COMPOSITE VS. DISTRIBUTED CURVE NUMBERS: EFFECTS ON ESTIMATES OF STORM RUNOFF DEPTHS1

ABSTRACT: The U.S. Department of Agriculture Curve Number (CN) method is one of the most common and widely used techniques for estimating surface runoff and has been incorporated into a number of popular hydrologic models. The CN method has traditionally been applied using compositing techniques in which the area weighted average of all curve numbers is calculated for a watershed or a small number of sub-watersheds. CN compositing was originally developed as a time saving procedure, reducing the number of runoff calculations required. However, with the proliferation of high speed computers and geographic information systems, it is now feasible to use distributed CNs when applying the CN method. To determine the effect of using composited versus distributed CNs on runoff estimates, two simulations of idealized watersheds were developed to compare runoff depths using composite and distributed CNs. The results of these simulations were compared to the results of similar analyses performed on an urbanizing watershed located in central Indiana and show that runoff depth estimates using distributed CNs are as much as 100 percent higher than when composited CNs are used. Underestimation of runoff due to CN compositing is a result of the curvilinear relationship between CN and runoff depth and is most severe for wide CN ranges, low CN values, and low precipitation depths. For larger design storms, however, the difference in runoff computed using composite and distributed CNs is minimal.     

Prenatal diagnosis of thrombocytopenia absent radius syndrome using ultrasound and fetoscopy

The prenatal diagnosis of thrombocytopenia absent radius syndrome in both dizygotic twins utilizing ultrasound, radiography and fetoscopy is described.     

Recurrent congenital toxoplasmosis in a woman with lupus erythematosus

We describe the case of a patient with systemic lupus erythematosus, treated by corticosteroids, who presented during two successive pregnancies with serological reactivation of toxoplasmosis associated with fetal lesions. The first infected fetus died in utero with signs of hydrops. The second fetus was treated in utero with a combination of sulfadoxine and pyrimethamine, administered to the mother, and is now well. The increasing number of immunocompromised pregnant patients with immunity to Toxoplasma gondii may lead to a higher risk of reactivation of maternal toxoplasmosis and congenital infection.     

Geochemical Distribution and Bioavailability of Heavy Metals and Oxalate in Street Sediments from Rio de Janeiro, Brazil: A Preliminary Investigation

As urbanisation accelerates within less-economically developed countries, populations in cities such as Rio de Janeiro are subject to numerous health risks relating to “heavy metal”, sewage and vehicle pollution. These risks apply especially to children, through inhalation and dermal contact with pollutant-rich street sediments that reflect contamination from atmospheric deposition and act as effective sinks for heavy metals and oxalates. To assess the nature and extent of these risks street sediments were collected from industrial, commercial, residential and recreational areas with varying traffic densities within Rio de Janeiro. A modified selective extraction procedure was used to study the geochemical partitioning and bioavailability of Fe, Mn, Zn, Cu, Cr, Ni, Pb and C₂O ₄ ⁻ . Oxalate partitioning has not been studied by traditional sequential methods and results from this procedure highlight the potential bioavailability of both oxalates and “heavy metals”, especially Pb and C₂O ₄ ⁻ in industrial and recreational areas.     

Sequential extraction of copper from soils and relationships with copper in maize

We studied copper uptake by maize grown on soils that have been contaminated with CuSO₄. In soil the total copper level ranged from 24 to 135 mg kg^–1. The copper distribution in soil fractions was assessed by sequential extraction, showing that anthropogenic copper is mainly concentrated in oxides fractions. The copper concentration of maize at the maturity stage reached values from 36.3 to 65.9 mg kg^–1 compared to copper levels usually found in non-contaminated crops (5–30 mg kg^–1). Here we demonstrate that copper can be accumulated by maize and that copper concentration in maize can be predicted by equations including copper concentration of soil fractions.     

