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Jesus Manuel Torres Palenzuela - One of the best experts on this subject based on the ideXlab platform.
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remote sensing chlorophyll a of optically complex waters rias baixas nw spain application of a regionally specific chlorophyll a algorithm for meris Full Resolution data during an upwelling cycle
Remote Sensing of Environment, 2011Co-Authors: Evangelos Spyrakos, Luis Gonzalez Vilas, Jesus Manuel Torres Palenzuela, Eric D BartonAbstract:Abstract This study takes advantage of a regionally specific algorithm and the characteristics of Medium Resolution Imaging Spectrometer (MERIS) in order to deliver more accurate, detailed chlorophyll a (chla) maps of optically complex coastal waters during an upwelling cycle. MERIS Full Resolution chla concentrations and in situ data were obtained on the Galician (NW Spain) shelf and in three adjacent rias (embayments), sites of extensive mussel culture that experience frequent harmful algal events. Regionally focused algorithms (Regional neural network for rias Baixas or NNRB) for the retrieval of chla in the Galician rias optically complex waters were tested in comparison to sea-truth data. The one that showed the best performance was applied to a series of six MERIS (FR) images during a summer upwelling cycle to test its performance. The best performance parameters were given for the NN trained with high-quality data using the most abundant cluster found in the rias after the application of fuzzy c-mean clustering techniques (FCM). July 2008 was characterized by three periods of different meteorological and oceanographic states. The main changes in chla concentration and distribution were clearly captured in the images. After a period of strong upwelling favorable winds a high biomass algal event was recorded in the study area. However, MERIS missed the high chlorophyll upwelled water that was detected below surface in the ria de Vigo by the chla profiles, proving the necessity of in situ observations. Relatively high biomass “patches” were mapped in detail inside the rias. There was a significant variation in the timing and the extent of the maximum chla areas. The maps confirmed that the complex spatial structure of the phytoplankton distribution in the rias Baixas is affected by the surface currents and winds on the adjacent continental shelf. This study showed that a regionally specific algorithm for an ocean color sensor with the characteristics of MERIS in combination with in situ data can be of great help in chla monitoring, detection and study of high biomass algal events in an area affected by coastal upwelling such as the rias Baixas.
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neural network estimation of chlorophyll a from meris Full Resolution data for the coastal waters of galician rias nw spain
Remote Sensing of Environment, 2011Co-Authors: Luis Gonzalez Vilas, Evangelos Spyrakos, Jesus Manuel Torres PalenzuelaAbstract:Abstract In typical Case 2 waters, accurate remote sensing retrieval of chlorophyll a (chl a ) is still a challenging task. In this study, focusing on the Galician rias (ΝW Spain), algorithms based on neural network (NN) techniques were developed for the retrieval of chl a concentration in optically complex waters, using Medium Resolution Imaging Spectrometer (MERIS) data. There is considerable interest in the accurate estimation of chl a for the Galician rias , because of the economic and social importance of the extensive culture of mussels, and the high frequency of harmful algal events. Fifteen MERIS Full Resolution (FR) cloud-free images paired with in situ chl a data (for 2002–2004 and 2006–2008) were used for the development and validation of the NN. The scope of NN was established from the clusters obtained using fuzzy c-mean (FCM) clustering techniques applied to the satellite-derived data. Three different NNs were developed: one including the whole data set, and two others using only points belonging to one of the clusters. The input data for these latter two NNs was chosen depending on the quality level, defined on the basis of quality flags given to each data set. The fitting results were fairly good and proved the capability of the tool to predict chl a concentrations in the study area. The best prediction was given for the NN trained with high-quality data using the most abundant cluster data set. The performance parameters in the validation set of this NN were R 2 = 0.86, mean percentage error (MPE) = − 0.14, root mean square error (RMSE) = 0.75 mg m − 3 , and relative RMSE = 66%. The NN developed in this study detected accurately the peaks of chl a , in both training and validation sets. The performance of the Case-2-Regional (C2R) algorithm, routinely used for MERIS data, was also tested and compared with our best performing NN and the sea-truthing data. Results showed that this NN outperformed the C2R, giving much higher R 2 and lower RMSE values. This study showed that the combination of in situ data and NN technology improved the retrieval of chl a in Case 2 waters, and could be used to obtain more accurate chl a maps. A local-based algorithm for the chl a retrieval from an ocean colour sensor with the characteristics of MERIS would be a great support in the quantitative monitoring and study of harmful algal events in the coastal waters of the Rias Baixas . The limitations and possible improvements of the developed chl a algorithms are also discussed.
