Egg coloration is correlated with female condition in eastern bluebirds (Sialia sialis)

Egg coloration has been hypothesized to reflect female condition. Because of the proposed physiological costs associated with deposition of biliverdin pigments and because of their conspicuousness, eggs with blue-green coloration may reliably convey information about female or brood quality. We tested the hypothesis that expression of blue-green coloration of eastern bluebird (Sialia sialis) eggs positively correlates to female condition. First, we documented the incidence of egg color polymorphism within the population. We observed that 98% of females laid blue-green eggs while less than 2% laid white eggs and less than 1% laid pink eggs. In a subset of clutches, we used full spectrum reflectance spectrometry (300–700 nm) to compare eggshell coloration to measures of female condition. We found that the color of eggs within clutches was more similar than the color of eggs from different clutches, and that the blue-green eggs have spectral peaks that are consistent with the characteristic absorbance spectra of biliverdin pigmentation. Females in better body condition and older females laid more colorful eggs. Moreover, individual females laid more colorful eggs later in the laying sequence. Overall, these data indicate that egg coloration covaries with female condition, suggesting that egg coloration could function as a reliable signal of female quality or that egg coloration may allow females to recognize eggs laid by conspecific brood parasites.     

Comparison of short-term variations (15-minute averages) in outdoor and indoor PM2.5 concentrations

Measurements of 15-min average PM2.5 concentrations were made with a real-time light-scattering instrument at both outdoor (central monitoring sites in three communities) and indoor (residential) locations over two seasons in the Minneapolis-St. Paul metropolitan area. These data are used to examine within-day variability of PM2.5 concentrations indoors and outdoors, as well as matched indoor-to-outdoor (I/O) ratios. Concurrent gravimetric measurements of 24-hr average PM2.5 concentrations were also obtained as a way to compare real-time measures with this more traditional metric. Results indicate that (1) within-day variability for both indoor and outdoor 15-min average PM2.5 concentrations was substantial and comparable in magnitude to day-to-day variability for 24-hr average concentrations; (2) some residences exhibited substantial variability in indoor aerosol characteristics from one day to the next; (3) peak values for indoor short-term (15-min) average PM2.5 concentrations routinely exceeded 24-hr average outdoor values by factors of 3-4; and (4) relatively strong correlations existed between indoor and outdoor PM2.5 concentrations for both 24-hr and 15-min averages.     

The effect of thermodynamic data on computer model predictions of uranium speciation in natural water systems

Computer models have found widespread application in order to help elucidate and predict changes in environmental systems. One such application is the prediction of trace metal speciation in aqueous systems. This is achieved by solving a set of non-linear equations involving equilibrium constants for all the components in the system, within mass and charge balance constraints. In this study a comparison of the predicted uranium speciation from two computer programs, WHAM and PHREEQCI, is used to illustrate the effect variations in thermodynamic data can have on the models produced. Using the original thermodynamic data provided with the models, WHAM predicted the UO2(2+) ion as the major species (84%) while PHREEQCI predicted UO2(HPO4)2(2-) as the major species (86%). Substituting uranium data from the Nuclear Energy Agency Thermochemical Database project (NEA-TDB) into both programs produced similar results from each program, with UO2F+ predicted to dominate (68%) in a groundwater sample. Natural water samples often contain humic substances. The possible interaction of such substances with uranium was also modelled. The WHAM program includes a discreet site electrostatic humic substance model, however in order to use the PHREEQCI program to model humic substance interactions, a 'model fulvic acid' dataset was added to the program. These models predicted 85 to 98% uranium-humic substance species at neutral pH. This indicates that humic substances do need to be taken into account when modelling uranium speciation in natural water samples.     

Uranium speciation in moorland river water samples: a comparison of experimental results and computer model predictions

An on-line method has been developed for separating inorganic and organic bound uranium species present in river water samples. The method utilised a small chelating resin (Hyphan) column incorporated into the sample introduction manifold of an ICP-MS instrument. The method was evaluated for samples from rivers on Dartmoor (Devon, UK), an area of granite overlain with peat bogs. The results indicate that organic-uranium species form a major proportion (80%) of the total dissolved uranium present. Further work with synthetic water samples indicated that the level of dissolved organic carbon played a greater role in determining the level of organic-uranium species than did sample pH. Computer models for the water samples were constructed using the WHAM program (incorporating uranium data from the Nuclear Energy Agency Thermochemical Database project) in order to predict the levels of organic-uranium species that would form. By varying the proportion of humic and fulvic acids used in the humic component, predictions within 10% of the experimental results were obtained. The program did exhibit a low bias at higher pH values (7.5) and low organic carbon concentrations (0.5 microg ml(-1)), but under the natural conditions prevalent in the Dartmoor water samples, the model predictions were successful.     

Numerical methods for improving sensitivity analysis and parameter estimation of virus transport simulated using sorptive-reactive processes

Using one- and two-dimensional homogeneous simulations, this paper addresses challenges associated with sensitivity analysis and parameter estimation for virus transport simulated using sorptive-reactive processes. Head, flow, and conservative- and virus-transport observations are considered. The paper examines the use of (1) observed-value weighting, (2) breakthrough-curve temporal moment observations, and (3) the significance of changes in the transport time-step size. The results suggest that (1) sensitivities using observed-value weighting are more susceptible to numerical solution variability, (2) temporal moments of the breakthrough curve are a more robust measure of sensitivity than individual conservative-transport observations, and (3) the transport-simulation time step size is more important than the inactivation rate in solution and about as important as at least two other parameters, reflecting the ease with which results can be influenced by numerical issues. The approach presented allows more accurate evaluation of the information provided by observations for estimation of parameters and generally improves the potential for reasonable parameter-estimation results.     

The spontaneous resolution of cystic hygromas and early fetal growth delay in fetuses with trisomy 18

The spontaneous resolution of cystic hygromas in fetuses with trisomy 18 may be due to a delay in lymphatic-vascular anastomosis. The severity of growth delay with trisomy 18 appears to be variable in time of onset and extent.     

The role of glucose in developing enhanced biological phosphorus removal

Sequential batch reactors were operated to study the mechanism of developing enhanced biological phosphorus removal (EBPR) while feeding glucose as the dominant substrate. Initial results indicated that feeding glucose as the dominant substrate caused poor and un-stable EBPR performance, similar to the findings reported by other researchers. The operating procedures for the glucose system were modified to longer anaerobic reaction time, higher glucose concentration in the influent, and shorter aerobic reaction time with a limited DO level. The application of these modified procedures successfully established stable EBPR performance by using glucose as the major substrate. Batch experiments showed that glucose was immediately transported into the bacteria and stored as glycogen and that poly-β-hydroxyvalerate predominated poly-β-hydroxyalkanoate (PHA) during the anaerobic phase. It was also observed that much lower levels of PO₄-P anaerobic release and PHA accumulation occurred in the glucose induced EBPR system than in the acetate induced EBPR system. It is hypothesized that glycogen might replace the essential energy role of polyphosphate under the anaerobic condition, which results in the deterioration of PO₄-P removal unless these modified operating procedures are applied.