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Jolyon P Mitchell - One of the best experts on this subject based on the ideXlab platform.

  • effect of sampling volume on dry powder inhaler dpi emitted aerosol aerodynamic particle size distributions apsds measured by the next generation pharmaceutical Impactor ngi and the andersen eight stage cascade Impactor aci
    Aaps Pharmscitech, 2012
    Co-Authors: Hlack Mohammed, Daryl L Roberts, Steven C Nichols, Mark Copley, Mark Hammond, Jolyon P Mitchell
    Abstract:

    Current pharmacopeial methods for testing dry powder inhalers (DPIs) require that 4.0 L be drawn through the inhaler to quantify aerodynamic particle size distribution of “inhaled” particles. This volume comfortably exceeds the internal dead volume of the Andersen eight-stage cascade Impactor (ACI) and Next Generation pharmaceutical Impactor (NGI) as designated multistage cascade Impactors. Two DPIs, the second (DPI-B) having similar resistance than the first (DPI-A) were used to evaluate ACI and NGI performance at 60 L/min following the methodology described in the European and United States Pharmacopeias. At sampling times ≥2 s (equivalent to volumes ≥2.0 L), both Impactors provided consistent measures of therapeutically important fine particle mass (FPM) from both DPIs, independent of sample duration. At shorter sample times, FPM decreased substantially with the NGI, indicative of incomplete aerosol bolus transfer through the system whose dead space was 2.025 L. However, the ACI provided consistent measures of both variables across the range of sampled volumes evaluated, even when this volume was less than 50% of its internal dead space of 1.155 L. Such behavior may be indicative of maldistribution of the flow profile from the relatively narrow exit of the induction port to the uppermost stage of the Impactor at start-up. An explanation of the ACI anomalous behavior from first principles requires resolution of the rapidly changing unsteady flow and pressure conditions at start up, and is the subject of ongoing research by the European Pharmaceutical Aerosol Group. Meanwhile, these experimental findings are provided to advocate a prudent approach by retaining the current pharmacopeial methodology.

  • effect of sampling volume on dry powder inhaler dpi emitted aerosol aerodynamic particle size distributions apsds measured by the next generation pharmaceutical Impactor ngi and the andersen eight stage cascade Impactor aci
    Aaps Pharmscitech, 2012
    Co-Authors: Hlack Mohammed, Daryl L Roberts, Steven C Nichols, Mark Copley, Mark Hammond, Jolyon P Mitchell
    Abstract:

    Current pharmacopeial methods for testing dry powder inhalers (DPIs) require that 4.0 L be drawn through the inhaler to quantify aerodynamic particle size distribution of “inhaled” particles. This volume comfortably exceeds the internal dead volume of the Andersen eight-stage cascade Impactor (ACI) and Next Generation pharmaceutical Impactor (NGI) as designated multistage cascade Impactors. Two DPIs, the second (DPI-B) having similar resistance than the first (DPI-A) were used to evaluate ACI and NGI performance at 60 L/min following the methodology described in the European and United States Pharmacopeias. At sampling times ≥2 s (equivalent to volumes ≥2.0 L), both Impactors provided consistent measures of therapeutically important fine particle mass (FPM) from both DPIs, independent of sample duration. At shorter sample times, FPM decreased substantially with the NGI, indicative of incomplete aerosol bolus transfer through the system whose dead space was 2.025 L. However, the ACI provided consistent measures of both variables across the range of sampled volumes evaluated, even when this volume was less than 50% of its internal dead space of 1.155 L. Such behavior may be indicative of maldistribution of the flow profile from the relatively narrow exit of the induction port to the uppermost stage of the Impactor at start-up. An explanation of the ACI anomalous behavior from first principles requires resolution of the rapidly changing unsteady flow and pressure conditions at start up, and is the subject of ongoing research by the European Pharmaceutical Aerosol Group. Meanwhile, these experimental findings are provided to advocate a prudent approach by retaining the current pharmacopeial methodology.

  • 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, 2009
    Co-Authors: Jolyon P Mitchell, Mark Nagel, Valentina Avvakoumova, H Mackay, Rubina Ali
    Abstract:

    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.