Ned Horning - One of the best experts on this subject based on the ideXlab platform.
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spatiotemporal variations of total suspended matter tsm in the pearl river estuary using meris Full Resolution fr level 2 tsm product
Marine and Freshwater Research, 2019Co-Authors: Yunpeng Wang, Xinyi Hu, Chao Xu, Ned HorningAbstract:In this study, we first use self-organising map (SOM) and medium-Resolution imaging spectrometer (MERIS) Full-Resolution (FR) level-2 total suspended matter (TSM) product to identify spatial-distribution patterns of TSM concentration in the Pearl River estuary. Second, the spatial and temporal variation of TSM concentration in the Pearl River estuary was investigated using 9-year (2003–2011) MERIS FR level-2 TSM products. The spatial-distribution patterns of TSM concentration identified by SOM in the Pearl River estuary showed that there are high values in west and north and low values in east and south. On the basis of the analysis of the sample points randomly extracted from the Pearl River estuary, the results showed that the spatial variation of TSM in eight gates varied greatly, and the Lingdingyang Bay from Humen to offshore waters (i.e. Xitan, Zhongtan and Dongtan) presents a decreasing trend. Moreover, extreme climate events (e.g. EI Nino and La Nina) may have a great effect on spatial and temporal variation of TSM concentration in the Pearl River estuary. These results could provide a new insight for a better understanding of the dynamics of TSM concentration in the Pearl River estuary and the effect of soil- and water-conservation measures in the upstream of Pearl River.
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spatiotemporal variations of total suspended matter tsm in the pearl river estuary using meris Full Resolution fr level 2 tsm product
Marine and Freshwater Research, 2019Co-Authors: Yunpeng Wang, Xinyi Hu, Chao Xu, Ned HorningAbstract:In this study, we first use self-organising map (SOM) and medium-Resolution imaging spectrometer (MERIS) Full-Resolution (FR) level-2 total suspended matter (TSM) product to identify spatial-distribution patterns of TSM concentration in the Pearl River estuary. Second, the spatial and temporal variation of TSM concentration in the Pearl River estuary was investigated using 9-year (2003–2011) MERIS FR level-2 TSM products. The spatial-distribution patterns of TSM concentration identified by SOM in the Pearl River estuary showed that there are high values in west and north and low values in east and south. On the basis of the analysis of the sample points randomly extracted from the Pearl River estuary, the results showed that the spatial variation of TSM in eight gates varied greatly, and the Lingdingyang Bay from Humen to offshore waters (i.e. Xitan, Zhongtan and Dongtan) presents a decreasing trend. Moreover, extreme climate events (e.g. EI Nino and La Nina) may have a great effect on spatial and temporal variation of TSM concentration in the Pearl River estuary. These results could provide a new insight for a better understanding of the dynamics of TSM concentration in the Pearl River estuary and the effect of soil- and water-conservation measures in the upstream of Pearl River.
Jolyon P Mitchell - One of the best experts on this subject based on the ideXlab platform.
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relative precision of inhaler aerodynamic particle size distribution apsd metrics by Full Resolution and abbreviated andersen cascade impactors acis part 2 investigation of bias in extra fine mass fraction with aim hrt impactor
Aaps Pharmscitech, 2010Co-Authors: Jolyon P Mitchell, Mark Nagel, Valentina Avvakoumova, Rubina Ali, Cathy Doyle, David J Christopher, Jorge Quiroz, Helen Strickland, Terrence P Tougas, Svetlana LyapustinaAbstract:The purpose of this study was to resolve an anomalously high measure of extra-fine particle fraction (EPF) determined by the abbreviated cascade impactor possibly relevant for human respiratory tract (AIM-HRT) in the experiment described in Part 1 of this two-part series, in which the relative precision of abbreviated impactors was evaluated in comparison with a Full Resolution Andersen eight-stage cascade impactor (ACI). Evidence that the surface coating used to mitigate particle bounce was laterally displaced by the flow emerging from the jets of the lower stage was apparent upon microscopic examination of the associated collection plate of the AIM-HRT impactor whose cut point size defines EPF. A filter soaked in surfactant was floated on top of this collection plate, and further measurements were made using the same pressurized metered-dose inhaler-based formulation and following the same procedure as in Part 1. Measures of EPF, fine particle, and coarse particle fractions were comparable with those obtained with the ACI, indicating that the cause of the bias had been identified and removed. When working with abbreviated impactors, this precaution is advised whenever there is evidence that surface coating displacement has occurred, a task that can be readily accomplished by microscopic inspection of all collection plates after allowing the impactor to sample ambient air for a few minutes.