Impacts of flight distance on sex ratio and resource allocation to offspring in the leafcutter bee, Megachile rotundata

Fisher's theoretical prediction of equal investment in each sex for a panmictic population (The genetical theory of natural selection. Clarendon, Oxford, 1930) can be altered by a number of factors. For example, the sex ratio theory predicts variation in equal investment in each sex when the maternal fitness gains from increased investment differ between sexes. Changing sex allocation because of changing payoffs may result from different ecological situations, such as foraging conditions. We investigated the impact of foraging travel cost on relative investment in sons vs daughters. Field studies were carried out with the central-place-foraging leafcutter bee Megachile rotundata (Fabricius), which has smaller males than females. Therefore, less investment is required to produce a viable son compared with a daughter. We found that with increased flight distance to resources, females produced a greater proportion of sons. Females also invested fewer resources in individual sons and daughters and produced fewer offspring with increased flight distance.     

Male mating effort in a polygynous ungulate

Survival and mating success are key fitness components of mammalian males. Because energy is limited, life history theory predicts trade-offs between current and future reproduction. While many studies have examined fitness trade-off in females, we know little about trade-offs faced by males. In polygynous species, male mating success is largely dependent upon intrasexual competition. Consequently, males have greater uncertainty over the benefits of a given allocation than over its costs, and the correlation between mating effort and success is likely much weaker in males than in females. We analyzed 14 years of data on the mating effort and survival of marked bighorn rams to investigate fitness trade-offs. Dominant rams defended single estrous ewes (“tending”) while subordinates attempted to copulate after separating the tending pair (“coursing”). We estimated the participation in tending and coursing for each ram and the effort in searching for breeding opportunities by each ram each year. We compared these three behavioral indices of male mating effort to demographic parameters, individual characteristics, and both yearly and long-term survival. Mating effort during the rut was unrelated to ram overwinter survival, but longevity was positively correlated with mating effort between 2 and 5 years of age. Persistent variation among rams is likely to explain this pattern, suggesting that in natural populations a few high quality males enjoy both high mating success and high survival.An erratum to this article can be found at     

A national critical loads framework for atmospheric deposition effects assessment: I. Method summary

The United States Environmental Protection Agency (EPA), with the assistance of the US Department of Energy (DOE) and the National Oceanographic and Atmospheric Administration (NOAA) is examining the utility of a critical loads approach for evaluating atmospheric pollutant effects on sensitive ecosystems. A critical load has been defined as, “a quantitative estimate of an exposure to one or more pollutants below which significant harmful effects on specified sensitive elements of the environment do not occur according to present knowledge.” Working in cooperation with the United Nations Economic Community for Europe’s (UN-ECE) Long Range Transboundary Air Pollution (LRTAP) Convention, the EPA has developed a flexible, six-step approach for setting critical loads for a range of ecosystem types. The framework is based on regional population characteristics of the ecosystem(s) of concern. The six steps of the approach are: (1) selection of ecosystem components, indicators, and characterization of the resource; (2) definition of functional subregions; (3) characterization of deposition within each of the subregions; (4) definition of an assessment end point; (5) selection and application of models; and (6) mapping projected ecosystem responses. The approach allows for variable ecosystem characteristics and data availability. Specific recognition of data and model uncertainties is an integral part of the process, and the use of multiple models to obtain ranges of critical loads estimates for each ecosystem component in a region is encouraged. Through this intercomparison process uncertainties in critical loads projections can be estimated. The research described in this article has been funded by the US Environmental Protection Agency. This document has been prepared at the EPA Environmental Research Laboratory in Corvallis, Oregon, through contract #68-C8-0006 with Man Tech Environmental Technology, Inc. It has been subjected to the agency’s peer and administrative review and approved for publication. Mention of trade names or commercial products does not constitute endorse ment or recommendation for use.     

Poly(hydroxyalkanoates) from fluorescent pseudomonads in retrospect and prospect

Poly[(R)-3-hydroxyalkanoates] (PHAs) are biopolymers stored by bacteria, which are currently receiving much attention because of their potential as renewable and biodegradable plastics. Most well-known representatives are poly[(R)-3-hydroxybutyrate] and its copolymers with 3-hydroxyvalerate, which have been commercialized under the trademark Biopol. In addition to these rigid materials, the elastomeric medium-chain length PHAs (mcl-PHAs) produced by fluorescent Pseudomonads are now emerging. The present review aims to survey the important developments concerning research and application prospects of mcl-PHAs.