  • aerodynamic particle size analysis of aerosols from pressurized metered dose inhalers comparison of andersen 8 stage cascade Impactor next generation pharmaceutical Impactor and model 3321 aerodynamic particle sizer aerosol spectrometer
    Aaps Pharmscitech, 2003
    Co-Authors: Jolyon P Mitchell, Mark Nagel, Kimberly J Wiersema, Cathy Doyle
    Abstract:

    The purpose of this research was to compare three different methods for the aerodynamic assessment of (1) chloroflurocarbon (CFC)-fluticasone propionate (Flovent), (2) CFC-sodium cromoglycate (Intal), and (3) hydrofluoroalkane (HFA)-beclomethasone dipropionate (Qvar) delivered by pressurized metered dose inhaler. Particle size distributions were compared determining mass median aerodynamic diameter (MMAD), geometric standard deviation (GSD), and fine particle fraction <4.7 μm aerodynamic diameter (FPF<4.7 μm). Next Generation Pharmaceutical Impactor (NGI)-size distributions for Flovent comprised finer particles than determined by Andersen 8-stage Impactor (ACI) (MMAD=2.0±0.05 μm [NGI]; 2.8±0.07 μm [ACI]); however FPF<4.7 μm by both Impactors was in the narrow range 88% to 93%. Size distribution agreement for Intal was better (MMAD=4.3±0.19 μm (NGI), 4.2±0.13 μm (ACI), with FPF<4.7 μm ranging from 52% to 60%. The Aerodynamic Particle Sizer (APS) undersized aerosols produced with either formulation (MMAD=1.8±0.07 μm and 3.2±0.02 μm for Flovent and Intal, respectively), but values of FPF<4.7 μm from the single-stage Impactor (SSI) located at the inlet to the APS (82.9%±2.1% [Flovent], 46.4%±2.4% [Intal]) were fairly close to corresponding data from the multi-stage Impactors. APS-measured size distributions for Qvar (MMAD=1.0±0.03 μm; FPF<4.7 μm=96.4% ±2.5%), were in fair agreement with both NGI (MMAD=0.9±0.03 μm; FPF<4.7 μm=96.7%±0.7%), and ACI (MMAD=1.2±0.02 μm, FPF<4.7 μm=98%±0.5%), but FPF<4.7 μm from the SSI (67.1%±4.1%) was lower than expected, based on equivalent data obtained by the other techniques. Particle bounce, incomplete evaporation of volatile constituents and the presence of surfactant particles are factors that may be responsible for discrepancies between the techniques.

Hai Wang - One of the best experts on this subject based on the ideXlab platform.

  • Experimental and numerical study on the low-velocity impact behavior of foam-core sandwich panels
    Composite Structures, 2013
    Co-Authors: Jie Wang, Anthony M Waas, Hai Wang
    Abstract:

    Abstract This paper presents the results of an experimental and numerical study on the low-velocity impact behavior of foam-core sandwich panels. Panels with polyurethane foam core and plain weave carbon fabric laminated face-sheets were subjected to low-velocity impact with hemispherical steel Impactors of different diameters at various energy levels. Digital image correlation technique (a non-contact measuring system) was used to measure the real-time displacement and velocity of the Impactor, and the back surface out-of-plane panel deflection time-history. A load sensor was used to record the contact force time-history. Non-destructive inspection and destructive sectioning methods were used to evaluate the internal and external damage on the sandwich panels after impact. The effects of impact variables such as Impactor diameter, impact energy, and sandwich panel configuration parameters, such as face-sheet thickness and foam core thickness on the impact behavior and resulting impact damage states were studied. Based on the generalized Schapery theory, a progressive damage model is developed to describe the nonlinear behavior of plain weave carbon laminates during impact. The foam core was modeled as a crushable foam material. Coupon tests were conducted to determine the input parameters for the progressive damage model and the foam crushing properties. Three-dimensional finite element models were implemented to analyze the impact response incorporating the progressive damage model. Results from the numerical models were found to agree well with experimental observations.

  • Experimental Study on the Low-velocity Impact Behavior of Foam-core Sandwich Panels
    53rd AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference&lt;BR&gt;20th AIAA ASME AHS Adaptive Structures Conference&lt;BR&g, 2012
    Co-Authors: Jie Wang, Anthony M Waas, Hai Wang
    Abstract:

    This paper presents the results of an experimental study on the low-velocity impact behavior of foam-core sandwich panels. Panels with PUR foam core and plain weave carbon fabric laminated face-sheets were subjected to low-velocity impact with hemispherical steel Impactors of dierent diameters at various energy levels. Digital image correlation (DIC) technique (ARAMIS software) was used to measure the real-time displacement and velocity of the Impactor, and the back surface out-of-plane panel deection time-history. A load sensor was used to record the contact force time-history. Non-destructive inspection (NDI) and destructive sectioning methods were used to evaluate the internal and external damage on the sandwich panels after impact. The eects of impact variables such as Impactor diameter, impact energy, and sandwich panel conguration parameters, such as face-sheet thickness and foam core thickness on the impact behavior and resulting impact damage states were studied.

Gary P Martin - One of the best experts on this subject based on the ideXlab platform.