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Relative Precision of Inhaler Aerodynamic Particle Size Distribution (APSD) Metrics by Full Resolution and Abbreviated Andersen Cascade Impactors (ACIs): Part 1
AAPS PharmSciTech, 2010Co-Authors: Jolyon P Mitchell, Valentina Avvakoumova, Jorge Quiroz, Helen Strickland, Terrence P Tougas, Mark W. Nagel, Cathy C. Doyle, Rubina S. Ali, J. David Christopher, Svetlana LyapustinaAbstract:The purpose of this study was to compare relative precision of two different abbreviated impactor measurement (AIM) systems and a traditional multi-stage cascade impactor (CI). The experimental design was chosen to provide separate estimates of variability for each impactor type. Full-Resolution CIs are useful for characterizing the aerosol aerodynamic particle size distribution of orally inhaled products during development but are too cumbersome, time-consuming, and resource-intensive for other applications, such as routine quality control (QC). This article presents a proof-of-concept experiment, where two AIM systems configured to provide metrics pertinent to QC (QC-system) and human respiratory tract (HRT-system) were evaluated using a hydrofluoroalkane-albuterol pressurized metered dose inhaler. The Andersen eight-stage CI (ACI) served as the benchmark apparatus. The statistical design allowed estimation of precision with each CI configuration. Apart from one source of systematic error affecting extra-fine particle fraction from the HRT-system, no other bias was detected with either abbreviated system. The observed bias was shown to be caused by particle bounce following the displacement of surfactant by the shear force of the airflow diverging above the collection plate of the second impaction stage. A procedure was subsequently developed that eliminated this source of error, as described in the second article of this series (submitted to AAPS PharmSciTech ). Measurements obtained with both abbreviated impactors were very similar in precision to the ACI for all measures of in vitro performance evaluated. Such abbreviated impactors can therefore be substituted for the ACI in certain situations, such as inhaler QC or add-on device testing.
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the abbreviated impactor measurement aim concept part 1 influence of particle bounce and re entrainment evaluation with a dry pressurized metered dose inhaler pmdi based formulation
Aaps Pharmscitech, 2009Co-Authors: Jolyon P Mitchell, Mark Nagel, Valentina Avvakoumova, H Mackay, Rubina AliAbstract:The abbreviated impactor measurement concept is a potential improvement to the labor-intensive Full-Resolution cascade impactor methodology for inhaler aerosol aerodynamic particle size distribution (APSD) measurement by virtue of being simpler and therefore quicker to execute. At the same time, improved measurement precision should be possible by eliminating stages upon which little or no drug mass is collected. Although several designs of abbreviated impactor systems have been developed in recent years, experimental work is lacking to validate the technique with aerosols produced by currently available inhalers. In part 1 of this two-part article that focuses on aerosols produced by pressurized metered dose inhalers (pMDIs), the evaluation of two abbreviated impactor systems (Copley fast screening Andersen impactor and Trudell fast screening Andersen impactor), based on the Full-Resolution eight-stage Andersen nonviable cascade impactor (ACI) operating principle, is reported with a formulation producing dry particles. The purpose was to investigate the potential for non-ideal collection behavior associated with particle bounce in relation to internal losses to surfaces from which particles containing active pharmaceutical ingredient are not normally recovered. Both abbreviated impactors were found to be substantially equivalent to the Full-Resolution ACI in terms of extra-fine and fine particle and coarse mass fractions used as metrics to characterize the APSD of these pMDI-produced aerosols when sampled at 28.3 L/min, provided that precautions are taken to coat collection plates to minimize bounce and entrainment.
