Concentrations Of Other Species Research Articles

Clam Size Explains Some Variability in Paralytic Shellfish Toxin Concentrations in Butter Clams (Saxidomus gigantea) in Southeast Alaska

Harmful algal blooms (HABs) are a reoccurring threat to subsistence and recreational shellfish harvest in Southeast Alaska. Recent Tribally led monitoring programs have enhanced understanding of the environmental drivers and toxicokinetics of shellfish toxins in the region; however, there is considerable variability in shellfish toxins in some species, which cannot be easily explained by seasonal bloom dynamics. Persistent concentrations of paralytic shellfish toxins (PSTs) in homogenized butter clam samples (n > 6, Saxidomus gigantea) have been observed in several communities, and relatively large spikes in concentrations are sometimes seen without Alexandrium observations or increased toxin concentrations in other species. In order to investigate potential sources of variability in PST concentrations from this subsistence species, we assessed individual concentrations of PSTs across a size gradient of butter clams during a period of relatively stable PST concentrations. We found that increasing concentrations of PSTs were significantly associated with larger clams using a log-linear model. We then simulated six clams randomly sampled from three size distributions, and we determined large clams had an outsized probability of contributing a significant proportion of the total toxicity in a six-clam homogenized sample. While our results were obtained during a period of low HAB activity and cannot be extrapolated to periods of intoxication or rapid detoxification, they have significant ramifications for both monitoring programs as well as subsistence and recreational harvesters.

Robustness for biochemical networks: Step-by-step approach

We propose two step-by-step approaches to the analysis of robustness in biochemical networks. Our aim is to measure the ability of the network to exhibit step-by-step limited variations on the concentration of a species of interest at varying of the initial concentration of other species. The first approach we propose is reaction-by-reaction, i.e. we compare the states reached by nominal and perturbed networks after they have performed the same number of reactions. We provide a statistical technique allowing for estimating robustness, we implement it in a tool called spebnr (a Simple Python Environment for statistical estimation of Biochemical Network Robustness) and showcase it on three case studies: the EnvZ/OmpR osmoregulatory signaling system of Escherichia Coli, the mechanism of bacterial chemotaxis of Escherichia Coli, and enzyme activity at saturation. Then, we consider a time-by-time approach, in which networks are compared on the basis of the states they reached at the same time point, regardless of how many reactions occurred. This approach is implemented in Stark, and we apply it to the study the robustness of the EnvZ/OmpR osmoregulatory signaling system and the Lotka-Volterra equations.

Cross-diffusion-induced transitions between Turing patterns in reaction-diffusion systems

Cross-diffusion is one of the most important factors affecting the formation and transition of Turing patterns in reaction diffusion systems. In this paper, cross-diffusion is introduced into a reaction diffusion Brusselator model to investigate the effects of the directivity and density-dependence of cross-diffusion on Turing pattern transition. Turing space is obtained by the standard linear stability analysis, and the amplitude equations are derived based on weakly nonlinear method, by which Turing pattern selection can be determined theoretically. It is found that the degree of deviation from the primary Turing bifurcation point plays an important role in determining the process of pattern selection in the Turing region. As the deviation from onset is increased, the system exhibits a series of pattern transitions from homogenous state to honeycomb hexagonal pattern, to stripe pattern, and then to hexagonal spot pattern. In the case of one-way cross-diffusion, the direction of cross-diffusion determines the order of Turing pattern transition. The cross-diffusion from the inhibitor to the activator enhances the Turing mode and drives the system far away from the primary bifurcation point, resulting in the forward order of Turing pattern transition. On the contrary, the cross-diffusion from the activator to the inhibitor suppresses the Turing mode and forces the pattern transition in a reverse order. In the case of two-way cross-diffusion, the cross-diffusion effect from inhibitors to activators is stronger than that from activators to inhibitors with the same diffusion coefficient. Essentially, the cross-diffusion coefficient is dependent on not only the local concentration of species itself, but also the concentrations of other species due to their interaction. It is found that concentration dependent cross diffusion also affects the transformation direction of Turing pattern. When the diffusion coefficient <inline-formula><tex-math id="M6">\begin{document}$ {D_{uv}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230333_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230333_M6.png"/></alternatives></inline-formula> is linearly dependent on the concentration of retarders, the positive transformation of the Turing pattern is induced with the increase of the concentration linear adjustment parameter <inline-formula><tex-math id="M7">\begin{document}$ \beta $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230333_M7.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230333_M7.png"/></alternatives></inline-formula>. On the contrary, when the diffusion coefficient <inline-formula><tex-math id="M8">\begin{document}$ {D_{vu}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230333_M8.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230333_M8.png"/></alternatives></inline-formula> is linearly dependent on the concentration of active particles, the reverse transformation of the Turing pattern is induced. The numerical simulation results are consistent with the theoretical analysis.

