bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computation of Shock Induced Noise in Imperfectly Expanded Supersonic Jets
Authors: Imamoglu B. , Baysal O. , Balakumar P. 
Published: June 2007

Screech noise exists in imperfectly expanded jets. When the exit pressure of imperfectly expanded jet does not match its backpressure, expansion or compression waves appear out of the nozzle and generate shock cell patterns. Screech is generated by the interaction of shock cells and instability waves. Although many studies have been conducted to model screech noise, it still is not yet a well-understood phenomenon. In the present computational study, the results help better understand screech generation mechanisms and they are compared with the latest available experiments. First, axisymmetric models are constructed for underexpanded jets of 25.4 mm diameter and Mach numbers of 1.19 and 1.43. Then, three dimensional (3D) models are computed for jets with Mach numbers of 1.43 and 1.80. The mathematical model consists of full Navier-Stokes equations in cylindrical coordinates, and large-eddy-simulation turbulence modeling. For spatial discretizations, a fifth-order, weighted essentially non-oscillatory scheme is used, as it is deemed the most suitable method for capturing shocks. Time discretization is a third-order total-variation-diminishing scheme. This methodology does not require artificial viscosity or “tuning up” of parameters. The experimental results predict that the solution is in axisymmetric mode for Mach 1.19 and in helical mode for 1.43. The experimental screech frequencies of 8.4 kHz for Mach 1.19 and 5.4 kHz for Mach 1.43 are verified with the present axisymmetric results. Computed shock cell structure is in agreement with experiments and other published computations in all cases. As in the experiments, the present screech waves emerge from the second and third shock cells. The screech wavelength is roughly estimated as 1.5 D, which is close to other published computational studies. Axisymmetric results for Mach number 1.43 could predict general flow quantities, like shock cell pattern and screech frequency prediction. Therefore, three-dimensional helical effects are investigated by creating a simulation of planes with varying azimuthal angles. This has been useful to detect shock generation locations. In Mach 1.80 case, a barrel shock structure is observed just as in the experimental studies. In conclusion, this study is deemed as a good verification of experimental results.
Chelated Potassium and Arginine Supplementation in Diets of Pacific White Shrimp Reared in Low-Salinity Waters of West Alabama
Authors: Saoud I Patrick , Roy Luke A , Davis D Allen 
Published: June 2007

Abstract
Dietary supplements have been proposed as a potential remediation strategy to counteract mineral deficiencies in low-salinity well waters (LSWW) used for shrimp culture in Alabama. Existing strategies (i.e., application of fertilizers such as K-mag and muriate of potash) are costly to farmers attempting to raise levels of potassium (K+) in their ponds. Previous laboratory studies using dietary supplements of chelated K+ increased growth but not survival of Pacific white shrimp Litopenaeus vannamei reared in low-salinity water. To determine whether this approach is applicable in the field, two growth trials were conducted in flow-through outdoor tanks that used water from farm ponds. The first trial (6 weeks) was conducted simultaneously at two separate low-salinity farms in west Alabama and evaluated two practical diets, one with a chelated K+ supplement and one without. One of these farms supplements K+ to its water and is considered a low-stress environment (LSE), while the other farm does not supplement its water and is considered a high-stress environment (HSE). Results indicated that dietary supplementation of K+ (1.0%) in the absence of an appropriate ionic profile (i.e., the HSE) failed to enhance growth or survival of Pacific white shrimp. Another 9-week growth trial was conducted at the LSE farm. Shrimp were offered either a practical basal diet or the basal diet supplemented with 0.5% chelated K+, 1.0% chelated K+, or 0.4% arginine. Although no statistically significant effects of chelated K+ supplementation were observed, results of this experiment and two other experiments showed an increase in growth associated with chelated K+ supplementation, indicating a marginal benefit. Present results do not justify K+ supplementation of diets for Pacific white shrimp reared in inland LSWW. Better shrimp survival and growth are observed when K+ is added to culture waters to mitigate imbalances in Na:K and Cl:K ratios.
Estimating Seasonal Movements of Chinook Salmon in Lake Huron from Efficiency Analysis of Coded Wire Tag Recoveries in Recreational Fisheries
Authors: Adlerstein Sara A. , Rutherford Edward S. , Clapp David , Clevenger John A. , Johnson James E. 
Published: June 2007

