Photolytic demethylation of monuron and demethylmonuron in aqueous solution

Photochemical demethylation of monuron [3-(4-chlorophenyl)-1, 1-dimethylurea] and of demethylmonuron [ 1-(4-chlorophenyl)-3-methylurea] in aqueous solution was investigated. The photoproducts identified in this study were formaldehyde, formic acid and carbon dioxide. These products indicate that demethylation occurs either by oxidation of a methyl group to hydroxymethyl which is readily cleaved to yield formaldehyde, or by further oxidation to an N-formyl group, which is slowly hydrolysed under weakly acidic conditions to yield formic acid. Samples equilibrated either with air or oxygen (> 99 % purity) gave essentially the same yield of oxidation products. Experimental evidence indicated that extensive photodegradation of formaldehyde was occurring during photolysis, causing low recoveries of formaldehyde. Consequently, with [²H₃-methyl]demethylmonuron and deuterated water, only steady state concentrations of formaldehyde could be measured in an isotopic study.     

Nuclear and Mitochondrial DNA Polymorphisms in Three Mitotic Parthenogenetic Meloidogyne Spp.

In order to expand our understanding of the genetics of root-knot nematodes, variation in nuclear DNA and mitochondrial DNA in Meloidogyne incognita, M. arenaria and M. javanica was investigated. Despite the obligate mitotic parthenogenetic mode of reproduction, a large number of AFLP polymorphisms were observed among all 16 populations studied. Both UPGMA and principle coordinate analyses revealed three distinct groups that corresponded with the respective species identities of the 16 populations. M. incognita was genetically most distinct. Amplification of 63-bp tandem repeats (TR) in mtDNA from single individuals enabled the calculation of diversity measures at three hierarchical levels: within individuals, among individuals of a single population and among populations. For all three species, the highest diversity was observed within individuals explaining 43–65% of the total diversity. Many individuals contained more than one mtDNA size variant. M. incognita harboured the most heteroplasmic individuals and was the most homogenous at the population level. Only 13% of the total diversity was observed among populations, while this figure was 35% for M. arenaria. Both TR and AFLP data showed that M. arenaria is the most heterogeneous species. The comparison of the genetic distances based on AFLPs and mtDNA size variants revealed a significant correlation for the six M. arenaria populations, whereas no consistent correlation was observed for the populations of the other two species.     

World congress highlights need for action

Landscape ecology traditionally has been limited to the study of terrestrial systems; however, the questions and methods defining the science are equally relevant for marine and coastal systems. The reciprocal relationship between spatial pattern and ecological processes and the overarching effect of scale on this relationship was being explored in some marine and coastal settings as the general discipline of landscape ecology was evolving throughout the latter two decades of the last century. As with all components of the biosphere, an understanding of these relationships is critical for successful management of marine and coastal systems. In these systems, widely dispersed field or ship-based observations and lack of broad scale data have historically precluded quantification of large-scale patterns and processes and hindered management efforts. However, relatively recent advances in geographic information systems, remote sensing and computer technologies have begun to address these issues and are now permitting assessments of pattern and process in oceans. The intent of this special issue is to highlight research that is adapting the tools of landscape ecology to answer ecological questions within marine and coastal systems, to address the unique challenges faced in these landscapes, and to stimulate an exchange of ideas and solutions to common problems. Inspiration for this special issue of Landscape Ecology began with a special session on “Marine and Coastal Applications in Landscape Ecology” that was held at the 19th Annual Symposium of the United States Regional Association of the International Association for Landscape Ecology, March 31–April 2, 2004 in Las Vegas, Nevada.     

Statistical treatment and comparative analysis of scale-dependent aquatic transect data in estuarine landscapes