Cardiovascular changes in horses with atrial fibrillation and high thyroid hormone concentration: a case–control study

IntroductionHyperthyroidism is a predisposing factor for atrial fibrillation (AF) in humans. The relationship between high thyroid hormone (TH) and AF in horses has not been evaluated. ObjectivesThe aim of this study is to identify whether (1) high TH concentrations were present in horses with AF, (2) other cardiovascular effects were observed in horses with high TH and AF, and (3) TH status affected recurrence rate. AnimalsTwenty-three horses presented with naturally occurring AF. MethodsProspective case–control clinical study. Thyroid hormone concentration was measured in horses presenting with AF. Heart rate, electrocardiogram, blood pressure, and an echocardiogram were recorded as part of their clinical workup. Recurrence rate was determined by owner/veterinarian follow-up. ResultsHigh TH concentration was found in 60% of horses with AF. Horses in the high TH group had a higher heart rate (P=0.001), systolic blood pressure (P=0.019), left ventricular free wall thickness (P=0.026), relative wall thickness (P=0.041) and were more likely to have periods of AF with a rapid ventricular response rate (P=0.022). All horses were successfully converted to normal sinus rhythm. The likelihood of recurrence was not different between groups. ConclusionElevated TH concentration can be found in horses with AF. Other cardiovascular effects of high TH concentrations in other species were also present in horses with AF and elevated TH concentrations. This study recommends measuring TH concentrations in horses presenting for AF with a history of thyroid or iodine supplementation. This study also cautions against TH or iodine supplementation in healthy performance horses.

Online Measurements of Hydrogen Impurities in PEMFC Single Cells and Short Stacks

Impurities can easily contaminate pure hydrogen at various points in the supply chain. The maximum allowed impurity concentrations in hydrogen, sold for automotive PEMFC use, are regulated by the ISO 14687 standard. Imposing too strict limits on hydrogen quality increases the cost of hydrogen unnecessarily but too lax limits risk the performance and durability of PEFMCs. It is therefore imperative that the specified limits are based on rigorous and realistic studies of impurity behaviour in fuel cells. As part of the European Union funded projects HYDRAITE and MetroHyVe2, NPL is investigating the impact of fuel impurities on the performance and durability of fuel cells. The overall aim is to develop new testing standards and provide more reliable information to ISO committees for the continuous revision of fuel quality standards.Impurity studies are being carried out primarily on commercial short stacks tested with a hydrogen recirculation loop and a dead-end anode. This operation mode is typical in real systems as it gives a very high fuel utilisation, however it also causes fuel impurities to concentrate well above their inlet level. Standard fuel cell testing is coupled with online measurements of the concentration of a range of contaminants inside the anode recirculation loop. For example, a Gas Chromatograph with a methanizer and flame ionising detector (GC-methanizer-FID) is used to provide information on CO2, CO, and CH4; while Selected Ion Flow Tube - Mass Spectrometry (SIFT-MS) is used to analyse isotopically labelled impurities and probe the concentrations of other species as a function of time.Our results will first show the power and limitations of using online gas analysis with isotopically labelled impurities to monitor processes related to CO poisoning in single cells. We will then demonstrate that certain hydrocarbon impurities have little impact on stack performance despite being stringently regulated. Finally, we will present information on rates of O2 and CO2 crossover, drawing conclusions relevant for setting the next iteration of hydrogen fuel standards. This work provides vital underpinning metrological support for the development of more robust business cases for large scale deployment of hydrogen in automotive applications.