Abstract
The decline of hatchery-reared Chinook salmon Oncorhynchus tshawytscha stocks in Lakes Huron and Michigan during the 1980s prompted mass-tagging programs to investigate reproduction, poststocking survival, and movements. In Lake Huron, millions of smolts implanted with coded wire tags (CWTs) were released in Michigan waters and recovered from charter and noncharter fisheries, surveys, and weirs. Using generalized linear models (GLMs), we investigated Chinook salmon seasonal movements based on the spatial and temporal distributions of recoveries by fishing trips in U.S. recreational fisheries and recovery efficiency. We used models incorporating area, month, year, and recovery source; creel-clerk and “headhunter” (CWT collection specialist) samples; and charter captain reports. We implemented models for recoveries regardless of release area and from one particular area. All model predictors and interactions between month and area were significant. The variation in recovery levels among recovery sources was larger than temporal or spatial variation. Headhunters were 7 times more efficient than captains in recovering CWTs from charter-boat catch and 11 times more efficient than clerks in recovering CWTs from non-charter-boat catch; this was due to the higher catches experienced in charter than in noncharter trips and to different recovery program goals. The spatial and temporal distribution of GLM-standardized recovery levels suggested that Chinook salmon released along the western coast of Lake Huron moved near shore during early spring and north during summer, returning mostly to nearby stocking areas in summer and fall. To complement our GLM analysis, we evaluated the distributions of CWT salmon released and recovered in U.S. and Canadian waters by all sources. Data supported previous conclusions on longitudinal movements and indicated that in spring fish moved from eastern locations to near shore in western Lake Huron then back to overwinter locations in autumn. These movement patterns coincided with seasonal prey species concentrations and favorable temperatures. The implications of our results for salmon fisheries management and the design of future tagging studies are discussed.
Direct and Indirect Estimates of Natural Mortality for Chesapeake Bay Blue Crab
Authors: Hewitt David A. , Lambert Debra M. , Hoenig John M. , Lipcius Romuald N. , Bunnell David B. , Miller Thomas J. 
Published: June 2007

AbstractAnalyses of the population dynamics of blue crabCallinectes sapidushave been complicated by a lack of estimates of the instantaneous natural mortality rate (M). We developed the first direct estimates ofMfor this species by solving Baranov's catch equation forMgiven estimates of annual survival rate and exploitation rate. Annual survival rates were estimated from a tagging study on adult female blue crabs in Chesapeake Bay, and female‐specific exploitation rates for the same stock were estimated by comparing commercial catches with abundances estimated from a dredge survey. We also used eight published methods based on life history parameters to calculate indirect estimates ofMfor blue crab. Direct estimates ofMfor adult females in Chesapeake Bay for the years 2002–2004 ranged from 0.42 to 0.87 per year and averaged 0.71 per year. Indirect estimates ofMvaried considerably depending on life history parameter inputs and the method used. All eight methods yielded values forMbetween 0.99 and 1.08 per year, and six of the eight methods yielded values between 0.82 and 1.35 per year. Our results indicate that natural mortality of blue crab is higher than previously believed, and we considerMvalues between 0.7 and 1.1 per year to be reasonable for the exploitable stock in Chesapeake Bay. Remaining uncertainty aboutMmakes it necessary to evaluate a range of estimates in assessment models.
Recovery of nontarget Lepidoptera on Vancouver Island, Canada: One and four years after a gypsy moth eradication program
Authors: Boulton Timothy J. , Otvos Imre S. , Halwas Karen L. , Rohlfs Doris A. 
Published: June 2007

