784 research outputs found

    Next generation of consumer aerosol valve design using inert gases

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    The current global consumer aerosol products such as deodorants, hairsprays, air-fresheners, polish, insecticide, disinfectant are primarily utilised unfriendly environmental propellant of liquefied petroleum gas (LPG) for over three decades. The advantages of the new innovative technology described in this paper are: (i) no butane or other liquefied hydrocarbon gas; (ii) compressed air, nitrogen or other safe gas propellant; (iii) customer acceptable spray quality and consistency during can lifetime; (iv) conventional cans and filling technology. Volatile organic compounds and greenhouse gases must be avoided but there are no flashing propellants replacements that would provide the good atomisation and spray reach. On the basis of the energy source for atomising, the only feasible source is inert gas (i.e. compressed air), which improves atomisation by gas bubbles and turbulence inside the atomiser insert of the actuator. This research concentrates on using ‘bubbly flow’ in the valve stem, with injection of compressed gas into the passing flow, thus also generating turbulence. Using a vapour phase tap in conventional aerosol valves allows the propellant gas into the liquid flow upstream of the valve. However, forcing bubbly flow through a valve is not ideal. The novel valves designed here, using compressed gas, thus achieved the following objectives when the correct combination of gas and liquid inlets to the valve, and the type and size of atomiser ‘insert’ were derived: 1. Produced a consistent flow rate and drop size of spray throughout the life of the can, compatible with the current conventional aerosols that use LPG: a new ‘constancy’ parameter is defined and used to this end. 2. Obtained a discharge flow rate suited to the product to be sprayed; typically between 0.4 g/s and 2.5 g/s. 3. Attained the spray droplets size suited to the product to be sprayed; typically between 40 mm and 120 mm

    Modeling gaseous non-reactive flow in a lean direct injection gas turbine combustor through an advanced mesh control strategy