Molecular characterization of biomass burning tracer compounds in fine particles in Nanjing, China

Abstract In this work, a sensitive method based on the High Performance Liquid Chromatography-Electrospray Ionization-Mass spectrometry/Mass spectrometry (HPLC-ESI-MS/MS) technique was established and validated, and successfully applied to quantify biomass burning tracer species (in total 20 compounds) in fine aerosol particles (PM2.5) collected during the full year of 2016 in Nanjing, China. The annual levoglucosan concentration was determined to be 328.3 ng m−3, at a similar level as it in other Chinese cities; the concentration peaked in fall, indicating influences of crop/straw burning during harvest periods. Concentrations of other species were a few orders of magnitude lower than that of levoglucosan, with salicylic acid (1.53 ng m−3), cis-pinonic acid (0.60 ng m−3) and vanillic acid (0.51 ng m−3) as the three most abundant ones. Total concentrations of tracers indicative of softwood, hardwood and grass burning were about equal. Seasonal concentrations of these tracers were generally similar, and all peaked in winter, different from that of levolglucosan. Further positive matrix factorization (PMF) identified four types of biomass (cellulose, harwood lignin, softwood lignin and grass). Celluose was dominated in fall, while softwood and hardwood were both dominated in winter, and seasonal contributions (except summer) were relatively even to grass. On an annual basis, softwood, hardwood and grass contributions were almost on par to the selected tracers, in agreement with the results based only on concentrations, but seasonally, grass was the major one in spring, summer and fall, but much less important in winter.

A new nano biosensor for maitotoxin with high sensitivity and selectivity based fluorescence resonance energy transfer between carbon quantum dots and gold nanoparticles

Maitotoxin (MTX) is a potent marine toxin with critical LD50, which usually causes poisoning because of eating the contaminated marine crustaceans. This poison is a severe threat to neuronal systems and also disables the heart by increasing the calcium ions flow in the cardiovascular. Therefore, the quantitative determination of MTX by using a fast and cost-effective way is essential. Application of carbon dots in the structure of various sensors for the measurement of biological compounds has been developed due to its easy, rapid and inexpensive synthesis. In this study, carbon quantum dots (CQDs) and gold nanoparticles (AuNPs) were synthesized for the determination of MTX with high sensitivity and selectivity. The structure of CQDs and AuNPs were characterized using SEM (Scanning electron microscopy), TEM (Transmission electron microscopy), EDS (Energy-dispersive X-ray spectroscopy) and FT-IR (Fourier-transform infrared spectroscopy) techniques. The Basis of the sensing method is fluorescence resonance energy transfer (FRET) which occurs between energy donor (CQDs) and energy acceptor (AuNPs). Under optimal conditions (excitation wavelength 430 nm and emission wavelength 523 nm), the linear range and detection limit were obtained 1−600 pmol L−1 and 0.3 pmol L-1, respectively. The strong point of this nanosensor is its very fast quenching process. The interference effect of other poisons and some ions on the MTX determination were investigated using CQDs at the constant concentration of MTX50 pmol L-1 and various concentrations of other species. The results show excellent selectivity for the measurement of MTX in the presence of other similar species.

Extreme Air Pollution Events Spiking Ionic Levels at Urban and Rural Sites of Indo-Gangetic Plain

ABSTRACT The present study is a modest attempt to quantify the water-soluble inorganic ions (WSIIs) in the early morning (fog-forming) ambient air on the central Indo-Gangetic Plain (IGP) during winter via dissolution using a low-cost refluxing mist chamber. The chemical composition of the bulk samples showed significant differences in the WSIIs between the two monitored sites, one urban and the other rural, with NH4+ (47% and 37%, respectively) and Ca2+ (18% and 8%, respectively) being the major cations and NO3– (10% and 16%, respectively) and SO42– (9% and 14%, respectively) being the major anions. The WSII concentration spiked during November at both locations (∑WSII = 159.6 and 141.9 µg m–3) due to two extreme air pollution events, viz., i) the burning of crop residue and ii) the Diwali festival. These changes, which were corroborated by observations of the meteorological conditions, played an essential role in the wintertime atmospheric chemistry. On foggy days, significant scavenging of ions associated with crustal dust (Ca2+, Na+, Mg2+ and Cl–) occurred, although the ambient concentrations of other species (K+, NH4+, NO2–, NO3– and SO42–) remained relatively unaffected. Furthermore, the relationship between the cations and anions demonstrated that NH3 and HONO, as the primary gaseous species, were involved in heterogeneous aqueous-phase reactions and the formation of secondary aerosols. Source apportionment based on principal component analysis and the mass ratios also indicated that local anthropogenic sources, in addition to natural ones such as soil/road dust and biogenic emissions, influenced the WSII composition. Vehicular exhaust, solid waste and biofuel burning were identified as the major contributors of WSIIs at the urban site, whereas biomass burning, agricultural activity and coal combustion in brick kilns were the predominant sources at the rural site.