Abstract
The gypsy moth (Lymantria dispar) is a destructive defoliator that is not established in British Columbia, Canada, because of successful eradication programs involving the microbial insecticide Bacillus thuringiensis var. kurstaki (Btk). In 1999, three aerial applications of Btk were made over two areas, totaling 12,805 ha, on southern Vancouver Island, Canada. The impacts of these Btk applications on nontarget Lepidoptera were studied from 1999 to 2004on Garry oak (Quercus garryana) and common snowberry (Symphoricarpos albus). In 1999, lepidopteran larvae were collected from S. albus foliage at 24 urban parks and from Q. garryana foliage at 28 oak-dominated habitats. The initial impacts (i.e., 1999 data) were published previously, and the present paper is a continuation of the same study. We tested two hypotheses: Reductions of nontarget Lepidoptera would be more severe at 12 to 13 months postspray than at one to two months postspray, and recovery would be significant, though not necessarily complete, at four years postspray. The total number of nontarget Lepidoptera on S. albus and Q. garryana was significantly reduced in the treatment sites in each year of the study: the reduction was greatest in 2000. Relative to the reference sites, each of 11 species that were initially reduced by the Btk applications showed an increase in the treatment sites between 2000 and 2003, by which time only four species remained significantly reduced in the treatment sites. The uncommon species were significantly reduced in 1999 and 2000 but not in 2003, indicating that some recovery had occurred. Limitations and economic implications of the present study are discussed.
Impact of polychlorinated biphenyl and polycyclic aromatic hydrocarbon sequestration in sediment on bioaccumulation in aquatic food webs
Authors: Moermond Caroline T.A. , Roessink Ivo , Jonker Michiel T.O. , Meijer Thijs , Koelmans Albert A. 
Published: June 2007

AbstractIt is not clear whether sequestration or aging of organic chemicals like polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) limits accumulation in higher levels of aquatic food chains. Therefore, the effect of aging on accumulation was studied in 1-m3 model ecosystems that mimicked fish-dominated, macrophyte-dominated, and fish- and macrophyte-dominated shallow lakes. Also treatments without fish and macrophytes were included. General characteristics, biomasses, total (Soxhlet-extractable), and labile (6-h Tenax-extractable) PCB and PAH concentrations in sediment and biota were monitored over time. Accumulation data for PCB 28, PCB 149, and fluoranthene (native to the sediment taken from the field) were compared to those for spiked analogues PCB 29, PCB 155, and fluoranthene-d10. Labile fractions for spiked compounds were higher than for their native analogues and decreased over time, suggesting sequestration in the sediment. In the majority of cases, 6-h Tenaxextractable concentrations correlated better with concentrations in biota than Soxhlet-extractable concentrations. Ecosystem structure affected food web accumulation, but replicate variability was too high to detect clear treatment effects. Differences in accumulation between spiked compounds and their native analogues indicated an effect of aging for invertebrates, macrophytes, and benthivorous fish. Thus, aging may translate directly into reduced uptake at higher trophic levels.
Evaluating regional predictive capacity of a process-based mercury exposure model, regional-mercury cycling model, applied to 91 Vermont and New Hampshire lakes and ponds, USA
Authors: Knightes Christopher D. , Ambrose Robert B. 
Published: June 2007

Abstract
Regulatory agencies must develop fish consumption advisories for many lakes and rivers with limited resources. Process-based mathematical models are potentially valuable tools for developing regional fish advisories. The regional mercury cycling model (R-MCM) specifically was designed to model a series of lakes for a given region with site-specific data and parameterization for each application. In this paper, we explore the feasibility of R-MCM application to develop regional fish advisories from existing data by testing model performance across 91 Vermont ([VT], USA) and New Hampshire ([NH], USA) lakes. We use a progressive method of parameter refinement ranging from simple defaults specified by the model to site-specific parameterization to evaluate potential improvements in model prediction. Model applications and parameter refinement tiers are based on Regional Environmental Monitoring Assessment Program (REMAP) data. Results show that R-MCM generally underpredicts water column methylmercury and total mercury concentrations and overpredicts sediment methylmercury concentrations. Default level input parameterization produced the largest amount of random scatter in model forecasted values. Using site-specific values for the default level characteristics reduced this variability but did not improve overall model performance. By separating the observed and predicted data by lake characteristics, we identify some overall trends in bias and fit, but are unable to identify systematic biases in model performance by lake type. This analysis suggests that process-based models like R-MCM cannot be used for a priori predictive applications at the regional scale at this time. Further, this work reinforces the need for additional research on the transport and transformation of mercury to elucidate parameterization useable in a modeling framework to help refine predictive capabilities of process-based models.
Size-dependence of the potential for metal biomagnification in early life stages of marine fish
Authors: Zhang Li , Wang Wen-Xiong 
Published: June 2007

