- 0.2 mg/kg (0.5-3.0 mg/kg) fumonisins in aflatoxin-resistant germplasm lines. The results are consistent with heat stress playing an important role in the susceptibility of corn to both aflatoxin and fumonisin contamination, with significant reductions of both aflatoxins and fumonisins in aflatoxin-resistant germplasm lines.

Community Structure and Functional Dynamics of Benthic Microalgae in Salt Marshes

Abstract: Benthic microalgae are a ubiquitous feature in sediments directly exposed to full sunlight or shaded by a vascular plant canopy in coastal salt marshes. Diatoms, cyanobacteria, and green algae are the dominant groups. Of these, diatoms are universally present and abundant, exhibit migratory rhythms driven mainly by light, and are by far the taxonomically most diverse group. Dense mats of cyanobacteria and secondarily green algae frequently develop where light levels are high. The more abundant species of all three algal groups are widely distributed within and among salt marshes of the United States and Europe. Standing crops of benthic microalgae beneath various vascular plant canopies exhibit mean annual values of 60 to 160 mg chl a m−2. Annual benthic microalgal production (BMP) has been shown to range from 28 g C m−2 y−1 beneath Juncus roemerianus to 314 g C m−2 y−1 beneath Jaumea carnosa. In general, BMP increases in a southerly direction in Atlantic coast marshes but is lowest in Gulf Coast marshes. In Atlantic and southern California marshes a significant portion of benthic microalgal production occurs when the overstory vascular plants are dormant. Experimental manipulations have shown that BMP and biomass beneath Spartina alterniflora are limited by nitrogen supplies and grazing activities. Manipulation of light appears to primarily affect the relative dominance of diatoms and cyanobacteria in the benthic microalgal assemblage. The ratio of annual BMP to net aerial production of the overstory vascular plant canopy is 10 to 60% in Atlantic and Gulf Coast marshes and 75 to 140% in a southern California marsh. The benthic microalgal portion of this two component productivity system has been shown by multiple stable isotope studies to be a major component of salt marsh food webs. Diatoms, in particular, are the preferred food item of a diverse array of invertebrate and fish species.

Diffusive logistic equation with constant yield harvesting, I: Steady states

Abstract: We consider a reaction-diffusion equation which models the constant yield harvesting to a spatially heterogeneous population which satisfies a logistic growth. We prove the existence, uniqueness and stability of the maximal steady state solutions under certain conditions, and we also classify all steady state solutions under more restricted conditions. Exact global bifurcation diagrams are obtained in the latter case. Our method is a combination of comparison arguments and bifurcation theory.

Preterm Birth Affects the Intestinal Response to Parenteral and Enteral Nutrition in Newborn Pigs

Abstract: Maturation of gastrointestinal (GI) function in neonates is stimulated by enteral nutrition, whereas parenteral nutrition induces GI atrophy and malfunction. We investigated whether preterm birth alters the GI responses to parenteral and enteral nutrition. Pigs were delivered either preterm (107 d gestation) or at term (115 d gestation) and fed total parenteral nutrition (TPN) or enteral sow's milk (ENT) for 6 d after birth. Immaturity of the preterm pigs was documented by reduced blood pH, oxygen saturation and neutrophil granulocyte function, impaired intestinal immunoglobulin G uptake from colostrum, and altered relative weights of visceral organs (small intestine, liver, spleen, pancreas, and adrenals). For both ages at delivery, increases occurred in pancreatic weight (30-75%) and amylase activity (0.5- to 13-fold) after birth, but much more in ENT than in TPN pigs (P < 0.05). Six days of TPN feeding was associated with reduced intestinal weight for both delivery groups (60% of values in ENT, P < 0.001), but only in term TPN pigs was the weight lower than at birth (-20%, P < 0.05). Likewise, it was only in term TPN pigs that intestinal maltase activity increased, compared with ENT, and the absorption of glucose and proline decreased. Only in preterm pigs did TPN feeding increase lactase activity (+50% compared with ENT, P < 0.05). For both delivery ages, the mRNA of lactase-phloridzin hydrolase and sodium-coupled glucose transporter 1 were increased in TPN, compared with ENT. In conclusion, the trophic effect of enteral vs. parenteral nutrition on the GI tract is also present after preterm birth, but the postnatal maturation of many GI functions is modified, compared with term birth. The effects of nutritional regimen on the maturation of the gut epithelium in neonates depend on gestational age at birth.