  • aerodynamic deposition of combination dry powder inhaler formulations in vitro a comparison of three Impactors
    International Journal of Pharmaceutics, 2010
    Co-Authors: Mohammed Taki, Christopher Marriott, Xian Ming Zeng, Gary P Martin
    Abstract:

    Abstract Inertial impaction is generally regarded as the ‘gold standard’ for the in vitro assessment of aerodynamic deposition of inhaled formulations. Despite the availability of several Impactors, few studies have compared measurements of aerodynamic deposition using multiple Impactors and none employed a combination formulation. The aerodynamic deposition of the combination dry powder inhaler (DPI) Seretide ® Accuhaler ® , which contains salmeterol xinafoate (SX) and fluticasone propionate (FP), was assessed using the Andersen cascade Impactor (ACI), multi-stage liquid impinger (MSLI) and next generation Impactor (NGI) and the results were compared. Two Seretide products were tested at flow rates of 30 and Q  L min −1 , the latter corresponding to a pressure drop of 4 kPa across the device. Significant differences in the particle size distributions were observed when the same formulation was tested using various Impactors. The ACI was found to be less suitable for DPI testing at flow rates considerably higher than 28.3 L min −1 due to the significant overlap in the cut-off curves of the pre-separator and stage 0. This was not the case with the MSLI but the data derived were limited by the relatively small number of stages. Deposition data determined by the three Impactors were significantly different. The NGI produced good resolution and minimal inter-stage overlap and was regarded as the Impactor of choice for DPI testing.

Jie Wang - One of the best experts on this subject based on the ideXlab platform.

  • Experimental and numerical study on the low-velocity impact behavior of foam-core sandwich panels
    Composite Structures, 2013
    Co-Authors: Jie Wang, Anthony M Waas, Hai Wang
    Abstract:

    Abstract This paper presents the results of an experimental and numerical study on the low-velocity impact behavior of foam-core sandwich panels. Panels with polyurethane foam core and plain weave carbon fabric laminated face-sheets were subjected to low-velocity impact with hemispherical steel Impactors of different diameters at various energy levels. Digital image correlation technique (a non-contact measuring system) was used to measure the real-time displacement and velocity of the Impactor, and the back surface out-of-plane panel deflection time-history. A load sensor was used to record the contact force time-history. Non-destructive inspection and destructive sectioning methods were used to evaluate the internal and external damage on the sandwich panels after impact. The effects of impact variables such as Impactor diameter, impact energy, and sandwich panel configuration parameters, such as face-sheet thickness and foam core thickness on the impact behavior and resulting impact damage states were studied. Based on the generalized Schapery theory, a progressive damage model is developed to describe the nonlinear behavior of plain weave carbon laminates during impact. The foam core was modeled as a crushable foam material. Coupon tests were conducted to determine the input parameters for the progressive damage model and the foam crushing properties. Three-dimensional finite element models were implemented to analyze the impact response incorporating the progressive damage model. Results from the numerical models were found to agree well with experimental observations.

  • Experimental Study on the Low-velocity Impact Behavior of Foam-core Sandwich Panels
    53rd AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference&lt;BR&gt;20th AIAA ASME AHS Adaptive Structures Conference&lt;BR&g, 2012
    Co-Authors: Jie Wang, Anthony M Waas, Hai Wang
    Abstract:

    This paper presents the results of an experimental study on the low-velocity impact behavior of foam-core sandwich panels. Panels with PUR foam core and plain weave carbon fabric laminated face-sheets were subjected to low-velocity impact with hemispherical steel Impactors of dierent diameters at various energy levels. Digital image correlation (DIC) technique (ARAMIS software) was used to measure the real-time displacement and velocity of the Impactor, and the back surface out-of-plane panel deection time-history. A load sensor was used to record the contact force time-history. Non-destructive inspection (NDI) and destructive sectioning methods were used to evaluate the internal and external damage on the sandwich panels after impact. The eects of impact variables such as Impactor diameter, impact energy, and sandwich panel conguration parameters, such as face-sheet thickness and foam core thickness on the impact behavior and resulting impact damage states were studied.

Sean N. Raymond - One of the best experts on this subject based on the ideXlab platform.

  • Late Veneer collisions and their impact on the evolution of Venus (PS Division Outstanding ECS Award Lecture)
    2017
    Co-Authors: Cedric Gillmann, Gregor Golabek, Paul Tackley, Sean N. Raymond
    Abstract:

    During the end of the accretion, the so-called Late Veneer phase, while the bulk of the mass of terrestrial planets is already in place, a substantial number of large collisions can still occur. Those impacts are thought to be responsible for the repartition of the Highly Siderophile Elements. They are also susceptible to have a strong effect on volatile repartition and mantle convection. We study how Late Veneer impacts modify the evolution of Venus and its atmosphere, using a coupled numerical simulation. We focus on volatile exchanges and their effects on surface conditions. Mantle dynamics, volcanism and degassing processes lead to an input of gases in the atmosphere and are modeled using the StagYY mantle convection code. Volatile losses are estimated through atmospheric escape modeling. It involves two different aspects: hydrodynamic escape (0-500 Myr) and non-thermal escape. Hydrodynamic escape is massive but occurs only when the solar energy input is strong. Post 4 Ga escape from non-thermal processes is comparatively low but long-lived. The resulting state of the atmosphere is used to the calculate greenhouse effect and surface temperature, through a one-dimensional gray radiative-convective model. Large impacts are capable of contributing to (i) atmospheric escape, (ii) volatile replenishment and (iii) energy transfer to the mantle. We test various Impactor compositions, impact parameters (velocity, location, size, and timing) and eroding power. Scenarios we tested are adapted from numerical stochastic simulations (Raymond et al., 2013). Impactor sizes are dominated by large bodies (R>500 km). Erosion of the atmosphere by a few large impacts appears limited. Swarms of smaller more mass-effective Impactors seem required for this effect to be significant. Large Impactors have two main effects on the atmosphere. They can (i) create a large input of volatile from the melting they cause during the impact and through the volatiles they carry. This leads to an increase in atmosphere density and surface temperatures. However, early impacts can also (ii) deplete the mantle of Venus and (assuming strong early escape) ultimately remove volatiles from the system, leading to lower late degassing and lower surface temperatures. The competition between those effects depends on the time of the impact, which directly governs the strength of atmospheric losses.

  • a primordial origin for the compositional similarity between the earth and the moon
    Nature, 2015
    Co-Authors: Alessandra Mastrobuonobattisti, Hagai B., Perets, Sean N. Raymond
    Abstract:

    The Moon is thought to have formed mainly from a giant Impactor striking the Earth but it has seemed odd that the Earth and its Impactor (and hence the Moon) had such similar compositions; here simulations of planetary accretion show that although the different planets have distinct compositions, the composition of each giant Impactor is indeed often very similar to that of the planet it strikes. The Moon is thought to have formed mainly from material within a giant Impactor that struck the proto-Earth, so it seems odd that the compositions of the Moon and Earth are so similar, given the differing composition of other Solar System bodies. Alessandra Mastrobuono-Battisti et al. track the feeding zones of growing planets in a suite of computational simulations of planetary accretion and find that different planets formed in the same simulation have distinct compositions, but the compositions of giant Impactors are more similar to the planets they impact. A significant fraction of planet–Impactor pairs have virtually identical compositions. The authors conclude that the similarity in composition between the Earth and Moon could be a natural consequence of a late giant impact. Most of the properties of the Earth–Moon system can be explained by a collision between a planetary embryo (giant Impactor) and the growing Earth late in the accretion process1,2,3. Simulations show that most of the material that eventually aggregates to form the Moon originates from the Impactor1,4,5. However, analysis of the terrestrial and lunar isotopic compositions show them to be highly similar6,7,8,9,10,11. In contrast, the compositions of other Solar System bodies are significantly different from those of the Earth and Moon12,13,14, suggesting that different Solar System bodies have distinct compositions. This challenges the giant impact scenario, because the Moon-forming Impactor must then also be thought to have a composition different from that of the proto-Earth. Here we track the feeding zones of growing planets in a suite of simulations of planetary accretion15, to measure the composition of Moon-forming Impactors. We find that different planets formed in the same simulation have distinct compositions, but the compositions of giant Impactors are statistically more similar to the planets they impact. A large fraction of planet–Impactor pairs have almost identical compositions. Thus, the similarity in composition between the Earth and Moon could be a natural consequence of a late giant impact.

  • A primordial origin for the composition similarity between the Earth and the Moon
    Nature, 2015
    Co-Authors: Alessandra, Mastrobuono-battisti, Hagai B., Perets, Sean N. Raymond
    Abstract:

    Most of the properties of the Earth-Moon system can be explained by a collision between a planetary embryo and the growing Earth late in the accretion process. Simulations show that most of the material that eventually aggregates to form the Moon originates from the Impactor. However, analysis of the terrestrial and lunar isotopic composition show them to be highly similar. In contrast, the compositions of other solar system bodies are significantly different than the Earth and Moon. This poses a major challenge to the giant impact scenario since the Moon-forming Impactor is then thought to also have differed in composition from the proto-Earth. Here we track the feeding zones of growing planets in a suite of simulations of planetary accretion, in order to measure the composition of Moon-forming Impactors. We find that different planets formed in the same simulation have distinct compositions, but the compositions of giant Impactors are systematically more similar to the planets they impact. A significant fraction of planet-Impactor pairs have virtually identical compositions. Thus, the similarity in composition between the Earth and Moon could be a natural consequence of a late giant impact.