Dynamics of Outgassing and Plume Transport Revealed by Proximal Unmanned Aerial System (UAS) Measurements at Volcán Villarrica, Chile

AbstractVolcanic gas emissions are intimately linked to the dynamics of magma ascent and outgassing and, on geological time scales, constitute an important source of volatiles to the Earth's atmosphere. Measurements of gas composition and flux are therefore critical to both volcano monitoring and to determining the contribution of volcanoes to global geochemical cycles. However, significant gaps remain in our global inventories of volcanic emissions, (particularly for CO2, which requires proximal sampling of a concentrated plume) for those volcanoes where the near‐vent region is hazardous or inaccessible. Unmanned Aerial Systems (UAS) provide a robust and effective solution to proximal sampling of dense volcanic plumes in extreme volcanic environments. Here we present gas compositional data acquired using a gas sensor payload aboard a UAS flown at Volcán Villarrica, Chile. We compare UAS‐derived gas time series to simultaneous crater rim multi‐GAS data and UV camera imagery to investigate early plume evolution. SO2 concentrations measured in the young proximal plume exhibit periodic variations that are well correlated with the concentrations of other species. By combining molar gas ratios (CO2/SO2 = 1.48–1.68, H2O/SO2 = 67–75, and H2O/CO2 = 45–51) with the SO2 flux (142 ± 17 t/day) from UV camera images, we derive CO2 and H2O fluxes of ~150 t/day and ~2,850 t/day, respectively. We observe good agreement between time‐averaged molar gas ratios obtained from simultaneous UAS‐ and ground‐based multi‐GAS acquisitions. However, the UAS measurements made in the young, less diluted plume reveal additional short‐term periodic structure that reflects active degassing through discrete, audible gas exhalations.

Ceramide-transfer protein-mediated ceramide transfer is a structurally tunable flow-inducing mechanism with structural feed-forward loops.

This paper considers two models of ceramide-transfer protein (CERT)-mediated ceramide transfer at the trans-Golgi network proposed in the literature, short distance shuttle and neck swinging, and seeks structural (parameter-free) features of the two models, which rely exclusively on the peculiar interaction network and not on specific parameter values. In particular, it is shown that both models can be seen as flow-inducing systems, where the flows between pairs of species are tuned by the concentrations of other species, and suitable external inputs can structurally regulate ceramide transfer. In the short distance shuttle model, the amount of transferred ceramide is structurally tuned by active protein kinase D (PKD), both directly and indirectly, in a coherent feed-forward loop motif. In the neck-swinging model, the amount of transferred ceramide is structurally tuned by active PI4KIIIβ, while active PKD has an ambivalent effect, due to the presence of an incoherent feed-forward loop motif that directly inhibits ceramide transfer and indirectly promotes it; the structural role of active PKD is to favour CERT mobility in the cytosol. It is also shown that the influences among key variables often have structurally determined steady-state signs, which can help falsify the models against experimental traces.

Determinants of mercury contamination in viperine snakes, Natrix maura, in Western Europe