Abstract
We investigated the bioaccumulation of metals (Cd, Se, and Zn) in different juvenile sizes of black sea bream Acanthopagrus schlegeli by applying a biokinetic model. A series of experiments were conducted to determine the physiological kinetic parameters, including uptake rate constant of waterborne metals, ingestion rate, assimilation efficiency of dietary metals, efflux rate constant, and specific growth rate as a function of fish size. Body concentration of metals as a function of body size was then simulated by the kinetic model and compared with the actual measurements. The uptake rate constants decreased with increasing fish size, with an allometric exponent (b) of 0.615 to 0.662. Ingestion rate was also negatively correlated with the fish size (b = −0.604). Assimilation efficiencies of Cd were independent of body size, whereas those of Se and Zn increased with fish size. In contrast, efflux rate constants and growth rate constants for metals were comparable in different sizes of fish. Predicted concentrations of Cd and Zn were comparable to actual measurements and were negatively correlated with fish size. Ingestion rate was the most important parameter accounting for the size-dependent bioaccumulation of metals, followed by dietary assimilation. We further showed that the trophic transfer potentials of Se and Zn were &gt;1 in smaller fish but then reduced to &lt;1 in larger ones, suggesting that trophic transfer potentials are highly size dependent in marine fish.
Plasma to egg conversion factor for evaluating polychlorinated biphenyl and DDT exposures in great horned owls and bald eagles
Authors: Strause Karl D. , Zwiernik Matthew J. , Im Sook Hyeon , Newsted John L. , Kay Denise P. , Bradley Patrick W. , Blankenship Alan L. , Williams Lisa L. , Giesy John P. 
Published: June 2007

Abstract
The benefits of nondestructive sampling techniques, such as plasma sampling, to directly measure contaminant exposure levels in at-risk or protected raptor populations are many. However, such assays are generally inconsistent with the most certain source of toxicity reference values, which are based on feeding studies and quantified as dietary or “in ovo” (egg-based) concentrations. An accurate conversion factor to translate nondestructive plasma-based contaminant concentrations to comparable egg-based concentrations will prove valuable to risk assessors investigating the potential effects of chemical exposures to raptors. We used databases describing the concentrations of total polychlorinated biphenyls (PCBs) in great horned owls (GHO; Bubo virginianus) and total PCBs and p,p′-dichlorodiphenyldichloroethylene (p,p′-DDE) in bald eagles (Haliaeetus leucocephalus) from the Great Lakes region (Michigan, Wisconsin, USA) to develop a relationship to predict concentrations of PCBs and DDE in eggs. To develop a robust predictive relationship, all of the source data included concentrations of both total PCBs and/or DDE for nestling blood plasma and egg samples collected from within discrete active nesting territories and, in most instances, the same nest. The key characteristics (slope and elevation) of each relationship were tested for differences related to species and geographic region. Predicted variability of relationships were examined and compared to variability associated with natural systems. The results of statistical testing indicate that applying the conversion factors between species (GHO to bald eagle) and among geographic regions yields predicted egg concentrations that are not statistically dissimilar and are within the natural variability observed for residue concentrations among eggs of raptors within species and region.
Effects of brominated flame retardants and brominated dioxins on steroidogenesis in H295R human adrenocortical carcinoma cell line
Authors: Ding Ling , Murphy Margaret B. , He Yuhe , Xu Yan , Yeung Leo W.Y. , Wang Jingxian , Zhou Bingsheng , Lam Paul K.S. , Wu Rudolf S.S. , Giesy John P. 
Published: June 2007