Gerald Moore - One of the best experts on this subject based on the ideXlab platform.
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using meris Full Resolution data to monitor coastal waters a case study from himmerfjarden a fjord like bay in the northwestern baltic sea
Remote Sensing of Environment, 2008Co-Authors: Susanne Kratzer, Carsten Brockmann, Gerald MooreAbstract:In this paper we investigate if MERIS Full Resolution (FR) data (300 m) is sufficient to monitor changes in optical constituents in Himmerfjarden, a fjord-like, north– south facing bay of about 30 ...
Svetlana Lyapustina - One of the best experts on this subject based on the ideXlab platform.
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relative precision of inhaler aerodynamic particle size distribution apsd metrics by Full Resolution and abbreviated andersen cascade impactors acis part 2 investigation of bias in extra fine mass fraction with aim hrt impactor
Aaps Pharmscitech, 2010Co-Authors: Jolyon P Mitchell, Mark Nagel, Valentina Avvakoumova, Rubina Ali, Cathy Doyle, David J Christopher, Jorge Quiroz, Helen Strickland, Terrence P Tougas, Svetlana LyapustinaAbstract:The purpose of this study was to resolve an anomalously high measure of extra-fine particle fraction (EPF) determined by the abbreviated cascade impactor possibly relevant for human respiratory tract (AIM-HRT) in the experiment described in Part 1 of this two-part series, in which the relative precision of abbreviated impactors was evaluated in comparison with a Full Resolution Andersen eight-stage cascade impactor (ACI). Evidence that the surface coating used to mitigate particle bounce was laterally displaced by the flow emerging from the jets of the lower stage was apparent upon microscopic examination of the associated collection plate of the AIM-HRT impactor whose cut point size defines EPF. A filter soaked in surfactant was floated on top of this collection plate, and further measurements were made using the same pressurized metered-dose inhaler-based formulation and following the same procedure as in Part 1. Measures of EPF, fine particle, and coarse particle fractions were comparable with those obtained with the ACI, indicating that the cause of the bias had been identified and removed. When working with abbreviated impactors, this precaution is advised whenever there is evidence that surface coating displacement has occurred, a task that can be readily accomplished by microscopic inspection of all collection plates after allowing the impactor to sample ambient air for a few minutes.
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Relative Precision of Inhaler Aerodynamic Particle Size Distribution (APSD) Metrics by Full Resolution and Abbreviated Andersen Cascade Impactors (ACIs): Part 1
AAPS PharmSciTech, 2010Co-Authors: Jolyon P Mitchell, Valentina Avvakoumova, Jorge Quiroz, Helen Strickland, Terrence P Tougas, Mark W. Nagel, Cathy C. Doyle, Rubina S. Ali, J. David Christopher, Svetlana LyapustinaAbstract:The purpose of this study was to compare relative precision of two different abbreviated impactor measurement (AIM) systems and a traditional multi-stage cascade impactor (CI). The experimental design was chosen to provide separate estimates of variability for each impactor type. Full-Resolution CIs are useful for characterizing the aerosol aerodynamic particle size distribution of orally inhaled products during development but are too cumbersome, time-consuming, and resource-intensive for other applications, such as routine quality control (QC). This article presents a proof-of-concept experiment, where two AIM systems configured to provide metrics pertinent to QC (QC-system) and human respiratory tract (HRT-system) were evaluated using a hydrofluoroalkane-albuterol pressurized metered dose inhaler. The Andersen eight-stage CI (ACI) served as the benchmark apparatus. The statistical design allowed estimation of precision with each CI configuration. Apart from one source of systematic error affecting extra-fine particle fraction from the HRT-system, no other bias was detected with either abbreviated system. The observed bias was shown to be caused by particle bounce following the displacement of surfactant by the shear force of the airflow diverging above the collection plate of the second impaction stage. A procedure was subsequently developed that eliminated this source of error, as described in the second article of this series (submitted to AAPS PharmSciTech ). Measurements obtained with both abbreviated impactors were very similar in precision to the ACI for all measures of in vitro performance evaluated. Such abbreviated impactors can therefore be substituted for the ACI in certain situations, such as inhaler QC or add-on device testing.