The effects of Hg contamination are presumably widespread across the components of aquatic ecosystems, but investigations have been mainly focused on freshwater fish, because this biota represents a major source of Hg for human populations. Yet, the possible bioaccumulation of Hg on other freshwater meso- and apex-predators (e.g., amphibians, reptiles) has been largely overlooked, especially in Western Europe. In this study, the determinants of Hg concentrations were assessed for the viperine snake (Natrix maura) across 6 populations (>130 individuals sampled in 2016 and 2017) in France and Spain. Specifically, body size, sex, and diet were compared with Hg concentrations measured in ventral scales. Overall, N. maura accumulated Hg in their scales. Sex did not seem to influence Hg concentrations in this species. Significant differences in Hg concentrations were observed between study sites, and these differences were likely to be mediated by site-specific diet. Frog-eating individuals were characterized not only by lower mean values of Hg (0.194±0.018μg·g−1 versus 0.386±0.032μg·g−1 for piscivorous individuals), but also by weaker slopes of the body size-Hg relationship as compared to fish-eating snakes, suggesting strong differences in accumulation rates due to food resources. Importantly, the highest slope of the body size-Hg relationship and the highest values of Hg were found in individuals foraging on trout raised by a fish farm, suggesting that fish farming may contribute to Hg contamination in inland freshwater systems. Finally, our results are compared with data on Hg concentrations in other species of aquatic snakes, in order to provide a comparative point for future studies.

Pharmacokinetics of meloxicam after intramuscular and oral administration of a single dose to American flamingos (Phoenicopertus ruber).

OBJECTIVE To determine pharmacokinetics after IM and oral administration of a single dose of meloxicam to American flamingos (Phoenicopertus ruber). ANIMALS 14 adult flamingos. PROCEDURES Flamingos were allocated to 2 groups. Each group received a dose of meloxicam (1 mg/kg) by the IM or oral route. After a 4-week washout period, groups received meloxicam via the other route of administration. Plasma meloxicam concentrations were measured with high-performance liquid chromatography. Data for each bird were analyzed. Estimated values of selected pharmacokinetic parameters were compared by use of a linear mixed-effects ANOVA. Pooled concentration-time profiles for each route of administration were analyzed to examine the influence of body weight on pharmacokinetics. RESULTS Mean ± SD maximum plasma concentration was 1.00 ± 0.88 μg/mL after oral administration. This was approximately 15% of the mean maximum plasma concentration of 5.50 ± 2.86 μg/mL after IM administration. Mean time to maximum plasma concentration was 1.33 ± 1.32 hours after oral administration and 0.28 ± 0.17 hours after IM administration. Mean half-life of the terminal phase after oral administration (3.83 ± 2.64 hours) was approximately twice that after IM administration (1.83 ± 1.22 hours). CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that the extent and rate of meloxicam absorption were less after oral administration than after IM administration. Intramuscular administration resulted in a short period during which mean plasma concentrations met or exceeded reported efficacious analgesic concentrations in other species, whereas oral administration did not. These results suggested that higher doses may be required for oral administration.

Bio- and toxic elements in edible wild mushrooms from two regions of potentially different environmental conditions in eastern Poland.

In the present study, the composition of bio-elements (K, Na, Mg, Ca, Fe, Cu, Zn) and toxic elements (Ag, Cd) in seven edible mushrooms from the rural and woodland region of Morąg (north-eastern Poland) and the rural and industrial region of the Tarnobrzeska Upland (south-eastern Poland) were investigated using a validated method. The species examined were Boletus edulis, Cantharellus cibarius, Leccinum aurantiacum, Leccinum versipelle, Lycoperdon perlatum, Suillus luteus, and Xerocomus subtomentosus. Final determination was carried out by flame atomic absorption spectroscopy (FAAS) after microwave-assisted decomposition of sample matrices with solutions of concentrated nitric acid in the pressurized polytetrafluoroethylene vessels. The contents of the alkali elements and alkali earth elements were determined in the species surveyed. The alkali elements, earth alkali elements, and transition metals (Ag, Cu, Zn, Fe, and Mn) were at typical concentrations as was determined for the same or similar species elsewhere in Poland and Europe. The results may suggest a lack of local and regional emissions of those metallic elements from industrialization of some sites in the Tarnobrzeska Plain. Cadmium was at elevated concentrations in L. versipelle from the Tarnobrzeska Plain but the reason—pollution or geogenic source—was unknown, while it was at typical concentrations in other species.

Synchronous Multi-sits Determination of H2O2 in Vertical Water Based on Phosphor TiO2/SiO2 Nanocomposite.