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    [EN] Fuel efficiency improvement and harmful emissions reduction are the main motivations for the development of gas turbine combustors. Numerical computational fluid dynamics (CFD) simulations of these devices are usually computationally expensive since they imply a multi-scale problem. In this work, gaseous non-reactive unsteady Reynolds-Averaged Navier-Stokes and large eddy simulations of a gaseous-fueled radial-swirled lean direct injection combustor have been carried out through CONVERGE (TM) CFD code by solving the complete inlet flow path through the swirl vanes and the combustor. The geometry considered is the gaseous configuration of the CORIA lean direct injection combustor, for which detailed measurements are available. The emphasis of the work is placed on the demonstration of the CONVERGE (TM) applicability to the multi-scale gas turbine engines field and the determination of an optimal mesh strategy through several grid control tools (i.e., local refinement, adaptive mesh refinement) allowing the exploitation of its automatic mesh generation against traditional fixed mesh approaches. For this purpose, the normalized mean square error has been adopted to quantify the accuracy of turbulent numerical statistics regarding the agreement with the experimental database. Furthermore, the focus of the work is to study the behavior when coupling several large eddy simulation sub-grid scale models (i.e., Smagorinsky, Dynamic Smagorinsky, and Dynamic Structure) with the adaptive mesh refinement algorithm through the evaluation of its specific performances and predictive capabilities in resolving the spatial-temporal scales and the intrinsically unsteady flow structures generated within the combustor. This investigation on the main non-reacting swirling flow characteristics inside the combustor provides a suitable background for further studies on combustion instability mechanisms.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was partly sponsored by the program "Ayuda a Primeros Proyectos de Investigacion (PAID-06-18), Vicerrectorado de Investigacion, Innovacion y Transferencia de la Universitat Politecnica de Valencia (UPV), Spain.'' The support given to Mr. Mario Belmar by Universitat Politecnica de Valencia through the "FPI-Subprograma 2'' grant within the "Programa de Apoyo para la Investigacion y Desarrollo (PAID-01-18)'' is gratefully acknowledged.Payri, R.; Novella Rosa, R.; Carreres, M.; Belmar-Gil, M. (2020). Modeling gaseous non-reactive flow in a lean direct injection gas turbine combustor through an advanced mesh control strategy. Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering. 234(11):1788-1810. https://doi.org/10.1177/0954410020919619S1788181023411Patel, N., Kırtaş, M., Sankaran, V., & Menon, S. (2007). Simulation of spray combustion in a lean-direct injection combustor. Proceedings of the Combustion Institute, 31(2), 2327-2334. doi:10.1016/j.proci.2006.07.232Luo, K., Pitsch, H., Pai, M. G., & Desjardins, O. (2011). Direct numerical simulations and analysis of three-dimensional n-heptane spray flames in a model swirl combustor. Proceedings of the Combustion Institute, 33(2), 2143-2152. doi:10.1016/j.proci.2010.06.077Masri, A. R., Pope, S. B., & Dally, B. B. (2000). Probability density function computations of a strongly swirling nonpremixed flame stabilized on a new burner. Proceedings of the Combustion Institute, 28(1), 123-131. doi:10.1016/s0082-0784(00)80203-9Johnson, M. R., Littlejohn, D., Nazeer, W. A., Smith, K. O., & Cheng, R. K. (2005). A comparison of the flowfields and emissions of high-swirl injectors and low-swirl injectors for lean premixed gas turbines. Proceedings of the Combustion Institute, 30(2), 2867-2874. doi:10.1016/j.proci.2004.07.040Sankaran, V., & Menon †, S. (2002). LES of spray combustion in swirling flows. Journal of Turbulence, 3, N11. doi:10.1088/1468-5248/3/1/011Jones, W. P., Marquis, A. J., & Vogiatzaki, K. (2014). Large-eddy simulation of spray combustion in a gas turbine combustor. Combustion and Flame, 161(1), 222-239. doi:10.1016/j.combustflame.2013.07.016Ding, G., He, X., Xue, C., Zhao, Z., & Jin, Y. (2015). Preliminary design and experimental verification of a triple swirler combustor. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 229(12), 2258-2271. doi:10.1177/0954410015573555Menon, S., & Patel, N. (2006). Subgrid Modeling for Simulation of Spray Combustion in Large-Scale Combustors. 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Ballistic imaging of the near field in a diesel spray. Experiments in Fluids, 40(6), 836-846. doi:10.1007/s00348-006-0122-0Desantes, J. M., Salvador, F. J., López, J. J., & De la Morena, J. (2010). Study of mass and momentum transfer in diesel sprays based on X-ray mass distribution measurements and on a theoretical derivation. Experiments in Fluids, 50(2), 233-246. doi:10.1007/s00348-010-0919-8Reddemann, M. A., Mathieu, F., & Kneer, R. (2013). Transmitted light microscopy for visualizing the turbulent primary breakup of a microscale liquid jet. Experiments in Fluids, 54(11). doi:10.1007/s00348-013-1607-2Chen, R.-H., & Driscoll, J. F. (1989). The role of the recirculation vortex in improving fuel-air mixing within swirling flames. Symposium (International) on Combustion, 22(1), 531-540. doi:10.1016/s0082-0784(89)80060-8Presser, C., Gupta, A. K., & Semerjian, H. G. (1993). Aerodynamic characteristics of swirling spray flames: Pressure-jet atomizer. 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International Journal of Multiphase Flow, 36(5), 349-363. doi:10.1016/j.ijmultiphaseflow.2010.01.008Asgari, B., & Amani, E. (2017). A multi-objective CFD optimization of liquid fuel spray injection in dry-low-emission gas-turbine combustors. Applied Energy, 203, 696-710. doi:10.1016/j.apenergy.2017.06.080Moureau, V., Domingo, P., & Vervisch, L. (2011). From Large-Eddy Simulation to Direct Numerical Simulation of a lean premixed swirl flame: Filtered laminar flame-PDF modeling. Combustion and Flame, 158(7), 1340-1357. doi:10.1016/j.combustflame.2010.12.004Caraeni, D., Bergström, C., & Fuchs, L. (2000). Flow, Turbulence and Combustion, 65(2), 223-244. doi:10.1023/a:1011428926494Icardi, M., Gavi, E., Marchisio, D. L., Olsen, M. G., Fox, R. O., & Lakehal, D. (2011). Validation of LES predictions for turbulent flow in a Confined Impinging Jets Reactor. Applied Mathematical Modelling, 35(4), 1591-1602. doi:10.1016/j.apm.2010.09.035Sankaran, V., & Menon, S. (2002). Vorticity-scalar alignments and small-scale structures in swirling spray combustion. Proceedings of the Combustion Institute, 29(1), 577-584. doi:10.1016/s1540-7489(02)80074-8Lebas, R., Menard, T., Beau, P. A., Berlemont, A., & Demoulin, F. X. (2009). Numerical simulation of primary break-up and atomization: DNS and modelling study. International Journal of Multiphase Flow, 35(3), 247-260. doi:10.1016/j.ijmultiphaseflow.2008.11.005Zhou, Y., Huang, Y., & Mu, Z. (2017). Large eddy simulation of the influence of synthetic inlet turbulence on a practical aeroengine combustor with counter-rotating swirler. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 233(3), 978-990. doi:10.1177/0954410017745900Torregrosa, A. J., Broatch, A., García-Tíscar, J., & Gomez-Soriano, J. (2018). Modal decomposition of the unsteady flow field in compression-ignited combustion chambers. 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    Preconditioning of mesenchymal stromal cells with low-intensity ultrasound: influence on chondrogenesis and directed SOX9 signaling pathways