Estuarine ecosystem dynamics have evolved around and respond to landscape-level influences that are dynamic in space and time. The estuarine water column is effectively the physical and biologial integrator of these landscape inputs. In this paper, we present a floating window Analysis of Covariance (ANCOVA) technique to statistically compare and contrast aquatic transect data that were taken at different times and under different tidal conditions, yet were geographically parallel and spatially articulate. The floating window ANCOVA compared two transects by testing whether the means of the dependent variable were significantly different while also testing whether the slopes of patterns in the dependent variable were significantly different. By varying the size of the floating window where the ANCOVA was run, we were able to examine how scale affected the magnitude and spatial pattern of that variable. The percentages of total models run, at a given window size, that generated significantly different magnitudes (means) and patterns (slopes) in the dependent variable were referred to as the degree of dissimilarity. Plots of window size versus degree of dissimilarity elucidated temporal and spatial variability in water column parameters at a range of scales. The advantages of this new statistical method in relation to traditional spatial statistics are discussed.We demonstrated the efficacy of the floating window ANCOVA method by comparing chlorophyll and salinity transect data taken at the North Inlet, SC estuary during flooding and ebbing tides in Winter, Spring, and Summer 1991. Chlorophyll concentrations represented the biological characteristics of the estuarine water column and salinity represented the physical processes affecting that water column. We found total dissimilarity in the magnitude of salinity data from one season to the next at all scales, but inter-seasonal similarity in spatial patterns over both short (hourly) and long (monthly) time scales. We also found a large seasonal dissimilarity in the magnitude of chlorophyll levels, as expected. Spatial patterns in phytoplankton biomass (as chlorophyll concentrations) appeared to be largely controlled by the physical processes represented with the salinity data. Often, we observed greater dissimilarity in biological and physical parameters from one tide to the next [on a given day] than from one season to the next. In these cases, the greatest flood-ebb differences were associated with landscape-level influences - from rivers and the coastal ocean - that varied greatly with direction of tidal flow. We are currently using spatially articulate aquatic transect data and the floating window ANCOVA technique to validate spatial simulation models at different scales. By using this variable-scale statistical technique to determine coherence between the actual transect data and model output from simulations run at different scales, we will test hypotheses about the scale-dependent relationships between data resolution and model predictability in landscape analysis.     

Teaching medical pathology in the twenty-first century: virtual microscopy applications

Virtual microscopy (VM) has been implemented and evaluated in the histology and general and systemic pathology courses at the University of Iowa Carver College of Medicine. Advantages of VM over traditional microscopy include accessibility and efficiency of learning and the ability to integrate VM with computer-assisted interactive learning. Advantages of using VM as opposed to digital photomicrographs include the ability to pan and zoom, explore the slide, and make independent observations. Although VM is used in a case-based format for teaching histopathology to medical students at the University of Iowa, VM may also be effectively implemented in other medical-student teaching models, including integrated and problem-based learning curricula and the classical pathology laboratory. Additional Iowa venues and courses using VM teaching include pathology of human disease for bioscience graduate students, cytology education, a comparative pathology research resource, and histology and histopathology for veterinary medicine. This article reviews the history and evolution of VM in medical pathology and its implementation at Iowa.     

Comparison of Near Infrared Reflectance Spectroscopy with Combustion and Chemical Methods for Soil Carbon Measurements in Agricultural Soils

As interest in soil organic carbon (SOC) dynamics increases, so do needs for rapid, accurate, and inexpensive methods for quantifying SOC. Objectives were to i) evaluate near infrared reflectance (NIR) spectroscopy potential to determine SOC and soil organic matter (SOM) in soils from across Tennessee, USA; and ii) evaluate potential upper limits of SOC from forest, pasture, no-tillage, and conventional tilled sites. Samples were analyzed via dry-combustion (SOC), Walkley–Black chemical SOM, and NIR. In addition, the sample particle size was classified to give five surface roughness levels to determine effects of particle size on NIR. Partial least squares regression was used to develop a model for predicting SOC as measured by NIR by comparing against SOM and SOC. Both NIR and SOM correlated well (R² > 0.9) with SOC (combustion). NIR is therefore considered a sufficiently accurate method for quantifying SOC in soils of Tennessee, with pasture and forested systems having the greatest accumulations.Abbreviations SOC, soil organic carbon; NIR, Near Infrared Reflectance Spectroscopy; MTREC, Middle Tennessee Research and Education Center; RECM, Research and Education Center at Milan; PREC, Plateau Research and Education Center; PLS, Partial least squares.     

部分高粱转换系与不同高粱细胞质的育性反应

利用部分高粱转换系与具相同核背景不同细胞质的高粱不育系杂交,调查F_1代植株花粉育性和主要农艺性状,结果表明4种细胞质之间育性反应存在着明显的差异,A_1与A_2型细胞质之间差异较小;A_1、A_2与A_3、A_4型之间差异较大。A_1和A_2型细胞质与部分高粱转换系杂交F_1代的自交结实率之间的相关达极显著水准。A_2、A_3型细胞质对F_1代主要农艺性状的影响与A_1型对这些性状的影响无显著差异。A_2型细胞质可以在高粱杂交种生产中加以利用。A_3型细胞质与前两种细胞质的育性反应截然不同。找到了A_3型细胞质的恢复源和能同时恢复A_1、A_2、A_3型细胞质的材料。初步确定了能够鉴定高粱4种不同细胞质的鉴定系。通过对同核异质,异核同质育性反应的研究,表明4种细胞质完全不同,细胞质对育性反应起着决定性的作用,育性反应不因核背景的改变而发生显著变化,不同细胞质育性恢复机制不同。