A promising strategy for trace analysis of hydrogen peroxide (H2O2) in natural water was established based on solid substrate room temperature phosphorimetry. The use of TiO2/SiO2 composite material as a phosphor for H2O2 detection was investigated. TiO2/SiO2 nanoparticle material was manufactured into a test kit for synchronous multilevel sampling test in the water sample reservoir. The proposed TiO2/SiO2 test kit displayed a wide linear response to H2O2 concentrations ranging from 1.0 × 10(-6) to 1.0 × 10(-1) M with a detection limit of 4.6 × 10(-7) M. When the concentration of other species was 100 times of 1.0 × 10(-4) M H2O2, the proposed test kit exhibited good selectivity toward the coexistence of 20 foreign ions. Satisfactory agreement between the proposed kit and spectrophotometric method was obtained, which demonstrated the possibility of its further development into a promising commercial phosphorescence sensor.

Assessment of oil contamination in the bay of Porto Grande (Cape Verde) using the mullet Chelon bispinosus

Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent organic pollutants, some of which are mutagenic and carcinogenic so PAH concentrations in fish used for human consumption are crucial to assess impact to human health. Total PAH concentrations in muscle and liver of mullets Chelon bispinosus from the Bay of Porto Grande (Cape Verde) (four sites in the bay and a control) ranged from 112.7 to 779.5 and 291.5 to 7548.7 ng/g d. w., respectively. Two and three ring PAHs were the most frequent (72.8 to 90.8% in the muscle and 75.9 to 98.3% in the liver), but levels of carcinogenic PAHs (mainly Dibenzo (a,h) antracene) in certain sites (CN and PG) are of concern. Results reflect a chronic PAH pollution in the bay and sources are a mixture of anthropogenic (petrogenic and pyrolytic) and natural sources, making their identification extremely complex. Although, BaP levels were below the threshold established by Cape Verde and the European Union, BaPEs levels in muscle ranged from 0.28 to 3.66 ng/g w. w. and BAPEs and TPAHs exposure for the average adult was 0.02 to 0.26 and 1.6 to 11.2 µg/day, respectively. Further knowledge of PAH concentrations in other species are necessary for a proper environmental risk assessment policy.

Spectroscopic Analysis of Microwave-Generated Plasmas

Aiming at understanding and controlling the major mechanisms and processes in microwave-generated plasmas, the ground-state densities of the most relevant atomic species and their spatial distributions were determined in these plasmas. They can be measured by optical emission and absorption spectroscopy. Similar to the determination of the silicon ground-state density from the analysis of the self-absorbed spectral lines of the silicon ground-state multiplet 3p 23 P-3p4s 3 P 0 in the ultraviolet range at about 251 nm, the neutral concentrations of other species like carbon and titanium were evaluated from further spectroscopic analyses. Furthermore, the spatial distributions were explored in detail. New developments of microwave-generated plasma sources and their optical emission spectroscopy to investigate the kind of species in the plasmas, as well as the gas and excitation temperatures, are also presented.

Mercury concentrations in seabird tissues from Machias Seal Island, New Brunswick, Canada

Mercury is a pervasive environmental contaminant, the anthropogenic portion of which is increasing globally, and in northeastern North America in particular. Seabirds frequently are used as indicators of the marine environment, including mercury contamination. We analysed paired samples for total mercury (Hg) concentrations in feathers and blood from adult and chick, albumen, and lipid-free yolk of seven seabirds breeding on Machias Seal Island, New Brunswick, Canada — Arctic Tern ( Sterna paradisaea), Atlantic Puffin ( Fratercula arctica), Common Eider ( Somateria mollissima), Common Murre ( Uria aalge), Common Tern ( Sterna hirundo), Leach's Storm-petrel ( Oceanodroma leucorhoa), and Razorbill ( Alca torda). We also used stable-isotope ratios of carbon ( δ 13C), and nitrogen ( δ 15N) to evaluate the relationship between carbon source and trophic position and mercury. We found high Hg concentrations across tissue types in Leach's Storm-petrels, and Razorbills, with lower concentrations in other species, the lowest being in Common Eiders. Storm-petrels prey on mesopelagic fish that accumulate mercury, and Razorbills feed on larger, older fish that bioaccumulate heavy metals. Biomagnification of Hg, or the increase in Hg concentration with trophic position as measured by δ 15N, was significant and greater in albumen than other tissues, whereas in other tissues, δ 15N explained little of the overall variation in Hg concentration. Hg concentrations in egg components are higher on Machias Seal Island than other sites globally and in the Gulf of Maine region, but only for some species. Further detailed investigations are required to determine the cause of this trend.