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    Background: Continuous low-intensity ultrasound (cLIUS) facilitates the chondrogenic differentiation of human mesenchymal stromal cells (MSCs) in the absence of exogenously added transforming growth factor-beta (TGFβ) by upregulating the expression of transcription factor SOX9, a master regulator of chondrogenesis. The present study evaluated the molecular events associated with the signaling pathways impacting SOX9 gene and protein expression under cLIUS. Methods: Human bone marrow-derived MSCs were exposed to cLIUS stimulation at 14 kPa (5 MHz, 2.5 Vpp) for 5 min. The gene and protein expression of SOX9 was evaluated. The specificity of SOX9 upregulation under cLIUS was determined by treating the MSCs with small molecule inhibitors of select signaling molecules, followed by cLIUS treatment. Signaling events regulating SOX9 expression under cLIUS were analyzed by gene expression, immunofluorescence staining, and western blotting. Results: cLIUS upregulated the gene expression of SOX9 and enhanced the nuclear localization of SOX9 protein when compared to non-cLIUS-stimulated control. cLIUS was noted to enhance the phosphorylation of the signaling molecule ERK1/2. Inhibition of MEK/ERK1/2 by PD98059 resulted in the effective abrogation of cLIUS-induced SOX9 expression, indicating that cLIUS-induced SOX9 upregulation was dependent on the phosphorylation of ERK1/2. Inhibition of integrin and TRPV4, the upstream cell-surface effectors of ERK1/2, did not inhibit the phosphorylation of ERK1/2 and therefore did not abrogate cLIUS-induced SOX9 expression, thereby suggesting the involvement of other mechanoreceptors. Consequently, the effect of cLIUS on the actin cytoskeleton, a mechanosensitive receptor regulating SOX9, was evaluated. Diffused and disrupted actin fibers observed in MSCs under cLIUS closely resembled actin disruption by treatment with cytoskeletal drug Y27632, which is known to increase the gene expression of SOX9. The upregulation of SOX9 under cLIUS was, therefore, related to cLIUS-induced actin reorganization. SOX9 upregulation induced by actin reorganization was also found to be dependent on the phosphorylation of ERK1/2. Conclusions: Collectively, preconditioning of MSCs by cLIUS resulted in the nuclear localization of SOX9, phosphorylation of ERK1/2 and disruption of actin filaments, and the expression of SOX9 was dependent on the phosphorylation of ERK1/2 under cLIUS

    Experimental and modeling investigation of the effect of air preheat on the formation of NOx in an RQL combustor