Abstract
Brominated flame retardants (BFRs) and brominated dioxins are emerging persistent organic pollutants that are ubiquitous in the environment and can be accumulated by wildlife and humans. These chemicals can disturb endocrine function. Recent studies have demonstrated that one of the mechanisms of endocrine disruption by chemicals is modulation of steroidogenic gene expression or enzyme activities. In this study, an in vitro assay based on the H295R human adrenocortical carcinoma cell line, which possesses most key genes or enzymes involved in steroidogenesis, was used to examine the effects of five bromophenols, two polybrominated biphenyls (PBBs 77 and 169), 2,3,7,8-tetrabromodibenzo-p-dioxin, and 2,3,7,8-tetrabromodibenzofuran on the expression of 10 key steroidogenic genes. The H295R cells were exposed to various BFR concentrations for 48 h, and the expression of specific genes—cytochrome P450 (CYP11A, CYP11B2, CYP17, CYP19, and CYP21), 3β-hydroxysteroid dehydrogenase (3βHSD2), 17β-hydroxysteroid dehydrogenase (17βHSD1 and 17βHSD4), steroidogenic acute regulatory protein (StAR), and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR)—was quantitatively measured using real-time polymerase chain reaction. Cell viability was not affected at the doses tested. Most of the genes were either up- or down-regulated, to some extent, by BFR exposure. Among the genes tested, 3βHSD2 was the most markedly up-regulated, with a range of magnitude from 1.6- to 20-fold. The results demonstrate that bromophenol, bromobiphenyls, and bromodibenzo-p-dioxin/furan are able to modulate steroidogenic gene expression, which may lead to endocrine disruption.
Inorganic mercury detection by valve closure response in the freshwater clamCorbicula fluminea: Integration of time and water metal concentration changes
Authors: Tran Damien , Fournier Elodie , Durrieu Gilles , Massabuau Jean-Charles 
Published: June 2007

AbstractThe objective of the present study was to monitor water-quality assessment by a biological method. Optimum dissolved inorganic mercury sensitivity in the freshwater bivalve Corbicula fluminea was estimated using a combined approach to determine their potentials and limits in detecting contaminants. Detection by bivalves is based on shell closure, a protective strategy when exposed to a water contaminant. To take the rate of spontaneous closures into account, stress associated with fixation by one valve in common valvometers was integrated, and the spontaneous rhythm was associated with daily activity. The response in conditions where the probability of spontaneous closing is the lowest was thus taken into account. To develop dose–response curves, impedance valvometry, in which lightweight impedance electrodes are applied to study free-ranging animals in low-stress conditions, also was used combined with a new analytical approach. The logistic regression dose–response curves take into account variations in both response time and metal concentration in water to significantly improve the methods aiming at determining the optimal sensitivity threshold response. This approach demonstrates that in C. fluminea, inorganic mercury concentrations under the range of 2.0 to 5.1 μg/L (95% confidence interval) cannot be detected within 5 h of addition.
Biogeochemical factors affecting mercury methylation in sediments of the Venice Lagoon, Italy
Authors: Han Seunghee , Obraztsova Anna , Pretto Patrizia , Choe Key-Young , Gieskes Joris , Deheyn Dimitri D. , Tebo Bradley M. 
Published: June 2007

Abstract
Mercury methylation and sulfate reduction rates, total Hg, and monomethyl Hg in the sediments of the Venice Lagoon (Italy) were measured in June 2005 in order to identify the factors affecting the methylation of inorganic Hg. While the rates of Hg methylation and sulfate reduction were generally higher in the surface layers (0–2.5 cm), the correlation between Hg methylation and sulfate reduction rates was not significant when considering all depths and sites. This discrepancy is discussed considering two factors: the activity of sulfate-reducing bacteria and Hg solubility. The former factor is important in determining the Hg methylation rate in comparable geochemical conditions as evidenced by similar vertical profiles of Hg methylation and sulfate reduction rates in each sediment core. The latter factor was assessed by comparing the Hg methylation rate with the particle—water partition coefficient of Hg. The Hg methylation rates normalized to sulfate reduction rates showed a negative linear correlation with the logarithm of the particle-water partition coefficient of Hg, suggesting that the availability of dissolved Hg is a critical factor affecting Hg methylation. Solid FeS seems to play an important role in controlling the solubility of Hg in Venice Lagoon sediments, where sulfate and iron reductions are the dominant electron-accepting processes. Overall, the production of monomethyl Hg in the Venice Lagoon is controlled by a fine balance between microbial and geochemical processes with key factors being the microbial sulfate reduction rate and the availability of dissolved Hg.