Is dimethylsulfoniopropionate (DMSP) produced by the symbionts or the host in an anemone–zooxanthella symbiosis?

Many groups of tropical cnidarians including scleractinian corals, octocorals, corallimorphs, and anemones contain the tertiary sulfonium compound dimethylsulfoniopropionate (DMSP). It is not known if the compound is synthesized by the animals, their microalgal symbionts, or derived through their diet. We determined the source of the DMSP in several species of tropical and temperate anemones using three approaches: (1) conducting comparative measurements of DMSP in aposymbiotic and zooxanthellate anemones of three species that harbor zooxanthellae, and similar measurements in one species that can harbor both zooxanthellae and zoochlorellae, (2) manipulating the presence or absence of zooxanthellae by inoculating juvenile aposymbiotic anemones (Aiptasia pallida) with their symbiont, Symbiodinium bermudense, and (3) manipulating the numbers of S. bermudense by growing aposymbiotic and zooxanthellate A. pallida in the light and the dark. DMSP was present in zooxanthellate anemones in concentrations of 3.4–15 μmol g−1 fresh mass (FM). In aposymbiotic Aiptasia spp. and Anthopleura elegantissima that lacked large numbers of zooxanthellae, concentrations ranged from being undetectable to 0.43 μmol g−1 FM. When aposymbiotic A. pallida were inoculated with zooxanthellae, concentrations of DMSP were an average of 4.24 μmol g−1 FM after 5 weeks; DMSP was undetectable in uninoculated control animals. Aposymbiotic anemones maintained in the light or the dark for 6 weeks contained no DMSP or zooxanthellae. Zooxanthellate anemones in the light contained five times as many zooxanthellae and approximately 7.5 times as much DMSP as zooxanthellate anemones maintained in the dark. Taken together, these data show that the zooxanthellae are the sole source of DMSP in A. pallida. The trends in DMSP concentrations in other species of zooxanthellate anemones suggest that this phenomenon is not limited to A. pallida but may be more generally true for other anemones or even other cnidarians hosting species of Symbiodinium.

Biomass Solid Oxide Fuel Cell-Microgas Turbine Hybrid System: Effect of Fuel Composition

Performance analysis of the solid oxide fuel cell-microgas turbine (SOFC-MGT) hybrid system has been made. We assume a fuel composition that is methane based with varying concentrations of other species that are expected to be present in biomass-derived gas streams in preparation for the study of biomass fueled SOFC-MGT hybrid system. This is based on the fact that the chemical composition of biomass fuel produced from different fuel production processes is diversified, i.e., in one case one chemical species rich in concentration and in another case another chemical species rich. In the analysis, the multistage model for internal reforming SOFC module developed previously with some modification is used. With this model, studies cover not only the performance of the hybrid system but also the spatial distributions of temperature and concentration of some chemical species inside the module, namely, in the cell stack and in the internal reformer.

A Journey from n-Heptane to Liquid Transportation Fuels. 1. The Role of the Allylic Radical and Its Related Species in Aromatic Precursor Chemistry

The Utah normal heptane mechanism compiled from submechanisms in the literature was extended into a detailed normal decane combustion mechanism, which is a subset of the Utah surrogate mechanisms. Few species have greater impact on the concentrations of other species than the allyl radical CH2CH═CH2. Reactions involving the allyl radical and its isomers determine the concentration levels of all olefins, most higher unsaturated species, and benzene. To correctly predict the concentration of benzene, the reaction rates involving allyl-radical-related species need to be accurate and the concentration profiles of these species need to be satisfactory. Kinetic rates found in the literature are compared in the current work for various reference reactions that involve the allylic radicals. The improvements in numerical predictions of unsaturated species are achieved after a rigorous study in finding reliable reaction rates and kinetic correlations between various species. Some of these rates are adopted as the generic rates that have been used in the Utah surrogate mechanisms in previous studies. The modified mechanism is able to predict the concentration profiles of unsaturated species in n-decane and n-heptane flames with good numerical accuracy. The concentrations of these species are closely related to those of various allylic radicals, and reliable kinetics of allylic reactions are critical in predicting the concentrations of benzene and higher aromatics.