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    The Rich-burn/Quick-mix/Lean-burn (RQL) combustor concept has been proposed to minimize the formation of oxides of nitrogen (NOx) in gas turbine systems. The success of this low-NOx combustor strategy is dependent upon the links between the formation of NOx, inlet air preheat temperature, and the mixing of the jet air and fuel-rich streams. Chemical equilibrium and kinetics modeling calculations and experiments were performed to further understand NOx emissions in an RQL combustor. The results indicate that as the temperature at the inlet to the mixing zone increases (due to preheating and/or operating conditions) the fuel-rich zone equivalence ratio must be increased to achieve minimum NOx formation in the primary zone of the combustor. The chemical kinetics model illustrates that there is sufficient residence time to produce NOx at concentrations that agree well with the NOx measurements. Air preheat was found to have very little effect on mixing, but preheating the air did increase NOx emissions significantly. By understanding the mechanisms governing NO x formation and the temperature dependence of key reactions in the RQL combustor, a strategy can be devised to further reduce NOx emissions using the RQL concept. © 2012 The Author(s)

    A seasonal cycle in the export of bottom water from the Weddell Sea

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    Dense water formed over the Antarctic continental shelf rapidly descends into the deep ocean where it spreads throughout the global ocean as Antarctic Bottom Water1, 2. The coldest and most voluminous component of this water mass is Weddell Sea bottom water1, 3, 4, 5, 6, 7. Here we present observations over eight years of the temperature and salinity stratification in the lowermost ocean southeast of the South Orkney Islands, marking the export of Weddell Sea bottom water. We observe a pronounced seasonal cycle in bottom temperatures, with a cold pulse in May/June and a warm one in October/November, but the timing of these phases varies each year. We detect the coldest bottom water in 1999 and 2002, whereas there was no cold phase in 2000. On the basis of current velocities and water mass characteristics, we infer that the pulses originate from the southwest Weddell Sea. We propose that the seasonal fluctuations of Weddell Sea bottom-water properties are governed by the seasonal cycle of the winds over the western margin of the Weddell Sea. Interannual fluctuations are linked to the variability of the wind-driven Weddell Sea gyre and hence to large-scale climate phenomena such as the Southern Annular Mode and El Niño/Southern Oscillation

    Relevance of large litter bag burial for the study of leaf breakdown in the hyporheic zone

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    Particulate organic matter is the major source of energy for most low-order streams, but a large part of this litter is buried within bed sediment during floods and thus become poorly available for benthic food webs. The fate of this buried litter is little studied. In most cases, measures of breakdown rates consist of burying a known mass of litter within the stream sediment and following its breakdown over time. We tested this method using large litter bags (15 x 15 cm) and two field experiments. First, we used litter large bags filled with Alnus glutinosa leaves (buried at 20 cm depth with a shovel) in six stations within different land-use contexts and with different sediment grain sizes. Breakdown rates were surprisingly high (0.0011–0.0188 day-1) and neither correlate with most of the physico-chemical characteristics measured in the interstitial habitats nor with the land-use around the stream. In contrast, the rates were negatively correlated with a decrease in oxygen concentrations between surface and buried bags and positively correlated with both the percentage of coarse particles (20–40 mm) in the sediment and benthic macro-invertebrate richness. These results suggest that the vertical exchanges with surface water in the hyporheic zone play a crucial role in litter breakdown. Second, an experimental modification of local sediment (removing fine particles with a shovel to increase vertical exchanges) highlighted the influence of grain size on water and oxygen exchanges, but had no effect on hyporheic breakdown rates. Burying large litter bags within sediments may thus not be a relevant method, especially in clogged conditions, due to changes induced through the burial process in the vertical connectivity between surface and interstitial habitats that modify organic matter processing

    Electrophysiological Properties of Motor Neurons in a Mouse Model of Severe Spinal Muscular Atrophy: In Vitro versus In Vivo Development

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    We examined the electrophysiological activity of motor neurons from the mouse model of severe spinal muscular atrophy (SMA) using two different methods: whole cell patch clamp of neurons cultured from day 13 embryos; and multi-electrode recording of ventral horns in spinal cord slices from pups on post-natal days 5 and 6. We used the MED64 multi-electrode array to record electrophysiological activity from motor neurons in slices from the lumbar spinal cord of SMA pups and their unaffected littermates. Recording simultaneously from up to 32 sites across the ventral horn, we observed a significant decrease in the number of active neurons in 5–6 day-old SMA pups compared to littermates. Ventral horn activity in control pups is significantly activated by serotonin and depressed by GABA, while these agents had much less effect on SMA slices. In contrast to the large differences observed in spinal cord, neurons cultured from SMA embryos for up to 21 days showed no significant differences in electrophysiological activity compared to littermates. No differences were observed in membrane potential, frequency of spiking and synaptic activity in cells from SMA embryos compared to controls. In addition, we observed no difference in cell survival between cells from SMA embryos and their unaffected littermates. Our results represent the first report on the electrophysiology of SMN-deficient motor neurons, and suggest that motor neuron development in vitro follows a different path than in vivo development, a path in which loss of SMN expression has little effect on motor neuron function and survival

    Inhibition of Apoptosis Blocks Human Motor Neuron Cell Death in a Stem Cell Model of Spinal Muscular Atrophy

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    Spinal muscular atrophy (SMA) is a genetic disorder caused by a deletion of the survival motor neuron 1 gene leading to motor neuron loss, muscle atrophy, paralysis, and death. We show here that induced pluripotent stem cell (iPSC) lines generated from two Type I SMA subjects–one produced with lentiviral constructs and the second using a virus-free plasmid–based approach–recapitulate the disease phenotype and generate significantly fewer motor neurons at later developmental time periods in culture compared to two separate control subject iPSC lines. During motor neuron development, both SMA lines showed an increase in Fas ligand-mediated apoptosis and increased caspase-8 and-3 activation. Importantly, this could be mitigated by addition of either a Fas blocking antibody or a caspase-3 inhibitor. Together, these data further validate this human stem cell model of SMA, suggesting that specific inhibitors of apoptotic pathways may be beneficial for patients

    Concurrent Exposure of Bottlenose Dolphins (Tursiops truncatus) to Multiple Algal Toxins in Sarasota Bay, Florida, USA

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    Sentinel species such as bottlenose dolphins (Tursiops truncatus) can be impacted by large-scale mortality events due to exposure to marine algal toxins. In the Sarasota Bay region (Gulf of Mexico, Florida, USA), the bottlenose dolphin population is frequently exposed to harmful algal blooms (HABs) of Karenia brevis and the neurotoxic brevetoxins (PbTx; BTX) produced by this dinoflagellate. Live dolphins sampled during capture-release health assessments performed in this region tested positive for two HAB toxins; brevetoxin and domoic acid (DA). Over a ten-year study period (2000–2009) we have determined that bottlenose dolphins are exposed to brevetoxin and/or DA on a nearly annual basis (i.e., DA: 2004, 2005, 2006, 2008, 2009; brevetoxin: 2000, 2004, 2005, 2008, 2009) with 36% of all animals testing positive for brevetoxin (n = 118) and 53% positive for DA (n = 83) with several individuals (14%) testing positive for both neurotoxins in at least one tissue/fluid. To date there have been no previously published reports of DA in southwestern Florida marine mammals, however the May 2008 health assessment coincided with a Pseudo-nitzschia pseudodelicatissima bloom that was the likely source of DA observed in seawater and live dolphin samples. Concurrently, both DA and brevetoxin were observed in common prey fish. Although no Pseudo-nitzschia bloom was identified the following year, DA was identified in seawater, fish, sediment, snails, and dolphins. DA concentrations in feces were positively correlated with hematologic parameters including an increase in total white blood cell (p = 0.001) and eosinophil (p<0.001) counts. Our findings demonstrate that dolphins within Sarasota Bay are commonly exposed to two algal toxins, and provide the impetus to further explore the potential long-term impacts on bottlenose dolphin health
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